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Wed, 16 Aug 2023 14:48:21 -0700 (PDT) MIME-Version: 1.0 References: <20230812210053.2325091-1-zokeefe@google.com> In-Reply-To: From: "Zach O'Keefe" Date: Wed, 16 Aug 2023 14:47:45 -0700 Message-ID: Subject: Re: [EXTERNAL] [PATCH] mm/thp: fix "mm: thp: kill __transhuge_page_enabled()" To: Saurabh Singh Sengar Cc: Matthew Wilcox , Dan Williams , "linux-mm@kvack.org" , Yang Shi , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 87174C001F X-Stat-Signature: cic5a4g6wtkb44d5kghgy1wugx8anr48 X-HE-Tag: 1692222503-312822 X-HE-Meta: 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 MH1sCjb0 yfQ9kKEaMDrWUgzcRV4IY/9iALRz0404mkFtzoPdKPVp9coMgAaN1gR6uUQxgcivLIE9e1+nx3ii7bXqgGWvmyMOv3nW4hdsyPOaqD3pKQaCZYvJ6DJJLF9QXrnR+v/vRzqZjwInYNzLlHMhcZLvTgJjQztLt9BP2z17SW1tXsdEoP6j14Silleks3mp3B41/OmFUhD0HZgbwI2Md4LtvZ8kzvGkqlxpIJtX604Zpp6i0Y+UEgNxH5243QB1X4WRWWpg6OuTB3vJI+pA7JxVrpRTM9Q4rb+DPv8ViIuUhtHX34zmR/cE6tMKarg== 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: > We have a out of tree driver that maps huge pages through a file handle a= nd > relies on -> huge_fault. It used to work in 5.19 kernels but 6.1 changed = this > behaviour. > > I don=E2=80=99t think reverting the earlier behaviour of fault_path for h= uge pages should > impact kernel negatively. > > Do you think we can restore this earlier behaviour of kernel to allow pag= e fault > for huge pages via ->huge_fault. That seems reasonable to me. I think using the existence of a ->huge_fault() handler as a predicate to return "true" makes sense to me. The "normal" flow for file-backed memory along fault path still needs to return "false", so that we correctly fallback to ->fault() handler. Unless there are objections, I can do that in a v2.