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 37D5BC433EF for ; Tue, 16 Nov 2021 21:57:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 19452615E2 for ; Tue, 16 Nov 2021 21:57:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231663AbhKPWA0 (ORCPT ); Tue, 16 Nov 2021 17:00:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58506 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229593AbhKPWAT (ORCPT ); Tue, 16 Nov 2021 17:00:19 -0500 Received: from mail-pg1-x549.google.com (mail-pg1-x549.google.com [IPv6:2607:f8b0:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8547BC061570 for ; Tue, 16 Nov 2021 13:57:22 -0800 (PST) Received: by mail-pg1-x549.google.com with SMTP id k22-20020a635a56000000b002df9863aa74so190565pgm.19 for ; Tue, 16 Nov 2021 13:57:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=RcxO89LsZtHgdWSYVweaJQPcYAbZUnKnBWG821s8zas=; b=sadMJNIDL9S3tfFJIrrJR2oyw/Fpm76XFjUCAQxx5qAVWIfC1+8OULcZFMJktCxOlk tjU8MxNlVgGMBPq1Oc0bUjfB2bB7hK3Rg33hxLGdi0+HdDCir3/JiqMwjY16IK9oLj3L 5toksxo5EbqhHJHXksLvDXWhH8nj5han4FAR8DMJLIJqyUxKokkZfqavlMO97qvmhcb6 i5D0W/5LrZnSdelv0TJVhDNsBNPLITY6FhKwUpgthNfmATlnUZfLLqWESkX2LX+ypW/i z2ANTtjj5hLbZS9PJALUGqhUQgDxMzgEUYqmqUqDtAWjjDOn2ZB5sfPHVZFx0fRac1v7 m9Fw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=RcxO89LsZtHgdWSYVweaJQPcYAbZUnKnBWG821s8zas=; b=GzbaWPJiAN/jAykW3ff+UH6Lqd59WoPlMc4NAGrWReB8ZdREGriyPeVS/5+qmkOBol OmSaBN1LJDFUBbyfnhOxt2bmIbeKyFdfkJTO9ETmEDOLANexo+i94Bq4t83cDK4QTAOz f06Ks/s5RgM+phlpsBuJCThTysPerNn0T0xszq+VF4Mb/FbtcjaR7ufho0KdSS5ltSez XYwXu77erc5cD9LWiFXii+18it+IMV5aBaCqv6fMzcytoEXwe6x3QAouxUuoeqvX3ev0 fI3aBB09rAvpNgkh7ai1zOJJDJpYIw2ei+jR2lCUkP/QFMUydvAkZOudWeU49MVQY49H OJAw== X-Gm-Message-State: AOAM533czVJkW9HI//jQhY/fgxjr1Z5x+nvthDpAMs0uIQQDs8fX1mqX kKJAo7vGs1RQet55eBjQaAd84SrC1/s= X-Google-Smtp-Source: ABdhPJw97ZImSXy/35Rbj61WyaJeUIeljhV1L18+fR0M/gOLQuFIwGLtXq43ozIk7RQDTw8knKOeaXWo9zI= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:91d1:d198:1088:5801]) (user=surenb job=sendgmr) by 2002:a63:86c1:: with SMTP id x184mr1591868pgd.295.1637099841832; Tue, 16 Nov 2021 13:57:21 -0800 (PST) Date: Tue, 16 Nov 2021 13:57:15 -0800 In-Reply-To: <20211116215715.645231-1-surenb@google.com> Message-Id: <20211116215715.645231-2-surenb@google.com> Mime-Version: 1.0 References: <20211116215715.645231-1-surenb@google.com> X-Mailer: git-send-email 2.34.0.rc2.393.gf8c9666880-goog Subject: [PATCH 2/2] mm/oom_kill: allow process_mrelease to run under mmap_lock protection From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: mhocko@kernel.org, mhocko@suse.com, 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, surenb@google.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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") Signed-off-by: Suren Baghdasaryan --- 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; -- 2.34.0.rc1.387.gb447b232ab-goog