Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752648AbdCBM0C (ORCPT ); Thu, 2 Mar 2017 07:26:02 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46712 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752442AbdCBMZy (ORCPT ); Thu, 2 Mar 2017 07:25:54 -0500 Date: Thu, 2 Mar 2017 07:24:27 -0500 From: Brian Foster To: Michal Hocko Cc: Tetsuo Handa , Xiong Zhou , Christoph Hellwig , linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: mm allocation failure and hang when running xfstests generic/269 on xfs Message-ID: <20170302122426.GA3213@bfoster.bfoster> References: <20170301044634.rgidgdqqiiwsmfpj@XZHOUW.usersys.redhat.com> <20170302003731.GB24593@infradead.org> <20170302051900.ct3xbesn2ku7ezll@XZHOUW.usersys.redhat.com> <42eb5d53-5ceb-a9ce-791a-9469af30810c@I-love.SAKURA.ne.jp> <20170302103520.GC1404@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170302103520.GC1404@dhcp22.suse.cz> User-Agent: Mutt/1.7.1 (2016-10-04) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 02 Mar 2017 12:24:28 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2567 Lines: 68 On Thu, Mar 02, 2017 at 11:35:20AM +0100, Michal Hocko wrote: > On Thu 02-03-17 19:04:48, Tetsuo Handa wrote: > [...] > > So, commit 5d17a73a2ebeb8d1("vmalloc: back off when the current task is > > killed") implemented __GFP_KILLABLE flag and automatically applied that > > flag. As a result, those who are not ready to fail upon SIGKILL are > > confused. ;-) > > You are right! The function is documented it might fail but the code > doesn't really allow that. This seems like a bug to me. What do you > think about the following? > --- > From d02cb0285d8ce3344fd64dc7e2912e9a04bef80d Mon Sep 17 00:00:00 2001 > From: Michal Hocko > Date: Thu, 2 Mar 2017 11:31:11 +0100 > Subject: [PATCH] xfs: allow kmem_zalloc_greedy to fail > > Even though kmem_zalloc_greedy is documented it might fail the current > code doesn't really implement this properly and loops on the smallest > allowed size for ever. This is a problem because vzalloc might fail > permanently. Since 5d17a73a2ebe ("vmalloc: back off when the current > task is killed") such a failure is much more probable than it used to > be. Fix this by bailing out if the minimum size request failed. > > This has been noticed by a hung generic/269 xfstest by Xiong Zhou. > > Reported-by: Xiong Zhou > Analyzed-by: Tetsuo Handa > Signed-off-by: Michal Hocko > --- > fs/xfs/kmem.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/xfs/kmem.c b/fs/xfs/kmem.c > index 339c696bbc01..ee95f5c6db45 100644 > --- a/fs/xfs/kmem.c > +++ b/fs/xfs/kmem.c > @@ -34,6 +34,8 @@ kmem_zalloc_greedy(size_t *size, size_t minsize, size_t maxsize) > size_t kmsize = maxsize; > > while (!(ptr = vzalloc(kmsize))) { > + if (kmsize == minsize) > + break; > if ((kmsize >>= 1) <= minsize) > kmsize = minsize; > } More consistent with the rest of the kmem code might be to accept a flags argument and do something like this based on KM_MAYFAIL. The one current caller looks like it would pass it, but I suppose we'd still need a mechanism to break out should a new caller not pass that flag. Would a fatal_signal_pending() check in the loop as well allow us to break out in the scenario that is reproduced here? Brian > -- > 2.11.0 > > -- > Michal Hocko > SUSE Labs > > -- > 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