linux-toradex.git/fs/notify, branch v4.6-rc6

fsnotify: turn fsnotify reaper thread into a workqueue job

2016-02-19T00:23:24+00:00

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 
Tested-by: Eryu Guan 
Reviewed-by: Jan Kara 
Cc: Eric Paris 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Revert "fsnotify: destroy marks with call_srcu instead of dedicated thread"

2016-02-19T00:23:24+00:00

This reverts commit c510eff6beba ("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 
Reported-by: Eryu Guan 
Tested-by: Eryu Guan 
Cc: Jan Kara 
Cc: Eric Paris 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fsnotify: destroy marks with call_srcu instead of dedicated thread

2016-01-15T00:00:49+00:00

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 
Cc: Eric Paris 
Reviewed-by: Jan Kara 
Cc: "Paul E. McKenney" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fs/notify/inode_mark.c: use list_next_entry in fsnotify_unmount_inodes

2016-01-15T00:00:49+00:00

To make the intention clearer, use list_next_entry instead of
list_entry.

Signed-off-by: Geliang Tang 
Reviewed-by: Jan Kara 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

inotify: actually check for invalid bits in sys_inotify_add_watch()

2015-11-06T03:34:48+00:00

The comment here says that it is checking for invalid bits.  But, the mask
is *actually* checking to ensure that _any_ valid bit is set, which is
quite different.

Without this check, an unexpected bit could get set on an inotify object.
Since these bits are also interpreted by the fsnotify/dnotify code, there
is the potential for an object to be mishandled inside the kernel.  For
instance, can we be sure that setting the dnotify flag FS_DN_RENAME on an
inotify watch is harmless?

Add the actual check which was intended.  Retain the existing inotify bits
are being added to the watch.  Plus, this is existing behavior which would
be nice to preserve.

I did a quick sniff test that inotify functions and that my
'inotify-tools' package passes 'make check'.

Signed-off-by: Dave Hansen 
Cc: John McCutchan 
Cc: Robert Love 
Cc: Eric Paris 
Cc: Josh Boyer 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

inotify: hide internal kernel bits from fdinfo

2015-11-06T03:34:48+00:00

There was a report that my patch:

    inotify: actually check for invalid bits in sys_inotify_add_watch()

broke CRIU.

The reason is that CRIU looks up raw flags in /proc/$pid/fdinfo/* to
figure out how to rebuild inotify watches and then passes those flags
directly back in to the inotify API.  One of those flags
(FS_EVENT_ON_CHILD) is set in mark->mask, but is not part of the inotify
API.  It is used inside the kernel to _implement_ inotify but it is not
and has never been part of the API.

My patch above ensured that we only allow bits which are part of the API
(IN_ALL_EVENTS).  This broke CRIU.

FS_EVENT_ON_CHILD is really internal to the kernel.  It is set _anyway_ on
all inotify marks.  So, CRIU was really just trying to set a bit that was
already set.

This patch hides that bit from fdinfo.  CRIU will not see the bit, not try
to set it, and should work as before.  We should not have been exposing
this bit in the first place, so this is a good patch independent of the
CRIU problem.

Signed-off-by: Dave Hansen 
Reported-by: Andrey Wagin 
Acked-by: Andrey Vagin 
Acked-by: Cyrill Gorcunov 
Acked-by: Eric Paris 
Cc: Pavel Emelyanov 
Cc: John McCutchan 
Cc: Robert Love 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2015-09-06T03:34:28+00:00

Pull vfs updates from Al Viro:
 "In this one:

   - d_move fixes (Eric Biederman)

   - UFS fixes (me; locking is mostly sane now, a bunch of bugs in error
     handling ought to be fixed)

   - switch of sb_writers to percpu rwsem (Oleg Nesterov)

   - superblock scalability (Josef Bacik and Dave Chinner)

   - swapon(2) race fix (Hugh Dickins)"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (65 commits)
  vfs: Test for and handle paths that are unreachable from their mnt_root
  dcache: Reduce the scope of i_lock in d_splice_alias
  dcache: Handle escaped paths in prepend_path
  mm: fix potential data race in SyS_swapon
  inode: don't softlockup when evicting inodes
  inode: rename i_wb_list to i_io_list
  sync: serialise per-superblock sync operations
  inode: convert inode_sb_list_lock to per-sb
  inode: add hlist_fake to avoid the inode hash lock in evict
  writeback: plug writeback at a high level
  change sb_writers to use percpu_rw_semaphore
  shift percpu_counter_destroy() into destroy_super_work()
  percpu-rwsem: kill CONFIG_PERCPU_RWSEM
  percpu-rwsem: introduce percpu_rwsem_release() and percpu_rwsem_acquire()
  percpu-rwsem: introduce percpu_down_read_trylock()
  document rwsem_release() in sb_wait_write()
  fix the broken lockdep logic in __sb_start_write()
  introduce __sb_writers_{acquired,release}() helpers
  ufs_inode_get{frag,block}(): get rid of 'phys' argument
  ufs_getfrag_block(): tidy up a bit
  ...

fsnotify: get rid of fsnotify_destroy_mark_locked()

2015-09-04T23:54:41+00:00

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 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fsnotify: remove mark->free_list

2015-09-04T23:54:41+00:00

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 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fsnotify: fix check in inotify fdinfo printing

2015-09-04T23:54:41+00:00

A check in inotify_fdinfo() checking whether mark is valid was always
true due to a bug.  Luckily we can never get to invalidated marks since
we hold mark_mutex and invalidated marks get removed from the group list
when they are invalidated under that mutex.

Anyway fix the check to make code more future proof.

Signed-off-by: Jan Kara 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds