io_uring/net: only consider msg_inq if larger than 1

JIRA: https://issues.redhat.com/browse/RHEL-106845

commit 2c7f023
Author: Jens Axboe <axboe@kernel.dk>
Date:   Wed May 28 13:45:44 2025 -0600

    io_uring/net: only consider msg_inq if larger than 1

    Currently retry and general validity of msg_inq is gated on it being
    larger than zero, but it's entirely possible for this to be slightly
    inaccurate. In particular, if FIN is received, it'll return 1.

    Just use larger than 1 as the check. This covers both the FIN case, and
    at the same time, it doesn't make much sense to retry a recv immediately
    if there's even just a single 1 byte of valid data in the socket.

    Leave the SOCK_NONEMPTY flagging when larger than 0 still, as an app may
    use that for the final receive.

    Cc: stable@vger.kernel.org
    Reported-by: Christian Mazakas <christian.mazakas@gmail.com>
    Fixes: 7c71a0a ("io_uring/net: improve recv bundles")
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Ming Lei <ming.lei@redhat.com>

Author: Ming Lei

io_uring/net.c

@@ -831,7 +831,7 @@ static inline bool io_recv_finish(struct io_kiocb *req, int *ret,
 		 * If more is available AND it was a full transfer, retry and
 		 * append to this one
 		 */
-		if (!sr->retry && kmsg->msg.msg_inq > 0 && this_ret > 0 &&
+		if (!sr->retry && kmsg->msg.msg_inq > 1 && this_ret > 0 &&
 		    !iov_iter_count(&kmsg->msg.msg_iter)) {
 			req->cqe.flags = cflags & ~CQE_F_MASK;
 			sr->len = kmsg->msg.msg_inq;
@@ -1068,7 +1068,7 @@ static int io_recv_buf_select(struct io_kiocb *req, struct io_async_msghdr *kmsg
 			arg.mode |= KBUF_MODE_FREE;
 		}
 
-		if (kmsg->msg.msg_inq > 0)
+		if (kmsg->msg.msg_inq > 1)
 			arg.max_len = min_not_zero(sr->len, kmsg->msg.msg_inq);
 
 		ret = io_buffers_peek(req, &arg);