Patch "sunrpc/cache: drop reference when sunrpc_cache_pipe_upcall() detects a race" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

sunrpc/cache: drop reference when sunrpc_cache_pipe_upcall() detects a race

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
sunrpc-cache-drop-reference-when-sunrpc_cache_pipe_upcall-detects-a-race.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: NeilBrown <[email protected]>
Date: Fri, 4 Mar 2016 17:20:13 +1100
Subject: sunrpc/cache: drop reference when sunrpc_cache_pipe_upcall() detects a race

From: NeilBrown <[email protected]>

commit a6ab1e8126d205238defbb55d23661a3a5c6a0d8 upstream.

sunrpc_cache_pipe_upcall() can detect a race if CACHE_PENDING is no longer set. In this case it aborts the queuing of the upcall.
However it has already taken a new counted reference on "h" and doesn't "put" it, even though it frees the data structure holding the reference.

So let's delay the "cache_get" until we know we need it.

---
 net/sunrpc/cache.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -1182,14 +1182,14 @@ int sunrpc_cache_pipe_upcall(struct cach
 	}
 
 	crq->q.reader = 0;
-	crq->item = cache_get(h);
 	crq->buf = buf;
 	crq->len = 0;
 	crq->readers = 0;
 	spin_lock(&queue_lock);
-	if (test_bit(CACHE_PENDING, &h->flags))
+	if (test_bit(CACHE_PENDING, &h->flags)) {
+		crq->item = cache_get(h);
 		list_add_tail(&crq->q.list, &detail->queue);
-	else
+	} else
 		/* Lost a race, no longer PENDING, so don't enqueue */
 		ret = -EAGAIN;
 	spin_unlock(&queue_lock);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/sunrpc-cache-drop-reference-when-sunrpc_cache_pipe_upcall-detects-a-race.patch