Re: [PATCH 2/7] scsi: target: core: Add RTPI field to target port

[Mike Christie <michael.christie@oracle.com>]

On 9/6/22 10:45 AM, Dmitry Bogdanov wrote:
> From: Roman Bolshakov <r.bolshakov@yadro.com>
> 
> SAM-5 4.6.5.2 (Relative Port Identifier attribute) defines the attribute
> as unique across SCSI target ports.
> 
> The change introduces RTPI attribute to se_portal group. The value is
> auto-incremented and unique across all SCSI target ports. It also limits
> number of SCSI target ports to 65535.
> 
> Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
> Signed-off-by: Dmitry Bogdanov <d.bogdanov@yadro.com>
> ---
>  drivers/target/target_core_tpg.c  | 78 +++++++++++++++++++++++++++++--
>  include/target/target_core_base.h |  4 ++
>  2 files changed, 77 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
> index f0d38d77edcc..325ef439fb42 100644
> --- a/drivers/target/target_core_tpg.c
> +++ b/drivers/target/target_core_tpg.c
> @@ -31,6 +31,10 @@
>  #include "target_core_ua.h"
>  
>  extern struct se_device *g_lun0_dev;
> +static u16 g_tpg_count;
> +static u16 g_tpg_rtpi_counter = 1;
> +static LIST_HEAD(g_tpg_list);
> +static DEFINE_SPINLOCK(g_tpg_lock);
>  
>  /*	__core_tpg_get_initiator_node_acl():
>   *
> @@ -439,6 +443,57 @@ static void core_tpg_lun_ref_release(struct percpu_ref *ref)
>  	complete(&lun->lun_shutdown_comp);
>  }
>  
> +static int core_tpg_register_rtpi(struct se_portal_group *se_tpg)
> +{
> +	struct se_portal_group *tpg;
> +
> +	/*
> +	 * Allocate the next RELATIVE TARGET PORT IDENTIFIER.
> +	 * Here is the table from SPC-4 4.3.4:
> +	 *
> +	 *    Table 34 -- Relative target port identifier values
> +	 *
> +	 * Value		Description
> +	 * 0h			Reserved
> +	 * 1h			Relative port 1, historically known as port A
> +	 * 2h			Relative port 2, historically known as port B
> +	 * 3h to FFFFh		Relative port 3 through 65 535
> +	 */
> +	spin_lock(&g_tpg_lock);
> +
> +	if (g_tpg_count == 0xffff) {
> +		spin_unlock(&g_tpg_lock);
> +		pr_warn("Reached g_tpg_count == 0xffff\n");
> +		return -ENOSPC;
> +	}
> +again:
> +	se_tpg->tpg_rtpi = g_tpg_rtpi_counter++;
> +	if (!se_tpg->tpg_rtpi)
> +		goto again;
> +
> +	list_for_each_entry(tpg, &g_tpg_list, tpg_list) {
> +		/*
> +		 * Make sure RELATIVE TARGET PORT IDENTIFIER is unique
> +		 * for 16-bit wrap..
> +		 */
> +		if (se_tpg->tpg_rtpi == tpg->tpg_rtpi)
> +			goto again;
> +	}
> +	list_add(&se_tpg->tpg_list, &g_tpg_list);
> +	g_tpg_count++;
> +	spin_unlock(&g_tpg_lock);
> +

I think you could just use an ida.