From patchwork Tue Dec 7 21:50:31 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Suren Baghdasaryan X-Patchwork-Id: 12662805 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 68D84C433EF for ; Tue, 7 Dec 2021 21:51:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 89E386B0073; Tue, 7 Dec 2021 16:50:49 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8269D6B0074; Tue, 7 Dec 2021 16:50:49 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6C6E16B0075; Tue, 7 Dec 2021 16:50:49 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0195.hostedemail.com [216.40.44.195]) by kanga.kvack.org (Postfix) with ESMTP id 5F1F26B0073 for ; 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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=/LdRQnVKFEGyVFkXugJvOQFjhYmdmtnxJCMLa6KGAIY=; b=3XKdkxOOM7ZG4YB/wobQZLyh+03WD0OLu4SB4/+PEFQbm1ahjeTXItvMsYGhrJcDq9 Gnw7tXzYrXle/VlWsCdTxGVD0D53ictmkpOfr5yi0cP5Ysu+485hwCwE6wNKIQb7VrO0 xYWfhSVS2jfZAjCD+97JYFd7nwDHORSYG6WkaUD7fKkFY3MviOk13n+ha01t6MgssMpE RB/8kQidbA4nT5oEUvJuBEUteiICEvpH7qik7SqvTm0KTBB+Yu4PHAf0PpQBe74pi/DG 9gUVGw98LT9AnO9PW85G+7zOvysJacQf1jiHjWc/7EiipgV3NDN+owXnL4kpH2euFtp4 E/+w== X-Gm-Message-State: AOAM530WiRtbGkQf+bQ02sPFYq5QG6AoXPms+hiz+hWnE/Ox39mwvS1b a64QwakOoYd9Ife5burCi8Hq1bDZZhQ= X-Google-Smtp-Source: ABdhPJwczMrB/D5UxD3qYy1dxNZtBECINmekRXrVCSEVzUwTVEXKrH833TdiHRiC+ZHYFRov7+HszGzjwvw= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:c2df:fc7c:ed5e:6133]) (user=surenb job=sendgmr) by 2002:a25:308b:: with SMTP id w133mr54895368ybw.534.1638913838031; Tue, 07 Dec 2021 13:50:38 -0800 (PST) Date: Tue, 7 Dec 2021 13:50:31 -0800 In-Reply-To: <20211207215031.2251719-1-surenb@google.com> Message-Id: <20211207215031.2251719-2-surenb@google.com> Mime-Version: 1.0 References: <20211207215031.2251719-1-surenb@google.com> X-Mailer: git-send-email 2.34.1.400.ga245620fadb-goog Subject: [PATCH v3 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 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: C268940003 X-Stat-Signature: q38oof6a66mbckasrgsobe9hrhfb5ebs Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=TSJWEN5R; spf=pass (imf01.hostedemail.com: domain of 3LtevYQYKCK8hjgTcQVddVaT.RdbaXcjm-bbZkPRZ.dgV@flex--surenb.bounces.google.com designates 209.85.219.202 as permitted sender) smtp.mailfrom=3LtevYQYKCK8hjgTcQVddVaT.RdbaXcjm-bbZkPRZ.dgV@flex--surenb.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1638913838-821543 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: 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;