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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uEgAZ-0000000AU2i-4AqK; Tue, 13 May 2025 03:19:04 +0000 Date: Tue, 13 May 2025 04:19:03 +0100 From: Matthew Wilcox To: Byungchul Park Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, kuba@kernel.org, almasrymina@google.com, ilias.apalodimas@linaro.org, harry.yoo@oracle.com, hawk@kernel.org, akpm@linux-foundation.org, ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, john.fastabend@gmail.com, andrew+netdev@lunn.ch, edumazet@google.com, pabeni@redhat.com, vishal.moola@gmail.com Subject: Re: [RFC 19/19] mm, netmem: remove the page pool members in struct page Message-ID: References: <20250509115126.63190-1-byungchul@sk.com> <20250509115126.63190-20-byungchul@sk.com> <20250512125103.GC45370@system.software.com> <20250513014200.GA577@system.software.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250513014200.GA577@system.software.com> X-Stat-Signature: gtetahao56h4a4ibnnbbkjd8in6k1sac X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 842B8180002 X-HE-Tag: 1747106352-609530 X-HE-Meta: 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 3NAPsKcV ovtDm+2kQ5y2AGeoVMthAI4CVUYx1kdbkL4iq1TV5bd04TOhlpFfs3oDELOEE8UIBoNiOaU4GgQT9PeGq9/XGIsMnj0T0W0MROF8VYD/AsjEgro5Oeq4Df91PqVyUxFAR9Ys7EzYUHMpoUATG5QwJm9Hd3PGVbvKfVBRMKpZ7y3/9oIk5Tea+/P/Ik7Pv/bhhwDWi8+G2cuOefeXZf1pCcNYDLTZrTm9yNeA2zvKx5aLNyaWhYZP3uuxt7eF1lRIGs9Gjp5divxvubhlNPPugpFrlcPVsuY6fOBIaM5bjsRYKmdrcSSMANu4KnA== 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 Tue, May 13, 2025 at 10:42:00AM +0900, Byungchul Park wrote: > Just in case, lemme explain what I meant, for *example*: I understood what you meant. > In here, operating on struct netmem_desc can smash _mapcount and > _refcount in struct page unexpectedly, even though sizeof(struct > netmem_desc) <= sizeof(struct page). That's why I think the place holder > is necessary until it completely gets separated so as to have its own > instance. We could tighten up the assert a bit. eg static_assert(sizeof(struct netmem_desc) <= offsetof(struct page, _refcount)); We _can't_ shrink struct page until struct folio is dynamically allocated. The same patch series that dynamically allocates folio will do the same for netmem and slab and ptdesc and ...