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[213.151.95.130]) by smtp.gmail.com with ESMTPSA id t25sm3074517wmj.19.2020.01.09.07.00.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jan 2020 07:00:52 -0800 (PST) Date: Thu, 9 Jan 2020 16:00:52 +0100 From: Michal Hocko To: Li Xinhai Cc: linux-mm@kvack.org, "Kirill A. Shutemov" , Mike Kravetz Subject: Re: [PATCH v2] mm/page_vma_mapped.c: Detect mismatched pfn of hugetlbfs page in pfn_in_hpage() Message-ID: <20200109150052.GT4951@dhcp22.suse.cz> References: <1578579963-6075-1-git-send-email-lixinhai.lxh@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1578579963-6075-1-git-send-email-lixinhai.lxh@gmail.com> User-Agent: Mutt/1.12.2 (2019-09-21) 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 Mike who is hugetlb maintainer] On Thu 09-01-20 14:26:02, Li Xinhai wrote: > check_pte is called for hugetlbfs page and comparing pfn in pfn_in_page, > where pfn is compared in range [hpage_pfn, hpage_pfn+HPAGE_PMD_NR). For > hugetlbfs page, pfn must equal to hpage_pfn, so catch it as bug if they > are not equal. Why do we need this? Would that help to debug any past bug? > Signed-off-by: Li Xinhai > Cc: Kirill A. Shutemov > --- > mm/page_vma_mapped.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c > index eff4b45..713aaed 100644 > --- a/mm/page_vma_mapped.c > +++ b/mm/page_vma_mapped.c > @@ -55,6 +55,7 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw) > static inline bool pfn_in_hpage(struct page *hpage, unsigned long pfn) > { > unsigned long hpage_pfn = page_to_pfn(hpage); > + VM_BUG_ON_PAGE(PageHuge(hpage) && pfn != hpage_pfn, hpage); > > /* THP can be referenced by any subpage */ > return pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage); > -- > 1.8.3.1 > -- Michal Hocko SUSE Labs