Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966197AbcCPFTT (ORCPT ); Wed, 16 Mar 2016 01:19:19 -0400 Received: from gum.cmpxchg.org ([85.214.110.215]:46578 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934569AbcCPFTO (ORCPT ); Wed, 16 Mar 2016 01:19:14 -0400 Date: Tue, 15 Mar 2016 22:18:48 -0700 From: Johannes Weiner To: Vladimir Davydov Cc: Michal Hocko , Andrew Morton , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH] mm: memcontrol: reclaim and OOM kill when shrinking memory.max below usage Message-ID: <20160316051848.GA11006@cmpxchg.org> References: <1457643015-8828-2-git-send-email-hannes@cmpxchg.org> <20160311081825.GC27701@dhcp22.suse.cz> <20160311091931.GK1946@esperanza> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160311091931.GK1946@esperanza> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1216 Lines: 34 On Fri, Mar 11, 2016 at 12:19:31PM +0300, Vladimir Davydov wrote: > On Fri, Mar 11, 2016 at 09:18:25AM +0100, Michal Hocko wrote: > > On Thu 10-03-16 15:50:14, Johannes Weiner wrote: > ... > > > @@ -5037,9 +5040,36 @@ static ssize_t memory_max_write(struct kernfs_open_file *of, > > > if (err) > > > return err; > > > > > > - err = mem_cgroup_resize_limit(memcg, max); > > > - if (err) > > > - return err; > > > + xchg(&memcg->memory.limit, max); > > > + > > > + for (;;) { > > > + unsigned long nr_pages = page_counter_read(&memcg->memory); > > > + > > > + if (nr_pages <= max) > > > + break; > > > + > > > + if (signal_pending(current)) { > > > > Didn't you want fatal_signal_pending here? At least the changelog > > suggests that. > > I suppose the user might want to interrupt the write by hitting CTRL-C. Yeah. This is the same thing we do for the current limit setting loop. > Come to think of it, shouldn't we restore the old limit and return EBUSY > if we failed to reclaim enough memory? I suspect it's very rare that it would fail. But even in that case it's probably better to at least not allow new charges past what the user requested, even if we can't push the level back far enough.