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* [PATCH 00/13] VFS: Filesystem information [ver #19]
@ 2020-03-18 15:08 David Howells
  2020-03-18 15:08 ` [PATCH 01/13] fsinfo: Add fsinfo() syscall to query filesystem " David Howells
                   ` (14 more replies)
  0 siblings, 15 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:08 UTC (permalink / raw)
  To: torvalds, viro
  Cc: linux-nfs, Andreas Dilger, Anna Schumaker, Theodore Ts'o,
	linux-api, linux-ext4, Trond Myklebust, dhowells, raven,
	mszeredi, christian, jannh, darrick.wong, kzak, jlayton,
	linux-api, linux-fsdevel, linux-security-module, linux-kernel


Here's a set of patches that adds a system call, fsinfo(), that allows
information about the VFS, mount topology, superblock and files to be
retrieved.

The patchset is based on top of the notifications patchset and allows event
counters implemented in the latter to be retrieved to allow overruns to be
efficiently managed.

Included are a couple of sample programs plus limited example code for NFS
and Ext4.  The example code is not intended to go upstream as-is.


=======
THE WHY
=======

Why do we want this?

Using /proc/mounts (or similar) has problems:

 (1) Reading from it holds a global lock (namespace_sem) that prevents
     mounting and unmounting.  Lots of data is encoded and mangled into
     text whilst the lock is held, including superblock option strings and
     mount point paths.  This causes performance problems when there are a
     lot of mount objects in a system.

 (2) Even though namespace_sem is held during a read, reading the whole
     file isn't necessarily atomic with respect to mount-type operations.
     If a read isn't satisfied in one go, then it may return to userspace
     briefly and then continue reading some way into the file.  But changes
     can occur in the interval that may then go unseen.

 (3) Determining what has changed means parsing and comparing consecutive
     outputs of /proc/mounts.

 (4) Querying a specific mount or superblock means searching through
     /proc/mounts and searching by path or mount ID - but we might have an
     fd we want to query.

 (5) Mount topology is not explicit.  One must derive it manually by
     comparing entries.

 (6) Whilst you can poll() it for events, it only tells you that something
     changed in the namespace, not what or whether you can even see the
     change.

To fix the notification issues, the preceding notifications patchset added
mount watch notifications whereby you can watch for notifications in a
specific mount subtree.  The notification messages include the ID(s) of the
affected mounts.

To support notifications, however, we need to be able to handle overruns in
the notification queue.  I added a number of event counters to struct
super_block and struct mount to allow you to pin down the changes, but
there needs to be a way to retrieve them.  Exposing them through /proc
would require adding yet another /proc/mounts-type file.  We could add
per-mount directories full of attributes in sysfs, but that has issues also
(see below).

Adding an extensible system call interface for retrieving filesystem
information also allows other things to be exposed:

 (1) Jeff Layton's error handling changes need a way to allow error event
     information to be retrieved.

 (2) Bits in masks returned by things like statx() and FS_IOC_GETFLAGS are
     actually 3-state { Set, Unset, Not supported }.  It could be useful to
     provide a way to expose information like this[*].

 (3) Limits of the numerical metadata values in a filesystem[*].

 (4) Filesystem capability information[*].  Filesystems don't all have the
     same capabilities, and even different instances may have different
     capabilities, particularly with network filesystems where the set of
     may be server-dependent.  Capabilities might even vary at file
     granularity - though possibly such information should be conveyed
     through statx() instead.

 (5) ID mapping/shifting tables in use for a superblock.

 (6) Filesystem-specific information.  I need something for AFS so that I
     can do pioctl()-emulation, thereby allowing me to implement certain of
     the AFS command line utilities that query state of a particular file.
     This could also have application for other filesystems, such as NFS,
     CIFS and ext4.

 [*] In a lot of cases these are probably fixed and can be memcpy'd from
     static data.

There's a further consideration: I want to make it possible to have
fsconfig(fd, FSCONFIG_CMD_CREATE) be intercepted by a container manager
such that the manager can supervise a mount attempted inside the container.
The manager would be given an fd pointing to the fs_context struct and
would then need some way to query it (fsinfo()) and modify it (fsconfig()).
This could also be used to arbitrate user-requested mounts when containers
are not in play.


============================
WHY NOT USE PROCFS OR SYSFS?
============================

Why is it better to go with a new system call rather than adding more magic
stuff to /proc or /sysfs for each superblock object and each mount object?

 (1) It can be targetted.  It makes it easy to query directly by path.
     procfs and sysfs cannot do this easily.

 (2) It's more efficient as we can return specific binary data rather than
     making huge text dumps.  Granted, sysfs and procfs could present the
     same data, though as lots of little files which have to be
     individually opened, read, closed and parsed.

 (3) We wouldn't have the overhead of open and close (even adding a
     self-contained readfile() syscall has to do that internally) and the
     RCU destruction of the file struct(s).

 (4) Opening a file in procfs or sysfs has a pathwalk overhead for each
     file accessed.  We can use an integer attribute ID instead (yes, this
     is similar to ioctl) - but could also use a string ID if that is
     preferred.

 (5) Can easily query cross-namespace if, say, a container manager process
     is given an fs_context that hasn't yet been mounted into a namespace -
     or hasn't even been fully created yet.

 (6) Don't have to create/delete a bunch of sysfs/procfs nodes each time a
     mount happens or is removed - and since systemd makes much use of
     mount namespaces and mount propagation, this will create a lot of
     nodes.

The argument for doing this through procfs/sysfs/somemagicfs is that
someone using a shell can just query the magic files using ordinary text
tools, such as cat - and that has merit - but it doesn't solve the
query-by-pathname problem.

The suggested way around the query-by-pathname problem is to open the
target file O_PATH and then look in a magic directory under procfs
corresponding to the fd number to see a set of attribute files[*] laid out.
Bash, however, can't open by O_PATH or O_NOFOLLOW as things stand...

[*] Or possibly symlinks to files under a per-mount or per-sb directory in
    sysfs.


================
DESIGN DECISIONS
================

 (1) Information is partitioned into sets of attributes.

 (2) Attribute IDs are integers as they're fast to compare.

 (3) Attribute values are typed (struct, list of structs, string, opaque
     blob).  They type is fixed for a particular attribute.

 (4) For structure types, the length is also a version.  New fields can be
     tacked onto the end.

 (5) When copying a versioned struct to userspace, the core handles a
     version mismatch by truncating or zero-padding the data as necessary.
     None of this is seen by the filesystem.

 (6) The core handles all the buffering and buffer resizing.

 (7) The filesystem never gets any access to the userspace parameter buffer
     or result buffer.

 (8) "Meta" attributes can describe other attributes.


========
OVERVIEW
========

fsinfo() is a system call that allows information about the filesystem at a
particular path point to be queried as a set of attributes.

Attribute values are of four basic types:

 (1) Structure with version-dependent length (the length is the version).

 (2) Variable-length string.

 (3) List of structures (all the same length).

 (4) Opaque blob.

Attributes can have multiple values either as a sequence of values or a
sequence-of-sequences of values and all the values of a particular
attribute must be of the same type.  Values can be up to INT_MAX size,
subject to memory availability.

Note that the values of an attribute *are* allowed to vary between dentries
within a single superblock, depending on the specific dentry that you're
looking at, but the values still have to be of the type for that attribute.

I've tried to make the interface as light as possible, so integer attribute
ID rather than string and the core does all the buffer allocation and
expansion and all the extensibility support work rather than leaving that
to the filesystems.  This means that userspace pointers are not exposed to
the filesystem.


fsinfo() allows a variety of information to be retrieved about a filesystem
and the mount topology:

 (1) General superblock attributes:

     - Filesystem identifiers (UUID, volume label, device numbers, ...)
     - The limits on a filesystem's capabilities
     - Information on supported statx fields and attributes and IOC flags.
     - A variety single-bit flags indicating supported capabilities.
     - Timestamp resolution and range.
     - The amount of space/free space in a filesystem (as statfs()).
     - Superblock notification counter.

 (2) Filesystem-specific superblock attributes:

     - Superblock-level timestamps.
     - Cell name, workgroup or other netfs grouping concept.
     - Server names and addresses.

 (3) VFS information:

     - Mount topology information.
     - Mount attributes.
     - Mount notification counter.
     - Mount point path.

 (4) Information about what the fsinfo() syscall itself supports, including
     the type and struct size of attributes.

The system is extensible:

 (1) New attributes can be added.  There is no requirement that a
     filesystem implement every attribute.  A helper function is provided
     to scan a list of attributes and a filesystem can have multiple such
     lists.

 (2) Version length-dependent structure attributes can be made larger and
     have additional information tacked on the end, provided it keeps the
     layout of the existing fields.  If an older process asks for a shorter
     structure, it will only be given the bits it asks for.  If a newer
     process asks for a longer structure on an older kernel, the extra
     space will be set to 0.  In all cases, the size of the data actually
     available is returned.

     In essence, the size of a structure is that structure's version: a
     smaller size is an earlier version and a later version includes
     everything that the earlier version did.

 (3) New single-bit capability flags can be added.  This is a structure-typed
     attribute and, as such, (2) applies.  Any bits you wanted but the kernel
     doesn't support are automatically set to 0.

fsinfo() may be called like the following, for example:

	struct fsinfo_params params = {
		.at_flags	= AT_SYMLINK_NOFOLLOW,
		.flags		= FSINFO_FLAGS_QUERY_PATH,
		.request	= FSINFO_ATTR_AFS_SERVER_ADDRESSES,
		.Nth		= 2,
	};
	struct fsinfo_server_address address;
	len = fsinfo(AT_FDCWD, "/afs/grand.central.org/doc", &params,
		     &address, sizeof(address));

The above example would query an AFS filesystem to retrieve the address
list for the 3rd server, and:

	struct fsinfo_params params = {
		.at_flags	= AT_SYMLINK_NOFOLLOW,
		.flags		= FSINFO_FLAGS_QUERY_PATH,
		.request	= FSINFO_ATTR_NFS_SERVER_NAME;
	};
	char server_name[256];
	len = fsinfo(AT_FDCWD, "/home/dhowells/", &params,
		     &server_name, sizeof(server_name));

would retrieve the name of the NFS server as a string.

In future, I want to make fsinfo() capable of querying a context created by
fsopen() or fspick(), e.g.:

	fd = fsopen("ext4", 0);
	struct fsinfo_params params = {
		.flags		= FSINFO_FLAGS_QUERY_FSCONTEXT,
		.request	= FSINFO_ATTR_CONFIGURATION;
	};
	char buffer[65536];
	fsinfo(fd, NULL, &params, &buffer, sizeof(buffer));

even if that context doesn't currently have a superblock attached.

The patches can be found here also:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git

on branch:

	fsinfo-core


===================
SIGNIFICANT CHANGES
===================

 ver #19:

 (*) Split FSINFO_ATTR_MOUNT_TOPOLOGY from FSINFO_ATTR_MOUNT_INFO.  The
     latter requires no locking as it looks no further than the mount
     object it's dealing with.  The topology attribute, however, has to
     take the namespace lock.  That said, the info attribute includes a
     counter that indicates how many times a mount object's position in the
     topology has changed.

 (*) A bit of patch rearrangement to put the mount topology-exposing
     attributes into one patch.

 (*) Pass both AT_* and RESOLVE_* flags to fsinfo() as suggested by Linus,
     rather than adding missing RESOLVE_* flags.

 ver #18:

 (*) Moved the mount and superblock notification patches into a different
     branch.

 (*) Made superblock configuration (->show_opts), bindmount path
     (->show_path) and filesystem statistics (->show_stats) available as
     the CONFIGURATION, MOUNT_PATH and FS_STATISTICS attributes.

 (*) Made mountpoint device name available, filtered through the superblock
     (->show_devname), as the SOURCE attribute.

 (*) Made the mountpoint available as a full path as well as a relative
     one.

 (*) Added more event counters to MOUNT_INFO, including a subtree
     notification counter, to make it easier to clean up after a
     notification overrun.

 (*) Made the event counter value returned by MOUNT_CHILDREN the sum of the
     five event counters.

 (*) Added a mount uniquifier and added that to the MOUNT_CHILDREN entries
     also so that mount ID reuse can be detected.

 (*) Merged the SB_NOTIFICATION attribute into the MOUNT_INFO attribute to
     avoid duplicate information.

 (*) Switched to using the RESOLVE_* flags rather than AT_* flags for
     pathwalk control.  Added more RESOLVE_* flags.

 (*) Used a lock instead of RCU to enumerate children for the
     MOUNT_CHILDREN attribute for safety.  This is probably worth
     revisiting at a later date, however.


 ver #17:

 (*) Applied comments from Jann Horn, Darrick Wong and Christian Brauner.

 (*) Rearranged the order in which fsinfo() does things so that the
     superblock operations table can have a function pointer rather than a
     table pointer.  The ->fsinfo() op is now called at least twice, once
     to determine the size of buffer needed and then to retrieve the data.
     If the retrieval step indicates yet more space is needed, the buffer
     will be expanded and that step repeated.

 (*) Merge the element size into the size in the fsinfo_attribute def and
     don't set size for strings or opaques.  Let a helper work that out.
     This means that strings can actually get larger then 4K.

 (*) A helper is provided to scan a list of attributes and call the
     appropriate get function.  This can be called from a filesystem's
     ->fsinfo() method multiple times.  It also handles attribute
     enumeration and info querying.

 (*) Rearranged the patches to put all the notification patches first.
     This allowed some of the bits to be squashed together.  At some point,
     I'll move the notification patches into a different branch.

 ver #16:

 (*) Split the features bits out of the fsinfo() core into their own patch
     and got rid of the name encoding attributes.

 (*) Renamed the 'array' type to 'list' and made AFS use it for returning
     server address lists.

 (*) Changed the ->fsinfo() method into an ->fsinfo_attributes[] table,
     where each attribute has a ->get() method to deal with it.  These
     tables can then be returned with an fsinfo meta attribute.

 (*) Dropped the fscontext query and parameter/description retrieval
     attributes for now.

 (*) Picked the mount topology attributes into this branch.

 (*) Picked the mount notifications into this branch and rebased on top of
     notifications-pipe-core.

 (*) Picked the superblock notifications into this branch.

 (*) Add sample code for Ext4 and NFS.

David
---
David Howells (13):
      fsinfo: Add fsinfo() syscall to query filesystem information
      fsinfo: Provide a bitmap of supported features
      fsinfo: Allow retrieval of superblock devname, options and stats
      fsinfo: Allow fsinfo() to look up a mount object by ID
      fsinfo: Add a uniquifier ID to struct mount
      fsinfo: Allow mount information to be queried
      fsinfo: Allow mount topology and propagation info to be retrieved
      fsinfo: Provide notification overrun handling support
      fsinfo: sample: Mount listing program
      fsinfo: Add API documentation
      fsinfo: Add support for AFS
      fsinfo: Example support for Ext4
      fsinfo: Example support for NFS


 Documentation/filesystems/fsinfo.rst        |  574 +++++++++++++++++
 arch/alpha/kernel/syscalls/syscall.tbl      |    1 
 arch/arm/tools/syscall.tbl                  |    1 
 arch/arm64/include/asm/unistd.h             |    2 
 arch/arm64/include/asm/unistd32.h           |    2 
 arch/ia64/kernel/syscalls/syscall.tbl       |    1 
 arch/m68k/kernel/syscalls/syscall.tbl       |    1 
 arch/microblaze/kernel/syscalls/syscall.tbl |    1 
 arch/mips/kernel/syscalls/syscall_n32.tbl   |    1 
 arch/mips/kernel/syscalls/syscall_n64.tbl   |    1 
 arch/mips/kernel/syscalls/syscall_o32.tbl   |    1 
 arch/parisc/kernel/syscalls/syscall.tbl     |    1 
 arch/powerpc/kernel/syscalls/syscall.tbl    |    1 
 arch/s390/kernel/syscalls/syscall.tbl       |    1 
 arch/sh/kernel/syscalls/syscall.tbl         |    1 
 arch/sparc/kernel/syscalls/syscall.tbl      |    1 
 arch/x86/entry/syscalls/syscall_32.tbl      |    1 
 arch/x86/entry/syscalls/syscall_64.tbl      |    1 
 arch/xtensa/kernel/syscalls/syscall.tbl     |    1 
 fs/Kconfig                                  |    7 
 fs/Makefile                                 |    1 
 fs/afs/internal.h                           |    1 
 fs/afs/super.c                              |  218 +++++++
 fs/d_path.c                                 |    2 
 fs/ext4/Makefile                            |    1 
 fs/ext4/ext4.h                              |    6 
 fs/ext4/fsinfo.c                            |   45 +
 fs/ext4/super.c                             |    3 
 fs/fsinfo.c                                 |  725 ++++++++++++++++++++++
 fs/internal.h                               |   14 
 fs/mount.h                                  |    3 
 fs/mount_notify.c                           |    2 
 fs/namespace.c                              |  389 ++++++++++++
 fs/nfs/Makefile                             |    1 
 fs/nfs/fsinfo.c                             |  230 +++++++
 fs/nfs/internal.h                           |    6 
 fs/nfs/nfs4super.c                          |    3 
 fs/nfs/super.c                              |    3 
 include/linux/fs.h                          |    4 
 include/linux/fsinfo.h                      |  111 +++
 include/linux/syscalls.h                    |    4 
 include/uapi/asm-generic/unistd.h           |    4 
 include/uapi/linux/fsinfo.h                 |  371 +++++++++++
 include/uapi/linux/mount.h                  |   10 
 include/uapi/linux/windows.h                |   35 +
 kernel/sys_ni.c                             |    1 
 samples/vfs/Makefile                        |    7 
 samples/vfs/test-fsinfo.c                   |  891 +++++++++++++++++++++++++++
 samples/vfs/test-mntinfo.c                  |  279 ++++++++
 49 files changed, 3962 insertions(+), 9 deletions(-)
 create mode 100644 Documentation/filesystems/fsinfo.rst
 create mode 100644 fs/ext4/fsinfo.c
 create mode 100644 fs/fsinfo.c
 create mode 100644 fs/nfs/fsinfo.c
 create mode 100644 include/linux/fsinfo.h
 create mode 100644 include/uapi/linux/fsinfo.h
 create mode 100644 include/uapi/linux/windows.h
 create mode 100644 samples/vfs/test-fsinfo.c
 create mode 100644 samples/vfs/test-mntinfo.c



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 01/13] fsinfo: Add fsinfo() syscall to query filesystem information [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
@ 2020-03-18 15:08 ` David Howells
  2020-03-18 15:08 ` [PATCH 02/13] fsinfo: Provide a bitmap of supported features " David Howells
                   ` (13 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:08 UTC (permalink / raw)
  To: torvalds, viro
  Cc: linux-api, dhowells, raven, mszeredi, christian, jannh,
	darrick.wong, kzak, jlayton, linux-api, linux-fsdevel,
	linux-security-module, linux-kernel

Add a system call to allow filesystem information to be queried.  A request
value can be given to indicate the desired attribute.  Support is provided
for enumerating multi-value attributes.

===============
NEW SYSTEM CALL
===============

The new system call looks like:

	int ret = fsinfo(int dfd,
			 const char *pathname,
			 const struct fsinfo_params *params,
			 size_t params_size,
			 void *result_buffer,
			 size_t result_buf_size);

The params parameter optionally points to a block of parameters:

	struct fsinfo_params {
		__u64	resolve_flags;
		__u32	at_flags;
		__u32	flags;
		__u32	request;
		__u32	Nth;
		__u32	Mth;
	};

If params is NULL, the default is that params->request is
FSINFO_ATTR_STATFS and all the other fields are 0.  params_size indicates
the size of the parameter struct.  If the parameter block is short compared
to what the kernel expects, the missing length will be set to 0; if the
parameter block is longer, an error will be given if the excess is not all
zeros.

The object to be queried is specified as follows - part param->flags
indicates the type of reference:

 (1) FSINFO_FLAGS_QUERY_PATH - dfd, pathname and at_flags indicate a
     filesystem object to query.

     There is no separate system call providing an analogue of lstat() -
     AT_SYMLINK_NOFOLLOW should be set in at_flags instead.
     AT_NO_AUTOMOUNT can also be used to an allow automount point to be
     queried without triggering it.

     RESOLVE_* flags can also be set in resolve_flags to further restrict
     the patchwalk.

 (2) FSINFO_FLAGS_QUERY_FD - dfd indicates a file descriptor pointing to
     the filesystem object to query.  pathname should be NULL.

 (3) FSINFO_FLAGS_QUERY_MOUNT - pathname indicates the numeric ID of the
     mountpoint to query as a string.  dfd is used to constrain which
     mounts can be accessed.  If dfd is AT_FDCWD, the mount must be within
     the subtree rooted at chroot, otherwise the mount must be within the
     subtree rooted at the directory specified by dfd.

 (4) In the future FSINFO_FLAGS_QUERY_FSCONTEXT will be added - dfd will
     indicate a context handle fd obtained from fsopen() or fspick(),
     allowing that to be queried before the target superblock is attached
     to the filesystem or even created.

params->request indicates the attribute/attributes to be queried.  This can
be one of:

	FSINFO_ATTR_STATFS		- statfs-style info
	FSINFO_ATTR_IDS			- Filesystem IDs
	FSINFO_ATTR_LIMITS		- Filesystem limits
	FSINFO_ATTR_SUPPORTS		- Support for statx, ioctl, etc.
	FSINFO_ATTR_TIMESTAMP_INFO	- Inode timestamp info
	FSINFO_ATTR_VOLUME_ID		- Volume ID (string)
	FSINFO_ATTR_VOLUME_UUID		- Volume UUID
	FSINFO_ATTR_VOLUME_NAME		- Volume name (string)
	FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO - Information about attr Nth
	FSINFO_ATTR_FSINFO_ATTRIBUTES	- List of supported attrs

Some attributes (such as the servers backing a network filesystem) can have
multiple values.  These can be enumerated by setting params->Nth and
params->Mth to 0, 1, ... until ENODATA is returned.

result_buffer and result_buf_size point to the reply buffer.  The buffer is
filled up to the specified size, even if this means truncating the reply.
The size of the full reply is returned, irrespective of the amount data
that was copied.  In future versions, this will allow extra fields to be
tacked on to the end of the reply, but anyone not expecting them will only
get the subset they're expecting.  If either buffer of result_buf_size are
0, no copy will take place and the data size will be returned.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-api@vger.kernel.org
---

 arch/alpha/kernel/syscalls/syscall.tbl      |    1 
 arch/arm/tools/syscall.tbl                  |    1 
 arch/arm64/include/asm/unistd.h             |    2 
 arch/arm64/include/asm/unistd32.h           |    2 
 arch/ia64/kernel/syscalls/syscall.tbl       |    1 
 arch/m68k/kernel/syscalls/syscall.tbl       |    1 
 arch/microblaze/kernel/syscalls/syscall.tbl |    1 
 arch/mips/kernel/syscalls/syscall_n32.tbl   |    1 
 arch/mips/kernel/syscalls/syscall_n64.tbl   |    1 
 arch/mips/kernel/syscalls/syscall_o32.tbl   |    1 
 arch/parisc/kernel/syscalls/syscall.tbl     |    1 
 arch/powerpc/kernel/syscalls/syscall.tbl    |    1 
 arch/s390/kernel/syscalls/syscall.tbl       |    1 
 arch/sh/kernel/syscalls/syscall.tbl         |    1 
 arch/sparc/kernel/syscalls/syscall.tbl      |    1 
 arch/x86/entry/syscalls/syscall_32.tbl      |    1 
 arch/x86/entry/syscalls/syscall_64.tbl      |    1 
 arch/xtensa/kernel/syscalls/syscall.tbl     |    1 
 fs/Kconfig                                  |    7 
 fs/Makefile                                 |    1 
 fs/fsinfo.c                                 |  586 +++++++++++++++++++++++++
 include/linux/fs.h                          |    4 
 include/linux/fsinfo.h                      |   73 +++
 include/linux/syscalls.h                    |    4 
 include/uapi/asm-generic/unistd.h           |    4 
 include/uapi/linux/fsinfo.h                 |  187 ++++++++
 kernel/sys_ni.c                             |    1 
 samples/vfs/Makefile                        |    5 
 samples/vfs/test-fsinfo.c                   |  633 +++++++++++++++++++++++++++
 29 files changed, 1523 insertions(+), 2 deletions(-)
 create mode 100644 fs/fsinfo.c
 create mode 100644 include/linux/fsinfo.h
 create mode 100644 include/uapi/linux/fsinfo.h
 create mode 100644 samples/vfs/test-fsinfo.c

diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
index 7c0115af9010..4d0b07dde12d 100644
--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -479,3 +479,4 @@
 548	common	pidfd_getfd			sys_pidfd_getfd
 549	common	watch_mount			sys_watch_mount
 550	common	watch_sb			sys_watch_sb
+551	common	fsinfo				sys_fsinfo
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index f256f009a89f..fdda8382b420 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -453,3 +453,4 @@
 438	common	pidfd_getfd			sys_pidfd_getfd
 439	common	watch_mount			sys_watch_mount
 440	common	watch_sb			sys_watch_sb
+441	common	fsinfo				sys_fsinfo
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index bc0f923e0e04..388eeb71cff0 100644
--- a/arch/arm64/include/asm/unistd.h
+++ b/arch/arm64/include/asm/unistd.h
@@ -38,7 +38,7 @@
 #define __ARM_NR_compat_set_tls		(__ARM_NR_COMPAT_BASE + 5)
 #define __ARM_NR_COMPAT_END		(__ARM_NR_COMPAT_BASE + 0x800)
 
-#define __NR_compat_syscalls		441
+#define __NR_compat_syscalls		442
 #endif
 
 #define __ARCH_WANT_SYS_CLONE
diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index 5ba3dae4859b..9ffde1fd2124 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -887,6 +887,8 @@ __SYSCALL(__NR_pidfd_getfd, sys_pidfd_getfd)
 __SYSCALL(__NR_watch_mount, sys_watch_mount)
 #define __NR_watch_sb 440
 __SYSCALL(__NR_watch_sb, sys_watch_sb)
+#define __NR_fsinfo 441
+__SYSCALL(__NR_fsinfo, sys_fsinfo)
 
 /*
  * Please add new compat syscalls above this comment and update
diff --git a/arch/ia64/kernel/syscalls/syscall.tbl b/arch/ia64/kernel/syscalls/syscall.tbl
index a4dafc659647..2316e60e031a 100644
--- a/arch/ia64/kernel/syscalls/syscall.tbl
+++ b/arch/ia64/kernel/syscalls/syscall.tbl
@@ -360,3 +360,4 @@
 438	common	pidfd_getfd			sys_pidfd_getfd
 439	common	watch_mount			sys_watch_mount
 440	common	watch_sb			sys_watch_sb
+441	common	fsinfo				sys_fsinfo
diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl
index 893fb4151547..efc2723ca91f 100644
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -439,3 +439,4 @@
 438	common	pidfd_getfd			sys_pidfd_getfd
 439	common	watch_mount			sys_watch_mount
 440	common	watch_sb			sys_watch_sb
+441	common	fsinfo				sys_fsinfo
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index 54aaf0d40c64..745c0f462fce 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -445,3 +445,4 @@
 438	common	pidfd_getfd			sys_pidfd_getfd
 439	common	watch_mount			sys_watch_mount
 440	common	watch_sb			sys_watch_sb
+441	common	fsinfo				sys_fsinfo
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index fd34dd0efed0..499f83562a8c 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -378,3 +378,4 @@
 438	n32	pidfd_getfd			sys_pidfd_getfd
 439	n32	watch_mount			sys_watch_mount
 440	n32	watch_sb			sys_watch_sb
+441	n32	fsinfo				sys_fsinfo
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index db0f4c0a0a0b..b3188bc3ab3c 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -354,3 +354,4 @@
 438	n64	pidfd_getfd			sys_pidfd_getfd
 439	n64	watch_mount			sys_watch_mount
 440	n64	watch_sb			sys_watch_sb
+441	n64	fsinfo				sys_fsinfo
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index ce2e1326de8f..1a3e8ed5e538 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -427,3 +427,4 @@
 438	o32	pidfd_getfd			sys_pidfd_getfd
 439	o32	watch_mount			sys_watch_mount
 440	o32	watch_sb			sys_watch_sb
+441	o32	fsinfo				sys_fsinfo
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index 6e4a7c08b64b..2572c215d861 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -437,3 +437,4 @@
 438	common	pidfd_getfd			sys_pidfd_getfd
 439	common	watch_mount			sys_watch_mount
 440	common	watch_sb			sys_watch_sb
+441	common	fsinfo				sys_fsinfo
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 08943f3b8206..39d7ac7e918c 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -521,3 +521,4 @@
 438	common	pidfd_getfd			sys_pidfd_getfd
 439	common	watch_mount			sys_watch_mount
 440	common	watch_sb			sys_watch_sb
+441	common	fsinfo				sys_fsinfo
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index b3b8529d2b74..ae4cefd3dd1b 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -442,3 +442,4 @@
 438  common	pidfd_getfd		sys_pidfd_getfd			sys_pidfd_getfd
 439	common	watch_mount		sys_watch_mount			sys_watch_mount
 440	common	watch_sb		sys_watch_sb			sys_watch_sb
+441  common	fsinfo			sys_fsinfo			sys_fsinfo
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index 89307a20657c..05945b9aee4b 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -442,3 +442,4 @@
 438	common	pidfd_getfd			sys_pidfd_getfd
 439	common	watch_mount			sys_watch_mount
 440	common	watch_sb			sys_watch_sb
+441	common	fsinfo				sys_fsinfo
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index 4ff841a00450..b71b34d4b45c 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -485,3 +485,4 @@
 438	common	pidfd_getfd			sys_pidfd_getfd
 439	common	watch_mount			sys_watch_mount
 440	common	watch_sb			sys_watch_sb
+441	common	fsinfo				sys_fsinfo
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index e2731d295f88..e118ba9aca4c 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -444,3 +444,4 @@
 438	i386	pidfd_getfd		sys_pidfd_getfd			__ia32_sys_pidfd_getfd
 439	i386	watch_mount		sys_watch_mount			__ia32_sys_watch_mount
 440	i386	watch_sb		sys_watch_sb			__ia32_sys_watch_sb
+441	i386	fsinfo			sys_fsinfo			__ia32_sys_fsinfo
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index f4391176102c..067f247471d0 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -361,6 +361,7 @@
 438	common	pidfd_getfd		__x64_sys_pidfd_getfd
 439	common	watch_mount		__x64_sys_watch_mount
 440	common	watch_sb		__x64_sys_watch_sb
+441	common	fsinfo			__x64_sys_fsinfo
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl
index 8e7d731ed6cf..e1ec25099d10 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -410,3 +410,4 @@
 438	common	pidfd_getfd			sys_pidfd_getfd
 439	common	watch_mount			sys_watch_mount
 440	common	watch_sb			sys_watch_sb
+441	common	fsinfo				sys_fsinfo
diff --git a/fs/Kconfig b/fs/Kconfig
index fef1365c23a5..01d0d436b3cd 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -15,6 +15,13 @@ config VALIDATE_FS_PARSER
 	  Enable this to perform validation of the parameter description for a
 	  filesystem when it is registered.
 
+config FSINFO
+	bool "Enable the fsinfo() system call"
+	help
+	  Enable the file system information querying system call to allow
+	  comprehensive information to be retrieved about a filesystem,
+	  superblock or mount object.
+
 if BLOCK
 
 config FS_IOMAP
diff --git a/fs/Makefile b/fs/Makefile
index 4477757780d0..b6bf2424c7f7 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -55,6 +55,7 @@ obj-$(CONFIG_COREDUMP)		+= coredump.o
 obj-$(CONFIG_SYSCTL)		+= drop_caches.o
 
 obj-$(CONFIG_FHANDLE)		+= fhandle.o
+obj-$(CONFIG_FSINFO)		+= fsinfo.o
 obj-y				+= iomap/
 
