From: David Howells <dhowells@redhat.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: dhowells@redhat.com, linux-api@vger.kernel.org,
torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 34/38] vfs: syscall: Add fsinfo() to query filesystem information [ver #10]
Date: Tue, 31 Jul 2018 13:39:16 +0100 [thread overview]
Message-ID: <1600.1533040756@warthog.procyon.org.uk> (raw)
In-Reply-To: <20180731041642.GH30522@ZenIV.linux.org.uk>
Al Viro <viro@ZenIV.linux.org.uk> wrote:
> Umm... What's so special about cell/volume/domain/realm?
Nothing particularly. But they're something various network filesystems might
find useful. cell for AFS, domain for CIFS, realm for things that use
kerberos.
volume_id/uuid/name would be usable by ext4 too, for example.
> And what do we do when a random filesystem gets added - should its
> parameters go into catch-all pile (attr_parameter),
FSINFO_ATTR_PARAMETER is a way to enumerate the configuration parameters
passed to mount, as an alternative to parsing /proc/mounts. So, for example,
afs has:
enum afs_param {
Opt_autocell,
Opt_dyn,
Opt_source,
nr__afs_params
};
static const struct fs_parameter_spec afs_param_specs[nr__afs_params] = {
[Opt_autocell] = { fs_param_takes_no_value },
[Opt_dyn] = { fs_param_takes_no_value },
[Opt_source] = { fs_param_is_string },
};
static const struct constant_table afs_param_keys[] = {
{ "autocell", Opt_autocell },
{ "dyn", Opt_dyn },
{ "source", Opt_source },
};
My thought is that calling fsinfo(..., "/some/afs/file", ¶ms, ...) with:
struct fsinfo_params params = {
.request = FSINFO_ATTR_PARAMETER,
.Nth = <parameter-number>,
};
would get you back, for example:
Nth Result
======= ==========================================
0 "autocell" (or "" if not set)
1 "dyn" (or "" if not set)
2 "source=%#grand.central.org:root.cell."
3+ -ENODATA (ie. there are no more)
where Nth corresponds to the parameter specified by
FSINFO_ATTR_PARAM_DESCRIPTION and Nth.
Now for some filesystems, cgroups-v1 for example, there are parameters beyond
the list (the subsystem name) and these can be listed after the predefined
parameters, eg.:
Nth Result
======= ==========================================
0 "all" or ""
1 "clone_children" or ""
2 "cpuset_v2_mode" or ""
3 "name" or ""
4 "none" or ""
5 "noprefix" or ""
6 "release_agent" or ""
7 "xattr" or ""
8 "<subsys0>" or ""
9 "<subsys1>" or ""
10 "<subsys2>" or ""
... -ENODATA
> or should they get classes of their own?
Yes.
> For Cthulhu sake, who's going to maintain that enum in face of
> random out-of-tree filesystems, each wanting a class or two its own?
They don't get their own numbers unless they're in-tree. Full stop. We have
the same issue with system calls and not-yet-upstream new syscalls.
Note that, as I have the code now, the "type" of return value for each
attribute must also be declared to the fsinfo() core, and the fsinfo core does
the copy to/from userspace.
> We'd tried that with device numbers; ask hpa how well has that
> worked and how much did he love the whole experience...
What would you do instead? I would prefer to avoid using text strings as keys
because then I need a big lookup table, and possibly this gets devolved to
each filesystem to handle - which ends up even more of a mess because then
there's nothing to hold consistency.
David
next prev parent reply other threads:[~2018-07-31 14:19 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-27 17:31 [PATCH 00/38] VFS: Introduce filesystem context [ver #10] David Howells
2018-07-27 17:31 ` [PATCH 01/38] vfs: syscall: Add open_tree(2) to reference or clone a mount " David Howells
2018-07-27 17:31 ` [PATCH 02/38] vfs: syscall: Add move_mount(2) to move mounts around " David Howells
2018-07-27 17:31 ` [PATCH 03/38] teach move_mount(2) to work with OPEN_TREE_CLONE " David Howells
2018-07-27 17:31 ` [PATCH 04/38] vfs: Suppress MS_* flag defs within the kernel unless explicitly enabled " David Howells
2018-07-27 17:31 ` [PATCH 05/38] vfs: Introduce the basic header for the new mount API's filesystem context " David Howells
2018-07-27 17:32 ` [PATCH 06/38] vfs: Introduce logging functions " David Howells
2018-07-27 17:32 ` [PATCH 07/38] vfs: Add configuration parser helpers " David Howells
2018-07-27 17:32 ` [PATCH 08/38] vfs: Add LSM hooks for the new mount API " David Howells
2018-07-27 17:32 ` [PATCH 09/38] selinux: Implement the new mount API LSM hooks " David Howells
2018-07-27 17:32 ` [PATCH 10/38] smack: Implement filesystem context security " David Howells
2018-07-27 17:32 ` [PATCH 11/38] apparmor: Implement security hooks for the new mount API " David Howells
