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t=1752487562; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gJJOji5TeFGRKckBy5yDJe/jroLDlO4MJuLaR9u2e38=; b=r9aXobEo65ogj47X1hAe67AYiv2uJqPGnpg0HMxaNXKKcl3Dh345JQhXgvrkUIoopkyEmR AtINKAx1nbcMaZHDcsdsC22eGuFKwidd7cyYjz1DH0FsZJ1dTmwX1U0TLBOkqpqAZwP7jU HS40lbFIJK0w4UFmHvY/56owuZ5olMI= X-AuditID: a67dfc5b-669ff7000002311f-07-6874d685ba14 Date: Mon, 14 Jul 2025 19:05:51 +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: <20250714100551.GA44803@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> 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? Byungchul > > diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c b/drivers/net/ethernet/intel/idpf/idpf_txrx.c > > index cef9dfb877e8..adccc7c8e68f 100644 > > --- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c > > +++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c > > @@ -3266,7 +3266,7 @@ static u32 idpf_rx_hsplit_wa(const struct libeth_fqe *hdr, > > struct libeth_fqe *buf, u32 data_len) > > { > > u32 copy = data_len <= L1_CACHE_BYTES ? data_len : ETH_HLEN; > > - struct page *hdr_page, *buf_page; > > + struct netmem_desc *hdr_nmdesc, *buf_nmdesc; > > const void *src; > > void *dst; > > > > @@ -3274,10 +3274,10 @@ static u32 idpf_rx_hsplit_wa(const struct libeth_fqe *hdr, > > !libeth_rx_sync_for_cpu(buf, copy)) > > return 0; > > > > - hdr_page = __netmem_to_page(hdr->netmem); > > - buf_page = __netmem_to_page(buf->netmem); > > - dst = page_address(hdr_page) + hdr->offset + hdr_page->pp->p.offset; > > - src = page_address(buf_page) + buf->offset + buf_page->pp->p.offset; > > + hdr_nmdesc = __netmem_to_nmdesc(hdr->netmem); > > + buf_nmdesc = __netmem_to_nmdesc(buf->netmem); > > + dst = nmdesc_address(hdr_nmdesc) + hdr->offset + hdr_nmdesc->pp->p.offset; > > + src = nmdesc_address(buf_nmdesc) + buf->offset + buf_nmdesc->pp->p.offset; > > > > memcpy(dst, src, LARGEST_ALIGN(copy)); > > buf->offset += copy; > -- > Pavel Begunkov