Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754803AbcK1RTR (ORCPT ); Mon, 28 Nov 2016 12:19:17 -0500 Received: from mail-yb0-f196.google.com ([209.85.213.196]:34336 "EHLO mail-yb0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754278AbcK1RTK (ORCPT ); Mon, 28 Nov 2016 12:19:10 -0500 Date: Mon, 28 Nov 2016 12:19:07 -0500 From: Tejun Heo To: Vlastimil Babka Cc: Linus Torvalds , Jens Axboe , linux-mm , Michal Hocko , LKML , Joonsoo Kim , Marc MERLIN Subject: Re: [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations in blkcg Message-ID: <20161128171907.GA14754@htj.duckdns.org> References: <20161121154336.GD19750@merlins.org> <0d4939f3-869d-6fb8-0914-5f74172f8519@suse.cz> <20161121215639.GF13371@merlins.org> <20161121230332.GA3767@htj.duckdns.org> <7189b1f6-98c3-9a36-83c1-79f2ff4099af@suse.cz> <20161122164822.GA5459@htj.duckdns.org> <3e8eeadb-8dde-2313-f6e3-ef7763832104@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3e8eeadb-8dde-2313-f6e3-ef7763832104@suse.cz> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1075 Lines: 27 Hello, On Wed, Nov 23, 2016 at 09:50:12AM +0100, Vlastimil Babka wrote: > > You'd certainly _hope_ that atomic allocations either have fallbacks > > or are harmless if they fail, but I'd still rather see that > > __GFP_NOWARN just to make that very much explicit. > > A global change to GFP_NOWAIT would of course mean that we should audit its > users (there don't seem to be many), whether they are using it consciously > and should not rather be using GFP_ATOMIC. A while ago, I thought about something like, say, GFP_MAYBE which is combination of NOWAIT and NOWARN but couldn't really come up with scenarios where one would want to use NOWAIT w/o NOWARN. If an allocation is important enough to warn the user of its failure, it better be dipping into the atomic reserve pool; otherwise, it doesn't make sense to make noise. Maybe we can come up with a better name which signifies that this is likely to fail every now and then but I still think it'd be beneficial to make it quiet by default. Linus, do you still think NOWARN should be explicit? Thanks. -- tejun