 obj-y				+= quota/
diff --git a/fs/fsinfo.c b/fs/fsinfo.c
new file mode 100644
index 000000000000..1830c73f37a7
--- /dev/null
+++ b/fs/fsinfo.c
@@ -0,0 +1,586 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Filesystem information query.
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+#include <linux/syscalls.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/statfs.h>
+#include <linux/security.h>
+#include <linux/uaccess.h>
+#include <linux/fsinfo.h>
+#include <uapi/linux/mount.h>
+#include "internal.h"
+
+/**
+ * fsinfo_string - Store a NUL-terminated string as an fsinfo attribute value.
+ * @s: The string to store (may be NULL)
+ * @ctx: The parameter context
+ */
+int fsinfo_string(const char *s, struct fsinfo_context *ctx)
+{
+	unsigned int len;
+	char *p = ctx->buffer;
+	int ret = 0;
+
+	if (s) {
+		len = min_t(size_t, strlen(s), ctx->buf_size - 1);
+		if (!ctx->want_size_only) {
+			memcpy(p, s, len);
+			p[len] = 0;
+		}
+		ret = len;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(fsinfo_string);
+
+/*
+ * Get basic filesystem stats from statfs.
+ */
+static int fsinfo_generic_statfs(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_statfs *p = ctx->buffer;
+	struct kstatfs buf;
+	int ret;
+
+	ret = vfs_statfs(path, &buf);
+	if (ret < 0)
+		return ret;
+
+	p->f_blocks.lo	= buf.f_blocks;
+	p->f_bfree.lo	= buf.f_bfree;
+	p->f_bavail.lo	= buf.f_bavail;
+	p->f_files.lo	= buf.f_files;
+	p->f_ffree.lo	= buf.f_ffree;
+	p->f_favail.lo	= buf.f_ffree;
+	p->f_bsize	= buf.f_bsize;
+	p->f_frsize	= buf.f_frsize;
+	return sizeof(*p);
+}
+
+static int fsinfo_generic_ids(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_ids *p = ctx->buffer;
+	struct super_block *sb;
+	struct kstatfs buf;
+	int ret;
+
+	ret = vfs_statfs(path, &buf);
+	if (ret < 0 && ret != -ENOSYS)
+		return ret;
+	if (ret == 0)
+		memcpy(&p->f_fsid, &buf.f_fsid, sizeof(p->f_fsid));
+
+	sb = path->dentry->d_sb;
+	p->f_fstype	= sb->s_magic;
+	p->f_dev_major	= MAJOR(sb->s_dev);
+	p->f_dev_minor	= MINOR(sb->s_dev);
+	p->f_sb_id	= sb->s_unique_id;
+	strlcpy(p->f_fs_name, sb->s_type->name, sizeof(p->f_fs_name));
+	return sizeof(*p);
+}
+
+int fsinfo_generic_limits(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_limits *p = ctx->buffer;
+	struct super_block *sb = path->dentry->d_sb;
+
+	p->max_file_size.hi	= 0;
+	p->max_file_size.lo	= sb->s_maxbytes;
+	p->max_ino.hi		= 0;
+	p->max_ino.lo		= UINT_MAX;
+	p->max_hard_links	= sb->s_max_links;
+	p->max_uid		= UINT_MAX;
+	p->max_gid		= UINT_MAX;
+	p->max_projid		= UINT_MAX;
+	p->max_filename_len	= NAME_MAX;
+	p->max_symlink_len	= PATH_MAX;
+	p->max_xattr_name_len	= XATTR_NAME_MAX;
+	p->max_xattr_body_len	= XATTR_SIZE_MAX;
+	p->max_dev_major	= 0xffffff;
+	p->max_dev_minor	= 0xff;
+	return sizeof(*p);
+}
+EXPORT_SYMBOL(fsinfo_generic_limits);
+
+int fsinfo_generic_supports(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_supports *p = ctx->buffer;
+	struct super_block *sb = path->dentry->d_sb;
+
+	p->stx_mask = STATX_BASIC_STATS;
+	if (sb->s_d_op && sb->s_d_op->d_automount)
+		p->stx_attributes |= STATX_ATTR_AUTOMOUNT;
+	return sizeof(*p);
+}
+EXPORT_SYMBOL(fsinfo_generic_supports);
+
+static const struct fsinfo_timestamp_info fsinfo_default_timestamp_info = {
+	.atime = {
+		.minimum	= S64_MIN,
+		.maximum	= S64_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+	.mtime = {
+		.minimum	= S64_MIN,
+		.maximum	= S64_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+	.ctime = {
+		.minimum	= S64_MIN,
+		.maximum	= S64_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+	.btime = {
+		.minimum	= S64_MIN,
+		.maximum	= S64_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+};
+
+int fsinfo_generic_timestamp_info(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_timestamp_info *p = ctx->buffer;
+	struct super_block *sb = path->dentry->d_sb;
+	s8 exponent;
+
+	*p = fsinfo_default_timestamp_info;
+
+	if (sb->s_time_gran < 1000000000) {
+		if (sb->s_time_gran < 1000)
+			exponent = -9;
+		else if (sb->s_time_gran < 1000000)
+			exponent = -6;
+		else
+			exponent = -3;
+
+		p->atime.gran_exponent = exponent;
+		p->mtime.gran_exponent = exponent;
+		p->ctime.gran_exponent = exponent;
+		p->btime.gran_exponent = exponent;
+	}
+
+	return sizeof(*p);
+}
+EXPORT_SYMBOL(fsinfo_generic_timestamp_info);
+
+static int fsinfo_generic_volume_uuid(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_volume_uuid *p = ctx->buffer;
+	struct super_block *sb = path->dentry->d_sb;
+
+	memcpy(p, &sb->s_uuid, sizeof(*p));
+	return sizeof(*p);
+}
+
+static int fsinfo_generic_volume_id(struct path *path, struct fsinfo_context *ctx)
+{
+	return fsinfo_string(path->dentry->d_sb->s_id, ctx);
+}
+
+static const struct fsinfo_attribute fsinfo_common_attributes[] = {
+	FSINFO_VSTRUCT	(FSINFO_ATTR_STATFS,		fsinfo_generic_statfs),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_IDS,		fsinfo_generic_ids),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_LIMITS,		fsinfo_generic_limits),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_SUPPORTS,		fsinfo_generic_supports),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_TIMESTAMP_INFO,	fsinfo_generic_timestamp_info),
+	FSINFO_STRING	(FSINFO_ATTR_VOLUME_ID,		fsinfo_generic_volume_id),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_VOLUME_UUID,	fsinfo_generic_volume_uuid),
+
+	FSINFO_LIST	(FSINFO_ATTR_FSINFO_ATTRIBUTES,	(void *)123UL),
+	FSINFO_VSTRUCT_N(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, (void *)123UL),
+	{}
+};
+
+/*
+ * Determine an attribute's minimum buffer size and, if the buffer is large
+ * enough, get the attribute value.
+ */
+static int fsinfo_get_this_attribute(struct path *path,
+				     struct fsinfo_context *ctx,
+				     const struct fsinfo_attribute *attr)
+{
+	int buf_size;
+
+	if (ctx->Nth != 0 && !(attr->flags & (FSINFO_FLAGS_N | FSINFO_FLAGS_NM)))
+		return -ENODATA;
+	if (ctx->Mth != 0 && !(attr->flags & FSINFO_FLAGS_NM))
+		return -ENODATA;
+
+	switch (attr->type) {
+	case FSINFO_TYPE_VSTRUCT:
+		ctx->clear_tail = true;
+		buf_size = attr->size;
+		break;
+	case FSINFO_TYPE_STRING:
+	case FSINFO_TYPE_OPAQUE:
+	case FSINFO_TYPE_LIST:
+		buf_size = 4096;
+		break;
+	default:
+		return -ENOPKG;
+	}
+
+	if (ctx->buf_size < buf_size)
+		return buf_size;
+
+	return attr->get(path, ctx);
+}
+
+static void fsinfo_attributes_insert(struct fsinfo_context *ctx,
+				     const struct fsinfo_attribute *attr)
+{
+	__u32 *p = ctx->buffer;
+	unsigned int i;
+
+	if (ctx->usage >= ctx->buf_size ||
+	    ctx->buf_size - ctx->usage < sizeof(__u32)) {
+		ctx->usage += sizeof(__u32);
+		return;
+	}
+
+	for (i = 0; i < ctx->usage / sizeof(__u32); i++)
+		if (p[i] == attr->attr_id)
+			return;
+
+	p[i] = attr->attr_id;
+	ctx->usage += sizeof(__u32);
+}
+
+static int fsinfo_list_attributes(struct path *path,
+				  struct fsinfo_context *ctx,
+				  const struct fsinfo_attribute *attributes)
+{
+	const struct fsinfo_attribute *a;
+
+	for (a = attributes; a->get; a++)
+		fsinfo_attributes_insert(ctx, a);
+	return -EOPNOTSUPP; /* We want to go through all the lists */
+}
+
+static int fsinfo_get_attribute_info(struct path *path,
+				     struct fsinfo_context *ctx,
+				     const struct fsinfo_attribute *attributes)
+{
+	const struct fsinfo_attribute *a;
+	struct fsinfo_attribute_info *p = ctx->buffer;
+
+	if (!ctx->buf_size)
+		return sizeof(*p);
+
+	for (a = attributes; a->get; a++) {
+		if (a->attr_id == ctx->Nth) {
+			p->attr_id	= a->attr_id;
+			p->type		= a->type;
+			p->flags	= a->flags;
+			p->size		= a->size;
+			p->size		= a->size;
+			return sizeof(*p);
+		}
+	}
+	return -EOPNOTSUPP; /* We want to go through all the lists */
+}
+
+/**
+ * fsinfo_get_attribute - Look up and handle an attribute
+ * @path: The object to query
+ * @params: Parameters to define a request and place to store result
+ * @attributes: List of attributes to search.
+ *
+ * Look through a list of attributes for one that matches the requested
+ * attribute then call the handler for it.
+ */
+int fsinfo_get_attribute(struct path *path, struct fsinfo_context *ctx,
+			 const struct fsinfo_attribute *attributes)
+{
+	const struct fsinfo_attribute *a;
+
+	switch (ctx->requested_attr) {
+	case FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO:
+		return fsinfo_get_attribute_info(path, ctx, attributes);
+	case FSINFO_ATTR_FSINFO_ATTRIBUTES:
+		return fsinfo_list_attributes(path, ctx, attributes);
+	default:
+		for (a = attributes; a->get; a++)
+			if (a->attr_id == ctx->requested_attr)
+				return fsinfo_get_this_attribute(path, ctx, a);
+		return -EOPNOTSUPP;
+	}
+}
+EXPORT_SYMBOL(fsinfo_get_attribute);
+
+/**
+ * generic_fsinfo - Handle an fsinfo attribute generically
+ * @path: The object to query
+ * @params: Parameters to define a request and place to store result
+ */
+static int fsinfo_call(struct path *path, struct fsinfo_context *ctx)
+{
+	int ret;
+
+	if (path->dentry->d_sb->s_op->fsinfo) {
+		ret = path->dentry->d_sb->s_op->fsinfo(path, ctx);
+		if (ret != -EOPNOTSUPP)
+			return ret;
+	}
+	ret = fsinfo_get_attribute(path, ctx, fsinfo_common_attributes);
+	if (ret != -EOPNOTSUPP)
+		return ret;
+
+	switch (ctx->requested_attr) {
+	case FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO:
+		return -ENODATA;
+	case FSINFO_ATTR_FSINFO_ATTRIBUTES:
+		return ctx->usage;
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+/**
+ * vfs_fsinfo - Retrieve filesystem information
+ * @path: The object to query
+ * @params: Parameters to define a request and place to store result
+ *
+ * Get an attribute on a filesystem or an object within a filesystem.  The
+ * filesystem attribute to be queried is indicated by @ctx->requested_attr, and
+ * if it's a multi-valued attribute, the particular value is selected by
+ * @ctx->Nth and then @ctx->Mth.
+ *
+ * For common attributes, a value may be fabricated if it is not supported by
+ * the filesystem.
+ *
+ * On success, the size of the attribute's value is returned (0 is a valid
+ * size).  A buffer will have been allocated and will be pointed to by
+ * @ctx->buffer.  The caller must free this with kvfree().
+ *
+ * Errors can also be returned: -ENOMEM if a buffer cannot be allocated, -EPERM
+ * or -EACCES if permission is denied by the LSM, -EOPNOTSUPP if an attribute
+ * doesn't exist for the specified object or -ENODATA if the attribute exists,
+ * but the Nth,Mth value does not exist.  -EMSGSIZE indicates that the value is
+ * unmanageable internally and -ENOPKG indicates other internal failure.
+ *
+ * Errors such as -EIO may also come from attempts to access media or servers
+ * to obtain the requested information if it's not immediately to hand.
+ *
+ * [*] Note that the caller may set @ctx->want_size_only if it only wants the
+ *     size of the value and not the data.  If this is set, a buffer may not be
+ *     allocated under some circumstances.  This is intended for size query by
+ *     userspace.
+ *
+ * [*] Note that @ctx->clear_tail will be returned set if the data should be
+ *     padded out with zeros when writing it to userspace.
+ */
+static int vfs_fsinfo(struct path *path, struct fsinfo_context *ctx)
+{
+	struct dentry *dentry = path->dentry;
+	int ret;
+
+	ret = security_sb_statfs(dentry);
+	if (ret)
+		return ret;
+
+	/* Call the handler to find out the buffer size required. */
+	ctx->buf_size = 0;
+	ret = fsinfo_call(path, ctx);
+	if (ret < 0 || ctx->want_size_only)
+		return ret;
+	ctx->buf_size = ret;
+
+	do {
+		/* Allocate a buffer of the requested size. */
+		if (ctx->buf_size > INT_MAX)
+			return -EMSGSIZE;
+		ctx->buffer = kvzalloc(ctx->buf_size, GFP_KERNEL);
+		if (!ctx->buffer)
+			return -ENOMEM;
+
+		ctx->usage = 0;
+		ctx->skip = 0;
+		ret = fsinfo_call(path, ctx);
+		if (IS_ERR_VALUE((long)ret))
+			return ret;
+		if ((unsigned int)ret <= ctx->buf_size)
+			return ret; /* It fitted */
+
+		/* We need to resize the buffer */
+		ctx->buf_size = roundup(ret, PAGE_SIZE);
+		kvfree(ctx->buffer);
+		ctx->buffer = NULL;
+	} while (!signal_pending(current));
+
+	return -ERESTARTSYS;
+}
+
+static int vfs_fsinfo_path(int dfd, const char __user *pathname,
+			   const struct fsinfo_params *up,
+			   struct fsinfo_context *ctx)
+{
+	struct path path;
+	unsigned lookup_flags = LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT;
+	int ret = -EINVAL;
+
+	if (up->resolve_flags & ~VALID_RESOLVE_FLAGS)
+		return -EINVAL;
+	if (up->at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT |
+			     AT_EMPTY_PATH))
+		return -EINVAL;
+
+	if (up->resolve_flags & RESOLVE_NO_XDEV)
+		lookup_flags |= LOOKUP_NO_XDEV;
+	if (up->resolve_flags & RESOLVE_NO_MAGICLINKS)
+		lookup_flags |= LOOKUP_NO_MAGICLINKS;
+	if (up->resolve_flags & RESOLVE_NO_SYMLINKS)
+		lookup_flags |= LOOKUP_NO_SYMLINKS;
+	if (up->resolve_flags & RESOLVE_BENEATH)
+		lookup_flags |= LOOKUP_BENEATH;
+	if (up->resolve_flags & RESOLVE_IN_ROOT)
+		lookup_flags |= LOOKUP_IN_ROOT;
+	if (up->at_flags & AT_SYMLINK_NOFOLLOW)
+		lookup_flags &= ~LOOKUP_FOLLOW;
+	if (up->at_flags & AT_NO_AUTOMOUNT)
+		lookup_flags &= ~LOOKUP_AUTOMOUNT;
+	if (up->at_flags & AT_EMPTY_PATH)
+		lookup_flags |= LOOKUP_EMPTY;
+
+retry:
+	ret = user_path_at(dfd, pathname, lookup_flags, &path);
+	if (ret)
+		goto out;
+
+	ret = vfs_fsinfo(&path, ctx);
+	path_put(&path);
+	if (retry_estale(ret, lookup_flags)) {
+		lookup_flags |= LOOKUP_REVAL;
+		goto retry;
+	}
+out:
+	return ret;
+}
+
+static int vfs_fsinfo_fd(unsigned int fd, struct fsinfo_context *ctx)
+{
+	struct fd f = fdget_raw(fd);
+	int ret = -EBADF;
+
+	if (f.file) {
+		ret = vfs_fsinfo(&f.file->f_path, ctx);
+		fdput(f);
+	}
+	return ret;
+}
+
+/**
+ * sys_fsinfo - System call to get filesystem information
+ * @dfd: Base directory to pathwalk from or fd referring to filesystem.
+ * @pathname: Filesystem to query or NULL.
+ * @params: Parameters to define request (NULL: FSINFO_ATTR_STATFS).
+ * @params_size: Size of parameter buffer.
+ * @result_buffer: Result buffer.
+ * @result_buf_size: Size of result buffer.
+ *
+ * Get information on a filesystem.  The filesystem attribute to be queried is
+ * indicated by @_params->request, and some of the attributes can have multiple
+ * values, indexed by @_params->Nth and @_params->Mth.  If @_params is NULL,
+ * then the 0th fsinfo_attr_statfs attribute is queried.  If an attribute does
+ * not exist, EOPNOTSUPP is returned; if the Nth,Mth value does not exist,
+ * ENODATA is returned.
+ *
+ * On success, the size of the attribute's value is returned.  If
+ * @result_buf_size is 0 or @result_buffer is NULL, only the size is returned.
+ * If the size of the value is larger than @result_buf_size, it will be
+ * truncated by the copy.  If the size of the value is smaller than
+ * @result_buf_size then the excess buffer space will be cleared.  The full
+ * size of the value will be returned, irrespective of how much data is
+ * actually placed in the buffer.
+ */
+SYSCALL_DEFINE6(fsinfo,
+		int, dfd,
+		const char __user *, pathname,
+		const struct fsinfo_params __user *, params,
+		size_t, params_size,
+		void __user *, result_buffer,
+		size_t, result_buf_size)
+{
+	struct fsinfo_context ctx;
+	struct fsinfo_params user_params;
+	unsigned int result_size;
+	void *r;
+	int ret;
+
+	if ((!params &&  params_size) ||
+	    ( params && !params_size) ||
+	    (!result_buffer &&  result_buf_size) ||
+	    ( result_buffer && !result_buf_size))
+		return -EINVAL;
+	if (result_buf_size > UINT_MAX)
+		return -EOVERFLOW;
+
+	memset(&ctx, 0, sizeof(ctx));
+	ctx.requested_attr	= FSINFO_ATTR_STATFS;
+	ctx.flags		= FSINFO_FLAGS_QUERY_PATH;
+	ctx.want_size_only	= (result_buf_size == 0);
+
+	if (params) {
+		ret = copy_struct_from_user(&user_params, sizeof(user_params),
+					    params, params_size);
+		if (ret < 0)
+			return ret;
+		if (user_params.flags & ~FSINFO_FLAGS_QUERY_MASK)
+			return -EINVAL;
+		ctx.flags = user_params.flags;
+		ctx.requested_attr = user_params.request;
+		ctx.Nth = user_params.Nth;
+		ctx.Mth = user_params.Mth;
+	}
+
+	switch (ctx.flags & FSINFO_FLAGS_QUERY_MASK) {
+	case FSINFO_FLAGS_QUERY_PATH:
+		ret = vfs_fsinfo_path(dfd, pathname, &user_params, &ctx);
+		break;
+	case FSINFO_FLAGS_QUERY_FD:
+		if (pathname)
+			return -EINVAL;
+		ret = vfs_fsinfo_fd(dfd, &ctx);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (ret < 0)
+		goto error;
+
+	r = ctx.buffer + ctx.skip;
+	result_size = min_t(size_t, ret, result_buf_size);
+	if (result_size > 0 &&
+	    copy_to_user(result_buffer, r, result_size) != 0) {
+		ret = -EFAULT;
+		goto error;
+	}
+
+	/* Clear any part of the buffer that we won't fill if we're putting a
+	 * struct in there.  Strings, opaque objects and arrays are expected to
+	 * be variable length.
+	 */
+	if (ctx.clear_tail &&
+	    result_buf_size > result_size &&
+	    clear_user(result_buffer + result_size,
+		       result_buf_size - result_size) != 0) {
+		ret = -EFAULT;
+		goto error;
+	}
+
+error:
+	kvfree(ctx.buffer);
+	return ret;
+}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b8d639540dc2..3abcb6a196fd 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -69,6 +69,7 @@ struct fsverity_info;
 struct fsverity_operations;
 struct fs_context;
 struct fs_parameter_spec;
+struct fsinfo_context;
 
 extern void __init inode_init(void);
 extern void __init inode_init_early(void);
@@ -1964,6 +1965,9 @@ struct super_operations {
 	int (*thaw_super) (struct super_block *);
 	int (*unfreeze_fs) (struct super_block *);
 	int (*statfs) (struct dentry *, struct kstatfs *);
+#ifdef CONFIG_FSINFO
+	int (*fsinfo)(struct path *, struct fsinfo_context *);
+#endif
 	int (*remount_fs) (struct super_block *, int *, char *);
 	void (*umount_begin) (struct super_block *);
 
diff --git a/include/linux/fsinfo.h b/include/linux/fsinfo.h
new file mode 100644
index 000000000000..bf806669b4fb
--- /dev/null
+++ b/include/linux/fsinfo.h
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Filesystem information query
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _LINUX_FSINFO_H
+#define _LINUX_FSINFO_H
+
+#ifdef CONFIG_FSINFO
+
+#include <uapi/linux/fsinfo.h>
+
+struct path;
+
+#define FSINFO_NORMAL_ATTR_MAX_SIZE 4096
+
+struct fsinfo_context {
+	__u32		flags;		/* [in] FSINFO_FLAGS_* */
+	__u32		requested_attr;	/* [in] What is being asking for */
+	__u32		Nth;		/* [in] Instance of it (some may have multiple) */
+	__u32		Mth;		/* [in] Subinstance */
+	bool		want_size_only;	/* [in] Just want to know the size, not the data */
+	bool		clear_tail;	/* [out] T if tail of buffer should be cleared */
+	unsigned int	skip;		/* [out] Number of bytes to skip in buffer */
+	unsigned int	usage;		/* [tmp] Amount of buffer used (if large) */
+	unsigned int	buf_size;	/* [tmp] Size of ->buffer[] */
+	void		*buffer;	/* [out] The reply buffer */
+};
+
+/*
+ * A filesystem information attribute definition.
+ */
+struct fsinfo_attribute {
+	unsigned int		attr_id;	/* The ID of the attribute */
+	enum fsinfo_value_type	type:8;		/* The type of the attribute's value(s) */
+	unsigned int		flags:8;
+	unsigned int		size:16;	/* - Value size (FSINFO_STRUCT/LIST) */
+	int (*get)(struct path *path, struct fsinfo_context *params);
+};
+
+#define __FSINFO(A, T, S, G, F) \
+	{ .attr_id = A, .type = T, .flags = F, .size = S, .get = G }
+
+#define _FSINFO(A, T, S, G)	__FSINFO(A, T, S, G, 0)
+#define _FSINFO_N(A, T, S, G)	__FSINFO(A, T, S, G, FSINFO_FLAGS_N)
+#define _FSINFO_NM(A, T, S, G)	__FSINFO(A, T, S, G, FSINFO_FLAGS_NM)
+
+#define _FSINFO_VSTRUCT(A,S,G)	  _FSINFO   (A, FSINFO_TYPE_VSTRUCT, sizeof(S), G)
+#define _FSINFO_VSTRUCT_N(A,S,G)  _FSINFO_N (A, FSINFO_TYPE_VSTRUCT, sizeof(S), G)
+#define _FSINFO_VSTRUCT_NM(A,S,G) _FSINFO_NM(A, FSINFO_TYPE_VSTRUCT, sizeof(S), G)
+
+#define FSINFO_VSTRUCT(A,G)	_FSINFO_VSTRUCT   (A, A##__STRUCT, G)
+#define FSINFO_VSTRUCT_N(A,G)	_FSINFO_VSTRUCT_N (A, A##__STRUCT, G)
+#define FSINFO_VSTRUCT_NM(A,G)	_FSINFO_VSTRUCT_NM(A, A##__STRUCT, G)
+#define FSINFO_STRING(A,G)	_FSINFO   (A, FSINFO_TYPE_STRING, 0, G)
+#define FSINFO_STRING_N(A,G)	_FSINFO_N (A, FSINFO_TYPE_STRING, 0, G)
+#define FSINFO_STRING_NM(A,G)	_FSINFO_NM(A, FSINFO_TYPE_STRING, 0, G)
+#define FSINFO_OPAQUE(A,G)	_FSINFO   (A, FSINFO_TYPE_OPAQUE, 0, G)
+#define FSINFO_LIST(A,G)	_FSINFO   (A, FSINFO_TYPE_LIST, sizeof(A##__STRUCT), G)
+#define FSINFO_LIST_N(A,G)	_FSINFO_N (A, FSINFO_TYPE_LIST, sizeof(A##__STRUCT), G)
+
+extern int fsinfo_string(const char *, struct fsinfo_context *);
+extern int fsinfo_generic_timestamp_info(struct path *, struct fsinfo_context *);
+extern int fsinfo_generic_supports(struct path *, struct fsinfo_context *);
+extern int fsinfo_generic_limits(struct path *, struct fsinfo_context *);
+extern int fsinfo_get_attribute(struct path *, struct fsinfo_context *,
+				const struct fsinfo_attribute *);
+
+#endif /* CONFIG_FSINFO */
+
+#endif /* _LINUX_FSINFO_H */
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index c84440d57f52..76064c0807e5 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -47,6 +47,7 @@ struct stat64;
 struct statfs;
 struct statfs64;
 struct statx;
+struct fsinfo_params;
 struct __sysctl_args;
 struct sysinfo;
 struct timespec;
@@ -1007,6 +1008,9 @@ asmlinkage long sys_watch_mount(int dfd, const char __user *path,
 				unsigned int at_flags, int watch_fd, int watch_id);
 asmlinkage long sys_watch_sb(int dfd, const char __user *path,
 			     unsigned int at_flags, int watch_fd, int watch_id);
+asmlinkage long sys_fsinfo(int dfd, const char __user *pathname,
+			   struct fsinfo_params __user *params, size_t params_size,
+			   void __user *result_buffer, size_t result_buf_size);
 
 /*
  * Architecture-specific system calls
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 5bff318b7ffa..7d764f86d3f5 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -859,9 +859,11 @@ __SYSCALL(__NR_pidfd_getfd, sys_pidfd_getfd)
 __SYSCALL(__NR_watch_mount, sys_watch_mount)
 #define __NR_watch_sb 440
 __SYSCALL(__NR_watch_sb, sys_watch_sb)
+#define __NR_fsinfo 441
+__SYSCALL(__NR_fsinfo, sys_fsinfo)
 
 #undef __NR_syscalls
-#define __NR_syscalls 441
+#define __NR_syscalls 442
 
 /*
  * 32 bit systems traditionally used different
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
new file mode 100644
index 000000000000..e9b35b9b7629
--- /dev/null
+++ b/include/uapi/linux/fsinfo.h
@@ -0,0 +1,187 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* fsinfo() definitions.
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+#ifndef _UAPI_LINUX_FSINFO_H
+#define _UAPI_LINUX_FSINFO_H
+
+#include <linux/types.h>
+#include <linux/socket.h>
+#include <linux/openat2.h>
+
+/*
+ * The filesystem attributes that can be requested.  Note that some attributes
+ * may have multiple instances which can be switched in the parameter block.
+ */
+#define FSINFO_ATTR_STATFS		0x00	/* statfs()-style state */
+#define FSINFO_ATTR_IDS			0x01	/* Filesystem IDs */
+#define FSINFO_ATTR_LIMITS		0x02	/* Filesystem limits */
+#define FSINFO_ATTR_SUPPORTS		0x03	/* What's supported in statx, iocflags, ... */
+#define FSINFO_ATTR_TIMESTAMP_INFO	0x04	/* Inode timestamp info */
+#define FSINFO_ATTR_VOLUME_ID		0x05	/* Volume ID (string) */
+#define FSINFO_ATTR_VOLUME_UUID		0x06	/* Volume UUID (LE uuid) */
+#define FSINFO_ATTR_VOLUME_NAME		0x07	/* Volume name (string) */
+
+#define FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO 0x100	/* Information about attr N (for path) */
+#define FSINFO_ATTR_FSINFO_ATTRIBUTES	0x101	/* List of supported attrs (for path) */
+
+/*
+ * Optional fsinfo() parameter structure.
+ *
+ * If this is not given, it is assumed that fsinfo_attr_statfs instance 0,0 is
+ * desired.
+ */
+struct fsinfo_params {
+	__u64	resolve_flags;	/* RESOLVE_* flags */
+	__u32	at_flags;	/* AT_* flags */
+	__u32	flags;		/* Flags controlling fsinfo() specifically */
+#define FSINFO_FLAGS_QUERY_MASK	0x0007 /* What object should fsinfo() query? */
+#define FSINFO_FLAGS_QUERY_PATH	0x0000 /* - path, specified by dirfd,pathname,AT_EMPTY_PATH */
+#define FSINFO_FLAGS_QUERY_FD	0x0001 /* - fd specified by dirfd */
+	__u32	request;	/* ID of requested attribute */
+	__u32	Nth;		/* Instance of it (some may have multiple) */
+	__u32	Mth;		/* Subinstance of Nth instance */
+};
+
+enum fsinfo_value_type {
+	FSINFO_TYPE_VSTRUCT	= 0,	/* Version-lengthed struct (up to 4096 bytes) */
+	FSINFO_TYPE_STRING	= 1,	/* NUL-term var-length string (up to 4095 chars) */
+	FSINFO_TYPE_OPAQUE	= 2,	/* Opaque blob (unlimited size) */
+	FSINFO_TYPE_LIST	= 3,	/* List of ints/structs (unlimited size) */
+};
+
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO).
+ *
+ * This gives information about the attributes supported by fsinfo for the
+ * given path.
+ */
+struct fsinfo_attribute_info {
+	unsigned int		attr_id;	/* The ID of the attribute */
+	enum fsinfo_value_type	type;		/* The type of the attribute's value(s) */
+	unsigned int		flags;
+#define FSINFO_FLAGS_N		0x01		/* - Attr has a set of values */
+#define FSINFO_FLAGS_NM		0x02		/* - Attr has a set of sets of values */
+	unsigned int		size;		/* - Value size (FSINFO_STRUCT/FSINFO_LIST) */
+};
+
+#define FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO__STRUCT struct fsinfo_attribute_info
+#define FSINFO_ATTR_FSINFO_ATTRIBUTES__STRUCT __u32
+
+struct fsinfo_u128 {
+#if defined(__BYTE_ORDER) ? __BYTE_ORDER == __BIG_ENDIAN : defined(__BIG_ENDIAN)
+	__u64	hi;
+	__u64	lo;
+#elif defined(__BYTE_ORDER) ? __BYTE_ORDER == __LITTLE_ENDIAN : defined(__LITTLE_ENDIAN)
+	__u64	lo;
+	__u64	hi;
+#endif
+};
+
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_STATFS).
+ * - This gives extended filesystem information.
+ */
+struct fsinfo_statfs {
+	struct fsinfo_u128 f_blocks;	/* Total number of blocks in fs */
+	struct fsinfo_u128 f_bfree;	/* Total number of free blocks */
+	struct fsinfo_u128 f_bavail;	/* Number of free blocks available to ordinary user */
+	struct fsinfo_u128 f_files;	/* Total number of file nodes in fs */
+	struct fsinfo_u128 f_ffree;	/* Number of free file nodes */
+	struct fsinfo_u128 f_favail;	/* Number of file nodes available to ordinary user */
+	__u64	f_bsize;		/* Optimal block size */
+	__u64	f_frsize;		/* Fragment size */
+};
+
+#define FSINFO_ATTR_STATFS__STRUCT struct fsinfo_statfs
+
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_IDS).
+ *
+ * List of basic identifiers as is normally found in statfs().
+ */
+struct fsinfo_ids {
+	char	f_fs_name[15 + 1];	/* Filesystem name */
+	__u64	f_fsid;			/* Short 64-bit Filesystem ID (as statfs) */
+	__u64	f_sb_id;		/* Internal superblock ID for sbnotify()/mntnotify() */
+	__u32	f_fstype;		/* Filesystem type from linux/magic.h [uncond] */
+	__u32	f_dev_major;		/* As st_dev_* from struct statx [uncond] */
+	__u32	f_dev_minor;
+	__u32	__padding[1];
+};
+
+#define FSINFO_ATTR_IDS__STRUCT struct fsinfo_ids
+
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_LIMITS).
+ *
+ * List of supported filesystem limits.
+ */
+struct fsinfo_limits {
+	struct fsinfo_u128 max_file_size;	/* Maximum file size */
+	struct fsinfo_u128 max_ino;		/* Maximum inode number */
+	__u64	max_uid;			/* Maximum UID supported */
+	__u64	max_gid;			/* Maximum GID supported */
+	__u64	max_projid;			/* Maximum project ID supported */
+	__u64	max_hard_links;			/* Maximum number of hard links on a file */
+	__u64	max_xattr_body_len;		/* Maximum xattr content length */
+	__u32	max_xattr_name_len;		/* Maximum xattr name length */
+	__u32	max_filename_len;		/* Maximum filename length */
+	__u32	max_symlink_len;		/* Maximum symlink content length */
+	__u32	max_dev_major;			/* Maximum device major representable */
+	__u32	max_dev_minor;			/* Maximum device minor representable */
+	__u32	__padding[1];
+};
+
+#define FSINFO_ATTR_LIMITS__STRUCT struct fsinfo_limits
+
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_SUPPORTS).
+ *
+ * What's supported in various masks, such as statx() attribute and mask bits
+ * and IOC flags.
+ */
+struct fsinfo_supports {
+	__u64	stx_attributes;		/* What statx::stx_attributes are supported */
+	__u32	stx_mask;		/* What statx::stx_mask bits are supported */
+	__u32	fs_ioc_getflags;	/* What FS_IOC_GETFLAGS may return */
+	__u32	fs_ioc_setflags_set;	/* What FS_IOC_SETFLAGS may set */
+	__u32	fs_ioc_setflags_clear;	/* What FS_IOC_SETFLAGS may clear */
+	__u32	win_file_attrs;		/* What DOS/Windows FILE_* attributes are supported */
+	__u32	__padding[1];
+};
+
+#define FSINFO_ATTR_SUPPORTS__STRUCT struct fsinfo_supports
+
+struct fsinfo_timestamp_one {
+	__s64	minimum;	/* Minimum timestamp value in seconds */
+	__s64	maximum;	/* Maximum timestamp value in seconds */
+	__u16	gran_mantissa;	/* Granularity(secs) = mant * 10^exp */
+	__s8	gran_exponent;
+	__u8	__padding[5];
+};
+
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_TIMESTAMP_INFO).
+ */
+struct fsinfo_timestamp_info {
+	struct fsinfo_timestamp_one	atime;	/* Access time */
+	struct fsinfo_timestamp_one	mtime;	/* Modification time */
+	struct fsinfo_timestamp_one	ctime;	/* Change time */
+	struct fsinfo_timestamp_one	btime;	/* Birth/creation time */
+};
+
+#define FSINFO_ATTR_TIMESTAMP_INFO__STRUCT struct fsinfo_timestamp_info
+
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_VOLUME_UUID).
+ */
+struct fsinfo_volume_uuid {
+	__u8	uuid[16];
+};
+
+#define FSINFO_ATTR_VOLUME_UUID__STRUCT struct fsinfo_volume_uuid
+
+#endif /* _UAPI_LINUX_FSINFO_H */
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 0ce01f86e5db..519317f3904c 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -51,6 +51,7 @@ COND_SYSCALL_COMPAT(io_pgetevents);
 COND_SYSCALL(io_uring_setup);
 COND_SYSCALL(io_uring_enter);
 COND_SYSCALL(io_uring_register);
+COND_SYSCALL(fsinfo);
 
 /* fs/xattr.c */
 
diff --git a/samples/vfs/Makefile b/samples/vfs/Makefile
index 65acdde5c117..9159ad1d7fc5 100644
--- a/samples/vfs/Makefile
+++ b/samples/vfs/Makefile
@@ -1,10 +1,15 @@
 # SPDX-License-Identifier: GPL-2.0-only
 # List of programs to build
+
 hostprogs := \
+	test-fsinfo \
 	test-fsmount \
 	test-statx
 
 always-y := $(hostprogs)
 
