Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756371Ab3CRVIH (ORCPT ); Mon, 18 Mar 2013 17:08:07 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:45922 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756305Ab3CRVIE (ORCPT ); Mon, 18 Mar 2013 17:08:04 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Guo Chao , Alexander Viro , "M. Hindess" , Nikanth Karthikesan , Jens Axboe , Andrew Morton , Jeff Mahoney Subject: [ 34/48] loopdev: fix a deadlock Date: Mon, 18 Mar 2013 14:08:42 -0700 Message-Id: <20130318210812.653678837@linuxfoundation.org> X-Mailer: git-send-email 1.8.1.2.434.g9a6c84e.dirty In-Reply-To: <20130318210810.247845918@linuxfoundation.org> References: <20130318210810.247845918@linuxfoundation.org> User-Agent: quilt/0.60-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2101 Lines: 69 3.4-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 Acked-by: Jeff Mahoney Signed-off-by: Greg Kroah-Hartman --- drivers/block/loop.c | 2 -- 1 file changed, 2 deletions(-) --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1263,11 +1263,9 @@ 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/