From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935778AbZLQEZM (ORCPT ); Wed, 16 Dec 2009 23:25:12 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S936477AbZLQEYr (ORCPT ); Wed, 16 Dec 2009 23:24:47 -0500 Received: from kroah.org ([198.145.64.141]:55792 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935788AbZLQEFB (ORCPT ); Wed, 16 Dec 2009 23:05:01 -0500 X-Mailbox-Line: From gregkh@mini.kroah.org Wed Dec 16 19:56:56 2009 Message-Id: <20091217035655.965379342@mini.kroah.org> User-Agent: quilt/0.48-1 Date: Wed, 16 Dec 2009 19:56:37 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Mikulas Patocka , Alasdair G Kergon Subject: [100/151] dm snapshot: only take lock for statustype info not table In-Reply-To: <20091217040208.GA26571@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-stable review patch. If anyone has any objections, please let us know. ------------------ From: Mikulas Patocka commit 94e76572b5dd37b1f0f4b3742ee8a565daead932 upstream. Take snapshot lock only for STATUSTYPE_INFO, not STATUSTYPE_TABLE. Commit 4c6fff445d7aa753957856278d4d93bcad6e2c14 (dm-snapshot-lock-snapshot-while-supplying-status.patch) introduced this use of the lock, but userspace applications using libdevmapper have been found to request STATUSTYPE_TABLE while the device is suspended and the lock is already held, leading to deadlock. Since the lock is not necessary in this case, don't try to take it. Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-snap.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -1152,10 +1152,11 @@ static int snapshot_status(struct dm_tar unsigned sz = 0; struct dm_snapshot *snap = ti->private; - down_write(&snap->lock); - switch (type) { case STATUSTYPE_INFO: + + down_write(&snap->lock); + if (!snap->valid) DMEMIT("Invalid"); else { @@ -1171,6 +1172,9 @@ static int snapshot_status(struct dm_tar else DMEMIT("Unknown"); } + + up_write(&snap->lock); + break; case STATUSTYPE_TABLE: @@ -1185,8 +1189,6 @@ static int snapshot_status(struct dm_tar break; } - up_write(&snap->lock); - return 0; }