+HOSTCFLAGS_test-fsinfo.o += -I$(objtree)/usr/include
+HOSTLDLIBS_test-fsinfo += -static -lm
+
 HOSTCFLAGS_test-fsmount.o += -I$(objtree)/usr/include
 HOSTCFLAGS_test-statx.o += -I$(objtree)/usr/include
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
new file mode 100644
index 000000000000..2b53c735d330
--- /dev/null
+++ b/samples/vfs/test-fsinfo.c
@@ -0,0 +1,633 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Test the fsinfo() system call
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define _GNU_SOURCE
+#define _ATFILE_SOURCE
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
+#include <ctype.h>
+#include <errno.h>
+#include <time.h>
+#include <math.h>
+#include <fcntl.h>
+#include <sys/syscall.h>
+#include <linux/fsinfo.h>
+#include <linux/socket.h>
+#include <sys/stat.h>
+#include <arpa/inet.h>
+
+#ifndef __NR_fsinfo
+#define __NR_fsinfo -1
+#endif
+
+static bool debug = 0;
+static bool list_last;
+
+static __attribute__((unused))
+ssize_t fsinfo(int dfd, const char *filename,
+	       struct fsinfo_params *params, size_t params_size,
+	       void *result_buffer, size_t result_buf_size)
+{
+	return syscall(__NR_fsinfo, dfd, filename,
+		       params, params_size,
+		       result_buffer, result_buf_size);
+}
+
+struct fsinfo_attribute {
+	unsigned int		attr_id;
+	enum fsinfo_value_type	type;
+	unsigned int		size;
+	const char		*name;
+	void (*dump)(void *reply, unsigned int size);
+};
+
+static const struct fsinfo_attribute fsinfo_attributes[];
+
+static ssize_t get_fsinfo(const char *, const char *, struct fsinfo_params *, void **);
+
+static void dump_hex(unsigned int *data, int from, int to)
+{
+	unsigned offset, print_offset = 1, col = 0;
+
+	from /= 4;
+	to = (to + 3) / 4;
+
+	for (offset = from; offset < to; offset++) {
+		if (print_offset) {
+			printf("%04x: ", offset * 8);
+			print_offset = 0;
+		}
+		printf("%08x", data[offset]);
+		col++;
+		if ((col & 3) == 0) {
+			printf("\n");
+			print_offset = 1;
+		} else {
+			printf(" ");
+		}
+	}
+
+	if (!print_offset)
+		printf("\n");
+}
+
+static void dump_attribute_info(void *reply, unsigned int size)
+{
+	struct fsinfo_attribute_info *attr_info = reply;
+	const struct fsinfo_attribute *attr;
+	char type[32], val_size[32];
+
+	switch (attr_info->type) {
+	case FSINFO_TYPE_VSTRUCT:	strcpy(type, "V-STRUCT");	break;
+	case FSINFO_TYPE_STRING:	strcpy(type, "STRING");		break;
+	case FSINFO_TYPE_OPAQUE:	strcpy(type, "OPAQUE");		break;
+	case FSINFO_TYPE_LIST:		strcpy(type, "LIST");		break;
+	default:
+		sprintf(type, "type-%x", attr_info->type);
+		break;
+	}
+
+	if (attr_info->flags & FSINFO_FLAGS_N)
+		strcat(type, " x N");
+	else if (attr_info->flags & FSINFO_FLAGS_NM)
+		strcat(type, " x NM");
+
+	for (attr = fsinfo_attributes; attr->name; attr++)
+		if (attr->attr_id == attr_info->attr_id)
+			break;
+
+	if (attr_info->size)
+		sprintf(val_size, "%u", attr_info->size);
+	else
+		strcpy(val_size, "-");
+
+	printf("%8x %-12s %08x %5s %s\n",
+	       attr_info->attr_id,
+	       type,
+	       attr_info->flags,
+	       val_size,
+	       attr->name ? attr->name : "");
+}
+
+static void dump_fsinfo_generic_statfs(void *reply, unsigned int size)
+{
+	struct fsinfo_statfs *f = reply;
+
+	printf("\n");
+	printf("\tblocks       : n=%llu fr=%llu av=%llu\n",
+	       (unsigned long long)f->f_blocks.lo,
+	       (unsigned long long)f->f_bfree.lo,
+	       (unsigned long long)f->f_bavail.lo);
+
+	printf("\tfiles        : n=%llu fr=%llu av=%llu\n",
+	       (unsigned long long)f->f_files.lo,
+	       (unsigned long long)f->f_ffree.lo,
+	       (unsigned long long)f->f_favail.lo);
+	printf("\tbsize        : %llu\n", f->f_bsize);
+	printf("\tfrsize       : %llu\n", f->f_frsize);
+}
+
+static void dump_fsinfo_generic_ids(void *reply, unsigned int size)
+{
+	struct fsinfo_ids *f = reply;
+
+	printf("\n");
+	printf("\tdev          : %02x:%02x\n", f->f_dev_major, f->f_dev_minor);
+	printf("\tfs           : type=%x name=%s\n", f->f_fstype, f->f_fs_name);
+	printf("\tfsid         : %llx\n", (unsigned long long)f->f_fsid);
+	printf("\tsbid         : %llx\n", (unsigned long long)f->f_sb_id);
+}
+
+static void dump_fsinfo_generic_limits(void *reply, unsigned int size)
+{
+	struct fsinfo_limits *f = reply;
+
+	printf("\n");
+	printf("\tmax file size: %llx%016llx\n",
+	       (unsigned long long)f->max_file_size.hi,
+	       (unsigned long long)f->max_file_size.lo);
+	printf("\tmax ino      : %llx%016llx\n",
+	       (unsigned long long)f->max_ino.hi,
+	       (unsigned long long)f->max_ino.lo);
+	printf("\tmax ids      : u=%llx g=%llx p=%llx\n",
+	       (unsigned long long)f->max_uid,
+	       (unsigned long long)f->max_gid,
+	       (unsigned long long)f->max_projid);
+	printf("\tmax dev      : maj=%x min=%x\n",
+	       f->max_dev_major, f->max_dev_minor);
+	printf("\tmax links    : %llx\n",
+	       (unsigned long long)f->max_hard_links);
+	printf("\tmax xattr    : n=%x b=%llx\n",
+	       f->max_xattr_name_len,
+	       (unsigned long long)f->max_xattr_body_len);
+	printf("\tmax len      : file=%x sym=%x\n",
+	       f->max_filename_len, f->max_symlink_len);
+}
+
+static void dump_fsinfo_generic_supports(void *reply, unsigned int size)
+{
+	struct fsinfo_supports *f = reply;
+
+	printf("\n");
+	printf("\tstx_attr     : %llx\n", (unsigned long long)f->stx_attributes);
+	printf("\tstx_mask     : %x\n", f->stx_mask);
+	printf("\tfs_ioc_*flags: get=%x set=%x clr=%x\n",
+	       f->fs_ioc_getflags, f->fs_ioc_setflags_set, f->fs_ioc_setflags_clear);
+	printf("\twin_fattrs   : %x\n", f->win_file_attrs);
+}
+
+static void print_time(struct fsinfo_timestamp_one *t, char stamp)
+{
+	printf("\t%ctime       : gran=%gs range=%llx-%llx\n",
+	       stamp,
+	       t->gran_mantissa * pow(10., t->gran_exponent),
+	       (long long)t->minimum,
+	       (long long)t->maximum);
+}
+
+static void dump_fsinfo_generic_timestamp_info(void *reply, unsigned int size)
+{
+	struct fsinfo_timestamp_info *f = reply;
+
+	printf("\n");
+	print_time(&f->atime, 'a');
+	print_time(&f->mtime, 'm');
+	print_time(&f->ctime, 'c');
+	print_time(&f->btime, 'b');
+}
+
+static void dump_fsinfo_generic_volume_uuid(void *reply, unsigned int size)
+{
+	struct fsinfo_volume_uuid *f = reply;
+
+	printf("%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x"
+	       "-%02x%02x%02x%02x%02x%02x\n",
+	       f->uuid[ 0], f->uuid[ 1],
+	       f->uuid[ 2], f->uuid[ 3],
+	       f->uuid[ 4], f->uuid[ 5],
+	       f->uuid[ 6], f->uuid[ 7],
+	       f->uuid[ 8], f->uuid[ 9],
+	       f->uuid[10], f->uuid[11],
+	       f->uuid[12], f->uuid[13],
+	       f->uuid[14], f->uuid[15]);
+}
+
+static void dump_string(void *reply, unsigned int size)
+{
+	char *s = reply, *p;
+	bool nl = false, last_nl = false;
+
+	p = s;
+	if (size >= 4096) {
+		size = 4096;
+		p[4092] = '.';
+		p[4093] = '.';
+		p[4094] = '.';
+		p[4095] = 0;
+	} else {
+		p[size] = 0;
+	}
+
+	for (p = s; *p; p++) {
+		if (*p == '\n') {
+			last_nl = nl = true;
+			continue;
+		}
+		last_nl = false;
+		if (!isprint(*p) && *p != '\t')
+			*p = '?';
+	}
+
+	if (nl)
+		putchar('\n');
+	printf("%s", s);
+	if (!last_nl)
+		putchar('\n');
+}
+
+#define dump_fsinfo_meta_attribute_info		(void *)0x123
+#define dump_fsinfo_meta_attributes		(void *)0x123
+
+/*
+ *
+ */
+#define __FSINFO(A, T, S, G, F, N)					\
+	{ .attr_id = A, .type = T, .size = S, .name = N, .dump = dump_##G }
+
+#define _FSINFO(A,T,S,G,N)	__FSINFO(A, T, S, G, 0, N)
+#define _FSINFO_N(A,T,S,G,N)	__FSINFO(A, T, S, G, FSINFO_FLAGS_N, N)
+#define _FSINFO_NM(A,T,S,G,N)	__FSINFO(A, T, S, G, FSINFO_FLAGS_NM, N)
+
+#define _FSINFO_VSTRUCT(A,S,G,N)    _FSINFO   (A, FSINFO_TYPE_VSTRUCT, sizeof(S), G, N)
+#define _FSINFO_VSTRUCT_N(A,S,G,N)  _FSINFO_N (A, FSINFO_TYPE_VSTRUCT, sizeof(S), G, N)
+#define _FSINFO_VSTRUCT_NM(A,S,G,N) _FSINFO_NM(A, FSINFO_TYPE_VSTRUCT, sizeof(S), G, N)
+
+#define FSINFO_VSTRUCT(A,G)	_FSINFO_VSTRUCT   (A, A##__STRUCT, G, #A)
+#define FSINFO_VSTRUCT_N(A,G)	_FSINFO_VSTRUCT_N (A, A##__STRUCT, G, #A)
+#define FSINFO_VSTRUCT_NM(A,G)	_FSINFO_VSTRUCT_NM(A, A##__STRUCT, G, #A)
+#define FSINFO_STRING(A,G)	_FSINFO   (A, FSINFO_TYPE_STRING, 0, G, #A)
+#define FSINFO_STRING_N(A,G)	_FSINFO_N (A, FSINFO_TYPE_STRING, 0, G, #A)
+#define FSINFO_STRING_NM(A,G)	_FSINFO_NM(A, FSINFO_TYPE_STRING, 0, G, #A)
+#define FSINFO_OPAQUE(A,G)	_FSINFO   (A, FSINFO_TYPE_OPAQUE, 0, G, #A)
+#define FSINFO_LIST(A,G)	_FSINFO   (A, FSINFO_TYPE_LIST, sizeof(A##__STRUCT), G, #A)
+#define FSINFO_LIST_N(A,G)	_FSINFO_N (A, FSINFO_TYPE_LIST, sizeof(A##__STRUCT), G, #A)
+
+static const struct fsinfo_attribute fsinfo_attributes[] = {
+	FSINFO_VSTRUCT	(FSINFO_ATTR_STATFS,		fsinfo_generic_statfs),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_IDS,		fsinfo_generic_ids),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_LIMITS,		fsinfo_generic_limits),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_SUPPORTS,		fsinfo_generic_supports),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_TIMESTAMP_INFO,	fsinfo_generic_timestamp_info),
+	FSINFO_STRING	(FSINFO_ATTR_VOLUME_ID,		string),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_VOLUME_UUID,	fsinfo_generic_volume_uuid),
+	FSINFO_STRING	(FSINFO_ATTR_VOLUME_NAME,	string),
+	FSINFO_VSTRUCT_N(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, fsinfo_meta_attribute_info),
+	FSINFO_LIST	(FSINFO_ATTR_FSINFO_ATTRIBUTES,	fsinfo_meta_attributes),
+	{}
+};
+
+static void dump_value(unsigned int attr_id,
+		       const struct fsinfo_attribute *attr,
+		       const struct fsinfo_attribute_info *attr_info,
+		       void *reply, unsigned int size)
+{
+	if (!attr || !attr->dump) {
+		printf("<no dumper>\n");
+		return;
+	}
+
+	if (attr->type == FSINFO_TYPE_VSTRUCT && size < attr->size) {
+		printf("<short data %u/%u>\n", size, attr->size);
+		return;
+	}
+
+	attr->dump(reply, size);
+}
+
+static void dump_list(unsigned int attr_id,
+		      const struct fsinfo_attribute *attr,
+		      const struct fsinfo_attribute_info *attr_info,
+		      void *reply, unsigned int size)
+{
+	size_t elem_size = attr_info->size;
+	unsigned int ix = 0;
+
+	printf("\n");
+	if (!attr || !attr->dump) {
+		printf("<no dumper>\n");
+		return;
+	}
+
+	if (attr->type == FSINFO_TYPE_VSTRUCT && size < attr->size) {
+		printf("<short data %u/%u>\n", size, attr->size);
+		return;
+	}
+
+	list_last = false;
+	while (size >= elem_size) {
+		printf("\t[%02x] ", ix);
+		if (size == elem_size)
+			list_last = true;
+		attr->dump(reply, size);
+		reply += elem_size;
+		size -= elem_size;
+		ix++;
+	}
+}
+
+/*
+ * Call fsinfo, expanding the buffer as necessary.
+ */
+static ssize_t get_fsinfo(const char *file, const char *name,
+			  struct fsinfo_params *params, void **_r)
+{
+	ssize_t ret;
+	size_t buf_size = 4096;
+	void *r;
+
+	for (;;) {
+		r = malloc(buf_size);
+		if (!r) {
+			perror("malloc");
+			exit(1);
+		}
+		memset(r, 0xbd, buf_size);
+
+		errno = 0;
+		ret = fsinfo(AT_FDCWD, file, params, sizeof(*params), r, buf_size - 1);
+		if (ret == -1)
+			goto error;
+
+		if (ret <= buf_size - 1)
+			break;
+		buf_size = (ret + 4096 - 1) & ~(4096 - 1);
+	}
+
+	if (debug)
+		printf("fsinfo(%s,%s,%u,%u) = %zd\n",
+		       file, name, params->Nth, params->Mth, ret);
+
+	((char *)r)[ret] = 0;
+	*_r = r;
+	return ret;
+
+error:
+	*_r = NULL;
+	free(r);
+	if (debug)
+		printf("fsinfo(%s,%s,%u,%u) = %m\n",
+		       file, name, params->Nth, params->Mth);
+	return ret;
+}
+
+/*
+ * Try one subinstance of an attribute.
+ */
+static int try_one(const char *file, struct fsinfo_params *params,
+		   const struct fsinfo_attribute_info *attr_info, bool raw)
+{
+	const struct fsinfo_attribute *attr;
+	const char *name;
+	size_t size = 4096;
+	char namebuf[32];
+	void *r;
+
+	for (attr = fsinfo_attributes; attr->name; attr++) {
+		if (attr->attr_id == params->request) {
+			name = attr->name;
+			if (strncmp(name, "fsinfo_generic_", 15) == 0)
+				name += 15;
+			goto found;
+		}
+	}
+
+	sprintf(namebuf, "<unknown-%x>", params->request);
+	name = namebuf;
+	attr = NULL;
+
+found:
+	size = get_fsinfo(file, name, params, &r);
+
+	if (size == -1) {
+		if (errno == ENODATA) {
+			if (!(attr_info->flags & (FSINFO_FLAGS_N | FSINFO_FLAGS_NM)) &&
+			    params->Nth == 0 && params->Mth == 0) {
+				fprintf(stderr,
+					"Unexpected ENODATA (0x%x{%u}{%u})\n",
+					params->request, params->Nth, params->Mth);
+				exit(1);
+			}
+			free(r);
+			return (params->Mth == 0) ? 2 : 1;
+		}
+		if (errno == EOPNOTSUPP) {
+			if (params->Nth > 0 || params->Mth > 0) {
+				fprintf(stderr,
+					"Should return -ENODATA (0x%x{%u}{%u})\n",
+					params->request, params->Nth, params->Mth);
+				exit(1);
+			}
+			//printf("\e[33m%s\e[m: <not supported>\n",
+			//       fsinfo_attr_names[attr]);
+			free(r);
+			return 2;
+		}
+		perror(file);
+		exit(1);
+	}
+
+	if (raw) {
+		if (size > 4096)
+			size = 4096;
+		dump_hex(r, 0, size);
+		free(r);
+		return 0;
+	}
+
+	switch (attr_info->flags & (FSINFO_FLAGS_N | FSINFO_FLAGS_NM)) {
+	case 0:
+		printf("\e[33m%s\e[m: ", name);
+		break;
+	case FSINFO_FLAGS_N:
+		printf("\e[33m%s{%u}\e[m: ", name, params->Nth);
+		break;
+	case FSINFO_FLAGS_NM:
+		printf("\e[33m%s{%u,%u}\e[m: ", name, params->Nth, params->Mth);
+		break;
+	}
+
+	switch (attr_info->type) {
+	case FSINFO_TYPE_VSTRUCT:
+	case FSINFO_TYPE_STRING:
+		dump_value(params->request, attr, attr_info, r, size);
+		free(r);
+		return 0;
+
+	case FSINFO_TYPE_LIST:
+		dump_list(params->request, attr, attr_info, r, size);
+		free(r);
+		return 0;
+
+	case FSINFO_TYPE_OPAQUE:
+		free(r);
+		return 0;
+
+	default:
+		fprintf(stderr, "Fishy about %u 0x%x,%x,%x\n",
+			params->request, attr_info->type, attr_info->flags, attr_info->size);
+		exit(1);
+	}
+}
+
+static int cmp_u32(const void *a, const void *b)
+{
+	return *(const int *)a - *(const int *)b;
+}
+
+/*
+ *
+ */
+int main(int argc, char **argv)
+{
+	struct fsinfo_attribute_info attr_info;
+	struct fsinfo_params params = {
+		.at_flags	= AT_SYMLINK_NOFOLLOW,
+		.flags		= FSINFO_FLAGS_QUERY_PATH,
+	};
+	unsigned int *attrs, ret, nr, i;
+	bool meta = false;
+	int raw = 0, opt, Nth, Mth;
+
+	while ((opt = getopt(argc, argv, "Madlr"))) {
+		switch (opt) {
+		case 'M':
+			meta = true;
+			continue;
+		case 'a':
+			params.at_flags |= AT_NO_AUTOMOUNT;
+			params.flags = FSINFO_FLAGS_QUERY_PATH;
+			continue;
+		case 'd':
+			debug = true;
+			continue;
+		case 'l':
+			params.at_flags &= ~AT_SYMLINK_NOFOLLOW;
+			params.flags = FSINFO_FLAGS_QUERY_PATH;
+			continue;
+		case 'r':
+			raw = 1;
+			continue;
+		}
+		break;
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	if (argc != 1) {
+		printf("Format: test-fsinfo [-Madlr] <path>\n");
+		exit(2);
+	}
+
+	/* Retrieve a list of supported attribute IDs */
+	params.request = FSINFO_ATTR_FSINFO_ATTRIBUTES;
+	params.Nth = 0;
+	params.Mth = 0;
+	ret = get_fsinfo(argv[0], "attributes", &params, (void **)&attrs);
+	if (ret == -1) {
+		fprintf(stderr, "Unable to get attribute list: %m\n");
+		exit(1);
+	}
+
+	if (ret % sizeof(attrs[0])) {
+		fprintf(stderr, "Bad length of attribute list (0x%x)\n", ret);
+		exit(2);
+	}
+
+	nr = ret / sizeof(attrs[0]);
+	qsort(attrs, nr, sizeof(attrs[0]), cmp_u32);
+
+	if (meta) {
+		printf("ATTR ID  TYPE         FLAGS    SIZE  NAME\n");
+		printf("======== ============ ======== ===== =========\n");
+		for (i = 0; i < nr; i++) {
+			params.request = FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO;
+			params.Nth = attrs[i];
+			params.Mth = 0;
+			ret = fsinfo(AT_FDCWD, argv[0],
+				     &params, sizeof(params),
+				     &attr_info, sizeof(attr_info));
+			if (ret == -1) {
+				fprintf(stderr, "Can't get info for attribute %x: %m\n", attrs[i]);
+				exit(1);
+			}
+
+			dump_attribute_info(&attr_info, ret);
+		}
+		exit(0);
+	}
+
+	for (i = 0; i < nr; i++) {
+		params.request = FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO;
+		params.Nth = attrs[i];
+		params.Mth = 0;
+		ret = fsinfo(AT_FDCWD, argv[0],
+			     &params, sizeof(params),
+			     &attr_info, sizeof(attr_info));
+		if (ret == -1) {
+			fprintf(stderr, "Can't get info for attribute %x: %m\n", attrs[i]);
+			exit(1);
+		}
+
+		if (attrs[i] == FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO ||
+		    attrs[i] == FSINFO_ATTR_FSINFO_ATTRIBUTES)
+			continue;
+
+		if (attrs[i] != attr_info.attr_id) {
+			fprintf(stderr, "ID for %03x returned %03x\n",
+				attrs[i], attr_info.attr_id);
+			break;
+		}
+		Nth = 0;
+		do {
+			Mth = 0;
+			do {
+				params.request = attrs[i];
+				params.Nth = Nth;
+				params.Mth = Mth;
+
+				switch (try_one(argv[0], &params, &attr_info, raw)) {
+				case 0:
+					continue;
+				case 1:
+					goto done_M;
+				case 2:
+					goto done_N;
+				}
+			} while (++Mth < 100);
+
+		done_M:
+			if (Mth >= 100) {
+				fprintf(stderr, "Fishy: Mth %x[%u][%u]\n", attrs[i], Nth, Mth);
+				break;
+			}
+
+		} while (++Nth < 100);
+
+	done_N:
+		if (Nth >= 100) {
+			fprintf(stderr, "Fishy: Nth %x[%u]\n", attrs[i], Nth);
+			break;
+		}
+	}
+
+	return 0;
+}



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 02/13] fsinfo: Provide a bitmap of supported features [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
  2020-03-18 15:08 ` [PATCH 01/13] fsinfo: Add fsinfo() syscall to query filesystem " David Howells
@ 2020-03-18 15:08 ` David Howells
  2020-03-18 15:08 ` [PATCH 03/13] fsinfo: Allow retrieval of superblock devname, options and stats " David Howells
                   ` (12 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:08 UTC (permalink / raw)
  To: torvalds, viro
  Cc: dhowells, raven, mszeredi, christian, jannh, darrick.wong, kzak,
	jlayton, linux-api, linux-fsdevel, linux-security-module,
	linux-kernel

Provide a bitmap of features that a filesystem may provide for the path
being queried.  Features include such things as:

 (1) The general class of filesystem, such as kernel-interface,
     block-based, flash-based, network-based.

 (2) Supported inode features, such as which timestamps are supported,
     whether simple numeric user, group or project IDs are supported and
     whether user identification is actually more complex behind the
     scenes.

 (3) Supported volume features, such as it having a UUID, a name or a
     filesystem ID.

 (4) Supported filesystem features, such as what types of file are
     supported, whether sparse files, extended attributes and quotas are
     supported.

 (5) Supported interface features, such as whether locking and leases are
     supported, what open flags are honoured and how i_version is managed.

For some filesystems, this may be an immutable set and can just be memcpy'd
into the reply buffer.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/fsinfo.c                 |   30 +++++++++++++++++++
 include/linux/fsinfo.h      |   38 ++++++++++++++++++++++++
 include/uapi/linux/fsinfo.h |   67 ++++++++++++++++++++++++++++++++++++++++++
 samples/vfs/test-fsinfo.c   |   69 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 204 insertions(+)

diff --git a/fs/fsinfo.c b/fs/fsinfo.c
index 1830c73f37a7..8aee78a6b584 100644
--- a/fs/fsinfo.c
+++ b/fs/fsinfo.c
@@ -121,6 +121,35 @@ int fsinfo_generic_supports(struct path *path, struct fsinfo_context *ctx)
 }
 EXPORT_SYMBOL(fsinfo_generic_supports);
 
+int fsinfo_generic_features(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_features *p = ctx->buffer;
+	struct super_block *sb = path->dentry->d_sb;
+
+	fsinfo_init_features(p);
+	if (sb->s_mtd)
+		fsinfo_set_feature(p, FSINFO_FEAT_IS_FLASH_FS);
+	else if (sb->s_bdev)
+		fsinfo_set_feature(p, FSINFO_FEAT_IS_BLOCK_FS);
+
+	if (sb->s_quota_types & QTYPE_MASK_USR)
+		fsinfo_set_feature(p, FSINFO_FEAT_USER_QUOTAS);
+	if (sb->s_quota_types & QTYPE_MASK_GRP)
+		fsinfo_set_feature(p, FSINFO_FEAT_GROUP_QUOTAS);
+	if (sb->s_quota_types & QTYPE_MASK_PRJ)
+		fsinfo_set_feature(p, FSINFO_FEAT_PROJECT_QUOTAS);
+	if (sb->s_d_op && sb->s_d_op->d_automount)
+		fsinfo_set_feature(p, FSINFO_FEAT_AUTOMOUNTS);
+	if (sb->s_id[0])
+		fsinfo_set_feature(p, FSINFO_FEAT_VOLUME_ID);
+
+	fsinfo_set_feature(p, FSINFO_FEAT_HAS_ATIME);
+	fsinfo_set_feature(p, FSINFO_FEAT_HAS_CTIME);
+	fsinfo_set_feature(p, FSINFO_FEAT_HAS_MTIME);
+	return sizeof(*p);
+}
+EXPORT_SYMBOL(fsinfo_generic_features);
+
 static const struct fsinfo_timestamp_info fsinfo_default_timestamp_info = {
 	.atime = {
 		.minimum	= S64_MIN,
@@ -196,6 +225,7 @@ static const struct fsinfo_attribute fsinfo_common_attributes[] = {
 	FSINFO_VSTRUCT	(FSINFO_ATTR_TIMESTAMP_INFO,	fsinfo_generic_timestamp_info),
 	FSINFO_STRING	(FSINFO_ATTR_VOLUME_ID,		fsinfo_generic_volume_id),
 	FSINFO_VSTRUCT	(FSINFO_ATTR_VOLUME_UUID,	fsinfo_generic_volume_uuid),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_FEATURES,		fsinfo_generic_features),
 
 	FSINFO_LIST	(FSINFO_ATTR_FSINFO_ATTRIBUTES,	(void *)123UL),
 	FSINFO_VSTRUCT_N(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, (void *)123UL),
diff --git a/include/linux/fsinfo.h b/include/linux/fsinfo.h
index bf806669b4fb..3f08e61c3270 100644
--- a/include/linux/fsinfo.h
+++ b/include/linux/fsinfo.h
@@ -67,6 +67,44 @@ extern int fsinfo_generic_supports(struct path *, struct fsinfo_context *);
 extern int fsinfo_generic_limits(struct path *, struct fsinfo_context *);
 extern int fsinfo_get_attribute(struct path *, struct fsinfo_context *,
 				const struct fsinfo_attribute *);
+extern int fsinfo_generic_features(struct path *, struct fsinfo_context *);
+
+static inline void fsinfo_init_features(struct fsinfo_features *p)
+{
+	p->nr_features = FSINFO_FEAT__NR;
+}
+
+static inline void fsinfo_set_feature(struct fsinfo_features *p,
+				      enum fsinfo_feature feature)
+{
+	p->features[feature / 8] |= 1 << (feature % 8);
+}
+
+static inline void fsinfo_clear_feature(struct fsinfo_features *p,
+					enum fsinfo_feature feature)
+{
+	p->features[feature / 8] &= ~(1 << (feature % 8));
+}
+
+/**
+ * fsinfo_set_unix_features - Set standard UNIX features.
+ * @f: The features mask to alter
+ */
+static inline void fsinfo_set_unix_features(struct fsinfo_features *p)
+{
+	fsinfo_set_feature(p, FSINFO_FEAT_UIDS);
+	fsinfo_set_feature(p, FSINFO_FEAT_GIDS);
+	fsinfo_set_feature(p, FSINFO_FEAT_DIRECTORIES);
+	fsinfo_set_feature(p, FSINFO_FEAT_SYMLINKS);
+	fsinfo_set_feature(p, FSINFO_FEAT_HARD_LINKS);
+	fsinfo_set_feature(p, FSINFO_FEAT_DEVICE_FILES);
+	fsinfo_set_feature(p, FSINFO_FEAT_UNIX_SPECIALS);
+	fsinfo_set_feature(p, FSINFO_FEAT_SPARSE);
+	fsinfo_set_feature(p, FSINFO_FEAT_HAS_ATIME);
+	fsinfo_set_feature(p, FSINFO_FEAT_HAS_CTIME);
+	fsinfo_set_feature(p, FSINFO_FEAT_HAS_MTIME);
+	fsinfo_set_feature(p, FSINFO_FEAT_HAS_INODE_NUMBERS);
+}
 
 #endif /* CONFIG_FSINFO */
 
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index e9b35b9b7629..83c92e202f7b 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -23,6 +23,7 @@
 #define FSINFO_ATTR_VOLUME_ID		0x05	/* Volume ID (string) */
 #define FSINFO_ATTR_VOLUME_UUID		0x06	/* Volume UUID (LE uuid) */
 #define FSINFO_ATTR_VOLUME_NAME		0x07	/* Volume name (string) */
+#define FSINFO_ATTR_FEATURES		0x08	/* Filesystem features (bits) */
 
 #define FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO 0x100	/* Information about attr N (for path) */
 #define FSINFO_ATTR_FSINFO_ATTRIBUTES	0x101	/* List of supported attrs (for path) */
@@ -155,6 +156,72 @@ struct fsinfo_supports {
 
 #define FSINFO_ATTR_SUPPORTS__STRUCT struct fsinfo_supports
 
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_FEATURES).
+ *
+ * Bitmask indicating filesystem features where renderable as single bits.
+ */
+enum fsinfo_feature {
+	FSINFO_FEAT_IS_KERNEL_FS	= 0,	/* fs is kernel-special filesystem */
+	FSINFO_FEAT_IS_BLOCK_FS		= 1,	/* fs is block-based filesystem */
+	FSINFO_FEAT_IS_FLASH_FS		= 2,	/* fs is flash filesystem */
+	FSINFO_FEAT_IS_NETWORK_FS	= 3,	/* fs is network filesystem */
+	FSINFO_FEAT_IS_AUTOMOUNTER_FS	= 4,	/* fs is automounter special filesystem */
+	FSINFO_FEAT_IS_MEMORY_FS	= 5,	/* fs is memory-based filesystem */
+	FSINFO_FEAT_AUTOMOUNTS		= 6,	/* fs supports automounts */
+	FSINFO_FEAT_ADV_LOCKS		= 7,	/* fs supports advisory file locking */
+	FSINFO_FEAT_MAND_LOCKS		= 8,	/* fs supports mandatory file locking */
+	FSINFO_FEAT_LEASES		= 9,	/* fs supports file leases */
+	FSINFO_FEAT_UIDS		= 10,	/* fs supports numeric uids */
+	FSINFO_FEAT_GIDS		= 11,	/* fs supports numeric gids */
+	FSINFO_FEAT_PROJIDS		= 12,	/* fs supports numeric project ids */
+	FSINFO_FEAT_STRING_USER_IDS	= 13,	/* fs supports string user identifiers */
+	FSINFO_FEAT_GUID_USER_IDS	= 14,	/* fs supports GUID user identifiers */
+	FSINFO_FEAT_WINDOWS_ATTRS	= 15,	/* fs has windows attributes */
+	FSINFO_FEAT_USER_QUOTAS		= 16,	/* fs has per-user quotas */
+	FSINFO_FEAT_GROUP_QUOTAS	= 17,	/* fs has per-group quotas */
+	FSINFO_FEAT_PROJECT_QUOTAS	= 18,	/* fs has per-project quotas */
+	FSINFO_FEAT_XATTRS		= 19,	/* fs has xattrs */
+	FSINFO_FEAT_JOURNAL		= 20,	/* fs has a journal */
+	FSINFO_FEAT_DATA_IS_JOURNALLED	= 21,	/* fs is using data journalling */
+	FSINFO_FEAT_O_SYNC		= 22,	/* fs supports O_SYNC */
+	FSINFO_FEAT_O_DIRECT		= 23,	/* fs supports O_DIRECT */
+	FSINFO_FEAT_VOLUME_ID		= 24,	/* fs has a volume ID */
+	FSINFO_FEAT_VOLUME_UUID		= 25,	/* fs has a volume UUID */
+	FSINFO_FEAT_VOLUME_NAME		= 26,	/* fs has a volume name */
+	FSINFO_FEAT_VOLUME_FSID		= 27,	/* fs has a volume FSID */
+	FSINFO_FEAT_IVER_ALL_CHANGE	= 28,	/* i_version represents data + meta changes */
+	FSINFO_FEAT_IVER_DATA_CHANGE	= 29,	/* i_version represents data changes only */
+	FSINFO_FEAT_IVER_MONO_INCR	= 30,	/* i_version incremented monotonically */
+	FSINFO_FEAT_DIRECTORIES		= 31,	/* fs supports (sub)directories */
+	FSINFO_FEAT_SYMLINKS		= 32,	/* fs supports symlinks */
+	FSINFO_FEAT_HARD_LINKS		= 33,	/* fs supports hard links */
+	FSINFO_FEAT_HARD_LINKS_1DIR	= 34,	/* fs supports hard links in same dir only */
+	FSINFO_FEAT_DEVICE_FILES	= 35,	/* fs supports bdev, cdev */
+	FSINFO_FEAT_UNIX_SPECIALS	= 36,	/* fs supports pipe, fifo, socket */
+	FSINFO_FEAT_RESOURCE_FORKS	= 37,	/* fs supports resource forks/streams */
+	FSINFO_FEAT_NAME_CASE_INDEP	= 38,	/* Filename case independence is mandatory */
+	FSINFO_FEAT_NAME_NON_UTF8	= 39,	/* fs has non-utf8 names */
+	FSINFO_FEAT_NAME_HAS_CODEPAGE	= 40,	/* fs has a filename codepage */
+	FSINFO_FEAT_SPARSE		= 41,	/* fs supports sparse files */
+	FSINFO_FEAT_NOT_PERSISTENT	= 42,	/* fs is not persistent */
+	FSINFO_FEAT_NO_UNIX_MODE	= 43,	/* fs does not support unix mode bits */
+	FSINFO_FEAT_HAS_ATIME		= 44,	/* fs supports access time */
+	FSINFO_FEAT_HAS_BTIME		= 45,	/* fs supports birth/creation time */
+	FSINFO_FEAT_HAS_CTIME		= 46,	/* fs supports change time */
+	FSINFO_FEAT_HAS_MTIME		= 47,	/* fs supports modification time */
+	FSINFO_FEAT_HAS_ACL		= 48,	/* fs supports ACLs of some sort */
+	FSINFO_FEAT_HAS_INODE_NUMBERS	= 49,	/* fs has inode numbers */
+	FSINFO_FEAT__NR
+};
+
+struct fsinfo_features {
+	__u32	nr_features;	/* Number of supported features (FSINFO_FEAT__NR) */
+	__u8	features[(FSINFO_FEAT__NR + 7) / 8];
+};
+
+#define FSINFO_ATTR_FEATURES__STRUCT struct fsinfo_features
+
 struct fsinfo_timestamp_one {
 	__s64	minimum;	/* Minimum timestamp value in seconds */
 	__s64	maximum;	/* Maximum timestamp value in seconds */
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index 2b53c735d330..bae9e6a46e72 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -184,6 +184,74 @@ static void dump_fsinfo_generic_supports(void *reply, unsigned int size)
 	printf("\twin_fattrs   : %x\n", f->win_file_attrs);
 }
 
+#define FSINFO_FEATURE_NAME(C) [FSINFO_FEAT_##C] = #C
+static const char *fsinfo_feature_names[FSINFO_FEAT__NR] = {
+	FSINFO_FEATURE_NAME(IS_KERNEL_FS),
+	FSINFO_FEATURE_NAME(IS_BLOCK_FS),
+	FSINFO_FEATURE_NAME(IS_FLASH_FS),
+	FSINFO_FEATURE_NAME(IS_NETWORK_FS),
+	FSINFO_FEATURE_NAME(IS_AUTOMOUNTER_FS),
+	FSINFO_FEATURE_NAME(IS_MEMORY_FS),
+	FSINFO_FEATURE_NAME(AUTOMOUNTS),
+	FSINFO_FEATURE_NAME(ADV_LOCKS),
+	FSINFO_FEATURE_NAME(MAND_LOCKS),
+	FSINFO_FEATURE_NAME(LEASES),
+	FSINFO_FEATURE_NAME(UIDS),
+	FSINFO_FEATURE_NAME(GIDS),
+	FSINFO_FEATURE_NAME(PROJIDS),
+	FSINFO_FEATURE_NAME(STRING_USER_IDS),
+	FSINFO_FEATURE_NAME(GUID_USER_IDS),
+	FSINFO_FEATURE_NAME(WINDOWS_ATTRS),
+	FSINFO_FEATURE_NAME(USER_QUOTAS),
+	FSINFO_FEATURE_NAME(GROUP_QUOTAS),
+	FSINFO_FEATURE_NAME(PROJECT_QUOTAS),
+	FSINFO_FEATURE_NAME(XATTRS),
+	FSINFO_FEATURE_NAME(JOURNAL),
+	FSINFO_FEATURE_NAME(DATA_IS_JOURNALLED),
+	FSINFO_FEATURE_NAME(O_SYNC),
+	FSINFO_FEATURE_NAME(O_DIRECT),
+	FSINFO_FEATURE_NAME(VOLUME_ID),
+	FSINFO_FEATURE_NAME(VOLUME_UUID),
+	FSINFO_FEATURE_NAME(VOLUME_NAME),
+	FSINFO_FEATURE_NAME(VOLUME_FSID),
+	FSINFO_FEATURE_NAME(IVER_ALL_CHANGE),
+	FSINFO_FEATURE_NAME(IVER_DATA_CHANGE),
+	FSINFO_FEATURE_NAME(IVER_MONO_INCR),
+	FSINFO_FEATURE_NAME(DIRECTORIES),
+	FSINFO_FEATURE_NAME(SYMLINKS),
+	FSINFO_FEATURE_NAME(HARD_LINKS),
+	FSINFO_FEATURE_NAME(HARD_LINKS_1DIR),
+	FSINFO_FEATURE_NAME(DEVICE_FILES),
+	FSINFO_FEATURE_NAME(UNIX_SPECIALS),
+	FSINFO_FEATURE_NAME(RESOURCE_FORKS),
+	FSINFO_FEATURE_NAME(NAME_CASE_INDEP),
+	FSINFO_FEATURE_NAME(NAME_NON_UTF8),
+	FSINFO_FEATURE_NAME(NAME_HAS_CODEPAGE),
+	FSINFO_FEATURE_NAME(SPARSE),
+	FSINFO_FEATURE_NAME(NOT_PERSISTENT),
+	FSINFO_FEATURE_NAME(NO_UNIX_MODE),
+	FSINFO_FEATURE_NAME(HAS_ATIME),
+	FSINFO_FEATURE_NAME(HAS_BTIME),
+	FSINFO_FEATURE_NAME(HAS_CTIME),
+	FSINFO_FEATURE_NAME(HAS_MTIME),
+	FSINFO_FEATURE_NAME(HAS_ACL),
+	FSINFO_FEATURE_NAME(HAS_INODE_NUMBERS),
+};
+
+static void dump_fsinfo_generic_features(void *reply, unsigned int size)
+{
+	struct fsinfo_features *f = reply;
+	int i;
+
+	printf("\n\t");
+	for (i = 0; i < sizeof(f->features); i++)
+		printf("%02x", f->features[i]);
+	printf(" (nr=%u)\n", f->nr_features);
+	for (i = 0; i < FSINFO_FEAT__NR; i++)
+		if (f->features[i / 8] & (1 << (i % 8)))
+			printf("\t- %s\n", fsinfo_feature_names[i]);
+}
+
 static void print_time(struct fsinfo_timestamp_one *t, char stamp)
 {
 	printf("\t%ctime       : gran=%gs range=%llx-%llx\n",
@@ -285,6 +353,7 @@ static const struct fsinfo_attribute fsinfo_attributes[] = {
 	FSINFO_VSTRUCT	(FSINFO_ATTR_IDS,		fsinfo_generic_ids),
 	FSINFO_VSTRUCT	(FSINFO_ATTR_LIMITS,		fsinfo_generic_limits),
 	FSINFO_VSTRUCT	(FSINFO_ATTR_SUPPORTS,		fsinfo_generic_supports),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_FEATURES,		fsinfo_generic_features),
 	FSINFO_VSTRUCT	(FSINFO_ATTR_TIMESTAMP_INFO,	fsinfo_generic_timestamp_info),
 	FSINFO_STRING	(FSINFO_ATTR_VOLUME_ID,		string),
 	FSINFO_VSTRUCT	(FSINFO_ATTR_VOLUME_UUID,	fsinfo_generic_volume_uuid),



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 03/13] fsinfo: Allow retrieval of superblock devname, options and stats [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
  2020-03-18 15:08 ` [PATCH 01/13] fsinfo: Add fsinfo() syscall to query filesystem " David Howells
  2020-03-18 15:08 ` [PATCH 02/13] fsinfo: Provide a bitmap of supported features " David Howells
@ 2020-03-18 15:08 ` David Howells
  2020-03-18 15:08 ` [PATCH 04/13] fsinfo: Allow fsinfo() to look up a mount object by ID " David Howells
                   ` (11 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:08 UTC (permalink / raw)
  To: torvalds, viro
  Cc: dhowells, raven, mszeredi, christian, jannh, darrick.wong, kzak,
	jlayton, linux-api, linux-fsdevel, linux-security-module,
	linux-kernel

Provide fsinfo() attributes to retrieve superblock device name, options,
and statistics in string form.  The following attributes are defined:

	FSINFO_ATTR_SOURCE		- Mount-specific device name
	FSINFO_ATTR_CONFIGURATION	- Mount options
	FSINFO_ATTR_FS_STATISTICS	- Filesystem statistics

FSINFO_ATTR_SOURCE could be made indexable by params->Nth to handle the
case where there is more than one source (e.g. the bcachefs filesystem).

