Fix a leak in s_fsnotify_connectors counter in case of a race between
concurrent add of new fsnotify mark to an object.
The task that lost the race fails to drop the counter before freeing
the unused connector.
Following umount() hangs in fsnotify_sb_delete()/wait_var_event(),
because s_fsnotify_connectors never drops to zero.
Fixes: ec44610fe2 ("fsnotify: count all objects with attached connectors")
Reported-by: Murphy Zhou <jencce.kernel@gmail.com>
Link: https://lore.kernel.org/linux-fsdevel/20210907063338.ycaw6wvhzrfsfdlp@xzhoux.usersys.redhat.com/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Rename s_fsnotify_inode_refs to s_fsnotify_connectors and count all
objects with attached connectors, not only inodes with attached
connectors.
This will be used to optimize fsnotify() calls on sb without any
type of marks.
Link: https://lore.kernel.org/r/20210810151220.285179-4-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Matthew Bobrowski <repnop@google.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Instead of incrementing s_fsnotify_inode_refs when detaching connector
from inode, increment it earlier when attaching connector to inode.
Next patch is going to use s_fsnotify_inode_refs to count all objects
with attached connectors.
Link: https://lore.kernel.org/r/20210810151220.285179-3-amir73il@gmail.com
Reviewed-by: Matthew Bobrowski <repnop@google.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
fanotify has some hardcoded limits. The only APIs to escape those limits
are FAN_UNLIMITED_QUEUE and FAN_UNLIMITED_MARKS.
Allow finer grained tuning of the system limits via sysfs tunables under
/proc/sys/fs/fanotify, similar to tunables under /proc/sys/fs/inotify,
with some minor differences.
- max_queued_events - global system tunable for group queue size limit.
Like the inotify tunable with the same name, it defaults to 16384 and
applies on initialization of a new group.
- max_user_marks - user ns tunable for marks limit per user.
Like the inotify tunable named max_user_watches, on a machine with
sufficient RAM and it defaults to 1048576 in init userns and can be
further limited per containing user ns.
- max_user_groups - user ns tunable for number of groups per user.
Like the inotify tunable named max_user_instances, it defaults to 128
in init userns and can be further limited per containing user ns.
The slightly different tunable names used for fanotify are derived from
the "group" and "mark" terminology used in the fanotify man pages and
throughout the code.
Considering the fact that the default value for max_user_instances was
increased in kernel v5.10 from 8192 to 1048576, leaving the legacy
fanotify limit of 8192 marks per group in addition to the max_user_marks
limit makes little sense, so the per group marks limit has been removed.
Note that when a group is initialized with FAN_UNLIMITED_MARKS, its own
marks are not accounted in the per user marks account, so in effect the
limit of max_user_marks is only for the collection of groups that are
not initialized with FAN_UNLIMITED_MARKS.
Link: https://lore.kernel.org/r/20210304112921.3996419-2-amir73il@gmail.com
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Sparse reports warnings at fsnotify_prepare_user_wait()
and at fsnotify_finish_user_wait()
warning: context imbalance in fsnotify_finish_user_wait()
- wrong count at exit
warning: context imbalance in fsnotify_prepare_user_wait()
- unexpected unlock
The root cause is the missing annotation at fsnotify_finish_user_wait()
and at fsnotify_prepare_user_wait()
fsnotify_prepare_user_wait() has an extra annotation __release()
that only tell Sparse and not GCC to shutdown the warning
Add the missing __acquires(&fsnotify_mark_srcu) annotation
Add the missing __releases(&fsnotify_mark_srcu) annotation
Add the __release(&fsnotify_mark_srcu) annotation.
Link: https://lore.kernel.org/r/20200413214240.15245-1-jbi.octave@gmail.com
Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
The knfsd file cache will need to detect when files are unlinked, so that
it can close the associated cached files. Export a minimal set of notifier
functions to allow it to do so.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
When implementing connector fsid cache, we only initialized the cache
when the first mark added to object was added by FAN_REPORT_FID group.
We forgot to update conn->fsid when the second mark is added by
FAN_REPORT_FID group to an already attached connector without fsid
cache.
