* [PATCH 0/6] overlay filesystem
@ 2011-04-18 16:00 Miklos Szeredi
2011-04-18 16:00 ` [PATCH 1/6] vfs: add i_op->open() Miklos Szeredi
` (7 more replies)
0 siblings, 8 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-04-18 16:00 UTC (permalink / raw)
To: viro; +Cc: linux-fsdevel, linux-kernel, apw, nbd, neilb, hramrach
Here's an updated version of the overlay filesystem.
Git tree is here:
git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs.v8
Changes from v7 to v8:
- split overlayfs.c into smaller files
- fix locking for copy up (reported by Al Viro)
- locking analysis of copy up vs. directory rename added as a comment
- tested with lockdep, fixed one lock annotation
- other bug fixes
To be done:
- redo i_op->open, waiting for status of atomic_open() from Al
- look into xattr support for tmpfs
Thanks,
Miklos
---
Andy Whitcroft (1):
overlayfs: add statfs support
Miklos Szeredi (4):
vfs: add i_op->open()
vfs: export do_splice_direct() to modules
vfs: introduce clone_private_mount()
overlay filesystem
Neil Brown (1):
overlay: overlay filesystem documentation
---
Documentation/filesystems/overlayfs.txt | 167 +++++++++
MAINTAINERS | 7 +
fs/Kconfig | 1 +
fs/Makefile | 1 +
fs/namespace.c | 17 +
fs/open.c | 76 +++--
fs/overlayfs/Kconfig | 4 +
fs/overlayfs/Makefile | 5 +
fs/overlayfs/copy_up.c | 382 ++++++++++++++++++++
fs/overlayfs/dir.c | 592 ++++++++++++++++++++++++++++++
fs/overlayfs/inode.c | 374 +++++++++++++++++++
fs/overlayfs/overlayfs.c | 596 +++++++++++++++++++++++++++++++
fs/overlayfs/overlayfs.h | 63 ++++
fs/overlayfs/readdir.c | 560 +++++++++++++++++++++++++++++
fs/splice.c | 1 +
include/linux/fs.h | 2 +
include/linux/mount.h | 3 +
17 files changed, 2825 insertions(+), 26 deletions(-)
create mode 100644 Documentation/filesystems/overlayfs.txt
create mode 100644 fs/overlayfs/Kconfig
create mode 100644 fs/overlayfs/Makefile
create mode 100644 fs/overlayfs/copy_up.c
create mode 100644 fs/overlayfs/dir.c
create mode 100644 fs/overlayfs/inode.c
create mode 100644 fs/overlayfs/overlayfs.c
create mode 100644 fs/overlayfs/overlayfs.h
create mode 100644 fs/overlayfs/readdir.c
------------------------------------------------------------------------------
Changes from v6 to v7
- added patches from Felix Fietkau to fix deadlocks on jffs2
- optimized directory removal
- properly clean up after copy-up and other failures
------------------------------------------------------------------------------
Changes from v5 to v6
- optimize directory merging
o use rbtree for weeding out duplicates
o use a cursor for current position within the stream
- instead of f_op->open_other(), implement i_op->open()
- don't share inodes for non-directory dentries - for now. I hope
this can come back once RCU lookup code has settled.
- misc bug fixes
------------------------------------------------------------------------------
Changes from v4 to v5
- fix copying up if fs doesn't support xattrs (Andy Whitcroft)
- clone mounts to be used internally to access the underlying
filesystems
------------------------------------------------------------------------------
Changes from v3 to v4
- export security_inode_permission to allow overlayfs to be modular
(Andy Whitcroft)
- add statfs support (Andy Whitcroft)
- change BUG_ON to WARN_ON
- Revert "vfs: add flag to allow rename to same inode", instead
introduce s_op->is_same_inode()
- overlayfs: fix rename to self
- fix whiteout after rename
------------------------------------------------------------------------------
Changes from v2 to v3
- Minimal remount support. As overlayfs reflects the 'readonly'
mount status in write-access to the upper filesystem, we must
handle remount and either drop or take write access when the ro
status changes. (NeilBrown)
- Use correct seek function for directories. It is incorrect to call
generic_llseek_file on a file from a different filesystem. For
that we must use the seek function that the filesystem defines,
which is called by vfs_llseek. Also, we only want to seek the
realfile when is_real is true. Otherwise we just want to update
our own f_pos pointer, so use generic_llseek_file for
that. (NeilBrown)
- Initialise is_real before use. The previous patch can use
od->is_real before it is properly initialised is llseek is called
before readdir. So factor out the initialisation of is_real and
call it from both readdir and llseek when f_pos is 0. (NeilBrown)
- Rename ovl_fill_cache to ovl_dir_read (NeilBrown)
- Tiny optimisation in open_other handling (NeilBrown)
- Assorted updates to Documentation/filesystems/overlayfs.txt (NeilBrown)
- Make copy-up work for >=4G files, make it killable during copy-up.
Need to fix recovery after a failed/interrupted copy-up.
- Store and reference upper/lower dentries in overlay dentries.
Store and reference upper/lower vfsmounts in overlay superblock.
- Add necessary barriers for setting upper dentry in copyup and for
retrieving upper dentry locklessly.
- Make sure the right file is used for directory fsync() after
copy-up.
- Add locking to ovl_dir_llseek() to prevent concurrent call of
ovl_dir_reset() with ovl_dir_read().
- Get rid of ovl_dentry_iput(). The VFS doesn't provide enough
locking for this function that the contents of ->d_fsdata could be
safely updated.
- After copying up a non-directory unhash the dentry. This way the
lower dentry ref, which is no longer necessary, can go away. This
revealed a use-after-free bug in truncate handling in
fs/namei.c:finish_open().
- Fix if a copy-up happens between the follow_linka the put_link
calls.
- Replace some WARN_ONs with BUG_ON. Some things just _really_
shouldn't happen.
- Extract common code from ovl_unlink and ovl_rmdir to a helper
function.
- After unlink and rmdir unhash the dentry. This will get rid of the
lower and upper dentry references after there are no more users of
the deleted dentry. This is a safe replacement for the removed
->d_iput() functionality.
- Added checks to unlink, rmdir and rename to verify that the
parent-child relationship in the upper filesystem matches that of
the overlay. This is necessary to prevent crash and/or corruption
if the upper filesystem topology is being modified while part of
the overlay.
- Optimize checking whiteout and opaque attributes.
- Optimize copy-up on truncate: don't copy up whole file before
truncating
- Misc bug fixes
------------------------------------------------------------------------------
Changes from v1 to v2
- rename "hybrid union filesystem" to "overlay filesystem" or overlayfs
- added documentation written by Neil
- correct st_dev for directories (reported by Neil)
- use getattr() to get attributes from the underlying filesystems,
this means that now an overlay filesystem itself can be the lower,
read-only layer of another overlay
- listxattr filters out private extended attributes
- get write ref on the upper layer on mount unless the overlay
itself is mounted read-only
- raise capabilities for copy up, dealing with whiteouts and opaque
directories. Now the overlay works for non-root users as well
- "rm -rf" didn't work correctly in all cases if the directory was
copied up between opendir and the first readdir, this is now fixed
(and the directory operations consolidated)
- simplified copy up, this broke optimization for truncate and
open(O_TRUNC) (now file is copied up to be immediately truncated,
will fix)
- st_nlink for merged directories set to 1, this is an "illegal"
value that normal filesystems never have but some use it to
indicate that the number of subdirectories is unknown. Utilities
(find, ...) seem to tolerate this well.
- misc fixes I forgot about
^ permalink raw reply [flat|nested] 19+ messages in thread
* [PATCH 1/6] vfs: add i_op->open()
2011-04-18 16:00 [PATCH 0/6] overlay filesystem Miklos Szeredi
@ 2011-04-18 16:00 ` Miklos Szeredi
2011-04-18 16:00 ` [PATCH 2/6] vfs: export do_splice_direct() to modules Miklos Szeredi
` (6 subsequent siblings)
7 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-04-18 16:00 UTC (permalink / raw)
To: viro
Cc: linux-fsdevel, linux-kernel, apw, nbd, neilb, hramrach, Miklos Szeredi
From: Miklos Szeredi <mszeredi@suse.cz>
Add a new inode operation i_op->open(). This is for stacked
filesystems that want to return a struct file from a different
filesystem.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/open.c | 76 ++++++++++++++++++++++++++++++++++------------------
include/linux/fs.h | 2 +
2 files changed, 52 insertions(+), 26 deletions(-)
diff --git a/fs/open.c b/fs/open.c
index b52cf01..84fa16a 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -666,8 +666,7 @@ static inline int __get_file_write_access(struct inode *inode,
return error;
}
-static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
- struct file *f,
+static struct file *__dentry_open(struct path *path, struct file *f,
int (*open)(struct inode *, struct file *),
const struct cred *cred)
{
@@ -675,15 +674,16 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
struct inode *inode;
int error;
+ path_get(path);
f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
FMODE_PREAD | FMODE_PWRITE;
if (unlikely(f->f_flags & O_PATH))
f->f_mode = FMODE_PATH;
- inode = dentry->d_inode;
+ inode = path->dentry->d_inode;
if (f->f_mode & FMODE_WRITE) {
- error = __get_file_write_access(inode, mnt);
+ error = __get_file_write_access(inode, path->mnt);
if (error)
goto cleanup_file;
if (!special_file(inode->i_mode))
@@ -691,8 +691,7 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
}
f->f_mapping = inode->i_mapping;
- f->f_path.dentry = dentry;
- f->f_path.mnt = mnt;
+ f->f_path = *path;
f->f_pos = 0;
file_sb_list_add(f, inode->i_sb);
@@ -745,7 +744,7 @@ cleanup_all:
* here, so just reset the state.
*/
file_reset_write(f);
- mnt_drop_write(mnt);
+ mnt_drop_write(path->mnt);
}
}
file_sb_list_del(f);
@@ -753,8 +752,7 @@ cleanup_all:
f->f_path.mnt = NULL;
cleanup_file:
put_filp(f);
- dput(dentry);
- mntput(mnt);
+ path_put(path);
return ERR_PTR(error);
}
@@ -780,14 +778,14 @@ cleanup_file:
struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
int (*open)(struct inode *, struct file *))
{
+ struct path path = { .dentry = dentry, .mnt = nd->path.mnt };
const struct cred *cred = current_cred();
if (IS_ERR(nd->intent.open.file))
goto out;
if (IS_ERR(dentry))
goto out_err;
- nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
- nd->intent.open.file,
+ nd->intent.open.file = __dentry_open(&path, nd->intent.open.file,
open, cred);
out:
return nd->intent.open.file;
@@ -816,10 +814,17 @@ struct file *nameidata_to_filp(struct nameidata *nd)
/* Has the filesystem initialised the file for us? */
if (filp->f_path.dentry == NULL) {
- path_get(&nd->path);
- filp = __dentry_open(nd->path.dentry, nd->path.mnt, filp,
- NULL, cred);
+ struct inode *inode = nd->path.dentry->d_inode;
+
+ if (inode->i_op->open) {
+ int flags = filp->f_flags;
+ put_filp(filp);
+ filp = inode->i_op->open(nd->path.dentry, flags, cred);
+ } else {
+ filp = __dentry_open(&nd->path, filp, NULL, cred);
+ }
}
+
return filp;
}
@@ -830,26 +835,45 @@ struct file *nameidata_to_filp(struct nameidata *nd)
struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
const struct cred *cred)
{
- int error;
- struct file *f;
-
- validate_creds(cred);
+ struct path path = { .dentry = dentry, .mnt = mnt };
+ struct file *ret;
/* We must always pass in a valid mount pointer. */
BUG_ON(!mnt);
- error = -ENFILE;
+ ret = vfs_open(&path, flags, cred);
+ path_put(&path);
+
+ return ret;
+}
+EXPORT_SYMBOL(dentry_open);
+
+/**
+ * vfs_open - open the file at the given path
+ * @path: path to open
+ * @flags: open flags
+ * @cred: credentials to use
+ *
+ * Open the file. If successful, the returned file will have acquired
+ * an additional reference for path.
+ */
+struct file *vfs_open(struct path *path, int flags, const struct cred *cred)
+{
+ struct file *f;
+ struct inode *inode = path->dentry->d_inode;
+
+ validate_creds(cred);
+
+ if (inode->i_op->open)
+ return inode->i_op->open(path->dentry, flags, cred);
f = get_empty_filp();
- if (f == NULL) {
- dput(dentry);
- mntput(mnt);
- return ERR_PTR(error);
- }
+ if (f == NULL)
+ return ERR_PTR(-ENFILE);
f->f_flags = flags;
- return __dentry_open(dentry, mnt, f, NULL, cred);
+ return __dentry_open(path, f, NULL, cred);
}
-EXPORT_SYMBOL(dentry_open);
+EXPORT_SYMBOL(vfs_open);
static void __put_unused_fd(struct files_struct *files, unsigned int fd)
{
diff --git a/include/linux/fs.h b/include/linux/fs.h
index dbd860a..fa062a8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1595,6 +1595,7 @@ struct inode_operations {
void (*truncate_range)(struct inode *, loff_t, loff_t);
int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
u64 len);
+ struct file *(*open)(struct dentry *, int flags, const struct cred *);
} ____cacheline_aligned;
struct seq_file;
@@ -1989,6 +1990,7 @@ extern long do_sys_open(int dfd, const char __user *filename, int flags,
extern struct file *filp_open(const char *, int, int);
extern struct file *file_open_root(struct dentry *, struct vfsmount *,
const char *, int);
+extern struct file *vfs_open(struct path *, int flags, const struct cred *);
extern struct file * dentry_open(struct dentry *, struct vfsmount *, int,
const struct cred *);
extern int filp_close(struct file *, fl_owner_t id);
--
1.7.1
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 2/6] vfs: export do_splice_direct() to modules
2011-04-18 16:00 [PATCH 0/6] overlay filesystem Miklos Szeredi
2011-04-18 16:00 ` [PATCH 1/6] vfs: add i_op->open() Miklos Szeredi
@ 2011-04-18 16:00 ` Miklos Szeredi
2011-04-18 16:00 ` [PATCH 3/6] vfs: introduce clone_private_mount() Miklos Szeredi
` (5 subsequent siblings)
7 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-04-18 16:00 UTC (permalink / raw)
To: viro
Cc: linux-fsdevel, linux-kernel, apw, nbd, neilb, hramrach, Miklos Szeredi
From: Miklos Szeredi <mszeredi@suse.cz>
Export do_splice_direct() to modules. Needed by overlay filesystem.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/splice.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/fs/splice.c b/fs/splice.c
index 50a5d97..4f2fa05 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1296,6 +1296,7 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
return ret;
}
+EXPORT_SYMBOL(do_splice_direct);
static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
struct pipe_inode_info *opipe,
--
1.7.1
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 3/6] vfs: introduce clone_private_mount()
2011-04-18 16:00 [PATCH 0/6] overlay filesystem Miklos Szeredi
2011-04-18 16:00 ` [PATCH 1/6] vfs: add i_op->open() Miklos Szeredi
2011-04-18 16:00 ` [PATCH 2/6] vfs: export do_splice_direct() to modules Miklos Szeredi
@ 2011-04-18 16:00 ` Miklos Szeredi
2011-04-18 16:00 ` [PATCH 4/6] overlay filesystem Miklos Szeredi
` (4 subsequent siblings)
7 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-04-18 16:00 UTC (permalink / raw)
To: viro
Cc: linux-fsdevel, linux-kernel, apw, nbd, neilb, hramrach, Miklos Szeredi
From: Miklos Szeredi <mszeredi@suse.cz>
Overlayfs needs a private clone of the mount, so create a function for
this and export to modules.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/namespace.c | 17 +++++++++++++++++
include/linux/mount.h | 3 +++
2 files changed, 20 insertions(+), 0 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index d99bcf5..4bcc60e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1494,6 +1494,23 @@ void drop_collected_mounts(struct vfsmount *mnt)
release_mounts(&umount_list);
}
+struct vfsmount *clone_private_mount(struct path *path)
+{
+ struct vfsmount *mnt;
+
+ if (IS_MNT_UNBINDABLE(path->mnt))
+ return ERR_PTR(-EINVAL);
+
+ down_read(&namespace_sem);
+ mnt = clone_mnt(path->mnt, path->dentry, CL_PRIVATE);
+ up_read(&namespace_sem);
+ if (!mnt)
+ return ERR_PTR(-ENOMEM);
+
+ return mnt;
+}
+EXPORT_SYMBOL_GPL(clone_private_mount);
+
int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
struct vfsmount *root)
{
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 604f122..44e9bf4 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -100,6 +100,9 @@ extern void mnt_pin(struct vfsmount *mnt);
extern void mnt_unpin(struct vfsmount *mnt);
extern int __mnt_is_readonly(struct vfsmount *mnt);
+struct path;
+extern struct vfsmount *clone_private_mount(struct path *path);
+
extern struct vfsmount *do_kern_mount(const char *fstype, int flags,
const char *name, void *data);
--
1.7.1
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 4/6] overlay filesystem
2011-04-18 16:00 [PATCH 0/6] overlay filesystem Miklos Szeredi
` (2 preceding siblings ...)
2011-04-18 16:00 ` [PATCH 3/6] vfs: introduce clone_private_mount() Miklos Szeredi
@ 2011-04-18 16:00 ` Miklos Szeredi
2011-04-18 16:00 ` [PATCH 5/6] overlayfs: add statfs support Miklos Szeredi
` (3 subsequent siblings)
7 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-04-18 16:00 UTC (permalink / raw)
To: viro
Cc: linux-fsdevel, linux-kernel, apw, nbd, neilb, hramrach, Miklos Szeredi
From: Miklos Szeredi <mszeredi@suse.cz>
Overlayfs allows one, usually read-write, directory tree to be
overlaid onto another, read-only directory tree. All modifications
go to the upper, writable layer.
This type of mechanism is most often used for live CDs but there's a
wide variety of other uses.
The implementation differs from other "union filesystem"
implementations in that after a file is opened all operations go
directly to the underlying, lower or upper, filesystems. This
simplifies the implementation and allows native performance in these
cases.
The dentry tree is duplicated from the underlying filesystems, this
enables fast cached lookups without adding special support into the
VFS. This uses slightly more memory than union mounts, but dentries
are relatively small.
Currently inodes are duplicated as well, but it is a possible
optimization to share inodes for non-directories.
Opening non directories results in the open forwarded to the
underlying filesystem. This makes the behavior very similar to union
mounts (with the same limitations vs. fchmod/fchown on O_RDONLY file
descriptors).
