afs: Fix lock-wait/callback-break double locking

BugLink: https://bugs.launchpad.net/bugs/1863019
[ Upstream commit c7226e407b6065d3bda8bd9dc627663d2c505ea3 ]

__afs_break_callback() holds vnode->lock around its call of
afs_lock_may_be_available() - which also takes that lock.

Fix this by not taking the lock in __afs_break_callback().

Also, there's no point checking the granted_locks and pending_locks queues;
it's sufficient to check lock_state, so move that check out of
afs_lock_may_be_available() into __afs_break_callback() to replace the
queue checks.

Fixes: e8d6c554126b ("AFS: implement file locking")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index 96125c9e3e17898d75caf53fe303a822338a4595..c3a12985871a7f9717dba2a5b019d6a71f37646f 100644 (file)
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -178,14 +178,8 @@ void afs_break_callback(struct afs_vnode *vnode)
                vnode->cb_break++;
                afs_clear_permits(vnode);
 
-               spin_lock(&vnode->lock);
-
-               _debug("break callback");
-
-               if (list_empty(&vnode->granted_locks) &&
-                   !list_empty(&vnode->pending_locks))
+               if (vnode->lock_state == AFS_VNODE_LOCK_WAITING_FOR_CB)
                        afs_lock_may_be_available(vnode);
-               spin_unlock(&vnode->lock);
        }
 
        write_sequnlock(&vnode->cb_lock);

diff --git a/fs/afs/flock.c b/fs/afs/flock.c
index ef7f4cb6251b8bd135ccb268d8c0da30ab3a368e..bc3c75f917f5774adceb828d191ea8c3d7746c2e 100644 (file)
--- a/fs/afs/flock.c
+++ b/fs/afs/flock.c
@@ -39,9 +39,6 @@ void afs_lock_may_be_available(struct afs_vnode *vnode)
 {
        _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
 
-       if (vnode->lock_state != AFS_VNODE_LOCK_WAITING_FOR_CB)
-               return;
-
        spin_lock(&vnode->lock);
        if (vnode->lock_state == AFS_VNODE_LOCK_WAITING_FOR_CB)
                afs_next_locker(vnode, 0);