Reported-and-tested-by: syzbot+c277e8e2f46414645508@syzkaller.appspotmail.com
Fixes: 77115225ac ("fanotify: cache fsid in fsnotify_mark_connector")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 or at your option any
later version this program is distributed in the hope that it will
be useful but without any warranty without even the implied warranty
of merchantability or fitness for a particular purpose see the gnu
general public license for more details you should have received a
copy of the gnu general public license along with this program see
the file copying if not write to the free software foundation 675
mass ave cambridge ma 02139 usa
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 52 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jilayne Lovejoy <opensource@jilayne.com>
Reviewed-by: Steve Winslow <swinslow@gmail.com>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190519154042.342335923@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add a comment explaining why WRITE_ONCE() is enough when setting
mark->connector which can get dereferenced by RCU protected readers.
Signed-off-by: Jan Kara <jack@suse.cz>
fanotify_get_fsid() is reading mark->connector->fsid under srcu. It can
happen that it sees mark not fully initialized or mark that is already
detached from the object list. In these cases mark->connector
can be NULL leading to NULL ptr dereference. Fix the problem by
being careful when reading mark->connector and check it for being NULL.
Also use WRITE_ONCE when writing the mark just to prevent compiler from
doing something stupid.
Reported-by: syzbot+15927486a4f1bfcbaf91@syzkaller.appspotmail.com
Fixes: 77115225ac ("fanotify: cache fsid in fsnotify_mark_connector")
Signed-off-by: Jan Kara <jack@suse.cz>
For FAN_REPORT_FID, we need to encode fid with fsid of the filesystem on
every event. To avoid having to call vfs_statfs() on every event to get
fsid, we store the fsid in fsnotify_mark_connector on the first time we
add a mark and on handle event we use the cached fsid.
Subsequent calls to add mark on the same object are expected to pass the
same fsid, so the call will fail on cached fsid mismatch.
If an event is reported on several mark types (inode, mount, filesystem),
all connectors should already have the same fsid, so we use the cached
fsid from the first connector.
[JK: Simplify code flow around fanotify_get_fid()
make fsid argument of fsnotify_add_mark_locked() unconditional]
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Detaching of mark connector from fsnotify_put_mark() can race with
unmounting of the filesystem like:
CPU1 CPU2
fsnotify_put_mark()
spin_lock(&conn->lock);
...
inode = fsnotify_detach_connector_from_object(conn)
spin_unlock(&conn->lock);
generic_shutdown_super()
fsnotify_unmount_inodes()
sees connector detached for inode
-> nothing to do
evict_inode()
barfs on pending inode reference
iput(inode);
Resulting in "Busy inodes after unmount" message and possible kernel
oops. Make fsnotify_unmount_inodes() properly wait for outstanding inode
references from detached connectors.
Note that the accounting of outstanding inode references in the
superblock can cause some cacheline contention on the counter. OTOH it
happens only during deletion of the last notification mark from an inode
(or during unlinking of watched inode) and that is not too bad. I have
measured time to create & delete inotify watch 100000 times from 64
processes in parallel (each process having its own inotify group and its
own file on a shared superblock) on a 64 CPU machine. Average and
standard deviation of 15 runs look like:
Avg Stddev
Vanilla 9.817400 0.276165
Fixed 9.710467 0.228294
So there's no statistically significant difference.
Fixes: 6b3f05d24d ("fsnotify: Detach mark from object list when last reference is dropped")
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Add the infrastructure to attach a mark to a super_block struct
and detach all attached marks when super block is destroyed.
This is going to be used by fanotify backend to setup super block
marks.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
When inode is getting deleted and someone else holds reference to a mark
attached to the inode, we just detach the connector from the inode. In
that case fsnotify_put_mark() called from fsnotify_destroy_marks() will
decide to recalculate mask for the inode and __fsnotify_recalc_mask()
will WARN about invalid connector type:
WARNING: CPU: 1 PID: 12015 at fs/notify/mark.c:139
__fsnotify_recalc_mask+0x2d7/0x350 fs/notify/mark.c:139
Actually there's no reason to warn about detached connector in
__fsnotify_recalc_mask() so just silently skip updating the mask in such
case.
Reported-by: syzbot+c34692a51b9a6ca93540@syzkaller.appspotmail.com
Fixes: 3ac70bfcde ("fsnotify: add helper to get mask from connector")
Signed-off-by: Jan Kara <jack@suse.cz>
Use a helper to get the mask from the object (i.e. i_fsnotify_mask)
to generalize code of add/remove inode/vfsmount mark.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Make the code to attach/detach a connector to object more generic
by letting the fsnotify connector point to an abstract fsnotify_connp_t.
