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Thu, 04 Dec 2025 07:13:27 -0800 (PST) Date: Thu, 4 Dec 2025 15:13:26 +0000 From: Wei Yang To: "David Hildenbrand (Red Hat)" Cc: Wei Yang , willy@infradead.org, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm/huge_memory: consolidate order-related checks into folio_split_supported() Message-ID: <20251204151326.63twqgfwzxbco362@master> Reply-To: Wei Yang References: <20251114075703.10434-1-richard.weiyang@gmail.com> <827fd8d8-c327-4867-9693-ec06cded55a9@kernel.org> <20251114150310.eua55tcgxl4mgdnp@master> <64b43302-e8cc-4259-9fa1-e27721c0d193@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <64b43302-e8cc-4259-9fa1-e27721c0d193@kernel.org> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: BF78E1C0010 X-Stat-Signature: c65xmxb5di51sszxut1ysunm6ckxftuw X-Rspam-User: X-HE-Tag: 1764861209-469157 X-HE-Meta: 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 qHcHqYHj OFcXdAJ87FZ26dra1KXJMCLlpBpMu0gPjg6Y7Nc89zkSorzht5KloC8dxdANbDg1IVCI0GF3HujVz5dfnbvIZAFr+ZDCJhFLhA6TnuMAAUkVJxKQcU676e4yZYc3Ag+531153uNRUu/eutbbgVZb61d+odkiK7JWeb5iPSInb3DAf8j2OGKFdzkVzJ4IXBKxYSewfWpCFb8immIfbDnNV+/exZkCYHDS/oRKn0KJYAmaWvj5rilQNrhQx9ondcKd/6ABDmRlFAQPrX1huLkaWhrMoglr9DS9UlRTDtdrFsZ2YqIsDJCrREB3Im7Vs+z/CjgxH 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 Fri, Nov 14, 2025 at 08:36:20PM +0100, David Hildenbrand (Red Hat) wrote: >On 14.11.25 16:03, Wei Yang wrote: >> On Fri, Nov 14, 2025 at 09:49:34AM +0100, David Hildenbrand (Red Hat) wrote: >> > On 14.11.25 08:57, Wei Yang wrote: >> > > The primary goal of the folio_split_supported() function is to validate >> > > whether a folio is suitable for splitting and to bail out early if it is >> > > not. >> > > >> > > Currently, some order-related checks are scattered throughout the >> > > calling code rather than being centralized in folio_split_supported(). >> > > >> > > This commit moves all remaining order-related validation logic into >> > > folio_split_supported(). This consolidation ensures that the function >> > > serves its intended purpose as a single point of failure and improves >> > > the clarity and maintainability of the surrounding code. >> > >> > Combining the EINVAL handling sounds reasonable. >> > >> >> You mean: >> >> This commit combines the EINVAL handling logic into folio_split_supported(). >> This consolidation ... ? > >It was not a suggestion to change, it was rather only a comment from my side >:) > >[...] > >> > >> > The mapping_max_folio_order() check is new now. What is the default value of that? Is it always initialized properly? >> > >> >> Not sure "is new now" means what? >> >> Original check use mapping_large_folio_support() which calls >> mapping_max_folio_order(). It looks not new to me. > >Right, but we did not actually care about the exact value. > >IOW, we didn't check for order <= mapping_max_folio_order() before. > >SO I'm just curious if that is universally fine. > Hi, David I just happened to come across some code that might address your question here. Take a look at the function __filemap_get_folio(). It uses mapping_max_folio_order() and mapping_min_folio_order() to determine the appropriate folio order for page cache allocation. Just want to share what I found. >-- >Cheers > >David -- Wei Yang Help you, Help me