net: avoid one loop iteration in __skb_splice_bits

[PATCH net-next v5] net: avoid one loop iteration in __skb_splice_bits

Posted by Pengtao He 1 month, 2 weeks ago

If *len is equal to 0 at the beginning of __splice_segment
it returns true directly. But when decreasing *len from
a positive number to 0 in __splice_segment, it returns false.
The __skb_splice_bits needs to call __splice_segment again.

Recheck *len if it changes, return true in time.
Reduce unnecessary calls to __splice_segment.

Signed-off-by: Pengtao He <hept.hept.hept@gmail.com>
---
v5:
Correct the summary phrase.
v4:
Correct the commit message.
v3:
Reduce once condition evaluation.
v2:
Correct the commit message and target tree.
v1:
https://lore.kernel.org/netdev/20250723063119.24059-1-hept.hept.hept@gmail.com/
---
 net/core/skbuff.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index ee0274417948..23b776cd9879 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3112,7 +3112,9 @@ static bool __splice_segment(struct page *page, unsigned int poff,
 		poff += flen;
 		plen -= flen;
 		*len -= flen;
-	} while (*len && plen);
+		if (!*len)
+			return true;
+	} while (plen);
 
 	return false;
 }
-- 
2.49.0

Re: [PATCH net-next v5] net: avoid one loop iteration in __skb_splice_bits

Posted by Willem de Bruijn 1 month, 2 weeks ago

Pengtao He wrote:
> If *len is equal to 0 at the beginning of __splice_segment
> it returns true directly. But when decreasing *len from
> a positive number to 0 in __splice_segment, it returns false.
> The __skb_splice_bits needs to call __splice_segment again.
> 
> Recheck *len if it changes, return true in time.
> Reduce unnecessary calls to __splice_segment.
> 
> Signed-off-by: Pengtao He <hept.hept.hept@gmail.com>

Reviewed-by: Willem de Bruijn <willemb@google.com>