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Shutemov" To: zhong jiang Cc: n-horiguchi@ah.jp.nec.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mhocko@suse.com, hughd@google.com, mhocko@kernel.org Subject: Re: [PATCH] mm: hwpoison: fix thp split handing in soft_offline_in_use_page() Message-ID: <20190226135156.mifspmbdyr6m3hff@kshutemo-mobl1> References: <1551179880-65331-1-git-send-email-zhongjiang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1551179880-65331-1-git-send-email-zhongjiang@huawei.com> User-Agent: NeoMutt/20180716 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 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. -- Kirill A. Shutemov