Changes from RFC v2: 1. Add a Reviewed-by tag (Thanks to Mina) 2. Rebase on main branch as of Sep 22 Changes from RFC: 1. Optimize the implementation of netmem_to_nmdesc to use less instructions (feedbacked by Pavel) --->8--- From 01d23fc4b20c369a2ecf29dc92319d55a4e63aa2 Mon Sep 17 00:00:00 2001 From: Byungchul Park Date: Tue, 29 Jul 2025 19:34:12 +0900 Subject: [PATCH net-next v3] netmem: replace __netmem_clear_lsb() with netmem_to_nmdesc() Now that we have struct netmem_desc, it'd better access the pp fields via struct netmem_desc rather than struct net_iov. Introduce netmem_to_nmdesc() for safely converting netmem_ref to netmem_desc regardless of the type underneath e.i. netmem_desc, net_iov. While at it, remove __netmem_clear_lsb() and make netmem_to_nmdesc() used instead. Suggested-by: Pavel Begunkov Signed-off-by: Byungchul Park Reviewed-by: Mina Almasry --- include/net/netmem.h | 66 +++++++++++++++++++++--------------------- net/core/netmem_priv.h | 16 +++++----- 2 files changed, 41 insertions(+), 41 deletions(-) diff --git a/include/net/netmem.h b/include/net/netmem.h index f7dacc9e75fd..651e2c62d1dd 100644 --- a/include/net/netmem.h +++ b/include/net/netmem.h @@ -247,6 +247,23 @@ static inline unsigned long netmem_pfn_trace(netmem_ref netmem) return page_to_pfn(netmem_to_page(netmem)); } +/* XXX: How to extract netmem_desc from page must be changed, once + * netmem_desc no longer overlays on page and will be allocated through + * slab. + */ +#define __pp_page_to_nmdesc(p) (_Generic((p), \ + const struct page * : (const struct netmem_desc *)(p), \ + struct page * : (struct netmem_desc *)(p))) + +/* CAUTION: Check if the page is a pp page before calling this helper or + * know it's a pp page. + */ +#define pp_page_to_nmdesc(p) \ +({ \ + DEBUG_NET_WARN_ON_ONCE(!page_pool_page_is_pp(p)); \ + __pp_page_to_nmdesc(p); \ +}) + /** * __netmem_to_nmdesc - unsafely get pointer to the &netmem_desc backing * @netmem @@ -265,42 +282,25 @@ static inline struct netmem_desc *__netmem_to_nmdesc(netmem_ref netmem) return (__force struct netmem_desc *)netmem; } -/* __netmem_clear_lsb - convert netmem_ref to struct net_iov * for access to - * common fields. - * @netmem: netmem reference to extract as net_iov. - * - * All the sub types of netmem_ref (page, net_iov) have the same pp, pp_magic, - * dma_addr, and pp_ref_count fields at the same offsets. Thus, we can access - * these fields without a type check to make sure that the underlying mem is - * net_iov or page. +/* netmem_to_nmdesc - convert netmem_ref to struct netmem_desc * for + * access to common fields. + * @netmem: netmem reference to get netmem_desc. * - * The resulting value of this function can only be used to access the fields - * that are NET_IOV_ASSERT_OFFSET'd. Accessing any other fields will result in - * undefined behavior. + * All the sub types of netmem_ref (netmem_desc, net_iov) have the same + * pp, pp_magic, dma_addr, and pp_ref_count fields via netmem_desc. * - * Return: the netmem_ref cast to net_iov* regardless of its underlying type. + * Return: the pointer to struct netmem_desc * regardless of its + * underlying type. */ -static inline struct net_iov *__netmem_clear_lsb(netmem_ref netmem) +static inline struct netmem_desc *netmem_to_nmdesc(netmem_ref netmem) { - return (struct net_iov *)((__force unsigned long)netmem & ~NET_IOV); -} + void *p = (void *)((__force unsigned long)netmem & ~NET_IOV); -/* XXX: How to extract netmem_desc from page