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[77.162.219.136]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6a611b675d1sm2933128a12.9.2026.08.30.15.11.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 30 Aug 2026 15:11:15 -0700 (PDT) From: Bruno Xavier To: fabriciogava@gmail.com, florian@schauer.to Cc: netdev@vger.kernel.org, kuba@kernel.org, edumazet@google.com, pabeni@redhat.com, davem@davemloft.net, lorenzo@kernel.org, hawk@kernel.org, ilias.apalodimas@linaro.org, bpf@vger.kernel.org, Bruno Xavier Subject: Re: [PATCH] net: skbuff: keep the page_pool fragment offset aligned in skb_pp_cow_data() Date: Mon, 31 Aug 2026 00:11:13 +0200 Message-ID: <20260830221113.1238112-1-bfxavier@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260830212331.546227-1-fabriciogava@gmail.com> References: <20260827122926.31123-1-bfxavier@gmail.com> <20260830212331.546227-1-fabriciogava@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Sun, Aug 30, 2026 at 09:23:27PM +0000, Fabricio Gava wrote: > That version has already been sent, by Florian Schauer, the day before > this patch -- "page_pool: keep frag_offset aligned for odd-sized requests", > now at v2: Thanks for linking the threads, I had not seen Florian's v1. > xdp_copy_frags_from_zc() does the same, net/core/xdp.c:700-705: I mispoke in my own notes on this one. I checked system_page_pool for other consumers before sending and read it as having exactly one, net/core/dev.c:5619. xdp.c:753 is the second. So fixing skb_pp_cow_data() alone leaves the defect reachable through the zero-copy path. Florian's patch is the right fix. Please drop this one. On veth, drivers/net/veth.c:762 passes its own rq->page_pool rather than the per-cpu one, so I don't think it widens the sharing. It widens where the misaligning loop runs, which is the part your reading of the Fixes tag gets at. I have the reproducer and an A/B kernel harness here. Building v2 now, numbers on Florian's thread. Thanks, Bruno