[PATCH] splice, net: avoid MSG_MORE when the bvec array fills

[Avi Weiss]

splice_to_socket() leaves tail at the last included pipe buffer when
its 16-entry bvec array fills. If the requested length exceeds the
available pipe data, pipe_occupancy() counts that buffer again and sets
MSG_MORE even though the pipe is empty. Small TCP transfers can then be
delayed until the cork timeout expires.

Advance tail before checking the array limit so the occupancy test
counts only pipe buffers that have not been included in the send.

Fixes: ca2d49f77ce4 ("splice, net: Fix splice_to_socket() to handle pipe bufs larger than a page")
Signed-off-by: Avi Weiss <thnkslprpt@xxxxxxxxx>
---
 fs/splice.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/splice.c b/fs/splice.c
index bc243ab8dc43..7c67e0375ae2 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -863,9 +863,9 @@ ssize_t splice_to_socket(struct pipe_inode_info *pipe, struct file *out,
 
 			bvec_set_page(&bvec[bc++], buf->page, seg, buf->offset);
 			remain -= seg;
+			tail++;
 			if (remain == 0 || bc >= ARRAY_SIZE(bvec))
 				break;
-			tail++;
 		}
 
 		if (!bc)
-- 
2.43.0