Currently inode reference is held by fsnotify marks. Change the rules so
that inode reference is held by fsnotify_mark_connector structure
whenever the list is non-empty. This simplifies the code and is more
logical.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Move pointer to inode / vfsmount from mark itself to the
fsnotify_mark_connector structure. This is another step on the path
towards decoupling inode / vfsmount lifetime from notification mark
lifetime.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Currently notification marks are attached to object (inode or vfsmnt) by
a hlist_head in the object. The list is also protected by a spinlock in
the object. So while there is any mark attached to the list of marks,
the object must be pinned in memory (and thus e.g. last iput() deleting
inode cannot happen). Also for list iteration in fsnotify() to work, we
must hold fsnotify_mark_srcu lock so that mark itself and
mark->obj_list.next cannot get freed. Thus we are required to wait for
response to fanotify events from userspace process with
fsnotify_mark_srcu lock held. That causes issues when userspace process
is buggy and does not reply to some event - basically the whole
notification subsystem gets eventually stuck.
So to be able to drop fsnotify_mark_srcu lock while waiting for
response, we have to pin the mark in memory and make sure it stays in
the object list (as removing the mark waiting for response could lead to
lost notification events for groups later in the list). However we don't
want inode reclaim to block on such mark as that would lead to system
just locking up elsewhere.
This commit is the first in the series that paves way towards solving
these conflicting lifetime needs. Instead of anchoring the list of marks
directly in the object, we anchor it in a dedicated structure
(fsnotify_mark_connector) and just point to that structure from the
object. The following commits will also add spinlock protecting the list
and object pointer to the structure.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Add a comment that lifetime of a notification mark is protected by SRCU
and remove a comment about clearing of marks attached to the inode. It
is stale and more uptodate version is at fsnotify_destroy_marks() which
is the function handling this case.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
There are only two calls sites of fsnotify_duplicate_mark(). Those are
in kernel/audit_tree.c and both are bogus. Vfsmount pointer is unused
for audit tree, inode pointer and group gets set in
fsnotify_add_mark_locked() later anyway, mask and free_mark are already
set in alloc_chunk(). In fact, calling fsnotify_duplicate_mark() is
actively harmful because following fsnotify_add_mark_locked() will leak
group reference by overwriting the group pointer. So just remove the two
calls to fsnotify_duplicate_mark() and the function.
Signed-off-by: Jan Kara <jack@suse.cz>
[PM: line wrapping to fit in 80 chars]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Inotify instance is destroyed when all references to it are dropped.
That not only means that the corresponding file descriptor needs to be
closed but also that all corresponding instance marks are freed (as each
mark holds a reference to the inotify instance). However marks are
freed only after SRCU period ends which can take some time and thus if
user rapidly creates and frees inotify instances, number of existing
inotify instances can exceed max_user_instances limit although from user
point of view there is always at most one existing instance. Thus
inotify_init() returns EMFILE error which is hard to justify from user
point of view. This problem is exposed by LTP inotify06 testcase on
some machines.
We fix the problem by making sure all group marks are properly freed
while destroying inotify instance. We wait for SRCU period to end in
that path anyway since we have to make sure there is no event being
added to the instance while we are tearing down the instance. So it
takes only some plumbing to allow for marks to be destroyed in that path
as well and not from a dedicated work item.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>
Tested-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We don't require a dedicated thread for fsnotify cleanup. Switch it
over to a workqueue job instead that runs on the system_unbound_wq.
In the interest of not thrashing the queued job too often when there are
a lot of marks being removed, we delay the reaper job slightly when
queueing it, to allow several to gather on the list.
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Tested-by: Eryu Guan <guaneryu@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Eric Paris <eparis@parisplace.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This reverts commit c510eff6be ("fsnotify: destroy marks with
call_srcu instead of dedicated thread").
Eryu reported that he was seeing some OOM kills kick in when running a
testcase that adds and removes inotify marks on a file in a tight loop.
The above commit changed the code to use call_srcu to clean up the
marks. While that does (in principle) work, the srcu callback job is
limited to cleaning up entries in small batches and only once per jiffy.
