linux-ext4 - Re: xfstests generic/130 hang with non-4k block size ext4 on 4.7-rc1 kernel

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Message-ID: <20160608125631.GA19589@quack2.suse.cz>
Date:	Wed, 8 Jun 2016 14:56:31 +0200
From:	Jan Kara <jack@...e.cz>
To:	Eryu Guan <guaneryu@...il.com>
Cc:	Jan Kara <jack@...e.cz>, Theodore Ts'o <tytso@....edu>,
	Eryu Guan <eguan@...hat.com>, linux-ext4@...r.kernel.org
Subject: Re: xfstests generic/130 hang with non-4k block size ext4 on 4.7-rc1
 kernel

On Fri 03-06-16 13:58:44, Jan Kara wrote:
> On Fri 03-06-16 18:16:12, Eryu Guan wrote:
> > On Thu, Jun 02, 2016 at 02:17:50PM +0200, Jan Kara wrote:
> > > 
> > > So I was trying but I could not reproduce the hang either. Can you find out
> > > which page is jbd2 thread waiting for and dump page->index, page->flags and
> > > also bh->b_state, bh->b_blocknr of all 4 buffer heads attached to it via
> > > page->private? Maybe that will shed some light...
> > 
> > I'm using crash on live system when the hang happens, so I got the page
> > address from "bt -f"
> > 
> >  #6 [ffff880212343b40] wait_on_page_bit at ffffffff8119009e
> >     ffff880212343b48: ffffea0002c23600 000000000000000d 
> >     ffff880212343b58: 0000000000000000 0000000000000000 
> >     ffff880212343b68: ffff880213251480 ffffffff810cd000 
> >     ffff880212343b78: ffff88021ff27218 ffff88021ff27218 
> >     ffff880212343b88: 00000000c1b4a75a ffff880212343c68 
> >     ffff880212343b98: ffffffff811901bf
> 
> Thanks for debugging! In the end I was able to reproduce the issue on my
> UML instance as well and I'm debugging what's going on.

Attached patch fixes the issue for me. I'll submit it once a full xfstests
run finishes for it (which may take a while as our server room is currently
moving to a different place).

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR

View attachment "0001-ext4-Fix-deadlock-during-page-writeback.patch" of type "text/x-patch" (2459 bytes)