Usage:
mount -t overlay -olowerdir=/lower,upperdir=/upper overlay /mnt
Supported:
- all operations
Missing:
- ensure that filesystems part of the overlay are not modified outside
the overlay
Neil Brown <neilb@suse.de>:
- minimal remount support
- use correct seek function for directories
- initialise is_real before use
- rename ovl_fill_cache to ovl_dir_read
Felix Fietkau <nbd@openwrt.org>:
- fix a deadlock in ovl_dir_read_merged
- fix a deadlock in ovl_remove_whiteouts
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/Kconfig | 1 +
fs/Makefile | 1 +
fs/overlayfs/Kconfig | 4 +
fs/overlayfs/Makefile | 5 +
fs/overlayfs/copy_up.c | 382 ++++++++++++++++++++++++++++++
fs/overlayfs/dir.c | 592 ++++++++++++++++++++++++++++++++++++++++++++++
fs/overlayfs/inode.c | 374 +++++++++++++++++++++++++++++
fs/overlayfs/overlayfs.c | 576 ++++++++++++++++++++++++++++++++++++++++++++
fs/overlayfs/overlayfs.h | 63 +++++
fs/overlayfs/readdir.c | 560 +++++++++++++++++++++++++++++++++++++++++++
10 files changed, 2558 insertions(+), 0 deletions(-)
create mode 100644 fs/overlayfs/Kconfig
create mode 100644 fs/overlayfs/Makefile
create mode 100644 fs/overlayfs/copy_up.c
create mode 100644 fs/overlayfs/dir.c
create mode 100644 fs/overlayfs/inode.c
create mode 100644 fs/overlayfs/overlayfs.c
create mode 100644 fs/overlayfs/overlayfs.h
create mode 100644 fs/overlayfs/readdir.c
diff --git a/fs/Kconfig b/fs/Kconfig
index f3aa9b0..7a6ec52 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -63,6 +63,7 @@ source "fs/quota/Kconfig"
source "fs/autofs4/Kconfig"
source "fs/fuse/Kconfig"
+source "fs/overlayfs/Kconfig"
config CUSE
tristate "Character device in Userspace support"
diff --git a/fs/Makefile b/fs/Makefile
index fb68c2b..ac7402a 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -105,6 +105,7 @@ obj-$(CONFIG_QNX4FS_FS) += qnx4/
obj-$(CONFIG_AUTOFS4_FS) += autofs4/
obj-$(CONFIG_ADFS_FS) += adfs/
obj-$(CONFIG_FUSE_FS) += fuse/
+obj-$(CONFIG_OVERLAYFS_FS) += overlayfs/
obj-$(CONFIG_UDF_FS) += udf/
obj-$(CONFIG_SUN_OPENPROMFS) += openpromfs/
obj-$(CONFIG_OMFS_FS) += omfs/
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
new file mode 100644
index 0000000..c4517da
--- /dev/null
+++ b/fs/overlayfs/Kconfig
@@ -0,0 +1,4 @@
+config OVERLAYFS_FS
+ tristate "Overlay filesystem support"
+ help
+ Add support for overlay filesystem.
diff --git a/fs/overlayfs/Makefile b/fs/overlayfs/Makefile
new file mode 100644
index 0000000..a7ebbf0
--- /dev/null
+++ b/fs/overlayfs/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile for the overlay filesystem.
+#
+
+obj-$(CONFIG_OVERLAYFS_FS) += overlayfs.o inode.o dir.o readdir.o copy_up.o
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
new file mode 100644
index 0000000..fb9962c
--- /dev/null
+++ b/fs/overlayfs/copy_up.c
@@ -0,0 +1,382 @@
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/splice.h>
+#include <linux/xattr.h>
+#include <linux/security.h>
+#include "overlayfs.h"
+
+#define OVL_COPY_UP_CHUNK_SIZE (1 << 20)
+
+static int ovl_copy_up_xattr(struct dentry *old, struct dentry *new)
+{
+ ssize_t list_size, size;
+ char *buf, *name, *value;
+ int error;
+
+ if (!old->d_inode->i_op->getxattr ||
+ !new->d_inode->i_op->getxattr)
+ return 0;
+
+ list_size = vfs_listxattr(old, NULL, 0);
+ if (list_size <= 0) {
+ if (list_size == -EOPNOTSUPP)
+ return 0;
+ return list_size;
+ }
+
+ buf = kzalloc(list_size, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ error = -ENOMEM;
+ value = kmalloc(XATTR_SIZE_MAX, GFP_KERNEL);
+ if (!value)
+ goto out;
+
+ list_size = vfs_listxattr(old, buf, list_size);
+ if (list_size <= 0) {
+ error = list_size;
+ goto out_free_value;
+ }
+
+ for (name = buf; name < (buf + list_size); name += strlen(name) + 1) {
+ size = vfs_getxattr(old, name, value, XATTR_SIZE_MAX);
+ if (size <= 0) {
+ error = size;
+ goto out_free_value;
+ }
+ error = vfs_setxattr(new, name, value, size, 0);
+ if (error)
+ goto out_free_value;
+ }
+
+out_free_value:
+ kfree(value);
+out:
+ kfree(buf);
+ return error;
+}
+
+static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
+{
+ struct file *old_file;
+ struct file *new_file;
+ int error = 0;
+
+ if (len == 0)
+ return 0;
+
+ old_file = vfs_open(old, O_RDONLY, current_cred());
+ if (IS_ERR(old_file))
+ return PTR_ERR(old_file);
+
+ new_file = vfs_open(new, O_WRONLY, current_cred());
+ if (IS_ERR(new_file)) {
+ error = PTR_ERR(new_file);
+ goto out_fput;
+ }
+
+ /* FIXME: copy up sparse files efficiently */
+ while (len) {
+ loff_t offset = new_file->f_pos;
+ size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
+ long bytes;
+
+ if (len < this_len)
+ this_len = len;
+
+ if (signal_pending_state(TASK_KILLABLE, current)) {
+ error = -EINTR;
+ break;
+ }
+
+ bytes = do_splice_direct(old_file, &offset, new_file, this_len,
+ SPLICE_F_MOVE);
+ if (bytes <= 0) {
+ error = bytes;
+ break;
+ }
+
+ len -= bytes;
+ }
+
+ fput(new_file);
+out_fput:
+ fput(old_file);
+ return error;
+}
+
+static char *ovl_read_symlink(struct dentry *realdentry)
+{
+ int res;
+ char *buf;
+ struct inode *inode = realdentry->d_inode;
+ mm_segment_t old_fs;
+
+ res = -EINVAL;
+ if (!inode->i_op->readlink)
+ goto err;
+
+ res = -ENOMEM;
+ buf = (char *) __get_free_page(GFP_KERNEL);
+ if (!buf)
+ goto err;
+
+ old_fs = get_fs();
+ set_fs(get_ds());
+ /* The cast to a user pointer is valid due to the set_fs() */
+ res = inode->i_op->readlink(realdentry,
+ (char __user *)buf, PAGE_SIZE - 1);
+ set_fs(old_fs);
+ if (res < 0) {
+ free_page((unsigned long) buf);
+ goto err;
+ }
+ buf[res] = '\0';
+
+ return buf;
+
+err:
+ return ERR_PTR(res);
+}
+
+static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat)
+{
+ struct iattr attr = {
+ .ia_valid = ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET,
+ .ia_atime = stat->atime,
+ .ia_mtime = stat->mtime,
+ };
+
+ return notify_change(upperdentry, &attr);
+}
+
+static int ovl_set_mode(struct dentry *upperdentry, umode_t mode)
+{
+ struct iattr attr = {
+ .ia_valid = ATTR_MODE,
+ .ia_mode = mode,
+ };
+
+ return notify_change(upperdentry, &attr);
+}
+
+static int ovl_copy_up_locked(struct dentry *upperdir, struct dentry *dentry,
+ struct path *lowerpath, struct kstat *stat,
+ const char *link)
+{
+ int err;
+ struct path newpath;
+ umode_t mode = stat->mode;
+
+ /* Can't properly set mode on creation because of the umask */
+ stat->mode &= S_IFMT;
+
+ ovl_path_upper(dentry, &newpath);
+ WARN_ON(newpath.dentry);
+ newpath.dentry = ovl_upper_create(upperdir, dentry, stat, link);
+ if (IS_ERR(newpath.dentry))
+ return PTR_ERR(newpath.dentry);
+
+ if (S_ISREG(stat->mode)) {
+ err = ovl_copy_up_data(lowerpath, &newpath, stat->size);
+ if (err)
+ goto err_remove;
+ }
+
+ err = ovl_copy_up_xattr(lowerpath->dentry, newpath.dentry);
+ if (err)
+ goto err_remove;
+
+ mutex_lock(&newpath.dentry->d_inode->i_mutex);
+ if (!S_ISLNK(stat->mode))
+ err = ovl_set_mode(newpath.dentry, mode);
+ if (!err)
+ err = ovl_set_timestamps(newpath.dentry, stat);
+ mutex_unlock(&newpath.dentry->d_inode->i_mutex);
+ if (err)
+ goto err_remove;
+
+ ovl_dentry_update(dentry, newpath.dentry);
+
+ /*
+ * Easiest way to get rid of the lower dentry reference is to
+ * drop this dentry. This is neither needed nor possible for
+ * directories.
+ */
+ if (!S_ISDIR(stat->mode))
+ d_drop(dentry);
+
+ return 0;
+
+err_remove:
+ if (S_ISDIR(stat->mode))
+ vfs_rmdir(upperdir->d_inode, newpath.dentry);
+ else
+ vfs_unlink(upperdir->d_inode, newpath.dentry);
+
+ dput(newpath.dentry);
+
+ return err;
+}
+
+/*
+ * Copy up a single dentry
+ *
+ * Directory renames only allowed on "pure upper" (already created on
+ * upper filesystem, never copied up). Directories which are on lower or
+ * are merged may not be renamed. For these -EXDEV is returned and
+ * userspace has to deal with it. This means, when copying up a
+ * directory we can rely on it and ancestors being stable.
+ *
+ * Non-directory renames start with copy up of source if necessary. The
+ * actual rename will only proceed once the copy up was successful. Copy
+ * up uses upper parent i_mutex for exclusion. Since rename can change
+ * d_parent it is possible that the copy up will lock the old parent. At
+ * that point the file will have already been copied up anyway.
+ */
+static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
+ struct path *lowerpath, struct kstat *stat)
+{
+ int err;
+ struct kstat pstat;
+ struct path parentpath;
+ struct dentry *upperdir;
+ const struct cred *old_cred;
+ struct cred *override_cred;
+ char *link = NULL;
+
+ ovl_path_upper(parent, &parentpath);
+ upperdir = parentpath.dentry;
+
+ err = vfs_getattr(parentpath.mnt, parentpath.dentry, &pstat);
+ if (err)
+ return err;
+
+ if (S_ISLNK(stat->mode)) {
+ link = ovl_read_symlink(lowerpath->dentry);
+ if (IS_ERR(link))
+ return PTR_ERR(link);
+ }
+
+ err = -ENOMEM;
+ override_cred = prepare_creds();
+ if (!override_cred)
+ goto out_free_link;
+
+ override_cred->fsuid = stat->uid;
+ override_cred->fsgid = stat->gid;
+ /*
+ * CAP_SYS_ADMIN for copying up extended attributes
+ * CAP_DAC_OVERRIDE for create
+ * CAP_FOWNER for chmod, timestamp update
+ * CAP_FSETID for chmod
+ * CAP_MKNOD for mknod
+ */
+ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+ cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+ cap_raise(override_cred->cap_effective, CAP_FOWNER);
+ cap_raise(override_cred->cap_effective, CAP_FSETID);
+ cap_raise(override_cred->cap_effective, CAP_MKNOD);
+ old_cred = override_creds(override_cred);
+
+ mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
+ if (ovl_path_type(dentry) != OVL_PATH_LOWER) {
+ err = 0;
+ } else {
+ err = ovl_copy_up_locked(upperdir, dentry, lowerpath,
+ stat, link);
+ if (!err) {
+ /* Restore timestamps on parent (best effort) */
+ ovl_set_timestamps(upperdir, &pstat);
+ }
+ }
+
+ mutex_unlock(&upperdir->d_inode->i_mutex);
+
+ revert_creds(old_cred);
+ put_cred(override_cred);
+
+out_free_link:
+ if (link)
+ free_page((unsigned long) link);
+
+ return err;
+}
+
+int ovl_copy_up(struct dentry *dentry)
+{
+ int err;
+
+ err = 0;
+ while (!err) {
+ struct dentry *next;
+ struct dentry *parent;
+ struct path lowerpath;
+ struct kstat stat;
+ enum ovl_path_type type = ovl_path_type(dentry);
+
+ if (type != OVL_PATH_LOWER)
+ break;
+
+ next = dget(dentry);
+ /* find the topmost dentry not yet copied up */
+ for (;;) {
+ parent = dget_parent(next);
+
+ type = ovl_path_type(parent);
+ if (type != OVL_PATH_LOWER)
+ break;
+
+ dput(next);
+ next = parent;
+ }
+
+ ovl_path_lower(next, &lowerpath);
+ err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
+ if (!err)
+ err = ovl_copy_up_one(parent, next, &lowerpath, &stat);
+
+ dput(parent);
+ dput(next);
+ }
+
+ return err;
+}
+
+/* Optimize by not copying up the file first and truncating later */
+int ovl_copy_up_truncate(struct dentry *dentry, loff_t size)
+{
+ int err;
+ struct kstat stat;
+ struct path lowerpath;
+ struct dentry *parent = dget_parent(dentry);
+
+ err = ovl_copy_up(parent);
+ if (err)
+ goto out_dput_parent;
+
+ ovl_path_lower(dentry, &lowerpath);
+ err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
+ if (err)
+ goto out_dput_parent;
+
+ if (size < stat.size)
+ stat.size = size;
+
+ err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
+
+out_dput_parent:
+ dput(parent);
+ return err;
+}
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
new file mode 100644
index 0000000..81f5fb9
--- /dev/null
+++ b/fs/overlayfs/dir.c
@@ -0,0 +1,592 @@
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/xattr.h>
+#include <linux/security.h>
+#include "overlayfs.h"
+
+static const char *ovl_whiteout_symlink = "(overlay-whiteout)";
+
+static struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
+ struct nameidata *nd)
+{
+ int err = ovl_do_lookup(dentry);
+
+ if (err)
+ return ERR_PTR(err);
+
+ return NULL;
+}
+
+static int ovl_whiteout(struct dentry *upperdir, struct dentry *dentry)
+{
+ int err;
+ struct dentry *newdentry;
+ const struct cred *old_cred;
+ struct cred *override_cred;
+
+ /* FIXME: recheck lower dentry to see if whiteout is really needed */
+
+ err = -ENOMEM;
+ override_cred = prepare_creds();
+ if (!override_cred)
+ goto out;
+
+ /*
+ * CAP_SYS_ADMIN for setxattr
+ * CAP_DAC_OVERRIDE for symlink creation
+ * CAP_FOWNER for unlink in sticky directory
+ */
+ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+ cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+ cap_raise(override_cred->cap_effective, CAP_FOWNER);
+ override_cred->fsuid = 0;
+ override_cred->fsgid = 0;
+ old_cred = override_creds(override_cred);
+
+ newdentry = lookup_one_len(dentry->d_name.name, upperdir,
+ dentry->d_name.len);
+ err = PTR_ERR(newdentry);
+ if (IS_ERR(newdentry))
+ goto out_put_cred;
+
+ /* Just been removed within the same locked region */
+ WARN_ON(newdentry->d_inode);
+
+ err = vfs_symlink(upperdir->d_inode, newdentry, ovl_whiteout_symlink);
+ if (err)
+ goto out_dput;
+
+ ovl_dentry_version_inc(dentry->d_parent);
+
+ err = vfs_setxattr(newdentry, ovl_whiteout_xattr, "y", 1, 0);
+ if (err)
+ vfs_unlink(upperdir->d_inode, newdentry);
+
+out_dput:
+ dput(newdentry);
+out_put_cred:
+ revert_creds(old_cred);
+ put_cred(override_cred);
+out:
+ if (err) {
+ /*
+ * There's no way to recover from failure to whiteout.
+ * What should we do? Log a big fat error and... ?
+ */
+ printk(KERN_ERR "overlayfs: ERROR - failed to whiteout '%s'\n",
+ dentry->d_name.name);
+ }
+
+ return err;
+}
+
+static struct dentry *ovl_lookup_create(struct dentry *upperdir,
+ struct dentry *template)
+{
+ int err;
+ struct dentry *newdentry;
+ struct qstr *name = &template->d_name;
+
+ newdentry = lookup_one_len(name->name, upperdir, name->len);
+ if (IS_ERR(newdentry))
+ return newdentry;
+
+ if (newdentry->d_inode) {
+ const struct cred *old_cred;
+ struct cred *override_cred;
+
+ /* No need to check whiteout if lower parent is non-existent */
+ err = -EEXIST;
+ if (!ovl_dentry_lower(template->d_parent))
+ goto out_dput;
+
+ if (!S_ISLNK(newdentry->d_inode->i_mode))
+ goto out_dput;
+
+ err = -ENOMEM;
+ override_cred = prepare_creds();
+ if (!override_cred)
+ goto out_dput;
+
+ /*
+ * CAP_SYS_ADMIN for getxattr
+ * CAP_FOWNER for unlink in sticky directory
+ */
+ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+ cap_raise(override_cred->cap_effective, CAP_FOWNER);
+ old_cred = override_creds(override_cred);
+
+ err = -EEXIST;
+ if (ovl_is_whiteout(newdentry))
+ err = vfs_unlink(upperdir->d_inode, newdentry);
+
+ revert_creds(old_cred);
+ put_cred(override_cred);
+ if (err)
+ goto out_dput;
+
+ dput(newdentry);
+ newdentry = lookup_one_len(name->name, upperdir, name->len);
+ if (IS_ERR(newdentry)) {
+ ovl_whiteout(upperdir, template);
+ return newdentry;
+ }
+
+ /*
+ * Whiteout just been successfully removed, parent
+ * i_mutex is still held, there's no way the lookup
+ * could return positive.
+ */
+ WARN_ON(newdentry->d_inode);
+ }
+
+ return newdentry;
+
+out_dput:
+ dput(newdentry);
+ return ERR_PTR(err);
+}
+
+struct dentry *ovl_upper_create(struct dentry *upperdir, struct dentry *dentry,
+ struct kstat *stat, const char *link)
+{
+ int err;
+ struct dentry *newdentry;
+ struct inode *dir = upperdir->d_inode;
+
+ newdentry = ovl_lookup_create(upperdir, dentry);
+ if (IS_ERR(newdentry))
+ goto out;
+
+ switch (stat->mode & S_IFMT) {
+ case S_IFREG:
+ err = vfs_create(dir, newdentry, stat->mode, NULL);
+ break;
+
+ case S_IFDIR:
+ err = vfs_mkdir(dir, newdentry, stat->mode);
+ break;
+
+ case S_IFCHR:
+ case S_IFBLK:
+ case S_IFIFO:
+ case S_IFSOCK:
+ err = vfs_mknod(dir, newdentry, stat->mode, stat->rdev);
+ break;
+
+ case S_IFLNK:
+ err = vfs_symlink(dir, newdentry, link);
+ break;
+
+ default:
+ err = -EPERM;
+ }
+ if (err) {
+ if (ovl_dentry_is_opaque(dentry))
+ ovl_whiteout(upperdir, dentry);
+ dput(newdentry);
+ newdentry = ERR_PTR(err);
+ }
+
+out:
+ return newdentry;
+
+}
+
+static int ovl_set_opaque(struct dentry *upperdentry)
+{
+ int err;
+ const struct cred *old_cred;
+ struct cred *override_cred;
+
+ override_cred = prepare_creds();
+ if (!override_cred)
+ return -ENOMEM;
+
+ /* CAP_SYS_ADMIN for setxattr of "trusted" namespace */
+ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+ old_cred = override_creds(override_cred);
+ err = vfs_setxattr(upperdentry, ovl_opaque_xattr, "y", 1, 0);
+ revert_creds(old_cred);
+ put_cred(override_cred);
+
+ return err;
+}
+
+static int ovl_remove_opaque(struct dentry *upperdentry)
+{
+ int err;
+ const struct cred *old_cred;
+ struct cred *override_cred;
+
+ override_cred = prepare_creds();
+ if (!override_cred)
+ return -ENOMEM;
+
+ /* CAP_SYS_ADMIN for removexattr of "trusted" namespace */
+ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+ old_cred = override_creds(override_cred);
+ err = vfs_removexattr(upperdentry, ovl_opaque_xattr);
+ revert_creds(old_cred);
+ put_cred(override_cred);
+
+ return err;
+}
+
+static int ovl_dir_getattr(struct vfsmount *mnt, struct dentry *dentry,
+ struct kstat *stat)
+{
+ int err;
+ enum ovl_path_type type;
+ struct path realpath;
+
+ type = ovl_path_real(dentry, &realpath);
+ err = vfs_getattr(realpath.mnt, realpath.dentry, stat);
+ if (err)
+ return err;
+
+ stat->dev = dentry->d_sb->s_dev;
+ stat->ino = dentry->d_inode->i_ino;
+
+ /*
+ * It's probably not worth it to count subdirs to get the
+ * correct link count. nlink=1 seems to pacify 'find' and
+ * other utilities.