Code that needs to dereference an inode or mount object now uses the
helpers fsnotify_conn_{inode,mount}.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Instead of passing inode and vfsmount arguments to fsnotify_add_mark()
and its _locked variant, pass an abstract object pointer and the object
type.
The helpers fsnotify_obj_{inode,mount} are added to get the concrete
object pointer from abstract object pointer.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
The object marks manipulation functions fsnotify_destroy_marks()
fsnotify_find_mark() and their helpers take an argument of type
struct fsnotify_mark_connector __rcu ** to dereference the connector
pointer. use a typedef to describe this type for brevity.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Make some code that handles marks of object types inode and vfsmount
generic, so it can handle other object types.
Introduce fsnotify_foreach_obj_type macro to iterate marks by object type
and fsnotify_iter_{should|set}_report_type macros to set/test report_mask.
This is going to be used for adding mark of another object type
(super block mark).
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
An fsnotify_mark_connector is referencing a single type of object
(either inode or vfsmount). Instead of storing a type mask in
connector->flags, store a single type id in connector->type to
identify the type of object.
When a connector object is detached from the object, its type is set
to FSNOTIFY_OBJ_TYPE_DETACHED and this object is not going to be
reused.
The function fsnotify_clear_marks_by_group() is the only place where
type mask was used, so use type flags instead of type id to this
function.
This change is going to be more convenient when adding a new object
type (super block).
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable fsnotify_mark.refcnt is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Blind increment of group's user_waits is not enough, we could be far enough
in the group's destruction that it isn't taken into account (i.e. grabbing
the mark ref afterwards doesn't guarantee that it was the ref coming from
the _group_ that was grabbed).
Instead we need to check (under lock) that the mark is still attached to
the group after having obtained a ref to the mark. If not, skip it.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 9385a84d7e ("fsnotify: Pass fsnotify_iter_info into handle_event handler")
Cc: <stable@vger.kernel.org> # v4.12
Signed-off-by: Jan Kara <jack@suse.cz>
This patch doesn't actually fix any bug, just paves the way for fixing mark
and group pinning.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org> # v4.12
Signed-off-by: Jan Kara <jack@suse.cz>
When fsnotify_add_mark_locked() fails it cleans up the mark it was
adding. Since the mark is already visible in group's list, we should
protect update of mark->flags with mark->lock. I'm not aware of any real
issues this could cause (since we also hold group->mark_mutex) but
better be safe and obey locking rules properly.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
We recently shifted this code around, so we're no longer holding the
lock on this path.
Fixes: 755b5bc681 ("fsnotify: Remove indirection from mark list addition")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Pointer to ->free_mark callback unnecessarily occupies one long in each
fsnotify_mark although they are the same for all marks from one
notification group. Move the callback pointer to fsnotify_ops.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Currently we initialize mark->group only in fsnotify_add_mark_lock().
However we will need to access fsnotify_ops of corresponding group from
fsnotify_put_mark() so we need mark->group initialized earlier. Do that
in fsnotify_init_mark() which has a consequence that once
fsnotify_init_mark() is called on a mark, the mark has to be destroyed
by fsnotify_put_mark().
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
The function is already mostly contained in what
fsnotify_clear_marks_by_group() does. Just update that function to not
select marks when all of them should be destroyed and remove
fsnotify_detach_group_marks().
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
The _flags() suffix in the function name was more confusing than
explaining so just remove it. Also rename the argument from 'flags' to
'type' to better explain what the function expects.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Suggested-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
These helpers are now only a simple assignment and just obfuscate
what is going on. Remove them.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
fanotify wants to drop fsnotify_mark_srcu lock when waiting for response
from userspace so that the whole notification subsystem is not blocked
during that time. This patch provides a framework for safely getting
mark reference for a mark found in the object list which pins the mark
in that list. We can then drop fsnotify_mark_srcu, wait for userspace
response and then safely continue iteration of the object list once we
reaquire fsnotify_mark_srcu.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Currently we queue all marks for destruction on group shutdown and then
destroy them from fsnotify_destroy_group() instead from a worker thread
which is the usual path. However worker can already be processing some
list of marks to destroy so this does not make 100% all marks are really
destroyed by the time group is shut down. This isn't a big problem as
each mark holds group reference and thus group stays partially alive
until all marks are really freed but there's no point in complicating
our lives - just wait for the delayed work to be finished instead.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Instead of removing mark from object list from fsnotify_detach_mark(),
remove the mark when last reference to the mark is dropped. This will
allow fanotify to wait for userspace response to event without having to
hold onto fsnotify_mark_srcu.
