Re: [PATCH for-7.1 3/8] nbd: remove peppering of nbd_client_connected

[Eric Blake]

On Tue, Apr 12, 2022 at 09:41:59PM +0200, Paolo Bonzini wrote:
> It is unnecessary to check nbd_client_connected() because every time
> s->state is moved out of NBD_CLIENT_CONNECTED the socket is shut down
> and all coroutines are resumed.
> 
> The only case where it was actually needed is when the NBD
> server disconnects and there is no reconnect-delay.  In that
> case, nbd_receive_replies() does not set s->reply.handle and
> nbd_co_do_receive_one_chunk() cannot continue.  For that one case,
> check the return value of nbd_receive_replies().
> 
> As to the others:
> 
> * nbd_receive_replies() can put the current coroutine to sleep if another
> reply is ongoing; then it will be woken by nbd_channel_error() called
> by the ongoing reply.  Or it can try itself to read a reply header and
> fail, thus calling nbd_channel_error() itself.
> 
> * nbd_co_send_request() will write the body of the request and fail
> 
> * nbd_reply_chunk_iter_receive() will call nbd_co_receive_one_chunk()
> and then nbd_co_do_receive_one_chunk(), which will handle the failure as
> above; or it will just detect a previous call to nbd_iter_channel_error()
> via iter->ret < 0.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  block/nbd.c | 17 ++++-------------
>  1 file changed, 4 insertions(+), 13 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
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