Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752403Ab3CREbV (ORCPT ); Mon, 18 Mar 2013 00:31:21 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33484 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751731Ab3CREa0 (ORCPT ); Mon, 18 Mar 2013 00:30:26 -0400 Message-Id: <20130318042151.896476449@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Mon, 18 Mar 2013 04:23:03 +0000 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, Guo Chao , Alexander Viro , "M. Hindess" , Nikanth Karthikesan , Jens Axboe Subject: [ 79/82] loopdev: fix a deadlock In-Reply-To: <20130318042144.234468645@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:d98f:da4e:f620:7bea X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2048 Lines: 67 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Guo Chao commit 5370019dc2d2c2ff90e95d181468071362934f3a upstream. bd_mutex and lo_ctl_mutex can be held in different order. Path #1: blkdev_open blkdev_get __blkdev_get (hold bd_mutex) lo_open (hold lo_ctl_mutex) Path #2: blkdev_ioctl lo_ioctl (hold lo_ctl_mutex) lo_set_capacity (hold bd_mutex) Lockdep does not report it, because path #2 actually holds a subclass of lo_ctl_mutex. This subclass seems creep into the code by mistake. The patch author actually just mentioned it in the changelog, see commit f028f3b2 ("loop: fix circular locking in loop_clr_fd()"), also see: http://marc.info/?l=linux-kernel&m=123806169129727&w=2 Path #2 hold bd_mutex to call bd_set_size(), I've protected it with i_mutex in a previous patch, so drop bd_mutex at this site. Signed-off-by: Guo Chao Cc: Alexander Viro Cc: Guo Chao Cc: M. Hindess Cc: Nikanth Karthikesan Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Jens Axboe Signed-off-by: Ben Hutchings --- drivers/block/loop.c | 2 -- 1 file changed, 2 deletions(-) --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1262,11 +1262,9 @@ static int loop_set_capacity(struct loop /* the width of sector_t may be narrow for bit-shift */ sz = sec; sz <<= 9; - mutex_lock(&bdev->bd_mutex); bd_set_size(bdev, sz); /* let user-space know about the new size */ kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE); - mutex_unlock(&bdev->bd_mutex); out: return err; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/