From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx193.postini.com [74.125.245.193]) by kanga.kvack.org (Postfix) with SMTP id C97896B0005 for ; Tue, 9 Apr 2013 17:04:34 -0400 (EDT) Date: Tue, 9 Apr 2013 14:04:32 -0700 From: Andrew Morton Subject: Re: [PATCH v3] [RESEND] mm: Make snapshotting pages for stable writes a per-bio operation Message-Id: <20130409140432.cd69f999302a02caf73788fc@linux-foundation.org> In-Reply-To: <20130409180617.GB8907@blackbox.djwong.org> References: <20130409180617.GB8907@blackbox.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Darrick J. Wong" Cc: Jan Kara , Mel Gorman , Shuge , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org, Kevin , Theodore Ts'o , Jens Axboe , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org On Tue, 9 Apr 2013 11:06:17 -0700 "Darrick J. Wong" wrote: > + * Here we write back pagecache data that may be mmaped. Since > + * we cannot afford to clean the page and set PageWriteback > + * here due to lock ordering (page lock ranks above transaction > + * start), the data can change while IO is in flight. Tell the > + * block layer it should bounce the bio pages if stable data > + * during write is required. I think there are already ab/ba deadlocks between lock_page() and journal_start(). iirc one path was write(), I forget which was the other path. This was 10+ years ago and nobody else noticed and I didn't know how to fix it so I didn't tell anyone ;) It would be neat to be able to hook things like journal_start() into lockdep but I don't think that lockdep has easy provision for wiring oddball things into its mechanisms. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org