+ */
+ if (type == OVL_PATH_MERGE)
+ stat->nlink = 1;
+
+ return 0;
+}
+
+static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
+ const char *link)
+{
+ int err;
+ struct dentry *newdentry;
+ struct dentry *upperdir;
+ struct inode *inode;
+ struct kstat stat = {
+ .mode = mode,
+ .rdev = rdev,
+ };
+
+ err = -ENOMEM;
+ inode = ovl_new_inode(dentry->d_sb, mode, dentry->d_fsdata);
+ if (!inode)
+ goto out;
+
+ err = ovl_copy_up(dentry->d_parent);
+ if (err)
+ goto out_iput;
+
+ upperdir = ovl_dentry_upper(dentry->d_parent);
+ mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
+
+ newdentry = ovl_upper_create(upperdir, dentry, &stat, link);
+ err = PTR_ERR(newdentry);
+ if (IS_ERR(newdentry))
+ goto out_unlock;
+
+ ovl_dentry_version_inc(dentry->d_parent);
+ if (ovl_dentry_is_opaque(dentry) && S_ISDIR(mode)) {
+ err = ovl_set_opaque(newdentry);
+ if (err) {
+ vfs_rmdir(upperdir->d_inode, newdentry);
+ ovl_whiteout(upperdir, dentry);
+ goto out_dput;
+ }
+ }
+ ovl_dentry_update(dentry, newdentry);
+ d_instantiate(dentry, inode);
+ inode = NULL;
+ newdentry = NULL;
+ err = 0;
+
+out_dput:
+ dput(newdentry);
+out_unlock:
+ mutex_unlock(&upperdir->d_inode->i_mutex);
+out_iput:
+ iput(inode);
+out:
+ return err;
+}
+
+static int ovl_create(struct inode *dir, struct dentry *dentry, int mode,
+ struct nameidata *nd)
+{
+ return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
+}
+
+static int ovl_mkdir(struct inode *dir, struct dentry *dentry, int mode)
+{
+ return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
+}
+
+static int ovl_mknod(struct inode *dir, struct dentry *dentry, int mode,
+ dev_t rdev)
+{
+ return ovl_create_object(dentry, mode, rdev, NULL);
+}
+
+static int ovl_symlink(struct inode *dir, struct dentry *dentry,
+ const char *link)
+{
+ return ovl_create_object(dentry, S_IFLNK, 0, link);
+}
+
+static int ovl_do_remove(struct dentry *dentry, bool is_dir)
+{
+ int err;
+ enum ovl_path_type type;
+ struct path realpath;
+ struct dentry *upperdir;
+
+ err = ovl_copy_up(dentry->d_parent);
+ if (err)
+ return err;
+
+ upperdir = ovl_dentry_upper(dentry->d_parent);
+ mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
+ type = ovl_path_real(dentry, &realpath);
+ if (type != OVL_PATH_LOWER) {
+ err = -ESTALE;
+ if (realpath.dentry->d_parent != upperdir)
+ goto out_d_drop;
+
+ /* FIXME: create whiteout up front and rename to target */
+
+ if (is_dir)
+ err = vfs_rmdir(upperdir->d_inode, realpath.dentry);
+ else
+ err = vfs_unlink(upperdir->d_inode, realpath.dentry);
+ if (err)
+ goto out_d_drop;
+
+ ovl_dentry_version_inc(dentry->d_parent);
+ }
+
+ if (type != OVL_PATH_UPPER || ovl_dentry_is_opaque(dentry))
+ err = ovl_whiteout(upperdir, dentry);
+
+ /*
+ * Keeping this dentry hashed would mean having to release
+ * upperpath/lowerpath, which could only be done if we are the
+ * sole user of this dentry. Too tricky... Just unhash for
+ * now.
+ */
+out_d_drop:
+ d_drop(dentry);
+ mutex_unlock(&upperdir->d_inode->i_mutex);
+
+ return err;
+}
+
+static int ovl_unlink(struct inode *dir, struct dentry *dentry)
+{
+ return ovl_do_remove(dentry, false);
+}
+
+
+static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
+{
+ int err;
+ enum ovl_path_type type;
+
+ type = ovl_path_type(dentry);
+ if (type != OVL_PATH_UPPER) {
+ err = ovl_check_empty_and_clear(dentry, type);
+ if (err)
+ return err;
+ }
+
+ return ovl_do_remove(dentry, true);
+}
+
+static int ovl_link(struct dentry *old, struct inode *newdir,
+ struct dentry *new)
+{
+ int err;
+ struct dentry *olddentry;
+ struct dentry *newdentry;
+ struct dentry *upperdir;
+
+ err = ovl_copy_up(old);
+ if (err)
+ goto out;
+
+ err = ovl_copy_up(new->d_parent);
+ if (err)
+ goto out;
+
+ upperdir = ovl_dentry_upper(new->d_parent);
+ mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
+ newdentry = ovl_lookup_create(upperdir, new);
+ err = PTR_ERR(newdentry);
+ if (IS_ERR(newdentry))
+ goto out_unlock;
+
+ olddentry = ovl_dentry_upper(old);
+ err = vfs_link(olddentry, upperdir->d_inode, newdentry);
+ if (!err) {
+ ovl_dentry_version_inc(new->d_parent);
+ ovl_dentry_update(new, newdentry);
+
+ ihold(old->d_inode);
+ d_instantiate(new, old->d_inode);
+ } else {
+ if (ovl_dentry_is_opaque(new))
+ ovl_whiteout(upperdir, new);
+ dput(newdentry);
+ }
+out_unlock:
+ mutex_unlock(&upperdir->d_inode->i_mutex);
+out:
+ return err;
+
+}
+
+static int ovl_rename(struct inode *olddir, struct dentry *old,
+ struct inode *newdir, struct dentry *new)
+{
+ int err;
+ enum ovl_path_type old_type;
+ struct dentry *old_upperdir;
+ struct dentry *new_upperdir;
+ struct dentry *olddentry;
+ struct dentry *newdentry;
+ struct dentry *trap;
+ bool old_opaque;
+ bool new_opaque;
+ bool is_dir = S_ISDIR(old->d_inode->i_mode);
+
+ /* Don't copy up directory trees */
+ old_type = ovl_path_type(old);
+ if (old_type != OVL_PATH_UPPER && is_dir)
+ return -EXDEV;
+
+ if (new->d_inode) {
+ enum ovl_path_type new_type;
+
+ new_type = ovl_path_type(new);
+
+ if (new_type == OVL_PATH_LOWER && old_type == OVL_PATH_LOWER) {
+ if (ovl_dentry_lower(old)->d_inode ==
+ ovl_dentry_lower(new)->d_inode)
+ return 0;
+ }
+ if (new_type != OVL_PATH_LOWER && old_type != OVL_PATH_LOWER) {
+ if (ovl_dentry_upper(old)->d_inode ==
+ ovl_dentry_upper(new)->d_inode)
+ return 0;
+ }
+
+ if (new_type != OVL_PATH_UPPER &&
+ S_ISDIR(new->d_inode->i_mode)) {
+ err = ovl_check_empty_and_clear(new, new_type);
+ if (err)
+ return err;
+ }
+ }
+
+ err = ovl_copy_up(old);
+ if (err)
+ return err;
+
+ err = ovl_copy_up(new->d_parent);
+ if (err)
+ return err;
+
+ old_upperdir = ovl_dentry_upper(old->d_parent);
+ new_upperdir = ovl_dentry_upper(new->d_parent);
+
+ trap = lock_rename(new_upperdir, old_upperdir);
+
+ olddentry = ovl_dentry_upper(old);
+ newdentry = ovl_dentry_upper(new);
+ if (newdentry) {
+ dget(newdentry);
+ } else {
+ newdentry = ovl_lookup_create(new_upperdir, new);
+ err = PTR_ERR(newdentry);
+ if (IS_ERR(newdentry))
+ goto out_unlock;
+ }
+
+ err = -ESTALE;
+ if (olddentry->d_parent != old_upperdir)
+ goto out_dput;
+ if (newdentry->d_parent != new_upperdir)
+ goto out_dput;
+ if (olddentry == trap)
+ goto out_dput;
+ if (newdentry == trap)
+ goto out_dput;
+
+ old_opaque = ovl_dentry_is_opaque(old);
+ new_opaque = ovl_dentry_is_opaque(new) ||
+ ovl_path_type(new) != OVL_PATH_UPPER;
+
+ if (is_dir && !old_opaque && new_opaque) {
+ err = ovl_set_opaque(olddentry);
+ if (err)
+ goto out_dput;
+ }
+
+ err = vfs_rename(old_upperdir->d_inode, olddentry,
+ new_upperdir->d_inode, newdentry);
+
+ if (err) {
+ if (ovl_dentry_is_opaque(new))
+ ovl_whiteout(new_upperdir, new);
+ if (is_dir && !old_opaque && new_opaque)
+ ovl_remove_opaque(olddentry);
+ goto out_dput;
+ }
+
+ if (old_type != OVL_PATH_UPPER || old_opaque)
+ err = ovl_whiteout(old_upperdir, old);
+ if (is_dir && old_opaque && !new_opaque)
+ ovl_remove_opaque(olddentry);
+
+ if (old_opaque != new_opaque)
+ ovl_dentry_set_opaque(old, new_opaque);
+
+ ovl_dentry_version_inc(old->d_parent);
+ ovl_dentry_version_inc(new->d_parent);
+
+out_dput:
+ dput(newdentry);
+out_unlock:
+ unlock_rename(new_upperdir, old_upperdir);
+ return err;
+}
+
+const struct inode_operations ovl_dir_inode_operations = {
+ .lookup = ovl_lookup,
+ .mkdir = ovl_mkdir,
+ .symlink = ovl_symlink,
+ .unlink = ovl_unlink,
+ .rmdir = ovl_rmdir,
+ .rename = ovl_rename,
+ .link = ovl_link,
+ .setattr = ovl_setattr,
+ .create = ovl_create,
+ .mknod = ovl_mknod,
+ .permission = ovl_permission,
+ .getattr = ovl_dir_getattr,
+ .setxattr = ovl_setxattr,
+ .getxattr = ovl_getxattr,
+ .listxattr = ovl_listxattr,
+ .removexattr = ovl_removexattr,
+};
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
new file mode 100644
index 0000000..3c15d54
--- /dev/null
+++ b/fs/overlayfs/inode.c
@@ -0,0 +1,374 @@
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/xattr.h>
+#include "overlayfs.h"
+
+int ovl_setattr(struct dentry *dentry, struct iattr *attr)
+{
+ struct dentry *upperdentry;
+ int err;
+
+ if ((attr->ia_valid & ATTR_SIZE) && !ovl_dentry_upper(dentry))
+ err = ovl_copy_up_truncate(dentry, attr->ia_size);
+ else
+ err = ovl_copy_up(dentry);
+ if (err)
+ return err;
+
+ upperdentry = ovl_dentry_upper(dentry);
+
+ if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
+ attr->ia_valid &= ~ATTR_MODE;
+
+ mutex_lock(&upperdentry->d_inode->i_mutex);
+ err = notify_change(upperdentry, attr);
+ mutex_unlock(&upperdentry->d_inode->i_mutex);
+
+ return err;
+}
+
+static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
+ struct kstat *stat)
+{
+ struct path realpath;
+
+ ovl_path_real(dentry, &realpath);
+ return vfs_getattr(realpath.mnt, realpath.dentry, stat);
+}
+
+int ovl_permission(struct inode *inode, int mask, unsigned int flags)
+{
+ struct ovl_entry *oe;
+ struct dentry *alias = NULL;
+ struct inode *realinode;
+ struct dentry *realdentry;
+ bool is_upper;
+ int err;
+
+ if (S_ISDIR(inode->i_mode)) {
+ oe = inode->i_private;
+ } else if (flags & IPERM_FLAG_RCU) {
+ return -ECHILD;
+ } else {
+ /*
+ * For non-directories find an alias and get the info
+ * from there.
+ */
+ spin_lock(&inode->i_lock);
+ if (WARN_ON(list_empty(&inode->i_dentry))) {
+ spin_unlock(&inode->i_lock);
+ return -ENOENT;
+ }
+ alias = list_entry(inode->i_dentry.next, struct dentry, d_alias);
+ dget(alias);
+ spin_unlock(&inode->i_lock);
+ oe = alias->d_fsdata;
+ }
+
+ realdentry = ovl_entry_real(oe, &is_upper);
+
+ /* Careful in RCU walk mode */
+ realinode = ACCESS_ONCE(realdentry->d_inode);
+ if (!realinode) {
+ WARN_ON(!(flags & IPERM_FLAG_RCU));
+ return -ENOENT;
+ }
+
+ if (mask & MAY_WRITE) {
+ umode_t mode = realinode->i_mode;
+
+ /*
+ * Writes will always be redirected to upper layer, so
+ * ignore lower layer being read-only.
+ */
+ err = -EROFS;
+ if (is_upper && IS_RDONLY(realinode) &&
+ (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
+ goto out_dput;
+
+ /*
+ * Nobody gets write access to an immutable file.
+ */
+ err = -EACCES;
+ if (IS_IMMUTABLE(realinode))
+ goto out_dput;
+ }
+
+ if (realinode->i_op->permission)
+ err = realinode->i_op->permission(realinode, mask, flags);
+ else
+ err = generic_permission(realinode, mask, flags,
+ realinode->i_op->check_acl);
+out_dput:
+ dput(alias);
+ return err;
+}
+
+
+struct ovl_link_data {
+ struct dentry *realdentry;
+ void *cookie;
+};
+
+static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
+{
+ void *ret;
+ struct dentry *realdentry;
+ struct inode *realinode;
+
+ realdentry = ovl_dentry_real(dentry);
+ realinode = realdentry->d_inode;
+
+ if (WARN_ON(!realinode->i_op->follow_link))
+ return ERR_PTR(-EPERM);
+
+ ret = realinode->i_op->follow_link(realdentry, nd);
+ if (IS_ERR(ret))
+ return ret;
+
+ if (realinode->i_op->put_link) {
+ struct ovl_link_data *data;
+
+ data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
+ if (!data) {
+ realinode->i_op->put_link(realdentry, nd, ret);
+ return ERR_PTR(-ENOMEM);
+ }
+ data->realdentry = realdentry;
+ data->cookie = ret;
+
+ return data;
+ } else {
+ return NULL;
+ }
+}
+
+static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)
+{
+ struct inode *realinode;
+ struct ovl_link_data *data = c;
+
+ if (!data)
+ return;
+
+ realinode = data->realdentry->d_inode;
+ realinode->i_op->put_link(data->realdentry, nd, data->cookie);
+ kfree(data);
+}
+
+static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
+{
+ struct path realpath;
+ struct inode *realinode;
+
+ ovl_path_real(dentry, &realpath);
+ realinode = realpath.dentry->d_inode;
+
+ if (!realinode->i_op->readlink)
+ return -EINVAL;
+
+ touch_atime(realpath.mnt, realpath.dentry);
+
+ return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
+}
+
+
+static bool ovl_is_private_xattr(const char *name)
+{
+ return strncmp(name, "trusted.overlay.", 14) == 0;
+}
+
+int ovl_setxattr(struct dentry *dentry, const char *name,
+ const void *value, size_t size, int flags)
+{
+ int err;
+ struct dentry *upperdentry;
+
+ if (ovl_is_private_xattr(name))
+ return -EPERM;
+
+ err = ovl_copy_up(dentry);
+ if (err)
+ return err;
+
+ upperdentry = ovl_dentry_upper(dentry);
+ return vfs_setxattr(upperdentry, name, value, size, flags);
+}
+
+ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
+ void *value, size_t size)
+{
+ if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
+ ovl_is_private_xattr(name))
+ return -ENODATA;
+
+ return vfs_getxattr(ovl_dentry_real(dentry), name, value, size);
+}
+
+ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
+{
+ ssize_t res;
+ int off;
+
+ res = vfs_listxattr(ovl_dentry_real(dentry), list, size);
+ if (res <= 0 || size == 0)
+ return res;
+
+ if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE)
+ return res;
+
+ /* filter out private xattrs */
+ for (off = 0; off < res;) {
+ char *s = list + off;
+ size_t slen = strlen(s) + 1;
+
+ BUG_ON(off + slen > res);
+
+ if (ovl_is_private_xattr(s)) {
+ res -= slen;
+ memmove(s, s + slen, res - off);
+ } else {
+ off += slen;
+ }
+ }
+
+ return res;
+}
+
+int ovl_removexattr(struct dentry *dentry, const char *name)
+{
+ int err;
+ struct path realpath;
+ enum ovl_path_type type;
+
+ if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
+ ovl_is_private_xattr(name))
+ return -ENODATA;
+
+ type = ovl_path_real(dentry, &realpath);
+ if (type == OVL_PATH_LOWER) {
+ err = vfs_getxattr(realpath.dentry, name, NULL, 0);
+ if (err < 0)
+ return err;
+
+ err = ovl_copy_up(dentry);
+ if (err)
+ return err;
+
+ ovl_path_upper(dentry, &realpath);
+ }
+
+ return vfs_removexattr(realpath.dentry, name);
+}
+
+static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
+ struct dentry *realdentry)
+{
+ if (type != OVL_PATH_LOWER)
+ return false;
+
+ if (special_file(realdentry->d_inode->i_mode))
+ return false;
+
+ if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
+ return false;
+
+ return true;
+}
+
+static struct file *ovl_open(struct dentry *dentry, int flags,
+ const struct cred *cred)
+{
+ int err;
+ struct path realpath;
+ enum ovl_path_type type;
+
+ type = ovl_path_real(dentry, &realpath);
+ if (ovl_open_need_copy_up(flags, type, realpath.dentry)) {
+ if (flags & O_TRUNC)
+ err = ovl_copy_up_truncate(dentry, 0);
+ else
+ err = ovl_copy_up(dentry);
+ if (err)
+ return ERR_PTR(err);
+
+ ovl_path_upper(dentry, &realpath);
+ }
+
+ return vfs_open(&realpath, flags, cred);
+}
+
+static const struct inode_operations ovl_file_inode_operations = {
+ .setattr = ovl_setattr,
+ .permission = ovl_permission,
+ .getattr = ovl_getattr,
+ .setxattr = ovl_setxattr,
+ .getxattr = ovl_getxattr,
+ .listxattr = ovl_listxattr,
+ .removexattr = ovl_removexattr,
+ .open = ovl_open,
+};
+
+static const struct inode_operations ovl_symlink_inode_operations = {
+ .setattr = ovl_setattr,
+ .follow_link = ovl_follow_link,
+ .put_link = ovl_put_link,
+ .readlink = ovl_readlink,
+ .getattr = ovl_getattr,
+ .setxattr = ovl_setxattr,
+ .getxattr = ovl_getxattr,
+ .listxattr = ovl_listxattr,
+ .removexattr = ovl_removexattr,
+};
+
+struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
+ struct ovl_entry *oe)
+{
+ struct inode *inode;
+
+ inode = new_inode(sb);
+ if (!inode)
+ return NULL;
+
+ mode &= S_IFMT;
+
+ inode->i_ino = get_next_ino();
+ inode->i_mode = mode;
+ inode->i_flags |= S_NOATIME | S_NOCMTIME;
+
+ switch (mode) {
+ case S_IFDIR:
+ inode->i_private = oe;
+ inode->i_op = &ovl_dir_inode_operations;
+ inode->i_fop = &ovl_dir_operations;
+ break;
+
+ case S_IFLNK:
+ inode->i_op = &ovl_symlink_inode_operations;
+ break;
+
+ case S_IFREG:
+ case S_IFSOCK:
+ case S_IFBLK:
+ case S_IFCHR:
+ case S_IFIFO:
+ inode->i_op = &ovl_file_inode_operations;
+ break;
+
+ default:
+ WARN(1, "illegal file type: %i\n", mode);
+ inode = NULL;
+ }
+
+ return inode;
+
+}
diff --git a/fs/overlayfs/overlayfs.c b/fs/overlayfs/overlayfs.c
new file mode 100644
index 0000000..0901eda
--- /dev/null
+++ b/fs/overlayfs/overlayfs.c
@@ -0,0 +1,576 @@
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/xattr.h>
+#include <linux/security.h>
+#include <linux/mount.h>
+#include <linux/slab.h>
+#include <linux/parser.h>
+#include <linux/module.h>
+#include "overlayfs.h"
+
+MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
+MODULE_DESCRIPTION("Overlay filesystem");
+MODULE_LICENSE("GPL");
+
+struct ovl_fs {
+ struct vfsmount *upper_mnt;
+ struct vfsmount *lower_mnt;
+};
+
+struct ovl_entry {
+ struct dentry *__upperdentry;
+ struct dentry *lowerdentry;
+ union {
+ struct {
+ u64 version;
+ bool opaque;
+ };
+ struct rcu_head rcu;
+ };
+};
+
+const char *ovl_whiteout_xattr = "trusted.overlay.whiteout";
+const char *ovl_opaque_xattr = "trusted.overlay.opaque";
+
+
+enum ovl_path_type ovl_path_type(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ if (oe->__upperdentry) {
