Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751663Ab3EMNSP (ORCPT ); Mon, 13 May 2013 09:18:15 -0400 Received: from cantor2.suse.de ([195.135.220.15]:44397 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750991Ab3EMNSN (ORCPT ); Mon, 13 May 2013 09:18:13 -0400 Date: Mon, 13 May 2013 15:18:09 +0200 From: Jan Kara To: EUNBONG SONG Cc: "Theodore Ts'o" , Dmitry Monakhov , Jan Kara , "linux-ext4@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-xfs@vger.kernel.org" , Dave Chinner Subject: Re: Re: Re: EXT4 regression caused 4eec7 Message-ID: <20130513131809.GG400@quack.suse.cz> References: <31302271.2821368363898561.JavaMail.weblogic@epml17> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <31302271.2821368363898561.JavaMail.weblogic@epml17> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2787 Lines: 79 On Sun 12-05-13 13:04:59, EUNBONG SONG wrote: > > > >> Since at this point it's safer to rollback the change and we can > >> investigate more deeply how to fix it correctly for the next > >> development cycle, this is the patch which I'm testing. > > >> - Ted > > > Hello, I've tested with your patch. But the same problem was reproduced. > > Currently, I'm trying to git bisect. If i done git bisect, i will let you know. > > Hi, I've done git bisect. and panic at jbd2_journal_put_journal_head() is caused by > ae4647fb7654676fc44a97e86eb35f9f06b99f66: "jbd2: reduce journal_head size." > I write just code patch which revert ae4647fb7654676fc44a97e86eb35f9f06b99f66 because > I don't know the root cause. This is really strange. I've verified the code and all the places modifying b_jlist or b_modified are holding bh_state lock so we should be safe... Hum, but I remember I was debugging similar problems with bit fields in btrfs on ia64 as well (see http://lwn.net/Articles/478657/). So I think what has happened is that your compiler compiled bitfield access as 64-bit and updates to b_jcount and b_jlist / b_modified crashed into one another. I didn't hit it because my compiler was not so "clever". Grumble. In this case I think bitfields are not worth the trouble with gcc. It's a pitty we have to spend additional 8 bytes for every journal_head but we'll survive... I'll send Ted a partial revert and add a comment so that we won't repeat this mistake in future. Honza > Signed-off-by: Eunbong Song > --- > include/linux/journal-head.h | 11 +++++++++-- > 1 files changed, 9 insertions(+), 2 deletions(-) > > diff --git a/include/linux/journal-head.h b/include/linux/journal-head.h > index 13a3da2..c18b46f 100644 > --- a/include/linux/journal-head.h > +++ b/include/linux/journal-head.h > @@ -31,14 +31,21 @@ struct journal_head { > /* > * Journalling list for this buffer [jbd_lock_bh_state()] > */ > - unsigned b_jlist:4; > + unsigned b_jlist; > > /* > * This flag signals the buffer has been modified by > * the currently running transaction > * [jbd_lock_bh_state()] > */ > - unsigned b_modified:1; > + unsigned b_modified; > + > + /* > + * This feild tracks the last transaction id in which this buffer > + * has been cowed > + * [jbd_lock_bh_state()] > + */ > + tid_t b_cow_tid; > > /* > * Copy of the buffer data frozen for writing to the log. > -- > 1.7.0.4 > > > Thanks. -- Jan Kara SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/