cifs: simplify refcounting for oplock breaks

Currently, we take a sb->s_active reference and a cifsFileInfo reference
when an oplock break workqueue job is queued. This is unnecessary and
more complicated than it needs to be. Also as Al points out,
deactivate_super has non-trivial locking implications so it's best to
avoid that if we can.

Instead, just cancel any pending oplock breaks for this filehandle
synchronously in cifsFileInfo_put after taking it off the lists.
That should ensure that this job doesn't outlive the structures it
depends on.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 2 insertions, 9 deletions

diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 03a1f491..7c16933 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -585,15 +585,8 @@ is_valid_oplock_break(struct smb_hdr *buf, struct TCP_Server_Info *srv)
 
 				cifs_set_oplock_level(pCifsInode,
 					pSMB->OplockLevel ? OPLOCK_READ : 0);
-				/*
-				 * cifs_oplock_break_put() can't be called
-				 * from here.  Get reference after queueing
-				 * succeeded.  cifs_oplock_break() will
-				 * synchronize using cifs_file_list_lock.
-				 */
-				if (queue_work(system_nrt_wq,
-					       &netfile->oplock_break))
-					cifs_oplock_break_get(netfile);
+				queue_work(system_nrt_wq,
+					   &netfile->oplock_break);
 				netfile->oplock_break_cancelled = false;
 
 				spin_unlock(&cifs_file_list_lock);