Return-Path: linux-nfs-owner@vger.kernel.org Received: from ipmail06.adl6.internode.on.net ([150.101.137.145]:47901 "EHLO ipmail06.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752428AbaDPGbb (ORCPT ); Wed, 16 Apr 2014 02:31:31 -0400 Date: Wed, 16 Apr 2014 16:31:29 +1000 From: Dave Chinner To: NeilBrown Cc: linux-mm@kvack.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, xfs@oss.sgi.com Subject: Re: [PATCH 09/19] XFS: ensure xfs_file_*_read cannot deadlock in memory allocation. Message-ID: <20140416063129.GI15995@dastard> References: <20140416033623.10604.69237.stgit@notabene.brown> <20140416040336.10604.90380.stgit@notabene.brown> <20140416060459.GE15995@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20140416060459.GE15995@dastard> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Wed, Apr 16, 2014 at 04:04:59PM +1000, Dave Chinner wrote: > On Wed, Apr 16, 2014 at 02:03:36PM +1000, NeilBrown wrote: > > xfs_file_*_read holds an inode lock while calling a generic 'read' > > function. These functions perform read-ahead and are quite likely to > > allocate memory. > > Yes, that's what reading data from disk requires. > > > So set PF_FSTRANS to ensure they avoid __GFP_FS and so don't recurse > > into a filesystem to free memory. > > We already have that protection via the Oops, stray paste. Ignore that comment. -Dave. -- Dave Chinner david@fromorbit.com