| Message ID | 7854000d2ce5ac32b75782a7c4574f25a11b573d.1689757133.git.jstancek@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | splice, net: Fix splice_to_socket() for O_NONBLOCK socket | expand |
Jan Stancek <jstancek@redhat.com> 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. Does this actually work correctly in all circumstances? The problem might come if you have a splice from a non-rewindable source through a temporary pipe (eg. sendfile() using splice_direct_to_actor()). David
On Mon, Jul 24, 2023 at 12:12 PM David Howells <dhowells@redhat.com> wrote: > > Jan Stancek <jstancek@redhat.com> 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. > > Does this actually work correctly in all circumstances? > > The problem might come if you have a splice from a non-rewindable source > through a temporary pipe (eg. sendfile() using splice_direct_to_actor()). I assumed this was safe, since sendfile / splice_direct_to_actor() requires input to be seekable.
Jan Stancek <jstancek@redhat.com> wrote: > On Mon, Jul 24, 2023 at 12:12 PM David Howells <dhowells@redhat.com> wrote: > > > > Jan Stancek <jstancek@redhat.com> 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. > > > > Does this actually work correctly in all circumstances? > > > > The problem might come if you have a splice from a non-rewindable source > > through a temporary pipe (eg. sendfile() using splice_direct_to_actor()). > > I assumed this was safe, since sendfile / splice_direct_to_actor() > requires input to be seekable. Ah! The test isn't where I was looking for it (in sendfile()) - it's in splice_direct_to_actor(). I wonder if it's worth making that explicit in do_sendfile() as the requirement doesn't hold if the output is a pipe (though in such a case, there's an explicit buffer, so it's not actually a problem). Anyway, did you want to post this to netdev too so that the networking tree picks it up? Feel free to add: Acked-by: David Howells <dhowells@redhat.com>
On Mon, 24 Jul 2023 16:44:07 +0100 David Howells wrote: > Anyway, did you want to post this to netdev too so that the networking tree > picks it up? Feel free to add: +1, no preference which tree this goes thru, but if no one else claims it please repost CCing netdev@vger.kernel.org
On Mon, Jul 24, 2023 at 7:09 PM Jakub Kicinski <kuba@kernel.org> wrote: > > On Mon, 24 Jul 2023 16:44:07 +0100 David Howells wrote: > > Anyway, did you want to post this to netdev too so that the networking tree > > picks it up? Feel free to add: > > +1, no preference which tree this goes thru, but if no one else claims > it please repost CCing netdev@vger.kernel.org I'll repost, thanks.
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);
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()") Signed-off-by: Jan Stancek <jstancek@redhat.com> --- fs/splice.c | 2 ++ 1 file changed, 2 insertions(+)