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/fsinfo.c                 |   41 +++++++++++++++++++++++++++++++++++++++++
 fs/internal.h               |    2 ++
 fs/namespace.c              |   39 +++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/fsinfo.h |    3 +++
 samples/vfs/test-fsinfo.c   |    4 ++++
 5 files changed, 89 insertions(+)

diff --git a/fs/fsinfo.c b/fs/fsinfo.c
index 8aee78a6b584..7389095efd4f 100644
--- a/fs/fsinfo.c
+++ b/fs/fsinfo.c
@@ -217,6 +217,44 @@ static int fsinfo_generic_volume_id(struct path *path, struct fsinfo_context *ct
 	return fsinfo_string(path->dentry->d_sb->s_id, ctx);
 }
 
+/*
+ * Retrieve the superblock configuration (mount options) as a comma-separated
+ * string.  The initial comma is stripped off.
+ */
+static int fsinfo_generic_seq_read(struct path *path, struct fsinfo_context *ctx)
+{
+	struct super_block *sb = path->dentry->d_sb;
+	struct seq_file m = {
+		.buf	= ctx->buffer,
+		.size	= ctx->buf_size,
+	};
+	int ret = 0;
+
+	switch (ctx->requested_attr) {
+	case FSINFO_ATTR_CONFIGURATION:
+		if (sb->s_op->show_options)
+			ret = sb->s_op->show_options(&m, path->mnt->mnt_root);
+		break;
+
+	case FSINFO_ATTR_FS_STATISTICS:
+		if (sb->s_op->show_stats)
+			ret = sb->s_op->show_stats(&m, path->mnt->mnt_root);
+		break;
+	}
+
+	if (ret < 0)
+		return ret;
+	if (seq_has_overflowed(&m))
+		return ctx->buf_size + PAGE_SIZE;
+	if (ctx->requested_attr == FSINFO_ATTR_CONFIGURATION) {
+		if (m.count > 0 && ((char *)ctx->buffer)[0] == ',') {
+			m.count--;
+			ctx->skip = 1;
+		}
+	}
+	return m.count;
+}
+
 static const struct fsinfo_attribute fsinfo_common_attributes[] = {
 	FSINFO_VSTRUCT	(FSINFO_ATTR_STATFS,		fsinfo_generic_statfs),
 	FSINFO_VSTRUCT	(FSINFO_ATTR_IDS,		fsinfo_generic_ids),
@@ -226,6 +264,9 @@ static const struct fsinfo_attribute fsinfo_common_attributes[] = {
 	FSINFO_STRING	(FSINFO_ATTR_VOLUME_ID,		fsinfo_generic_volume_id),
 	FSINFO_VSTRUCT	(FSINFO_ATTR_VOLUME_UUID,	fsinfo_generic_volume_uuid),
 	FSINFO_VSTRUCT	(FSINFO_ATTR_FEATURES,		fsinfo_generic_features),
+	FSINFO_STRING	(FSINFO_ATTR_SOURCE,		fsinfo_generic_mount_source),
+	FSINFO_STRING	(FSINFO_ATTR_CONFIGURATION,	fsinfo_generic_seq_read),
+	FSINFO_STRING	(FSINFO_ATTR_FS_STATISTICS,	fsinfo_generic_seq_read),
 
 	FSINFO_LIST	(FSINFO_ATTR_FSINFO_ATTRIBUTES,	(void *)123UL),
 	FSINFO_VSTRUCT_N(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, (void *)123UL),
diff --git a/fs/internal.h b/fs/internal.h
index a0d90f23593c..6f2cc77bf38d 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -91,6 +91,8 @@ extern int __mnt_want_write_file(struct file *);
 extern void __mnt_drop_write_file(struct file *);
 
 extern void dissolve_on_fput(struct vfsmount *);
+extern int fsinfo_generic_mount_source(struct path *, struct fsinfo_context *);
+
 /*
  * fs_struct.c
  */
diff --git a/fs/namespace.c b/fs/namespace.c
index 54d237251941..e26e06447993 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -30,6 +30,7 @@
 #include <uapi/linux/mount.h>
 #include <linux/fs_context.h>
 #include <linux/shmem_fs.h>
+#include <linux/fsinfo.h>
 
 #include "pnode.h"
 #include "internal.h"
@@ -3997,3 +3998,41 @@ const struct proc_ns_operations mntns_operations = {
 	.install	= mntns_install,
 	.owner		= mntns_owner,
 };
+
+#ifdef CONFIG_FSINFO
+static inline void mangle(struct seq_file *m, const char *s)
+{
+	seq_escape(m, s, " \t\n\\");
+}
+
+/*
+ * Return the mount source/device name as seen from this mountpoint.  Shared
+ * mounts may vary here and the filesystem is permitted to substitute its own
+ * rendering.
+ */
+int fsinfo_generic_mount_source(struct path *path, struct fsinfo_context *ctx)
+{
+	struct super_block *sb = path->mnt->mnt_sb;
+	struct mount *mnt = real_mount(path->mnt);
+	struct seq_file m = {
+		.buf	= ctx->buffer,
+		.size	= ctx->buf_size,
+	};
+	int ret;
+
+	if (sb->s_op->show_devname) {
+		ret = sb->s_op->show_devname(&m, mnt->mnt.mnt_root);
+		if (ret < 0)
+			return ret;
+	} else {
+		if (!mnt->mnt_devname)
+			return fsinfo_string("none", ctx);
+		mangle(&m, mnt->mnt_devname);
+	}
+
+	if (seq_has_overflowed(&m))
+		return ctx->buf_size + PAGE_SIZE;
+	return m.count;
+}
+
+#endif /* CONFIG_FSINFO */
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 83c92e202f7b..3bb4fa67f8c8 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -24,6 +24,9 @@
 #define FSINFO_ATTR_VOLUME_UUID		0x06	/* Volume UUID (LE uuid) */
 #define FSINFO_ATTR_VOLUME_NAME		0x07	/* Volume name (string) */
 #define FSINFO_ATTR_FEATURES		0x08	/* Filesystem features (bits) */
+#define FSINFO_ATTR_SOURCE		0x09	/* Superblock source/device name (string) */
+#define FSINFO_ATTR_CONFIGURATION	0x0a	/* Superblock configuration/options (string) */
+#define FSINFO_ATTR_FS_STATISTICS	0x0b	/* Superblock filesystem statistics (string) */
 
 #define FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO 0x100	/* Information about attr N (for path) */
 #define FSINFO_ATTR_FSINFO_ATTRIBUTES	0x101	/* List of supported attrs (for path) */
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index bae9e6a46e72..692639ae6d1c 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -358,6 +358,10 @@ static const struct fsinfo_attribute fsinfo_attributes[] = {
 	FSINFO_STRING	(FSINFO_ATTR_VOLUME_ID,		string),
 	FSINFO_VSTRUCT	(FSINFO_ATTR_VOLUME_UUID,	fsinfo_generic_volume_uuid),
 	FSINFO_STRING	(FSINFO_ATTR_VOLUME_NAME,	string),
+	FSINFO_STRING	(FSINFO_ATTR_SOURCE,		string),
+	FSINFO_STRING	(FSINFO_ATTR_CONFIGURATION,	string),
+	FSINFO_STRING	(FSINFO_ATTR_FS_STATISTICS,	string),
+
 	FSINFO_VSTRUCT_N(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, fsinfo_meta_attribute_info),
 	FSINFO_LIST	(FSINFO_ATTR_FSINFO_ATTRIBUTES,	fsinfo_meta_attributes),
 	{}



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 04/13] fsinfo: Allow fsinfo() to look up a mount object by ID [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (2 preceding siblings ...)
  2020-03-18 15:08 ` [PATCH 03/13] fsinfo: Allow retrieval of superblock devname, options and stats " David Howells
@ 2020-03-18 15:08 ` David Howells
  2020-03-18 15:08 ` [PATCH 05/13] fsinfo: Add a uniquifier ID to struct mount " David Howells
                   ` (10 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:08 UTC (permalink / raw)
  To: torvalds, viro
  Cc: dhowells, raven, mszeredi, christian, jannh, darrick.wong, kzak,
	jlayton, linux-api, linux-fsdevel, linux-security-module,
	linux-kernel

Allow the fsinfo() syscall to look up a mount object by ID rather than by
pathname.  This is necessary as there can be multiple mounts stacked up at
the same pathname and there's no way to look through them otherwise.

This is done by passing FSINFO_FLAGS_QUERY_MOUNT to fsinfo() in the
parameters and then passing the mount ID as a string to fsinfo() in place
of the filename:

	struct fsinfo_params params = {
		.flags	 = FSINFO_FLAGS_QUERY_MOUNT,
		.request = FSINFO_ATTR_IDS,
	};

	ret = fsinfo(AT_FDCWD, "21", &params, buffer, sizeof(buffer));

The caller is only permitted to query a mount object if the root directory
of that mount connects directly to the current chroot if dfd == AT_FDCWD[*]
or the directory specified by dfd otherwise.  Note that this is not
available to the pathwalk of any other syscall.

[*] This needs to be something other than AT_FDCWD, perhaps AT_FDROOT.

[!] This probably needs an LSM hook.

[!] This might want to check the permissions on all the intervening dirs -
    but it would have to do that under RCU conditions.

[!] This might want to check a CAP_* flag.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/fsinfo.c                 |   53 +++++++++++++++++++
 fs/internal.h               |    1 
 fs/namespace.c              |  117 ++++++++++++++++++++++++++++++++++++++++++-
 include/uapi/linux/fsinfo.h |    1 
 samples/vfs/test-fsinfo.c   |    7 ++-
 5 files changed, 175 insertions(+), 4 deletions(-)

diff --git a/fs/fsinfo.c b/fs/fsinfo.c
index 7389095efd4f..3250b9ff2905 100644
--- a/fs/fsinfo.c
+++ b/fs/fsinfo.c
@@ -551,6 +551,56 @@ static int vfs_fsinfo_fd(unsigned int fd, struct fsinfo_context *ctx)
 	return ret;
 }
 
+/*
+ * Look up the root of a mount object.  This allows access to mount objects
+ * (and their attached superblocks) that can't be retrieved by path because
+ * they're entirely covered.
+ *
+ * We only permit access to a mount that has a direct path between either the
+ * dentry pointed to by dfd or to our chroot (if dfd is AT_FDCWD).
+ */
+static int vfs_fsinfo_mount(int dfd, const char __user *filename,
+			    struct fsinfo_context *ctx)
+{
+	struct path path;
+	struct fd f = {};
+	char *name;
+	long mnt_id;
+	int ret;
+
+	if (!filename)
+		return -EINVAL;
+
+	name = strndup_user(filename, 32);
+	if (IS_ERR(name))
+		return PTR_ERR(name);
+	ret = kstrtoul(name, 0, &mnt_id);
+	if (ret < 0)
+		goto out_name;
+	if (mnt_id > INT_MAX)
+		goto out_name;
+
+	if (dfd != AT_FDCWD) {
+		ret = -EBADF;
+		f = fdget_raw(dfd);
+		if (!f.file)
+			goto out_name;
+	}
+
+	ret = lookup_mount_object(f.file ? &f.file->f_path : NULL,
+				  mnt_id, &path);
+	if (ret < 0)
+		goto out_fd;
+
+	ret = vfs_fsinfo(&path, ctx);
+	path_put(&path);
+out_fd:
+	fdput(f);
+out_name:
+	kfree(name);
+	return ret;
+}
+
 /**
  * sys_fsinfo - System call to get filesystem information
  * @dfd: Base directory to pathwalk from or fd referring to filesystem.
@@ -624,6 +674,9 @@ SYSCALL_DEFINE6(fsinfo,
 			return -EINVAL;
 		ret = vfs_fsinfo_fd(dfd, &ctx);
 		break;
+	case FSINFO_FLAGS_QUERY_MOUNT:
+		ret = vfs_fsinfo_mount(dfd, pathname, &ctx);
+		break;
 	default:
 		return -EINVAL;
 	}
diff --git a/fs/internal.h b/fs/internal.h
index 6f2cc77bf38d..abbd5299e7dc 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -91,6 +91,7 @@ extern int __mnt_want_write_file(struct file *);
 extern void __mnt_drop_write_file(struct file *);
 
 extern void dissolve_on_fput(struct vfsmount *);
+extern int lookup_mount_object(struct path *, int, struct path *);
 extern int fsinfo_generic_mount_source(struct path *, struct fsinfo_context *);
 
 /*
diff --git a/fs/namespace.c b/fs/namespace.c
index e26e06447993..f33cec5fe885 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -64,7 +64,7 @@ static int __init set_mphash_entries(char *str)
 __setup("mphash_entries=", set_mphash_entries);
 
 static u64 event;
-static DEFINE_IDA(mnt_id_ida);
+static DEFINE_IDR(mnt_id_ida);
 static DEFINE_IDA(mnt_group_ida);
 
 static struct hlist_head *mount_hashtable __read_mostly;
@@ -105,17 +105,27 @@ static inline struct hlist_head *mp_hash(struct dentry *dentry)
 
 static int mnt_alloc_id(struct mount *mnt)
 {
-	int res = ida_alloc(&mnt_id_ida, GFP_KERNEL);
+	int res;
 
+	/* Allocate an ID, but don't set the pointer back to the mount until
+	 * later, as once we do that, we have to follow RCU protocols to get
+	 * rid of the mount struct.
+	 */
+	res = idr_alloc(&mnt_id_ida, NULL, 0, INT_MAX, GFP_KERNEL);
 	if (res < 0)
 		return res;
 	mnt->mnt_id = res;
 	return 0;
 }
 
+static void mnt_publish_id(struct mount *mnt)
+{
+	idr_replace(&mnt_id_ida, mnt, mnt->mnt_id);
+}
+
 static void mnt_free_id(struct mount *mnt)
 {
-	ida_free(&mnt_id_ida, mnt->mnt_id);
+	idr_remove(&mnt_id_ida, mnt->mnt_id);
 }
 
 /*
@@ -959,6 +969,7 @@ struct vfsmount *vfs_create_mount(struct fs_context *fc)
 	lock_mount_hash();
 	list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts);
 	unlock_mount_hash();
+	mnt_publish_id(mnt);
 	return &mnt->mnt;
 }
 EXPORT_SYMBOL(vfs_create_mount);
@@ -1052,6 +1063,7 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
 	lock_mount_hash();
 	list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
 	unlock_mount_hash();
+	mnt_publish_id(mnt);
 
 	if ((flag & CL_SLAVE) ||
 	    ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
@@ -4035,4 +4047,103 @@ int fsinfo_generic_mount_source(struct path *path, struct fsinfo_context *ctx)
 	return m.count;
 }
 
+/*
+ * See if one path point connects directly to another by ancestral relationship
+ * across mountpoints.  Must call with the RCU read lock held.
+ */
+static bool are_paths_connected(struct path *ancestor, struct path *to_check)
+{
+	struct mount *mnt, *parent;
+	struct path cursor;
+	unsigned seq;
+	bool connected;
+
+	seq = 0;
+restart:
+	cursor = *to_check;
+
+	read_seqbegin_or_lock(&rename_lock, &seq);
+	while (cursor.mnt != ancestor->mnt) {
+		mnt = real_mount(cursor.mnt);
+		parent = READ_ONCE(mnt->mnt_parent);
+		if (mnt == parent)
+			goto failed;
+		cursor.dentry = READ_ONCE(mnt->mnt_mountpoint);
+		cursor.mnt = &parent->mnt;
+	}
+
+	while (cursor.dentry != ancestor->dentry) {
+		if (cursor.dentry == cursor.mnt->mnt_root ||
+		    IS_ROOT(cursor.dentry))
+			goto failed;
+		cursor.dentry = READ_ONCE(cursor.dentry->d_parent);
+	}
+
+	connected = true;
+out:
+	done_seqretry(&rename_lock, seq);
+	return connected;
+
+failed:
+	if (need_seqretry(&rename_lock, seq)) {
+		seq = 1;
+		goto restart;
+	}
+	connected = false;
+	goto out;
+}
+
+/**
+ * lookup_mount_object - Look up a vfsmount object by ID
+ * @root: The mount root must connect backwards to this point (or chroot if NULL).
+ * @id: The ID of the mountpoint.
+ * @_mntpt: Where to return the resulting mountpoint path.
+ *
+ * Look up the root of the mount with the corresponding ID.  This is only
+ * permitted if that mount connects directly to the specified root/chroot.
+ */
+int lookup_mount_object(struct path *root, int mnt_id, struct path *_mntpt)
+{
+	struct mount *mnt;
+	struct path stop, mntpt = {};
+	int ret = -EPERM;
+
+	if (!root)
+		get_fs_root(current->fs, &stop);
+	else
+		stop = *root;
+
+	rcu_read_lock();
+	lock_mount_hash();
+	mnt = idr_find(&mnt_id_ida, mnt_id);
+	if (!mnt)
+		goto out_unlock_mh;
+	if (mnt->mnt.mnt_flags & (MNT_SYNC_UMOUNT | MNT_UMOUNT | MNT_DOOMED))
+		goto out_unlock_mh;
+	if (mnt_get_count(mnt) == 0)
+		goto out_unlock_mh;
+	mnt_add_count(mnt, 1);
+	mntpt.mnt = &mnt->mnt;
+	mntpt.dentry = dget(mnt->mnt.mnt_root);
+	unlock_mount_hash();
+
+	if (are_paths_connected(&stop, &mntpt)) {
+		*_mntpt = mntpt;
+		mntpt.mnt = NULL;
+		mntpt.dentry = NULL;
+		ret = 0;
+	}
+
+out_unlock:
+	rcu_read_unlock();
+	if (!root)
+		path_put(&stop);
+	path_put(&mntpt);
+	return ret;
+
+out_unlock_mh:
+	unlock_mount_hash();
+	goto out_unlock;
+}
+
 #endif /* CONFIG_FSINFO */
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 3bb4fa67f8c8..0ae050a5227b 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -44,6 +44,7 @@ struct fsinfo_params {
 #define FSINFO_FLAGS_QUERY_MASK	0x0007 /* What object should fsinfo() query? */
 #define FSINFO_FLAGS_QUERY_PATH	0x0000 /* - path, specified by dirfd,pathname,AT_EMPTY_PATH */
 #define FSINFO_FLAGS_QUERY_FD	0x0001 /* - fd specified by dirfd */
+#define FSINFO_FLAGS_QUERY_MOUNT 0x0002	/* - mount object (path=>mount_id, dirfd=>subtree) */
 	__u32	request;	/* ID of requested attribute */
 	__u32	Nth;		/* Instance of it (some may have multiple) */
 	__u32	Mth;		/* Subinstance of Nth instance */
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index 692639ae6d1c..90fd95c46f2e 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -579,7 +579,7 @@ int main(int argc, char **argv)
 	bool meta = false;
 	int raw = 0, opt, Nth, Mth;
 
-	while ((opt = getopt(argc, argv, "Madlr"))) {
+	while ((opt = getopt(argc, argv, "Madmlr"))) {
 		switch (opt) {
 		case 'M':
 			meta = true;
@@ -595,6 +595,10 @@ int main(int argc, char **argv)
 			params.at_flags &= ~AT_SYMLINK_NOFOLLOW;
 			params.flags = FSINFO_FLAGS_QUERY_PATH;
 			continue;
+		case 'm':
+			params.resolve_flags = 0;
+			params.flags = FSINFO_FLAGS_QUERY_MOUNT;
+			continue;
 		case 'r':
 			raw = 1;
 			continue;
@@ -607,6 +611,7 @@ int main(int argc, char **argv)
 
 	if (argc != 1) {
 		printf("Format: test-fsinfo [-Madlr] <path>\n");
+		printf("Format: test-fsinfo [-Mdr] -m <mnt_id>\n");
 		exit(2);
 	}
 



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 05/13] fsinfo: Add a uniquifier ID to struct mount [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (3 preceding siblings ...)
  2020-03-18 15:08 ` [PATCH 04/13] fsinfo: Allow fsinfo() to look up a mount object by ID " David Howells
@ 2020-03-18 15:08 ` David Howells
  2020-03-18 15:09 ` [PATCH 06/13] fsinfo: Allow mount information to be queried " David Howells
                   ` (9 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:08 UTC (permalink / raw)
  To: torvalds, viro
  Cc: dhowells, raven, mszeredi, christian, jannh, darrick.wong, kzak,
	jlayton, linux-api, linux-fsdevel, linux-security-module,
	linux-kernel

Add a uniquifier ID to struct mount that is effectively unique over the
kernel lifetime to deal around mnt_id values being reused.  This can then
be exported through fsinfo() to allow detection of replacement mounts that
happen to end up with the same mount ID.

The normal mount handle is still used for referring to a particular mount.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/mount.h     |    3 +++
 fs/namespace.c |    3 +++
 2 files changed, 6 insertions(+)

diff --git a/fs/mount.h b/fs/mount.h
index 9a49ea1e7365..063f41bc2e93 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -73,6 +73,9 @@ struct mount {
 	int mnt_expiry_mark;		/* true if marked for expiry */
 	struct hlist_head mnt_pins;
 	struct hlist_head mnt_stuck_children;
+#ifdef CONFIG_FSINFO
+	u64	mnt_unique_id;		/* ID unique over lifetime of kernel */
+#endif
 #ifdef CONFIG_MOUNT_NOTIFICATIONS
 	atomic_t mnt_topology_changes;	/* Number of topology changes applied */
 	atomic_t mnt_attr_changes;	/* Number of attribute changes applied */
diff --git a/fs/namespace.c b/fs/namespace.c
index f33cec5fe885..54e8eb93fdd6 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -115,6 +115,9 @@ static int mnt_alloc_id(struct mount *mnt)
 	if (res < 0)
 		return res;
 	mnt->mnt_id = res;
+#ifdef CONFIG_FSINFO
+	vfs_generate_unique_id(&mnt->mnt_unique_id);
+#endif
 	return 0;
 }
 



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 06/13] fsinfo: Allow mount information to be queried [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (4 preceding siblings ...)
  2020-03-18 15:08 ` [PATCH 05/13] fsinfo: Add a uniquifier ID to struct mount " David Howells
@ 2020-03-18 15:09 ` David Howells
  2020-03-18 15:09 ` [PATCH 07/13] fsinfo: Allow mount topology and propagation info to be retrieved " David Howells
                   ` (8 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:09 UTC (permalink / raw)
  To: torvalds, viro
  Cc: dhowells, raven, mszeredi, christian, jannh, darrick.wong, kzak,
	jlayton, linux-api, linux-fsdevel, linux-security-module,
	linux-kernel

Allow mount information, including information about a mount object to be
queried with the fsinfo() system call.  Setting FSINFO_FLAGS_QUERY_MOUNT
allows overlapping mounts to be queried by indicating that the syscall
should interpret the pathname as a number indicating the mount ID.

To this end, a number of fsinfo() attributes are provided:

 (1) FSINFO_ATTR_MOUNT_INFO.

     This is a structure providing information about a mount, including:

	- Mount ID (can be used with FSINFO_FLAGS_QUERY_MOUNT).
	- Mount uniquifier ID.
	- Mount attributes (eg. R/O, NOEXEC).
	- Mount change/notification counters.
	- Superblock ID.
	- Superblock change/notification counters.

 (2) FSINFO_ATTR_MOUNT_PATH.

     This a string providing information about a bind mount relative the
     the root that was bound off, though it may get overridden by the
     filesystem (NFS unconditionally sets it to "/", for example).

 (3) FSINFO_ATTR_MOUNT_POINT.

     This is a string indicating the name of the mountpoint within the
     parent mount, limited to the parent's mounted root and the chroot.

 (4) FSINFO_ATTR_MOUNT_POINT_FULL.

     This is a string indicating the full path of the mountpoint, limited to
     the chroot.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/d_path.c                 |    2 -
 fs/fsinfo.c                 |   13 +++++
 fs/internal.h               |    9 +++
 fs/namespace.c              |  111 +++++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/fsinfo.h |   17 +++++++
 samples/vfs/test-fsinfo.c   |   16 ++++++
 6 files changed, 167 insertions(+), 1 deletion(-)

diff --git a/fs/d_path.c b/fs/d_path.c
index 0f1fc1743302..4c203f64e45e 100644
--- a/fs/d_path.c
+++ b/fs/d_path.c
@@ -229,7 +229,7 @@ static int prepend_unreachable(char **buffer, int *buflen)
 	return prepend(buffer, buflen, "(unreachable)", 13);
 }
 
-static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
+void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
 {
 	unsigned seq;
 
diff --git a/fs/fsinfo.c b/fs/fsinfo.c
index 3250b9ff2905..a08b172f71d2 100644
--- a/fs/fsinfo.c
+++ b/fs/fsinfo.c
@@ -236,6 +236,14 @@ static int fsinfo_generic_seq_read(struct path *path, struct fsinfo_context *ctx
 			ret = sb->s_op->show_options(&m, path->mnt->mnt_root);
 		break;
 
+	case FSINFO_ATTR_MOUNT_PATH:
+		if (sb->s_op->show_path) {
+			ret = sb->s_op->show_path(&m, path->mnt->mnt_root);
+		} else {
+			seq_dentry(&m, path->mnt->mnt_root, " \t\n\\");
+		}
+		break;
+
 	case FSINFO_ATTR_FS_STATISTICS:
 		if (sb->s_op->show_stats)
 			ret = sb->s_op->show_stats(&m, path->mnt->mnt_root);
@@ -270,6 +278,11 @@ static const struct fsinfo_attribute fsinfo_common_attributes[] = {
 
 	FSINFO_LIST	(FSINFO_ATTR_FSINFO_ATTRIBUTES,	(void *)123UL),
 	FSINFO_VSTRUCT_N(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, (void *)123UL),
+
+	FSINFO_VSTRUCT	(FSINFO_ATTR_MOUNT_INFO,	fsinfo_generic_mount_info),
+	FSINFO_STRING	(FSINFO_ATTR_MOUNT_PATH,	fsinfo_generic_seq_read),
+	FSINFO_STRING	(FSINFO_ATTR_MOUNT_POINT,	fsinfo_generic_mount_point),
+	FSINFO_STRING	(FSINFO_ATTR_MOUNT_POINT_FULL,	fsinfo_generic_mount_point_full),
 	{}
 };
 
diff --git a/fs/internal.h b/fs/internal.h
index abbd5299e7dc..68e300a1e9a3 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -15,6 +15,7 @@ struct mount;
 struct shrink_control;
 struct fs_context;
 struct user_namespace;
+struct fsinfo_context;
 
 /*
  * block_dev.c
@@ -47,6 +48,11 @@ extern int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
  */
 extern void __init chrdev_init(void);
 
+/*
+ * d_path.c
+ */
+extern void get_fs_root_rcu(struct fs_struct *fs, struct path *root);
+
 /*
  * fs_context.c
  */
@@ -93,6 +99,9 @@ extern void __mnt_drop_write_file(struct file *);
 extern void dissolve_on_fput(struct vfsmount *);
 extern int lookup_mount_object(struct path *, int, struct path *);
 extern int fsinfo_generic_mount_source(struct path *, struct fsinfo_context *);
+extern int fsinfo_generic_mount_info(struct path *, struct fsinfo_context *);
+extern int fsinfo_generic_mount_point(struct path *, struct fsinfo_context *);
+extern int fsinfo_generic_mount_point_full(struct path *, struct fsinfo_context *);
 
 /*
  * fs_struct.c
diff --git a/fs/namespace.c b/fs/namespace.c
index 54e8eb93fdd6..483fbbde5c28 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4149,4 +4149,115 @@ int lookup_mount_object(struct path *root, int mnt_id, struct path *_mntpt)
 	goto out_unlock;
 }
 
+/*
+ * Retrieve information about the nominated mount.
+ */
+int fsinfo_generic_mount_info(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_mount_info *p = ctx->buffer;
+	struct super_block *sb;
+	struct mount *m;
+	unsigned int flags;
+
+	m = real_mount(path->mnt);
+	sb = m->mnt.mnt_sb;
+
+	p->sb_unique_id		= sb->s_unique_id;
+	p->mnt_unique_id	= m->mnt_unique_id;
+	p->mnt_id		= m->mnt_id;
+
+	flags = READ_ONCE(m->mnt.mnt_flags);
+	if (flags & MNT_READONLY)
+		p->attr |= MOUNT_ATTR_RDONLY;
+	if (flags & MNT_NOSUID)
+		p->attr |= MOUNT_ATTR_NOSUID;
+	if (flags & MNT_NODEV)
+		p->attr |= MOUNT_ATTR_NODEV;
+	if (flags & MNT_NOEXEC)
+		p->attr |= MOUNT_ATTR_NOEXEC;
+	if (flags & MNT_NODIRATIME)
+		p->attr |= MOUNT_ATTR_NODIRATIME;
+
+	if (flags & MNT_NOATIME)
+		p->attr |= MOUNT_ATTR_NOATIME;
+	else if (flags & MNT_RELATIME)
+		p->attr |= MOUNT_ATTR_RELATIME;
+	else
+		p->attr |= MOUNT_ATTR_STRICTATIME;
+	return sizeof(*p);
+}
+
+/*
+ * Return the path of this mount relative to its parent and clipped to
+ * the current chroot.
+ */
+int fsinfo_generic_mount_point(struct path *path, struct fsinfo_context *ctx)
+{
+	struct mountpoint *mp;
+	struct mount *m, *parent;
+	struct path mountpoint, root;
+	void *p;
+
+	rcu_read_lock();
+
+	m = real_mount(path->mnt);
+	parent = m->mnt_parent;
+	if (parent == m)
+		goto skip;
+	mp = READ_ONCE(m->mnt_mp);
+	if (mp)
+		goto found;
+skip:
+	rcu_read_unlock();
+	return -ENODATA;
+
+found:
+	mountpoint.mnt = &parent->mnt;
+	mountpoint.dentry = READ_ONCE(mp->m_dentry);
+
+	get_fs_root_rcu(current->fs, &root);
+	if (path->mnt == root.mnt) {
+		rcu_read_unlock();
+		return fsinfo_string("/", ctx);
+	}
+
+	if (root.mnt != &parent->mnt) {
+		root.mnt = &parent->mnt;
+		root.dentry = parent->mnt.mnt_root;
+	}
+
+	p = __d_path(&mountpoint, &root, ctx->buffer, ctx->buf_size);
+	rcu_read_unlock();
+
+	if (IS_ERR(p))
+		return PTR_ERR(p);
+	if (!p)
+		return -EPERM;
+
+	ctx->skip = p - ctx->buffer;
+	return (ctx->buffer + ctx->buf_size) - p;
+}
+
+/*
+ * Return the path of this mount from the current chroot.
+ */
+int fsinfo_generic_mount_point_full(struct path *path, struct fsinfo_context *ctx)
+{
+	struct path root;
+	void *p;
+
+	rcu_read_lock();
+	get_fs_root_rcu(current->fs, &root);
+	p = __d_path(path, &root, ctx->buffer, ctx->buf_size);
+	rcu_read_unlock();
+
+	if (IS_ERR(p))
+		return PTR_ERR(p);
+	if (!p)
+		return -EPERM;
+
+	ctx->skip = p - ctx->buffer;
+	return (ctx->buffer + ctx->buf_size) - p;
+}
+
 #endif /* CONFIG_FSINFO */
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 0ae050a5227b..df96301dc612 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -31,6 +31,11 @@
 #define FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO 0x100	/* Information about attr N (for path) */
 #define FSINFO_ATTR_FSINFO_ATTRIBUTES	0x101	/* List of supported attrs (for path) */
 
+#define FSINFO_ATTR_MOUNT_INFO		0x200	/* Mount object information */
+#define FSINFO_ATTR_MOUNT_PATH		0x201	/* Bind mount/superblock path (string) */
+#define FSINFO_ATTR_MOUNT_POINT		0x202	/* Relative path of mount in parent (string) */
+#define FSINFO_ATTR_MOUNT_POINT_FULL	0x203	/* Absolute path of mount (string) */
+
 /*
  * Optional fsinfo() parameter structure.
  *
@@ -85,6 +90,18 @@ struct fsinfo_u128 {
 #endif
 };
 
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_MOUNT_INFO).
+ */
+struct fsinfo_mount_info {
+	__u64	sb_unique_id;		/* Kernel-lifetime unique superblock ID */
+	__u64	mnt_unique_id;		/* Kernel-lifetime unique mount ID */
+	__u32	mnt_id;			/* Mount identifier (use with AT_FSINFO_MOUNTID_PATH) */
+	__u32	attr;			/* MOUNT_ATTR_* flags */
+};
+
+#define FSINFO_ATTR_MOUNT_INFO__STRUCT struct fsinfo_mount_info
+
 /*
  * Information struct for fsinfo(FSINFO_ATTR_STATFS).
  * - This gives extended filesystem information.
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index 90fd95c46f2e..b23d0d56988f 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -288,6 +288,17 @@ static void dump_fsinfo_generic_volume_uuid(void *reply, unsigned int size)
 	       f->uuid[14], f->uuid[15]);
 }
 
+static void dump_fsinfo_generic_mount_info(void *reply, unsigned int size)
+{
+	struct fsinfo_mount_info *r = reply;
+
+	printf("\n");
+	printf("\tsb_uniq : %llx\n", (unsigned long long)r->sb_unique_id);
+	printf("\tmnt_uniq: %llx\n", (unsigned long long)r->mnt_unique_id);
+	printf("\tmnt_id  : %x\n", r->mnt_id);
+	printf("\tattr    : %x\n", r->attr);
+}
+
 static void dump_string(void *reply, unsigned int size)
 {
 	char *s = reply, *p;
@@ -364,6 +375,11 @@ static const struct fsinfo_attribute fsinfo_attributes[] = {
 
 	FSINFO_VSTRUCT_N(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, fsinfo_meta_attribute_info),
 	FSINFO_LIST	(FSINFO_ATTR_FSINFO_ATTRIBUTES,	fsinfo_meta_attributes),
+
+	FSINFO_VSTRUCT	(FSINFO_ATTR_MOUNT_INFO,	fsinfo_generic_mount_info),
+	FSINFO_STRING	(FSINFO_ATTR_MOUNT_PATH,	string),
+	FSINFO_STRING_N	(FSINFO_ATTR_MOUNT_POINT,	string),
+	FSINFO_STRING_N	(FSINFO_ATTR_MOUNT_POINT_FULL,	string),
 	{}
 };
 



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 07/13] fsinfo: Allow mount topology and propagation info to be retrieved [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (5 preceding siblings ...)
  2020-03-18 15:09 ` [PATCH 06/13] fsinfo: Allow mount information to be queried " David Howells
@ 2020-03-18 15:09 ` David Howells
  2020-03-18 15:09 ` [PATCH 08/13] fsinfo: Provide notification overrun handling support " David Howells
                   ` (7 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:09 UTC (permalink / raw)
  To: torvalds, viro
  Cc: dhowells, raven, mszeredi, christian, jannh, darrick.wong, kzak,
	jlayton, linux-api, linux-fsdevel, linux-security-module,
	linux-kernel

Add a couple of attributes to allow information about the mount topology
and propagation to be retrieved:

 (1) FSINFO_ATTR_MOUNT_TOPOLOGY.

     Information about a mount's parentage in the mount topology tree and
     its propagation attributes.

     This has to be collected with the VFS namespace lock held, so it's
     separate from FSINFO_ATTR_MOUNT_INFO.  The topology change counter
     that a subsequent patch will export can be used to work out from the
     cheaper _INFO attribute as to whether the more expensive _TOPOLOGY
     attribute needs requerying.

     MOUNT_PROPAGATION_* flags are added to linux/mount.h for UAPI
     consumption.  At some point a mount_setattr() system call needs to be
     added.

 (2) FSINFO_ATTR_MOUNT_CHILDREN.

     Information about a mount's children in the mount topology tree.

