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([2620:10d:c092:600::1:f749]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ae6e7f2aa1asm795946066b.71.2025.07.14.02.42.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Jul 2025 02:42:05 -0700 (PDT) Message-ID: <5ee839d6-2734-41c5-b34c-8d686c910bc8@gmail.com> Date: Mon, 14 Jul 2025 10:43:35 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v9 2/8] netmem: introduce utility APIs to use struct netmem_desc To: Byungchul Park 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 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> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <20250713230752.GA7758@system.software.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 05393180008 X-Stat-Signature: 35466g65s6nzwe1n1x5dtuyh4cd1buf7 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1752486127-295678 X-HE-Meta: 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 H7V4v1lT 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 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 7/14/25 00:07, Byungchul Park wrote: > On Sat, Jul 12, 2025 at 12:59:34PM +0100, Pavel Begunkov wrote: >> On 7/10/25 09:28, Byungchul Park wrote: >> ...> + >>> static inline struct net_iov *netmem_to_net_iov(netmem_ref netmem) >>> { >>> if (netmem_is_net_iov(netmem)) >>> @@ -314,6 +340,21 @@ static inline netmem_ref netmem_compound_head(netmem_ref netmem) >>> return page_to_netmem(compound_head(netmem_to_page(netmem))); >>> } >>> >>> +#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. > 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