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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id a24-20020a0ca998000000b00677a12f11bcsm625712qvb.24.2023.11.23.08.10.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Nov 2023 08:10:02 -0800 (PST) Date: Thu, 23 Nov 2023 11:10:00 -0500 From: Peter Xu To: Christoph Hellwig Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , James Houghton , Lorenzo Stoakes , David Hildenbrand , Vlastimil Babka , John Hubbard , Yang Shi , Rik van Riel , Hugh Dickins , Matthew Wilcox , Jason Gunthorpe , Axel Rasmussen , "Kirill A . Shutemov" , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Mike Rapoport , Mike Kravetz Subject: Re: [PATCH RFC 06/12] mm/gup: Drop folio_fast_pin_allowed() in hugepd processing Message-ID: References: <20231116012908.392077-1-peterx@redhat.com> <20231116012908.392077-7-peterx@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: B28A1180016 X-Rspam-User: X-Stat-Signature: qhpumaz9o4udee9d4zye5po8xqxrg85n X-Rspamd-Server: rspam03 X-HE-Tag: 1700755805-973904 X-HE-Meta: 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 oEwt3THw GQZxMxcr2SHBz9SmWg4tJteS0SoK2Ff8UrrsRBYrVy4zJxO3d45sagcqYF3+wjgR2M1uYg/E5gye+6d2c/NNtzb2wuEGNP4AOKFhG8T7FFtk9WrK+Pc+7ZhVm6MhIPswhNt4gtwLiWxfraSwaaJ28IOA/R8Tv02o/qH4qRe9XV0vRgpLUXqEpWrlmSt0dMSdxcCthSJI4HLBXw/k6A7kX7r9D7kYCPjC3XYkidcNSZxVo3zSoBGK0NRR+Uqed6/cwZ/xrJzBGy8RF2mkhA46t6jsxlLeNJPDiYtFpv+rJMqly/U66DCJS8QTLIIGhlBdAYhxqDkza1ToDkr/9EBrjwVWZ/kVQiDS1+EPOEWQOPINOGT6TL/OAlA478Q== 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: List-Subscribe: List-Unsubscribe: On Wed, Nov 22, 2023 at 11:21:50PM -0800, Christoph Hellwig wrote: > That alone sounds like a good reason to not bother. So unless more > qualified people have a different opinion I'm fine with this patch > as long as you leave a comment in place, and ammend the commit message > with some of the very useful information from your mail. Will do, thanks. This is what I will squash into the same patch in the new version, as the current plan: +/* + * NOTE: currently hugepd is only used in hugetlbfs file systems on Power, + * which does not have issue with folio writeback against GUP updates. + * When hugepd will be extended to support non-hugetlbfs or even anonymous + * memory, we need to do extra check as what we do with most of the other + * folios. See writable_file_mapping_allowed() and folio_fast_pin_allowed() + * for more information. + */ static int gup_huge_pd(hugepd_t hugepd, unsigned long addr, unsigned int pdshift, unsigned long end, unsigned int flags, struct page **pages, int *nr) -- Peter Xu