[PATCH AUTOSEL 4.19 362/671] afs: Fix lock-wait/callback-break double locking

Sasha Levin
2020-01-16T18:55:49Z

From: David Howells <dhowells@redhat.com>

[ 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>
---
fs/afs/callback.c | 8 +-------
fs/afs/flock.c | 3 ---
2 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index 4ad701250299..97283b04fa6f 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -221,14 +221,8 @@ 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 075fe7f94810..457ce62e5c0f 100644
--- 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);
--
2.20.1