From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 1C0E26B01B0 for ; Wed, 16 Jun 2010 03:57:31 -0400 (EDT) Date: Wed, 16 Jun 2010 17:57:23 +1000 From: Nick Piggin 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> Sender: owner-linux-mm@kvack.org 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 List-ID: 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