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b=I4EA2HN1xggEwDDY+EXXjeuTilUUVALnglQLg5zXBbhd1yvhPoCdwFWeQubJDPAfD y3NuOuh15eivOqBrC5NW9R/erOX2PrG5kdAphHgZAJKLP+tlz7mdlRksYtvMzMJu2X MgvuHswuuxhuknZuovUsvwbX1K0ZS1iaIdOTGnknf0YLeig+4uroSN5muMwksb5JF2 A2f094CKNKnI0a1QHYkgu0hGk7MzhAhRLaFd/TYCSkMsvVcUy7kFVeqROi1LFqezJl M+ZgXQoAm7PEINoyJGzndzB3iHFArwOaWzWRQE/94FXzdWhJ3zwanQ1y/k1CeEVzeu Cc9MjX6Hk5dww== Date: Fri, 7 Nov 2025 17:41:29 -0800 From: Jakub Kicinski To: Byungchul Park Cc: linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel_team@skhynix.com, harry.yoo@oracle.com, ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, hawk@kernel.org, john.fastabend@gmail.com, sdf@fomichev.me, saeedm@nvidia.com, leon@kernel.org, tariqt@nvidia.com, mbloch@nvidia.com, andrew+netdev@lunn.ch, edumazet@google.com, pabeni@redhat.com, akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, horms@kernel.org, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, ilias.apalodimas@linaro.org, willy@infradead.org, brauner@kernel.org, kas@kernel.org, yuzhao@google.com, usamaarif642@gmail.com, baolin.wang@linux.alibaba.com, almasrymina@google.com, toke@redhat.com, asml.silence@gmail.com, bpf@vger.kernel.org, linux-rdma@vger.kernel.org, sfr@canb.auug.org.au, dw@davidwei.uk, ap420073@gmail.com, dtatulea@nvidia.com Subject: Re: [RFC mm v5 1/2] page_pool: check nmdesc->pp to see its usage as page pool for net_iov not page-backed Message-ID: <20251107174129.62a3f39c@kernel.org> In-Reply-To: <20251107044708.GA54407@system.software.com> References: <20251103075108.26437-1-byungchul@sk.com> <20251103075108.26437-2-byungchul@sk.com> <20251106173320.2f8e683a@kernel.org> <20251107015902.GA3021@system.software.com> <20251106180810.6b06f71a@kernel.org> <20251107044708.GA54407@system.software.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 9412D20003 X-Stat-Signature: hhoczihhnukrsac4y8a7w79szsgfk715 X-Rspam-User: X-HE-Tag: 1762566093-888376 X-HE-Meta: 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 yUxdgQw+ c08I7UGbGf4agSyWJT5kHXZPWX+OAjqklD3aWXb3jNV/QZ+/Soth6zRUBpazFVlBdJ0e2D9jumSueBv8WUR/d9PEVYWX9kkAxqPoQ3yP55ZCE64/0s7sa0H9yCx2sCGGlJDLjs7He10cK6+IV4vHU/sAF+NE3s9woJXsdj/MteqAhLzAkCAmG69eLNeV9SntP801cXDM4eebmh7qJU+w5vW/037mQr6Hv0pnQzRbfpKoGyndUjDlEnSSKRD03ki4J2VnB6Sa/S/tyJKq6M4LfIJG5dvwxIjDBjz6Ec4savxJOnCwbvUCsKxHiy/cnUVKcqzxTBUmSB8yXubDCnH+1tt8wKhOMbythsHTLdUW4S0PJ5gQoDedq9SkAaNAGGNLPbmhn 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, 7 Nov 2025 13:47:08 +0900 Byungchul Park wrote: > The offset of page_type in struct page cannot be used in struct net_iov > for the same purpose, since the offset in struct net_iov is for storing > (struct net_iov_area *)owner. owner does not have to be at a fixed offset. Can we not move owner to _pp_mapping_pad ? Or reorder it with type, enum net_iov_type only has 2 values we can smoosh it with page_type easily. > Yeah, you can tell 'why don't we add the field, page_type, to struct > net_iov (or struct netmem_desc)' so as to be like: > > struct net_iov { > union { > struct netmem_desc desc; > struct > { > unsigned long _flags; > unsigned long pp_magic; > struct page_pool *pp; > unsigned long _pp_mapping_pad; > unsigned long dma_addr; > atomic_long_t pp_ref_count; > + unsigned int page_type; // add this field newly > }; > }; > struct net_iov_area *owner; // the same offet of page_type > enum net_iov_type type; > }; > > I think we can make it anyway but it makes less sense to add page_type > to struct net_iov, only for PGTY_netpp. > > It'd be better to use netmem_desc->pp for that purpose, IMO.