On 02/19/2020 12:31 AM, Hou Pu wrote:
> Nbd server with multiple connections could be upgraded since
> 560bc4b (nbd: handle dead connections). But if only one conncection
> is configured, after we take down nbd server, all inflight IO
> would finally timeout and return error. We could requeue them
> like what we do with multiple connections and wait for new socket
> in submit path.
>
> Signed-off-by: Hou Pu <houpu@xxxxxxxxxxxxx>
> ---
> drivers/block/nbd.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 78181908f0df..8e348c9c49a4 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -395,16 +395,19 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
> }
> config = nbd->config;
>
> - if (config->num_connections > 1) {
> + if (config->num_connections > 1 ||
> + (config->num_connections == 1 && nbd->tag_set.timeout)) {
> dev_err_ratelimited(nbd_to_dev(nbd),
> "Connection timed out, retrying (%d/%d alive)\n",
> atomic_read(&config->live_connections),
> config->num_connections);
> /*
> * Hooray we have more connections, requeue this IO, the submit
> - * path will put it on a real connection.
> + * path will put it on a real connection. Or if only one
> + * connection is configured, the submit path will wait util
> + * a new connection is reconfigured or util dead timeout.
> */
> - if (config->socks && config->num_connections > 1) {
> + if (config->socks) {
> if (cmd->index < config->num_connections) {
> struct nbd_sock *nsock =
> config->socks[cmd->index];
> @@ -747,8 +750,7 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
> * and let the timeout stuff handle resubmitting
> * this request onto another connection.
> */
> - if (nbd_disconnected(config) ||
> - config->num_connections <= 1) {
> + if (nbd_disconnected(config)) {
I think you need to update the comment right above this chunk. It still
mentions num_connections=1 working differently.
> cmd->status = BLK_STS_IOERR;
> goto out;
> }
> @@ -825,7 +827,7 @@ static int find_fallback(struct nbd_device *nbd, int index)
>
> if (config->num_connections <= 1) {
> dev_err_ratelimited(disk_to_dev(nbd->disk),
> - "Attempted send on invalid socket\n");
> + "Dead connection, failed to find a fallback\n");
> return new_index;
> }
>
>
