From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rik van Riel 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 12:59:54 -0400 Message-ID: <4C19030A.4070406@redhat.com> 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> <20100616075723.GT6138@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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: Nick Piggin Return-path: In-Reply-To: <20100616075723.GT6138@laptop> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On 06/16/2010 03:57 AM, Nick Piggin wrote: > 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. __GFP_IO can wait for filesystem activity __GFP_FS can kick off new filesystem activity At least, that's how I remember it from when I last looked at that code in detail. Things may have changed subtly. -- All rights reversed -- 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