io_uring/net: wire up IORING_CQE_F_SOCK_NONEMPTY for accept

If the given protocol supports passing back whether or not we had more
pending accept post this one, pass back this information to userspace.
This is done by setting IORING_CQE_F_SOCK_NONEMPTY in the CQE flags,
just like we do for recv/recvmsg if there's more data available post
a receive operation.

We can also use this information to be smarter about multishot retry,
as we don't need to do a pointless retry if we know for a fact that
there aren't any more connections to accept.

Suggested-by: Norman Maurer <norman_maurer@apple.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/net.c b/io_uring/net.c
index d4d1fc93635cbf0c323fb5dd350f6470878e42dc..0a48596429d9f53edd252a58435619654f7ee7a0 100644 (file)
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -1533,6 +1533,7 @@ int io_accept(struct io_kiocb *req, unsigned int issue_flags)
                .flags = force_nonblock ? O_NONBLOCK : 0,
        };
        struct file *file;
+       unsigned cflags;
        int ret, fd;
 
        if (!(req->flags & REQ_F_POLLED) &&
@@ -1545,6 +1546,8 @@ retry:
                if (unlikely(fd < 0))
                        return fd;
        }
+       arg.err = 0;
+       arg.is_empty = -1;
        file = do_accept(req->file, &arg, accept->addr, accept->addr_len,
                         accept->flags);
        if (IS_ERR(file)) {
@@ -1573,17 +1576,26 @@ retry:
                                                accept->file_slot);
        }
 
+       cflags = 0;
+       if (!arg.is_empty)
+               cflags |= IORING_CQE_F_SOCK_NONEMPTY;
+
        if (!(req->flags & REQ_F_APOLL_MULTISHOT)) {
-               io_req_set_res(req, ret, 0);
+               io_req_set_res(req, ret, cflags);
                return IOU_OK;
        }
 
        if (ret < 0)
                return ret;
-       if (io_req_post_cqe(req, ret, IORING_CQE_F_MORE))
-               goto retry;
+       if (io_req_post_cqe(req, ret, cflags | IORING_CQE_F_MORE)) {
+               if (cflags & IORING_CQE_F_SOCK_NONEMPTY || arg.is_empty == -1)
+                       goto retry;
+               if (issue_flags & IO_URING_F_MULTISHOT)
+                       return IOU_ISSUE_SKIP_COMPLETE;
+               return -EAGAIN;
+       }
 
-       io_req_set_res(req, ret, 0);
+       io_req_set_res(req, ret, cflags);
        return IOU_STOP_MULTISHOT;
 }