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Author SHA1 Message Date
Eric Paris
90586523eb fsnotify: unified filesystem notification backend 
fsnotify is a backend for filesystem notification.  fsnotify does
not provide any userspace interface but does provide the basis
needed for other notification schemes such as dnotify.  fsnotify
can be extended to be the backend for inotify or the upcoming
fanotify.  fsnotify provides a mechanism for "groups" to register for
some set of filesystem events and to then deliver those events to
those groups for processing.

fsnotify has a number of benefits, the first being actually shrinking the size
of an inode.  Before fsnotify to support both dnotify and inotify an inode had

        unsigned long           i_dnotify_mask; /* Directory notify events */
        struct dnotify_struct   *i_dnotify; /* for directory notifications */
        struct list_head        inotify_watches; /* watches on this inode */
        struct mutex            inotify_mutex;  /* protects the watches list

But with fsnotify this same functionallity (and more) is done with just

        __u32                   i_fsnotify_mask; /* all events for this inode */
        struct hlist_head       i_fsnotify_mark_entries; /* marks on this inode */

That's right, inotify, dnotify, and fanotify all in 64 bits.  We used that
much space just in inotify_watches alone, before this patch set.

fsnotify object lifetime and locking is MUCH better than what we have today.
inotify locking is incredibly complex.  See 8f7b0ba1c8 as an example of
what's been busted since inception.  inotify needs to know internal semantics
of superblock destruction and unmounting to function.  The inode pinning and
vfs contortions are horrible.

no fsnotify implementers do allocation under locks.  This means things like
f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to
GFP_NOFS can be reverted.  There are no longer any allocation rules when using
or implementing your own fsnotify listener.

fsnotify paves the way for fanotify.  In brief fanotify is a notification
mechanism that delivers the lisener both an 'event' and an open file descriptor
to the object in question.  This means that fanotify is pathname agnostic.
Some on lkml may not care for the original companies or users that pushed for
TALPA, but fanotify was designed with flexibility and input for other users in
mind.  The readahead group expressed interest in fanotify as it could be used
to profile disk access on boot without breaking the audit system.  The desktop
search groups have also expressed interest in fanotify as it solves a number
of the race conditions and problems present with managing inotify when more
than a limited number of specific files are of interest.  fanotify can provide
for a userspace access control system which makes it a clean interface for AV
vendors to hook without trying to do binary patching on the syscall table,
LSM, and everywhere else they do their things today.  With this patch series
fanotify can be implemented in less than 1200 lines of easy to review code.
Almost all of which is the socket based user interface.

This patch series builds fsnotify to the point that it can implement
dnotify and inotify_user.  Patches exist and will be sent soon after
acceptance to finish the in kernel inotify conversion (audit) and implement
fanotify.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
 2009-06-11 14:57:52 -04:00
Nick Piggin
aabb8fdb41 fs: avoid I_NEW inodes 
To be on the safe side, it should be less fragile to exclude I_NEW inodes
from inode list scans by default (unless there is an important reason to
have them).

Normally they will get excluded (eg.  by zero refcount or writecount etc),
however it is a bit fragile for list walkers to know exactly what parts of
the inode state is set up and valid to test when in I_NEW.  So along these
lines, move I_NEW checks upward as well (sometimes taking I_FREEING etc
checks with them too -- this shouldn't be a problem should it?)

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
 2009-03-27 14:44:05 -04:00
Ingo Molnar
f04b30de3c inotify: fix GFP_KERNEL related deadlock 
Enhanced lockdep coverage of __GFP_NOFS turned up this new lockdep
assert:

[ 1093.677775]
[ 1093.677781] =================================
[ 1093.680031] [ INFO: inconsistent lock state ]
[ 1093.680031] 2.6.29-rc5-tip-01504-gb49eca1-dirty #1
[ 1093.680031] ---------------------------------
[ 1093.680031] inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.
[ 1093.680031] kswapd0/308 [HC0[0]:SC0[0]:HE1:SE1] takes:
[ 1093.680031]  (&inode->inotify_mutex){+.+.?.}, at: [<c0205942>] inotify_inode_is_dead+0x20/0x80
[ 1093.680031] {RECLAIM_FS-ON-W} state was registered at:
[ 1093.680031]   [<c01696b9>] mark_held_locks+0x43/0x5b
[ 1093.680031]   [<c016baa4>] lockdep_trace_alloc+0x6c/0x6e
[ 1093.680031]   [<c01cf8b0>] kmem_cache_alloc+0x20/0x150
[ 1093.680031]   [<c040d0ec>] idr_pre_get+0x27/0x6c
[ 1093.680031]   [<c02056e3>] inotify_handle_get_wd+0x25/0xad
[ 1093.680031]   [<c0205f43>] inotify_add_watch+0x7a/0x129
[ 1093.680031]   [<c020679e>] sys_inotify_add_watch+0x20f/0x250
[ 1093.680031]   [<c010389e>] sysenter_do_call+0x12/0x35
[ 1093.680031]   [<ffffffff>] 0xffffffff
[ 1093.680031] irq event stamp: 60417
[ 1093.680031] hardirqs last  enabled at (60417): [<c018d5f5>] call_rcu+0x53/0x59
[ 1093.680031] hardirqs last disabled at (60416): [<c018d5b9>] call_rcu+0x17/0x59
[ 1093.680031] softirqs last  enabled at (59656): [<c0146229>] __do_softirq+0x157/0x16b
[ 1093.680031] softirqs last disabled at (59651): [<c0106293>] do_softirq+0x74/0x15d
[ 1093.680031]
[ 1093.680031] other info that might help us debug this:
[ 1093.680031] 2 locks held by kswapd0/308:
[ 1093.680031]  #0:  (shrinker_rwsem){++++..}, at: [<c01b0502>] shrink_slab+0x36/0x189
[ 1093.680031]  #1:  (&type->s_umount_key#4){+++++.}, at: [<c01e6d77>] shrink_dcache_memory+0x110/0x1fb
[ 1093.680031]
[ 1093.680031] stack backtrace:
[ 1093.680031] Pid: 308, comm: kswapd0 Not tainted 2.6.29-rc5-tip-01504-gb49eca1-dirty #1
[ 1093.680031] Call Trace:
[ 1093.680031]  [<c016947a>] valid_state+0x12a/0x13d
[ 1093.680031]  [<c016954e>] mark_lock+0xc1/0x1e9
[ 1093.680031]  [<c016a5b4>] ? check_usage_forwards+0x0/0x3f
[ 1093.680031]  [<c016ab74>] __lock_acquire+0x2c6/0xac8
[ 1093.680031]  [<c01688d9>] ? register_lock_class+0x17/0x228
[ 1093.680031]  [<c016b3d3>] lock_acquire+0x5d/0x7a
[ 1093.680031]  [<c0205942>] ? inotify_inode_is_dead+0x20/0x80
[ 1093.680031]  [<c08824c4>] __mutex_lock_common+0x3a/0x4cb
[ 1093.680031]  [<c0205942>] ? inotify_inode_is_dead+0x20/0x80
[ 1093.680031]  [<c08829ed>] mutex_lock_nested+0x2e/0x36
[ 1093.680031]  [<c0205942>] ? inotify_inode_is_dead+0x20/0x80
[ 1093.680031]  [<c0205942>] inotify_inode_is_dead+0x20/0x80
[ 1093.680031]  [<c01e6672>] dentry_iput+0x90/0xc2
[ 1093.680031]  [<c01e67a3>] d_kill+0x21/0x45
[ 1093.680031]  [<c01e6a46>] __shrink_dcache_sb+0x27f/0x355
[ 1093.680031]  [<c01e6dc5>] shrink_dcache_memory+0x15e/0x1fb
[ 1093.680031]  [<c01b05ed>] shrink_slab+0x121/0x189
[ 1093.680031]  [<c01b0d12>] kswapd+0x39f/0x561
[ 1093.680031]  [<c01ae499>] ? isolate_pages_global+0x0/0x233
[ 1093.680031]  [<c0157eae>] ? autoremove_wake_function+0x0/0x43
[ 1093.680031]  [<c01b0973>] ? kswapd+0x0/0x561
[ 1093.680031]  [<c0157daf>] kthread+0x41/0x82
[ 1093.680031]  [<c0157d6e>] ? kthread+0x0/0x82
[ 1093.680031]  [<c01043ab>] kernel_thread_helper+0x7/0x10

inotify_handle_get_wd() does idr_pre_get() which does a
kmem_cache_alloc() without __GFP_FS - and is hence deadlockable under
extreme MM pressure.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: MinChan Kim <minchan.kim@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2009-02-18 15:37:56 -08:00
Eric Paris
272eb01485 filesystem notification: create fs/notify to contain all fs notification 
Creating a generic filesystem notification interface, fsnotify, which will be
used by inotify, dnotify, and eventually fanotify is really starting to
clutter the fs directory.  This patch simply moves inotify and dnotify into
fs/notify/inotify and fs/notify/dnotify respectively to make both current fs/
and future notification tidier.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
 2008-12-31 18:07:43 -05:00