     This is formatted as an array of structures, one for each child and
     capped with one for the argument mount (checked after listing all the
     children).  Each element contains the static IDs of the respective
     mount object along with a sum of its change attributes.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/fsinfo.c                 |    2 +
 fs/internal.h               |    2 +
 fs/namespace.c              |   91 +++++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/fsinfo.h |   27 +++++++++++++
 include/uapi/linux/mount.h  |   10 ++++-
 samples/vfs/test-fsinfo.c   |   38 ++++++++++++++++++
 6 files changed, 169 insertions(+), 1 deletion(-)

diff --git a/fs/fsinfo.c b/fs/fsinfo.c
index a08b172f71d2..eccea3b1579a 100644
--- a/fs/fsinfo.c
+++ b/fs/fsinfo.c
@@ -280,9 +280,11 @@ static const struct fsinfo_attribute fsinfo_common_attributes[] = {
 	FSINFO_VSTRUCT_N(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, (void *)123UL),
 
 	FSINFO_VSTRUCT	(FSINFO_ATTR_MOUNT_INFO,	fsinfo_generic_mount_info),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_MOUNT_TOPOLOGY,	fsinfo_generic_mount_topology),
 	FSINFO_STRING	(FSINFO_ATTR_MOUNT_PATH,	fsinfo_generic_seq_read),
 	FSINFO_STRING	(FSINFO_ATTR_MOUNT_POINT,	fsinfo_generic_mount_point),
 	FSINFO_STRING	(FSINFO_ATTR_MOUNT_POINT_FULL,	fsinfo_generic_mount_point_full),
+	FSINFO_LIST	(FSINFO_ATTR_MOUNT_CHILDREN,	fsinfo_generic_mount_children),
 	{}
 };
 
diff --git a/fs/internal.h b/fs/internal.h
index 68e300a1e9a3..6a30320ea2f8 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -100,8 +100,10 @@ extern void dissolve_on_fput(struct vfsmount *);
 extern int lookup_mount_object(struct path *, int, struct path *);
 extern int fsinfo_generic_mount_source(struct path *, struct fsinfo_context *);
 extern int fsinfo_generic_mount_info(struct path *, struct fsinfo_context *);
+extern int fsinfo_generic_mount_topology(struct path *, struct fsinfo_context *);
 extern int fsinfo_generic_mount_point(struct path *, struct fsinfo_context *);
 extern int fsinfo_generic_mount_point_full(struct path *, struct fsinfo_context *);
+extern int fsinfo_generic_mount_children(struct path *, struct fsinfo_context *);
 
 /*
  * fs_struct.c
diff --git a/fs/namespace.c b/fs/namespace.c
index 483fbbde5c28..61b110149fc5 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4187,6 +4187,53 @@ int fsinfo_generic_mount_info(struct path *path, struct fsinfo_context *ctx)
 	return sizeof(*p);
 }
 
+/*
+ * Retrieve information about the topology at the nominated mount and
+ * its propogation attributes.
+ */
+int fsinfo_generic_mount_topology(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_mount_topology *p = ctx->buffer;
+	struct mount *m;
+	struct path root;
+
+	get_fs_root(current->fs, &root);
+
+	namespace_lock();
+
+	m = real_mount(path->mnt);
+
+	p->parent_id = m->mnt_parent->mnt_id;
+
+	if (path->mnt == root.mnt) {
+		p->parent_id = m->mnt_id;
+	} else {
+		rcu_read_lock();
+		if (!are_paths_connected(&root, path))
+			p->parent_id = m->mnt_id;
+		rcu_read_unlock();
+	}
+
+	if (IS_MNT_SHARED(m)) {
+		p->group_id = m->mnt_group_id;
+		p->propagation |= MOUNT_PROPAGATION_SHARED;
+	}
+	if (IS_MNT_SLAVE(m)) {
+		int master = m->mnt_master->mnt_group_id;
+		int dom = get_dominating_id(m, &root);
+		p->master_id = master;
+		if (dom && dom != master)
+			p->from_id = dom;
+		p->propagation |= MOUNT_PROPAGATION_SLAVE;
+	}
+	if (IS_MNT_UNBINDABLE(m))
+		p->propagation |= MOUNT_PROPAGATION_UNBINDABLE;
+
+	namespace_unlock();
+	path_put(&root);
+	return sizeof(*p);
+}
+
 /*
  * Return the path of this mount relative to its parent and clipped to
  * the current chroot.
@@ -4260,4 +4307,48 @@ int fsinfo_generic_mount_point_full(struct path *path, struct fsinfo_context *ct
 	return (ctx->buffer + ctx->buf_size) - p;
 }
 
+/*
+ * Store a mount record into the fsinfo buffer.
+ */
+static void fsinfo_store_mount(struct fsinfo_context *ctx, const struct mount *p)
+{
+	struct fsinfo_mount_child record = {};
+	unsigned int usage = ctx->usage;
+
+	if (ctx->usage >= INT_MAX)
+		return;
+	ctx->usage = usage + sizeof(record);
+
+	if (ctx->buffer && ctx->usage <= ctx->buf_size) {
+		record.mnt_unique_id	= p->mnt_unique_id;
+		record.mnt_id		= p->mnt_id;
+		memcpy(ctx->buffer + usage, &record, sizeof(record));
+	}
+}
+
+/*
+ * Return information about the submounts relative to path.
+ */
+int fsinfo_generic_mount_children(struct path *path, struct fsinfo_context *ctx)
+{
+	struct mount *m, *child;
+
+	m = real_mount(path->mnt);
+
+	read_seqlock_excl(&mount_lock);
+
+	list_for_each_entry_rcu(child, &m->mnt_mounts, mnt_child) {
+		if (child->mnt_parent != m)
+			continue;
+		fsinfo_store_mount(ctx, child);
+	}
+
+	/* End the list with a copy of the parameter mount's details so that
+	 * userspace can quickly check for changes.
+	 */
+	fsinfo_store_mount(ctx, m);
+	read_sequnlock_excl(&mount_lock);
+	return ctx->usage;
+}
+
 #endif /* CONFIG_FSINFO */
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index df96301dc612..9410e320d824 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -35,6 +35,8 @@
 #define FSINFO_ATTR_MOUNT_PATH		0x201	/* Bind mount/superblock path (string) */
 #define FSINFO_ATTR_MOUNT_POINT		0x202	/* Relative path of mount in parent (string) */
 #define FSINFO_ATTR_MOUNT_POINT_FULL	0x203	/* Absolute path of mount (string) */
+#define FSINFO_ATTR_MOUNT_TOPOLOGY	0x204	/* Mount object topology */
+#define FSINFO_ATTR_MOUNT_CHILDREN	0x205	/* Children of this mount (list) */
 
 /*
  * Optional fsinfo() parameter structure.
@@ -102,6 +104,31 @@ struct fsinfo_mount_info {
 
 #define FSINFO_ATTR_MOUNT_INFO__STRUCT struct fsinfo_mount_info
 
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_MOUNT_TOPOLOGY).
+ */
+struct fsinfo_mount_topology {
+	__u32	parent_id;		/* Parent mount identifier */
+	__u32	group_id;		/* Mount group ID */
+	__u32	master_id;		/* Slave master group ID */
+	__u32	from_id;		/* Slave propagated from ID */
+	__u32	propagation;		/* MOUNT_PROPAGATION_* flags */
+};
+
+#define FSINFO_ATTR_MOUNT_TOPOLOGY__STRUCT struct fsinfo_mount_topology
+
+/*
+ * Information struct element for fsinfo(FSINFO_ATTR_MOUNT_CHILDREN).
+ * - An extra element is placed on the end representing the parent mount.
+ */
+struct fsinfo_mount_child {
+	__u64	mnt_unique_id;		/* Kernel-lifetime unique mount ID */
+	__u32	mnt_id;			/* Mount identifier (use with AT_FSINFO_MOUNTID_PATH) */
+	__u32	__padding[1];
+};
+
+#define FSINFO_ATTR_MOUNT_CHILDREN__STRUCT struct fsinfo_mount_child
+
 /*
  * Information struct for fsinfo(FSINFO_ATTR_STATFS).
  * - This gives extended filesystem information.
diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
index 96a0240f23fe..c18b21de3fdd 100644
--- a/include/uapi/linux/mount.h
+++ b/include/uapi/linux/mount.h
@@ -105,7 +105,7 @@ enum fsconfig_command {
 #define FSMOUNT_CLOEXEC		0x00000001
 
 /*
- * Mount attributes.
+ * Mount object attributes (these are separate to filesystem attributes).
  */
 #define MOUNT_ATTR_RDONLY	0x00000001 /* Mount read-only */
 #define MOUNT_ATTR_NOSUID	0x00000002 /* Ignore suid and sgid bits */
@@ -117,4 +117,12 @@ enum fsconfig_command {
 #define MOUNT_ATTR_STRICTATIME	0x00000020 /* - Always perform atime updates */
 #define MOUNT_ATTR_NODIRATIME	0x00000080 /* Do not update directory access times */
 
+/*
+ * Mount object propagation attributes.
+ */
+#define MOUNT_PROPAGATION_UNBINDABLE	0x00000001 /* Mount is unbindable */
+#define MOUNT_PROPAGATION_SLAVE		0x00000002 /* Mount is slave */
+#define MOUNT_PROPAGATION_PRIVATE	0x00000000 /* Mount is private (ie. not shared) */
+#define MOUNT_PROPAGATION_SHARED	0x00000004 /* Mount is shared */
+
 #endif /* _UAPI_LINUX_MOUNT_H */
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index b23d0d56988f..762ab4517cd9 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -299,6 +299,42 @@ static void dump_fsinfo_generic_mount_info(void *reply, unsigned int size)
 	printf("\tattr    : %x\n", r->attr);
 }
 
+static void dump_fsinfo_generic_mount_topology(void *reply, unsigned int size)
+{
+	struct fsinfo_mount_topology *r = reply;
+
+	printf("\n");
+	printf("\tparent  : %x\n", r->parent_id);
+	printf("\tgroup   : %x\n", r->group_id);
+	printf("\tmaster  : %x\n", r->master_id);
+	printf("\tfrom    : %x\n", r->from_id);
+	printf("\tpropag  : %x\n", r->propagation);
+}
+
+static void dump_fsinfo_generic_mount_children(void *reply, unsigned int size)
+{
+	struct fsinfo_mount_child *r = reply;
+	ssize_t mplen;
+	char path[32], *mp;
+
+	struct fsinfo_params params = {
+		.flags		= FSINFO_FLAGS_QUERY_MOUNT,
+		.request	= FSINFO_ATTR_MOUNT_POINT,
+	};
+
+	if (!list_last) {
+		sprintf(path, "%u", r->mnt_id);
+		mplen = get_fsinfo(path, "FSINFO_ATTR_MOUNT_POINT", &params, (void **)&mp);
+		if (mplen < 0)
+			mp = "-";
+	} else {
+		mp = "<this>";
+	}
+
+	printf("%8x %16llx %s\n",
+	       r->mnt_id, (unsigned long long)r->mnt_unique_id, mp);
+}
+
 static void dump_string(void *reply, unsigned int size)
 {
 	char *s = reply, *p;
@@ -377,9 +413,11 @@ static const struct fsinfo_attribute fsinfo_attributes[] = {
 	FSINFO_LIST	(FSINFO_ATTR_FSINFO_ATTRIBUTES,	fsinfo_meta_attributes),
 
 	FSINFO_VSTRUCT	(FSINFO_ATTR_MOUNT_INFO,	fsinfo_generic_mount_info),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_MOUNT_TOPOLOGY,	fsinfo_generic_mount_topology),
 	FSINFO_STRING	(FSINFO_ATTR_MOUNT_PATH,	string),
 	FSINFO_STRING_N	(FSINFO_ATTR_MOUNT_POINT,	string),
 	FSINFO_STRING_N	(FSINFO_ATTR_MOUNT_POINT_FULL,	string),
+	FSINFO_LIST	(FSINFO_ATTR_MOUNT_CHILDREN,	fsinfo_generic_mount_children),
 	{}
 };
 



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 08/13] fsinfo: Provide notification overrun handling support [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (6 preceding siblings ...)
  2020-03-18 15:09 ` [PATCH 07/13] fsinfo: Allow mount topology and propagation info to be retrieved " David Howells
@ 2020-03-18 15:09 ` David Howells
  2020-03-18 15:09 ` [PATCH 09/13] fsinfo: sample: Mount listing program " David Howells
                   ` (6 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:09 UTC (permalink / raw)
  To: torvalds, viro
  Cc: dhowells, raven, mszeredi, christian, jannh, darrick.wong, kzak,
	jlayton, linux-api, linux-fsdevel, linux-security-module,
	linux-kernel

Provide support for the handling of an overrun in a watch queue.  In the
event that an overrun occurs, the watcher needs to be able to find out what
it was that they missed.  To this end, previous patches added event
counters to the superblock and mount object structures.

To make them accessible, they can be accessed using fsinfo() and the
FSINFO_ATTR_MOUNT_INFO attribute.

	struct fsinfo_mount_info {
		__u64	mnt_unique_id;
		__u32	sb_changes;
		__u32	sb_notifications;
		__u32	mnt_attr_changes;
		__u32	mnt_topology_changes;
		__u32	mnt_subtree_notifications;
	...
	};

There's a uniquifier and five event counters:

 (1) mnt_unique_id - This is an effectively non-repeating ID given to each
     mount object on creation.  This allows the caller to check that the
     mount ID didn't get reused (the 32-bit mount ID is more efficient to
     look up).

 (2) sb_changes - Count of superblock configuration changes.

 (3) sb_notifications - Count of other superblock notifications (errors,
     quota overruns, etc.).

 (4) mnt_attr_changes - Count of attribute changes on a mount object.

 (5) mnt_topology_changes - Count of alterations to the mount tree that
     affected this node.

 (6) mnt_subtree_notifications - Count of mount object event notifications
     that were generated in the subtree rooted at this node.  This excludes
     events generated on this node itself and does not include superblock
     events.

The counters are also accessible through the FSINFO_ATTR_MOUNT_CHILDREN
attribute, where a list of all the children of a mount can be scanned.  The
record returned for each child includes the sum of the above five counters
for that child.  An additional record is added at the end for the queried
object and that also includes the sum of its five counters

The mnt_topology_changes counter is also included in
FSINFO_ATTR_MOUNT_TOPOLOGY.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/mount_notify.c           |    2 ++
 fs/namespace.c              |   38 +++++++++++++++++++++++++++++++++-----
 include/uapi/linux/fsinfo.h |   11 ++++++++++-
 samples/vfs/test-fsinfo.c   |    8 ++++++--
 4 files changed, 51 insertions(+), 8 deletions(-)

diff --git a/fs/mount_notify.c b/fs/mount_notify.c
index 403d79785807..9ca6888e53c2 100644
--- a/fs/mount_notify.c
+++ b/fs/mount_notify.c
@@ -93,6 +93,8 @@ void notify_mount(struct mount *trigger,
 	n.watch.info	= info_flags | watch_sizeof(n);
 	n.triggered_on	= trigger->mnt_id;
 
+	smp_wmb(); /* See fsinfo_generic_mount_info(). */
+
 	switch (subtype) {
 	case NOTIFY_MOUNT_EXPIRY:
 	case NOTIFY_MOUNT_READONLY:
diff --git a/fs/namespace.c b/fs/namespace.c
index 61b110149fc5..5427e732c1bf 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4166,6 +4166,21 @@ int fsinfo_generic_mount_info(struct path *path, struct fsinfo_context *ctx)
 	p->mnt_unique_id	= m->mnt_unique_id;
 	p->mnt_id		= m->mnt_id;
 
+#ifdef CONFIG_SB_NOTIFICATIONS
+	p->sb_changes		= atomic_read(&sb->s_change_counter);
+	p->sb_notifications	= atomic_read(&sb->s_notify_counter);
+#endif
+#ifdef CONFIG_MOUNT_NOTIFICATIONS
+	p->mnt_subtree_notifications = atomic_read(&m->mnt_subtree_notifications);
+	p->mnt_topology_changes	= atomic_read(&m->mnt_topology_changes);
+	p->mnt_attr_changes	= atomic_read(&m->mnt_attr_changes);
+#endif
+
+	/* Record the counters before reading the attributes as we're not
+	 * holding a lock.  Paired with a write barrier in notify_mount().
+	 */
+	smp_rmb();
+
 	flags = READ_ONCE(m->mnt.mnt_flags);
 	if (flags & MNT_READONLY)
 		p->attr |= MOUNT_ATTR_RDONLY;
@@ -4203,6 +4218,7 @@ int fsinfo_generic_mount_topology(struct path *path, struct fsinfo_context *ctx)
 
 	m = real_mount(path->mnt);
 
+	p->mnt_topology_changes	= atomic_read(&m->mnt_topology_changes);
 	p->parent_id = m->mnt_parent->mnt_id;
 
 	if (path->mnt == root.mnt) {
@@ -4313,17 +4329,29 @@ int fsinfo_generic_mount_point_full(struct path *path, struct fsinfo_context *ct
 static void fsinfo_store_mount(struct fsinfo_context *ctx, const struct mount *p)
 {
 	struct fsinfo_mount_child record = {};
+	const struct super_block *sb = p->mnt.mnt_sb;
 	unsigned int usage = ctx->usage;
 
 	if (ctx->usage >= INT_MAX)
 		return;
 	ctx->usage = usage + sizeof(record);
+	if (!ctx->buffer || ctx->usage > ctx->buf_size)
+		return;
 
-	if (ctx->buffer && ctx->usage <= ctx->buf_size) {
-		record.mnt_unique_id	= p->mnt_unique_id;
-		record.mnt_id		= p->mnt_id;
-		memcpy(ctx->buffer + usage, &record, sizeof(record));
-	}
+	record.mnt_unique_id	= p->mnt_unique_id;
+	record.mnt_id		= p->mnt_id;
+	record.notify_sum	= 0;
+#ifdef CONFIG_SB_NOTIFICATIONS
+	record.notify_sum	+= (atomic_read(&sb->s_change_counter) +
+				    atomic_read(&sb->s_notify_counter));
+#endif
+#ifdef CONFIG_MOUNT_NOTIFICATIONS
+	record.notify_sum	+= (atomic_read(&p->mnt_attr_changes) +
+				    atomic_read(&p->mnt_topology_changes) +
+				    atomic_read(&p->mnt_subtree_notifications));
+#endif
+
+	memcpy(ctx->buffer + usage, &record, sizeof(record));
 }
 
 /*
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 9410e320d824..85edc3ef2e51 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -100,6 +100,12 @@ struct fsinfo_mount_info {
 	__u64	mnt_unique_id;		/* Kernel-lifetime unique mount ID */
 	__u32	mnt_id;			/* Mount identifier (use with AT_FSINFO_MOUNTID_PATH) */
 	__u32	attr;			/* MOUNT_ATTR_* flags */
+	__u32	sb_changes;		/* Number of sb configuration changes */
+	__u32	sb_notifications;	/* Number of other sb notifications */
+	__u32	mnt_attr_changes;	/* Number of attribute changes to this mount. */
+	__u32	mnt_topology_changes;	/* Number of topology changes to this mount. */
+	__u32	mnt_subtree_notifications; /* Number of notifications in mount subtree */
+	__u32	padding[1];
 };
 
 #define FSINFO_ATTR_MOUNT_INFO__STRUCT struct fsinfo_mount_info
@@ -113,6 +119,7 @@ struct fsinfo_mount_topology {
 	__u32	master_id;		/* Slave master group ID */
 	__u32	from_id;		/* Slave propagated from ID */
 	__u32	propagation;		/* MOUNT_PROPAGATION_* flags */
+	__u32	mnt_topology_changes;	/* Number of topology changes to this mount. */
 };
 
 #define FSINFO_ATTR_MOUNT_TOPOLOGY__STRUCT struct fsinfo_mount_topology
@@ -124,7 +131,9 @@ struct fsinfo_mount_topology {
 struct fsinfo_mount_child {
 	__u64	mnt_unique_id;		/* Kernel-lifetime unique mount ID */
 	__u32	mnt_id;			/* Mount identifier (use with AT_FSINFO_MOUNTID_PATH) */
-	__u32	__padding[1];
+	__u32	notify_sum;		/* Sum of sb_changes, sb_notifications, mnt_attr_changes,
+					 * mnt_topology_changes and mnt_subtree_notifications.
+					 */
 };
 
 #define FSINFO_ATTR_MOUNT_CHILDREN__STRUCT struct fsinfo_mount_child
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index 762ab4517cd9..7b2676e1b7b0 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -297,6 +297,9 @@ static void dump_fsinfo_generic_mount_info(void *reply, unsigned int size)
 	printf("\tmnt_uniq: %llx\n", (unsigned long long)r->mnt_unique_id);
 	printf("\tmnt_id  : %x\n", r->mnt_id);
 	printf("\tattr    : %x\n", r->attr);
+	printf("\tsb_nfy  : changes=%u other=%u\n", r->sb_changes, r->sb_notifications);
+	printf("\tmnt_nfy : attr=%u topology=%u subtree=%u\n",
+	       r->mnt_attr_changes, r->mnt_topology_changes, r->mnt_subtree_notifications);
 }
 
 static void dump_fsinfo_generic_mount_topology(void *reply, unsigned int size)
@@ -309,6 +312,7 @@ static void dump_fsinfo_generic_mount_topology(void *reply, unsigned int size)
 	printf("\tmaster  : %x\n", r->master_id);
 	printf("\tfrom    : %x\n", r->from_id);
 	printf("\tpropag  : %x\n", r->propagation);
+	printf("\tmnt_nfy : topology=%u\n", r->mnt_topology_changes);
 }
 
 static void dump_fsinfo_generic_mount_children(void *reply, unsigned int size)
@@ -331,8 +335,8 @@ static void dump_fsinfo_generic_mount_children(void *reply, unsigned int size)
 		mp = "<this>";
 	}
 
-	printf("%8x %16llx %s\n",
-	       r->mnt_id, (unsigned long long)r->mnt_unique_id, mp);
+	printf("%8x %16llx %10u %s\n",
+	       r->mnt_id, (unsigned long long)r->mnt_unique_id, r->notify_sum, mp);
 }
 
 static void dump_string(void *reply, unsigned int size)



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 09/13] fsinfo: sample: Mount listing program [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (7 preceding siblings ...)
  2020-03-18 15:09 ` [PATCH 08/13] fsinfo: Provide notification overrun handling support " David Howells
@ 2020-03-18 15:09 ` David Howells
  2020-03-18 15:09 ` [PATCH 10/13] fsinfo: Add API documentation " David Howells
                   ` (5 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:09 UTC (permalink / raw)
  To: torvalds, viro
  Cc: dhowells, raven, mszeredi, christian, jannh, darrick.wong, kzak,
	jlayton, linux-api, linux-fsdevel, linux-security-module,
	linux-kernel

Implement a program to demonstrate mount listing using the new fsinfo()
syscall.  For example, to dump the tree from mount 21:

# ./test-mntinfo -m 21
MOUNT                            MOUNT ID   CHANGE#  AT P DEV   TYPE
-------------------------------- ---------- -------- -- - ----- --------
21                                       21        0  e 4  0:14 sysfs
 \_ kernel/security                      24        0  e 4   0:8 securityfs
 \_ fs/cgroup                            28        4 2f 4  0:18 tmpfs
 |   \_ unified                          29        0  e 4  0:19 cgroup2
 |   \_ systemd                          30        0  e 4  0:1a cgroup
 |   \_ blkio                            34        0  e 4  0:1e cgroup
 |   \_ net_cls,net_prio                 35        0  e 4  0:1f cgroup
 |   \_ perf_event                       36        0  e 4  0:20 cgroup
 |   \_ freezer                          37        0  e 4  0:21 cgroup
 |   \_ devices                          38        0  e 4  0:22 cgroup
 |   \_ cpu,cpuacct                      39        0  e 4  0:23 cgroup
 |   \_ rdma                             40        0  e 4  0:24 cgroup
 |   \_ memory                           41        0  e 4  0:25 cgroup
 |   \_ cpuset                           42        0  e 4  0:26 cgroup
 |   \_ hugetlb                          43        0  e 4  0:27 cgroup
 \_ fs/pstore                            31        0  e 4  0:1b pstore
 \_ firmware/efi/efivars                 32        0  e 4  0:1c efivarfs
 \_ fs/bpf                               33        0  e 4  0:1d bpf
 \_ kernel/config                        92        0  0 4  0:28 configfs
 \_ fs/selinux                           44        0  0 4  0:11 selinuxfs
 \_ kernel/debug                         45        1  0 4   0:7 debugfs

Signed-off-by: David Howells <dhowells@redhat.com>
---

 samples/vfs/Makefile       |    2 
 samples/vfs/test-mntinfo.c |  279 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 281 insertions(+)
 create mode 100644 samples/vfs/test-mntinfo.c

diff --git a/samples/vfs/Makefile b/samples/vfs/Makefile
index 9159ad1d7fc5..19be60ab950e 100644
--- a/samples/vfs/Makefile
+++ b/samples/vfs/Makefile
@@ -4,12 +4,14 @@
 hostprogs := \
 	test-fsinfo \
 	test-fsmount \
+	test-mntinfo \
 	test-statx
 
 always-y := $(hostprogs)
 
 HOSTCFLAGS_test-fsinfo.o += -I$(objtree)/usr/include
 HOSTLDLIBS_test-fsinfo += -static -lm
+HOSTCFLAGS_test-mntinfo.o += -I$(objtree)/usr/include
 
 HOSTCFLAGS_test-fsmount.o += -I$(objtree)/usr/include
 HOSTCFLAGS_test-statx.o += -I$(objtree)/usr/include
diff --git a/samples/vfs/test-mntinfo.c b/samples/vfs/test-mntinfo.c
new file mode 100644
index 000000000000..d7e9942a70d6
--- /dev/null
+++ b/samples/vfs/test-mntinfo.c
@@ -0,0 +1,279 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Test the fsinfo() system call
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define _GNU_SOURCE
+#define _ATFILE_SOURCE
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
+#include <ctype.h>
+#include <errno.h>
+#include <time.h>
+#include <math.h>
+#include <sys/syscall.h>
+#include <linux/fsinfo.h>
+#include <linux/socket.h>
+#include <linux/fcntl.h>
+#include <sys/stat.h>
+#include <arpa/inet.h>
+
+#ifndef __NR_fsinfo
+#define __NR_fsinfo -1
+#endif
+
+static __attribute__((unused))
+ssize_t fsinfo(int dfd, const char *filename,
+	       struct fsinfo_params *params, size_t params_size,
+	       void *result_buffer, size_t result_buf_size)
+{
+	return syscall(__NR_fsinfo, dfd, filename,
+		       params, params_size,
+		       result_buffer, result_buf_size);
+}
+
+static char tree_buf[4096];
+static char bar_buf[4096];
+static unsigned int children_list_interval;
+
+/*
+ * Get an fsinfo attribute in a statically allocated buffer.
+ */
+static void get_attr(unsigned int mnt_id, unsigned int attr, unsigned int Nth,
+		     void *buf, size_t buf_size)
+{
+	struct fsinfo_params params = {
+		.flags		= FSINFO_FLAGS_QUERY_MOUNT,
+		.request	= attr,
+		.Nth		= Nth,
+	};
+	char file[32];
+	long ret;
+
+	sprintf(file, "%u", mnt_id);
+
+	memset(buf, 0xbd, buf_size);
+
+	ret = fsinfo(AT_FDCWD, file, &params, sizeof(params), buf, buf_size);
+	if (ret == -1) {
+		fprintf(stderr, "mount-%s: %m\n", file);
+		exit(1);
+	}
+}
+
+/*
+ * Get an fsinfo attribute in a dynamically allocated buffer.
+ */
+static void *get_attr_alloc(unsigned int mnt_id, unsigned int attr,
+			    unsigned int Nth, size_t *_size)
+{
+	struct fsinfo_params params = {
+		.flags		= FSINFO_FLAGS_QUERY_MOUNT,
+		.request	= attr,
+		.Nth		= Nth,
+	};
+	size_t buf_size = 4096;
+	char file[32];
+	void *r;
+	long ret;
+
+	sprintf(file, "%u", mnt_id);
+
+	for (;;) {
+		r = malloc(buf_size);
+		if (!r) {
+			perror("malloc");
+			exit(1);
+		}
+		memset(r, 0xbd, buf_size);
+
+		ret = fsinfo(AT_FDCWD, file, &params, sizeof(params), r, buf_size);
+		if (ret == -1) {
+			fprintf(stderr, "mount-%s: %x,%x,%x %m\n",
+				file, params.request, params.Nth, params.Mth);
+			exit(1);
+		}
+
+		if (ret <= buf_size) {
+			*_size = ret;
+			break;
+		}
+		buf_size = (ret + 4096 - 1) & ~(4096 - 1);
+	}
+
+	return r;
+}
+
+/*
+ * Display a mount and then recurse through its children.
+ */
+static void display_mount(unsigned int mnt_id, unsigned int depth, char *path)
+{
+	struct fsinfo_mount_topology top;
+	struct fsinfo_mount_child child;
+	struct fsinfo_mount_info info;
+	struct fsinfo_ids ids;
+	void *children;
+	unsigned int d;
+	size_t ch_size, p_size;
+	char dev[64];
+	int i, n, s;
+
+	get_attr(mnt_id, FSINFO_ATTR_MOUNT_TOPOLOGY, 0, &top, sizeof(top));
+	get_attr(mnt_id, FSINFO_ATTR_MOUNT_INFO, 0, &info, sizeof(info));
+	get_attr(mnt_id, FSINFO_ATTR_IDS, 0, &ids, sizeof(ids));
+	if (depth > 0)
+		printf("%s", tree_buf);
+
+	s = strlen(path);
+	printf("%s", !s ? "\"\"" : path);
+	if (!s)
+		s += 2;
+	s += depth;
+	if (s < 38)
+		s = 38 - s;
+	else
+		s = 1;
+	printf("%*.*s", s, s, "");
+
+	sprintf(dev, "%x:%x", ids.f_dev_major, ids.f_dev_minor);
+	printf("%10u %8x %2x %x %5s %s",
+	       info.mnt_id,
+	       (info.sb_changes +
+		info.sb_notifications +
+		info.mnt_attr_changes +
+		info.mnt_topology_changes +
+		info.mnt_subtree_notifications),
+	       info.attr, top.propagation,
+	       dev, ids.f_fs_name);
+	putchar('\n');
+
+	children = get_attr_alloc(mnt_id, FSINFO_ATTR_MOUNT_CHILDREN, 0, &ch_size);
+	n = ch_size / children_list_interval - 1;
+
+	bar_buf[depth + 1] = '|';
+	if (depth > 0) {
+		tree_buf[depth - 4 + 1] = bar_buf[depth - 4 + 1];
+		tree_buf[depth - 4 + 2] = ' ';
+	}
+
+	tree_buf[depth + 0] = ' ';
+	tree_buf[depth + 1] = '\\';
+	tree_buf[depth + 2] = '_';
+	tree_buf[depth + 3] = ' ';
+	tree_buf[depth + 4] = 0;
+	d = depth + 4;
+
+	memset(&child, 0, sizeof(child));
+	for (i = 0; i < n; i++) {
+		void *p = children + i * children_list_interval;
+
+		if (sizeof(child) >= children_list_interval)
+			memcpy(&child, p, children_list_interval);
+		else
+			memcpy(&child, p, sizeof(child));
+
+		if (i == n - 1)
+			bar_buf[depth + 1] = ' ';
+		path = get_attr_alloc(child.mnt_id, FSINFO_ATTR_MOUNT_POINT,
+				      0, &p_size);
+		display_mount(child.mnt_id, d, path + 1);
+		free(path);
+	}
+
+	free(children);
+	if (depth > 0) {
+		tree_buf[depth - 4 + 1] = '\\';
+		tree_buf[depth - 4 + 2] = '_';
+	}
+	tree_buf[depth] = 0;
+}
+
+/*
+ * Find the ID of whatever is at the nominated path.
+ */
+static unsigned int lookup_mnt_by_path(const char *path)
+{
+	struct fsinfo_mount_info mnt;
+	struct fsinfo_params params = {
+		.flags		= FSINFO_FLAGS_QUERY_PATH,
+		.request	= FSINFO_ATTR_MOUNT_INFO,
+	};
+
+	if (fsinfo(AT_FDCWD, path, &params, sizeof(params), &mnt, sizeof(mnt)) == -1) {
+		perror(path);
+		exit(1);
+	}
+
+	return mnt.mnt_id;
+}
+
+/*
+ * Determine the element size for the mount child list.
+ */
+static unsigned int query_list_element_size(int mnt_id, unsigned int attr)
+{
+	struct fsinfo_attribute_info attr_info;
+
+	get_attr(mnt_id, FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, attr,
+		 &attr_info, sizeof(attr_info));
+	return attr_info.size;
+}
+
+/*
+ *
+ */
+int main(int argc, char **argv)
+{
+	unsigned int mnt_id;
+	char *path;
+	bool use_mnt_id = false;
+	int opt;
+
+	while ((opt = getopt(argc, argv, "m"))) {
+		switch (opt) {
+		case 'm':
+			use_mnt_id = true;
+			continue;
+		}
+		break;
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	switch (argc) {
+	case 0:
+		mnt_id = lookup_mnt_by_path("/");
+		path = "ROOT";
+		break;
+	case 1:
+		path = argv[0];
+		if (use_mnt_id) {
+			mnt_id = strtoul(argv[0], NULL, 0);
+			break;
+		}
+
+		mnt_id = lookup_mnt_by_path(argv[0]);
+		break;
+	default:
+		printf("Format: test-mntinfo\n");
+		printf("Format: test-mntinfo <path>\n");
+		printf("Format: test-mntinfo -m <mnt_id>\n");
+		exit(2);
+	}
+
+	children_list_interval =
+		query_list_element_size(mnt_id, FSINFO_ATTR_MOUNT_CHILDREN);
+
+	printf("MOUNT                                 MOUNT ID   CHANGE#  AT P DEV   TYPE\n");
+	printf("------------------------------------- ---------- -------- -- - ----- --------\n");
+	display_mount(mnt_id, 0, path);
+	return 0;
+}



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 10/13] fsinfo: Add API documentation [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (8 preceding siblings ...)
  2020-03-18 15:09 ` [PATCH 09/13] fsinfo: sample: Mount listing program " David Howells
@ 2020-03-18 15:09 ` David Howells
  2020-03-18 15:09 ` [PATCH 11/13] fsinfo: Add support for AFS " David Howells
                   ` (4 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:09 UTC (permalink / raw)
  To: torvalds, viro
  Cc: dhowells, raven, mszeredi, christian, jannh, darrick.wong, kzak,
	jlayton, linux-api, linux-fsdevel, linux-security-module,
	linux-kernel

