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AJvYcCVT4IC9PY0f49/YePZThw9+QgiXIwuq+6/at4uAWIIyAYqL5MD9+IMJjIvBjzxOGw2HQxdaWswlDg==@kvack.org X-Gm-Message-State: AOJu0YwOjxLRh3Q1bGsONbdE18pXjVqPure+UoFJRJ84eye169my351C mIxyh5wcFN42r+S19he+gfn7hysQNz97M2KGplRvvo8rqzoImXdPBm+V+oiaVhF6OU5OPPaaj1w W9cZ56MEqAhf2UqFvqnMQRXkuTY2viTbO/SDNvN+Q X-Gm-Gg: ASbGncsSxl5JmekOXmOxnNudMLbSrbb15oZnN57jGvWBuq/IL5jfo2b3TpSmiADkFfG aSYH5QpTL1rVrjK/xPV1niVmi18wH72mtMXH4JGTOOOvjItikBZbuZ11LST7V5fM6DMq/2aDc+H btkdDSlrfx+XBbjRr366b7CUkKcl1qJY7P8oFMs+O+Cotq X-Google-Smtp-Source: AGHT+IGEZRKG6xvZHogMtre77VgiSxDaYZdqjTk10sRxgiSBiBGpyaYgS/fptxzapbkZ7Jl7Refn+g7Umm+MVSkwFF8= X-Received: by 2002:a17:903:22cf:b0:235:e1e4:efc4 with SMTP id d9443c01a7336-236021cbd7cmr556885ad.14.1749152847887; Thu, 05 Jun 2025 12:47:27 -0700 (PDT) MIME-Version: 1.0 References: <20250604025246.61616-1-byungchul@sk.com> <20250604025246.61616-19-byungchul@sk.com> <390073b2-cc7f-4d31-a1c8-4149e884ce95@gmail.com> In-Reply-To: From: Mina Almasry Date: Thu, 5 Jun 2025 12:47:14 -0700 X-Gm-Features: AX0GCFuQUodCCzxMMKtUv6I9nARNgb_4QREwvin7nUUsfjMZH4C0VBF2D5sefUE Message-ID: Subject: Re: [RFC v4 18/18] page_pool: access ->pp_magic through struct netmem_desc in page_pool_page_is_pp() To: Harry Yoo Cc: Pavel Begunkov , Byungchul Park , willy@infradead.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, kuba@kernel.org, ilias.apalodimas@linaro.org, hawk@kernel.org, akpm@linux-foundation.org, davem@davemloft.net, john.fastabend@gmail.com, andrew+netdev@lunn.ch, toke@redhat.com, tariqt@nvidia.com, edumazet@google.com, pabeni@redhat.com, saeedm@nvidia.com, leon@kernel.org, ast@kernel.org, daniel@iogearbox.net, 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, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, vishal.moola@gmail.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5AF4C180002 X-Stat-Signature: 7ujdk9qp8e99r8wfpr9zhhrsnsju4xnz X-Rspam-User: X-HE-Tag: 1749152849-162963 X-HE-Meta: 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 p49Hb/3S QN11oOUXaz6WdrHvmIsTEOdG+kNsxcnezmw76ir1nM41iXaISf/qzzpX1kxhJp66yCG1rfWL1sYuquS/D17c3gPN3Z/0b0EDu1tAh1JUe6RM9b3n4G4TVfOD0vyp2veDM7mI2eMCL8a8lQQ+wWJE1zxpZ8Fvya2nCiOSmlS6nZochdot01q2hei05rrTj6HXvAg9H4MjuA3wOD0e6wAGewvJWIyZ7pOPA3td8jCD24krX5hZ1VxUgfdbjJ+82UXfjA3KuPqAcqyb518FZQ/aGfdfAn8df4kne0u0GGGQhLGSl2zzMqDu/o7PQb04sit+uJhjmZgyEXGrlYalfB8mQAqRJmRsJpk6bKWzy 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 Thu, Jun 5, 2025 at 4:49=E2=80=AFAM Harry Yoo wro= te: > > On Thu, Jun 05, 2025 at 11:56:14AM +0100, Pavel Begunkov wrote: > > On 6/4/25 03:52, Byungchul Park wrote: > > > To simplify struct page, the effort to separate its own descriptor fr= om > > > struct page is required and the work for page pool is on going. > > > > > > To achieve that, all the code should avoid directly accessing page po= ol > > > members of struct page. > > > > Just to clarify, are we leaving the corresponding struct page fields > > for now until the final memdesc conversion is done? > > Yes, that's correct. > > > If so, it might be better to leave the access in page_pool_page_is_pp() > > to be "page->pp_magic", so that once removed the build fails until > > the helper is fixed up to use the page->type or so. > > When we truly separate netmem from struct page, we won't have 'lru' field > in memdesc (because not all types of memory are on LRU list), > so NETMEM_DESC_ASSERT_OFFSET(lru, pp_magic) should fail. > > And then page_pool_page_is_pp() should be changed to check lower bits > of memdesc pointer to identify its type. > Oh boy, I'm not sure that works. We already do LSB tricks with netmem_ref to tell what kind of ref it is. I think the LSB pointer tricks with netmem_ref and netmem_desc may trample each other's toes. I guess we'll cross that bridge when we get to it... --=20 Thanks, Mina