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imf26.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf26.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1750730106; a=rsa-sha256; cv=none; b=4VEo42T05NLOr/raHnTHKkb8PP/4Fw7SBCyHfbbntHXKrrQbPw1PSbg6YNcWqJhY30ZK2w ekBkZW52SXApePLdHJxO0FTQl0iqiHi6AEldECvWBq/ydvzAVlFYvTuJ9ENpsMGlY74vH7 fa1Mf1Zp0ND6b5KgzfwmOpJsBGMkRY4= X-AuditID: a67dfc5b-681ff7000002311f-0d-685a05782dd9 Date: Tue, 24 Jun 2025 10:54:58 +0900 From: Byungchul Park To: Pavel Begunkov Cc: Mina Almasry , David Hildenbrand , Zi Yan , 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, harry.yoo@oracle.com, 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, 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, hannes@cmpxchg.org, jackmanb@google.com Subject: Re: [PATCH net-next v6 9/9] page_pool: access ->pp_magic through struct netmem_desc in page_pool_page_is_pp() Message-ID: <20250624015458.GD5820@system.software.com> References: <20250620041224.46646-1-byungchul@sk.com> <20250620041224.46646-10-byungchul@sk.com> <20250623101622.GB3199@system.software.com> <460ACE40-9E99-42B8-90F0-2B18D2D8C72C@nvidia.com> <41e68e52-5747-4b18-810d-4b20ada01c9a@gmail.com> <69762ce3-ead1-4324-ba33-9839efbe31e7@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; 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It checks the ownership with > > > netmem_is_pp(), which is basically the same as page_pool_page_is_pp() > > > but done though some aliasing. > > > > > > static inline bool netmem_is_pp(netmem_ref netmem) > > > { > > > return (netmem_get_pp_magic(netmem) & PP_MAGIC_MASK) == PP_SIGNATURE; > > > } > > > > > > I assume there is no point in moving the check to skbuff.c as it > > > already does exactly same test, but we can probably just kill it. > > > > > > > Even if we do kill it, maybe lets do that in a separate patch, and > > maybe a separate series. I would recommend not complicating this one? > FWIW, the discussion somewhat mentioned "long term", but I'm not > suggesting actually removing it, it serves the purpose. And in > long term the helper will be converted to use page->type / etc. > without touching pp fields, that should reduce the degree of > ugliness and make it more acceptable for keeping in mm. Agree. Byungchul > > > Also, AFAIU, this is about removing/moving the checks in > > bad_page_reason() and page_expected_state()? I think this check does > > fire sometimes. I saw at least 1 report in the last year of a > > bad_page_reason() check firing because the page_pool got its > > accounting wrong and released a page to the buddy allocator early, so > > maybe that new patch that removes that check should explain why this > > check is no longer necessary. > > -- > Pavel Begunkov