+ if (oe->lowerdentry && S_ISDIR(dentry->d_inode->i_mode))
+ return OVL_PATH_MERGE;
+ else
+ return OVL_PATH_UPPER;
+ } else {
+ return OVL_PATH_LOWER;
+ }
+}
+
+static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
+{
+ struct dentry *upperdentry = ACCESS_ONCE(oe->__upperdentry);
+ smp_read_barrier_depends();
+ return upperdentry;
+}
+
+void ovl_path_upper(struct dentry *dentry, struct path *path)
+{
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ path->mnt = ofs->upper_mnt;
+ path->dentry = ovl_upperdentry_dereference(oe);
+}
+
+void ovl_path_lower(struct dentry *dentry, struct path *path)
+{
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ path->mnt = ofs->lower_mnt;
+ path->dentry = oe->lowerdentry;
+}
+
+enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
+{
+
+ enum ovl_path_type type = ovl_path_type(dentry);
+
+ if (type == OVL_PATH_LOWER)
+ ovl_path_lower(dentry, path);
+ else
+ ovl_path_upper(dentry, path);
+
+ return type;
+}
+
+struct dentry *ovl_dentry_upper(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ return ovl_upperdentry_dereference(oe);
+}
+
+struct dentry *ovl_dentry_lower(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ return oe->lowerdentry;
+}
+
+struct dentry *ovl_dentry_real(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+ struct dentry *realdentry;
+
+ realdentry = ovl_upperdentry_dereference(oe);
+ if (!realdentry)
+ realdentry = oe->lowerdentry;
+
+ return realdentry;
+}
+
+struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
+{
+ struct dentry *realdentry;
+
+ realdentry = ovl_upperdentry_dereference(oe);
+ if (realdentry) {
+ *is_upper = true;
+ } else {
+ realdentry = oe->lowerdentry;
+ *is_upper = false;
+ }
+ return realdentry;
+}
+
+bool ovl_dentry_is_opaque(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+ return oe->opaque;
+}
+
+void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+ oe->opaque = opaque;
+}
+
+void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
+ WARN_ON(oe->__upperdentry);
+ smp_wmb();
+ oe->__upperdentry = upperdentry;
+}
+
+void ovl_dentry_version_inc(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
+ oe->version++;
+}
+
+u64 ovl_dentry_version_get(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
+ return oe->version;
+}
+
+bool ovl_is_whiteout(struct dentry *dentry)
+{
+ int res;
+ char val;
+
+ if (!dentry)
+ return false;
+ if (!dentry->d_inode)
+ return false;
+ if (!S_ISLNK(dentry->d_inode->i_mode))
+ return false;
+
+ res = vfs_getxattr(dentry, ovl_whiteout_xattr, &val, 1);
+ if (res == 1 && val == 'y')
+ return true;
+
+ return false;
+}
+
+static bool ovl_is_opaquedir(struct dentry *dentry)
+{
+ int res;
+ char val;
+
+ if (!S_ISDIR(dentry->d_inode->i_mode))
+ return false;
+
+ res = vfs_getxattr(dentry, ovl_opaque_xattr, &val, 1);
+ if (res == 1 && val == 'y')
+ return true;
+
+ return false;
+}
+
+static void ovl_entry_free(struct rcu_head *head)
+{
+ struct ovl_entry *oe = container_of(head, struct ovl_entry, rcu);
+ kfree(oe);
+}
+
+static void ovl_dentry_release(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ if (oe) {
+ dput(oe->__upperdentry);
+ dput(oe->lowerdentry);
+ call_rcu(&oe->rcu, ovl_entry_free);
+ }
+}
+
+const struct dentry_operations ovl_dentry_operations = {
+ .d_release = ovl_dentry_release,
+};
+
+static struct ovl_entry *ovl_alloc_entry(void)
+{
+ return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL);
+}
+
+static struct dentry *ovl_lookup_real(struct dentry *dir, struct qstr *name)
+{
+ struct dentry *dentry;
+
+ mutex_lock(&dir->d_inode->i_mutex);
+ dentry = lookup_one_len(name->name, dir, name->len);
+ mutex_unlock(&dir->d_inode->i_mutex);
+
+ if (IS_ERR(dentry)) {
+ if (PTR_ERR(dentry) == -ENOENT)
+ dentry = NULL;
+ } else if (!dentry->d_inode) {
+ dput(dentry);
+ dentry = NULL;
+ }
+ return dentry;
+}
+
+int ovl_do_lookup(struct dentry *dentry)
+{
+ struct ovl_entry *oe;
+ struct dentry *upperdir;
+ struct dentry *lowerdir;
+ struct dentry *upperdentry = NULL;
+ struct dentry *lowerdentry = NULL;
+ struct inode *inode = NULL;
+ int err;
+
+ err = -ENOMEM;
+ oe = ovl_alloc_entry();
+ if (!oe)
+ goto out;
+
+ upperdir = ovl_dentry_upper(dentry->d_parent);
+ lowerdir = ovl_dentry_lower(dentry->d_parent);
+
+ if (upperdir) {
+ upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
+ err = PTR_ERR(upperdentry);
+ if (IS_ERR(upperdentry))
+ goto out_put_dir;
+
+ if (lowerdir && upperdentry &&
+ (S_ISLNK(upperdentry->d_inode->i_mode) ||
+ S_ISDIR(upperdentry->d_inode->i_mode))) {
+ const struct cred *old_cred;
+ struct cred *override_cred;
+
+ err = -ENOMEM;
+ override_cred = prepare_creds();
+ if (!override_cred)
+ goto out_dput_upper;
+
+ /* CAP_SYS_ADMIN needed for getxattr */
+ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+ old_cred = override_creds(override_cred);
+
+ if (ovl_is_opaquedir(upperdentry)) {
+ oe->opaque = true;
+ } else if (ovl_is_whiteout(upperdentry)) {
+ dput(upperdentry);
+ upperdentry = NULL;
+ oe->opaque = true;
+ }
+ revert_creds(old_cred);
+ put_cred(override_cred);
+ }
+ }
+ if (lowerdir && !oe->opaque) {
+ lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name);
+ err = PTR_ERR(lowerdentry);
+ if (IS_ERR(lowerdentry))
+ goto out_dput_upper;
+ }
+
+ if (lowerdentry && upperdentry &&
+ (!S_ISDIR(upperdentry->d_inode->i_mode) ||
+ !S_ISDIR(lowerdentry->d_inode->i_mode))) {
+ dput(lowerdentry);
+ lowerdentry = NULL;
+ oe->opaque = true;
+ }
+
+ if (lowerdentry || upperdentry) {
+ struct dentry *realdentry;
+
+ realdentry = upperdentry ? upperdentry : lowerdentry;
+ err = -ENOMEM;
+ inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode, oe);
+ if (!inode)
+ goto out_dput;
+ }
+
+ if (upperdentry)
+ oe->__upperdentry = upperdentry;
+
+ if (lowerdentry)
+ oe->lowerdentry = lowerdentry;
+
+ dentry->d_fsdata = oe;
+ dentry->d_op = &ovl_dentry_operations;
+ d_add(dentry, inode);
+
+ return 0;
+
+out_dput:
+ dput(lowerdentry);
+out_dput_upper:
+ dput(upperdentry);
+out_put_dir:
+ kfree(oe);
+out:
+ return err;
+}
+
+static void ovl_put_super(struct super_block *sb)
+{
+ struct ovl_fs *ufs = sb->s_fs_info;
+
+ if (!(sb->s_flags & MS_RDONLY))
+ mnt_drop_write(ufs->upper_mnt);
+
+ mntput(ufs->upper_mnt);
+ mntput(ufs->lower_mnt);
+
+ kfree(ufs);
+}
+
+static int ovl_remount_fs(struct super_block *sb, int *flagsp, char *data)
+{
+ int flags = *flagsp;
+ struct ovl_fs *ufs = sb->s_fs_info;
+
+ /* When remounting rw or ro, we need to adjust the write access to the
+ * upper fs.
+ */
+ if (((flags ^ sb->s_flags) & MS_RDONLY) == 0)
+ /* No change to readonly status */
+ return 0;
+
+ if (flags & MS_RDONLY) {
+ mnt_drop_write(ufs->upper_mnt);
+ return 0;
+ } else
+ return mnt_want_write(ufs->upper_mnt);
+}
+
+static const struct super_operations ovl_super_operations = {
+ .put_super = ovl_put_super,
+ .remount_fs = ovl_remount_fs,
+};
+
+struct ovl_config {
+ char *lowerdir;
+ char *upperdir;
+};
+
+enum {
+ Opt_lowerdir,
+ Opt_upperdir,
+ Opt_err,
+};
+
+static const match_table_t ovl_tokens = {
+ {Opt_lowerdir, "lowerdir=%s"},
+ {Opt_upperdir, "upperdir=%s"},
+ {Opt_err, NULL}
+};
+
+static int ovl_parse_opt(char *opt, struct ovl_config *config)
+{
+ char *p;
+
+ config->upperdir = NULL;
+ config->lowerdir = NULL;
+
+ while ((p = strsep(&opt, ",")) != NULL) {
+ int token;
+ substring_t args[MAX_OPT_ARGS];
+
+ if (!*p)
+ continue;
+
+ token = match_token(p, ovl_tokens, args);
+ switch (token) {
+ case Opt_upperdir:
+ kfree(config->upperdir);
+ config->upperdir = match_strdup(&args[0]);
+ if (!config->upperdir)
+ return -ENOMEM;
+ break;
+
+ case Opt_lowerdir:
+ kfree(config->lowerdir);
+ config->lowerdir = match_strdup(&args[0]);
+ if (!config->lowerdir)
+ return -ENOMEM;
+ break;
+
+ default:
+ return -EINVAL;
+ }
+ }
+ return 0;
+}
+
+static int ovl_fill_super(struct super_block *sb, void *data, int silent)
+{
+ struct path lowerpath;
+ struct path upperpath;
+ struct inode *root_inode;
+ struct dentry *root_dentry;
+ struct ovl_entry *oe;
+ struct ovl_fs *ufs;
+ struct ovl_config config;
+ int err;
+
+ err = ovl_parse_opt((char *) data, &config);
+ if (err)
+ goto out;
+
+ err = -EINVAL;
+ if (!config.upperdir || !config.lowerdir) {
+ printk(KERN_ERR "overlayfs: missing upperdir or lowerdir\n");
+ goto out_free_config;
+ }
+
+ err = -ENOMEM;
+ ufs = kmalloc(sizeof(struct ovl_fs), GFP_KERNEL);
+ if (!ufs)
+ goto out_free_config;
+
+ oe = ovl_alloc_entry();
+ if (oe == NULL)
+ goto out_free_ufs;
+
+ root_inode = ovl_new_inode(sb, S_IFDIR, oe);
+ if (!root_inode)
+ goto out_free_oe;
+
+ err = kern_path(config.upperdir, LOOKUP_FOLLOW, &upperpath);
+ if (err)
+ goto out_put_root;
+
+ err = kern_path(config.lowerdir, LOOKUP_FOLLOW, &lowerpath);
+ if (err)
+ goto out_put_upperpath;
+
+ err = -ENOTDIR;
+ if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) ||
+ !S_ISDIR(lowerpath.dentry->d_inode->i_mode))
+ goto out_put_lowerpath;
+
+ ufs->upper_mnt = clone_private_mount(&upperpath);
+ err = PTR_ERR(ufs->upper_mnt);
+ if (IS_ERR(ufs->upper_mnt)) {
+ printk(KERN_ERR "overlayfs: failed to clone upperpath\n");
+ goto out_put_lowerpath;
+ }
+
+ ufs->lower_mnt = clone_private_mount(&lowerpath);
+ err = PTR_ERR(ufs->lower_mnt);
+ if (IS_ERR(ufs->lower_mnt)) {
+ printk(KERN_ERR "overlayfs: failed to clone lowerpath\n");
+ goto out_put_upper_mnt;
+ }
+
+ if (!(sb->s_flags & MS_RDONLY)) {
+ err = mnt_want_write(ufs->upper_mnt);
+ if (err)
+ goto out_put_lower_mnt;
+ }
+
+ err = -ENOMEM;
+ root_dentry = d_alloc_root(root_inode);
+ if (!root_dentry)
+ goto out_drop_write;
+
+ mntput(upperpath.mnt);
+ mntput(lowerpath.mnt);
+
+ oe->__upperdentry = upperpath.dentry;
+ oe->lowerdentry = lowerpath.dentry;
+
+ root_dentry->d_fsdata = oe;
+ root_dentry->d_op = &ovl_dentry_operations;
+
+ sb->s_op = &ovl_super_operations;
+ sb->s_root = root_dentry;
+ sb->s_fs_info = ufs;
+
+ return 0;
+
+out_drop_write:
+ if (!(sb->s_flags & MS_RDONLY))
+ mnt_drop_write(ufs->upper_mnt);
+out_put_lower_mnt:
+ mntput(ufs->lower_mnt);
+out_put_upper_mnt:
+ mntput(ufs->upper_mnt);
+out_put_lowerpath:
+ path_put(&lowerpath);
+out_put_upperpath:
+ path_put(&upperpath);
+out_put_root:
+ iput(root_inode);
+out_free_oe:
+ kfree(oe);
+out_free_ufs:
+ kfree(ufs);
+out_free_config:
+ kfree(config.lowerdir);
+ kfree(config.upperdir);
+out:
+ return err;
+}
+
+static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
+ const char *dev_name, void *raw_data)
+{
+ return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
+}
+
+static struct file_system_type ovl_fs_type = {
+ .owner = THIS_MODULE,
+ .name = "overlayfs",
+ .mount = ovl_mount,
+ .kill_sb = kill_anon_super,
+};
+
+static int __init ovl_init(void)
+{
+ return register_filesystem(&ovl_fs_type);
+}
+
+static void __exit ovl_exit(void)
+{
+ unregister_filesystem(&ovl_fs_type);
+}
+
+module_init(ovl_init);
+module_exit(ovl_exit);
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
new file mode 100644
index 0000000..e4928e2
--- /dev/null
+++ b/fs/overlayfs/overlayfs.h
@@ -0,0 +1,63 @@
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+struct ovl_entry;
+
+enum ovl_path_type {
+ OVL_PATH_UPPER,
+ OVL_PATH_MERGE,
+ OVL_PATH_LOWER,
+};
+
+extern const char *ovl_opaque_xattr;
+extern const char *ovl_whiteout_xattr;
+extern const struct dentry_operations ovl_dentry_operations;
+
+enum ovl_path_type ovl_path_type(struct dentry *dentry);
+u64 ovl_dentry_version_get(struct dentry *dentry);
+void ovl_dentry_version_inc(struct dentry *dentry);
+void ovl_path_upper(struct dentry *dentry, struct path *path);
+void ovl_path_lower(struct dentry *dentry, struct path *path);
+enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
+struct dentry *ovl_dentry_upper(struct dentry *dentry);
+struct dentry *ovl_dentry_lower(struct dentry *dentry);
+struct dentry *ovl_dentry_real(struct dentry *dentry);
+struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper);
+bool ovl_dentry_is_opaque(struct dentry *dentry);
+void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque);
+bool ovl_is_whiteout(struct dentry *dentry);
+void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry);
+void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque);
+int ovl_do_lookup(struct dentry *dentry);
+
+struct dentry *ovl_upper_create(struct dentry *upperdir, struct dentry *dentry,
+ struct kstat *stat, const char *link);
+
+/* readdir.c */
+extern const struct file_operations ovl_dir_operations;
+int ovl_check_empty_and_clear(struct dentry *dentry, enum ovl_path_type type);
+
+/* inode.c */
+int ovl_setattr(struct dentry *dentry, struct iattr *attr);
+int ovl_permission(struct inode *inode, int mask, unsigned int flags);
+int ovl_setxattr(struct dentry *dentry, const char *name,
+ const void *value, size_t size, int flags);
+ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
+ void *value, size_t size);
+ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
+int ovl_removexattr(struct dentry *dentry, const char *name);
+
+struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
+ struct ovl_entry *oe);
+/* dir.c */
+extern const struct inode_operations ovl_dir_inode_operations;
+
+/* copy_up.c */
+int ovl_copy_up(struct dentry *dentry);
+int ovl_copy_up_truncate(struct dentry *dentry, loff_t size);
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
new file mode 100644
index 0000000..9b8004c
--- /dev/null
+++ b/fs/overlayfs/readdir.c
@@ -0,0 +1,560 @@
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/namei.h>
+#include <linux/file.h>
+#include <linux/xattr.h>
+#include <linux/rbtree.h>
+#include <linux/security.h>
+#include "overlayfs.h"
+
+struct ovl_cache_entry {
+ const char *name;
+ unsigned int len;
+ unsigned int type;
+ u64 ino;
+ bool is_whiteout;
+ struct list_head l_node;
+ struct rb_node node;
+};
+
+struct ovl_readdir_data {
+ struct rb_root *root;
+ struct list_head *list;
+ struct list_head *middle;
+ struct dentry *dir;
+ int count;
+ int err;
+};
+
+struct ovl_dir_file {
+ bool is_real;
+ bool is_cached;
+ struct list_head cursor;
+ u64 cache_version;
+ struct list_head cache;
+ struct file *realfile;
+};
+
+static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
+{
+ return container_of(n, struct ovl_cache_entry, node);
+}
+
+static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
+ const char *name, int len)
+{
+ struct rb_node *node = root->rb_node;
+ int cmp;
+
+ while (node) {
+ struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
+
+ cmp = strncmp(name, p->name, len);
+ if (cmp > 0)
+ node = p->node.rb_right;
+ else if (cmp < 0 || len < p->len)
+ node = p->node.rb_left;
+ else
+ return p;
+ }
+
+ return NULL;
+}
+
+static struct ovl_cache_entry *ovl_cache_entry_new(const char *name, int len,
+ u64 ino, unsigned int d_type)
+{
+ struct ovl_cache_entry *p;
+
+ p = kmalloc(sizeof(*p) + len + 1, GFP_KERNEL);
+ if (p) {
+ char *name_copy = (char *) (p + 1);
+ memcpy(name_copy, name, len);
+ name_copy[len] = '\0';
+ p->name = name_copy;
+ p->len = len;
+ p->type = d_type;
+ p->ino = ino;
+ p->is_whiteout = false;
+ }
+
+ return p;
+}
+
+static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
+ const char *name, int len, u64 ino,
+ unsigned int d_type)
+{
+ struct rb_node **newp = &rdd->root->rb_node;
+ struct rb_node *parent = NULL;
+ struct ovl_cache_entry *p;
+
+ while (*newp) {
+ int cmp;
+ struct ovl_cache_entry *tmp;
+
+ parent = *newp;
+ tmp = ovl_cache_entry_from_node(*newp);
+ cmp = strncmp(name, tmp->name, len);
+ if (cmp > 0)
+ newp = &tmp->node.rb_right;
+ else if (cmp < 0 || len < tmp->len)
+ newp = &tmp->node.rb_left;
+ else
+ return 0;
+ }
+
+ p = ovl_cache_entry_new(name, len, ino, d_type);
+ if (p == NULL)
+ return -ENOMEM;
+
+ list_add_tail(&p->l_node, rdd->list);
+ rb_link_node(&p->node, parent, newp);
+ rb_insert_color(&p->node, rdd->root);
+
+ return 0;
+}
+
+static int ovl_fill_lower(void *buf, const char *name, int namelen,
+ loff_t offset, u64 ino, unsigned int d_type)
+{
+ struct ovl_readdir_data *rdd = buf;
+ struct ovl_cache_entry *p;
+
+ rdd->count++;
+ p = ovl_cache_entry_find(rdd->root, name, namelen);
+ if (p) {
+ list_move_tail(&p->l_node, rdd->middle);
+ } else {
+ p = ovl_cache_entry_new(name, namelen, ino, d_type);
+ if (p == NULL)
+ rdd->err = -ENOMEM;
+ else
+ list_add_tail(&p->l_node, rdd->middle);
+ }
+
+ return rdd->err;
+}
+
+static void ovl_cache_free(struct list_head *list)
+{
+ struct ovl_cache_entry *p;
+ struct ovl_cache_entry *n;
+
+ list_for_each_entry_safe(p, n, list, l_node)
+ kfree(p);
+
+ INIT_LIST_HEAD(list);
+}
+
+static int ovl_fill_upper(void *buf, const char *name, int namelen,
+ loff_t offset, u64 ino, unsigned int d_type)
+{
