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[198.145.29.99]) by mx.google.com with ESMTPS id i11si10155225plb.416.2019.05.25.11.28.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 25 May 2019 11:28:52 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=c268qRQW; spf=pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from localhost.localdomain (c-73-223-200-170.hsd1.ca.comcast.net [73.223.200.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EDAB320863; Sat, 25 May 2019 18:28:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558808932; bh=o915ziI83Wq3DsJM16MhIJ37dE0MX7hNkXvLF1mxSSs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=c268qRQWAtxOlxLXaieeHQKVwLydKfkQ1kaOAyUmD8rZ5kPgeuW35L3VundqMz2ws TKpWRCTzZ8coWST9lgDMHXMzGATDQxarTquKm4ZuZQkbKIhDrGjeXU+rXigaTuPjPT LPC2G49gKq0gH2eeygnFjTHww2cX8TsGOwqjPKMc= Date: Sat, 25 May 2019 11:28:51 -0700 From: Andrew Morton To: zhong jiang Cc: , , , , , , , , Vlastimil Babka Subject: Re: [PATCH] mm/mempolicy: Fix an incorrect rebind node in mpol_rebind_nodemask Message-Id: <20190525112851.ee196bcbbc33bf9e0d869236@linux-foundation.org> In-Reply-To: <1558768043-23184-1-git-send-email-zhongjiang@huawei.com> References: <1558768043-23184-1-git-send-email-zhongjiang@huawei.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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: (Cc Vlastimil) On Sat, 25 May 2019 15:07:23 +0800 zhong jiang wrote: > We bind an different node to different vma, Unluckily, > it will bind different vma to same node by checking the /proc/pid/numa_maps. > Commit 213980c0f23b ("mm, mempolicy: simplify rebinding mempolicies when updating cpusets") > has introduced the issue. when we change memory policy by seting cpuset.mems, > A process will rebind the specified policy more than one times. > if the cpuset_mems_allowed is not equal to user specified nodes. hence the issue will trigger. > Maybe result in the out of memory which allocating memory from same node. > > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -345,7 +345,7 @@ static void mpol_rebind_nodemask(struct mempolicy *pol, const nodemask_t *nodes) > else { > nodes_remap(tmp, pol->v.nodes,pol->w.cpuset_mems_allowed, > *nodes); > - pol->w.cpuset_mems_allowed = tmp; > + pol->w.cpuset_mems_allowed = *nodes; > } > > if (nodes_empty(tmp)) hm, I'm not surprised the code broke. What the heck is going on in there? It used to have a perfunctory comment, but Vlastimil deleted it. Could someone please propose a comment for the above code block explaining why we're doing what we do?