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 8C034C433EF for ; Thu, 9 Dec 2021 19:13:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230429AbhLITRK (ORCPT ); Thu, 9 Dec 2021 14:17:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46866 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230399AbhLITRJ (ORCPT ); Thu, 9 Dec 2021 14:17:09 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77903C061746 for ; Thu, 9 Dec 2021 11:13:35 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id g25-20020a25b119000000b005c5e52a0574so12240946ybj.5 for ; Thu, 09 Dec 2021 11:13:35 -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=TGD1yEXRZ0MgwllUhVvIa/i7an9uYE2v1PNT6apFGJI=; b=SUl8NhsoAJRdz0LQdtW1eB9Xs5Y8fHH763/4wqAqzmTa0ilCvW8QVUyzOZYkmIvsc8 R9fE+KAUto0xhgURFJ1S7aQztTkTD6YLsl/Sn88yMKSGsMu2m1IsZsv8xMBP8oeEqIzh XrbU5YGJPTbrlZQ1ky1NDM9uTsXmBpgDmwlo+Nb+DgkYyt8tlDlY3EuwLW/lTbbZBCGZ Effb9bBThbMtFYR79CQ99L7ibUrgjyGl4W62Oq2ZJmUcDYqxW7+sTpZIR3qbIOTzHrFB 9xvNqsWwcAv1NC0OO+MOTjmHvnP2iHaUoS9ayqgK6ilvCDnPMH0WbCujZtt7m2LkCKjU kK2g== 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=TGD1yEXRZ0MgwllUhVvIa/i7an9uYE2v1PNT6apFGJI=; b=m6CBkwEpc+rBKHF6ZfAYVglEmQ5yLvKsFBKCYbvqiZFSiCzTGd9jyd2jkbXwoTuuJR S29TbWAyslqoAYXtKpgeBEV/evVjBcW6EhnEM1MK4VQ8kIManSv3gDVVsxsbxvS7rhN6 uauvpnrcBMHJ7hK/pwNkLsrYOHgfazOkBtbpnKMUjfF2orFEfm+WX1IIRFv1kHRXYlIP rojYAtPOQt3ZXhwy7Iwr1X+iQYvNQjzDTxfcduWcOqAU1hzPB6CoyOKN4KETtIeA2/rm GlZX0HFSpUoqDg1/MLNp50aNWsZCAgj2wRx81uMb7ODhcfqHzHDntyBQb68YbFSrgA2W 5Afg== X-Gm-Message-State: AOAM5320X33V2i7bdumcixRtyYvw6527J8wfzXaXpyoQoaBC6PsiCoxi EhIsboqfLE07pO8Sv5RLIuj7cnwLDzs= X-Google-Smtp-Source: ABdhPJzI6MKgxdWBOrBRoG1MLD+oFx/sRDSe7QZtGI0W5qh4PkIQfOOtUwGmoWPwmy/8YdVZhrcexmtxZp8= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:8b23:8fcc:c6e4:3a65]) (user=surenb job=sendgmr) by 2002:a25:d16:: with SMTP id 22mr8607169ybn.51.1639077214712; Thu, 09 Dec 2021 11:13:34 -0800 (PST) Date: Thu, 9 Dec 2021 11:13:25 -0800 In-Reply-To: <20211209191325.3069345-1-surenb@google.com> Message-Id: <20211209191325.3069345-3-surenb@google.com> Mime-Version: 1.0 References: <20211209191325.3069345-1-surenb@google.com> X-Mailer: git-send-email 2.34.1.173.g76aa8bc2d0-goog Subject: [PATCH v5 3/3] 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. Signed-off-by: Suren Baghdasaryan Acked-by: Michal Hocko --- changes in v5 - Removed Fixes: tag, per Michal Hocko - Added Acked-by's 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; -- 2.34.1.173.g76aa8bc2d0-goog