It's easily possible to overwhelm that machinery with too many call_srcu
callbacks, and Eryu's reproduer did just that.
There's also another potential problem with using call_srcu here. While
you can obviously sleep while holding the srcu_read_lock, the callbacks
run under local_bh_disable, so you can't sleep there.
It's possible when putting the last reference to the fsnotify_mark that
we'll end up putting a chain of references including the fsnotify_group,
uid, and associated keys. While I don't see any obvious ways that that
could occurs, it's probably still best to avoid using call_srcu here
after all.
This patch reverts the above patch. A later patch will take a different
approach to eliminated the dedicated thread here.
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Reported-by: Eryu Guan <guaneryu@gmail.com>
Tested-by: Eryu Guan <guaneryu@gmail.com>
Cc: Jan Kara <jack@suse.com>
Cc: Eric Paris <eparis@parisplace.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
At the time that this code was originally written, call_srcu didn't
exist, so this thread was required to ensure that we waited for that
SRCU grace period to settle before finally freeing the object.
It does exist now however and we can much more efficiently use call_srcu
to handle this. That also allows us to potentially use srcu_barrier to
ensure that they are all of the callbacks have run before proceeding.
In order to conserve space, we union the rcu_head with the g_list.
This will be necessary for nfsd which will allocate marks from a
dedicated slabcache. We have to be able to ensure that all of the
objects are destroyed before destroying the cache. That's fairly
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Cc: Eric Paris <eparis@parisplace.org>
Reviewed-by: Jan Kara <jack@suse.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fsnotify_destroy_mark_locked() is subtle to use because it temporarily
releases group->mark_mutex. To avoid future problems with this
function, split it into two.
fsnotify_detach_mark() is the part that needs group->mark_mutex and
fsnotify_free_mark() is the part that must be called outside of
group->mark_mutex. This way it's much clearer what's going on and we
also avoid some pointless acquisitions of group->mark_mutex.
Signed-off-by: Jan Kara <jack@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Free list is used when all marks on given inode / mount should be
destroyed when inode / mount is going away. However we can free all of
the marks without using a special list with some care.
Signed-off-by: Jan Kara <jack@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fsnotify_clear_marks_by_group_flags() can race with
fsnotify_destroy_marks() so that when fsnotify_destroy_mark_locked()
drops mark_mutex, a mark from the list iterated by
fsnotify_clear_marks_by_group_flags() can be freed and thus the next
entry pointer we have cached may become stale and we dereference free
memory.
Fix the problem by first moving marks to free to a special private list
and then always free the first entry in the special list. This method
is safe even when entries from the list can disappear once we drop the
lock.
Signed-off-by: Jan Kara <jack@suse.com>
Reported-by: Ashish Sangwan <a.sangwan@samsung.com>
Reviewed-by: Ashish Sangwan <a.sangwan@samsung.com>
Cc: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This reverts commit a2673b6e04.
Kinglong Mee reports a memory leak with that patch, and Jan Kara confirms:
"Thanks for report! You are right that my patch introduces a race
between fsnotify kthread and fsnotify_destroy_group() which can result
in leaking inotify event on group destruction.
I haven't yet decided whether the right fix is not to queue events for
dying notification group (as that is pointless anyway) or whether we
should just fix the original problem differently... Whenever I look
at fsnotify code mark handling I get lost in the maze of locks, lists,
and subtle differences between how different notification systems
handle notification marks :( I'll think about it over night"
and after thinking about it, Jan says:
"OK, I have looked into the code some more and I found another
relatively simple way of fixing the original oops. It will be IMHO
better than trying to fixup this issue which has more potential for
breakage. I'll ask Linus to revert the fsnotify fix he already merged
and send a new fix"
Reported-by: Kinglong Mee <kinglongmee@gmail.com>
Requested-by: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fsnotify_clear_marks_by_group_flags() can race with
fsnotify_destroy_marks() so when fsnotify_destroy_mark_locked() drops
mark_mutex, a mark from the list iterated by
fsnotify_clear_marks_by_group_flags() can be freed and we dereference free
memory in the loop there.
