linux-kernel - Re: writeback: bad unlock balance detected in 3.5-rc1

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Date:	Sat, 9 Jun 2012 08:37:28 +0900
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Ted Ts'o <tytso@....edu>, Jan Kara <jack@...e.cz>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: writeback: bad unlock balance detected in 3.5-rc1

On Fri, Jun 08, 2012 at 04:28:40PM -0400, Theodore Ts'o wrote:
> On Fri, Jun 08, 2012 at 05:07:36PM +0200, Jan Kara wrote:
> >   Argh, I wonder how come I didn't hit this. Does attached patch fix the
> > problem?
> 
> Just to confirm (although there was little doubt), I've built a kernel
> with this patch and it fixes the lockdep complaint.

Great, thank you!

Here is the updated changelog:

        writeback: Fix lock imbalance in writeback_sb_inodes()

        Fix bug introduced by 169ebd90.  We have to have wb_list_lock locked when
        restarting writeback loop after having waited for inode writeback.

        Bug description by Ted Tso:
          
          I can reproduce this fairly easily by using ext4 w/o a journal, running
          under KVM with 1024megs memory, with fsstress (xfstests #13):
          
          [   45.153294] =====================================
          [   45.154784] [ BUG: bad unlock balance detected! ]
          [   45.155591] 3.5.0-rc1-00002-gb22b1f1 #124 Not tainted
          [   45.155591] -------------------------------------
          [   45.155591] flush-254:16/2499 is trying to release lock (&(&wb->list_lock)->rlock) at:
          [   45.155591] [<c022c3da>] writeback_sb_inodes+0x160/0x327
          [   45.155591] but there are no more locks to release!

        Reported-by: Theodore Ts'o <tytso@....edu>
        Tested-by: Theodore Ts'o <tytso@....edu>
        Signed-off-by: Jan Kara <jack@...e.cz>
        Signed-off-by: Fengguang Wu <fengguang.wu@...el.com>

Thanks,
Fengguang
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