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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 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231116012908.392077-7-peterx@redhat.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Rspamd-Queue-Id: C1FBC180008 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 63wr737tb5hbby4fom44wot6nfj5hpxg X-HE-Tag: 1700468791-125145 X-HE-Meta: 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 yCuhiaUn WvAtsWvX/Lxv+O/h+KTkfspo19GfS9/SNAE7OIHuRHSTjeDghcyW403ktLpkcmNRAxlWMW10vV5aPGCCHlL8k7H6AJiuuvDXIDxkLt9Cbo2OOZK2o6xNpERIYKfnleC/YGjxuWmNEjQ02p09VbCRQSwYuAA7LpBR2ePZjOxH4wHLmcg4fWkK8hIMwo+JZGLKCpe1GEz+P2YM7STDpYoeaX2blw5+CAMfMEEZJxj1nrivoggDdjzZpCb8AU7BH3pBMl+uQ24NWvuxkPid9HSefJoLFLn5qGmVpDbG0RxINTnFcYW6SM7/hbjxluGB2/jFBTMlmqFbBANue8LVgmYj/wHkVpb1MEvF0MzRyJZUvrg65yGHz/cn0EjO2lBdmZoSKdPSJFlXYv8VqkHNY7duWGObk9MFk8Ztfq1wjkTPEIuaP7Tys/OhD753kjA== 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 15, 2023 at 08:29:02PM -0500, Peter Xu wrote: > Hugepd format is only used in PowerPC with hugetlbfs. In commit > a6e79df92e4a ("mm/gup: disallow FOLL_LONGTERM GUP-fast writing to > file-backed mappings"), we added a check to fail gup-fast if there's > potential risk of violating GUP over writeback file systems. That should > never apply to hugepd. > > Drop that check, not only because it'll never be true for hugepd, but also > it paves way for reusing the function outside fast-gup. What prevents us from ever using hugepd with file mappings? I think it would naturally fit in with how large folios for the pagecache work. So keeping this check and generalizing it seems like the better idea to me.