Trivial fix to a couple of outdated netmem comments. No code changes, just more accurately describing current code.
Signed-off-by: Mina Almasry <almasrym...@google.com> --- v2: https://lore.kernel.org/netdev/20250613042804.3259045-2-almasrym...@google.com/ - Adjust comment for clearing lsb as (Jakub) --- include/net/netmem.h | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/include/net/netmem.h b/include/net/netmem.h index 386164fb9c18..850869b45b45 100644 --- a/include/net/netmem.h +++ b/include/net/netmem.h @@ -89,8 +89,7 @@ static inline unsigned int net_iov_idx(const struct net_iov *niov) * typedef netmem_ref - a nonexistent type marking a reference to generic * network memory. * - * A netmem_ref currently is always a reference to a struct page. This - * abstraction is introduced so support for new memory types can be added. + * A netmem_ref can be a struct page* or a struct net_iov* underneath. * * Use the supplied helpers to obtain the underlying memory pointer and fields. */ @@ -117,9 +116,6 @@ static inline struct page *__netmem_to_page(netmem_ref netmem) return (__force struct page *)netmem; } -/* This conversion fails (returns NULL) if the netmem_ref is not struct page - * backed. - */ static inline struct page *netmem_to_page(netmem_ref netmem) { if (WARN_ON_ONCE(netmem_is_net_iov(netmem))) @@ -178,6 +174,21 @@ static inline unsigned long netmem_pfn_trace(netmem_ref netmem) return page_to_pfn(netmem_to_page(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. + * + * 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. + * + * Return: the netmem_ref cast to net_iov* regardless of its underlying type. + */ static inline struct net_iov *__netmem_clear_lsb(netmem_ref netmem) { return (struct net_iov *)((__force unsigned long)netmem & ~NET_IOV); base-commit: 8909f5f4ecd551c2299b28e05254b77424c8c7dc -- 2.50.0.rc1.591.g9c95f17f64-goog