must be changed, once - * netmem_desc no longer overlays on page and will be allocated through - * slab. - */ -#define __pp_page_to_nmdesc(p) (_Generic((p), \ - const struct page * : (const struct netmem_desc *)(p), \ - struct page * : (struct netmem_desc *)(p))) + if (netmem_is_net_iov(netmem)) + return &((struct net_iov *)p)->desc; -/* CAUTION: Check if the page is a pp page before calling this helper or - * know it's a pp page. - */ -#define pp_page_to_nmdesc(p) \ -({ \ - DEBUG_NET_WARN_ON_ONCE(!page_pool_page_is_pp(p)); \ - __pp_page_to_nmdesc(p); \ -}) + return __pp_page_to_nmdesc((struct page *)p); +} /** * __netmem_get_pp - unsafely get pointer to the &page_pool backing @netmem @@ -320,12 +320,12 @@ static inline struct page_pool *__netmem_get_pp(netmem_ref netmem) static inline struct page_pool *netmem_get_pp(netmem_ref netmem) { - return __netmem_clear_lsb(netmem)->pp; + return netmem_to_nmdesc(netmem)->pp; } static inline atomic_long_t *netmem_get_pp_ref_count_ref(netmem_ref netmem) { - return &__netmem_clear_lsb(netmem)->pp_ref_count; + return &netmem_to_nmdesc(netmem)->pp_ref_count; } static inline bool netmem_is_pref_nid(netmem_ref netmem, int pref_nid) @@ -390,7 +390,7 @@ static inline bool netmem_is_pfmemalloc(netmem_ref netmem) static inline unsigned long netmem_get_dma_addr(netmem_ref netmem) { - return __netmem_clear_lsb(netmem)->dma_addr; + return netmem_to_nmdesc(netmem)->dma_addr; } void get_netmem(netmem_ref netmem); diff --git a/net/core/netmem_priv.h b/net/core/netmem_priv.h index cd95394399b4..23175cb2bd86 100644 --- a/net/core/netmem_priv.h +++ b/net/core/netmem_priv.h @@ -5,19 +5,19 @@ static inline unsigned long netmem_get_pp_magic(netmem_ref netmem) { - return __netmem_clear_lsb(netmem)->pp_magic & ~PP_DMA_INDEX_MASK; + return netmem_to_nmdesc(netmem)->pp_magic & ~PP_DMA_INDEX_MASK; } static inline void netmem_or_pp_magic(netmem_ref netmem, unsigned long pp_magic) { - __netmem_clear_lsb(netmem)->pp_magic |= pp_magic; + netmem_to_nmdesc(netmem)->pp_magic |= pp_magic; } static inline void netmem_clear_pp_magic(netmem_ref netmem) { - WARN_ON_ONCE(__netmem_clear_lsb(netmem)->pp_magic & PP_DMA_INDEX_MASK); + WARN_ON_ONCE(netmem_to_nmdesc(netmem)->pp_magic & PP_DMA_INDEX_MASK); - __netmem_clear_lsb(netmem)->pp_magic = 0; + netmem_to_nmdesc(netmem)->pp_magic = 0; } static inline bool netmem_is_pp(netmem_ref netmem) @@ -27,13 +27,13 @@ static inline bool netmem_is_pp(netmem_ref netmem) static inline void netmem_set_pp(netmem_ref netmem, struct page_pool *pool) { - __netmem_clear_lsb(netmem)->pp = pool; + netmem_to_nmdesc(netmem)->pp = pool; } static inline void netmem_set_dma_addr(netmem_ref netmem, unsigned long dma_addr) { - __netmem_clear_lsb(netmem)->dma_addr = dma_addr; + netmem_to_nmdesc(netmem)->dma_addr = dma_addr; } static inline unsigned long netmem_get_dma_index(netmem_ref netmem) @@ -43,7 +43,7 @@ static inline unsigned long netmem_get_dma_index(netmem_ref netmem) if (WARN_ON_ONCE(netmem_is_net_iov(netmem))) return 0; - magic = __netmem_clear_lsb(netmem)->pp_magic; + magic = netmem_to_nmdesc(netmem)->pp_magic; return (magic & PP_DMA_INDEX_MASK) >> PP_DMA_INDEX_SHIFT; } @@ -57,6 +57,6 @@ static inline void netmem_set_dma_index(netmem_ref netmem, return; magic = netmem_get_pp_magic(netmem) | (id << PP_DMA_INDEX_SHIFT); - __netmem_clear_lsb(netmem)->pp_magic = magic; + netmem_to_nmdesc(netmem)->pp_magic = magic; } #endif base-commit: 312e6f7676e63bbb9b81e5c68e580a9f776cc6f0 -- 2.17.1