From dcfea72e79b0aa7a057c8f6024169d86a1bbc84b Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 8 Jan 2020 16:59:02 -0500 Subject: [PATCH] net: introduce skb_list_walk_safe for skb segment walking As part of the continual effort to remove direct usage of skb->next and skb->prev, this patch adds a helper for iterating through the singly-linked variant of skb lists, which are used for lists of GSO packet. The name "skb_list_..." has been chosen to match the existing function, "kfree_skb_list, which also operates on these singly-linked lists, and the "..._walk_safe" part is the same idiom as elsewhere in the kernel. This patch removes the helper from wireguard and puts it into linux/skbuff.h, while making it a bit more robust for general usage. In particular, parenthesis are added around the macro argument usage, and it now accounts for trying to iterate through an already-null skb pointer, which will simply run the iteration zero times. This latter enhancement means it can be used to replace both do { ... } while and while (...) open-coded idioms. This should take care of these three possible usages, which match all current methods of iterations. skb_list_walk_safe(segs, skb, next) { ... } skb_list_walk_safe(skb, skb, next) { ... } skb_list_walk_safe(segs, skb, segs) { ... } Gcc appears to generate efficient code for each of these. Signed-off-by: Jason A. Donenfeld Signed-off-by: David S. Miller --- drivers/net/wireguard/device.h | 8 -------- include/linux/skbuff.h | 5 +++++ 2 files changed, 5 insertions(+), 8 deletions(-) diff --git a/drivers/net/wireguard/device.h b/drivers/net/wireguard/device.h index c91f3051c5c7..b15a8be9d816 100644 --- a/drivers/net/wireguard/device.h +++ b/drivers/net/wireguard/device.h @@ -62,12 +62,4 @@ struct wg_device { int wg_device_init(void); void wg_device_uninit(void); -/* Later after the dust settles, this can be moved into include/linux/skbuff.h, - * where virtually all code that deals with GSO segs can benefit, around ~30 - * drivers as of writing. - */ -#define skb_list_walk_safe(first, skb, next) \ - for (skb = first, next = skb->next; skb; \ - skb = next, next = skb ? skb->next : NULL) - #endif /* _WG_DEVICE_H */ diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index e9133bcf0544..64e5b1be9ff5 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1478,6 +1478,11 @@ static inline void skb_mark_not_on_list(struct sk_buff *skb) skb->next = NULL; } +/* Iterate through singly-linked GSO fragments of an skb. */ +#define skb_list_walk_safe(first, skb, next) \ + for ((skb) = (first), (next) = (skb) ? (skb)->next : NULL; (skb); \ + (skb) = (next), (next) = (skb) ? (skb)->next : NULL) + static inline void skb_list_del_init(struct sk_buff *skb) { __list_del_entry(&skb->list); -- 2.11.0