From patchwork Wed Nov 24 23:59:06 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Suren Baghdasaryan X-Patchwork-Id: 12638133 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 BA8DDC433EF for ; Wed, 24 Nov 2021 23:59:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CDB6B6B007D; Wed, 24 Nov 2021 18:59:23 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C56326B007E; Wed, 24 Nov 2021 18:59:23 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AF73E6B0080; Wed, 24 Nov 2021 18:59:23 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0231.hostedemail.com [216.40.44.231]) by kanga.kvack.org (Postfix) with ESMTP id A1B406B007D 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=t7FdhzxvsZEaT0mOxjq3xyS9+1eldYre4hZBRnUvw50=; b=4AAl7TL468mzFnwZ4RJM9Amf6Y1sOsJwLiaxrS5epZueGp2Bw6gEcfkq7PeSTYBOBF iD5u5eeLAsS74Md2HX3CJtykngabRtbx8EClPKp+EHSF+ppzLAPrFUC8UF3q8oGzdcZx Qmh6CsX+OyhmPodl33aooCiUEsPU0IHi2Z2ZkwurZyUcrkC+QYqfiAS090Il0B2PjJlR 1MKbkv+gZ4MKMatBMPGdOs8NWGSD+UN2yU1OljAdfgfDNHJfzao3hKX0tD9EfYIXJgJv sSrv3/ACmfiu4qcN/KdZXKHO82rg0a3fhWzhIMTlsEslTPuYTi4Ncc6lrZTfORJJiQGL +wQA== X-Gm-Message-State: AOAM532pIdafvRqsmptQFTrPLWUazuLpW2FGyumRdZkcjA7hdKSuHo65 D30ZJ16ZwcRh0w+zYahjVVGGtCj+MPM= 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 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: D388E300044A X-Stat-Signature: zr8f67wnz47bkuu7mjxyfinunedbdygy Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=XeEU3PAG; spf=pass (imf03.hostedemail.com: domain of 3z9GeYQYKCAIuwtgpdiqqing.eqonkpwz-oomxcem.qti@flex--surenb.bounces.google.com designates 209.85.210.201 as permitted sender) smtp.mailfrom=3z9GeYQYKCAIuwtgpdiqqing.eqonkpwz-oomxcem.qti@flex--surenb.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1637798349-316282 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;