Fix the problem by keeping mark_mutex held in
fsnotify_destroy_mark_locked(). The reason why we drop that mutex is that
we need to call a ->freeing_mark() callback which may acquire mark_mutex
again. To avoid this and similar lock inversion issues, we move the call
to ->freeing_mark() callback to the kthread destroying the mark.
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Ashish Sangwan <a.sangwan@samsung.com>
Suggested-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
destroy_list is used to track marks which still need waiting for srcu
period end before they can be freed. However by the time mark is added to
destroy_list it isn't in group's list of marks anymore and thus we can
reuse fsnotify_mark->g_list for queueing into destroy_list. This saves
two pointers for each fsnotify_mark.
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Eric Paris <eparis@redhat.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There's a lot of common code in inode and mount marks handling. Factor it
out to a common helper function.
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Eric Paris <eparis@redhat.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fsnotify() needs to merge inode and mount marks lists when notifying
groups about events so that ignore masks from inode marks are reflected
in mount mark notifications and groups are notified in proper order
(according to priorities).
Currently the sorting of the lists done by fsnotify_add_inode_mark() /
fsnotify_add_vfsmount_mark() and fsnotify() differed which resulted
ignore masks not being used in some cases.
Fix the problem by always using the same comparison function when
sorting / merging the mark lists.
Thanks to Heinrich Schuchardt for improvements of my patch.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=87721
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Tested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Do not initialize private_destroy_list twice. list_replace_init()
already takes care of initializing private_destroy_list. We don't need
to initialize it with LIST_HEAD() beforehand.
Signed-off-by: David Cohen <david.a.cohen@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There have been changes in the locking scheme of fsnotify but the
comments in the source code have not been updated yet. This patch
corrects this.
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Cc: Eric Paris <eparis@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In clear_marks_by_group_flags() the mark list of a group is iterated and the
marks are put on a temporary list.
Since we introduced fsnotify_destroy_mark_locked() we dont need the temp list
any more and are able to remove the marks while the mark list is iterated and
the mark list mutex is held.
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
This patch introduces fsnotify_add_mark_locked() and fsnotify_remove_mark_locked()
which are essentially the same as fsnotify_add_mark() and fsnotify_remove_mark() but
assume that the caller has already taken the groups mark mutex.
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
In fsnotify_destroy_mark() dont get the group from the passed mark anymore,
but pass the group itself as an additional parameter to the function.
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
Replaces the groups mark_lock spinlock with a mutex. Using a mutex instead
of a spinlock results in more flexibility (i.e it allows to sleep while the
lock is held).
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
Race-free addition and removal of a mark to a groups mark list would be easier
if we could lock the mark list of group before we lock the specific mark.
This patch changes the order used to add/remove marks to/from mark lists from
1. mark->lock
2. group->mark_lock
3. inode->i_lock
to
1. group->mark_lock
2. mark->lock
3. inode->i_lock
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
Get a group ref for each mark that is added to the groups list and release that
ref when the mark is freed in fsnotify_put_mark().
We also use get a group reference for duplicated marks and for private event
data.
Now we dont free a group any more when the number of marks becomes 0 but when
the groups ref count does. Since this will only happen when all marks are removed
from a groups mark list, we dont have to set the groups number of marks to 1 at
group creation.
Beside clearing all marks in fsnotify_destroy_group() we do also flush the
groups event queue. This is since events may hold references to groups (due to
private event data) and we have to put those references first before we get a
chance to put the final ref, which will result in a call to
fsnotify_final_destroy_group().
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
Removing the parent of a watched file results in "kernel BUG at
fs/notify/mark.c:139".
To reproduce
add "-w /tmp/audit/dir/watched_file" to audit.rules
rm -rf /tmp/audit/dir
This is caused by fsnotify_destroy_mark() being called without an
extra reference taken by the caller.
Reported by Francesco Cosoleto here:
https://bugzilla.novell.com/show_bug.cgi?id=689860
Fix by removing the BUG_ON and adding a comment about not accessing mark after
the iput.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This allows us to move duplicated code in <asm/atomic.h>
(atomic_inc_not_zero() for now) to <linux/atomic.h>
Signed-off-by: Arun Sharma <asharma@fb.com>
Reviewed-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Miller <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
All that remains of the inode_lock is protecting the inode hash list
manipulation and traversals. Rename the inode_lock to
inode_hash_lock to reflect it's actual function.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The global fsnotify groups lists were invented as a way to increase the
performance of fsnotify by shortcutting events which were not interesting.
