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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 D86D0C433B4 for ; Wed, 21 Apr 2021 08:43:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 65A4361437 for ; Wed, 21 Apr 2021 08:43:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 65A4361437 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D61256B0071; Wed, 21 Apr 2021 04:43:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D388B6B0072; Wed, 21 Apr 2021 04:43:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C00D26B0073; Wed, 21 Apr 2021 04:43:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0224.hostedemail.com [216.40.44.224]) by kanga.kvack.org (Postfix) with ESMTP id A89576B0071 for ; Wed, 21 Apr 2021 04:43:29 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 6747082499B9 for ; Wed, 21 Apr 2021 08:43:29 +0000 (UTC) X-FDA: 78055735338.18.767F7E6 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf28.hostedemail.com (Postfix) with ESMTP id 200282000247 for ; Wed, 21 Apr 2021 08:43:30 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1618994608; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qx4dGYz57xIKRcyBm8cNLa//VH6OP4QY62G9bSPSqbY=; b=vR1jIb+IgHGDVvD+K8RweleyuDGzDT/mMygFYy7nkeudoMFWAJVfU/v1E09OascrON5j3j Q3Wb53w8sKl5yVpWbnaVJZaCpEEyA6h00hpKvfXVnYxV5a++I10QGew/VTkFK7AVpqm+L0 357YNt97omyJtOgPqG4H7hMYOLn/zNk= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id DE8C8B151; Wed, 21 Apr 2021 08:43:27 +0000 (UTC) Date: Wed, 21 Apr 2021 10:43:26 +0200 From: Michal Hocko To: Oscar Salvador Cc: Muchun Song , Mike Kravetz , Andrew Morton , Linux Memory Management List , LKML , Naoya Horiguchi Subject: Re: [External] Re: [PATCH] mm: hugetlb: fix a race between memory-failure/soft_offline and gather_surplus_pages Message-ID: References: <20210421060259.67554-1-songmuchun@bytedance.com> <20210421082103.GE22456@linux> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210421082103.GE22456@linux> X-Rspamd-Queue-Id: 200282000247 X-Stat-Signature: boqak9ff9tcc44akeumd4up7jqg1onzm X-Rspamd-Server: rspam02 Received-SPF: none (suse.com>: No applicable sender policy available) receiver=imf28; identity=mailfrom; envelope-from=""; helo=mx2.suse.de; client-ip=195.135.220.15 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618994610-355631 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 Wed 21-04-21 10:21:03, Oscar Salvador wrote: > On Wed, Apr 21, 2021 at 04:15:00PM +0800, Muchun Song wrote: > > > The hwpoison side of this looks really suspicious to me. It shouldn't > > > really touch the reference count of hugetlb pages without being very > > > careful (and having hugetlb_lock held). What would happen if the > > > reference count was increased after the page has been enqueed into the > > > pool? This can just blow up later. > > > > If the page has been enqueued into the pool, then the page can be > > allocated to other users. The page reference count will be reset to > > 1 in the dequeue_huge_page_node_exact(). Then memory-failure > > will free the page because of put_page(). This is wrong. Because > > there is another user. > > Note that dequeue_huge_page_node_exact() will not hand over any pages > which are poisoned, so in this case it will not be allocated. I have to say I have missed the HWPoison check so the this particular scenario is not possible indeed. > But it is true that we might need hugetlb lock, this needs some more > thought. yes, nobody should be touching to the reference count of hugetlb pool pages out of the hugetlb proper. > I will have a look. Thanks! -- Michal Hocko SUSE Labs