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Shutemov" To: Li Xinhai Cc: linux-mm@kvack.org, "Kirill A. Shutemov" Subject: Re: [PATCH] mm/page_vma_mapped.c: Exactly compare hugetlbfs page's pfn in pfn_in_hpage() Message-ID: <20200109123021.v4akwvcwjsbfc4xt@box> References: <1578552280-5703-1-git-send-email-lixinhai.lxh@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1578552280-5703-1-git-send-email-lixinhai.lxh@gmail.com> User-Agent: NeoMutt/20180716 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000303, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jan 09, 2020 at 06:44:40AM +0000, 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). Now > change it to match exactly for hugetlbfs page to avoid hiding any > potential problems. Hm. What potential problems do you talk about? I understand that for hugetlb pages pfn is always has to be equal hpage_pfn, but returning false for pfn in the range of the hugetlb page just because it's not head is not helpful. I would rather have VM_BUG_ON_PAGE(PageHuge(hpage) && pfn != hpage_pfn, hpage); there. > > Signed-off-by: Li Xinhai > Cc: Kirill A. Shutemov > --- > mm/page_vma_mapped.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c > index eff4b45..434978b 100644 > --- a/mm/page_vma_mapped.c > +++ b/mm/page_vma_mapped.c > @@ -55,6 +55,8 @@ 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); > + if (unlikely(PageHuge(hpage))) > + return pfn == hpage_pfn; > > /* THP can be referenced by any subpage */ > return pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage); > -- > 1.8.3.1 > > -- Kirill A. Shutemov