Commit fded4e09 authored Sep 17, 2012 by Paul Clements Committed by Linus Torvalds Sep 17, 2012

nbd: clear waiting_queue on shutdown



Fix a serious but uncommon bug in nbd which occurs when there is heavy
I/O going to the nbd device while, at the same time, a failure (server,
network) or manual disconnect of the nbd connection occurs.

There is a small window between the time that the nbd_thread is stopped
and the socket is shutdown where requests can continue to be queued to
nbd's internal waiting_queue.  When this happens, those requests are
never completed or freed.

The fix is to clear the waiting_queue on shutdown of the nbd device, in
the same way that the nbd request queue (queue_head) is already being
cleared.

Signed-off-by: Paul Clements <paul.clements@steeleye.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent e9b7d7c8

drivers/block/nbd.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -449,6 +449,14 @@ static void nbd_clear_que(struct nbd_device *nbd)
		req->errors++;
		nbd_end_request(req);
		}

		while (!list_empty(&nbd->waiting_queue)) {
		req = list_entry(nbd->waiting_queue.next, struct request,
		queuelist);
		list_del_init(&req->queuelist);
		req->errors++;
		nbd_end_request(req);
		}
		}


		@@ -598,6 +606,7 @@ static int __nbd_ioctl(struct block_device bdev, struct nbd_device nbd,
		nbd->file = NULL;
		nbd_clear_que(nbd);
		BUG_ON(!list_empty(&nbd->queue_head));
		BUG_ON(!list_empty(&nbd->waiting_queue));
		if (file)
		fput(file);
		return 0;