+ struct ovl_readdir_data *rdd = buf;
+
+ rdd->count++;
+ return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
+}
+
+static int ovl_dir_read(struct path *realpath, struct ovl_readdir_data *rdd,
+ filldir_t filler)
+{
+ struct file *realfile;
+ int err;
+
+ realfile = vfs_open(realpath, O_RDONLY | O_DIRECTORY, current_cred());
+ if (IS_ERR(realfile))
+ return PTR_ERR(realfile);
+
+ do {
+ rdd->count = 0;
+ rdd->err = 0;
+ err = vfs_readdir(realfile, filler, rdd);
+ if (err >= 0)
+ err = rdd->err;
+ } while (!err && rdd->count);
+ fput(realfile);
+
+ return 0;
+}
+
+static void ovl_dir_reset(struct file *file)
+{
+ struct ovl_dir_file *od = file->private_data;
+ enum ovl_path_type type = ovl_path_type(file->f_path.dentry);
+
+ if (ovl_dentry_version_get(file->f_path.dentry) != od->cache_version) {
+ list_del_init(&od->cursor);
+ ovl_cache_free(&od->cache);
+ od->is_cached = false;
+ }
+ WARN_ON(!od->is_real && type != OVL_PATH_MERGE);
+ if (od->is_real && type == OVL_PATH_MERGE) {
+ fput(od->realfile);
+ od->realfile = NULL;
+ od->is_real = false;
+ }
+}
+
+static int ovl_dir_mark_whiteouts(struct ovl_readdir_data *rdd)
+{
+ struct ovl_cache_entry *p;
+ struct dentry *dentry;
+ const struct cred *old_cred;
+ struct cred *override_cred;
+
+ override_cred = prepare_creds();
+ if (!override_cred) {
+ ovl_cache_free(rdd->list);
+ return -ENOMEM;
+ }
+
+ /*
+ * CAP_SYS_ADMIN for getxattr
+ * CAP_DAC_OVERRIDE for lookup
+ */
+ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+ cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+ old_cred = override_creds(override_cred);
+
+ mutex_lock(&rdd->dir->d_inode->i_mutex);
+ list_for_each_entry(p, rdd->list, l_node) {
+ if (p->type != DT_LNK)
+ continue;
+
+ dentry = lookup_one_len(p->name, rdd->dir, p->len);
+ if (IS_ERR(dentry))
+ continue;
+
+ p->is_whiteout = ovl_is_whiteout(dentry);
+ dput(dentry);
+ }
+ mutex_unlock(&rdd->dir->d_inode->i_mutex);
+
+ revert_creds(old_cred);
+ put_cred(override_cred);
+
+ return 0;
+}
+
+static int ovl_dir_read_merged(struct path *upperpath, struct path *lowerpath,
+ struct ovl_readdir_data *rdd)
+{
+ int err;
+ struct rb_root root = RB_ROOT;
+ struct list_head middle;
+
+ rdd->root = &root;
+ if (upperpath->dentry) {
+ rdd->dir = upperpath->dentry;
+ err = ovl_dir_read(upperpath, rdd, ovl_fill_upper);
+ if (err)
+ goto out;
+
+ err = ovl_dir_mark_whiteouts(rdd);
+ if (err)
+ goto out;
+ }
+ /*
+ * Insert lowerpath entries before upperpath ones, this allows
+ * offsets to be reasonably constant
+ */
+ list_add(&middle, rdd->list);
+ rdd->middle = &middle;
+ err = ovl_dir_read(lowerpath, rdd, ovl_fill_lower);
+ list_del(&middle);
+out:
+ rdd->root = NULL;
+
+ return err;
+}
+
+static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos)
+{
+ struct list_head *l;
+ loff_t off;
+
+ l = od->cache.next;
+ for (off = 0; off < pos; off++) {
+ if (l == &od->cache)
+ break;
+ l = l->next;
+ }
+ list_move_tail(&od->cursor, l);
+}
+
+static int ovl_readdir(struct file *file, void *buf, filldir_t filler)
+{
+ struct ovl_dir_file *od = file->private_data;
+ int res;
+
+ if (!file->f_pos)
+ ovl_dir_reset(file);
+
+ if (od->is_real) {
+ res = vfs_readdir(od->realfile, filler, buf);
+ file->f_pos = od->realfile->f_pos;
+
+ return res;
+ }
+
+ if (!od->is_cached) {
+ struct path lowerpath;
+ struct path upperpath;
+ struct ovl_readdir_data rdd = { .list = &od->cache };
+
+ ovl_path_lower(file->f_path.dentry, &lowerpath);
+ ovl_path_upper(file->f_path.dentry, &upperpath);
+
+ res = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd);
+ if (res) {
+ ovl_cache_free(rdd.list);
+ return res;
+ }
+
+ od->cache_version = ovl_dentry_version_get(file->f_path.dentry);
+ od->is_cached = true;
+
+ ovl_seek_cursor(od, file->f_pos);
+ }
+
+ while (od->cursor.next != &od->cache) {
+ int over;
+ loff_t off;
+ struct ovl_cache_entry *p;
+
+ p = list_entry(od->cursor.next, struct ovl_cache_entry, l_node);
+ off = file->f_pos;
+ file->f_pos++;
+ list_move(&od->cursor, &p->l_node);
+
+ if (p->is_whiteout)
+ continue;
+
+ over = filler(buf, p->name, p->len, off, p->ino, p->type);
+ if (over)
+ break;
+ }
+
+ return 0;
+}
+
+static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin)
+{
+ loff_t res;
+ struct ovl_dir_file *od = file->private_data;
+
+ mutex_lock(&file->f_dentry->d_inode->i_mutex);
+ if (!file->f_pos)
+ ovl_dir_reset(file);
+
+ if (od->is_real) {
+ res = vfs_llseek(od->realfile, offset, origin);
+ file->f_pos = od->realfile->f_pos;
+ } else {
+ res = -EINVAL;
+
+ switch (origin) {
+ case SEEK_CUR:
+ offset += file->f_pos;
+ break;
+ case SEEK_SET:
+ break;
+ default:
+ goto out_unlock;
+ }
+ if (offset < 0)
+ goto out_unlock;
+
+ if (offset != file->f_pos) {
+ file->f_pos = offset;
+ if (od->is_cached)
+ ovl_seek_cursor(od, offset);
+ }
+ res = offset;
+ }
+out_unlock:
+ mutex_unlock(&file->f_dentry->d_inode->i_mutex);
+
+ return res;
+}
+
+static int ovl_dir_fsync(struct file *file, int datasync)
+{
+ struct ovl_dir_file *od = file->private_data;
+
+ /* May need to reopen directory if it got copied up */
+ if (!od->realfile) {
+ struct path upperpath;
+
+ ovl_path_upper(file->f_path.dentry, &upperpath);
+ od->realfile = vfs_open(&upperpath, O_RDONLY, current_cred());
+ if (IS_ERR(od->realfile))
+ return PTR_ERR(od->realfile);
+ }
+
+ return vfs_fsync(od->realfile, datasync);
+}
+
+static int ovl_dir_release(struct inode *inode, struct file *file)
+{
+ struct ovl_dir_file *od = file->private_data;
+
+ list_del(&od->cursor);
+ ovl_cache_free(&od->cache);
+ if (od->realfile)
+ fput(od->realfile);
+ kfree(od);
+
+ return 0;
+}
+
+static int ovl_dir_open(struct inode *inode, struct file *file)
+{
+ struct path realpath;
+ struct file *realfile;
+ struct ovl_dir_file *od;
+ enum ovl_path_type type;
+
+ od = kzalloc(sizeof(struct ovl_dir_file), GFP_KERNEL);
+ if (!od)
+ return -ENOMEM;
+
+ type = ovl_path_real(file->f_path.dentry, &realpath);
+ realfile = vfs_open(&realpath, file->f_flags, current_cred());
+ if (IS_ERR(realfile)) {
+ kfree(od);
+ return PTR_ERR(realfile);
+ }
+ INIT_LIST_HEAD(&od->cache);
+ INIT_LIST_HEAD(&od->cursor);
+ od->is_cached = false;
+ od->realfile = realfile;
+ od->is_real = (type != OVL_PATH_MERGE);
+ file->private_data = od;
+
+ return 0;
+}
+
+const struct file_operations ovl_dir_operations = {
+ .read = generic_read_dir,
+ .open = ovl_dir_open,
+ .readdir = ovl_readdir,
+ .llseek = ovl_dir_llseek,
+ .fsync = ovl_dir_fsync,
+ .release = ovl_dir_release,
+};
+
+static int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
+{
+ int err;
+ struct path lowerpath;
+ struct path upperpath;
+ struct ovl_cache_entry *p;
+ struct ovl_readdir_data rdd = { .list = list };
+
+ ovl_path_upper(dentry, &upperpath);
+ ovl_path_lower(dentry, &lowerpath);
+
+ err = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd);
+ if (err)
+ return err;
+
+ err = 0;
+
+ list_for_each_entry(p, list, l_node) {
+ if (p->is_whiteout)
+ continue;
+
+ if (p->name[0] == '.') {
+ if (p->len == 1)
+ continue;
+ if (p->len == 2 && p->name[1] == '.')
+ continue;
+ }
+ err = -ENOTEMPTY;
+ break;
+ }
+
+ return err;
+}
+
+static int ovl_remove_whiteouts(struct dentry *dir, struct list_head *list)
+{
+ struct path upperpath;
+ struct dentry *upperdir;
+ struct ovl_cache_entry *p;
+ const struct cred *old_cred;
+ struct cred *override_cred;
+ int err;
+
+ ovl_path_upper(dir, &upperpath);
+ upperdir = upperpath.dentry;
+
+ override_cred = prepare_creds();
+ if (!override_cred)
+ return -ENOMEM;
+
+ /*
+ * CAP_DAC_OVERRIDE for lookup and unlink
+ * CAP_SYS_ADMIN for setxattr of "trusted" namespace
+ * CAP_FOWNER for unlink in sticky directory
+ */
+ cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+ cap_raise(override_cred->cap_effective, CAP_FOWNER);
+ old_cred = override_creds(override_cred);
+
+ err = vfs_setxattr(upperdir, ovl_opaque_xattr, "y", 1, 0);
+ if (err)
+ goto out_revert_creds;
+
+ mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
+ list_for_each_entry(p, list, l_node) {
+ struct dentry *dentry;
+ int ret;
+
+ if (!p->is_whiteout)
+ continue;
+
+ dentry = lookup_one_len(p->name, upperdir, p->len);
+ if (IS_ERR(dentry)) {
+ printk(KERN_WARNING "overlayfs: failed to lookup whiteout %.*s: %li\n", p->len, p->name, PTR_ERR(dentry));
+ continue;
+ }
+ ret = vfs_unlink(upperdir->d_inode, dentry);
+ dput(dentry);
+ if (ret)
+ printk(KERN_WARNING "overlayfs: failed to unlink whiteout %.*s: %i\n", p->len, p->name, ret);
+ }
+ mutex_unlock(&upperdir->d_inode->i_mutex);
+
+out_revert_creds:
+ revert_creds(old_cred);
+ put_cred(override_cred);
+
+ return err;
+}
+
+int ovl_check_empty_and_clear(struct dentry *dentry, enum ovl_path_type type)
+{
+ int err;
+ LIST_HEAD(list);
+
+ err = ovl_check_empty_dir(dentry, &list);
+ if (!err && type == OVL_PATH_MERGE)
+ err = ovl_remove_whiteouts(dentry, &list);
+
+ ovl_cache_free(&list);
+
+ return err;
+}
--
1.7.1
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 5/6] overlayfs: add statfs support
2011-04-18 16:00 [PATCH 0/6] overlay filesystem Miklos Szeredi
` (3 preceding siblings ...)
2011-04-18 16:00 ` [PATCH 4/6] overlay filesystem Miklos Szeredi
@ 2011-04-18 16:00 ` Miklos Szeredi
2011-04-18 16:00 ` [PATCH 6/6] overlay: overlay filesystem documentation Miklos Szeredi
` (2 subsequent siblings)
7 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-04-18 16:00 UTC (permalink / raw)
To: viro
Cc: linux-fsdevel, linux-kernel, apw, nbd, neilb, hramrach, Miklos Szeredi
From: Andy Whitcroft <apw@canonical.com>
Add support for statfs to the overlayfs filesystem. As the upper layer
is the target of all write operations assume that the space in that
filesystem is the space in the overlayfs. There will be some inaccuracy as
overwriting a file will copy it up and consume space we were not expecting,
but it is better than nothing.
Use the upper layer dentry and mount from the overlayfs root inode,
passing the statfs call to that filesystem.
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/overlayfs/overlayfs.c | 20 ++++++++++++++++++++
1 files changed, 20 insertions(+), 0 deletions(-)
diff --git a/fs/overlayfs/overlayfs.c b/fs/overlayfs/overlayfs.c
index 0901eda..a9a09a6 100644
--- a/fs/overlayfs/overlayfs.c
+++ b/fs/overlayfs/overlayfs.c
@@ -379,9 +379,29 @@ static int ovl_remount_fs(struct super_block *sb, int *flagsp, char *data)
return mnt_want_write(ufs->upper_mnt);
}
+/**
+ * ovl_statfs
+ * @sb: The overlayfs super block
+ * @buf: The struct kstatfs to fill in with stats
+ *
+ * Get the filesystem statistics. As writes always target the upper layer
+ * filesystem pass the statfs to the same filesystem.
+ */
+static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+ struct dentry *root_dentry = dentry->d_sb->s_root;
+ struct path path;
+ ovl_path_upper(root_dentry, &path);
+
+ if (!path.dentry->d_sb->s_op->statfs)
+ return -ENOSYS;
+ return path.dentry->d_sb->s_op->statfs(path.dentry, buf);
+}
+
static const struct super_operations ovl_super_operations = {
.put_super = ovl_put_super,
.remount_fs = ovl_remount_fs,
+ .statfs = ovl_statfs,
};
struct ovl_config {
--
1.7.1
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 6/6] overlay: overlay filesystem documentation
2011-04-18 16:00 [PATCH 0/6] overlay filesystem Miklos Szeredi
` (4 preceding siblings ...)
2011-04-18 16:00 ` [PATCH 5/6] overlayfs: add statfs support Miklos Szeredi
@ 2011-04-18 16:00 ` Miklos Szeredi
2011-04-19 3:05 ` J. R. Okajima
2011-04-18 18:19 ` [PATCH 0/6] overlay filesystem Michal Suchanek
2011-05-09 19:14 ` [PATCH 0/6] overlay filesystem Michal Suchanek
7 siblings, 1 reply; 19+ messages in thread
From: Miklos Szeredi @ 2011-04-18 16:00 UTC (permalink / raw)
To: viro
Cc: linux-fsdevel, linux-kernel, apw, nbd, neilb, hramrach, Miklos Szeredi
From: Neil Brown <neilb@suse.de>
Document the overlay filesystem.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
Documentation/filesystems/overlayfs.txt | 167 +++++++++++++++++++++++++++++++
MAINTAINERS | 7 ++
2 files changed, 174 insertions(+), 0 deletions(-)
create mode 100644 Documentation/filesystems/overlayfs.txt
diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt
new file mode 100644
index 0000000..4bc0b34
--- /dev/null
+++ b/Documentation/filesystems/overlayfs.txt
@@ -0,0 +1,167 @@
+Written by: Neil Brown <neilb@suse.de>
+
+Overlay Filesystem
+==================
+
+This document describes a prototype for a new approach to providing
+overlay-filesystem functionality in Linux (sometimes referred to as
+union-filesystems). An overlay-filesystem tries to present a
+filesystem which is the result over overlaying one filesystem on top
+of the other.
+
+The result will inevitably fail to look exactly like a normal
+filesystem for various technical reasons. The expectation is that
+many use cases will be able to ignore these differences.
+
+This approach is 'hybrid' because the objects that appear in the
+filesystem do not all appear to belong to that filesystem. In many
+cases an object accessed in the union will be indistinguishable
+from accessing the corresponding object from the original filesystem.
+This is most obvious from the 'st_dev' field returned by stat(2).
+
+While directories will report an st_dev from the overlay-filesystem,
+all non-directory objects will report an st_dev from the lower or
+upper filesystem that is providing the object. Similarly st_ino will
+only be unique when combined with st_dev, and both of these can change
+over the lifetime of a non-directory object. Many applications and
+tools ignore these values and will not be affected.
+
+Upper and Lower
+---------------
+
+An overlay filesystem combines two filesystems - an 'upper' filesystem
+and a 'lower' filesystem. When a name exists in both filesystems, the
+object in the 'upper' filesystem is visible while the object in the
+'lower' filesystem is either hidden or, in the case of directories,
+merged with the 'upper' object.
+
+It would be more correct to refer to an upper and lower 'directory
+tree' rather than 'filesystem' as it is quite possible for both
+directory trees to be in the same filesystem and there is no
+requirement that the root of a filesystem be given for either upper or
+lower.
+
+The lower filesystem can be any filesystem supported by Linux and does
+not need to be writable. The lower filesystem can even be another
+overlayfs. The upper filesystem will normally be writable and if it
+is it must support the creation of trusted.* extended attributes, and
+must provide valid d_type in readdir responses, at least for symbolic
+links - so NFS is not suitable.
+
+A read-only overlay of two read-only filesystems may use any
+filesystem type.
+
+Directories
+-----------
+
+Overlaying mainly involved directories. If a given name appears in both
+upper and lower filesystems and refers to a non-directory in either,
+then the lower object is hidden - the name refers only to the upper
+object.
+
+Where both upper and lower objects are directories, a merged directory
+is formed.
+
+At mount time, the two directories given as mount options are combined
+into a merged directory:
+
+ mount -t overlayfs overlayfs -olowerdir=/lower,upperdir=/upper /overlay
+
+Then whenever a lookup is requested in such a merged directory, the
+lookup is performed in each actual directory and the combined result
+is cached in the dentry belonging to the overlay filesystem. If both
+actual lookups find directories, both are stored and a merged
+directory is created, otherwise only one is stored: the upper if it
+exists, else the lower.
+
+Only the lists of names from directories are merged. Other content
+such as metadata and extended attributes are reported for the upper
+directory only. These attributes of the lower directory are hidden.
+
+whiteouts and opaque directories
+--------------------------------
+
+In order to support rm and rmdir without changing the lower
+filesystem, an overlay filesystem needs to record in the upper filesystem
+that files have been removed. This is done using whiteouts and opaque
+directories (non-directories are always opaque).
+
+The overlay filesystem uses extended attributes with a
+"trusted.overlay." prefix to record these details.
+
+A whiteout is created as a symbolic link with target
+"(overlay-whiteout)" and with xattr "trusted.overlay.whiteout" set to "y".
+When a whiteout is found in the upper level of a merged directory, any
+matching name in the lower level is ignored, and the whiteout itself
+is also hidden.
+
+A directory is made opaque by setting the xattr "trusted.overlay.opaque"
+to "y". Where the upper filesystem contains an opaque directory, any
+directory in the lower filesystem with the same name is ignored.
