From: Dave Chinner <david@fromorbit.com>
To: Miao Xie <miaox@cn.fujitsu.com>
Cc: Chris Mason <chris.mason@oracle.com>,
viro <viro@zeniv.linux.org.uk>,
Linux Btrfs <linux-btrfs@vger.kernel.org>,
Linux Fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [RFC PATCH 2/2] Btrfs: fix deadlock on umount by umount_prepare interface
Date: Thu, 22 Mar 2012 15:39:36 +1100 [thread overview]
Message-ID: <20120322043936.GD3592@dastard> (raw)
In-Reply-To: <4F6A98CD.5090701@cn.fujitsu.com>
On Thu, Mar 22, 2012 at 11:13:17AM +0800, Miao Xie wrote:
> The reason the deadlock is that:
> Task Btrfs-cleaner
> umount()
> down_write(&s->s_umount)
> close_ctree()
> wait for the end of
> btrfs-cleaner
> start_transaction
> reserve space
> shrink_delalloc()
> writeback_inodes_sb_nr_if_idle()
> down_read(&sb->s_umount)
> So, the deadlock has happened.
Every time a deadlock involving writeback_inodes_sb...if_idle()
comes up, I give the same response. If the s_umount is write locked,
then the sb is not idle. IOWs, writeback_inodes_sb...if_idle()
should be doing down_read_trylock(), not down_read().
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2012-03-22 4:39 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-22 3:13 [RFC PATCH 2/2] Btrfs: fix deadlock on umount by umount_prepare interface Miao Xie
2012-03-22 4:39 ` Dave Chinner [this message]
2012-03-22 5:25 ` Miao Xie
2012-03-22 6:29 ` Dave Chinner
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