vfs: generate FS_CREATE before FS_OPEN when ->atomic_open used.

When a file is opened and created with open(..., O_CREAT) we get
both the CREATE and OPEN fsnotify events and would expect them in that
order.   For most filesystems we get them in that order because
open_last_lookups() calls fsnofify_create() and then do_open() (from
path_openat()) calls vfs_open()->do_dentry_open() which calls
fsnotify_open().

However when ->atomic_open is used, the
   do_dentry_open() -> fsnotify_open()
call happens from finish_open() which is called from the ->atomic_open
handler in lookup_open() which is called *before* open_last_lookups()
calls fsnotify_create.  So we get the "open" notification before
"create" - which is backwards.  ltp testcase inotify02 tests this and
reports the inconsistency.

This patch lifts the fsnotify_open() call out of do_dentry_open() and
places it higher up the call stack.  There are three callers of
do_dentry_open().

For vfs_open() and kernel_file_open() the fsnotify_open() is placed
directly in that caller so there should be no behavioural change.

For finish_open() there are two cases:
 - finish_open is used in ->atomic_open handlers.  For these we add a
   call to fsnotify_open() at open_last_lookups() if FMODE_OPENED is
   set - which means do_dentry_open() has been called.
 - finish_open is used in ->tmpfile() handlers.  For these a similar
   call to fsnotify_open() is added to vfs_tmpfile()

With this patch NFSv3 is restored to its previous behaviour (before
->atomic_open support was added) of generating CREATE notifications
before OPEN, and NFSv4 now has that same correct ordering that is has
not had before.  I haven't tested other filesystems.

Fixes: 7c6c5249f061 ("NFS: add atomic_open for NFSv3 to handle O_TRUNC correctly.")
Reported-by: James Clark <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]
Signed-off-by: NeilBrown <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Fixes: 7b8c9d7bb457 ("fsnotify: move fsnotify_open() hook into do_dentry_open()")
Tested-by: James Clark <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Amir Goldstein <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

0 files changed, 0 insertions, 0 deletions