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[99.254.144.39]) by smtp.gmail.com with ESMTPSA id d5-20020ad450a5000000b0062ffcda34c6sm1267657qvq.137.2023.06.20.07.40.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Jun 2023 07:40:58 -0700 (PDT) Date: Tue, 20 Jun 2023 10:40:56 -0400 From: Peter Xu To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Matthew Wilcox , Andrea Arcangeli , John Hubbard , Mike Rapoport , Vlastimil Babka , "Kirill A . Shutemov" , Andrew Morton , Mike Kravetz , James Houghton , Hugh Dickins Subject: Re: [PATCH 3/7] mm/hugetlb: Add page_mask for hugetlb_follow_page_mask() Message-ID: References: <20230613215346.1022773-1-peterx@redhat.com> <20230613215346.1022773-4-peterx@redhat.com> <24f4a22e-7d3b-544b-320f-bba5abb92285@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <24f4a22e-7d3b-544b-320f-bba5abb92285@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 20, 2023 at 09:01:23AM +0200, David Hildenbrand wrote: > On 19.06.23 23:43, Peter Xu wrote: > > On Tue, Jun 13, 2023 at 05:53:42PM -0400, Peter Xu wrote: > > > @@ -6506,6 +6507,7 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, > > > * because we hold the ptl lock and have verified pte_present(). > > > */ > > > WARN_ON_ONCE(try_grab_page(page, flags)); > > > + *page_mask = huge_page_mask(h); > > > > Sorry, I was wrong this line. It should be: > > > > *page_mask = ~huge_page_mask(h) >> PAGE_SHIFT; > > > > That's ... surprising. It feels like either page_mask or huge_page_mask() > has a misleading name .... > > h->mask = ~(huge_page_size(h) - 1); > > > For PMDs, we do > > ctx->page_mask = HPAGE_PMD_NR - 1; > > > Maybe > > *page_mask = PHYS_PFN(huge_page_size(h)) - 1; > > Would be clearer. Since I just posted a new version.. I'll see whether I should get that cleaned up in a new one. > > I guess "page_mask" should actually be "pfn_mask" ... but the meaning > regarding PAGE_MASK are still inverted ... Yes, pfn_mask can be at least slightly better. I can add a patch to rename it, or we can also do it on top as cleanups. Thanks, -- Peter Xu