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[45.249.212.35]) by mx.google.com with ESMTPS id t19si2279249vsp.267.2019.02.26.06.34.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Feb 2019 06:34:39 -0800 (PST) Received-SPF: pass (google.com: domain of zhongjiang@huawei.com designates 45.249.212.35 as permitted sender) client-ip=45.249.212.35; Authentication-Results: mx.google.com; spf=pass (google.com: domain of zhongjiang@huawei.com designates 45.249.212.35 as permitted sender) smtp.mailfrom=zhongjiang@huawei.com Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 84FAC77CDBC0C7823188; Tue, 26 Feb 2019 22:34:34 +0800 (CST) Received: from [127.0.0.1] (10.177.29.68) by DGGEMS413-HUB.china.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.408.0; Tue, 26 Feb 2019 22:34:33 +0800 Message-ID: <5C754E78.4050804@huawei.com> Date: Tue, 26 Feb 2019 22:34:32 +0800 From: zhong jiang User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: "Kirill A. Shutemov" CC: , , , , , , Subject: Re: [PATCH] mm: hwpoison: fix thp split handing in soft_offline_in_use_page() References: <1551179880-65331-1-git-send-email-zhongjiang@huawei.com> <20190226135156.mifspmbdyr6m3hff@kshutemo-mobl1> In-Reply-To: <20190226135156.mifspmbdyr6m3hff@kshutemo-mobl1> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.29.68] X-CFilter-Loop: Reflected 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 2019/2/26 21:51, Kirill A. Shutemov wrote: > On Tue, Feb 26, 2019 at 07:18:00PM +0800, zhong jiang wrote: >> From: zhongjiang >> >> When soft_offline_in_use_page() runs on a thp tail page after pmd is plit, > s/plit/split/ > >> we trigger the following VM_BUG_ON_PAGE(): >> >> Memory failure: 0x3755ff: non anonymous thp >> __get_any_page: 0x3755ff: unknown zero refcount page type 2fffff80000000 >> Soft offlining pfn 0x34d805 at process virtual address 0x20fff000 >> page:ffffea000d360140 count:0 mapcount:0 mapping:0000000000000000 index:0x1 >> flags: 0x2fffff80000000() >> raw: 002fffff80000000 ffffea000d360108 ffffea000d360188 0000000000000000 >> raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000 >> page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0) >> ------------[ cut here ]------------ >> kernel BUG at ./include/linux/mm.h:519! >> >> soft_offline_in_use_page() passed refcount and page lock from tail page to >> head page, which is not needed because we can pass any subpage to >> split_huge_page(). > I don't see a description of what is going wrong and why change will fixed > it. From the description, it appears as it's cosmetic-only change. > > Please elaborate. When soft_offline_in_use_page runs on a thp tail page after pmd is split, and we pass the head page to split_huge_page, Unfortunately, the tail page can be free or count turn into zero. Thanks, zhong jiang