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Fri, 14 Nov 2025 18:51:11 -0800 (PST) Date: Sat, 15 Nov 2025 02:51:09 +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: <20251115025109.yerb7gbty4h7h63s@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: rspam06 X-Rspamd-Queue-Id: 893B2C0005 X-Stat-Signature: wdok9cai64a1omsdqfzicc6iotjsjxmb X-Rspam-User: X-HE-Tag: 1763175073-493623 X-HE-Meta: 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 zyPfc/zc B4FGXwtrbyOCBp2UQQOl0XjhQ2S3rm81hlMSjoVXa7Q/tk0UkKeYlL8yQCz3VXoqz5VqCcCqGClrM29tqxTCSGu/tp4sJ6yoBhAp4ddTkJvO+TC1XS57OWhXpvkN3rimem7vQu6CamGRd5QeBRWBtquGfhO0TgFcTyLiqOi4G08Dc7TwUe+IPlUxoJVQvbZmq0Rq6NSPIczro+l2wKXHE6Mhh8MAGTg7SWYqYSP4v2cjw2dERm1OOFe0wi5foLcodaCjEcnGVVtEVh3Izv4pkJGHRqP/QRwxN18xboNV9qlaCn3eqm2gONQSM4wG23jO/Cl5m 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. > Thanks, I got your point. I am not 100% for sure. While if we trust it returns 0 if folio doesn't support large folio, I am afraid we can trust it returns correct value it supports. Or that would be the issue to related file system. To be honest, I am lack of the capability to investigate all file system to make sure this value is properly setup. >-- >Cheers > >David -- Wei Yang Help you, Help me