From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932554Ab1CEBBF (ORCPT ); Fri, 4 Mar 2011 20:01:05 -0500 Received: from kroah.org ([198.145.64.141]:50484 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932503Ab1CEBA7 (ORCPT ); Fri, 4 Mar 2011 20:00:59 -0500 X-Mailbox-Line: From gregkh@clark.kroah.org Fri Mar 4 16:56:40 2011 Message-Id: <20110305005640.831280368@clark.kroah.org> User-Agent: quilt/0.48-11.2 Date: Fri, 04 Mar 2011 16:56:09 -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, Petr Uzel , Arnd Bergmann , Jens Axboe Subject: [64/73] block: kill loop_mutex In-Reply-To: <20110305005720.GA16162@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.37-stable review patch. If anyone has any objections, please let us know. ------------------ From: Petr Uzel commit fd51469fb68b987032e46297e0a4fe9020063c20 upstream. Following steps lead to deadlock in kernel: dd if=/dev/zero of=img bs=512 count=1000 losetup -f img mkfs.ext2 /dev/loop0 mount -t ext2 -o loop /dev/loop0 mnt umount mnt/ Stacktrace: [] irq_exit+0x36/0x59 [] smp_apic_timer_interrupt+0x6b/0x75 [] apic_timer_interrupt+0x31/0x38 [] mutex_spin_on_owner+0x54/0x5b [] lo_release+0x12/0x67 [loop] [] __blkdev_put+0x7c/0x10c [] fput+0xd5/0x1aa [] loop_clr_fd+0x1a9/0x1b1 [loop] [] lo_release+0x39/0x67 [loop] [] __blkdev_put+0x7c/0x10c [] deactivate_locked_super+0x17/0x36 [] sys_umount+0x27e/0x2a5 [] sys_oldumount+0xb/0xe [] sysenter_do_call+0x12/0x26 [] 0xffffffff Regression since 2a48fc0ab24241755dc9, which introduced the private loop_mutex as part of the BKL removal process. As per [1], the mutex can be safely removed. [1] http://www.gossamer-threads.com/lists/linux/kernel/1341930 Addresses: https://bugzilla.novell.com/show_bug.cgi?id=669394 Addresses: https://bugzilla.kernel.org/show_bug.cgi?id=29172 Signed-off-by: Petr Uzel Reviewed-by: Nikanth Karthikesan Acked-by: Arnd Bergmann Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- drivers/block/loop.c | 5 ----- 1 file changed, 5 deletions(-) --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -78,7 +78,6 @@ #include -static DEFINE_MUTEX(loop_mutex); static LIST_HEAD(loop_devices); static DEFINE_MUTEX(loop_devices_mutex); @@ -1505,11 +1504,9 @@ static int lo_open(struct block_device * { struct loop_device *lo = bdev->bd_disk->private_data; - mutex_lock(&loop_mutex); mutex_lock(&lo->lo_ctl_mutex); lo->lo_refcnt++; mutex_unlock(&lo->lo_ctl_mutex); - mutex_unlock(&loop_mutex); return 0; } @@ -1519,7 +1516,6 @@ static int lo_release(struct gendisk *di struct loop_device *lo = disk->private_data; int err; - mutex_lock(&loop_mutex); mutex_lock(&lo->lo_ctl_mutex); if (--lo->lo_refcnt) @@ -1544,7 +1540,6 @@ static int lo_release(struct gendisk *di out: mutex_unlock(&lo->lo_ctl_mutex); out_unlocked: - mutex_unlock(&loop_mutex); return 0; }