Add API documentation for fsinfo.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 Documentation/filesystems/fsinfo.rst |  574 ++++++++++++++++++++++++++++++++++
 1 file changed, 574 insertions(+)
 create mode 100644 Documentation/filesystems/fsinfo.rst

diff --git a/Documentation/filesystems/fsinfo.rst b/Documentation/filesystems/fsinfo.rst
new file mode 100644
index 000000000000..65d88e5a36bc
--- /dev/null
+++ b/Documentation/filesystems/fsinfo.rst
@@ -0,0 +1,574 @@
+============================
+Filesystem Information Query
+============================
+
+The fsinfo() system call allows the querying of filesystem and filesystem
+security information beyond what stat(), statx() and statfs() can obtain.  It
+does not require a file to be opened as does ioctl().
+
+fsinfo() may be called with a path, with open file descriptor or a with a mount
+object identifier.
+
+The fsinfo() system call needs to be configured on by enabling:
+
+	"File systems"/"Enable the fsinfo() system call" (CONFIG_FSINFO)
+
+This document has the following sections:
+
+.. contents:: :local:
+
+
+Overview
+========
+
+The fsinfo() system call retrieves one of a number of attributes, the IDs of
+which can be found in include/uapi/linux/fsinfo.h::
+
+	FSINFO_ATTR_STATFS	- statfs()-style state
+	FSINFO_ATTR_IDS		- Filesystem IDs
+	FSINFO_ATTR_LIMITS	- Filesystem limits
+	...
+	FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO - Information about an attribute
+	FSINFO_ATTR_FSINFO_ATTRIBUTES - List of available attributes
+	...
+	FSINFO_ATTR_MOUNT_INFO	- Information about the mount topology
+	...
+
+Each attribute can have zero or more values, which can be of one of the
+following types:
+
+ * ``FSINFO_TYPE_VSTRUCT``.  This is a structure with a version-dependent
+   length.  New versions of the kernel may append more fields, though they are
+   not permitted to remove or replace old ones.
+
+   Older applications, expecting an older version of the field, can ask for a
+   shorter struct and will only get the fields they requested; newer
+   applications running on an older kernel will get the extra fields they
+   requested filled with zeros.  Either way, the system call returns the size
+   of the internal struct, regardless of how much data it returned.
+
+   This allows for struct-type fields to be extended in future.
+
+ * ``FSINFO_TYPE_STRING``.  This is a variable-length string of up to INT_MAX
+   characters (no NUL character is included).  The returned string will be
+   truncated if the output buffer is too small.  The total size of the string
+   is returned, regardless of any truncation.
+
+ * ``FSINFO_TYPE_OPAQUE``.  This is a variable-length blob of indeterminate
+   structure.  It may be up to INT_MAX bytes in size.
+
+ * ``FSINFO_TYPE_LIST``.  This is a variable-length list of fixed-size
+   structures.  The element size may not vary over time, so the element format
+   must be designed with care.  The maximum length is INT_MAX bytes, though
+   this depends on the kernel being able to allocate an internal buffer large
+   enough.
+
+Value type is an inherent propery of an attribute and all the values of an
+attribute must be of that type.  Each attribute can have a single value, a
+sequence of values or a sequence-of-sequences of values.
+
+
+Filesystem API
+==============
+
+If the filesystem wishes to override the generic queryable attributes or
+provide queryable attributes of its own, it should define a handler function
+and point the appropriate superblock op to it::
+
+	int (*fsinfo)(struct path *path, struct fsinfo_context *ctx);
+
+The core calls this function to see if it wants to handle the attribute.  For
+each table of attibutes it has (and it can have more than one), it should
+call::
+
+	int fsinfo_get_attribute(struct path *path, struct fsinfo_context *ctx,
+				 const struct fsinfo_attribute *attrs);
+
+to scan the table to see if the requested one is in there.  This function also
+handles determining the size of struct attributes, enumerating attributes for
+the FSINFO_ATTR_FSINFO_ATTRIBUTES and querying information about an attribute
+for FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO.
+
+If it doesn't want to handle the function, -EOPNOTSUPP should be returned.  The
+core will then examine the generic attribute table.
+
+
+Attribute Table
+---------------
+
+An attribute table is a sequence of ``struct fsinfo_attribute`` terminated with
+a blank entry.  Entries can be created with a set of helper macros::
+
+	FSINFO_VSTRUCT(A,G)
+	FSINFO_VSTRUCT_N(A,G)
+	FSINFO_VSTRUCT_NM(A,G)
+	FSINFO_STRING(A,G)
+	FSINFO_STRING_N(A,G)
+	FSINFO_STRING_NM(A,G)
+	FSINFO_OPAQUE(A,G)
+	FSINFO_LIST(A,G)
+	FSINFO_LIST_N(A,G)
+
+The names of the macro are a combination of type (vstruct, string, opaque and
+list) and an optional qualifier, if the attribute has N values or N lots of M
+values.  ``A`` is the name of the attribute and ``G`` is a function to get a
+value for that attribute.
+
+For vstruct- and list-type attributes, it is expected that there is a macro
+defined with the name ``A##__STRUCT`` that indicates the structure type.
+
+The get function needs to match the following type::
+
+	int (*get)(struct path *path, struct fsinfo_context *ctx);
+
+where "path" indicates the object to be queried and ctx is a context describing
+the parameters and the output buffer.  The function should return the total
+size of the data it would like to produce or an error.
+
+
+Context Structure
+-----------------
+
+The context struct looks like::
+
+	struct fsinfo_context {
+		__u32		requested_attr;
+		__u32		Nth;
+		__u32		Mth;
+		bool		want_size_only;
+		unsigned int	skip;
+		unsigned int	usage;
+		unsigned int	buf_size;
+		void		*buffer;
+		...
+	};
+
+The fields relevant to the filesystem are as follows:
+
+ * ``requested_attr``
+
+   Which attribute is being requested.  EOPNOTSUPP should be returned if the
+   attribute is not supported by the filesystem or the LSM.
+
+ * ``Nth`` and ``Mth``
+
+   Which value of an attribute is being requested.
+
+   For a single-value attribute Nth and Mth will both be 0.
+
+   For a "1D" attribute, Nth will indicate which value and Mth will always
+   be 0.  Take, for example, FSINFO_ATTR_SERVER_NAME - for a network
+   filesystem, the superblock will be backed by a number of servers.  This will
+   return the name of the Nth server.  ENODATA will be returned if Nth goes
+   beyond the end of the array.
+
+   For a "2D" attribute, Mth will indicate the index in the Nth set of values.
+   Take, for example, an attribute for a network filesystems that returns
+   server addresses - each server may have one or more addresses.  This could
+   return the Mth address of the Nth server.  ENODATA should be returned if the
+   Nth set doesn't exist or the Mth element of the Nth set doesn't exist.
+
+ * ``want_size_only``
+
+   Is set to true if the caller only wants the size of the value so that the
+   get function doesn't have to make expensive calculations or calls to
+   retrieve the value.
+
+ * ``skip``
+
+   This indicates how far into the buffer the data to be returned starts.  This
+   can be used to trim the front off the buffer or to handle backward-filling.
+
+ * ``usage``
+
+   This indicates how much of the buffer has been used so far for an list or
+   opaque type attribute.  This is updated by the fsinfo_note_param*()
+   functions.
+
+ * ``buf_size``
+
+   This indicates the current size of the buffer.  For the list type and the
+   opaque type this will be increased if the current buffer won't hold the
+   value and the filesystem will be called again.
+
+ * ``buffer``
+
+   This points to the output buffer.  It will be buf_size in size and will be
+   resized if the returned size is larger than this.
+
+To simplify filesystem code, there will always be at least a minimal buffer
+available if a ->get() method gets called.
+
+
+Helper Functions
+================
+
+The API includes a number of helper functions:
+
+ * ``int fsinfo_string(const char *s, struct fsinfo_context *ctx);``
+
+   This places the specified string into the buffer set in the context.  If the
+   string is NULL, the buffer will be left empty.
+
+ * ``int fsinfo_generic_timestamp_info(struct path *, struct fsinfo_context *);``
+ * ``int fsinfo_generic_supports(struct path *, struct fsinfo_context *);``
+ * ``int fsinfo_generic_limits(struct path *, struct fsinfo_context *);``
+
+   These set the generic information for timestamp resolution and range
+   information, supported features and number limits and are called for the
+   corresponding attributes if the filesystem doesn't override them.
+
+   If the filesystem does override them, it can call the above functions and
+   then amend the results.
+
+ * ``void fsinfo_set_feature(struct fsinfo_features *ft,
+			     enum fsinfo_feature feature);``
+
+   This function sets a feature flag.
+
+ * ``void fsinfo_clear_feature(struct fsinfo_features *ft,
+			       enum fsinfo_feature feature);``
+
+   This function clears a feature flag.
+
+ * ``void fsinfo_set_unix_features(struct fsinfo_features *ft);``
+
+   Set feature flags appropriate to the features of a standard UNIX filesystem,
+   such as having numeric UIDS and GIDS; allowing the creation of directories,
+   symbolic links, hard links, device files, FIFO and socket files; permitting
+   sparse files; and having access, change and modification times.
+
+
+Attribute Summary
+=================
+
+To summarise the attributes that are defined::
+
+  Symbolic name				Type
+  =====================================	===============
+  FSINFO_ATTR_STATFS			vstruct
+  FSINFO_ATTR_IDS			vstruct
+  FSINFO_ATTR_LIMITS			vstruct
+  FSINFO_ATTR_SUPPORTS			vstruct
+  FSINFO_ATTR_TIMESTAMP_INFO		vstruct
+  FSINFO_ATTR_VOLUME_ID			string
+  FSINFO_ATTR_VOLUME_UUID		vstruct
+  FSINFO_ATTR_VOLUME_NAME		string
+  FSINFO_ATTR_FEATURES			vstruct
+  FSINFO_ATTR_SOURCE			string
+  FSINFO_ATTR_CONFIGURATION		string
+  FSINFO_ATTR_FS_STATISTICS		string
+  FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO	N × vstruct
+  FSINFO_ATTR_FSINFO_ATTRIBUTES		list
+  FSINFO_ATTR_MOUNT_INFO		vstruct
+  FSINFO_ATTR_MOUNT_PATH		string
+  FSINFO_ATTR_MOUNT_POINT		string
+  FSINFO_ATTR_MOUNT_CHILDREN		list
+  FSINFO_ATTR_AFS_CELL_NAME		string
+  FSINFO_ATTR_AFS_SERVER_NAME		N × string
+  FSINFO_ATTR_AFS_SERVER_ADDRESSES	N × list
+
+
+Attribute Catalogue
+===================
+
+A number of the attributes convey information about a filesystem superblock:
+
+ *  ``FSINFO_ATTR_STATFS``
+
+    This struct-type attribute gives most of the equivalent data to statfs(),
+    but with all the fields as unconditional 64-bit or 128-bit integers.  Note
+    that static data like IDs that don't change are retrieved with
+    FSINFO_ATTR_IDS instead.
+
+    Further, superblock flags (such as MS_RDONLY) are not exposed by this
+    attribute; rather the parameters must be listed and the attributes picked
+    out from that.
+
+ *  ``FSINFO_ATTR_IDS``
+
+    This struct-type attribute conveys various identifiers used by the target
+    filesystem.  This includes the filesystem name, the NFS filesystem ID, the
+    superblock ID used in notifications, the filesystem magic type number and
+    the primary device ID.
+
+ *  ``FSINFO_ATTR_LIMITS``
+
+    This struct-type attribute conveys the limits on various aspects of a
+    filesystem, such as maximum file, symlink and xattr sizes, maxiumm filename
+    and xattr name length, maximum number of symlinks, maximum device major and
+    minor numbers and maximum UID, GID and project ID numbers.
+
+ *  ``FSINFO_ATTR_SUPPORTS``
+
+    This struct-type attribute conveys information about the support the
+    filesystem has for various UAPI features of a filesystem.  This includes
+    information about which bits are supported in various masks employed by the
+    statx system call, what FS_IOC_* flags are supported by ioctls and what
+    DOS/Windows file attribute flags are supported.
+
+ *  ``FSINFO_ATTR_TIMESTAMP_INFO``
+
+    This struct-type attribute conveys information about the resolution and
+    range of the timestamps available in a filesystem.  The resolutions are
+    given as a mantissa and exponent (resolution = mantissa * 10^exponent
+    seconds), where the exponent can be negative to indicate a sub-second
+    resolution (-9 being nanoseconds, for example).
+
+ *  ``FSINFO_ATTR_VOLUME_ID``
+
+    This is a string-type attribute that conveys the superblock identifier for
+    the volume.  By default it will be filled in from the contents of s_id from
+    the superblock.  For a block-based filesystem, for example, this might be
+    the name of the primary block device.
+
+ *  ``FSINFO_ATTR_VOLUME_UUID``
+
+    This is a struct-type attribute that conveys the UUID identifier for the
+    volume.  By default it will be filled in from the contents of s_uuid from
+    the superblock.  If this doesn't exist, it will be an entirely zeros.
+
+ *  ``FSINFO_ATTR_VOLUME_NAME``
+
+    This is a string-type attribute that conveys the name of the volume.  By
+    default it will return EOPNOTSUPP.  For a disk-based filesystem, it might
+    convey the partition label; for a network-based filesystem, it might convey
+    the name of the remote volume.
+
+ *  ``FSINFO_ATTR_FEATURES``
+
+    This is a special attribute, being a set of single-bit feature flags,
+    formatted as struct-type attribute.  The meanings of the feature bits are
+    listed below - see the "Feature Bit Catalogue" section.  The feature bits
+    are grouped numerically into bytes, such that features 0-7 are in byte 0,
+    8-15 are in byte 1, 16-23 in byte 2 and so on.
+
+    Any feature bit that's not supported by the kernel will be set to false if
+    asked for.  The highest supported feature is set at the beginning of the
+    structure.
+
+ *  ``FSINFO_ATTR_SOURCE``
+ *  ``FSINFO_ATTR_CONFIGURATION``
+ *  ``FSINFO_ATTR_FS_STATISTICS``
+
+    These attributes return the mountpoint device name (as processed by the
+    filesystem), the superblock configuration (mount) options and the
+    superblock statistics in string form, as presented through a variety
+    of /proc files.
+
+
+Some attributes give information about fsinfo itself:
+
+ *  ``FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO``
+
+    This struct-type attribute gives metadata about the attribute with the ID
+    specified by the Nth parameter, including its type, default size and
+    element size.
+
+ *  ``FSINFO_ATTR_FSINFO_ATTRIBUTES``
+
+    This list-type attribute gives a list of the attribute IDs available at the
+    point of reference.  FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO can then be used to
+    query each attribute.
+
+
+Some attributes give information about mount objects:
+
+ *  ``FSINFO_ATTR_MOUNT_INFO``
+
+    This gives information about a particular mount object, including its IDs,
+    its attributes and its event counters.
+
+ *  ``FSINFO_ATTR_MOUNT_TOPOLOGY``
+
+    This gives information about a mount object's topological relationships and
+    propagation attributes.  This is more expensive inside the kernel than
+    MOUNT_INFO due to the locking requirements, but the mount object's topology
+    change counter can be used to work out if it has changed.
+
+    This does not give a list of the children; use FSINFO_ATTR_MOUNT_CHILDREN
+    for that.
+
+ *  ``FSINFO_ATTR_MOUNT_PATH``
+
+    This gives information about the path set by binding a mount, though it may
+    be overridden by the filesystem.
+
+ *  ``FSINFO_ATTR_MOUNT_POINT``
+ *  ``FSINFO_ATTR_MOUNT_POINT_FULL``
+
+    These give the path to the mount point for a mount object, in the former
+    relative to its parent mount's mount point (limited to chroot) and in the
+    latter as a full path from the chroot.
+
+ *  ``FSINFO_ATTR_MOUNT_CHILDREN``
+
+    This gives a list of all the child mounts of the queried mount.  This is
+    presented as tuples of { mount ID, mount uniquifier, event counter sum }
+    and includes at the end a tuple representing the queried mount.
+
+
+Finally there are filesystem-specific attributes, e.g.:
+
+ *  ``FSINFO_ATTR_AFS_CELL_NAME``
+
+    This is a string-type attribute that retrieves the AFS cell name of the
+    target object.
+
+ *  ``FSINFO_ATTR_AFS_SERVER_NAME``
+
+    This is a string-type attribute that conveys the name of the Nth server
+    backing a network-filesystem superblock.
+
+ *  ``FSINFO_ATTR_AFS_SERVER_ADDRESSES``
+
+    This is a list-type attribute that conveys the addresses of the Nth server,
+    corresponding to the Nth server returned by FSINFO_ATTR_SERVER_NAME.
+
+
+Feature Bit Catalogue
+=====================
+
+The feature bits convey single true/false assertions about a specific instance
+of a filesystem (ie. a specific superblock).  They are accessed using the
+"FSINFO_ATTR_FEATURE" attribute:
+
+ *  ``FSINFO_FEAT_IS_KERNEL_FS``
+ *  ``FSINFO_FEAT_IS_BLOCK_FS``
+ *  ``FSINFO_FEAT_IS_FLASH_FS``
+ *  ``FSINFO_FEAT_IS_NETWORK_FS``
+ *  ``FSINFO_FEAT_IS_AUTOMOUNTER_FS``
+ *  ``FSINFO_FEAT_IS_MEMORY_FS``
+
+    These indicate what kind of filesystem the target is: kernel API (proc),
+    block-based (ext4), flash/nvm-based (jffs2), remote over the network (NFS),
+    local quasi-filesystem that acts as a tray of mountpoints (autofs), plain
+    in-memory filesystem (shmem).
+
+ *  ``FSINFO_FEAT_AUTOMOUNTS``
+
+    This indicate if a filesystem may have objects that are automount points.
+
+ *  ``FSINFO_FEAT_ADV_LOCKS``
+ *  ``FSINFO_FEAT_MAND_LOCKS``
+ *  ``FSINFO_FEAT_LEASES``
+
+    These indicate if a filesystem supports advisory locks, mandatory locks or
+    leases.
+
+ *  ``FSINFO_FEAT_UIDS``
+ *  ``FSINFO_FEAT_GIDS``
+ *  ``FSINFO_FEAT_PROJIDS``
+
+    These indicate if a filesystem supports/stores/transports numeric user IDs,
+    group IDs or project IDs.  The "FSINFO_ATTR_LIMITS" attribute can be used
+    to find out the upper limits on the IDs values.
+
+ *  ``FSINFO_FEAT_STRING_USER_IDS``
+
+    This indicates if a filesystem supports/stores/transports string user
+    identifiers.
+
+ *  ``FSINFO_FEAT_GUID_USER_IDS``
+
+    This indicates if a filesystem supports/stores/transports Windows GUIDs as
+    user identifiers (eg. ntfs).
+
+ *  ``FSINFO_FEAT_WINDOWS_ATTRS``
+
+    This indicates if a filesystem supports Windows FILE_* attribute bits
+    (eg. cifs, jfs).  The "FSINFO_ATTR_SUPPORTS" attribute can be used to find
+    out which windows file attributes are supported by the filesystem.
+
+ *  ``FSINFO_FEAT_USER_QUOTAS``
+ *  ``FSINFO_FEAT_GROUP_QUOTAS``
+ *  ``FSINFO_FEAT_PROJECT_QUOTAS``
+
+    These indicate if a filesystem supports quotas for users, groups or
+    projects.
+
+ *  ``FSINFO_FEAT_XATTRS``
+
+    These indicate if a filesystem supports extended attributes.  The
+    "FSINFO_ATTR_LIMITS" attribute can be used to find out the upper limits on
+    the supported name and body lengths.
+
+ *  ``FSINFO_FEAT_JOURNAL``
+ *  ``FSINFO_FEAT_DATA_IS_JOURNALLED``
+
+    These indicate whether the filesystem has a journal and whether data
+    changes are logged to it.
+
+ *  ``FSINFO_FEAT_O_SYNC``
+ *  ``FSINFO_FEAT_O_DIRECT``
+
+    These indicate whether the filesystem supports the O_SYNC and O_DIRECT
+    flags.
+
+ *  ``FSINFO_FEAT_VOLUME_ID``
+ *  ``FSINFO_FEAT_VOLUME_UUID``
+ *  ``FSINFO_FEAT_VOLUME_NAME``
+ *  ``FSINFO_FEAT_VOLUME_FSID``
+
+    These indicate whether ID, UUID, name and FSID identifiers actually exist
+    in the filesystem and thus might be considered persistent.
+
+ *  ``FSINFO_FEAT_IVER_ALL_CHANGE``
+ *  ``FSINFO_FEAT_IVER_DATA_CHANGE``
+ *  ``FSINFO_FEAT_IVER_MONO_INCR``
+
+    These indicate whether i_version in the inode is supported and, if so, what
+    mode it operates in.  The first two indicate if it's changed for any data
+    or metadata change, or whether it's only changed for any data changes; the
+    last indicates whether or not it's monotonically increasing for each such
+    change.
+
+ *  ``FSINFO_FEAT_HARD_LINKS``
+ *  ``FSINFO_FEAT_HARD_LINKS_1DIR``
+
+    These indicate whether the filesystem can have hard links made in it, and
+    whether they can be made between directory or only within the same
+    directory.
+
+ *  ``FSINFO_FEAT_DIRECTORIES``
+ *  ``FSINFO_FEAT_SYMLINKS``
+ *  ``FSINFO_FEAT_DEVICE_FILES``
+ *  ``FSINFO_FEAT_UNIX_SPECIALS``
+
+    These indicate whether directories; symbolic links; device files; or pipes
+    and sockets can be made within the filesystem.
+
+ *  ``FSINFO_FEAT_RESOURCE_FORKS``
+
+    This indicates if the filesystem supports resource forks.
+
+ *  ``FSINFO_FEAT_NAME_CASE_INDEP``
+ *  ``FSINFO_FEAT_NAME_NON_UTF8``
+ *  ``FSINFO_FEAT_NAME_HAS_CODEPAGE``
+
+    These indicate if the filesystem supports case-independent file names,
+    whether the filenames are non-utf8 (see the "FSINFO_ATTR_NAME_ENCODING"
+    attribute) and whether a codepage is in use to transliterate them (see
+    the "FSINFO_ATTR_NAME_CODEPAGE" attribute).
+
+ *  ``FSINFO_FEAT_SPARSE``
+
+    This indicates if a filesystem supports sparse files.
+
+ *  ``FSINFO_FEAT_NOT_PERSISTENT``
+
+    This indicates if a filesystem is not persistent.
+
+ *  ``FSINFO_FEAT_NO_UNIX_MODE``
+
+    This indicates if a filesystem doesn't support UNIX mode bits (though they
+    may be manufactured from other bits, such as Windows file attribute flags).
+
+ *  ``FSINFO_FEAT_HAS_ATIME``
+ *  ``FSINFO_FEAT_HAS_BTIME``
+ *  ``FSINFO_FEAT_HAS_CTIME``
+ *  ``FSINFO_FEAT_HAS_MTIME``
+
+    These indicate which timestamps a filesystem supports (access, birth,
+    change, modify).  The range and resolutions can be queried with the
+    "FSINFO_ATTR_TIMESTAMPS" attribute).



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 11/13] fsinfo: Add support for AFS [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (9 preceding siblings ...)
  2020-03-18 15:09 ` [PATCH 10/13] fsinfo: Add API documentation " David Howells
@ 2020-03-18 15:09 ` David Howells
  2020-03-18 15:09 ` [PATCH 12/13] fsinfo: Example support for Ext4 " David Howells
                   ` (3 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:09 UTC (permalink / raw)
  To: torvalds, viro
  Cc: dhowells, raven, mszeredi, christian, jannh, darrick.wong, kzak,
	jlayton, linux-api, linux-fsdevel, linux-security-module,
	linux-kernel

Add fsinfo support to the AFS filesystem.  This allows the export of server
lists, amongst other things, which is necessary to implement some of the
AFS 'fs' command set, such as "checkservers", "getserverprefs" and
"whereis".

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/internal.h           |    1 
 fs/afs/super.c              |  218 +++++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/fsinfo.h |   15 +++
 samples/vfs/test-fsinfo.c   |   49 ++++++++++
 4 files changed, 281 insertions(+), 2 deletions(-)

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 1d81fc4c3058..b4b2a8a18e9f 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -248,6 +248,7 @@ struct afs_super_info {
 	struct afs_volume	*volume;	/* volume record */
 	enum afs_flock_mode	flock_mode:8;	/* File locking emulation mode */
 	bool			dyn_root;	/* True if dynamic root */
+	bool			autocell;	/* True if autocell */
 };
 
 static inline struct afs_super_info *AFS_FS_S(struct super_block *sb)
diff --git a/fs/afs/super.c b/fs/afs/super.c
index dda7a9a66848..969248a192a2 100644
--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -26,9 +26,13 @@
 #include <linux/sched.h>
 #include <linux/nsproxy.h>
 #include <linux/magic.h>
+#include <linux/fsinfo.h>
 #include <net/net_namespace.h>
 #include "internal.h"
 
+#ifdef CONFIG_FSINFO
+static int afs_fsinfo(struct path *path, struct fsinfo_context *ctx);
+#endif
 static void afs_i_init_once(void *foo);
 static void afs_kill_super(struct super_block *sb);
 static struct inode *afs_alloc_inode(struct super_block *sb);
@@ -54,6 +58,9 @@ int afs_net_id;
 
 static const struct super_operations afs_super_ops = {
 	.statfs		= afs_statfs,
+#ifdef CONFIG_FSINFO
+	.fsinfo		= afs_fsinfo,
+#endif
 	.alloc_inode	= afs_alloc_inode,
 	.drop_inode	= afs_drop_inode,
 	.destroy_inode	= afs_destroy_inode,
@@ -193,7 +200,7 @@ static int afs_show_options(struct seq_file *m, struct dentry *root)
 
 	if (as->dyn_root)
 		seq_puts(m, ",dyn");
-	if (test_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(d_inode(root))->flags))
+	if (as->autocell)
 		seq_puts(m, ",autocell");
 	switch (as->flock_mode) {
 	case afs_flock_mode_unset:	break;
@@ -458,7 +465,7 @@ static int afs_fill_super(struct super_block *sb, struct afs_fs_context *ctx)
 	if (IS_ERR(inode))
 		return PTR_ERR(inode);
 
-	if (ctx->autocell || as->dyn_root)
+	if (as->autocell || as->dyn_root)
 		set_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(inode)->flags);
 
 	ret = -ENOMEM;
@@ -498,6 +505,8 @@ static struct afs_super_info *afs_alloc_sbi(struct fs_context *fc)
 			as->cell = afs_get_cell(ctx->cell);
 			as->volume = __afs_get_volume(ctx->volume);
 		}
+		if (ctx->autocell)
+			as->autocell = true;
 	}
 	return as;
 }
@@ -760,3 +769,208 @@ static int afs_statfs(struct dentry *dentry, struct kstatfs *buf)
 
 	return ret;
 }
+
+#ifdef CONFIG_FSINFO
+static const struct fsinfo_timestamp_info afs_timestamp_info = {
+	.atime = {
+		.minimum	= 0,
+		.maximum	= UINT_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+	.mtime = {
+		.minimum	= 0,
+		.maximum	= UINT_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+	.ctime = {
+		.minimum	= 0,
+		.maximum	= UINT_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+	.btime = {
+		.minimum	= 0,
+		.maximum	= UINT_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+};
+
+static int afs_fsinfo_get_timestamp(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_timestamp_info *tsinfo = ctx->buffer;
+	*tsinfo = afs_timestamp_info;
+	return sizeof(*tsinfo);
+}
+
+static int afs_fsinfo_get_limits(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_limits *lim = ctx->buffer;
+
+	lim->max_file_size.hi	= 0;
+	lim->max_file_size.lo	= MAX_LFS_FILESIZE;
+	/* Inode numbers can be 96-bit on YFS, but that's hard to determine. */
+	lim->max_ino.hi		= 0;
+	lim->max_ino.lo		= UINT_MAX;
+	lim->max_hard_links	= UINT_MAX;
+	lim->max_uid		= UINT_MAX;
+	lim->max_gid		= UINT_MAX;
+	lim->max_filename_len	= AFSNAMEMAX - 1;
+	lim->max_symlink_len	= AFSPATHMAX - 1;
+	return sizeof(*lim);
+}
+
+static int afs_fsinfo_get_supports(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_supports *p = ctx->buffer;
+
+	p->stx_mask = (STATX_TYPE | STATX_MODE |
+		       STATX_NLINK |
+		       STATX_UID | STATX_GID |
+		       STATX_MTIME | STATX_INO |
+		       STATX_SIZE);
+	p->stx_attributes = STATX_ATTR_AUTOMOUNT;
+	return sizeof(*p);
+}
+
+static int afs_fsinfo_get_features(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_features *p = ctx->buffer;
+
+	fsinfo_set_feature(p, FSINFO_FEAT_IS_NETWORK_FS);
+	fsinfo_set_feature(p, FSINFO_FEAT_AUTOMOUNTS);
+	fsinfo_set_feature(p, FSINFO_FEAT_ADV_LOCKS);
+	fsinfo_set_feature(p, FSINFO_FEAT_UIDS);
+	fsinfo_set_feature(p, FSINFO_FEAT_GIDS);
+	fsinfo_set_feature(p, FSINFO_FEAT_VOLUME_ID);
+	fsinfo_set_feature(p, FSINFO_FEAT_VOLUME_NAME);
+	fsinfo_set_feature(p, FSINFO_FEAT_IVER_MONO_INCR);
+	fsinfo_set_feature(p, FSINFO_FEAT_SYMLINKS);
+	fsinfo_set_feature(p, FSINFO_FEAT_HARD_LINKS_1DIR);
+	fsinfo_set_feature(p, FSINFO_FEAT_HAS_MTIME);
+	fsinfo_set_feature(p, FSINFO_FEAT_HAS_INODE_NUMBERS);
+	return sizeof(*p);
+}
+
+static int afs_dyn_fsinfo_get_features(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_features *p = ctx->buffer;
+
+	fsinfo_set_feature(p, FSINFO_FEAT_IS_AUTOMOUNTER_FS);
+	fsinfo_set_feature(p, FSINFO_FEAT_AUTOMOUNTS);
+	return sizeof(*p);
+}
+
+static int afs_fsinfo_get_volume_name(struct path *path, struct fsinfo_context *ctx)
+{
+	struct afs_super_info *as = AFS_FS_S(path->dentry->d_sb);
+	struct afs_volume *volume = as->volume;
+
+	memcpy(ctx->buffer, volume->name, volume->name_len);
+	return volume->name_len;
+}
+
+static int afs_fsinfo_get_cell_name(struct path *path, struct fsinfo_context *ctx)
+{
+	struct afs_super_info *as = AFS_FS_S(path->dentry->d_sb);
+	struct afs_cell *cell = as->cell;
+
+	memcpy(ctx->buffer, cell->name, cell->name_len);
+	return cell->name_len;
+}
+
+static int afs_fsinfo_get_server_name(struct path *path, struct fsinfo_context *ctx)
+{
+	struct afs_server_list *slist;
+	struct afs_super_info *as = AFS_FS_S(path->dentry->d_sb);
+	struct afs_volume *volume = as->volume;
+	struct afs_server *server;
+	int ret = -ENODATA;
+
+	read_lock(&volume->servers_lock);
+	slist = volume->servers;
+	if (slist) {
+		if (ctx->Nth < slist->nr_servers) {
+			server = slist->servers[ctx->Nth].server;
+			ret = sprintf(ctx->buffer, "%pU", &server->uuid);
+		}
+	}
+
+	read_unlock(&volume->servers_lock);
+	return ret;
+}
+
+static int afs_fsinfo_get_server_address(struct path *path, struct fsinfo_context *ctx)
+{
+	struct fsinfo_afs_server_address *p = ctx->buffer;
+	struct afs_server_list *slist;
+	struct afs_super_info *as = AFS_FS_S(path->dentry->d_sb);
+	struct afs_addr_list *alist;
+	struct afs_volume *volume = as->volume;
+	struct afs_server *server;
+	struct afs_net *net = afs_d2net(path->dentry);
+	unsigned int i;
+	int ret = -ENODATA;
+
+	read_lock(&volume->servers_lock);
+	slist = afs_get_serverlist(volume->servers);
+	read_unlock(&volume->servers_lock);
+
+	if (ctx->Nth >= slist->nr_servers)
+		goto put_slist;
+	server = slist->servers[ctx->Nth].server;
+
+	read_lock(&server->fs_lock);
+	alist = afs_get_addrlist(rcu_dereference_protected(
+					 server->addresses,
+					 lockdep_is_held(&server->fs_lock)));
+	read_unlock(&server->fs_lock);
+	if (!alist)
+		goto put_slist;
+
+	ret = alist->nr_addrs * sizeof(*p);
+	if (ret <= ctx->buf_size) {
+		for (i = 0; i < alist->nr_addrs; i++)
+			memcpy(&p[i].address, &alist->addrs[i],
+			       sizeof(struct sockaddr_rxrpc));
+	}
+
+	afs_put_addrlist(alist);
+put_slist:
+	afs_put_serverlist(net, slist);
+	return ret;
+}
+
+static const struct fsinfo_attribute afs_fsinfo_attributes[] = {
+	FSINFO_VSTRUCT	(FSINFO_ATTR_TIMESTAMP_INFO,	afs_fsinfo_get_timestamp),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_LIMITS,		afs_fsinfo_get_limits),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_SUPPORTS,		afs_fsinfo_get_supports),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_FEATURES,		afs_fsinfo_get_features),
+	FSINFO_STRING	(FSINFO_ATTR_VOLUME_NAME,	afs_fsinfo_get_volume_name),
+	FSINFO_STRING	(FSINFO_ATTR_AFS_CELL_NAME,	afs_fsinfo_get_cell_name),
+	FSINFO_STRING_N	(FSINFO_ATTR_AFS_SERVER_NAME,	afs_fsinfo_get_server_name),
+	FSINFO_LIST_N	(FSINFO_ATTR_AFS_SERVER_ADDRESSES, afs_fsinfo_get_server_address),
+	{}
+};
+
+static const struct fsinfo_attribute afs_dyn_fsinfo_attributes[] = {
+	FSINFO_VSTRUCT(FSINFO_ATTR_TIMESTAMP_INFO,	afs_fsinfo_get_timestamp),
+	FSINFO_VSTRUCT(FSINFO_ATTR_FEATURES,		afs_dyn_fsinfo_get_features),
+	{}
+};
+
+static int afs_fsinfo(struct path *path, struct fsinfo_context *ctx)
+{
+	struct afs_super_info *as = AFS_FS_S(path->dentry->d_sb);
+	int ret;
+
+	if (as->dyn_root)
+		ret = fsinfo_get_attribute(path, ctx, afs_dyn_fsinfo_attributes);
+	else
+		ret = fsinfo_get_attribute(path, ctx, afs_fsinfo_attributes);
+	return ret;
+}
+
+#endif /* CONFIG_FSINFO */
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 85edc3ef2e51..150b693a1b5a 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -38,6 +38,10 @@
 #define FSINFO_ATTR_MOUNT_TOPOLOGY	0x204	/* Mount object topology */
 #define FSINFO_ATTR_MOUNT_CHILDREN	0x205	/* Children of this mount (list) */
 
+#define FSINFO_ATTR_AFS_CELL_NAME	0x300	/* AFS cell name (string) */
+#define FSINFO_ATTR_AFS_SERVER_NAME	0x301	/* Name of the Nth server (string) */
+#define FSINFO_ATTR_AFS_SERVER_ADDRESSES 0x302	/* List of addresses of the Nth server */
+
 /*
  * Optional fsinfo() parameter structure.
  *
@@ -308,4 +312,15 @@ struct fsinfo_volume_uuid {
 
 #define FSINFO_ATTR_VOLUME_UUID__STRUCT struct fsinfo_volume_uuid
 
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_AFS_SERVER_ADDRESSES).
+ *
+ * Get the addresses of the Nth server for a network filesystem.
+ */
+struct fsinfo_afs_server_address {
+	struct __kernel_sockaddr_storage address;
+};
+
+#define FSINFO_ATTR_AFS_SERVER_ADDRESSES__STRUCT struct fsinfo_afs_server_address
+
 #endif /* _UAPI_LINUX_FSINFO_H */
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index 7b2676e1b7b0..9f9564f7f73e 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -23,6 +23,7 @@
 #include <linux/socket.h>
 #include <sys/stat.h>
 #include <arpa/inet.h>
+#include <linux/rxrpc.h>
 
 #ifndef __NR_fsinfo
 #define __NR_fsinfo -1
@@ -339,6 +340,50 @@ static void dump_fsinfo_generic_mount_children(void *reply, unsigned int size)
 	       r->mnt_id, (unsigned long long)r->mnt_unique_id, r->notify_sum, mp);
 }
 
+static void dump_afs_fsinfo_server_address(void *reply, unsigned int size)
+{
+	struct fsinfo_afs_server_address *f = reply;
+	struct sockaddr_storage *ss = (struct sockaddr_storage *)&f->address;
+	struct sockaddr_rxrpc *srx;
+	struct sockaddr_in6 *sin6;
+	struct sockaddr_in *sin;
+	char proto[32], buf[1024];
+
+	if (ss->ss_family == AF_RXRPC) {
+		srx = (struct sockaddr_rxrpc *)ss;
+		printf("%5u ", srx->srx_service);
+		switch (srx->transport_type) {
+		case SOCK_DGRAM:
+			sprintf(proto, "udp");
+			break;
+		case SOCK_STREAM:
+			sprintf(proto, "tcp");
+			break;
+		default:
+			sprintf(proto, "%3u", srx->transport_type);
+			break;
+		}
+		ss = (struct sockaddr_storage *)&srx->transport;
+	}
+
+	switch (ss->ss_family) {
+	case AF_INET:
+		sin = (struct sockaddr_in *)ss;
+		if (!inet_ntop(AF_INET, &sin->sin_addr, buf, sizeof(buf)))
+			break;
+		printf("%5u/%s %s\n", ntohs(sin->sin_port), proto, buf);
+		return;
+	case AF_INET6:
+		sin6 = (struct sockaddr_in6 *)ss;
+		if (!inet_ntop(AF_INET6, &sin6->sin6_addr, buf, sizeof(buf)))
+			break;
+		printf("%5u/%s %s\n", ntohs(sin6->sin6_port), proto, buf);
+		return;
+	}
+
+	printf("family=%u\n", ss->ss_family);
+}
+
 static void dump_string(void *reply, unsigned int size)
 {
 	char *s = reply, *p;
@@ -422,6 +467,10 @@ static const struct fsinfo_attribute fsinfo_attributes[] = {
 	FSINFO_STRING_N	(FSINFO_ATTR_MOUNT_POINT,	string),
 	FSINFO_STRING_N	(FSINFO_ATTR_MOUNT_POINT_FULL,	string),
 	FSINFO_LIST	(FSINFO_ATTR_MOUNT_CHILDREN,	fsinfo_generic_mount_children),
+
+	FSINFO_STRING	(FSINFO_ATTR_AFS_CELL_NAME,	string),
+	FSINFO_STRING	(FSINFO_ATTR_AFS_SERVER_NAME,	string),
+	FSINFO_LIST_N	(FSINFO_ATTR_AFS_SERVER_ADDRESSES, afs_fsinfo_server_address),
 	{}
 };
 



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 12/13] fsinfo: Example support for Ext4 [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (10 preceding siblings ...)
  2020-03-18 15:09 ` [PATCH 11/13] fsinfo: Add support for AFS " David Howells
@ 2020-03-18 15:09 ` David Howells
  2020-03-18 15:10 ` [PATCH 13/13] fsinfo: Example support for NFS " David Howells
                   ` (2 subsequent siblings)
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:09 UTC (permalink / raw)
  To: torvalds, viro
  Cc: Theodore Ts'o, Andreas Dilger, linux-ext4, dhowells, raven,
	mszeredi, christian, jannh, darrick.wong, kzak, jlayton,
	linux-api, linux-fsdevel, linux-security-module, linux-kernel

Add the ability to list some Ext4 volume timestamps as an example.

