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 X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8E4A8C10F00 for ; Fri, 6 Mar 2020 12:52:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 417A12072D for ; Fri, 6 Mar 2020 12:52:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 417A12072D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9A6D96B0005; Fri, 6 Mar 2020 07:52:13 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9570F6B0006; Fri, 6 Mar 2020 07:52:13 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 86CD36B0007; Fri, 6 Mar 2020 07:52:13 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0094.hostedemail.com [216.40.44.94]) by kanga.kvack.org (Postfix) with ESMTP id 6CE696B0005 for ; Fri, 6 Mar 2020 07:52:13 -0500 (EST) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 0D06E181AC9B6 for ; Fri, 6 Mar 2020 12:52:13 +0000 (UTC) X-FDA: 76564925346.10.iron73_1352b98f50e55 X-HE-Tag: iron73_1352b98f50e55 X-Filterd-Recvd-Size: 3070 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf02.hostedemail.com (Postfix) with ESMTP for ; Fri, 6 Mar 2020 12:52:12 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 5C2F3B138; Fri, 6 Mar 2020 12:52:10 +0000 (UTC) Subject: Re: [PATCH v7 6/7] mm/madvise: employ mmget_still_valid for write lock To: Minchan Kim , Andrew Morton Cc: LKML , linux-mm , linux-api@vger.kernel.org, oleksandr@redhat.com, Suren Baghdasaryan , Tim Murray , Daniel Colascione , Sandeep Patil , Sonny Rao , Brian Geffon , Michal Hocko , Johannes Weiner , Shakeel Butt , John Dias , Joel Fernandes , Jann Horn , alexander.h.duyck@linux.intel.com, sj38.park@gmail.com References: <20200302193630.68771-1-minchan@kernel.org> <20200302193630.68771-7-minchan@kernel.org> From: Vlastimil Babka Message-ID: Date: Fri, 6 Mar 2020 13:52:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200302193630.68771-7-minchan@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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: On 3/2/20 8:36 PM, Minchan Kim wrote: > From: Oleksandr Natalenko > > Do the very same trick as we already do since 04f5866e41fb. KSM hints > will require locking mmap_sem for write since they modify vm_flags, so > for remote KSM hinting this additional check is needed. > > Reviewed-by: Suren Baghdasaryan > Signed-off-by: Oleksandr Natalenko > Signed-off-by: Minchan Kim > --- > mm/madvise.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/madvise.c b/mm/madvise.c > index e794367f681e..e77c6c1fad34 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -1118,6 +1118,8 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm, > if (write) { > if (down_write_killable(&mm->mmap_sem)) > return -EINTR; > + if (current->mm != mm && !mmget_still_valid(mm)) > + goto skip_mm; This will return 0, is that correct? Shoudln't there be a similar error e.g. as when finding the task by pid fails (-ESRCH ?), because IIUC the task here is going away and dumping the core? > } else { > down_read(&mm->mmap_sem); > } > @@ -1169,6 +1171,7 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm, > } > out: > blk_finish_plug(&plug); > +skip_mm: > if (write) > up_write(&mm->mmap_sem); > else >