[PATCH v2] splice, net: Fix splice_to_socket() for O_NONBLOCK socket

[Jan Stancek <jstancek@redhat.com>]

LTP sendfile07 [1], which expects sendfile() to return EAGAIN when
transferring data from regular file to a "full" O_NONBLOCK socket,
started failing after commit 2dc334f1a63a ("splice, net: Use
sendmsg(MSG_SPLICE_PAGES) rather than ->sendpage()").
sendfile() no longer immediately returns, but now blocks.

Removed sock_sendpage() handled this case by setting a MSG_DONTWAIT
flag, fix new splice_to_socket() to do the same for O_NONBLOCK sockets.

[1] https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/sendfile/sendfile07.c

Fixes: 2dc334f1a63a ("splice, net: Use sendmsg(MSG_SPLICE_PAGES) rather than ->sendpage()")
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Jan Stancek <jstancek@redhat.com>
---
Changes in v2:
- add David's Acked-by
- add netdev list

 fs/splice.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/splice.c b/fs/splice.c
index 004eb1c4ce31..3e2a31e1ce6a 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -876,6 +876,8 @@ ssize_t splice_to_socket(struct pipe_inode_info *pipe, struct file *out,
 			msg.msg_flags |= MSG_MORE;
 		if (remain && pipe_occupancy(pipe->head, tail) > 0)
 			msg.msg_flags |= MSG_MORE;
+		if (out->f_flags & O_NONBLOCK)
+			msg.msg_flags |= MSG_DONTWAIT;
 
 		iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, bvec, bc,
 			      len - remain);
-- 
2.31.1