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

[Xi Ruoyao]

On Mon, 2023-07-24 at 19:39 +0200, Jan Stancek wrote:
> 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@xxxxxxxxxx>
> Signed-off-by: Jan Stancek <jstancek@xxxxxxxxxx>

This issue caused the "test_asyncio" test in Python 3 test suite to hang
indefinitely.  I can confirm this patch fixes the issue.

Tested-by: Xi Ruoyao <xry111@xxxxxxxxxxx>

> ---
> 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);

-- 
Xi Ruoyao <xry111@xxxxxxxxxxx>
School of Aerospace Science and Technology, Xidian University