To avoid pinning inodes by elevated refcount (and thus e.g. delaying
file deletion) while someone holds mark reference, we detach connector
from the object also from fsnotify_destroy_marks() and not only after
removing last mark from the list as it was now.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Currently we queue mark into a list of marks for destruction in
__fsnotify_free_mark() and keep the last mark reference dangling. After the
worker waits for SRCU period, it drops the last reference to the mark
which frees it. This scheme has the disadvantage that if we hold
reference to a mark and drop and reacquire SRCU lock, the mark can get
freed immediately which is slightly inconvenient and we will need to
avoid this in the future.
Move to a scheme where queueing of mark into a list of marks for
destruction happens when the last reference to the mark is dropped. Also
drop reference to the mark held by group list already when mark is
removed from that list instead of dropping it only from the destruction
worker.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Currently we free fsnotify_mark_connector structure only when inode /
vfsmount is getting freed. This can however impose noticeable memory
overhead when marks get attached to inodes only temporarily. So free the
connector structure once the last mark is detached from the object.
Since notification infrastructure can be working with the connector
under the protection of fsnotify_mark_srcu, we have to be careful and
free the fsnotify_mark_connector only after SRCU period passes.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
So far list of marks attached to an object (inode / vfsmount) was
protected by i_lock or mnt_root->d_lock. This dictates that the list
must be empty before the object can be destroyed although the list is
now anchored in the fsnotify_mark_connector structure. Protect the list
by a spinlock in the fsnotify_mark_connector structure to decouple
lifetime of a list of marks from a lifetime of the object. This also
simplifies the code quite a bit since we don't have to differentiate
between inode and vfsmount lists in quite a few places anymore.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
After removing all the indirection it is clear that
hlist_del_init_rcu(&mark->obj_list);
in fsnotify_destroy_marks() is not needed as the mark gets removed from
the list shortly afterwards in fsnotify_destroy_mark() ->
fsnotify_detach_mark() -> fsnotify_detach_from_object(). Also there is
no problem with mark being visible on object list while we call
fsnotify_destroy_mark() as parallel destruction of marks from several
places is properly handled (as mentioned in the comment in
fsnotify_destroy_marks(). So just remove the list removal and also the
stale comment.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
We lock object list lock in fsnotify_detach_from_object() twice - once
to detach mark and second time to recalculate mask. That is unnecessary
and later it will become problematic as we will free the connector as
soon as there is no mark in it. So move recalculation of fsnotify mask
into the same critical section that is detaching mark.
This also removes recalculation of child dentry flags from
fsnotify_detach_from_object(). That is however fine. Those marks will
get recalculated once some event happens on a child.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
fsnotify_detach_mark() calls fsnotify_destroy_inode_mark() or
fsnotify_destroy_vfsmount_mark() to remove mark from object list. These
two functions are however very similar and differ only in the lock they
use to protect the object list of marks. Simplify the code by removing
the indirection and removing mark from the object list in a common
function.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Instead of passing spinlock into fsnotify_destroy_marks() determine it
directly in that function from the connector type. This will reduce code
churn when changing lock protecting list of marks.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Move locking of a mark list into fsnotify_find_mark(). This reduces code
churn in the following patch changing lock protecting the list.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Move locking of locks protecting a list of marks into
fsnotify_recalc_mask(). This reduces code churn in the following patch
which changes the lock protecting the list of marks.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Move fsnotify_destroy_marks() to be later in the fs/notify/mark.c. It
will need some functions that are declared after its current
declaration. No functional change.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Adding notification mark to object list has been currently done through
fsnotify_add_{inode|vfsmount}_mark() helpers from
fsnotify_add_mark_locked() which call fsnotify_add_mark_list(). Remove
this unnecessary indirection to simplify the code.
Pushing all the locking to fsnotify_add_mark_list() also allows us to
allocate the connector structure with GFP_KERNEL mode.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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>
