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Mon, 03 Nov 2025 04:24:41 -0800 (PST) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6407b392d5dsm9676772a12.15.2025.11.03.04.24.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Nov 2025 04:24:40 -0800 (PST) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id EE02432844E; Mon, 03 Nov 2025 13:24:39 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Byungchul Park , linux-mm@kvack.org, netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel_team@skhynix.com, harry.yoo@oracle.com, ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, kuba@kernel.org, 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, 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 In-Reply-To: <20251103075108.26437-2-byungchul@sk.com> References: <20251103075108.26437-1-byungchul@sk.com> <20251103075108.26437-2-byungchul@sk.com> X-Clacks-Overhead: GNU Terry Pratchett Date: Mon, 03 Nov 2025 13:24:39 +0100 Message-ID: <87ms53pam0.fsf@toke.dk> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Byungchul Park writes: > Currently, the condition 'page->pp_magic =3D=3D PP_SIGNATURE' is used to > determine if a page belongs to a page pool. However, with the planned > removal of ->pp_magic, we will instead leverage the page_type in struct > page, such as PGTY_netpp, for this purpose. > > That works for page-backed network memory. However, for net_iov not > page-backed, the identification cannot be based on the page_type. > Instead, nmdesc->pp can be used to see if it belongs to a page pool, by > making sure nmdesc->pp is NULL otherwise. > > For net_iov not page-backed, initialize it using nmdesc->pp =3D NULL in > net_devmem_bind_dmabuf() and using kvmalloc_array(__GFP_ZERO) in > io_zcrx_create_area() so that netmem_is_pp() can check if nmdesc->pp is > !NULL to confirm its usage as page pool. > > Signed-off-by: Byungchul Park > Reviewed-by: Mina Almasry Reviewed-by: Toke H=C3=B8iland-J=C3=B8rgensen