From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933097AbZKFWl0 (ORCPT ); Fri, 6 Nov 2009 17:41:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932344AbZKFWlW (ORCPT ); Fri, 6 Nov 2009 17:41:22 -0500 Received: from kroah.org ([198.145.64.141]:56742 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932308AbZKFWWh (ORCPT ); Fri, 6 Nov 2009 17:22:37 -0500 X-Mailbox-Line: From gregkh@mini.kroah.org Fri Nov 6 14:15:41 2009 Message-Id: <20091106221541.565594071@mini.kroah.org> User-Agent: quilt/0.48-1 Date: Fri, 06 Nov 2009 14:14:20 -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, Kiyoshi Ueda , Junichi Nomura , Alasdair G Kergon Subject: [22/99] dm: dec_pending needs locking to save error value References: <20091106221358.309857998@mini.kroah.org> Content-Disposition: inline; filename=dm-dec_pending-needs-locking-to-save-error-value.patch In-Reply-To: <20091106221850.GA15408@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.31-stable review patch. If anyone has any objections, please let us know. ------------------ From: Kiyoshi Ueda commit f88fb981183e71daf40bbd84bc8251bbf7b59e19 upstream. Multiple instances of dec_pending() can run concurrently so a lock is needed when it saves the first error code. I have never experienced actual problem without locking and just found this during code inspection while implementing the barrier support patch for request-based dm. This patch adds the locking. I've done compile, boot and basic I/O testings. Signed-off-by: Kiyoshi Ueda Signed-off-by: Jun'ichi Nomura Signed-off-by: Alasdair G Kergon Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -47,6 +47,7 @@ struct dm_io { atomic_t io_count; struct bio *bio; unsigned long start_time; + spinlock_t endio_lock; }; /* @@ -576,8 +577,12 @@ static void dec_pending(struct dm_io *io struct mapped_device *md = io->md; /* Push-back supersedes any I/O errors */ - if (error && !(io->error > 0 && __noflush_suspending(md))) - io->error = error; + if (unlikely(error)) { + spin_lock_irqsave(&io->endio_lock, flags); + if (!(io->error > 0 && __noflush_suspending(md))) + io->error = error; + spin_unlock_irqrestore(&io->endio_lock, flags); + } if (atomic_dec_and_test(&io->io_count)) { if (io->error == DM_ENDIO_REQUEUE) { @@ -1224,6 +1229,7 @@ static void __split_and_process_bio(stru atomic_set(&ci.io->io_count, 1); ci.io->bio = bio; ci.io->md = md; + spin_lock_init(&ci.io->endio_lock); ci.sector = bio->bi_sector; ci.sector_count = bio_sectors(bio); if (unlikely(bio_empty_barrier(bio)))