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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vNXIf-000000075NS-1PRu; Mon, 24 Nov 2025 14:12:17 +0000 Date: Mon, 24 Nov 2025 14:12:17 +0000 From: Matthew Wilcox To: Harry Yoo Cc: Vlastimil Babka , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org Subject: Re: [PATCH v4 16/16] slab: Remove references to folios from virt_to_slab() Message-ID: References: <20251113000932.1589073-1-willy@infradead.org> <20251113000932.1589073-17-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 18F46140007 X-Stat-Signature: ir3uc3jsbbc34rub48qgm1aine9i36dp X-Rspam-User: X-HE-Tag: 1763993540-977071 X-HE-Meta: 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 BrA7ycO3 GhdJccm6EyRIs72YlCXkmc8FX+h8SGJNM1aCny66S0KqsyVO5YR01kl2oWeSQ6flmeypNPMACXUL+px1XSRAIf3joz/cP/icnOUZnrpFGJ2hGJNFtBJHPVIdN3sme1nXa6EvRikSzs8EpkKfDKuR51wkg5bfNT8pVm7VCM0FVD/ffGy6PHWUlQ7fqgTzU+YIboo4smuNqetZJU4RXpDXeDfE9peHgrLtqmOEWfEOglht6U8IK19F4ip8Ze9YGGlJ+oGtcJ9rhAVD5g0YQdO072Ij4d2Z2aEODqxs2+/xIu0kF4EU= 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 Mon, Nov 24, 2025 at 04:09:32PM +0900, Harry Yoo wrote: > By the way, there is one remaining code snippet that references folio in > alloc_from_pcs(): > > if (folio_nid(virt_to_folio(object)) != node) > > which won't work after separating struct slab from struct folio :) Oh, thank you! This is a fairly silly thing to do today as there's an unnecessary use of compound_head() to go from page to folio. Each page knows which node it belongs to (and that's going to continue to be true until we get to an 8-byte struct page) so there's no need to do page_to_memdesc(). It'll be worth it once we do get to an 8 byte struct page as we'll know what kind of memdesc this is rather than having page_to_nid() figure it out. Patch soon.