From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 59517C433EF for ; Mon, 27 Sep 2021 09:36:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3D78D60E8B for ; Mon, 27 Sep 2021 09:36:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233692AbhI0JiD (ORCPT ); Mon, 27 Sep 2021 05:38:03 -0400 Received: from relay.sw.ru ([185.231.240.75]:54652 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233587AbhI0Jh6 (ORCPT ); Mon, 27 Sep 2021 05:37:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Content-Type:MIME-Version:Date:Message-ID:From: Subject; bh=UuF6FHs19BNorLrl2iJ5nlzRqI12m41442Ub5BwC1yY=; b=cLaqobgNClIHOqPlH 4PvwKYnD6rUCdvka5AQkv2s1rFASROYIi0XMbECngjIx9Cdm9lUzuqO/DpoDma1WyY+fZO27ZPZCz yVMT5tKlP4GG049tOkT8nVxdakIoLjMIA4pjZZ1d+/PtrSfIjlruZdsBA9KuVUT0pB6QMF8a5RhM4 =; Received: from [10.93.0.56] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1mUn3Y-003bZI-4A; Mon, 27 Sep 2021 12:36:16 +0300 Subject: Re: [PATCH mm] vmalloc: back off when the current task is OOM-killed To: Michal Hocko Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Tetsuo Handa , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel@openvz.org References: From: Vasily Averin Message-ID: <508abe37-a044-7180-ac67-b4ce5e4cc149@virtuozzo.com> Date: Mon, 27 Sep 2021 12:36:15 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/24/21 10:55 AM, Michal Hocko wrote: > On Thu 23-09-21 09:49:57, Vasily Averin wrote: > [...] >> I'm agree that vmalloc callers should expect and handle single vnalloc failures. >> I think it is acceptable to enable fatal_signal_pending check to quickly >> detect such kind of iussues. >> However fatal_signal_pending check can cause serial vmalloc failures >> and I doubt it is acceptable. >> >> Rollback after failed vmalloc can call new vmalloc calls that will be failed too, >> even properly handled such serial failures can cause troubles. > > Could you be more specific? Also how would this be any different from > similar failures for an oom victim? Except that the later is less likely > so (as already mentioend) any potential bugs would be just lurking there > for a longer time. > >> Hypothetically, cancelled vmalloc called inside some filesystem's transaction >> forces its rollback, that in own turn it can call own vmalloc. > > Do you have any specific example? No, it was pure hypothetical assumption. I was thinking about it over the weekend, and decided that: a) such kind of issue (i.e. vmalloc call in rollback after failed vmalloc) is very unlikely b) if it still exists -- it must have own failback with kmalloc(NOFAIL) or just accept/ignore such failure and should not lead to critical failures. If this still happen -- ihis is a bug, we should detect and fix it ASAP. >> Should we perhaps interrupt the first vmalloc only? > > This doesn't make much sense to me TBH. It doesn't address the very > problem you are describing in the changelog. Last question: how do you think, should we perhaps, instead, detect such vmallocs (called in rollback after failed vmalloc) and generate a warnings, to prevent such kind of problems in future? Thank you, Vasily Averin From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vasily Averin Subject: Re: [PATCH mm] vmalloc: back off when the current task is OOM-killed Date: Mon, 27 Sep 2021 12:36:15 +0300 Message-ID: <508abe37-a044-7180-ac67-b4ce5e4cc149@virtuozzo.com> References: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Content-Type:MIME-Version:Date:Message-ID:From: Subject; bh=UuF6FHs19BNorLrl2iJ5nlzRqI12m41442Ub5BwC1yY=; b=cLaqobgNClIHOqPlH 4PvwKYnD6rUCdvka5AQkv2s1rFASROYIi0XMbECngjIx9Cdm9lUzuqO/DpoDma1WyY+fZO27ZPZCz yVMT5tKlP4GG049tOkT8nVxdakIoLjMIA4pjZZ1d+/PtrSfIjlruZdsBA9KuVUT0pB6QMF8a5RhM4 =; In-Reply-To: Content-Language: en-US List-ID: Content-Type: text/plain; charset="us-ascii" To: Michal Hocko Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Tetsuo Handa , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org On 9/24/21 10:55 AM, Michal Hocko wrote: > On Thu 23-09-21 09:49:57, Vasily Averin wrote: > [...] >> I'm agree that vmalloc callers should expect and handle single vnalloc failures. >> I think it is acceptable to enable fatal_signal_pending check to quickly >> detect such kind of iussues. >> However fatal_signal_pending check can cause serial vmalloc failures >> and I doubt it is acceptable. >> >> Rollback after failed vmalloc can call new vmalloc calls that will be failed too, >> even properly handled such serial failures can cause troubles. > > Could you be more specific? Also how would this be any different from > similar failures for an oom victim? Except that the later is less likely > so (as already mentioend) any potential bugs would be just lurking there > for a longer time. > >> Hypothetically, cancelled vmalloc called inside some filesystem's transaction >> forces its rollback, that in own turn it can call own vmalloc. > > Do you have any specific example? No, it was pure hypothetical assumption. I was thinking about it over the weekend, and decided that: a) such kind of issue (i.e. vmalloc call in rollback after failed vmalloc) is very unlikely b) if it still exists -- it must have own failback with kmalloc(NOFAIL) or just accept/ignore such failure and should not lead to critical failures. If this still happen -- ihis is a bug, we should detect and fix it ASAP. >> Should we perhaps interrupt the first vmalloc only? > > This doesn't make much sense to me TBH. It doesn't address the very > problem you are describing in the changelog. Last question: how do you think, should we perhaps, instead, detect such vmallocs (called in rollback after failed vmalloc) and generate a warnings, to prevent such kind of problems in future? Thank you, Vasily Averin