[PATCH 3/4] nvmet: include all configured ports in the discovery log page

[Sagi Grimberg]

On 4/20/22 12:27, Hannes Reinecke wrote:
> When a per-port discovery subsystem is used we should include
> all configured ports in the discovery log page, not just that one
> through which the controller was connected.
> 
> - /
>    o- ports
>    | o- 1 .. [trtype=tcp, traddr=127.0.0.1, trsvcid=8009]
>    | | o- subsystems
>    | |   o- nqn.discovery
>    | o- 2 .. [trtype=tcp, traddr=127.0.0.1, trsvcid=4420]
>    | | o- subsystems
>    | |   o- nqn.discovery
>    | |   o- nqn.io-1
>    | o- 3 .. [trtype=tcp, traddr=127.0.0.1, trsvcid=4421]
>    |   o- subsystems
>    |     o- nqn.io-2
>    o- subsystems
>      o- nqn.discovery
>      o- nqn.io-1
>      | o- namespaces
>      o- nqn.io-2
>        o- namespaces
> 
> A discovery on port 8009 will return information about
> - nqn.discovery at port 8009
> - nqn.discovery at port 4420
> - nqn.io-1 at port 4420
> A discovery on port 4420 will return the same information.
> A discovery on port 4421 will return information about
> - standard discovery subsystem on port 4421
> - nqn.io-2 on port 4421
> 
> Signed-off-by: Hannes Reinecke <hare at suse.de>
> ---
>   drivers/nvme/target/discovery.c | 53 +++++++++++++++++++++++++++------
>   1 file changed, 44 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/nvme/target/discovery.c b/drivers/nvme/target/discovery.c
> index 6b8aa6c4e752..ea8fce538342 100644
> --- a/drivers/nvme/target/discovery.c
> +++ b/drivers/nvme/target/discovery.c
> @@ -149,6 +149,30 @@ static void nvmet_set_disc_traddr(struct nvmet_req *req, struct nvmet_port *port
>   		memcpy(traddr, port->disc_addr.traddr, NVMF_TRADDR_SIZE);
>   }
>   
> +/*
> + * discovery_port_match - filter eligible ports for discovery log page
> + *
> + * If the port through which the controller is connected has no discovery
> + * subsystem linked, use the original behaviour of just including information
> + * about that port in the discovery log page.
> + * Otherwise include information about all ports into which the specified
> + * discovery subsystem is linked.
> + */
> +
> +static bool discovery_port_match(struct nvmet_req *req, struct nvmet_port *r)
> +{
> +	struct nvmet_ctrl *ctrl = req->sq->ctrl;
> +
> +	if (!req->port->disc_subsys) {
> +		if (r != req->port)
> +			return false;
> +	} else {
> +		if (ctrl->subsys != r->disc_subsys)
> +			return false;

What is this condition for? What is this filtering out?