From: Theodore Ts'o Subject: Re: EXT4 panic at jbd2_journal_put_journal_head() in 3.9+ Date: Sun, 12 May 2013 23:36:55 -0400 Message-ID: <20130513033655.GE25996@thunk.org> References: <7032562.14371368411664268.JavaMail.weblogic@epml07> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: eunb.song@samsung.com, Dmitry Monakhov , "linux-ext4@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: Tony Luck Return-path: Received: from li9-11.members.linode.com ([67.18.176.11]:47882 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751929Ab3EMDhD (ORCPT ); Sun, 12 May 2013 23:37:03 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Sun, May 12, 2013 at 08:11:59PM -0700, Tony Luck wrote: > > My best guess as to why this commit causes problems is that there are places > where updates to individual fields in this structure used to be independent > because they were to whole words. Now we have bitfileds there are races > between access to different fields in the same word. Yeah, except we access the fields while holding a lock.... wait a minute. We're using bit_spinlocks().... and am I missing something? Where are the barrier statements to prevent the CPU or the compiler from reordering statements around bit_spin_lock()? But if that's the problem, I would have expected lots of other things to be broken. - Ted