+
+readdir
+-------
+
+When a 'readdir' request is made on a merged directory, the upper and
+lower directories are each read and the name lists merged in the
+obvious way (upper is read first, then lower - entries that already
+exist are not re-added). This merged name list is cached in the
+'struct file' and so remains as long as the file is kept open. If the
+directory is opened and read by two processes at the same time, they
+will each have separate caches. A seekdir to the start of the
+directory (offset 0) followed by a readdir will cause the cache to be
+discarded and rebuilt.
+
+This means that changes to the merged directory do not appear while a
+directory is being read. This is unlikely to be noticed by many
+programs.
+
+seek offsets are assigned sequentially when the directories are read.
+Thus if
+ - read part of a directory
+ - remember an offset, and close the directory
+ - re-open the directory some time later
+ - seek to the remembered offset
+
+there may be little correlation between the old and new locations in
+the list of filenames, particularly if anything has changed in the
+directory.
+
+Readdir on directories that are not merged is simply handled by the
+underlying directory (upper or lower).
+
+
+Non-directories
+---------------
+
+Objects that are not directories (files, symlinks, device-special
+files etc.) are presented either from the upper or lower filesystem as
+appropriate. When a file in the lower filesystem is accessed in a way
+the requires write-access, such as opening for write access, changing
+some metadata etc., the file is first copied from the lower filesystem
+to the upper filesystem (copy_up). Note that creating a hard-link
+also requires copy_up, though of course creation of a symlink does
+not.
+
+The copy_up process first makes sure that the containing directory
+exists in the upper filesystem - creating it and any parents as
+necessary. It then creates the object with the same metadata (owner,
+mode, mtime, symlink-target etc.) and then if the object is a file, the
+data is copied from the lower to the upper filesystem. Finally any
+extended attributes are copied up.
+
+Once the copy_up is complete, the overlay filesystem simply
+provides direct access to the newly created file in the upper
+filesystem - future operations on the file are barely noticed by the
+overlay filesystem (though an operation on the name of the file such as
+rename or unlink will of course be noticed and handled).
+
+Changes to underlying filesystems
+---------------------------------
+
+Offline changes, when the overlay is not mounted, are allowed to either
+the upper or the lower trees.
+
+Changes to the underlying filesystems while part of a mounted overlay
+filesystem are not allowed. This is not yet enforced, but will be in
+the future.
diff --git a/MAINTAINERS b/MAINTAINERS
index ec36003..dbbee18 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4680,6 +4680,13 @@ F: drivers/scsi/osd/
F: include/scsi/osd_*
F: fs/exofs/
+OVERLAYFS FILESYSTEM
+M: Miklos Szeredi <miklos@szeredi.hu>
+L: linux-fsdevel@vger.kernel.org
+S: Supported
+F: fs/overlayfs/*
+F: Documentation/filesystems/overlayfs.txt
+
P54 WIRELESS DRIVER
M: Christian Lamparter <chunkeey@googlemail.com>
L: linux-wireless@vger.kernel.org
--
1.7.1
^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [PATCH 0/6] overlay filesystem
2011-04-18 16:00 [PATCH 0/6] overlay filesystem Miklos Szeredi
` (5 preceding siblings ...)
2011-04-18 16:00 ` [PATCH 6/6] overlay: overlay filesystem documentation Miklos Szeredi
@ 2011-04-18 18:19 ` Michal Suchanek
2011-04-19 9:39 ` Miklos Szeredi
2011-05-09 19:14 ` [PATCH 0/6] overlay filesystem Michal Suchanek
7 siblings, 1 reply; 19+ messages in thread
From: Michal Suchanek @ 2011-04-18 18:19 UTC (permalink / raw)
To: Miklos Szeredi; +Cc: viro, linux-fsdevel, linux-kernel, apw, nbd, neilb
On 18 April 2011 18:00, Miklos Szeredi <miklos@szeredi.hu> wrote:
> Here's an updated version of the overlay filesystem.
>
> Git tree is here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs.v8
>
Can't build this one:
CC [M] fs/overlayfs/copy_up.o
CC [M] fs/qnx4/inode.o
fs/overlayfs/copy_up.c: In function 'ovl_read_symlink':
fs/overlayfs/copy_up.c:135: error: implicit declaration of function 'get_fs'
fs/overlayfs/copy_up.c:135: error: incompatible types when assigning
to type 'mm_segment_t' from type 'int'
fs/overlayfs/copy_up.c:136: error: implicit declaration of function 'set_fs'
fs/overlayfs/copy_up.c:136: error: implicit declaration of function 'get_ds'
CC [M] fs/quota/quota_v1.o
make[3]: *** [fs/overlayfs/copy_up.o] Error 1
make[2]: *** [fs/overlayfs] Error 2
make[2]: *** Waiting for unfinished jobs....
CC [M] fs/quota/quota_v2.o
CC [M] fs/quota/quota_tree.o
CC [M] fs/qnx4/dir.o
CC [M] fs/qnx4/namei.o
CC [M] fs/qnx4/bitmap.o
LD [M] fs/qnx4/qnx4.o
make[1]: *** [fs] Error 2
make[1]: *** Waiting for unfinished jobs....
Possibly a missing include somewhere?
Thanks
Michal
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 6/6] overlay: overlay filesystem documentation
2011-04-18 16:00 ` [PATCH 6/6] overlay: overlay filesystem documentation Miklos Szeredi
@ 2011-04-19 3:05 ` J. R. Okajima
2011-04-19 3:58 ` NeilBrown
0 siblings, 1 reply; 19+ messages in thread
From: J. R. Okajima @ 2011-04-19 3:05 UTC (permalink / raw)
To: Miklos Szeredi
Cc: viro, linux-fsdevel, linux-kernel, apw, nbd, neilb, hramrach,
Miklos Szeredi
Hello Miklos,
Miklos Szeredi:
> +The lower filesystem can be any filesystem supported by Linux and does
> +not need to be writable. The lower filesystem can even be another
> +overlayfs. ...
When user mounts overlayfs over and over like this,
# mount -t overlayfs -o upper=/rw1,lower=/ro1 none /ovl1
# mount -t overlayfs -o upper=/rw2,lower=/ovl1 none /ovl2
:::
# mount -t overlayfs -o upper=/rwN,lower=/ovl{N-1} none /ovlN
And if he modify a file in the bottom RO layer, then overlayfs copies-up
the file into each RW layer?
- 'fileA' exists in only /ro1.
- nested mounts.
- run "echo append >> /ovlN/fileA"
- is fileA copied-up to /rw1, and then to /rw2, and then ... to /rwN?
If user specify a single dir as every upper laery, then the copyup will
be done only once, or such RW layers are not allowed?
J. R. Okajima
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 6/6] overlay: overlay filesystem documentation
2011-04-19 3:05 ` J. R. Okajima
@ 2011-04-19 3:58 ` NeilBrown
2011-04-19 4:13 ` J. R. Okajima
0 siblings, 1 reply; 19+ messages in thread
From: NeilBrown @ 2011-04-19 3:58 UTC (permalink / raw)
To: J. R. Okajima
Cc: Miklos Szeredi, viro, linux-fsdevel, linux-kernel, apw, nbd,
hramrach, Miklos Szeredi
On Tue, 19 Apr 2011 12:05:17 +0900 "J. R. Okajima" <hooanon05@yahoo.co.jp>
wrote:
>
> Hello Miklos,
>
> Miklos Szeredi:
> > +The lower filesystem can be any filesystem supported by Linux and does
> > +not need to be writable. The lower filesystem can even be another
> > +overlayfs. ...
>
> When user mounts overlayfs over and over like this,
> # mount -t overlayfs -o upper=/rw1,lower=/ro1 none /ovl1
> # mount -t overlayfs -o upper=/rw2,lower=/ovl1 none /ovl2
> :::
> # mount -t overlayfs -o upper=/rwN,lower=/ovl{N-1} none /ovlN
>
> And if he modify a file in the bottom RO layer, then overlayfs copies-up
> the file into each RW layer?
> - 'fileA' exists in only /ro1.
> - nested mounts.
> - run "echo append >> /ovlN/fileA"
> - is fileA copied-up to /rw1, and then to /rw2, and then ... to /rwN?
>
> If user specify a single dir as every upper laery, then the copyup will
> be done only once, or such RW layers are not allowed?
>
>
> J. R. Okajima
Only to top level of an overlay stack is writable. All others are or should
be read only. So only the top level can change.
So in your example, fileA will be copied from ro1 directly into rwN where it
will then be appended to.
NeilBrown
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 6/6] overlay: overlay filesystem documentation
2011-04-19 3:58 ` NeilBrown
@ 2011-04-19 4:13 ` J. R. Okajima
0 siblings, 0 replies; 19+ messages in thread
From: J. R. Okajima @ 2011-04-19 4:13 UTC (permalink / raw)
To: NeilBrown
Cc: Miklos Szeredi, viro, linux-fsdevel, linux-kernel, apw, nbd,
hramrach, Miklos Szeredi
NeilBrown:
> Only to top level of an overlay stack is writable. All others are or should
> be read only. So only the top level can change.
>
> So in your example, fileA will be copied from ro1 directly into rwN where it
> will then be appended to.
I see.
When I have time, I will try building overlayfs.
Thank you.
J. R. Okajima
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 0/6] overlay filesystem
2011-04-18 18:19 ` [PATCH 0/6] overlay filesystem Michal Suchanek
@ 2011-04-19 9:39 ` Miklos Szeredi
0 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-04-19 9:39 UTC (permalink / raw)
To: Michal Suchanek; +Cc: viro, linux-fsdevel, linux-kernel, apw, nbd, neilb
On Mon, Apr 18, 2011 at 8:19 PM, Michal Suchanek <hramrach@centrum.cz> wrote:
> On 18 April 2011 18:00, Miklos Szeredi <miklos@szeredi.hu> wrote:
>> Here's an updated version of the overlay filesystem.
>>
>> Git tree is here:
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs.v8
>>
>
> Can't build this one:
>
>
> CC [M] fs/overlayfs/copy_up.o
> CC [M] fs/qnx4/inode.o
> fs/overlayfs/copy_up.c: In function 'ovl_read_symlink':
> fs/overlayfs/copy_up.c:135: error: implicit declaration of function 'get_fs'
> fs/overlayfs/copy_up.c:135: error: incompatible types when assigning
> to type 'mm_segment_t' from type 'int'
> fs/overlayfs/copy_up.c:136: error: implicit declaration of function 'set_fs'
> fs/overlayfs/copy_up.c:136: error: implicit declaration of function 'get_ds'
Thanks. Fixed in the overlayfs.v8 branch. Also patches coming up.
Miklos
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 0/6] overlay filesystem
@ 2011-04-19 9:39 ` Miklos Szeredi
0 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-04-19 9:39 UTC (permalink / raw)
To: Michal Suchanek; +Cc: viro, linux-fsdevel, linux-kernel, apw, nbd, neilb
On Mon, Apr 18, 2011 at 8:19 PM, Michal Suchanek <hramrach@centrum.cz> wrote:
> On 18 April 2011 18:00, Miklos Szeredi <miklos@szeredi.hu> wrote:
>> Here's an updated version of the overlay filesystem.
>>
>> Git tree is here:
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs.v8
>>
>
> Can't build this one:
>
>
> CC [M] fs/overlayfs/copy_up.o
> CC [M] fs/qnx4/inode.o
> fs/overlayfs/copy_up.c: In function 'ovl_read_symlink':
> fs/overlayfs/copy_up.c:135: error: implicit declaration of function 'get_fs'
> fs/overlayfs/copy_up.c:135: error: incompatible types when assigning
> to type 'mm_segment_t' from type 'int'
> fs/overlayfs/copy_up.c:136: error: implicit declaration of function 'set_fs'
> fs/overlayfs/copy_up.c:136: error: implicit declaration of function 'get_ds'
Thanks. Fixed in the overlayfs.v8 branch. Also patches coming up.
Miklos
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^ permalink raw reply [flat|nested] 19+ messages in thread
* [PATCH 1/2] ovl: fix missing include
2011-04-19 9:39 ` Miklos Szeredi
(?)
@ 2011-04-19 9:43 ` Miklos Szeredi
-1 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-04-19 9:43 UTC (permalink / raw)
To: viro
Cc: linux-fsdevel, linux-kernel, apw, nbd, neilb, hramrach, Miklos Szeredi
From: Miklos Szeredi <mszeredi@suse.cz>
CC [M] fs/overlayfs/copy_up.o
fs/overlayfs/copy_up.c: In function 'ovl_read_symlink':
fs/overlayfs/copy_up.c:135:2: error: implicit declaration of function 'get_fs'
fs/overlayfs/copy_up.c:135:9: error: incompatible types when assigning to type 'mm_segment_t' from type 'int'
fs/overlayfs/copy_up.c:136:2: error: implicit declaration of function 'set_fs'
fs/overlayfs/copy_up.c:136:2: error: implicit declaration of function 'get_ds'
Reported-by: Michal Suchanek <hramrach@centrum.cz>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/overlayfs/copy_up.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index fb9962c..308a80a 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -13,6 +13,7 @@
#include <linux/splice.h>
#include <linux/xattr.h>
#include <linux/security.h>
+#include <linux/uaccess.h>
#include "overlayfs.h"
#define OVL_COPY_UP_CHUNK_SIZE (1 << 20)
--
1.7.1
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 2/2] ovl: fix building as a module
2011-04-19 9:39 ` Miklos Szeredi
(?)
(?)
@ 2011-04-19 9:43 ` Miklos Szeredi
-1 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-04-19 9:43 UTC (permalink / raw)
To: viro
Cc: linux-fsdevel, linux-kernel, apw, nbd, neilb, hramrach, Miklos Szeredi
From: Miklos Szeredi <mszeredi@suse.cz>
Didn't test module building after splitting up the source. So it
broke. Now it's fixed.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/overlayfs/Makefile | 4 +-
fs/overlayfs/overlayfs.c | 596 ----------------------------------------------
fs/overlayfs/super.c | 596 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 599 insertions(+), 597 deletions(-)
delete mode 100644 fs/overlayfs/overlayfs.c
create mode 100644 fs/overlayfs/super.c
diff --git a/fs/overlayfs/Makefile b/fs/overlayfs/Makefile
index a7ebbf0..8f91889 100644
--- a/fs/overlayfs/Makefile
+++ b/fs/overlayfs/Makefile
@@ -2,4 +2,6 @@
# Makefile for the overlay filesystem.
#
-obj-$(CONFIG_OVERLAYFS_FS) += overlayfs.o inode.o dir.o readdir.o copy_up.o
+obj-$(CONFIG_OVERLAYFS_FS) += overlayfs.o
+
+overlayfs-objs := super.o inode.o dir.o readdir.o copy_up.o
diff --git a/fs/overlayfs/overlayfs.c b/fs/overlayfs/overlayfs.c
deleted file mode 100644
index a9a09a6..0000000
--- a/fs/overlayfs/overlayfs.c
+++ /dev/null
@@ -1,596 +0,0 @@
-/*
- *
- * Copyright (C) 2011 Novell Inc.
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 as published by
- * the Free Software Foundation.
- */
-
-#include <linux/fs.h>
-#include <linux/namei.h>
-#include <linux/xattr.h>
-#include <linux/security.h>
-#include <linux/mount.h>
-#include <linux/slab.h>
-#include <linux/parser.h>
-#include <linux/module.h>
-#include "overlayfs.h"
-
-MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
-MODULE_DESCRIPTION("Overlay filesystem");
-MODULE_LICENSE("GPL");
-
-struct ovl_fs {
- struct vfsmount *upper_mnt;
- struct vfsmount *lower_mnt;
-};
-
-struct ovl_entry {
- struct dentry *__upperdentry;
- struct dentry *lowerdentry;
- union {
- struct {
- u64 version;
- bool opaque;
- };
- struct rcu_head rcu;
- };
-};
-
-const char *ovl_whiteout_xattr = "trusted.overlay.whiteout";
-const char *ovl_opaque_xattr = "trusted.overlay.opaque";
-
-
-enum ovl_path_type ovl_path_type(struct dentry *dentry)
-{
- struct ovl_entry *oe = dentry->d_fsdata;
-
- if (oe->__upperdentry) {
- if (oe->lowerdentry && S_ISDIR(dentry->d_inode->i_mode))
- return OVL_PATH_MERGE;
- else
- return OVL_PATH_UPPER;
- } else {
- return OVL_PATH_LOWER;
- }
-}
-
-static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
-{
- struct dentry *upperdentry = ACCESS_ONCE(oe->__upperdentry);
- smp_read_barrier_depends();
- return upperdentry;
-}
-
-void ovl_path_upper(struct dentry *dentry, struct path *path)
-{
- struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
- struct ovl_entry *oe = dentry->d_fsdata;
-
- path->mnt = ofs->upper_mnt;
- path->dentry = ovl_upperdentry_dereference(oe);
-}
-
-void ovl_path_lower(struct dentry *dentry, struct path *path)
-{
- struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
- struct ovl_entry *oe = dentry->d_fsdata;
-
- path->mnt = ofs->lower_mnt;
- path->dentry = oe->lowerdentry;
-}
-
-enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
-{
-
- enum ovl_path_type type = ovl_path_type(dentry);
-
- if (type == OVL_PATH_LOWER)
- ovl_path_lower(dentry, path);
- else
- ovl_path_upper(dentry, path);
-
- return type;
-}
-
-struct dentry *ovl_dentry_upper(struct dentry *dentry)
-{
- struct ovl_entry *oe = dentry->d_fsdata;
-
- return ovl_upperdentry_dereference(oe);
-}
-
-struct dentry *ovl_dentry_lower(struct dentry *dentry)
-{
- struct ovl_entry *oe = dentry->d_fsdata;
-
- return oe->lowerdentry;
-}
-
-struct dentry *ovl_dentry_real(struct dentry *dentry)
-{
- struct ovl_entry *oe = dentry->d_fsdata;
- struct dentry *realdentry;
-
- realdentry = ovl_upperdentry_dereference(oe);
- if (!realdentry)
- realdentry = oe->lowerdentry;
-
- return realdentry;
-}
-
-struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
-{
- struct dentry *realdentry;
-
- realdentry = ovl_upperdentry_dereference(oe);
- if (realdentry) {
- *is_upper = true;
- } else {
- realdentry = oe->lowerdentry;
- *is_upper = false;
- }
- return realdentry;
-}
-
-bool ovl_dentry_is_opaque(struct dentry *dentry)
-{
- struct ovl_entry *oe = dentry->d_fsdata;
- return oe->opaque;
-}
-
-void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
-{
- struct ovl_entry *oe = dentry->d_fsdata;
- oe->opaque = opaque;
-}
-
-void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
-{
- struct ovl_entry *oe = dentry->d_fsdata;
-
- WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
- WARN_ON(oe->__upperdentry);
- smp_wmb();
- oe->__upperdentry = upperdentry;
-}
-
-void ovl_dentry_version_inc(struct dentry *dentry)
-{
- struct ovl_entry *oe = dentry->d_fsdata;
-
- WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
- oe->version++;
-}
-
-u64 ovl_dentry_version_get(struct dentry *dentry)
-{
- struct ovl_entry *oe = dentry->d_fsdata;
-
- WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
- return oe->version;
-}
-
-bool ovl_is_whiteout(struct dentry *dentry)
-{
- int res;
- char val;
-
- if (!dentry)
- return false;
- if (!dentry->d_inode)
- return false;
- if (!S_ISLNK(dentry->d_inode->i_mode))
- return false;
-
- res = vfs_getxattr(dentry, ovl_whiteout_xattr, &val, 1);
- if (res == 1 && val == 'y')
- return true;
-
- return false;
-}
-
-static bool ovl_is_opaquedir(struct dentry *dentry)
-{
- int res;
- char val;
-
- if (!S_ISDIR(dentry->d_inode->i_mode))
- return false;
-
- res = vfs_getxattr(dentry, ovl_opaque_xattr, &val, 1);
- if (res == 1 && val == 'y')
- return true;
-
- return false;
-}
-
-static void ovl_entry_free(struct rcu_head *head)
-{
- struct ovl_entry *oe = container_of(head, struct ovl_entry, rcu);
- kfree(oe);
-}
-
-static void ovl_dentry_release(struct dentry *dentry)
-{
- struct ovl_entry *oe = dentry->d_fsdata;
-
- if (oe) {
- dput(oe->__upperdentry);
- dput(oe->lowerdentry);
- call_rcu(&oe->rcu, ovl_entry_free);
- }
-}
-
-const struct dentry_operations ovl_dentry_operations = {
- .d_release = ovl_dentry_release,
-};
-
-static struct ovl_entry *ovl_alloc_entry(void)
-{
- return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL);
-}
-
-static struct dentry *ovl_lookup_real(struct dentry *dir, struct qstr *name)
-{
- struct dentry *dentry;
-
- mutex_lock(&dir->d_inode->i_mutex);
- dentry = lookup_one_len(name->name, dir, name->len);
- mutex_unlock(&dir->d_inode->i_mutex);
-
- if (IS_ERR(dentry)) {
- if (PTR_ERR(dentry) == -ENOENT)
- dentry = NULL;
- } else if (!dentry->d_inode) {
- dput(dentry);
- dentry = NULL;
- }
- return dentry;
-}
-
-int ovl_do_lookup(struct dentry *dentry)
-{
- struct ovl_entry *oe;
- struct dentry *upperdir;
- struct dentry *lowerdir;
- struct dentry *upperdentry = NULL;
- struct dentry *lowerdentry = NULL;
- struct inode *inode = NULL;
- int err;
-
- err = -ENOMEM;
- oe = ovl_alloc_entry();
- if (!oe)
- goto out;
-
- upperdir = ovl_dentry_upper(dentry->d_parent);
- lowerdir = ovl_dentry_lower(dentry->d_parent);
-
- if (upperdir) {
- upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
- err = PTR_ERR(upperdentry);
- if (IS_ERR(upperdentry))
- goto out_put_dir;
-
- if (lowerdir && upperdentry &&
- (S_ISLNK(upperdentry->d_inode->i_mode) ||
- S_ISDIR(upperdentry->d_inode->i_mode))) {
- const struct cred *old_cred;
- struct cred *override_cred;
-
- err = -ENOMEM;
- override_cred = prepare_creds();
- if (!override_cred)
- goto out_dput_upper;
-
- /* CAP_SYS_ADMIN needed for getxattr */
- cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
- old_cred = override_creds(override_cred);
-
- if (ovl_is_opaquedir(upperdentry)) {
- oe->opaque = true;
- } else if (ovl_is_whiteout(upperdentry)) {
- dput(upperdentry);
- upperdentry = NULL;
- oe->opaque = true;
- }
- revert_creds(old_cred);
- put_cred(override_cred);
- }
- }
- if (lowerdir && !oe->opaque) {
- lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name);
- err = PTR_ERR(lowerdentry);
- if (IS_ERR(lowerdentry))
- goto out_dput_upper;
- }
-
- if (lowerdentry && upperdentry &&
- (!S_ISDIR(upperdentry->d_inode->i_mode) ||
- !S_ISDIR(lowerdentry->d_inode->i_mode))) {
- dput(lowerdentry);
- lowerdentry = NULL;
- oe->opaque = true;
- }
-
- if (lowerdentry || upperdentry) {
- struct dentry *realdentry;
-
- realdentry = upperdentry ? upperdentry : lowerdentry;
- err = -ENOMEM;
- inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode, oe);
- if (!inode)
- goto out_dput;
- }
-
- if (upperdentry)
- oe->__upperdentry = upperdentry;
-
- if (lowerdentry)
- oe->lowerdentry = lowerdentry;
-
- dentry->d_fsdata = oe;
- dentry->d_op = &ovl_dentry_operations;
- d_add(dentry, inode);
-
- return 0;
-
-out_dput:
- dput(lowerdentry);
-out_dput_upper:
- dput(upperdentry);
-out_put_dir:
- kfree(oe);
-out:
- return err;
-}
-
-static void ovl_put_super(struct super_block *sb)
-{
- struct ovl_fs *ufs = sb->s_fs_info;
-
- if (!(sb->s_flags & MS_RDONLY))
- mnt_drop_write(ufs->upper_mnt);
-
- mntput(ufs->upper_mnt);
- mntput(ufs->lower_mnt);
-
- kfree(ufs);
-}
-
-static int ovl_remount_fs(struct super_block *sb, int *flagsp, char *data)
-{
- int flags = *flagsp;
- struct ovl_fs *ufs = sb->s_fs_info;
-
- /* When remounting rw or ro, we need to adjust the write access to the
- * upper fs.
