From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:45510 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751195AbdLINcW (ORCPT ); Sat, 9 Dec 2017 08:32:22 -0500 Subject: Re: [PATCH] Btrfs: raid56: fix race between merge_bio and rbio_orig_end_io To: Liu Bo , linux-btrfs@vger.kernel.org References: <20171208230235.30636-1-bo.li.liu@oracle.com> From: Nikolay Borisov Message-ID: <233e3f98-5f56-c2b8-1aa3-32ea360fe577@suse.com> Date: Sat, 9 Dec 2017 15:32:18 +0200 MIME-Version: 1.0 In-Reply-To: <20171208230235.30636-1-bo.li.liu@oracle.com> Content-Type: text/plain; charset=utf-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 9.12.2017 01:02, Liu Bo wrote: > We're not allowed to take any new bios to rbio->bio_list in > rbio_orig_end_io(), otherwise we may get merged with more bios and > rbio->bio_list is not empty. > > This should only happens in error-out cases, the normal path of > recover and full stripe write have already set RBIO_RMW_LOCKED_BIT to > disable merge before doing IO. > > Reported-by: Jérôme Carretero > Signed-off-by: Liu Bo > --- > fs/btrfs/raid56.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c > index 5aa9d22..127c782 100644 > --- a/fs/btrfs/raid56.c > +++ b/fs/btrfs/raid56.c > @@ -859,12 +859,23 @@ static void free_raid_bio(struct btrfs_raid_bio *rbio) > */ > static void rbio_orig_end_io(struct btrfs_raid_bio *rbio, blk_status_t err) > { > - struct bio *cur = bio_list_get(&rbio->bio_list); > + struct bio *cur; > struct bio *next; > > + /* > + * We're not allowed to take any new bios to rbio->bio_list > + * from now on, otherwise we may get merged with more bios and > + * rbio->bio_list is not empty. > + */ > + spin_lock(&rbio->bio_list_lock); > + set_bit(RBIO_RMW_LOCKED_BIT, &rbio->flags); > + spin_unlock(&rbio->bio_list_lock); do we really need the spinlock, bit operations are atomic? > + > if (rbio->generic_bio_cnt) > btrfs_bio_counter_sub(rbio->fs_info, rbio->generic_bio_cnt); > > + cur = bio_list_get(&rbio->bio_list); > + > free_raid_bio(rbio); > > while (cur) { >