Is this useful for ext4?  Is there anything else that could be useful?

Signed-off-by: David Howells <dhowells@redhat.com>
cc: "Theodore Ts'o" <tytso@mit.edu>
cc: Andreas Dilger <adilger.kernel@dilger.ca>
cc: linux-ext4@vger.kernel.org
---

 fs/ext4/Makefile            |    1 +
 fs/ext4/ext4.h              |    6 ++++++
 fs/ext4/fsinfo.c            |   45 +++++++++++++++++++++++++++++++++++++++++++
 fs/ext4/super.c             |    3 +++
 include/uapi/linux/fsinfo.h |   16 +++++++++++++++
 samples/vfs/test-fsinfo.c   |   35 +++++++++++++++++++++++++++++++++
 6 files changed, 106 insertions(+)
 create mode 100644 fs/ext4/fsinfo.c

diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
index 4ccb3c9189d8..71d5b460c7c7 100644
--- a/fs/ext4/Makefile
+++ b/fs/ext4/Makefile
@@ -16,3 +16,4 @@ ext4-$(CONFIG_EXT4_FS_SECURITY)		+= xattr_security.o
 ext4-inode-test-objs			+= inode-test.o
 obj-$(CONFIG_EXT4_KUNIT_TESTS)		+= ext4-inode-test.o
 ext4-$(CONFIG_FS_VERITY)		+= verity.o
+ext4-$(CONFIG_FSINFO)			+= fsinfo.o
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 61b37a052052..f0304aa107f8 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -42,6 +42,7 @@
 
 #include <linux/fscrypt.h>
 #include <linux/fsverity.h>
+#include <linux/fsinfo.h>
 
 #include <linux/compiler.h>
 
@@ -3190,6 +3191,11 @@ extern const struct inode_operations ext4_file_inode_operations;
 extern const struct file_operations ext4_file_operations;
 extern loff_t ext4_llseek(struct file *file, loff_t offset, int origin);
 
+/* fsinfo.c */
+#ifdef CONFIG_FSINFO
+extern int ext4_fsinfo(struct path *path, struct fsinfo_context *ctx);
+#endif
+
 /* inline.c */
 extern int ext4_get_max_inline_size(struct inode *inode);
 extern int ext4_find_inline_data_nolock(struct inode *inode);
diff --git a/fs/ext4/fsinfo.c b/fs/ext4/fsinfo.c
new file mode 100644
index 000000000000..785f82a74dc9
--- /dev/null
+++ b/fs/ext4/fsinfo.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Filesystem information for ext4
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/mount.h>
+#include "ext4.h"
+
+static int ext4_fsinfo_get_volume_name(struct path *path, struct fsinfo_context *ctx)
+{
+	const struct ext4_sb_info *sbi = EXT4_SB(path->mnt->mnt_sb);
+	const struct ext4_super_block *es = sbi->s_es;
+
+	memcpy(ctx->buffer, es->s_volume_name, sizeof(es->s_volume_name));
+	return strlen(ctx->buffer);
+}
+
+static int ext4_fsinfo_get_timestamps(struct path *path, struct fsinfo_context *ctx)
+{
+	const struct ext4_sb_info *sbi = EXT4_SB(path->mnt->mnt_sb);
+	const struct ext4_super_block *es = sbi->s_es;
+	struct fsinfo_ext4_timestamps *ts = ctx->buffer;
+
+#define Z(R,S) R = S | (((u64)S##_hi) << 32)
+	Z(ts->mkfs_time,	es->s_mkfs_time);
+	Z(ts->mount_time,	es->s_mtime);
+	Z(ts->write_time,	es->s_wtime);
+	Z(ts->last_check_time,	es->s_lastcheck);
+	Z(ts->first_error_time,	es->s_first_error_time);
+	Z(ts->last_error_time,	es->s_last_error_time);
+	return sizeof(*ts);
+}
+
+static const struct fsinfo_attribute ext4_fsinfo_attributes[] = {
+	FSINFO_STRING	(FSINFO_ATTR_VOLUME_NAME,	ext4_fsinfo_get_volume_name),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_EXT4_TIMESTAMPS,	ext4_fsinfo_get_timestamps),
+	{}
+};
+
+int ext4_fsinfo(struct path *path, struct fsinfo_context *ctx)
+{
+	return fsinfo_get_attribute(path, ctx, ext4_fsinfo_attributes);
+}
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ff1b764b0c0e..3655fbeab754 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1487,6 +1487,9 @@ static const struct super_operations ext4_sops = {
 	.freeze_fs	= ext4_freeze,
 	.unfreeze_fs	= ext4_unfreeze,
 	.statfs		= ext4_statfs,
+#ifdef CONFIG_FSINFO
+	.fsinfo		= ext4_fsinfo,
+#endif
 	.remount_fs	= ext4_remount,
 	.show_options	= ext4_show_options,
 #ifdef CONFIG_QUOTA
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 150b693a1b5a..4cfb71227eff 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -42,6 +42,8 @@
 #define FSINFO_ATTR_AFS_SERVER_NAME	0x301	/* Name of the Nth server (string) */
 #define FSINFO_ATTR_AFS_SERVER_ADDRESSES 0x302	/* List of addresses of the Nth server */
 
+#define FSINFO_ATTR_EXT4_TIMESTAMPS	0x400	/* Ext4 superblock timestamps */
+
 /*
  * Optional fsinfo() parameter structure.
  *
@@ -323,4 +325,18 @@ struct fsinfo_afs_server_address {
 
 #define FSINFO_ATTR_AFS_SERVER_ADDRESSES__STRUCT struct fsinfo_afs_server_address
 
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_EXT4_TIMESTAMPS).
+ */
+struct fsinfo_ext4_timestamps {
+	__u64		mkfs_time;
+	__u64		mount_time;
+	__u64		write_time;
+	__u64		last_check_time;
+	__u64		first_error_time;
+	__u64		last_error_time;
+};
+
+#define FSINFO_ATTR_EXT4_TIMESTAMPS__STRUCT struct fsinfo_ext4_timestamps
+
 #endif /* _UAPI_LINUX_FSINFO_H */
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index 9f9564f7f73e..6ad1128a3e1d 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -384,6 +384,40 @@ static void dump_afs_fsinfo_server_address(void *reply, unsigned int size)
 	printf("family=%u\n", ss->ss_family);
 }
 
+static char *dump_ext4_time(char *buffer, time_t tim)
+{
+	struct tm tm;
+	int len;
+
+	if (tim == 0)
+		return "-";
+
+	if (!localtime_r(&tim, &tm)) {
+		perror("localtime_r");
+		exit(1);
+	}
+	len = strftime(buffer, 100, "%F %T", &tm);
+	if (len == 0) {
+		perror("strftime");
+		exit(1);
+	}
+	return buffer;
+}
+
+static void dump_ext4_fsinfo_timestamps(void *reply, unsigned int size)
+{
+	struct fsinfo_ext4_timestamps *r = reply;
+	char buffer[100];
+
+	printf("\n");
+	printf("\tmkfs    : %s\n", dump_ext4_time(buffer, r->mkfs_time));
+	printf("\tmount   : %s\n", dump_ext4_time(buffer, r->mount_time));
+	printf("\twrite   : %s\n", dump_ext4_time(buffer, r->write_time));
+	printf("\tfsck    : %s\n", dump_ext4_time(buffer, r->last_check_time));
+	printf("\t1st-err : %s\n", dump_ext4_time(buffer, r->first_error_time));
+	printf("\tlast-err: %s\n", dump_ext4_time(buffer, r->last_error_time));
+}
+
 static void dump_string(void *reply, unsigned int size)
 {
 	char *s = reply, *p;
@@ -471,6 +505,7 @@ static const struct fsinfo_attribute fsinfo_attributes[] = {
 	FSINFO_STRING	(FSINFO_ATTR_AFS_CELL_NAME,	string),
 	FSINFO_STRING	(FSINFO_ATTR_AFS_SERVER_NAME,	string),
 	FSINFO_LIST_N	(FSINFO_ATTR_AFS_SERVER_ADDRESSES, afs_fsinfo_server_address),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_EXT4_TIMESTAMPS,	ext4_fsinfo_timestamps),
 	{}
 };
 



^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 13/13] fsinfo: Example support for NFS [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (11 preceding siblings ...)
  2020-03-18 15:09 ` [PATCH 12/13] fsinfo: Example support for Ext4 " David Howells
@ 2020-03-18 15:10 ` David Howells
  2020-03-18 16:05 ` [PATCH 00/13] VFS: Filesystem information " Miklos Szeredi
  2020-03-19 10:37 ` David Howells
  14 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-03-18 15:10 UTC (permalink / raw)
  To: torvalds, viro
  Cc: Trond Myklebust, Anna Schumaker, linux-nfs, dhowells, raven,
	mszeredi, christian, jannh, darrick.wong, kzak, jlayton,
	linux-api, linux-fsdevel, linux-security-module, linux-kernel

Add the ability to list NFS server addresses and hostname, timestamp
information and capabilities as an example.

Is this useful for export from NFS?  Is there anything else that would be
useful?

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Trond Myklebust <trond.myklebust@hammerspace.com>
cc: Anna Schumaker <anna.schumaker@netapp.com>
cc: linux-nfs@vger.kernel.org
---

 fs/nfs/Makefile              |    1 
 fs/nfs/fsinfo.c              |  230 ++++++++++++++++++++++++++++++++++++++++++
 fs/nfs/internal.h            |    6 +
 fs/nfs/nfs4super.c           |    3 +
 fs/nfs/super.c               |    3 +
 include/uapi/linux/fsinfo.h  |   29 +++++
 include/uapi/linux/windows.h |   35 ++++++
 samples/vfs/test-fsinfo.c    |   38 +++++++
 8 files changed, 345 insertions(+)
 create mode 100644 fs/nfs/fsinfo.c
 create mode 100644 include/uapi/linux/windows.h

diff --git a/fs/nfs/Makefile b/fs/nfs/Makefile
index 2433c3e03cfa..20fbc9596833 100644
--- a/fs/nfs/Makefile
+++ b/fs/nfs/Makefile
@@ -13,6 +13,7 @@ nfs-y 			:= client.o dir.o file.o getroot.o inode.o super.o \
 nfs-$(CONFIG_ROOT_NFS)	+= nfsroot.o
 nfs-$(CONFIG_SYSCTL)	+= sysctl.o
 nfs-$(CONFIG_NFS_FSCACHE) += fscache.o fscache-index.o
+nfs-$(CONFIG_FSINFO)	+= fsinfo.o
 
 obj-$(CONFIG_NFS_V2) += nfsv2.o
 nfsv2-y := nfs2super.o proc.o nfs2xdr.o
diff --git a/fs/nfs/fsinfo.c b/fs/nfs/fsinfo.c
new file mode 100644
index 000000000000..a0299ec27efd
--- /dev/null
+++ b/fs/nfs/fsinfo.c
@@ -0,0 +1,230 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Filesystem information for NFS
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/nfs_fs.h>
+#include <linux/windows.h>
+#include "internal.h"
+
+static const struct fsinfo_timestamp_info nfs_timestamp_info = {
+	.atime = {
+		.minimum	= 0,
+		.maximum	= UINT_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+	.mtime = {
+		.minimum	= 0,
+		.maximum	= UINT_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+	.ctime = {
+		.minimum	= 0,
+		.maximum	= UINT_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+	.btime = {
+		.minimum	= 0,
+		.maximum	= UINT_MAX,
+		.gran_mantissa	= 1,
+		.gran_exponent	= 0,
+	},
+};
+
+static int nfs_fsinfo_get_timestamp_info(struct path *path, struct fsinfo_context *ctx)
+{
+	const struct nfs_server *server = NFS_SB(path->dentry->d_sb);
+	struct fsinfo_timestamp_info *r = ctx->buffer;
+	unsigned long long nsec;
+	unsigned int rem, mant;
+	int exp = -9;
+
+	*r = nfs_timestamp_info;
+
+	nsec = server->time_delta.tv_nsec;
+	nsec += server->time_delta.tv_sec * 1000000000ULL;
+	if (nsec == 0)
+		goto out;
+
+	do {
+		mant = nsec;
+		rem = do_div(nsec, 10);
+		if (rem)
+			break;
+		exp++;
+	} while (nsec);
+
+	r->atime.gran_mantissa = mant;
+	r->atime.gran_exponent = exp;
+	r->btime.gran_mantissa = mant;
+	r->btime.gran_exponent = exp;
+	r->ctime.gran_mantissa = mant;
+	r->ctime.gran_exponent = exp;
+	r->mtime.gran_mantissa = mant;
+	r->mtime.gran_exponent = exp;
+
+out:
+	return sizeof(*r);
+}
+
+static int nfs_fsinfo_get_info(struct path *path, struct fsinfo_context *ctx)
+{
+	const struct nfs_server *server = NFS_SB(path->dentry->d_sb);
+	const struct nfs_client *clp = server->nfs_client;
+	struct fsinfo_nfs_info *r = ctx->buffer;
+
+	r->version		= clp->rpc_ops->version;
+	r->minor_version	= clp->cl_minorversion;
+	r->transport_proto	= clp->cl_proto;
+	return sizeof(*r);
+}
+
+static int nfs_fsinfo_get_server_name(struct path *path, struct fsinfo_context *ctx)
+{
+	const struct nfs_server *server = NFS_SB(path->dentry->d_sb);
+	const struct nfs_client *clp = server->nfs_client;
+
+	return fsinfo_string(clp->cl_hostname, ctx);
+}
+
+static int nfs_fsinfo_get_server_addresses(struct path *path, struct fsinfo_context *ctx)
+{
+	const struct nfs_server *server = NFS_SB(path->dentry->d_sb);
+	const struct nfs_client *clp = server->nfs_client;
+	struct fsinfo_nfs_server_address *addr = ctx->buffer;
+	int ret;
+
+	ret = 1 * sizeof(*addr);
+	if (ret <= ctx->buf_size)
+		memcpy(&addr[0].address, &clp->cl_addr, clp->cl_addrlen);
+	return ret;
+
+}
+
+static int nfs_fsinfo_get_gssapi_name(struct path *path, struct fsinfo_context *ctx)
+{
+	const struct nfs_server *server = NFS_SB(path->dentry->d_sb);
+	const struct nfs_client *clp = server->nfs_client;
+
+	return fsinfo_string(clp->cl_acceptor, ctx);
+}
+
+static int nfs_fsinfo_get_limits(struct path *path, struct fsinfo_context *ctx)
+{
+	const struct nfs_server *server = NFS_SB(path->dentry->d_sb);
+	struct fsinfo_limits *lim = ctx->buffer;
+
+	lim->max_file_size.hi	= 0;
+	lim->max_file_size.lo	= server->maxfilesize;
+	lim->max_ino.hi		= 0;
+	lim->max_ino.lo		= U64_MAX;
+	lim->max_hard_links	= UINT_MAX;
+	lim->max_uid		= UINT_MAX;
+	lim->max_gid		= UINT_MAX;
+	lim->max_filename_len	= NAME_MAX - 1;
+	lim->max_symlink_len	= PATH_MAX - 1;
+	return sizeof(*lim);
+}
+
+static int nfs_fsinfo_get_supports(struct path *path, struct fsinfo_context *ctx)
+{
+	const struct nfs_server *server = NFS_SB(path->dentry->d_sb);
+	struct fsinfo_supports *sup = ctx->buffer;
+
+	/* Don't set STATX_INO as i_ino is fabricated and may not be unique. */
+
+	if (!(server->caps & NFS_CAP_MODE))
+		sup->stx_mask |= STATX_TYPE | STATX_MODE;
+	if (server->caps & NFS_CAP_OWNER)
+		sup->stx_mask |= STATX_UID;
+	if (server->caps & NFS_CAP_OWNER_GROUP)
+		sup->stx_mask |= STATX_GID;
+	if (server->caps & NFS_CAP_ATIME)
+		sup->stx_mask |= STATX_ATIME;
+	if (server->caps & NFS_CAP_CTIME)
+		sup->stx_mask |= STATX_CTIME;
+	if (server->caps & NFS_CAP_MTIME)
+		sup->stx_mask |= STATX_MTIME;
+	if (server->attr_bitmask[0] & FATTR4_WORD0_SIZE)
+		sup->stx_mask |= STATX_SIZE;
+	if (server->attr_bitmask[1] & FATTR4_WORD1_NUMLINKS)
+		sup->stx_mask |= STATX_NLINK;
+
+	if (server->attr_bitmask[0] & FATTR4_WORD0_ARCHIVE)
+		sup->win_file_attrs |= ATTR_ARCHIVE;
+	if (server->attr_bitmask[0] & FATTR4_WORD0_HIDDEN)
+		sup->win_file_attrs |= ATTR_HIDDEN;
+	if (server->attr_bitmask[1] & FATTR4_WORD1_SYSTEM)
+		sup->win_file_attrs |= ATTR_SYSTEM;
+
+	sup->stx_attributes = STATX_ATTR_AUTOMOUNT;
+	return sizeof(*sup);
+}
+
+static int nfs_fsinfo_get_features(struct path *path, struct fsinfo_context *ctx)
+{
+	const struct nfs_server *server = NFS_SB(path->dentry->d_sb);
+	struct fsinfo_features *ft = ctx->buffer;
+
+	fsinfo_set_feature(ft, FSINFO_FEAT_IS_NETWORK_FS);
+	fsinfo_set_feature(ft, FSINFO_FEAT_AUTOMOUNTS);
+	fsinfo_set_feature(ft, FSINFO_FEAT_O_SYNC);
+	fsinfo_set_feature(ft, FSINFO_FEAT_O_DIRECT);
+	fsinfo_set_feature(ft, FSINFO_FEAT_ADV_LOCKS);
+	fsinfo_set_feature(ft, FSINFO_FEAT_DEVICE_FILES);
+	fsinfo_set_feature(ft, FSINFO_FEAT_UNIX_SPECIALS);
+	if (server->nfs_client->rpc_ops->version == 4) {
+		fsinfo_set_feature(ft, FSINFO_FEAT_LEASES);
+		fsinfo_set_feature(ft, FSINFO_FEAT_IVER_ALL_CHANGE);
+	}
+
+	if (server->caps & NFS_CAP_OWNER)
+		fsinfo_set_feature(ft, FSINFO_FEAT_UIDS);
+	if (server->caps & NFS_CAP_OWNER_GROUP)
+		fsinfo_set_feature(ft, FSINFO_FEAT_GIDS);
+	if (!(server->caps & NFS_CAP_MODE))
+		fsinfo_set_feature(ft, FSINFO_FEAT_NO_UNIX_MODE);
+	if (server->caps & NFS_CAP_ACLS)
+		fsinfo_set_feature(ft, FSINFO_FEAT_HAS_ACL);
+	if (server->caps & NFS_CAP_SYMLINKS)
+		fsinfo_set_feature(ft, FSINFO_FEAT_SYMLINKS);
+	if (server->caps & NFS_CAP_HARDLINKS)
+		fsinfo_set_feature(ft, FSINFO_FEAT_HARD_LINKS);
+	if (server->caps & NFS_CAP_ATIME)
+		fsinfo_set_feature(ft, FSINFO_FEAT_HAS_ATIME);
+	if (server->caps & NFS_CAP_CTIME)
+		fsinfo_set_feature(ft, FSINFO_FEAT_HAS_CTIME);
+	if (server->caps & NFS_CAP_MTIME)
+		fsinfo_set_feature(ft, FSINFO_FEAT_HAS_MTIME);
+
+	if (server->attr_bitmask[0] & FATTR4_WORD0_CASE_INSENSITIVE)
+		fsinfo_set_feature(ft, FSINFO_FEAT_NAME_CASE_INDEP);
+	if ((server->attr_bitmask[0] & FATTR4_WORD0_ARCHIVE) ||
+	    (server->attr_bitmask[0] & FATTR4_WORD0_HIDDEN) ||
+	    (server->attr_bitmask[1] & FATTR4_WORD1_SYSTEM))
+		fsinfo_set_feature(ft, FSINFO_FEAT_WINDOWS_ATTRS);
+
+	return sizeof(*ft);
+}
+
+static const struct fsinfo_attribute nfs_fsinfo_attributes[] = {
+	FSINFO_VSTRUCT	(FSINFO_ATTR_TIMESTAMP_INFO,	nfs_fsinfo_get_timestamp_info),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_LIMITS,		nfs_fsinfo_get_limits),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_SUPPORTS,		nfs_fsinfo_get_supports),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_FEATURES,		nfs_fsinfo_get_features),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_NFS_INFO,		nfs_fsinfo_get_info),
+	FSINFO_STRING	(FSINFO_ATTR_NFS_SERVER_NAME,	nfs_fsinfo_get_server_name),
+	FSINFO_LIST	(FSINFO_ATTR_NFS_SERVER_ADDRESSES, nfs_fsinfo_get_server_addresses),
+	FSINFO_STRING	(FSINFO_ATTR_NFS_GSSAPI_NAME,	nfs_fsinfo_get_gssapi_name),
+	{}
+};
+
+int nfs_fsinfo(struct path *path, struct fsinfo_context *ctx)
+{
+	return fsinfo_get_attribute(path, ctx, nfs_fsinfo_attributes);
+}
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index f80c47d5ff27..59e407066b45 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -10,6 +10,7 @@
 #include <linux/sunrpc/addr.h>
 #include <linux/nfs_page.h>
 #include <linux/wait_bit.h>
+#include <linux/fsinfo.h>
 
 #define NFS_SB_MASK (SB_RDONLY|SB_NOSUID|SB_NODEV|SB_NOEXEC|SB_SYNCHRONOUS)
 
@@ -247,6 +248,11 @@ extern const struct svc_version nfs4_callback_version4;
 /* fs_context.c */
 extern struct file_system_type nfs_fs_type;
 
+/* fsinfo.c */
+#ifdef CONFIG_FSINFO
+extern int nfs_fsinfo(struct path *path, struct fsinfo_context *ctx);
+#endif
+
 /* pagelist.c */
 extern int __init nfs_init_nfspagecache(void);
 extern void nfs_destroy_nfspagecache(void);
diff --git a/fs/nfs/nfs4super.c b/fs/nfs/nfs4super.c
index 1475f932d7da..cd38da87cbd3 100644
--- a/fs/nfs/nfs4super.c
+++ b/fs/nfs/nfs4super.c
@@ -26,6 +26,9 @@ static const struct super_operations nfs4_sops = {
 	.write_inode	= nfs4_write_inode,
 	.drop_inode	= nfs_drop_inode,
 	.statfs		= nfs_statfs,
+#ifdef CONFIG_FSINFO
+	.fsinfo		= nfs_fsinfo,
+#endif
 	.evict_inode	= nfs4_evict_inode,
 	.umount_begin	= nfs_umount_begin,
 	.show_options	= nfs_show_options,
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index dada09b391c6..27ac751d3789 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -76,6 +76,9 @@ const struct super_operations nfs_sops = {
 	.write_inode	= nfs_write_inode,
 	.drop_inode	= nfs_drop_inode,
 	.statfs		= nfs_statfs,
+#ifdef CONFIG_FSINFO
+	.fsinfo		= nfs_fsinfo,
+#endif
 	.evict_inode	= nfs_evict_inode,
 	.umount_begin	= nfs_umount_begin,
 	.show_options	= nfs_show_options,
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 4cfb71227eff..80f1ae8bd17d 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -44,6 +44,11 @@
 
 #define FSINFO_ATTR_EXT4_TIMESTAMPS	0x400	/* Ext4 superblock timestamps */
 
+#define FSINFO_ATTR_NFS_INFO		0x500	/* Information about an NFS mount */
+#define FSINFO_ATTR_NFS_SERVER_NAME	0x501	/* Name of the server (string) */
+#define FSINFO_ATTR_NFS_SERVER_ADDRESSES 0x502	/* List of addresses of the server */
+#define FSINFO_ATTR_NFS_GSSAPI_NAME	0x503	/* GSSAPI acceptor name */
+
 /*
  * Optional fsinfo() parameter structure.
  *
@@ -339,4 +344,28 @@ struct fsinfo_ext4_timestamps {
 
 #define FSINFO_ATTR_EXT4_TIMESTAMPS__STRUCT struct fsinfo_ext4_timestamps
 
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_NFS_INFO).
+ *
+ * Get information about an NFS mount.
+ */
+struct fsinfo_nfs_info {
+	__u32		version;
+	__u32		minor_version;
+	__u32		transport_proto;
+};
+
+#define FSINFO_ATTR_NFS_INFO__STRUCT struct fsinfo_nfs_info
+
+/*
+ * Information struct for fsinfo(FSINFO_ATTR_NFS_SERVER_ADDRESSES).
+ *
+ * Get the addresses of the server for an NFS mount.
+ */
+struct fsinfo_nfs_server_address {
+	struct __kernel_sockaddr_storage address;
+};
+
+#define FSINFO_ATTR_NFS_SERVER_ADDRESSES__STRUCT struct fsinfo_nfs_server_address
+
 #endif /* _UAPI_LINUX_FSINFO_H */
diff --git a/include/uapi/linux/windows.h b/include/uapi/linux/windows.h
new file mode 100644
index 000000000000..17efb9a40529
--- /dev/null
+++ b/include/uapi/linux/windows.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Common windows attributes
+ */
+#ifndef _UAPI_LINUX_WINDOWS_H
+#define _UAPI_LINUX_WINDOWS_H
+
+/*
+ * File Attribute flags
+ */
+#define ATTR_READONLY		0x0001
+#define ATTR_HIDDEN		0x0002
+#define ATTR_SYSTEM		0x0004
+#define ATTR_VOLUME		0x0008
+#define ATTR_DIRECTORY		0x0010
+#define ATTR_ARCHIVE		0x0020
+#define ATTR_DEVICE		0x0040
+#define ATTR_NORMAL		0x0080
+#define ATTR_TEMPORARY		0x0100
+#define ATTR_SPARSE		0x0200
+#define ATTR_REPARSE		0x0400
+#define ATTR_COMPRESSED		0x0800
+#define ATTR_OFFLINE		0x1000	/* ie file not immediately available -
+					   on offline storage */
+#define ATTR_NOT_CONTENT_INDEXED 0x2000
+#define ATTR_ENCRYPTED		0x4000
+#define ATTR_POSIX_SEMANTICS	0x01000000
+#define ATTR_BACKUP_SEMANTICS	0x02000000
+#define ATTR_DELETE_ON_CLOSE	0x04000000
+#define ATTR_SEQUENTIAL_SCAN	0x08000000
+#define ATTR_RANDOM_ACCESS	0x10000000
+#define ATTR_NO_BUFFERING	0x20000000
+#define ATTR_WRITE_THROUGH	0x80000000
+
+#endif /* _UAPI_LINUX_WINDOWS_H */
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index 6ad1128a3e1d..8e19cdc18d91 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -418,6 +418,40 @@ static void dump_ext4_fsinfo_timestamps(void *reply, unsigned int size)
 	printf("\tlast-err: %s\n", dump_ext4_time(buffer, r->last_error_time));
 }
 
+static void dump_nfs_fsinfo_info(void *reply, unsigned int size)
+{
+	struct fsinfo_nfs_info *r = reply;
+
+	printf("ver=%u.%u proto=%u\n", r->version, r->minor_version, r->transport_proto);
+}
+
+static void dump_nfs_fsinfo_server_addresses(void *reply, unsigned int size)
+{
+	struct fsinfo_nfs_server_address *r = reply;
+	struct sockaddr_storage *ss = (struct sockaddr_storage *)&r->address;
+	struct sockaddr_in6 *sin6;
+	struct sockaddr_in *sin;
+	char buf[1024];
+
+	switch (ss->ss_family) {
+	case AF_INET:
+		sin = (struct sockaddr_in *)ss;
+		if (!inet_ntop(AF_INET, &sin->sin_addr, buf, sizeof(buf)))
+			break;
+		printf("%5u %s\n", ntohs(sin->sin_port), buf);
+		return;
+	case AF_INET6:
+		sin6 = (struct sockaddr_in6 *)ss;
+		if (!inet_ntop(AF_INET6, &sin6->sin6_addr, buf, sizeof(buf)))
+			break;
+		printf("%5u %s\n", ntohs(sin6->sin6_port), buf);
+		return;
+	default:
+		printf("family=%u\n", ss->ss_family);
+		return;
+	}
+}
+
 static void dump_string(void *reply, unsigned int size)
 {
 	char *s = reply, *p;
@@ -506,6 +540,10 @@ static const struct fsinfo_attribute fsinfo_attributes[] = {
 	FSINFO_STRING	(FSINFO_ATTR_AFS_SERVER_NAME,	string),
 	FSINFO_LIST_N	(FSINFO_ATTR_AFS_SERVER_ADDRESSES, afs_fsinfo_server_address),
 	FSINFO_VSTRUCT	(FSINFO_ATTR_EXT4_TIMESTAMPS,	ext4_fsinfo_timestamps),
+	FSINFO_VSTRUCT	(FSINFO_ATTR_NFS_INFO,		nfs_fsinfo_info),
+	FSINFO_STRING	(FSINFO_ATTR_NFS_SERVER_NAME,	string),
+	FSINFO_LIST	(FSINFO_ATTR_NFS_SERVER_ADDRESSES, nfs_fsinfo_server_addresses),
+	FSINFO_STRING	(FSINFO_ATTR_NFS_GSSAPI_NAME,	string),
 	{}
 };
 



^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (12 preceding siblings ...)
  2020-03-18 15:10 ` [PATCH 13/13] fsinfo: Example support for NFS " David Howells
@ 2020-03-18 16:05 ` Miklos Szeredi
  2020-04-01  5:22   ` Ian Kent
  2020-03-19 10:37 ` David Howells
  14 siblings, 1 reply; 25+ messages in thread
From: Miklos Szeredi @ 2020-03-18 16:05 UTC (permalink / raw)
  To: David Howells
  Cc: Linus Torvalds, Al Viro, Linux NFS list, Andreas Dilger,
	Anna Schumaker, Theodore Ts'o, Linux API, linux-ext4,
	Trond Myklebust, Ian Kent, Miklos Szeredi, Christian Brauner,
	Jann Horn, Darrick J. Wong, Karel Zak, Jeff Layton,
	linux-fsdevel, LSM, linux-kernel

On Wed, Mar 18, 2020 at 4:08 PM David Howells <dhowells@redhat.com> wrote:

> ============================
> WHY NOT USE PROCFS OR SYSFS?
> ============================
>
> Why is it better to go with a new system call rather than adding more magic
> stuff to /proc or /sysfs for each superblock object and each mount object?
>
>  (1) It can be targetted.  It makes it easy to query directly by path.
>      procfs and sysfs cannot do this easily.
>
>  (2) It's more efficient as we can return specific binary data rather than
>      making huge text dumps.  Granted, sysfs and procfs could present the
>      same data, though as lots of little files which have to be
>      individually opened, read, closed and parsed.

Asked this a number of times, but you haven't answered yet:  what
application would require such a high efficiency?

Nobody's suggesting we move stat(2) to proc interfaces, and AFAIK
nobody suggested we move /proc/PID/* to a binary syscall interface.
Each one has its place, and I strongly feel that mount info belongs in
the latter category.    Feel free to prove the opposite.

>  (3) We wouldn't have the overhead of open and close (even adding a
>      self-contained readfile() syscall has to do that internally

Busted: add f_op->readfile() and be done with all that.   For example
DEFINE_SHOW_ATTRIBUTE() could be trivially moved to that interface.

We could optimize existing proc, sys, etc. interfaces, but it's not
been an issue, apparently.

>
>  (4) Opening a file in procfs or sysfs has a pathwalk overhead for each
>      file accessed.  We can use an integer attribute ID instead (yes, this
>      is similar to ioctl) - but could also use a string ID if that is
>      preferred.
>
>  (5) Can easily query cross-namespace if, say, a container manager process
>      is given an fs_context that hasn't yet been mounted into a namespace -
>      or hasn't even been fully created yet.

Works with my patch.

>  (6) Don't have to create/delete a bunch of sysfs/procfs nodes each time a
>      mount happens or is removed - and since systemd makes much use of
>      mount namespaces and mount propagation, this will create a lot of
>      nodes.

Not true.

> The argument for doing this through procfs/sysfs/somemagicfs is that
> someone using a shell can just query the magic files using ordinary text
> tools, such as cat - and that has merit - but it doesn't solve the
> query-by-pathname problem.
>
> The suggested way around the query-by-pathname problem is to open the
> target file O_PATH and then look in a magic directory under procfs
> corresponding to the fd number to see a set of attribute files[*] laid out.
> Bash, however, can't open by O_PATH or O_NOFOLLOW as things stand...

Bash doesn't have fsinfo(2) either, so that's not really a good argument.

Implementing a utility to show mount attribute(s) by path is trivial
for the file based interface, while it would need to be updated for
each extension of fsinfo(2).   Same goes for libc, language bindings,
etc.

Thanks,
Miklos

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
  2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
                   ` (13 preceding siblings ...)
  2020-03-18 16:05 ` [PATCH 00/13] VFS: Filesystem information " Miklos Szeredi
@ 2020-03-19 10:37 ` David Howells
  2020-03-19 12:36   ` Miklos Szeredi
  14 siblings, 1 reply; 25+ messages in thread
From: David Howells @ 2020-03-19 10:37 UTC (permalink / raw)
  To: Miklos Szeredi
  Cc: dhowells, Linus Torvalds, Al Viro, Linux NFS list,
	Andreas Dilger, Anna Schumaker, Theodore Ts'o, Linux API,
	linux-ext4, Trond Myklebust, Ian Kent, Miklos Szeredi,
	Christian Brauner, Jann Horn, Darrick J. Wong, Karel Zak,
	Jeff Layton, linux-fsdevel, LSM, linux-kernel

Miklos Szeredi <miklos@szeredi.hu> wrote:

> >  (2) It's more efficient as we can return specific binary data rather than
> >      making huge text dumps.  Granted, sysfs and procfs could present the
> >      same data, though as lots of little files which have to be
> >      individually opened, read, closed and parsed.
> 
> Asked this a number of times, but you haven't answered yet:  what
> application would require such a high efficiency?

Low efficiency means more time doing this when that time could be spent doing
other things - or even putting the CPU in a powersaving state.  Using an
open/read/close render-to-text-and-parse interface *will* be slower and less
efficient as there are more things you have to do to use it.

Then consider doing a walk over all the mounts in the case where there are
10000 of them - we have issues with /proc/mounts for such.  fsinfo() will end
up doing a lot less work.

> I strongly feel that mount info belongs in the latter category

I feel strongly that a lot of stuff done through /proc or /sys shouldn't be.

Yes, it's nice that you can explore it with cat and poke it with echo, but it
has a number of problems: security, atomiticity, efficiency and providing an
round-the-back way to pin stuff if not done right.

> >  (3) We wouldn't have the overhead of open and close (even adding a
> >      self-contained readfile() syscall has to do that internally
> 
> Busted: add f_op->readfile() and be done with all that.   For example
> DEFINE_SHOW_ATTRIBUTE() could be trivially moved to that interface.

Look at your example.  "f_op->".  That's "file->f_op->" I presume.

You would have to make it "i_op->" to avoid the open and the close - and for
things like procfs and sysfs, that's probably entirely reasonable - but bear
in mind that you still have to apply all the LSM file security controls, just
in case the backing filesystem is, say, ext4 rather than procfs.

> We could optimize existing proc, sys, etc. interfaces, but it's not
> been an issue, apparently.

You can't get rid of or change many of the existing interfaces.  A lot of them
are effectively indirect system calls and are, as such, part of the fixed
UAPI.  You'd have to add a parallel optimised set.

> >  (6) Don't have to create/delete a bunch of sysfs/procfs nodes each time a
> >      mount happens or is removed - and since systemd makes much use of
> >      mount namespaces and mount propagation, this will create a lot of
> >      nodes.
> 
> Not true.