With the changes to walk the object lists rather than global groups lists
these shortcuts are not useful.
Signed-off-by: Eric Paris <eparis@redhat.com>
Instead of moving list elements from destroy_list to &private_destroy_list,
exchange the list heads.
Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
Currently reading the inode->i_fsnotify_marks or
vfsmount->mnt_fsnotify_marks lists are protected by a spinlock on both the
read and the write side. This patch protects the read side of those lists
with a new single srcu.
Signed-off-by: Eric Paris <eparis@redhat.com>
Currently fsnotify check is mark->group is NULL to decide if
fsnotify_destroy_mark() has already been called or not. With the upcoming
rcu work it is a heck of a lot easier to use an explicit flag than worry
about group being set to NULL.
Signed-off-by: Eric Paris <eparis@redhat.com>
fsnotify takes an igrab on an inode when it adds a mark. The code was
supposed to drop the reference when the mark was removed but didn't.
This caused problems when an fs was unmounted because those inodes would
clearly not be gone. Thus resulting in the most devistating of messages:
VFS: Busy inodes after unmount of loop0. Self-destruct in 5 seconds.
>>> Have a nice day...
Jiri Slaby bisected the problem to a patch in the fsnotify tree. The
code snippets below show my stupidity quite clearly.
void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
{
...
mark->inode = NULL;
...
}
void fsnotify_destroy_mark(struct fsnotify_mark *mark)
{
struct inode *inode = NULL;
...
if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
fsnotify_destroy_inode_mark(mark);
inode = mark->i.inode;
}
...
if (inode)
iput(inode);
...
}
Obviously the intent was to capture the inode before it was set to NULL in
fsnotify_destory_inode_mark() so we wouldn't be leaking inodes forever.
Instead we leaked them (and exploded on umount)
Reported-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
fanotify listeners may want to clear all marks. They may want to do this
to destroy all of their inode marks which have nothing but ignores.
Realistically this is useful for av vendors who update policy and want to
clear all of their cached allows.
Signed-off-by: Eric Paris <eparis@redhat.com>
The ignored_mask is a new mask which is part of fsnotify marks. A group's
should_send_event() function can use the ignored mask to determine that
certain events are not of interest. In particular if a group registers a
mask including FS_OPEN on a vfsmount they could add FS_OPEN to the
ignored_mask for individual inodes and not send open events for those
inodes.
Signed-off-by: Eric Paris <eparis@redhat.com>
inotify marks must pin inodes in core. dnotify doesn't technically need to
since they are closed when the directory is closed. fanotify also need to
pin inodes in core as it works today. But the next step is to introduce
the concept of 'ignored masks' which is actually a mask of events for an
inode of no interest. I claim that these should be liberally sent to the
kernel and should not pin the inode in core. If the inode is brought back
in the listener will get an event it may have thought excluded, but this is
not a serious situation and one any listener should deal with.
This patch lays the ground work for non-pinning inode marks by using lazy
inode pinning. We do not pin a mark until it has a non-zero mask entry. If a
listener new sets a mask we never pin the inode.
Signed-off-by: Eric Paris <eparis@redhat.com>
Much like inode-mark.c has all of the code dealing with marks on inodes
this patch adds a vfsmount-mark.c which has similar code but is intended
for marks on vfsmounts.
Signed-off-by: Eric Paris <eparis@redhat.com>
Currently fsnotify_init_mark sets some fields to 0/NULL. Some users
already used some sorts of zalloc, some didn't. This patch uses memset to
explicitly zero everything in the fsnotify_mark when it is initialized so we
don't have to be careful if fields are later added to marks.
Signed-off-by: Eric Paris <eparis@redhat.com>
currently all marking is done by functions in inode-mark.c. Some of this
is pretty generic and should be instead done in a generic function and we
should only put the inode specific code in inode-mark.c
Signed-off-by: Eric Paris <eparis@redhat.com>
Jan Kara