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d=hostedemail.com; t=1752494785; a=rsa-sha256; cv=none; b=NgK26YbcavzgjYXK5cmkRlzlrhecu7Q6hs8hbsiCrUqSjTn4WpDJCDRgToW5XtYrrJhB7T 1l0jwvVew2D7fg13XpewhbpLl5C5oC8ApMgXkm/U5afMw/z3/a3Vfn0zrZlu/avlbRFlxr /UOsNIfRDFJb2beIezLqnnSI+O0f0Wk= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf21.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com X-AuditID: a67dfc5b-681ff7000002311f-a8-6874f2bee77b Date: Mon, 14 Jul 2025 21:06:17 +0900 From: Byungchul Park To: Pavel Begunkov Cc: willy@infradead.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, kuba@kernel.org, almasrymina@google.com, 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, 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, hannes@cmpxchg.org, ziy@nvidia.com, jackmanb@google.com Subject: Re: [PATCH net-next v9 2/8] netmem: introduce utility APIs to use struct netmem_desc Message-ID: <20250714120617.GA36228@system.software.com> References: <20250710082807.27402-1-byungchul@sk.com> <20250710082807.27402-3-byungchul@sk.com> <4a8b0a45-b829-462c-a655-af0bda10a246@gmail.com> <20250713230752.GA7758@system.software.com> <5ee839d6-2734-41c5-b34c-8d686c910bc8@gmail.com> <20250714100551.GA44803@system.software.com> MIME-Version: 1.0 Content-Type: text/plain; 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> > > > > > } > > > > > > > > > > > > +#define nmdesc_to_page(nmdesc) (_Generic((nmdesc), \ > > > > > > + const struct netmem_desc * : (const struct page *)(nmdesc), \ > > > > > > + struct netmem_desc * : (struct page *)(nmdesc))) > > > > > > > > > > Considering that nmdesc is going to be separated from pages and > > > > > accessed through indirection, and back reference to the page is > > > > > not needed (at least for net/), this helper shouldn't even exist. > > > > > And in fact, you don't really use it ... > > > > > > +static inline struct netmem_desc *page_to_nmdesc(struct page *page) > > > > > > +{ > > > > > > + VM_BUG_ON_PAGE(PageTail(page), page); > > > > > > + return (struct netmem_desc *)page; > > > > > > +} > > > > > > + > > > > > > +static inline void *nmdesc_address(struct netmem_desc *nmdesc) > > > > > > +{ > > > > > > + return page_address(nmdesc_to_page(nmdesc)); > > > > > > +} > > > > > > > > > > ... That's the only caller, and nmdesc_address() is not used, so > > > > > just nuke both of them. This helper doesn't even make sense. > > > > > > > > > > Please avoid introducing functions that you don't use as a general > > > > > rule. > > > > > > > > I'm sorry about making you confused. I should've included another patch > > > > using the helper like the following. > > > > > > Ah, I see. And still, it's not a great function. There should be > > > no way to extract a page or a page address from a nmdesc. > > > > > > For the diff below it's same as with the mt76 patch, it's allocating > > > a page, expects it to be a page, using it as a page, but for no reason > > > keeps it wrapped into netmem. It only adds confusion and overhead. > > > A rule of thumb would be only converting to netmem if the new code > > > would be able to work with a netmem-wrapped net_iovs. > > > > Thanks. I'm now working on this job, avoiding your concern. > > > > By the way, am I supposed to wait for you to complete the work about > > extracting type from page e.g. page pool (or bump) type? > > 1/8 doesn't depend on it, if you're sending it separately. As for Right. > the rest, it might need to wait for the PGTY change, which is more Only 3/8 needs to wait for the PGTY change. The rest can be merged regardless of it if acceptable. Byungchul > likely to be for 6.18 > > -- > Pavel Begunkov