This may not be true if you roll your own special filesystem.  It *is* true if
you do it in procfs or sysfs.  The files don't exist if you don't create nodes
or attribute tables for them.

> > The argument for doing this through procfs/sysfs/somemagicfs is that
> > someone using a shell can just query the magic files using ordinary text
> > tools, such as cat - and that has merit - but it doesn't solve the
> > query-by-pathname problem.
> >
> > The suggested way around the query-by-pathname problem is to open the
> > target file O_PATH and then look in a magic directory under procfs
> > corresponding to the fd number to see a set of attribute files[*] laid out.
> > Bash, however, can't open by O_PATH or O_NOFOLLOW as things stand...
> 
> Bash doesn't have fsinfo(2) either, so that's not really a good argument.

I never claimed that fsinfo() could be accessed directly from the shell.  For
you proposal, you claimed "immediately usable from all programming languages,
including scripts".

> Implementing a utility to show mount attribute(s) by path is trivial
> for the file based interface, while it would need to be updated for
> each extension of fsinfo(2).   Same goes for libc, language bindings,
> etc.

That's not precisely true.  If you aren't using an extension to an fsinfo()
attribute, you wouldn't need to change anything[*].

If you want to use an extension - *even* through a file based interface - you
*would* have to change your code and your parser.

And, no, extending an fsinfo() attribute would not require any changes to libc
unless libc is using that attribute[*] and wants to access the extension.

[*] I assume that in C/C++ at least, you'd use linux/fsinfo.h rather than some
    libc version.

[*] statfs() could be emulated this way, but I'm not sure what else libc
    specifically is going to look at.  This is more aimed at libmount amongst
    other things.

David


^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
  2020-03-19 10:37 ` David Howells
@ 2020-03-19 12:36   ` Miklos Szeredi
  0 siblings, 0 replies; 25+ messages in thread
From: Miklos Szeredi @ 2020-03-19 12:36 UTC (permalink / raw)
  To: David Howells
  Cc: Linus Torvalds, Al Viro, Linux NFS list, Andreas Dilger,
	Anna Schumaker, Theodore Ts'o, Linux API, linux-ext4,
	Trond Myklebust, Ian Kent, Miklos Szeredi, Christian Brauner,
	Jann Horn, Darrick J. Wong, Karel Zak, Jeff Layton,
	linux-fsdevel, LSM, linux-kernel

On Thu, Mar 19, 2020 at 11:37 AM David Howells <dhowells@redhat.com> wrote:
>
> Miklos Szeredi <miklos@szeredi.hu> wrote:
>
> > >  (2) It's more efficient as we can return specific binary data rather than
> > >      making huge text dumps.  Granted, sysfs and procfs could present the
> > >      same data, though as lots of little files which have to be
> > >      individually opened, read, closed and parsed.
> >
> > Asked this a number of times, but you haven't answered yet:  what
> > application would require such a high efficiency?
>
> Low efficiency means more time doing this when that time could be spent doing
> other things - or even putting the CPU in a powersaving state.  Using an
> open/read/close render-to-text-and-parse interface *will* be slower and less
> efficient as there are more things you have to do to use it.
>
> Then consider doing a walk over all the mounts in the case where there are
> 10000 of them - we have issues with /proc/mounts for such.  fsinfo() will end
> up doing a lot less work.

Current /proc/mounts problems arise from the fact that mount info can
only be queried for the whole namespace, and hence changes related to
a single mount will require rescanning the complete mount list.  If
mount info can be queried for individual mounts, then the need to scan
the complete list will be rare.  That's *the* point of this change.

> > >  (3) We wouldn't have the overhead of open and close (even adding a
> > >      self-contained readfile() syscall has to do that internally
> >
> > Busted: add f_op->readfile() and be done with all that.   For example
> > DEFINE_SHOW_ATTRIBUTE() could be trivially moved to that interface.
>
> Look at your example.  "f_op->".  That's "file->f_op->" I presume.
>
> You would have to make it "i_op->" to avoid the open and the close - and for
> things like procfs and sysfs, that's probably entirely reasonable - but bear
> in mind that you still have to apply all the LSM file security controls, just
> in case the backing filesystem is, say, ext4 rather than procfs.
>
> > We could optimize existing proc, sys, etc. interfaces, but it's not
> > been an issue, apparently.
>
> You can't get rid of or change many of the existing interfaces.  A lot of them
> are effectively indirect system calls and are, as such, part of the fixed
> UAPI.  You'd have to add a parallel optimised set.

Sure.

We already have the single_open() internal API that is basically a
->readfile() wrapper.   Moving this up to the f_op level (no, it's not
an i_op, and yes, we do need struct file, but it can be simply
allocated on the stack) is a trivial optimization that would let a
readfile(2) syscall access that level.  No new complexity in that
case.    Same generally goes for seq_file: seq_readfile() is trivial
to implement without messing with current implementation or any
existing APIs.

>
> > >  (6) Don't have to create/delete a bunch of sysfs/procfs nodes each time a
> > >      mount happens or is removed - and since systemd makes much use of
> > >      mount namespaces and mount propagation, this will create a lot of
> > >      nodes.
> >
> > Not true.
>
> This may not be true if you roll your own special filesystem.  It *is* true if
> you do it in procfs or sysfs.  The files don't exist if you don't create nodes
> or attribute tables for them.

That's one of the reasons why I opted to roll my own.  But the ideas
therein could be applied to kernfs, if found to be generally useful.
Nothing magic about that.

>
> > > The argument for doing this through procfs/sysfs/somemagicfs is that
> > > someone using a shell can just query the magic files using ordinary text
> > > tools, such as cat - and that has merit - but it doesn't solve the
> > > query-by-pathname problem.
> > >
> > > The suggested way around the query-by-pathname problem is to open the
> > > target file O_PATH and then look in a magic directory under procfs
> > > corresponding to the fd number to see a set of attribute files[*] laid out.
> > > Bash, however, can't open by O_PATH or O_NOFOLLOW as things stand...
> >
> > Bash doesn't have fsinfo(2) either, so that's not really a good argument.
>
> I never claimed that fsinfo() could be accessed directly from the shell.  For
> you proposal, you claimed "immediately usable from all programming languages,
> including scripts".

You are right.  Note however: only special files need the O_PATH
handling, regular files are directories can be opened by the shell
without side effects.

In any case, I think neither of us can be convinced of the other's
right, so I guess It's up to Al and Linus to make a decision.

Thanks,
Miklos

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
  2020-03-18 16:05 ` [PATCH 00/13] VFS: Filesystem information " Miklos Szeredi
@ 2020-04-01  5:22   ` Ian Kent
  2020-04-01  8:18     ` Miklos Szeredi
  2020-04-01  8:27     ` David Howells
  0 siblings, 2 replies; 25+ messages in thread
From: Ian Kent @ 2020-04-01  5:22 UTC (permalink / raw)
  To: Miklos Szeredi, David Howells
  Cc: Linus Torvalds, Al Viro, Linux NFS list, Andreas Dilger,
	Anna Schumaker, Theodore Ts'o, Linux API, linux-ext4,
	Trond Myklebust, Miklos Szeredi, Christian Brauner, Jann Horn,
	Darrick J. Wong, Karel Zak, Jeff Layton, linux-fsdevel, LSM,
	linux-kernel

On Wed, 2020-03-18 at 17:05 +0100, Miklos Szeredi wrote:
> On Wed, Mar 18, 2020 at 4:08 PM David Howells <dhowells@redhat.com>
> wrote:
> 
> > ============================
> > WHY NOT USE PROCFS OR SYSFS?
> > ============================
> > 
> > Why is it better to go with a new system call rather than adding
> > more magic
> > stuff to /proc or /sysfs for each superblock object and each mount
> > object?
> > 
> >  (1) It can be targetted.  It makes it easy to query directly by
> > path.
> >      procfs and sysfs cannot do this easily.
> > 
> >  (2) It's more efficient as we can return specific binary data
> > rather than
> >      making huge text dumps.  Granted, sysfs and procfs could
> > present the
> >      same data, though as lots of little files which have to be
> >      individually opened, read, closed and parsed.
> 
> Asked this a number of times, but you haven't answered yet:  what
> application would require such a high efficiency?

Umm ... systemd and udisks2 and about 4 others.

A problem I've had with autofs for years is using autofs direct mount
maps of any appreciable size cause several key user space applications
to consume all available CPU while autofs is starting or stopping which
takes a fair while with a very large mount table. I saw a couple of
applications affected purely because of the large mount table but not
as badly as starting or stopping autofs.

Maps of 5,000 to 10,000 map entries can almost be handled, not uncommon
for heavy autofs users in spite of the problem, but much larger than
that and you've got a serious problem.

There are problems with expiration as well but that's more an autofs
problem that I need to fix.

To be clear it's not autofs that needs the improvement (I need to
deal with this in autofs itself) it's the affect that these large
mount tables have on the rest of the user space and that's quite
significant.

I can't even think about resolving my autofs problem until this
problem is resolved and handling very large numbers of mounts
as efficiently as possible must be part of that solution for me
and I think for the OS overall too.

Ian
> 
> Nobody's suggesting we move stat(2) to proc interfaces, and AFAIK
> nobody suggested we move /proc/PID/* to a binary syscall interface.
> Each one has its place, and I strongly feel that mount info belongs
> in
> the latter category.    Feel free to prove the opposite.
> 
> >  (3) We wouldn't have the overhead of open and close (even adding a
> >      self-contained readfile() syscall has to do that internally
> 
> Busted: add f_op->readfile() and be done with all that.   For example
> DEFINE_SHOW_ATTRIBUTE() could be trivially moved to that interface.
> 
> We could optimize existing proc, sys, etc. interfaces, but it's not
> been an issue, apparently.
> 
> >  (4) Opening a file in procfs or sysfs has a pathwalk overhead for
> > each
> >      file accessed.  We can use an integer attribute ID instead
> > (yes, this
> >      is similar to ioctl) - but could also use a string ID if that
> > is
> >      preferred.
> > 
> >  (5) Can easily query cross-namespace if, say, a container manager
> > process
> >      is given an fs_context that hasn't yet been mounted into a
> > namespace -
> >      or hasn't even been fully created yet.
> 
> Works with my patch.
> 
> >  (6) Don't have to create/delete a bunch of sysfs/procfs nodes each
> > time a
> >      mount happens or is removed - and since systemd makes much use
> > of
> >      mount namespaces and mount propagation, this will create a lot
> > of
> >      nodes.
> 
> Not true.
> 
> > The argument for doing this through procfs/sysfs/somemagicfs is
> > that
> > someone using a shell can just query the magic files using ordinary
> > text
> > tools, such as cat - and that has merit - but it doesn't solve the
> > query-by-pathname problem.
> > 
> > The suggested way around the query-by-pathname problem is to open
> > the
> > target file O_PATH and then look in a magic directory under procfs
> > corresponding to the fd number to see a set of attribute files[*]
> > laid out.
> > Bash, however, can't open by O_PATH or O_NOFOLLOW as things
> > stand...
> 
> Bash doesn't have fsinfo(2) either, so that's not really a good
> argument.
> 
> Implementing a utility to show mount attribute(s) by path is trivial
> for the file based interface, while it would need to be updated for
> each extension of fsinfo(2).   Same goes for libc, language bindings,
> etc.
> 
> Thanks,
> Miklos


^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
  2020-04-01  5:22   ` Ian Kent
@ 2020-04-01  8:18     ` Miklos Szeredi
  2020-04-01  8:27     ` David Howells
  1 sibling, 0 replies; 25+ messages in thread
From: Miklos Szeredi @ 2020-04-01  8:18 UTC (permalink / raw)
  To: Ian Kent
  Cc: David Howells, Linus Torvalds, Al Viro, Linux NFS list,
	Andreas Dilger, Anna Schumaker, Theodore Ts'o, Linux API,
	linux-ext4, Trond Myklebust, Miklos Szeredi, Christian Brauner,
	Jann Horn, Darrick J. Wong, Karel Zak, Jeff Layton,
	linux-fsdevel, LSM, linux-kernel

On Wed, Apr 1, 2020 at 7:22 AM Ian Kent <raven@themaw.net> wrote:
>
> On Wed, 2020-03-18 at 17:05 +0100, Miklos Szeredi wrote:
> > On Wed, Mar 18, 2020 at 4:08 PM David Howells <dhowells@redhat.com>
> > wrote:
> >
> > > ============================
> > > WHY NOT USE PROCFS OR SYSFS?
> > > ============================
> > >
> > > Why is it better to go with a new system call rather than adding
> > > more magic
> > > stuff to /proc or /sysfs for each superblock object and each mount
> > > object?
> > >
> > >  (1) It can be targetted.  It makes it easy to query directly by
> > > path.
> > >      procfs and sysfs cannot do this easily.
> > >
> > >  (2) It's more efficient as we can return specific binary data
> > > rather than
> > >      making huge text dumps.  Granted, sysfs and procfs could
> > > present the
> > >      same data, though as lots of little files which have to be
> > >      individually opened, read, closed and parsed.
> >
> > Asked this a number of times, but you haven't answered yet:  what
> > application would require such a high efficiency?
>
> Umm ... systemd and udisks2 and about 4 others.
>
> A problem I've had with autofs for years is using autofs direct mount
> maps of any appreciable size cause several key user space applications
> to consume all available CPU while autofs is starting or stopping which
> takes a fair while with a very large mount table. I saw a couple of
> applications affected purely because of the large mount table but not
> as badly as starting or stopping autofs.
>
> Maps of 5,000 to 10,000 map entries can almost be handled, not uncommon
> for heavy autofs users in spite of the problem, but much larger than
> that and you've got a serious problem.
>
> There are problems with expiration as well but that's more an autofs
> problem that I need to fix.
>
> To be clear it's not autofs that needs the improvement (I need to
> deal with this in autofs itself) it's the affect that these large
> mount tables have on the rest of the user space and that's quite
> significant.


According to dhowell's measurements processing 100k mounts would take
about a few seconds of system time (that's the time spent by the
kernel to retrieve the data, obviously the userspace processing would
add to that, but that's independent of the kernel patchset).  I think
that sort of time spent by the kernel is entirely reasonable and is
probably not worth heavy optimization, since userspace is probably
going to spend as much, if not more time with each mount entry.

> I can't even think about resolving my autofs problem until this
> problem is resolved and handling very large numbers of mounts
> as efficiently as possible must be part of that solution for me
> and I think for the OS overall too.

The key to that is allowing userspace to retrieve individual mount
entries instead of having to parse the complete mount table on every
change.

Thanks,
Miklos

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
  2020-04-01  5:22   ` Ian Kent
  2020-04-01  8:18     ` Miklos Szeredi
@ 2020-04-01  8:27     ` David Howells
  2020-04-01  8:37       ` Miklos Szeredi
  1 sibling, 1 reply; 25+ messages in thread
From: David Howells @ 2020-04-01  8:27 UTC (permalink / raw)
  To: Miklos Szeredi
  Cc: dhowells, Ian Kent, Linus Torvalds, Al Viro, Linux NFS list,
	Andreas Dilger, Anna Schumaker, Theodore Ts'o, Linux API,
	linux-ext4, Trond Myklebust, Miklos Szeredi, Christian Brauner,
	Jann Horn, Darrick J. Wong, Karel Zak, Jeff Layton,
	linux-fsdevel, LSM, linux-kernel

Miklos Szeredi <miklos@szeredi.hu> wrote:

> According to dhowell's measurements processing 100k mounts would take
> about a few seconds of system time (that's the time spent by the
> kernel to retrieve the data,

But the inefficiency of mountfs - at least as currently implemented - scales
up with the number of individual values you want to retrieve, both in terms of
memory usage and time taken.

With fsinfo(), I've tried to batch values together where it makes sense - and
there's no lingering memory overhead - no extra inodes, dentries and files
required.

David


^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
  2020-04-01  8:27     ` David Howells
@ 2020-04-01  8:37       ` Miklos Szeredi
  2020-04-01 12:35         ` Miklos Szeredi
                           ` (2 more replies)
  0 siblings, 3 replies; 25+ messages in thread
From: Miklos Szeredi @ 2020-04-01  8:37 UTC (permalink / raw)
  To: David Howells
  Cc: Ian Kent, Linus Torvalds, Al Viro, Linux NFS list,
	Andreas Dilger, Anna Schumaker, Theodore Ts'o, Linux API,
	linux-ext4, Trond Myklebust, Miklos Szeredi, Christian Brauner,
	Jann Horn, Darrick J. Wong, Karel Zak, Jeff Layton,
	linux-fsdevel, LSM, linux-kernel

On Wed, Apr 1, 2020 at 10:27 AM David Howells <dhowells@redhat.com> wrote:
>
> Miklos Szeredi <miklos@szeredi.hu> wrote:
>
> > According to dhowell's measurements processing 100k mounts would take
> > about a few seconds of system time (that's the time spent by the
> > kernel to retrieve the data,
>
> But the inefficiency of mountfs - at least as currently implemented - scales
> up with the number of individual values you want to retrieve, both in terms of
> memory usage and time taken.

I've taken that into account when guesstimating a "few seconds per
100k entries".  My guess is that there's probably an order of
magnitude difference between the performance of a fs based interface
and a binary syscall based interface.  That could be reduced somewhat
with a readfile(2) type API.

But the point is: this does not matter.  Whether it's .5s or 5s is
completely irrelevant, as neither is going to take down the system,
and userspace processing is probably going to take as much, if not
more time.  And remember, we are talking about stopping and starting
the automount daemon, which is something that happens, but it should
not happen often by any measure.

> With fsinfo(), I've tried to batch values together where it makes sense - and
> there's no lingering memory overhead - no extra inodes, dentries and files
> required.

The dentries, inodes and files in your test are single use (except the
root dentry) and can be made ephemeral if that turns out to be better.
My guess is that dentries belonging to individual attributes should be
deleted on final put, while the dentries belonging to the mount
directory can be reclaimed normally.

Thanks,
Miklos

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
  2020-04-01  8:37       ` Miklos Szeredi
@ 2020-04-01 12:35         ` Miklos Szeredi
  2020-04-01 15:51         ` David Howells
  2020-04-02  1:38         ` Ian Kent
  2 siblings, 0 replies; 25+ messages in thread
From: Miklos Szeredi @ 2020-04-01 12:35 UTC (permalink / raw)
  To: David Howells
  Cc: Ian Kent, Linus Torvalds, Al Viro, Linux NFS list,
	Andreas Dilger, Anna Schumaker, Theodore Ts'o, Linux API,
	linux-ext4, Trond Myklebust, Miklos Szeredi, Christian Brauner,
	Jann Horn, Darrick J. Wong, Karel Zak, Jeff Layton,
	linux-fsdevel, LSM, linux-kernel

[-- Attachment #1: Type: text/plain, Size: 1618 bytes --]

On Wed, Apr 1, 2020 at 10:37 AM Miklos Szeredi <miklos@szeredi.hu> wrote:
>
> On Wed, Apr 1, 2020 at 10:27 AM David Howells <dhowells@redhat.com> wrote:
> >
> > Miklos Szeredi <miklos@szeredi.hu> wrote:
> >
> > > According to dhowell's measurements processing 100k mounts would take
> > > about a few seconds of system time (that's the time spent by the
> > > kernel to retrieve the data,
> >
> > But the inefficiency of mountfs - at least as currently implemented - scales
> > up with the number of individual values you want to retrieve, both in terms of
> > memory usage and time taken.
>
> I've taken that into account when guesstimating a "few seconds per
> 100k entries".  My guess is that there's probably an order of
> magnitude difference between the performance of a fs based interface
> and a binary syscall based interface.  That could be reduced somewhat
> with a readfile(2) type API.

And to show that I'm not completely off base, attached a patch that
adds a limited readfile(2) syscall and uses it in the p2 method.

Results are promising:

./test-fsinfo-perf /tmp/a 30000
--- make mounts ---
--- test fsinfo by path ---
sum(mnt_id) = 930000
--- test fsinfo by mnt_id ---
sum(mnt_id) = 930000
--- test /proc/fdinfo ---
sum(mnt_id) = 930000
--- test mountfs ---
sum(mnt_id) = 930000
For   30000 mounts, f=    146400us f2=    136766us p=   1406569us p2=
  221669us; p=9.6*f p=10.3*f2 p=6.3*p2
--- umount ---

This is about a 2 fold increase in speed compared to open + read + close.

Is someone still worried about performance, or can we move on to more
interesting parts of the design?

Thanks,
Miklos

[-- Attachment #2: fsmount-readfile.patch --]
[-- Type: text/x-patch, Size: 6326 bytes --]

Index: linux/fs/mountfs/super.c
===================================================================
--- linux.orig/fs/mountfs/super.c	2020-04-01 14:21:24.609955072 +0200
+++ linux/fs/mountfs/super.c	2020-04-01 14:21:42.426151545 +0200
@@ -51,10 +51,11 @@ static bool mountfs_entry_visible(struct
 
 	return visible;
 }
+
 static int mountfs_attr_show(struct seq_file *sf, void *v)
 {
 	const char *name = sf->file->f_path.dentry->d_name.name;
-	struct mountfs_entry *entry = sf->private;
+	struct mountfs_entry *entry = file_inode(sf->file)->i_private;
 	struct mount *mnt;
 	struct vfsmount *m;
 	struct super_block *sb;
@@ -140,12 +141,40 @@ static int mountfs_attr_show(struct seq_
 	return err;
 }
 
+ssize_t mountfs_attr_readfile(struct file *file, char __user *buf, size_t size)
+{
+	struct seq_file m = { .size = PAGE_SIZE, .file = file };
+	ssize_t ret;
+
+retry:
+	m.buf = kvmalloc(m.size, GFP_KERNEL);
+	if (!m.buf)
+		return -ENOMEM;
+
+	ret = mountfs_attr_show(&m, NULL);
+	if (!ret) {
+		if (m.count == m.size) {
+			kvfree(m.buf);
+			m.size <<= 1;
+			m.count = 0;
+			goto retry;
+		}
+		ret = min(m.count, size);
+		if (copy_to_user(buf, m.buf, ret))
+			ret = -EFAULT;
+	}
+
+	kvfree(m.buf);
+	return ret;
+}
+
 static int mountfs_attr_open(struct inode *inode, struct file *file)
 {
-	return single_open(file, mountfs_attr_show, inode->i_private);
+	return single_open(file, mountfs_attr_show, NULL);
 }
 
 static const struct file_operations mountfs_attr_fops = {
+	.readfile	= mountfs_attr_readfile,
 	.open		= mountfs_attr_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
Index: linux/samples/vfs/test-fsinfo-perf.c
===================================================================
--- linux.orig/samples/vfs/test-fsinfo-perf.c	2020-04-01 14:21:24.609955072 +0200
+++ linux/samples/vfs/test-fsinfo-perf.c	2020-04-01 14:21:42.426151545 +0200
@@ -172,6 +172,12 @@ static void get_id_by_proc(int ix, const
 	//printf("[%u] %u\n", ix, x);
 }
 
+static long readfile(int dfd, const char *name, char *buffer, size_t size,
+		     int flags)
+{
+	return syscall(__NR_readfile, dfd, name, buffer, size, flags);
+}
+
 static void get_id_by_fsinfo_2(void)
 {
 	struct fsinfo_mount_topology t;
@@ -300,11 +306,8 @@ static void get_id_by_mountfs(void)
 		}
 
 		sprintf(procfile, "%u/parent", mnt_id);
-		fd = openat(mntfd, procfile, O_RDONLY);
-		ERR(fd, procfile);
-		len = read(fd, buffer, sizeof(buffer) - 1);
-		ERR(len, "read/parent");
-		close(fd);
+		len = readfile(mntfd, procfile, buffer, sizeof(buffer), 0);
+		ERR(len, "readfile/parent");
 		if (len > 0 && buffer[len - 1] == '\n')
 			len--;
 		buffer[len] = 0;
@@ -319,11 +322,8 @@ static void get_id_by_mountfs(void)
 		sum_check += x;
 
 		sprintf(procfile, "%u/counter", mnt_id);
-		fd = openat(mntfd, procfile, O_RDONLY);
-		ERR(fd, procfile);
-		len = read(fd, buffer, sizeof(buffer) - 1);
-		ERR(len, "read/counter");
-		close(fd);
+		len = readfile(mntfd, procfile, buffer, sizeof(buffer) - 1, 0);
+		ERR(len, "readfile/counter");
 		if (len > 0 && buffer[len - 1] == '\n')
 			len--;
 		buffer[len] = 0;
Index: linux/arch/x86/entry/syscalls/syscall_64.tbl
===================================================================
--- linux.orig/arch/x86/entry/syscalls/syscall_64.tbl	2020-04-01 14:21:37.284094840 +0200
+++ linux/arch/x86/entry/syscalls/syscall_64.tbl	2020-04-01 14:21:42.412151390 +0200
@@ -362,6 +362,7 @@
 439	common	watch_mount		__x64_sys_watch_mount
 440	common	watch_sb		__x64_sys_watch_sb
 441	common	fsinfo			__x64_sys_fsinfo
+442	common	readfile		__x64_sys_readfile
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
Index: linux/fs/open.c
===================================================================
--- linux.orig/fs/open.c	2020-04-01 14:21:37.284094840 +0200
+++ linux/fs/open.c	2020-04-01 14:21:42.424151523 +0200
@@ -1340,3 +1340,25 @@ int stream_open(struct inode *inode, str
 }
 
 EXPORT_SYMBOL(stream_open);
+
+SYSCALL_DEFINE5(readfile, int, dfd, const char __user *, filename,
+		char __user *, buffer, size_t, bufsize, int, flags)
+{
+	ssize_t ret;
+	struct file file = {};
+
+	if (flags)
+		return -EINVAL;
+
+	ret = user_path_at(dfd, filename, 0, &file.f_path);
+	if (!ret) {
+		file.f_inode = file.f_path.dentry->d_inode;
+		file.f_op = file.f_inode->i_fop;
+		ret = -EOPNOTSUPP;
+		if (file.f_op->readfile)
+			ret = file.f_op->readfile(&file, buffer, bufsize);
+		path_put(&file.f_path);
+	}
+
+	return ret;
+}
Index: linux/include/linux/syscalls.h
===================================================================
--- linux.orig/include/linux/syscalls.h	2020-04-01 14:21:37.284094840 +0200
+++ linux/include/linux/syscalls.h	2020-04-01 14:21:42.413151401 +0200
@@ -1011,6 +1011,8 @@ asmlinkage long sys_watch_sb(int dfd, co
 asmlinkage long sys_fsinfo(int dfd, const char __user *pathname,
 			   struct fsinfo_params __user *params, size_t params_size,
 			   void __user *result_buffer, size_t result_buf_size);
+asmlinkage long sys_readfile(int dfd, const char __user *filename,
+			     char __user *buffer, size_t bufsize, int flags);
 
 /*
  * Architecture-specific system calls
Index: linux/include/uapi/asm-generic/unistd.h
===================================================================
--- linux.orig/include/uapi/asm-generic/unistd.h	2020-04-01 14:21:37.284094840 +0200
+++ linux/include/uapi/asm-generic/unistd.h	2020-04-01 14:21:42.413151401 +0200
@@ -861,9 +861,11 @@ __SYSCALL(__NR_watch_mount, sys_watch_mo
 __SYSCALL(__NR_watch_sb, sys_watch_sb)
 #define __NR_fsinfo 441
 __SYSCALL(__NR_fsinfo, sys_fsinfo)
+#define __NR_readfile 442
+__SYSCALL(__NR_readfile, sys_readfile)
 
 #undef __NR_syscalls
-#define __NR_syscalls 442
+#define __NR_syscalls 443
 
 /*
  * 32 bit systems traditionally used different
Index: linux/include/linux/fs.h
===================================================================
--- linux.orig/include/linux/fs.h	2020-04-01 14:21:19.144894804 +0200
+++ linux/include/linux/fs.h	2020-04-01 14:21:42.425151534 +0200
@@ -1868,6 +1868,7 @@ struct file_operations {
 				   struct file *file_out, loff_t pos_out,
 				   loff_t len, unsigned int remap_flags);
 	int (*fadvise)(struct file *, loff_t, loff_t, int);
+	ssize_t (*readfile)(struct file *, char __user *, size_t);
 } __randomize_layout;
 
 struct inode_operations {

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
  2020-04-01  8:37       ` Miklos Szeredi
  2020-04-01 12:35         ` Miklos Szeredi
@ 2020-04-01 15:51         ` David Howells
  2020-04-02  1:38         ` Ian Kent
  2 siblings, 0 replies; 25+ messages in thread
From: David Howells @ 2020-04-01 15:51 UTC (permalink / raw)
  To: Miklos Szeredi
  Cc: dhowells, Ian Kent, Linus Torvalds, Al Viro, Linux NFS list,
	Andreas Dilger, Anna Schumaker, Theodore Ts'o, Linux API,
	linux-ext4, Trond Myklebust, Miklos Szeredi, Christian Brauner,
	Jann Horn, Darrick J. Wong, Karel Zak, Jeff Layton,
	linux-fsdevel, LSM, linux-kernel

Miklos Szeredi <miklos@szeredi.hu> wrote:

> For   30000 mounts, f=    146400us f2=    136766us p=   1406569us p2=
>   221669us; p=9.6*f p=10.3*f2 p=6.3*p2

	f =    146400us
	f2=    136766us
	p =   1406569us  <--- Order of magnitude slower
	p2=    221669us

And more memory used because it's added a whole bunch of inodes and dentries
to the cache.  For each mount that's a pair for each dir and a pair for each
file within the dir.  So for the two files my test is reading, for 30000
mounts, that's 90000 dentries and 90000 inodes in mountfs alone.

	(gdb) p sizeof(struct dentry)
	$1 = 216
	(gdb) p sizeof(struct inode)
	$2 = 696
	(gdb) p (216*696)*30000*3/1024/1024
	$3 = 615

so 615 MiB of RAM added to the caches in an extreme case.

We're seeing customers with 10000+ mounts - that would be 205 MiB, just to
read two values from each mount.

I presume you're not going through /proc/fdinfo each time as that would add
another d+i - for >1GiB added to the caches for 30000 mounts.

David


^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
  2020-04-01  8:37       ` Miklos Szeredi
  2020-04-01 12:35         ` Miklos Szeredi
  2020-04-01 15:51         ` David Howells
@ 2020-04-02  1:38         ` Ian Kent
  2020-04-02 14:14           ` Karel Zak
  2 siblings, 1 reply; 25+ messages in thread
From: Ian Kent @ 2020-04-02  1:38 UTC (permalink / raw)
  To: Miklos Szeredi, David Howells
  Cc: Linus Torvalds, Al Viro, Linux NFS list, Andreas Dilger,
	Anna Schumaker, Theodore Ts'o, Linux API, linux-ext4,
	Trond Myklebust, Miklos Szeredi, Christian Brauner, Jann Horn,
	Darrick J. Wong, Karel Zak, Jeff Layton, linux-fsdevel, LSM,
	linux-kernel

On Wed, 2020-04-01 at 10:37 +0200, Miklos Szeredi wrote:
> On Wed, Apr 1, 2020 at 10:27 AM David Howells <dhowells@redhat.com>
> wrote:
> > Miklos Szeredi <miklos@szeredi.hu> wrote:
> > 
> > > According to dhowell's measurements processing 100k mounts would
> > > take
> > > about a few seconds of system time (that's the time spent by the
> > > kernel to retrieve the data,
> > 
> > But the inefficiency of mountfs - at least as currently implemented
> > - scales
> > up with the number of individual values you want to retrieve, both
> > in terms of
> > memory usage and time taken.
> 
> I've taken that into account when guesstimating a "few seconds per
> 100k entries".  My guess is that there's probably an order of
> magnitude difference between the performance of a fs based interface
> and a binary syscall based interface.  That could be reduced somewhat
> with a readfile(2) type API.
> 
> But the point is: this does not matter.  Whether it's .5s or 5s is
> completely irrelevant, as neither is going to take down the system,
> and userspace processing is probably going to take as much, if not
> more time.  And remember, we are talking about stopping and starting
> the automount daemon, which is something that happens, but it should
> not happen often by any measure.

Yes, but don't forget, I'm reporting what I saw when testing during
development.

From previous discussion we know systemd (and probably the other apps
like udisks2, et. al.) gets notified on mount and umount activity so
its not going to be just starting and stopping autofs that's a problem
with very large mount tables.

To get a feel for the real difference we'd need to make the libmount
changes for both and then check between the two and check behaviour.
The mount and umount lookup case that Karel (and I) talked about
should be sufficient.

The biggest problem I had with fsinfo() when I was working with
earlier series was getting fs specific options, in particular the
need to use sb op ->fsinfo(). With this latest series David has made
that part of the generic code and your patch also cover it.

So the thing that was holding me up is done so we should be getting
on with libmount improvements, we need to settle this.

I prefer the system call interface and I'm not offering justification
for that other than a general dislike (and on occasion outright
frustration) of pretty much every proc implementation I have had to
look at.

> 
> > With fsinfo(), I've tried to batch values together where it makes
> > sense - and
> > there's no lingering memory overhead - no extra inodes, dentries
> > and files
> > required.
> 
> The dentries, inodes and files in your test are single use (except
> the
> root dentry) and can be made ephemeral if that turns out to be
> better.
> My guess is that dentries belonging to individual attributes should
> be
> deleted on final put, while the dentries belonging to the mount
> directory can be reclaimed normally.
> 
> Thanks,
> Miklos


^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
  2020-04-02  1:38         ` Ian Kent
@ 2020-04-02 14:14           ` Karel Zak
  0 siblings, 0 replies; 25+ messages in thread
From: Karel Zak @ 2020-04-02 14:14 UTC (permalink / raw)
  To: Ian Kent
  Cc: Miklos Szeredi, David Howells, Linus Torvalds, Al Viro,
	Linux NFS list, Andreas Dilger, Anna Schumaker,
	Theodore Ts'o, Linux API, linux-ext4, Trond Myklebust,
	Miklos Szeredi, Christian Brauner, Jann Horn, Darrick J. Wong,
	Jeff Layton, linux-fsdevel, LSM, linux-kernel

On Thu, Apr 02, 2020 at 09:38:20AM +0800, Ian Kent wrote:
> I prefer the system call interface and I'm not offering justification
> for that other than a general dislike (and on occasion outright
> frustration) of pretty much every proc implementation I have had to
> look at.

Frankly, I'm modest, what about to have both interfaces in kernel --
fsinfo() as well mountfs? It's nothing unusual for example for block
devices to have attribute accessible by /sys as well as by ioctl().

I can imagine that for complex task or performance sensitive tasks
it's better to use fsinfo(), but in another simple use-cases (for
example to convert mountpoint to device name in shell) is better to
read /proc/.../<atrtr>.

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com


^ permalink raw reply	[flat|nested] 25+ messages in thread

end of thread, other threads:[~2020-04-02 14:14 UTC | newest]

Thread overview: 25+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
2020-03-18 15:08 ` [PATCH 01/13] fsinfo: Add fsinfo() syscall to query filesystem " David Howells
2020-03-18 15:08 ` [PATCH 02/13] fsinfo: Provide a bitmap of supported features " David Howells
2020-03-18 15:08 ` [PATCH 03/13] fsinfo: Allow retrieval of superblock devname, options and stats " David Howells
2020-03-18 15:08 ` [PATCH 04/13] fsinfo: Allow fsinfo() to look up a mount object by ID " David Howells
2020-03-18 15:08 ` [PATCH 05/13] fsinfo: Add a uniquifier ID to struct mount " David Howells
2020-03-18 15:09 ` [PATCH 06/13] fsinfo: Allow mount information to be queried " David Howells
2020-03-18 15:09 ` [PATCH 07/13] fsinfo: Allow mount topology and propagation info to be retrieved " David Howells
2020-03-18 15:09 ` [PATCH 08/13] fsinfo: Provide notification overrun handling support " David Howells
2020-03-18 15:09 ` [PATCH 09/13] fsinfo: sample: Mount listing program " David Howells
2020-03-18 15:09 ` [PATCH 10/13] fsinfo: Add API documentation " David Howells
2020-03-18 15:09 ` [PATCH 11/13] fsinfo: Add support for AFS " David Howells
2020-03-18 15:09 ` [PATCH 12/13] fsinfo: Example support for Ext4 " David Howells
2020-03-18 15:10 ` [PATCH 13/13] fsinfo: Example support for NFS " David Howells
2020-03-18 16:05 ` [PATCH 00/13] VFS: Filesystem information " Miklos Szeredi
2020-04-01  5:22   ` Ian Kent
2020-04-01  8:18     ` Miklos Szeredi
2020-04-01  8:27     ` David Howells
2020-04-01  8:37       ` Miklos Szeredi
2020-04-01 12:35         ` Miklos Szeredi
2020-04-01 15:51         ` David Howells
2020-04-02  1:38         ` Ian Kent
2020-04-02 14:14           ` Karel Zak
2020-03-19 10:37 ` David Howells
2020-03-19 12:36   ` Miklos Szeredi

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