From: Marco Stornelli <marco.stornelli@gmail.com>
To: liub.liubo@gmail.com
Cc: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH RFC] Btrfs: fix deadlock between sys_sync and freeze
Date: Tue, 14 Aug 2012 14:59:30 +0200 [thread overview]
Message-ID: <502A4BB2.6000404@gmail.com> (raw)
In-Reply-To: <1344920474-10014-1-git-send-email-liub.liubo@gmail.com>
Il 14/08/2012 07:01, liub.liubo@gmail.com ha scritto:
> From: Liu Bo <bo.li.liu@oracle.com>
>
> I found this while testing xfstests 068, the story is
>
> t1 t2
> sys_sync thaw_super
> iterate_supers
> down_read(sb->s_umount) down_write(sb->s_umount) --->wait for t1
> sync_fs (with wait mode)
> start_transaction
> sb_start_intwrite --------------------> wait for t2 to set s_writers.frozen to SB_UNFROZEN
>
> In this patch, I add an helper sb_start_intwrite_trylock() and use it before we
> start_transaction in sync_fs() with wait mode so that we won't hit the deadlock.
>
IMHO, we should avoid to call the sync operation on a frozen fs. The
freeze operation, indeed, already include a sync operation. According to
man page, no other operation should modify the fs after the freeze. So
for me the modification is inside sync_filesystem (and sync_one_sb).
Marco
next prev parent reply other threads:[~2012-08-14 13:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-14 5:01 [PATCH RFC] Btrfs: fix deadlock between sys_sync and freeze liub.liubo
2012-08-14 12:59 ` Marco Stornelli [this message]
2012-08-14 13:53 ` Liu Bo
2012-08-14 14:12 ` Marco Stornelli
2012-08-15 12:51 ` Liu Bo
2012-08-15 13:12 ` Jan Kara
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