- */
- if (((flags ^ sb->s_flags) & MS_RDONLY) == 0)
- /* No change to readonly status */
- return 0;
-
- if (flags & MS_RDONLY) {
- mnt_drop_write(ufs->upper_mnt);
- return 0;
- } else
- return mnt_want_write(ufs->upper_mnt);
-}
-
-/**
- * ovl_statfs
- * @sb: The overlayfs super block
- * @buf: The struct kstatfs to fill in with stats
- *
- * Get the filesystem statistics. As writes always target the upper layer
- * filesystem pass the statfs to the same filesystem.
- */
-static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
-{
- struct dentry *root_dentry = dentry->d_sb->s_root;
- struct path path;
- ovl_path_upper(root_dentry, &path);
-
- if (!path.dentry->d_sb->s_op->statfs)
- return -ENOSYS;
- return path.dentry->d_sb->s_op->statfs(path.dentry, buf);
-}
-
-static const struct super_operations ovl_super_operations = {
- .put_super = ovl_put_super,
- .remount_fs = ovl_remount_fs,
- .statfs = ovl_statfs,
-};
-
-struct ovl_config {
- char *lowerdir;
- char *upperdir;
-};
-
-enum {
- Opt_lowerdir,
- Opt_upperdir,
- Opt_err,
-};
-
-static const match_table_t ovl_tokens = {
- {Opt_lowerdir, "lowerdir=%s"},
- {Opt_upperdir, "upperdir=%s"},
- {Opt_err, NULL}
-};
-
-static int ovl_parse_opt(char *opt, struct ovl_config *config)
-{
- char *p;
-
- config->upperdir = NULL;
- config->lowerdir = NULL;
-
- while ((p = strsep(&opt, ",")) != NULL) {
- int token;
- substring_t args[MAX_OPT_ARGS];
-
- if (!*p)
- continue;
-
- token = match_token(p, ovl_tokens, args);
- switch (token) {
- case Opt_upperdir:
- kfree(config->upperdir);
- config->upperdir = match_strdup(&args[0]);
- if (!config->upperdir)
- return -ENOMEM;
- break;
-
- case Opt_lowerdir:
- kfree(config->lowerdir);
- config->lowerdir = match_strdup(&args[0]);
- if (!config->lowerdir)
- return -ENOMEM;
- break;
-
- default:
- return -EINVAL;
- }
- }
- return 0;
-}
-
-static int ovl_fill_super(struct super_block *sb, void *data, int silent)
-{
- struct path lowerpath;
- struct path upperpath;
- struct inode *root_inode;
- struct dentry *root_dentry;
- struct ovl_entry *oe;
- struct ovl_fs *ufs;
- struct ovl_config config;
- int err;
-
- err = ovl_parse_opt((char *) data, &config);
- if (err)
- goto out;
-
- err = -EINVAL;
- if (!config.upperdir || !config.lowerdir) {
- printk(KERN_ERR "overlayfs: missing upperdir or lowerdir\n");
- goto out_free_config;
- }
-
- err = -ENOMEM;
- ufs = kmalloc(sizeof(struct ovl_fs), GFP_KERNEL);
- if (!ufs)
- goto out_free_config;
-
- oe = ovl_alloc_entry();
- if (oe == NULL)
- goto out_free_ufs;
-
- root_inode = ovl_new_inode(sb, S_IFDIR, oe);
- if (!root_inode)
- goto out_free_oe;
-
- err = kern_path(config.upperdir, LOOKUP_FOLLOW, &upperpath);
- if (err)
- goto out_put_root;
-
- err = kern_path(config.lowerdir, LOOKUP_FOLLOW, &lowerpath);
- if (err)
- goto out_put_upperpath;
-
- err = -ENOTDIR;
- if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) ||
- !S_ISDIR(lowerpath.dentry->d_inode->i_mode))
- goto out_put_lowerpath;
-
- ufs->upper_mnt = clone_private_mount(&upperpath);
- err = PTR_ERR(ufs->upper_mnt);
- if (IS_ERR(ufs->upper_mnt)) {
- printk(KERN_ERR "overlayfs: failed to clone upperpath\n");
- goto out_put_lowerpath;
- }
-
- ufs->lower_mnt = clone_private_mount(&lowerpath);
- err = PTR_ERR(ufs->lower_mnt);
- if (IS_ERR(ufs->lower_mnt)) {
- printk(KERN_ERR "overlayfs: failed to clone lowerpath\n");
- goto out_put_upper_mnt;
- }
-
- if (!(sb->s_flags & MS_RDONLY)) {
- err = mnt_want_write(ufs->upper_mnt);
- if (err)
- goto out_put_lower_mnt;
- }
-
- err = -ENOMEM;
- root_dentry = d_alloc_root(root_inode);
- if (!root_dentry)
- goto out_drop_write;
-
- mntput(upperpath.mnt);
- mntput(lowerpath.mnt);
-
- oe->__upperdentry = upperpath.dentry;
- oe->lowerdentry = lowerpath.dentry;
-
- root_dentry->d_fsdata = oe;
- root_dentry->d_op = &ovl_dentry_operations;
-
- sb->s_op = &ovl_super_operations;
- sb->s_root = root_dentry;
- sb->s_fs_info = ufs;
-
- return 0;
-
-out_drop_write:
- if (!(sb->s_flags & MS_RDONLY))
- mnt_drop_write(ufs->upper_mnt);
-out_put_lower_mnt:
- mntput(ufs->lower_mnt);
-out_put_upper_mnt:
- mntput(ufs->upper_mnt);
-out_put_lowerpath:
- path_put(&lowerpath);
-out_put_upperpath:
- path_put(&upperpath);
-out_put_root:
- iput(root_inode);
-out_free_oe:
- kfree(oe);
-out_free_ufs:
- kfree(ufs);
-out_free_config:
- kfree(config.lowerdir);
- kfree(config.upperdir);
-out:
- return err;
-}
-
-static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
- const char *dev_name, void *raw_data)
-{
- return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
-}
-
-static struct file_system_type ovl_fs_type = {
- .owner = THIS_MODULE,
- .name = "overlayfs",
- .mount = ovl_mount,
- .kill_sb = kill_anon_super,
-};
-
-static int __init ovl_init(void)
-{
- return register_filesystem(&ovl_fs_type);
-}
-
-static void __exit ovl_exit(void)
-{
- unregister_filesystem(&ovl_fs_type);
-}
-
-module_init(ovl_init);
-module_exit(ovl_exit);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
new file mode 100644
index 0000000..a9a09a6
--- /dev/null
+++ b/fs/overlayfs/super.c
@@ -0,0 +1,596 @@
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/xattr.h>
+#include <linux/security.h>
+#include <linux/mount.h>
+#include <linux/slab.h>
+#include <linux/parser.h>
+#include <linux/module.h>
+#include "overlayfs.h"
+
+MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
+MODULE_DESCRIPTION("Overlay filesystem");
+MODULE_LICENSE("GPL");
+
+struct ovl_fs {
+ struct vfsmount *upper_mnt;
+ struct vfsmount *lower_mnt;
+};
+
+struct ovl_entry {
+ struct dentry *__upperdentry;
+ struct dentry *lowerdentry;
+ union {
+ struct {
+ u64 version;
+ bool opaque;
+ };
+ struct rcu_head rcu;
+ };
+};
+
+const char *ovl_whiteout_xattr = "trusted.overlay.whiteout";
+const char *ovl_opaque_xattr = "trusted.overlay.opaque";
+
+
+enum ovl_path_type ovl_path_type(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ if (oe->__upperdentry) {
+ if (oe->lowerdentry && S_ISDIR(dentry->d_inode->i_mode))
+ return OVL_PATH_MERGE;
+ else
+ return OVL_PATH_UPPER;
+ } else {
+ return OVL_PATH_LOWER;
+ }
+}
+
+static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
+{
+ struct dentry *upperdentry = ACCESS_ONCE(oe->__upperdentry);
+ smp_read_barrier_depends();
+ return upperdentry;
+}
+
+void ovl_path_upper(struct dentry *dentry, struct path *path)
+{
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ path->mnt = ofs->upper_mnt;
+ path->dentry = ovl_upperdentry_dereference(oe);
+}
+
+void ovl_path_lower(struct dentry *dentry, struct path *path)
+{
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ path->mnt = ofs->lower_mnt;
+ path->dentry = oe->lowerdentry;
+}
+
+enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
+{
+
+ enum ovl_path_type type = ovl_path_type(dentry);
+
+ if (type == OVL_PATH_LOWER)
+ ovl_path_lower(dentry, path);
+ else
+ ovl_path_upper(dentry, path);
+
+ return type;
+}
+
+struct dentry *ovl_dentry_upper(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ return ovl_upperdentry_dereference(oe);
+}
+
+struct dentry *ovl_dentry_lower(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ return oe->lowerdentry;
+}
+
+struct dentry *ovl_dentry_real(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+ struct dentry *realdentry;
+
+ realdentry = ovl_upperdentry_dereference(oe);
+ if (!realdentry)
+ realdentry = oe->lowerdentry;
+
+ return realdentry;
+}
+
+struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
+{
+ struct dentry *realdentry;
+
+ realdentry = ovl_upperdentry_dereference(oe);
+ if (realdentry) {
+ *is_upper = true;
+ } else {
+ realdentry = oe->lowerdentry;
+ *is_upper = false;
+ }
+ return realdentry;
+}
+
+bool ovl_dentry_is_opaque(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+ return oe->opaque;
+}
+
+void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+ oe->opaque = opaque;
+}
+
+void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
+ WARN_ON(oe->__upperdentry);
+ smp_wmb();
+ oe->__upperdentry = upperdentry;
+}
+
+void ovl_dentry_version_inc(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
+ oe->version++;
+}
+
+u64 ovl_dentry_version_get(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
+ return oe->version;
+}
+
+bool ovl_is_whiteout(struct dentry *dentry)
+{
+ int res;
+ char val;
+
+ if (!dentry)
+ return false;
+ if (!dentry->d_inode)
+ return false;
+ if (!S_ISLNK(dentry->d_inode->i_mode))
+ return false;
+
+ res = vfs_getxattr(dentry, ovl_whiteout_xattr, &val, 1);
+ if (res == 1 && val == 'y')
+ return true;
+
+ return false;
+}
+
+static bool ovl_is_opaquedir(struct dentry *dentry)
+{
+ int res;
+ char val;
+
+ if (!S_ISDIR(dentry->d_inode->i_mode))
+ return false;
+
+ res = vfs_getxattr(dentry, ovl_opaque_xattr, &val, 1);
+ if (res == 1 && val == 'y')
+ return true;
+
+ return false;
+}
+
+static void ovl_entry_free(struct rcu_head *head)
+{
+ struct ovl_entry *oe = container_of(head, struct ovl_entry, rcu);
+ kfree(oe);
+}
+
+static void ovl_dentry_release(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ if (oe) {
+ dput(oe->__upperdentry);
+ dput(oe->lowerdentry);
+ call_rcu(&oe->rcu, ovl_entry_free);
+ }
+}
+
+const struct dentry_operations ovl_dentry_operations = {
+ .d_release = ovl_dentry_release,
+};
+
+static struct ovl_entry *ovl_alloc_entry(void)
+{
+ return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL);
+}
+
+static struct dentry *ovl_lookup_real(struct dentry *dir, struct qstr *name)
+{
+ struct dentry *dentry;
+
+ mutex_lock(&dir->d_inode->i_mutex);
+ dentry = lookup_one_len(name->name, dir, name->len);
+ mutex_unlock(&dir->d_inode->i_mutex);
+
+ if (IS_ERR(dentry)) {
+ if (PTR_ERR(dentry) == -ENOENT)
+ dentry = NULL;
+ } else if (!dentry->d_inode) {
+ dput(dentry);
+ dentry = NULL;
+ }
+ return dentry;
+}
+
+int ovl_do_lookup(struct dentry *dentry)
+{
+ struct ovl_entry *oe;
+ struct dentry *upperdir;
+ struct dentry *lowerdir;
+ struct dentry *upperdentry = NULL;
+ struct dentry *lowerdentry = NULL;
+ struct inode *inode = NULL;
+ int err;
+
+ err = -ENOMEM;
+ oe = ovl_alloc_entry();
+ if (!oe)
+ goto out;
+
+ upperdir = ovl_dentry_upper(dentry->d_parent);
+ lowerdir = ovl_dentry_lower(dentry->d_parent);
+
+ if (upperdir) {
+ upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
+ err = PTR_ERR(upperdentry);
+ if (IS_ERR(upperdentry))
+ goto out_put_dir;
+
+ if (lowerdir && upperdentry &&
+ (S_ISLNK(upperdentry->d_inode->i_mode) ||
+ S_ISDIR(upperdentry->d_inode->i_mode))) {
+ const struct cred *old_cred;
+ struct cred *override_cred;
+
+ err = -ENOMEM;
+ override_cred = prepare_creds();
+ if (!override_cred)
+ goto out_dput_upper;
+
+ /* CAP_SYS_ADMIN needed for getxattr */
+ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+ old_cred = override_creds(override_cred);
+
+ if (ovl_is_opaquedir(upperdentry)) {
+ oe->opaque = true;
+ } else if (ovl_is_whiteout(upperdentry)) {
+ dput(upperdentry);
+ upperdentry = NULL;
+ oe->opaque = true;
+ }
+ revert_creds(old_cred);
+ put_cred(override_cred);
+ }
+ }
+ if (lowerdir && !oe->opaque) {
+ lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name);
+ err = PTR_ERR(lowerdentry);
+ if (IS_ERR(lowerdentry))
+ goto out_dput_upper;
+ }
+
+ if (lowerdentry && upperdentry &&
+ (!S_ISDIR(upperdentry->d_inode->i_mode) ||
+ !S_ISDIR(lowerdentry->d_inode->i_mode))) {
+ dput(lowerdentry);
+ lowerdentry = NULL;
+ oe->opaque = true;
+ }
+
+ if (lowerdentry || upperdentry) {
+ struct dentry *realdentry;
+
+ realdentry = upperdentry ? upperdentry : lowerdentry;
+ err = -ENOMEM;
+ inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode, oe);
+ if (!inode)
+ goto out_dput;
+ }
+
+ if (upperdentry)
+ oe->__upperdentry = upperdentry;
+
+ if (lowerdentry)
+ oe->lowerdentry = lowerdentry;
+
+ dentry->d_fsdata = oe;
+ dentry->d_op = &ovl_dentry_operations;
+ d_add(dentry, inode);
+
+ return 0;
+
+out_dput:
+ dput(lowerdentry);
+out_dput_upper:
+ dput(upperdentry);
+out_put_dir:
+ kfree(oe);
+out:
+ return err;
+}
+
+static void ovl_put_super(struct super_block *sb)
+{
+ struct ovl_fs *ufs = sb->s_fs_info;
+
+ if (!(sb->s_flags & MS_RDONLY))
+ mnt_drop_write(ufs->upper_mnt);
+
+ mntput(ufs->upper_mnt);
+ mntput(ufs->lower_mnt);
+
+ kfree(ufs);
+}
+
+static int ovl_remount_fs(struct super_block *sb, int *flagsp, char *data)
+{
+ int flags = *flagsp;
+ struct ovl_fs *ufs = sb->s_fs_info;
+
+ /* When remounting rw or ro, we need to adjust the write access to the
+ * upper fs.
+ */
+ if (((flags ^ sb->s_flags) & MS_RDONLY) == 0)
+ /* No change to readonly status */
+ return 0;
+
+ if (flags & MS_RDONLY) {
+ mnt_drop_write(ufs->upper_mnt);
+ return 0;
+ } else
+ return mnt_want_write(ufs->upper_mnt);
+}
+
+/**
+ * ovl_statfs
+ * @sb: The overlayfs super block
+ * @buf: The struct kstatfs to fill in with stats
+ *
+ * Get the filesystem statistics. As writes always target the upper layer
+ * filesystem pass the statfs to the same filesystem.
