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@grimberg.me>
Link: https://lore.kernel.org/r/20240613113504.1079860-1-sagi@grimberg.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/datagram.c b/net/core/datagram.c
index e614cfd8e14a50a08c764dfed30c2e0838413a93..95f242591fd23c22ca397d21939e230d37cec9ff 100644 (file)
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -417,14 +417,14 @@ 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;