CIFS: keep FileInfo handle live during oplock break
authorAurelien Aptel <aaptel@suse.com>
Fri, 29 Mar 2019 09:49:12 +0000 (10:49 +0100)
committerSteve French <stfrench@microsoft.com>
Tue, 16 Apr 2019 14:38:38 +0000 (09:38 -0500)
commitb98749cac4a695f084a5ff076f4510b23e353ecd
treeb1b5aa35d4d1410bef00756fb2aacb125f5cb729
parente6d0fb7b34f264f72c33053558a360a6a734905e
CIFS: keep FileInfo handle live during oplock break

In the oplock break handler, writing pending changes from pages puts
the FileInfo handle. If the refcount reaches zero it closes the handle
and waits for any oplock break handler to return, thus causing a deadlock.

To prevent this situation:

* We add a wait flag to cifsFileInfo_put() to decide whether we should
  wait for running/pending oplock break handlers

* We keep an additionnal reference of the SMB FileInfo handle so that
  for the rest of the handler putting the handle won't close it.
  - The ref is bumped everytime we queue the handler via the
    cifs_queue_oplock_break() helper.
  - The ref is decremented at the end of the handler

This bug was triggered by xfstest 464.

Also important fix to address the various reports of
oops in smb2_push_mandatory_locks

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
CC: Stable <stable@vger.kernel.org>
fs/cifs/cifsglob.h
fs/cifs/file.c
fs/cifs/misc.c
fs/cifs/smb2misc.c