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Fri, 08 Nov 2019 11:26:33 -0800 (PST) Date: Fri, 8 Nov 2019 12:26:29 -0700 In-Reply-To: <20190825200621.211494-1-yuzhao@google.com> Message-Id: <20191108192629.201556-1-yuzhao@google.com> Mime-Version: 1.0 References: <20190825200621.211494-1-yuzhao@google.com> X-Mailer: git-send-email 2.24.0.rc1.363.gb1bccd3e3d-goog Subject: [PATCH v2] mm: replace is_zero_pfn with is_huge_zero_pmd for thp From: Yu Zhao To: Andrew Morton Cc: Matthew Wilcox , Ralph Campbell , " =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= " , Will Deacon , Peter Zijlstra , "Aneesh Kumar K . V" , Dave Airlie , Thomas Hellstrom , Souptick Joarder , Gerald Schaefer , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Yu Zhao 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: For hugely mapped thp, we use is_huge_zero_pmd() to check if it's zero page or not. We do fill ptes with my_zero_pfn() when we split zero thp pmd, but this is not what we have in vm_normal_page_pmd() -- pmd_trans_huge_lock() makes sure of it. This is a trivial fix for /proc/pid/numa_maps, and AFAIK nobody complains about it. Gerald Schaefer asked: > Maybe the description could also mention the symptom of this bug? > I would assume that it affects anon/dirty accounting in gather_pte_stats(), > for huge mappings, if zero page mappings are not correctly recognized. I came across this while I was looking at the code, so I'm not aware of any symptom. Signed-off-by: Yu Zhao --- mm/memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index b1ca51a079f2..cf209f84ce4a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -654,7 +654,7 @@ struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr, if (pmd_devmap(pmd)) return NULL; - if (is_zero_pfn(pfn)) + if (is_huge_zero_pmd(pmd)) return NULL; if (unlikely(pfn > highest_memmap_pfn)) return NULL;