From: Theodore Tso Subject: Re: [RFC PATCH] ext4: Use page_mkwrite vma_operations to get mmap write notification. Date: Wed, 5 Mar 2008 18:59:41 -0500 Message-ID: <20080305235941.GD18188@mit.edu> References: <1204634542-16599-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1204677951.3605.6.camel@localhost.localdomain> <20080305232927.GC18188@mit.edu> <1204760238.3713.4.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Aneesh Kumar K.V" , linux-ext4@vger.kernel.org To: Mingming Cao Return-path: Received: from BISCAYNE-ONE-STATION.MIT.EDU ([18.7.7.80]:61719 "EHLO biscayne-one-station.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753501AbYCEX74 (ORCPT ); Wed, 5 Mar 2008 18:59:56 -0500 Content-Disposition: inline In-Reply-To: <1204760238.3713.4.camel@localhost.localdomain> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, Mar 05, 2008 at 03:37:18PM -0800, Mingming Cao wrote: > On Wed, 2008-03-05 at 18:29 -0500, Theodore Tso wrote: > > On Tue, Mar 04, 2008 at 04:45:51PM -0800, Mingming Cao wrote: > > > > + /* FIXME!! should we take inode->i_mutex ? Currently we can't because > > > > + * it has a circular locking dependency with DIO. But migrate expect > > > > + * i_mutex to ensure no i_data changes > > > > Should I worry that we have something in the stable part of the patch > > queue with this FIXME!! comment? :-) > > > > I think this comment could be moved to the migration.c. We can't take > i_mutex on mapped IO path. The i_data_mutex is the lock that should > protect the i_data concurrent changes, which is currently mapped IO > used. The race with migration could be addressed in migration instead of > here. I propose we drop this comment for now. OK, but that still means we have a known bug in the migration code, which is in mainline.... - Ted