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Shutemov" To: Zi Yan Cc: "Matthew Wilcox (Oracle)" , linux-mm@kvack.org, Ryan Roberts , Hugh Dickins , David Hildenbrand , Yang Shi , Miaohe Lin , Kefeng Wang , Yu Zhao , John Hubbard , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/6] mm/huge_memory: add two new (yet used) functions for folio_split() Message-ID: References: <20241101150357.1752726-1-ziy@nvidia.com> <20241101150357.1752726-2-ziy@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 543EF14002F X-Rspamd-Server: rspam01 X-Stat-Signature: 7r4c5xsw5su33yssa61nu47ffiy8itzb X-HE-Tag: 1730988110-303681 X-HE-Meta: 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 k4llHhYj /FHMQ4mp6wGbT+Y56ga2B/eN/9GzB+VXtvoJQAbZAH3hAMaby/mBzYn5O88l21dMsT9k9PxuayrJ1sciFBwRREF5hfsfJEUyxFEAsdKLxTfEjKTlvVsR3a2bUhsu79LO8vVSvDiEEmlbgAgVMmnTkrHvBLvQ7VJg6moQOf3+yXIxe0cDTyOceSObIc7wHVL0F/cQyKiNg8sbmp/ZSxMoAB9ww40RSD8CxhHQxbkum6jcZMpkidZ67VfMPJH26grlTcWJAynK3B8hzFPsM1HivCRP1appCJnkv8Rst 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 06, 2024 at 05:06:32PM -0500, Zi Yan wrote: > >> + } else { > >> + if (PageHead(head)) > >> + ClearPageCompound(head); > > > > Huh? You only have to test for PageHead() because it is inside the loop. > > It has to be done after loop is done. > > You are right, will remove this and add the code below after the loop. > > if (!new_order && PageHead(&folio->page)) > ClearPageCompound(&folio->page); PageHead(&forlio->page) is always true, isn't it? > >> + if (folio_test_anon(folio) && folio_test_swapcache(folio)) { > >> + if (!uniform_split) > >> + return -EINVAL; > > > > Why this limitation? > > I am not closely following the status of mTHP support in swap. If it > is supported, this can be removed. Right now, split_huge_page_to_list_to_order() > only allows to split a swapcache folio to order 0[1]. > > [1] https://elixir.bootlin.com/linux/v6.12-rc6/source/mm/huge_memory.c#L3397 It would be nice to clarify this or at least add a comment. -- Kiryl Shutsemau / Kirill A. Shutemov