2018-07-27 17:32 ` [PATCH 12/38] vfs: Pass key and value into LSM and FS and provide a helper parser " David Howells
2018-07-27 17:32 ` [PATCH 13/38] tomoyo: Implement security hooks for the new mount API " David Howells
2018-07-28 2:29 ` Tetsuo Handa
2018-07-30 10:49 ` David Howells
2018-07-27 17:32 ` [PATCH 14/38] vfs: Separate changing mount flags full remount " David Howells
2018-07-27 17:33 ` [PATCH 15/38] vfs: Implement a filesystem superblock creation/configuration context " David Howells
2018-07-27 17:33 ` [PATCH 16/38] vfs: Remove unused code after filesystem context changes " David Howells
2018-07-27 17:33 ` [PATCH 17/38] procfs: Move proc_fill_super() to fs/proc/root.c " David Howells
2018-07-27 17:33 ` [PATCH 18/38] proc: Add fs_context support to procfs " David Howells
2018-07-27 17:33 ` [PATCH 19/38] ipc: Convert mqueue fs to fs_context " David Howells
2018-07-27 17:33 ` [PATCH 20/38] cpuset: Use " David Howells
2018-07-27 17:33 ` [PATCH 21/38] kernfs, sysfs, cgroup, intel_rdt: Support " David Howells
2018-07-27 17:33 ` [PATCH 22/38] hugetlbfs: Convert to " David Howells
2018-07-27 17:33 ` [PATCH 23/38] vfs: Remove kern_mount_data() " David Howells
2018-07-27 17:34 ` [PATCH 24/38] vfs: Provide documentation for new mount API " David Howells
2018-07-27 17:34 ` [PATCH 25/38] Make anon_inodes unconditional " David Howells
2018-07-27 20:04 ` Randy Dunlap
2018-07-30 10:52 ` David Howells
2018-07-27 17:34 ` [PATCH 26/38] vfs: syscall: Add fsopen() to prepare for superblock creation " David Howells
2018-07-27 17:34 ` [PATCH 27/38] vfs: Implement logging through fs_context " David Howells
2018-07-27 17:34 ` [PATCH 28/38] vfs: Add some logging to the core users of the fs_context log " David Howells
2018-07-27 17:34 ` [PATCH 29/38] vfs: syscall: Add fsconfig() for configuring and managing a context " David Howells
2018-07-27 19:42 ` Andy Lutomirski
2018-07-27 21:51 ` David Howells
2018-07-27 21:57 ` Andy Lutomirski
2018-07-27 22:27 ` David Howells
2018-07-27 22:32 ` Jann Horn
2018-07-29 8:50 ` David Howells
2018-07-29 11:14 ` Jann Horn
2018-07-30 12:32 ` David Howells
2018-07-27 17:34 ` [PATCH 30/38] vfs: syscall: Add fsmount() to create a mount for a superblock " David Howells
2018-07-27 19:27 ` Andy Lutomirski
2018-07-27 19:43 ` Andy Lutomirski
2018-07-27 22:09 ` David Howells
2018-07-27 22:06 ` David Howells
2018-07-27 17:34 ` [PATCH 31/38] vfs: syscall: Add fspick() to select a superblock for reconfiguration " David Howells
2018-07-27 17:34 ` [PATCH 32/38] afs: Add fs_context support " David Howells
2018-07-27 17:35 ` [PATCH 33/38] afs: Use fs_context to pass parameters over automount " David Howells
2018-07-27 17:35 ` [PATCH 34/38] vfs: syscall: Add fsinfo() to query filesystem information " David Howells
2018-07-27 19:35 ` Andy Lutomirski
2018-07-27 22:12 ` David Howells
2018-07-27 23:14 ` Jann Horn
2018-07-27 23:49 ` David Howells
2018-07-28 0:14 ` Anton Altaparmakov
2018-07-27 23:51 ` David Howells
2018-07-27 23:58 ` Jann Horn
2018-07-28 0:08 ` David Howells
2018-07-30 14:48 ` David Howells
2018-07-31 4:16 ` Al Viro
2018-07-31 12:39 ` David Howells [this message]
2018-07-31 13:20 ` David Howells
2018-07-31 23:49 ` Darrick J. Wong
2018-08-01 1:07 ` David Howells
2018-07-27 17:35 ` [PATCH 35/38] afs: Add fsinfo support " David Howells
2018-07-27 17:35 ` [PATCH 36/38] vfs: Add a sample program for the new mount API " David Howells
2018-07-29 11:37 ` Pavel Machek
2018-07-30 12:23 ` David Howells
2018-07-30 14:31 ` Pavel Machek
2018-07-30 18:08 ` Matthew Wilcox
2018-07-30 18:16 ` Pavel Machek
2018-07-30 18:18 ` Linus Torvalds
2018-07-30 18:38 ` Matthew Wilcox
2018-07-30 18:59 ` Linus Torvalds
2018-07-30 19:49 ` Matthew Wilcox
2018-07-30 21:02 ` Theodore Y. Ts'o
2018-07-30 21:23 ` Pavel Machek
2018-07-30 23:58 ` Matthew Wilcox
2018-07-31 0:58 ` Theodore Y. Ts'o
2018-07-31 9:40 ` Pavel Machek
2018-07-31 10:11 ` David Howells
2018-07-31 11:34 ` Pavel Machek
2018-07-31 12:07 ` Matthew Wilcox
2018-07-31 12:28 ` Pavel Machek
2018-07-31 13:33 ` Al Viro
2018-07-31 13:00 ` David Howells
2018-07-31 19:39 ` Pavel Machek
2018-07-31 21:00 ` David Howells
2018-07-31 21:21 ` Linus Torvalds
2018-07-31 21:38 ` David Howells
2018-07-30 20:47 ` Pavel Machek
2018-07-30 15:33 ` David Howells
2018-07-30 17:30 ` Pavel Machek
2018-07-30 17:54 ` Linus Torvalds
2018-07-30 18:16 ` Pavel Machek
2018-07-27 17:35 ` [PATCH 37/38] vfs: Allow fsinfo() to query what's in an fs_context " David Howells
2018-07-27 17:35 ` [PATCH 38/38] vfs: Allow fsinfo() to be used to query an fs parameter description " David Howells
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