Re: [PATCH 4/6] scsi: pm8001: Use sas_task_find_rq() for tagging

Damien Le Moal
2022-09-29T02:17:51Z

On 9/28/22 21:27, John Garry wrote:
> The request associated with a scsi command coming from the block layer
> has a unique tag, so use that when possible for getting a CCB.
>
> Unfortunately we don't support reserved commands in the SCSI midlayer yet,
> so in the interim continue to manage those tags internally (along with
> tags for private commands).
>
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
> drivers/scsi/pm8001/pm8001_init.c | 10 ++++------
> drivers/scsi/pm8001/pm8001_sas.c | 8 ++++++++
> drivers/scsi/pm8001/pm8001_sas.h | 6 +++++-
> 3 files changed, 17 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/scsi/pm8001/pm8001_init.c b/drivers/scsi/pm8001/pm8001_init.c
> index 0edc9857a8bd..0868836e7391 100644
> --- a/drivers/scsi/pm8001/pm8001_init.c
> +++ b/drivers/scsi/pm8001/pm8001_init.c
> @@ -1208,17 +1208,14 @@ static int pm8001_init_ccb_tag(struct pm8001_hba_info *pm8001_ha)
> struct Scsi_Host *shost = pm8001_ha->shost;
> struct device *dev = pm8001_ha->dev;
> u32 max_out_io, ccb_count;
> - u32 can_queue;
> int i;
>
> max_out_io = pm8001_ha->main_cfg_tbl.pm80xx_tbl.max_out_io;
> ccb_count = min_t(int, PM8001_MAX_CCB, max_out_io);
>
> - /* Update to the scsi host*/
> - can_queue = ccb_count - PM8001_RESERVE_SLOT;
> - shost->can_queue = can_queue;
> + shost->can_queue = ccb_count - PM8001_RESERVE_SLOT;
>
> - pm8001_ha->tags = bitmap_zalloc(ccb_count, GFP_KERNEL);
> + pm8001_ha->tags = bitmap_zalloc(PM8001_RESERVE_SLOT, GFP_KERNEL);

The "tags" name for this field is really confusing as it seems to be
implying "all tags". Could we rename that to reserved_tags or similar ?

> if (!pm8001_ha->tags)
> goto err_out;
>
> @@ -1244,9 +1241,10 @@ static int pm8001_init_ccb_tag(struct pm8001_hba_info *pm8001_ha)
> pm8001_ha->ccb_info[i].task = NULL;
> pm8001_ha->ccb_info[i].ccb_tag = PM8001_INVALID_TAG;
> pm8001_ha->ccb_info[i].device = NULL;
> - ++pm8001_ha->tags_num;
> }
>
> + pm8001_ha->tags_num = PM8001_RESERVE_SLOT;

Same here. reserved_tags_num ?
But given that this seems to always be equal to PM8001_RESERVE_SLOT, do
we even need this field at all ?

> +
> return 0;
>
> err_out_noccb:
> diff --git a/drivers/scsi/pm8001/pm8001_sas.c b/drivers/scsi/pm8001/pm8001_sas.c
> index 066dfa9f4683..9d25855af657 100644
> --- a/drivers/scsi/pm8001/pm8001_sas.c
> +++ b/drivers/scsi/pm8001/pm8001_sas.c
> @@ -68,6 +68,11 @@ void pm8001_tag_free(struct pm8001_hba_info *pm8001_ha, u32 tag)
> void *bitmap = pm8001_ha->tags;
> unsigned long flags;
>
> + if (tag < pm8001_ha->shost->can_queue)
> + return;
> +
> + tag -= pm8001_ha->shost->can_queue;
> +
> spin_lock_irqsave(&pm8001_ha->bitmap_lock, flags);
> __clear_bit(tag, bitmap);
> spin_unlock_irqrestore(&pm8001_ha->bitmap_lock, flags);
> @@ -92,6 +97,9 @@ int pm8001_tag_alloc(struct pm8001_hba_info *pm8001_ha, u32 *tag_out)
> }
> __set_bit(tag, bitmap);
> spin_unlock_irqrestore(&pm8001_ha->bitmap_lock, flags);
> +
> + /* reserved tags are in the upper region of the tagset */
> + tag += pm8001_ha->shost->can_queue;
> *tag_out = tag;
> return 0;
> }
> diff --git a/drivers/scsi/pm8001/pm8001_sas.h b/drivers/scsi/pm8001/pm8001_sas.h
> index 9acaadf02150..9ff8d1fa84b0 100644
> --- a/drivers/scsi/pm8001/pm8001_sas.h
> +++ b/drivers/scsi/pm8001/pm8001_sas.h
> @@ -737,9 +737,13 @@ pm8001_ccb_alloc(struct pm8001_hba_info *pm8001_ha,
> struct pm8001_device *dev, struct sas_task *task)
> {
> struct pm8001_ccb_info *ccb;
> + struct request *rq = NULL;

I do not think you need the NULL initialization...

> u32 tag;
>
> - if (pm8001_tag_alloc(pm8001_ha, &tag)) {
> + rq = sas_task_find_rq(task);
> + if (rq) {
> + tag = rq->tag;
> + } else if (pm8001_tag_alloc(pm8001_ha, &tag)) {
> pm8001_dbg(pm8001_ha, FAIL, "Failed to allocate a tag\n");
> return NULL;
> }

--
Damien Le Moal
Western Digital Research