io_uring/net: don't retry recvmsg() unnecessarily

If we're doing multishot receives, then we always end up doing two trips
through sock_recvmsg(). For protocols that sanely set msghdr->msg_inq,
then we don't need to waste time picking a new buffer and attempting a
new receive if there's nothing there.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/net.c b/io_uring/net.c
index 9e00347..0795f37 100644 (file)
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -635,7 +635,15 @@ static inline bool io_recv_finish(struct io_kiocb *req, int *ret,
                if (io_aux_cqe(req->ctx, issue_flags & IO_URING_F_COMPLETE_DEFER,
                               req->cqe.user_data, *ret, cflags | IORING_CQE_F_MORE, true)) {
                        io_recv_prep_retry(req);
-                       return false;
+                       /* Known not-empty or unknown state, retry */
+                       if (cflags & IORING_CQE_F_SOCK_NONEMPTY ||
+                           msg->msg_inq == -1U)
+                               return false;
+                       if (issue_flags & IO_URING_F_MULTISHOT)
+                               *ret = IOU_ISSUE_SKIP_COMPLETE;
+                       else
+                               *ret = -EAGAIN;
+                       return true;
                }
                /* Otherwise stop multishot but use the current result. */
        }