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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id AFD20C433F5 for ; Thu, 9 Dec 2021 19:04:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 475C36B0073; Thu, 9 Dec 2021 14:04:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 3FE426B0074; Thu, 9 Dec 2021 14:04:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2789F6B0075; Thu, 9 Dec 2021 14:04:17 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0189.hostedemail.com [216.40.44.189]) by kanga.kvack.org (Postfix) with ESMTP id 19D2A6B0073 for ; Thu, 9 Dec 2021 14:04:17 -0500 (EST) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id CAFC18248076 for ; Thu, 9 Dec 2021 19:04:06 +0000 (UTC) X-FDA: 78899180892.25.032087C Received: from mail-yb1-f176.google.com (mail-yb1-f176.google.com [209.85.219.176]) by imf10.hostedemail.com (Postfix) with ESMTP id 097A7C000B for ; Thu, 9 Dec 2021 19:04:04 +0000 (UTC) Received: by mail-yb1-f176.google.com with SMTP id v64so15986022ybi.5 for ; Thu, 09 Dec 2021 11:03:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=two5tWS0eGFOwgvR2SUAW/v768W9Njq3kAUeHb+0A4Q=; b=Lwiup1KxwBFyc07FAmO5nKhY05sgszhLXDqINwnOoO1lFEc8Y/u1J2GTVuy7p2BUzj fT7ftz1+EmywUzrlqjNoQ4YaC+RxQccsjCtTUku1d1TRQBu7eFY2grZ1yx8vcnvkL/cy WeTQX/cJPLqK15ZZ+nJpwJhqBZmqQVTKeukO52X1SRIOBJvhuMvx7Opwk5c/YDnX6r/K EdsTJpzMYmheZLwlHenEVAhnZWW9B3Hbd3PB6Q/vCSuUnoPp8JJHTP8jswnti+t7me7d KtA3DZRrG86Ne4ieRt9tWFoM9/NH3IP4yFxA4BLt9M9A9PE17J9vMLRkJ3ZR+0RbIXfz /yPA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=two5tWS0eGFOwgvR2SUAW/v768W9Njq3kAUeHb+0A4Q=; b=q0atw4OU42bBzKJ/NEkdVk6/ssYArzjqSrIMeKCRNxNi3Sj8F0kYhVJwhyw/HG838N 0XSR6nj1PihhuerXmKWgnR3v9RNtbd2RIeS70qFva9Jj42WJvNz341WfQuC2whQRHzxi 7RTGi84PtRTFgHh2K9U/FacKZ6tY8lnx55xZRJ9MMZTr9Ddss++Bitu6dhI8AI8X9jMD sdu/P/nVjmz/0YcXc+1axUNm2nK39Je3zaRKzIT8GjjOKIV0DI6816v4I9mvq13pmKjU S4i6ir/VPDLOkQ5d1Rywc52YjSGJC8RKMTncvxiF8VWiz7F1f4X/IuopeU6mL/UDuZyA C8cA== X-Gm-Message-State: AOAM531OLZw1u2qA359/+OLkRfeVHDttmYP8mKGgAZptcemB5oSjHr0V xh+ZrBMASu3njLqNJXVsXqkw/1IjeIB1e5lKY8UjIg== X-Google-Smtp-Source: ABdhPJyecQYcqcyB3VigbPT/iwpHLSqnyETAoJb0G5MHHeKta4v9w6O15VNzF6yzZaUdu3RkQuz6hcW7XgA+lP52SNI= X-Received: by 2002:a25:a448:: with SMTP id f66mr8383450ybi.225.1639076637791; Thu, 09 Dec 2021 11:03:57 -0800 (PST) MIME-Version: 1.0 References: <20211208212211.2860249-1-surenb@google.com> <20211208212211.2860249-3-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Thu, 9 Dec 2021 11:03:46 -0800 Message-ID: Subject: Re: [PATCH v4 3/3] mm/oom_kill: allow process_mrelease to run under mmap_lock protection To: Michal Hocko Cc: akpm@linux-foundation.org, rientjes@google.com, willy@infradead.org, hannes@cmpxchg.org, guro@fb.com, riel@surriel.com, minchan@kernel.org, kirill@shutemov.name, aarcange@redhat.com, christian@brauner.io, hch@infradead.org, oleg@redhat.com, david@redhat.com, jannh@google.com, shakeelb@google.com, luto@kernel.org, christian.brauner@ubuntu.com, fweimer@redhat.com, jengelh@inai.de, timmurray@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 097A7C000B X-Stat-Signature: b88tuzmywgeiog4ugbgw8zrxydbba694 Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=Lwiup1Kx; spf=pass (imf10.hostedemail.com: domain of surenb@google.com designates 209.85.219.176 as permitted sender) smtp.mailfrom=surenb@google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1639076644-459511 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Dec 9, 2021 at 12:59 AM Michal Hocko wrote: > > On Wed 08-12-21 13:22:11, Suren Baghdasaryan wrote: > > With exit_mmap holding mmap_write_lock during free_pgtables call, > > process_mrelease does not need to elevate mm->mm_users in order to > > prevent exit_mmap from destrying pagetables while __oom_reap_task_mm > > is walking the VMA tree. The change prevents process_mrelease from > > calling the last mmput, which can lead to waiting for IO completion > > in exit_aio. > > > > Fixes: 337546e83fc7 ("mm/oom_kill.c: prevent a race between process_mrelease and exit_mmap") > > I am not sure I have brought this up already but I do not think Fixes > tag is a good fit. 337546e83fc7 is a correct way to handle the race. It > is just slightly less optimal than this fix. Will post v5 without it. Thanks! > > > Signed-off-by: Suren Baghdasaryan > > Acked-by: Michal Hocko > > Thanks! > > --- > > mm/oom_kill.c | 27 +++++++++++++++------------ > > 1 file changed, 15 insertions(+), 12 deletions(-) > > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > index 1ddabefcfb5a..67780386f478 100644 > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -1169,15 +1169,15 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags) > > goto put_task; > > } > > > > - if (mmget_not_zero(p->mm)) { > > - mm = p->mm; > > - if (task_will_free_mem(p)) > > - reap = true; > > - else { > > - /* Error only if the work has not been done already */ > > - if (!test_bit(MMF_OOM_SKIP, &mm->flags)) > > - ret = -EINVAL; > > - } > > + mm = p->mm; > > + mmgrab(mm); > > + > > + if (task_will_free_mem(p)) > > + reap = true; > > + else { > > + /* Error only if the work has not been done already */ > > + if (!test_bit(MMF_OOM_SKIP, &mm->flags)) > > + ret = -EINVAL; > > } > > task_unlock(p); > > > > @@ -1188,13 +1188,16 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags) > > ret = -EINTR; > > goto drop_mm; > > } > > - if (!__oom_reap_task_mm(mm)) > > + /* > > + * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure > > + * possible change in exit_mmap is seen > > + */ > > + if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm)) > > ret = -EAGAIN; > > mmap_read_unlock(mm); > > > > drop_mm: > > - if (mm) > > - mmput(mm); > > + mmdrop(mm); > > put_task: > > put_task_struct(task); > > return ret; > > -- > > 2.34.1.400.ga245620fadb-goog > > -- > Michal Hocko > SUSE Labs