netdev - [PATCH] net: micro-optimize skb_datagram

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Date: Thu, 13 Jun 2024 14:35:04 +0300
From: Sagi Grimberg <sagi@...mberg.me>
To: netdev@...r.kernel.org
Cc: Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH] net: micro-optimize skb_datagram_iter

We only use the mapping in a single context in a short and contained scope,
so kmap_local_page is sufficient and cheaper. This will also allow
skb_datagram_iter to be called from softirq context.

Signed-off-by: Sagi Grimberg <sagi@...mberg.me>
---
 net/core/datagram.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/datagram.c b/net/core/datagram.c
index a8b625abe242..ac74df248205 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -436,14 +436,14 @@ static int __skb_datagram_iter(const struct sk_buff *skb, int offset,
 		end = start + skb_frag_size(frag);
 		if ((copy = end - offset) > 0) {
 			struct page *page = skb_frag_page(frag);
-			u8 *vaddr = kmap(page);
+			u8 *vaddr = kmap_local_page(page);
 
 			if (copy > len)
 				copy = len;
 			n = INDIRECT_CALL_1(cb, simple_copy_to_iter,
 					vaddr + skb_frag_off(frag) + offset - start,
 					copy, data, to);
-			kunmap(page);
+			kunmap_local(vaddr);
 			offset += n;
 			if (n != copy)
 				goto short_copy;
-- 
2.43.0