From c64e80d55db81df22a7f25b75ab4ba4c55db4749 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 6 Feb 2008 11:34:13 -0500 Subject: [PATCH] NLM: don't requeue block if it was invalidated while GRANT_MSG was in flight It's possible for lockd to catch a SIGKILL while a GRANT_MSG callback is in flight. If this happens we don't want lockd to insert the block back into the nlm_blocked list. This helps that situation, but there's still a possible race. Fixing that will mean adding real locking for nlm_blocked. Signed-off-by: Jeff Layton Signed-off-by: J. Bruce Fields --- fs/lockd/svclock.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c index 82db7b323b83..fe9bdb4a220c 100644 --- a/fs/lockd/svclock.c +++ b/fs/lockd/svclock.c @@ -795,6 +795,17 @@ static void nlmsvc_grant_callback(struct rpc_task *task, void *data) dprintk("lockd: GRANT_MSG RPC callback\n"); + /* if the block is not on a list at this point then it has + * been invalidated. Don't try to requeue it. + * + * FIXME: it's possible that the block is removed from the list + * after this check but before the nlmsvc_insert_block. In that + * case it will be added back. Perhaps we need better locking + * for nlm_blocked? + */ + if (list_empty(&block->b_list)) + return; + /* Technically, we should down the file semaphore here. Since we * move the block towards the head of the queue only, no harm * can be done, though. */