+ */
+static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+ struct dentry *root_dentry = dentry->d_sb->s_root;
+ struct path path;
+ ovl_path_upper(root_dentry, &path);
+
+ if (!path.dentry->d_sb->s_op->statfs)
+ return -ENOSYS;
+ return path.dentry->d_sb->s_op->statfs(path.dentry, buf);
+}
+
+static const struct super_operations ovl_super_operations = {
+ .put_super = ovl_put_super,
+ .remount_fs = ovl_remount_fs,
+ .statfs = ovl_statfs,
+};
+
+struct ovl_config {
+ char *lowerdir;
+ char *upperdir;
+};
+
+enum {
+ Opt_lowerdir,
+ Opt_upperdir,
+ Opt_err,
+};
+
+static const match_table_t ovl_tokens = {
+ {Opt_lowerdir, "lowerdir=%s"},
+ {Opt_upperdir, "upperdir=%s"},
+ {Opt_err, NULL}
+};
+
+static int ovl_parse_opt(char *opt, struct ovl_config *config)
+{
+ char *p;
+
+ config->upperdir = NULL;
+ config->lowerdir = NULL;
+
+ while ((p = strsep(&opt, ",")) != NULL) {
+ int token;
+ substring_t args[MAX_OPT_ARGS];
+
+ if (!*p)
+ continue;
+
+ token = match_token(p, ovl_tokens, args);
+ switch (token) {
+ case Opt_upperdir:
+ kfree(config->upperdir);
+ config->upperdir = match_strdup(&args[0]);
+ if (!config->upperdir)
+ return -ENOMEM;
+ break;
+
+ case Opt_lowerdir:
+ kfree(config->lowerdir);
+ config->lowerdir = match_strdup(&args[0]);
+ if (!config->lowerdir)
+ return -ENOMEM;
+ break;
+
+ default:
+ return -EINVAL;
+ }
+ }
+ return 0;
+}
+
+static int ovl_fill_super(struct super_block *sb, void *data, int silent)
+{
+ struct path lowerpath;
+ struct path upperpath;
+ struct inode *root_inode;
+ struct dentry *root_dentry;
+ struct ovl_entry *oe;
+ struct ovl_fs *ufs;
+ struct ovl_config config;
+ int err;
+
+ err = ovl_parse_opt((char *) data, &config);
+ if (err)
+ goto out;
+
+ err = -EINVAL;
+ if (!config.upperdir || !config.lowerdir) {
+ printk(KERN_ERR "overlayfs: missing upperdir or lowerdir\n");
+ goto out_free_config;
+ }
+
+ err = -ENOMEM;
+ ufs = kmalloc(sizeof(struct ovl_fs), GFP_KERNEL);
+ if (!ufs)
+ goto out_free_config;
+
+ oe = ovl_alloc_entry();
+ if (oe == NULL)
+ goto out_free_ufs;
+
+ root_inode = ovl_new_inode(sb, S_IFDIR, oe);
+ if (!root_inode)
+ goto out_free_oe;
+
+ err = kern_path(config.upperdir, LOOKUP_FOLLOW, &upperpath);
+ if (err)
+ goto out_put_root;
+
+ err = kern_path(config.lowerdir, LOOKUP_FOLLOW, &lowerpath);
+ if (err)
+ goto out_put_upperpath;
+
+ err = -ENOTDIR;
+ if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) ||
+ !S_ISDIR(lowerpath.dentry->d_inode->i_mode))
+ goto out_put_lowerpath;
+
+ ufs->upper_mnt = clone_private_mount(&upperpath);
+ err = PTR_ERR(ufs->upper_mnt);
+ if (IS_ERR(ufs->upper_mnt)) {
+ printk(KERN_ERR "overlayfs: failed to clone upperpath\n");
+ goto out_put_lowerpath;
+ }
+
+ ufs->lower_mnt = clone_private_mount(&lowerpath);
+ err = PTR_ERR(ufs->lower_mnt);
+ if (IS_ERR(ufs->lower_mnt)) {
+ printk(KERN_ERR "overlayfs: failed to clone lowerpath\n");
+ goto out_put_upper_mnt;
+ }
+
+ if (!(sb->s_flags & MS_RDONLY)) {
+ err = mnt_want_write(ufs->upper_mnt);
+ if (err)
+ goto out_put_lower_mnt;
+ }
+
+ err = -ENOMEM;
+ root_dentry = d_alloc_root(root_inode);
+ if (!root_dentry)
+ goto out_drop_write;
+
+ mntput(upperpath.mnt);
+ mntput(lowerpath.mnt);
+
+ oe->__upperdentry = upperpath.dentry;
+ oe->lowerdentry = lowerpath.dentry;
+
+ root_dentry->d_fsdata = oe;
+ root_dentry->d_op = &ovl_dentry_operations;
+
+ sb->s_op = &ovl_super_operations;
+ sb->s_root = root_dentry;
+ sb->s_fs_info = ufs;
+
+ return 0;
+
+out_drop_write:
+ if (!(sb->s_flags & MS_RDONLY))
+ mnt_drop_write(ufs->upper_mnt);
+out_put_lower_mnt:
+ mntput(ufs->lower_mnt);
+out_put_upper_mnt:
+ mntput(ufs->upper_mnt);
+out_put_lowerpath:
+ path_put(&lowerpath);
+out_put_upperpath:
+ path_put(&upperpath);
+out_put_root:
+ iput(root_inode);
+out_free_oe:
+ kfree(oe);
+out_free_ufs:
+ kfree(ufs);
+out_free_config:
+ kfree(config.lowerdir);
+ kfree(config.upperdir);
+out:
+ return err;
+}
+
+static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
+ const char *dev_name, void *raw_data)
+{
+ return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
+}
+
+static struct file_system_type ovl_fs_type = {
+ .owner = THIS_MODULE,
+ .name = "overlayfs",
+ .mount = ovl_mount,
+ .kill_sb = kill_anon_super,
+};
+
+static int __init ovl_init(void)
+{
+ return register_filesystem(&ovl_fs_type);
+}
+
+static void __exit ovl_exit(void)
+{
+ unregister_filesystem(&ovl_fs_type);
+}
+
+module_init(ovl_init);
+module_exit(ovl_exit);
--
1.7.1
^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [PATCH 0/6] overlay filesystem
2011-04-18 16:00 [PATCH 0/6] overlay filesystem Miklos Szeredi
` (6 preceding siblings ...)
2011-04-18 18:19 ` [PATCH 0/6] overlay filesystem Michal Suchanek
@ 2011-05-09 19:14 ` Michal Suchanek
2011-05-10 16:30 ` Miklos Szeredi
7 siblings, 1 reply; 19+ messages in thread
From: Michal Suchanek @ 2011-05-09 19:14 UTC (permalink / raw)
To: Miklos Szeredi; +Cc: viro, linux-fsdevel, linux-kernel, apw, nbd, neilb
Hello
On 18 April 2011 18:00, Miklos Szeredi <miklos@szeredi.hu> wrote:
> Here's an updated version of the overlay filesystem.
>
> Git tree is here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs.v8
>
> Changes from v7 to v8:
>
> - split overlayfs.c into smaller files
>
> - fix locking for copy up (reported by Al Viro)
>
> - locking analysis of copy up vs. directory rename added as a comment
>
> - tested with lockdep, fixed one lock annotation
>
> - other bug fixes
>
> To be done:
>
> - redo i_op->open, waiting for status of atomic_open() from Al
>
> - look into xattr support for tmpfs
>
What's still required for overlayfs to get into the kernel?
With the additional patches posted in the v8 branch (the modular build
fix and the xattr for tmpfs patch) overlayfs works for me.
I rebuilt my linux rescue system to use
overlayfs/tmpfs+squashfs/loop/fuse.httpfs and used it a few times
without any issues.
This system has about 1.6G data in 68599 files, 6960 directories and
7634 symlinks (compressed to about 630M squashfs).
Thanks
Michal
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 0/6] overlay filesystem
2011-05-09 19:14 ` [PATCH 0/6] overlay filesystem Michal Suchanek
@ 2011-05-10 16:30 ` Miklos Szeredi
0 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-05-10 16:30 UTC (permalink / raw)
To: Michal Suchanek; +Cc: viro, linux-fsdevel, linux-kernel, apw, nbd, neilb
Michal Suchanek <hramrach@centrum.cz> writes:
> Hello
>
> On 18 April 2011 18:00, Miklos Szeredi <miklos@szeredi.hu> wrote:
>> Here's an updated version of the overlay filesystem.
>>
>> Git tree is here:
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs.v8
>>
>> Changes from v7 to v8:
>>
>> - split overlayfs.c into smaller files
>>
>> - fix locking for copy up (reported by Al Viro)
>>
>> - locking analysis of copy up vs. directory rename added as a comment
>>
>> - tested with lockdep, fixed one lock annotation
>>
>> - other bug fixes
>>
>> To be done:
>>
>> - redo i_op->open, waiting for status of atomic_open() from Al
>>
>> - look into xattr support for tmpfs
>>
>
> What's still required for overlayfs to get into the kernel?
>
> With the additional patches posted in the v8 branch (the modular build
> fix and the xattr for tmpfs patch) overlayfs works for me.
>
> I rebuilt my linux rescue system to use
> overlayfs/tmpfs+squashfs/loop/fuse.httpfs and used it a few times
> without any issues.
>
> This system has about 1.6G data in 68599 files, 6960 directories and
> 7634 symlinks (compressed to about 630M squashfs).
Great, thanks for reporting on your test results.
Before posting v9 I'd like to clear up the bug observed by Jordi. Then
it will need to be acked by Al Viro before going into mainline.
Thanks,
Miklos
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 0/6] overlay filesystem
@ 2011-05-10 16:30 ` Miklos Szeredi
0 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2011-05-10 16:30 UTC (permalink / raw)
To: Michal Suchanek; +Cc: viro, linux-fsdevel, linux-kernel, apw, nbd, neilb
Michal Suchanek <hramrach@centrum.cz> writes:
> Hello
>
> On 18 April 2011 18:00, Miklos Szeredi <miklos@szeredi.hu> wrote:
>> Here's an updated version of the overlay filesystem.
>>
>> Git tree is here:
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs.v8
>>
>> Changes from v7 to v8:
>>
>> - split overlayfs.c into smaller files
>>
>> - fix locking for copy up (reported by Al Viro)
>>
>> - locking analysis of copy up vs. directory rename added as a comment
>>
>> - tested with lockdep, fixed one lock annotation
>>
>> - other bug fixes
>>
>> To be done:
>>
>> - redo i_op->open, waiting for status of atomic_open() from Al
>>
>> - look into xattr support for tmpfs
>>
>
> What's still required for overlayfs to get into the kernel?
>
> With the additional patches posted in the v8 branch (the modular build
> fix and the xattr for tmpfs patch) overlayfs works for me.
>
> I rebuilt my linux rescue system to use
> overlayfs/tmpfs+squashfs/loop/fuse.httpfs and used it a few times
> without any issues.
>
> This system has about 1.6G data in 68599 files, 6960 directories and
> 7634 symlinks (compressed to about 630M squashfs).
Great, thanks for reporting on your test results.
Before posting v9 I'd like to clear up the bug observed by Jordi. Then
it will need to be acked by Al Viro before going into mainline.
Thanks,
Miklos
--
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^ permalink raw reply [flat|nested] 19+ messages in thread
* [PATCH 6/6] overlay: overlay filesystem documentation
2010-09-03 13:41 [PATCH 0/6] overlay filesystem prototype Miklos Szeredi
@ 2010-09-03 13:41 ` Miklos Szeredi
0 siblings, 0 replies; 19+ messages in thread
From: Miklos Szeredi @ 2010-09-03 13:41 UTC (permalink / raw)
To: linux-fsdevel, linux-kernel; +Cc: vaurora, neilb, viro
[-- Attachment #1: overlayfs-documentation.patch --]
[-- Type: text/plain, Size: 7769 bytes --]
From: Neil Brown <neilb@suse.de>
Document the overlay filesystem.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
Documentation/filesystems/overlayfs.txt | 162 ++++++++++++++++++++++++++++++++
1 file changed, 162 insertions(+)
Index: linux-2.6/Documentation/filesystems/overlayfs.txt
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6/Documentation/filesystems/overlayfs.txt 2010-08-31 18:41:33.000000000 +0200
@@ -0,0 +1,162 @@
+Written by: Neil Brown <neilb@suse.de>
+
+Overlay Filesystem
+==================
+
+This document describes a prototype for a new approach to providing
+union-filesystem functionality in Linux. A union-filesystem tries to
+present the union of two different filesystems as though it were a
+single filesystem. The result will inevitably fail to look exactly
+like a normal filesystem for various technical reasons. The
+expectation is that many use cases will be able to ignore these
+differences.
+
+This approach is 'hybrid' because the objects that appear in the
+filesystem do not all appear to belong to that filesystem. In many
+case an object accessed in the union will be indistinguishable
+from accessing the corresponding object from the original filesystem.
+This is most obvious from the 'st_dev' field returned by stat(2).
+Some objects will report an st_dev from one original filesystem, some
+from the other, directories will report an st_dev from the union
+itself. Similarly st_ino will only be unique when combined with
+st_dev, and both of these can change over the lifetime of a
+non-directory object. Many applications and tools ignore these values
+and will not be affected.
+
+Upper and Lower
+---------------
+
+An overlay filesystem combines two filesystems - an 'upper' filesystem
+and a 'lower' filesystem. Note that while in set theory, 'union' is a
+commutative operation, in filesystems it is not - the two filesystems
+are treated differently. When a name exists in both filesystems, the
+object in the 'upper' filesystem is visible while the object in the
+'lower' filesystem is either hidden or, in the case of directories,
+merged with the 'upper' object.
+
+It would be more correct to refer to an upper and lower 'directory
+tree' rather than 'filesystem' as it is quite possible for both
+directory trees to be in the same filesystem and there is no
+requirement that the root of a filesystem be given for either upper or
+lower.
+
+The lower filesystem can be any filesystem supported by Linux and does
+not need to be writable. Theoretically it could even be another
+overlayfs, but this is not yet supported. The upper filesystem will
+normally be writeable and if it is it must support the creation of
+trusted.* extended attributes, and must provide valid d_type in
+readdir responses, at least for symbolic links - so NFS is not
+suitable.
+
+A read-only union of two read-only filesystems may use any filesystem
+type.
+
+Directories
+-----------
+
+Unioning mainly involved directories. If a given name appears in both
+upper ad lower filesystems and refers to a non-directory in either,
+then the lower object is hidden - the name refers only to the upper
+object.
+
+Where both upper and lower objects are directories, a merged directory
+is formed.
+
+At mount time, the two directories given as mount options are combined
+into a merged directory. Then whenever a lookup is requested in such
+a merged directory, the lookup is performed in each actual directory
+and the combined result is cached in the dentry belonging to the overlay
+filesystem. If both actual lookups find directories, both are stored
+and a merged directory is create, otherwise only one is stored: the
+upper if it exists, else the lower.
+
+Only the lists of names from directories are merged. Other content
+such as metadata and extended attributes are reported for the upper
+directory only. These attributes of the lower directory are hidden.
+
+whiteouts and opaque directories
+--------------------------------
+
+In order to support rm and rmdir without changing the lower
+filesystem, an overlay filesystem needs to record in the upper filesystem
+that files have been removed. This is done using whiteouts and opaque
+directories (non-directories are always opaque).
+
+The overlay filesystem uses extended attributes with a
+"trusted.overlay." prefix to record these details.
+
+A whiteout is created as a symbolic link with target
+"(overlay-whiteout)" and with xattr "trusted.overlay.whiteout" set to "y".
+When a whiteout is found in the upper level of a merged directory, any
+matching name in the lower level is ignored, and the whiteout itself
+is also hidden.
+
+A directory is made opaque by setting the xattr "trusted.overlay.opaque"
+to "y". Where the upper filesystem contains an opaque directory, any
+directory in the lower filesystem with the same name is ignored.
+
+readdir
+-------
+
+When a 'readdir' request is made on a merged directory, the upper and
+lower directories are each read and the name lists merged in the
+obvious way (upper is read first, then lower - entries that already
+exist are not re-added). This merged name list is cached in the
+'struct file' and so remains as long as the file is kept open. If the
+directory is opened and read by two processes at the same time, they
+will each have separate caches. A seekdir to the start of the
+directory (offset 0) followed by a readdir will cause the cache to be
+discarded and rebuilt.
+
+This means that changes to the merged directory do not appear while a
+directory is being read. This is unlikely to be noticed by many
+programs.
+
+seek offsets are assigned sequentially when the directories are read.
+Thus if
+ - read part of a directory
+ - remember an offset, and close the directory
+ - re-open the directory some time later
+ - seek to the remembered offset
+
+there may be little correlation between the old and new locations in
+the list of filenames, particularly if anything has changed in the
+directory.
+
+Readdir on directories that are not merged is simply handled by the
+underlying directory (upper or lower).
+
+
+Non-directories
+---------------
+
+Objects that are not directories (files, symlinks, device-special
+files etc) are presented either from the upper or lower filesystem as
+appropriate. When a file in the lower filesystem is accessed in a way
+the requires write-access; such as opening for write access, changing
+some metadata etc, the file is first copied from the lower filesystem
+to the upper filesystem (copy_up). Note that creating a hard-link
+also requires copy-up, though of course creation of a symlink does
+not.
+
+The copy_up process first makes sure that the containing directory
+exists in the upper filesystem - creating it and any parents as
+necessary. It then creates the object with the same metadata (owner,
+mode, mtime, symlink-target etc) and then if the object is a file, the
+data is copied from the lower to the upper filesystem. Finally any
+extended attributes are copied up.
+
+Once the copy_up is complete, the overlay filesystem simply
+provides direct access to the newly created file in the upper
+filesystem - future operations on the file are barely noticed by the
+overlay filesystem (though an operation on the name of the file such as
+rename or unlink will of course be noticed and handled).
+
+Changes to underlying filesystems
+---------------------------------
+
+Offline changes, when the overlay is not mounted, are allowed to either
+the upper or the lower trees.
+
+Changes to the underlying filesystems while part of a mounted overlay
+filesystem are not allowed. This is not yet enforced, but will be in
--
^ permalink raw reply [flat|nested] 19+ messages in thread
end of thread, other threads:[~2011-05-10 16:30 UTC | newest]
Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2011-04-18 16:00 [PATCH 0/6] overlay filesystem Miklos Szeredi
2011-04-18 16:00 ` [PATCH 1/6] vfs: add i_op->open() Miklos Szeredi
2011-04-18 16:00 ` [PATCH 2/6] vfs: export do_splice_direct() to modules Miklos Szeredi
2011-04-18 16:00 ` [PATCH 3/6] vfs: introduce clone_private_mount() Miklos Szeredi
2011-04-18 16:00 ` [PATCH 4/6] overlay filesystem Miklos Szeredi
2011-04-18 16:00 ` [PATCH 5/6] overlayfs: add statfs support Miklos Szeredi
2011-04-18 16:00 ` [PATCH 6/6] overlay: overlay filesystem documentation Miklos Szeredi
2011-04-19 3:05 ` J. R. Okajima
2011-04-19 3:58 ` NeilBrown
2011-04-19 4:13 ` J. R. Okajima
2011-04-18 18:19 ` [PATCH 0/6] overlay filesystem Michal Suchanek
2011-04-19 9:39 ` Miklos Szeredi
2011-04-19 9:39 ` Miklos Szeredi
2011-04-19 9:43 ` [PATCH 1/2] ovl: fix missing include Miklos Szeredi
2011-04-19 9:43 ` [PATCH 2/2] ovl: fix building as a module Miklos Szeredi
2011-05-09 19:14 ` [PATCH 0/6] overlay filesystem Michal Suchanek
2011-05-10 16:30 ` Miklos Szeredi
2011-05-10 16:30 ` Miklos Szeredi
-- strict thread matches above, loose matches on Subject: below --
2010-09-03 13:41 [PATCH 0/6] overlay filesystem prototype Miklos Szeredi
2010-09-03 13:41 ` [PATCH 6/6] overlay: overlay filesystem documentation Miklos Szeredi
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