From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755561Ab0FPH5b (ORCPT ); Wed, 16 Jun 2010 03:57:31 -0400 Received: from cantor2.suse.de ([195.135.220.15]:39543 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753101Ab0FPH5a (ORCPT ); Wed, 16 Jun 2010 03:57:30 -0400 Date: Wed, 16 Jun 2010 17:57:23 +1000 From: Nick Piggin To: Rik van Riel Cc: Christoph Hellwig , Andrea Arcangeli , Mel Gorman , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Chris Mason Subject: Re: [RFC PATCH 0/6] Do not call ->writepage[s] from direct reclaim and use a_ops->writepages() where possible Message-ID: <20100616075723.GT6138@laptop> References: <20100615141122.GA27893@infradead.org> <20100615142219.GE28052@random.random> <20100615144342.GA3339@infradead.org> <20100615150850.GF28052@random.random> <20100615152526.GA3468@infradead.org> <20100615154516.GG28052@random.random> <20100615162600.GA9910@infradead.org> <4C17AF2D.2060904@redhat.com> <20100615165423.GA16868@infradead.org> <4C17D0C5.9030203@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C17D0C5.9030203@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 15, 2010 at 03:13:09PM -0400, Rik van Riel wrote: > On 06/15/2010 12:54 PM, Christoph Hellwig wrote: > >On Tue, Jun 15, 2010 at 12:49:49PM -0400, Rik van Riel wrote: > >>This is already in a filesystem. Why does ->writepage get > >>called a second time? Shouldn't this have a gfp_mask > >>without __GFP_FS set? > > > >Why would it? GFP_NOFS is not for all filesystem code, but only for > >code where we can't re-enter the filesystem due to deadlock potential. > > Why? How about because you know the stack is not big enough > to have the XFS call path on it twice? :) > > Isn't the whole purpose of this patch series to prevent writepage > from being called by the VM, when invoked from a deep callstack > like xfs writepage? > > That sounds a lot like simply wanting to not have GFP_FS... buffered write path uses __GFP_FS by design because huge amounts of (dirty) memory can be allocated in doing pagecache writes. If would be nasty if that was not allowed to wait for filesystem activity. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [RFC PATCH 0/6] Do not call ->writepage[s] from direct reclaim and use a_ops->writepages() where possible Date: Wed, 16 Jun 2010 17:57:23 +1000 Message-ID: <20100616075723.GT6138@laptop> References: <20100615141122.GA27893@infradead.org> <20100615142219.GE28052@random.random> <20100615144342.GA3339@infradead.org> <20100615150850.GF28052@random.random> <20100615152526.GA3468@infradead.org> <20100615154516.GG28052@random.random> <20100615162600.GA9910@infradead.org> <4C17AF2D.2060904@redhat.com> <20100615165423.GA16868@infradead.org> <4C17D0C5.9030203@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , Andrea Arcangeli , Mel Gorman , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Chris Mason To: Rik van Riel Return-path: Content-Disposition: inline In-Reply-To: <4C17D0C5.9030203@redhat.com> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Tue, Jun 15, 2010 at 03:13:09PM -0400, Rik van Riel wrote: > On 06/15/2010 12:54 PM, Christoph Hellwig wrote: > >On Tue, Jun 15, 2010 at 12:49:49PM -0400, Rik van Riel wrote: > >>This is already in a filesystem. Why does ->writepage get > >>called a second time? Shouldn't this have a gfp_mask > >>without __GFP_FS set? > > > >Why would it? GFP_NOFS is not for all filesystem code, but only for > >code where we can't re-enter the filesystem due to deadlock potential. > > Why? How about because you know the stack is not big enough > to have the XFS call path on it twice? :) > > Isn't the whole purpose of this patch series to prevent writepage > from being called by the VM, when invoked from a deep callstack > like xfs writepage? > > That sounds a lot like simply wanting to not have GFP_FS... buffered write path uses __GFP_FS by design because huge amounts of (dirty) memory can be allocated in doing pagecache writes. If would be nasty if that was not allowed to wait for filesystem activity. -- 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