From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id C99466B0003 for ; Wed, 31 Jan 2018 18:40:34 -0500 (EST) Received: by mail-pg0-f70.google.com with SMTP id m3so12197858pgd.20 for ; Wed, 31 Jan 2018 15:40:34 -0800 (PST) Received: from ipmail06.adl6.internode.on.net (ipmail06.adl6.internode.on.net. [150.101.137.145]) by mx.google.com with ESMTP id p129si320197pga.134.2018.01.31.15.40.32 for ; Wed, 31 Jan 2018 15:40:33 -0800 (PST) Date: Thu, 1 Feb 2018 10:41:26 +1100 From: Dave Chinner Subject: Re: [LSF/MM TOPIC] few MM topics Message-ID: <20180131234126.oobqdp6ibcayduu3@destitution> References: <20180124092649.GC21134@dhcp22.suse.cz> <20180131192104.GD4841@magnolia> <20180131202438.GA21609@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180131202438.GA21609@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: "Darrick J. Wong" , lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, Johannes Weiner , Rik van Riel On Wed, Jan 31, 2018 at 09:24:38PM +0100, Michal Hocko wrote: > On Wed 31-01-18 11:21:04, Darrick J. Wong wrote: > > On Wed, Jan 24, 2018 at 10:26:49AM +0100, Michal Hocko wrote: > [...] > > > - I would also love to talk to some FS people and convince them to move > > > away from GFP_NOFS in favor of the new scope API. I know this just > > > means to send patches but the existing code is quite complex and it > > > really requires somebody familiar with the specific FS to do that > > > work. > > > > Hm, are you talking about setting PF_MEMALLOC_NOFS instead of passing > > *_NOFS to allocation functions and whatnot? > > yes memalloc_nofs_{save,restore} > > > Right now XFS will set it > > on any thread which has a transaction open, but that doesn't help for > > fs operations that don't have transactions (e.g. reading metadata, > > opening files). I suppose we could just set the flag any time someone > > stumbles into the fs code from userspace, though you're right that seems > > daunting. > > I would really love to see the code to take the nofs scope > (memalloc_nofs_save) at the point where the FS "critical" section starts > (from the reclaim recursion POV). We already do that - the transaction context in XFS is the critical context, and we set PF_MEMALLOC_NOFS when we allocate a transaction handle and remove it when we commit the transaction. > This would both document the context > and also limit NOFS allocations to bare minumum. Yup, most of XFS already uses implicit GFP_NOFS allocation calls via the transaction context process flag manipulation. Cheers, Dave. -- Dave Chinner david@fromorbit.com -- 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