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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 145A6C433EF for ; Wed, 24 Nov 2021 23:59:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344289AbhKYAC0 (ORCPT ); Wed, 24 Nov 2021 19:02:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37938 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244870AbhKYACW (ORCPT ); Wed, 24 Nov 2021 19:02:22 -0500 Received: from mail-pf1-x44a.google.com (mail-pf1-x44a.google.com [IPv6:2607:f8b0:4864:20::44a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F794C061574 for ; Wed, 24 Nov 2021 15:59:12 -0800 (PST) Received: by mail-pf1-x44a.google.com with SMTP id c131-20020a621c89000000b004a343484969so2416933pfc.3 for ; Wed, 24 Nov 2021 15:59:12 -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=t7FdhzxvsZEaT0mOxjq3xyS9+1eldYre4hZBRnUvw50=; b=XeEU3PAGavc7VvBMypFLluu+ieBo76Q+zJ39ZTNFi6b5dJ5s8y79SbwbGCFPHJO7qe iUp9PDs2knNmYnC0Rc49wtUu66reODZVX0XweepNO8ec4ZnpA4ngpThkRkm04eApGFn4 BcGW+53Z0vi0ABD0ZY6p8765F2G7V9az6dCLJZ+D9Yy4Y+jIgg4pZYfm5bFDRpBifUwA mUGjXZEgG1Q7Gcd51ADbYPrOlAPUxSIvInm8OYi+IUVSBeXfyoJW7Axf9GkQE7J9wU7z ZL4c/YNyXnf4IhCqXGXOYin80aaul8joX00TnEhQmKZcIGWs8cseJPdCKDZvi0TD4bXQ /zsw== 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=t7FdhzxvsZEaT0mOxjq3xyS9+1eldYre4hZBRnUvw50=; b=0wDFBmmof6xaq36p9OQuRIZ0usUgFTVAR6K2ahA7kB4CrUSS+KGe7kInWnK6x28w80 3LYFMu1lk/warBautHohYEOhi2SIjE2iciYGBM8ZxPze1vLOC3XAZ0o12xg9jY0HacOo +E85hf8vd3s+ZME5ZyNiH5/gH03xG+XZgi1zgxM83Z+jhfnTGwERJUAqQSeoVtpGVjD3 /IT7XNmMhEtcUA4cD1sH51gPGEZiCmX6/WM55h+uCUqZnQmzs7sq12VemSdJl83N6flX SRc+8XWm0Z7q7YxGmIxQliCMQM5SpteZ4Rs1D6IYd7motLxOcueYB0RAeKb4t9E4sWmU MDRw== X-Gm-Message-State: AOAM532o9k2Fsfm1EWAVFmcyRY4GvVak6pGT4KV7GCx1nMp9WHbvToLo Y86uF0oVxavbjdDRg8dmMx0Orvs2hUU= X-Google-Smtp-Source: ABdhPJy11r8Cp9qEV7E2WGPyNi2vSpjmD9e1BGWfSYrrDL2dDwJV+yrk5EsdtC2BNTHjzJgHlKsupPO6pi4= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:e6ae:ce8f:3b61:8f18]) (user=surenb job=sendgmr) by 2002:a63:150c:: with SMTP id v12mr13231871pgl.442.1637798351805; Wed, 24 Nov 2021 15:59:11 -0800 (PST) Date: Wed, 24 Nov 2021 15:59:06 -0800 In-Reply-To: <20211124235906.14437-1-surenb@google.com> Message-Id: <20211124235906.14437-2-surenb@google.com> Mime-Version: 1.0 References: <20211124235906.14437-1-surenb@google.com> X-Mailer: git-send-email 2.34.0.rc2.393.gf8c9666880-goog Subject: [PATCH v2 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.rc2.393.gf8c9666880-goog