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SubjectRe: [PATCH v2 4/6] scsi: pm8001: Use sas_task_find_rq() for tagging
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On 9/30/22 10:56, 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 | 12 ++++--------
> drivers/scsi/pm8001/pm8001_sas.c | 16 ++++++++++++----
> drivers/scsi/pm8001/pm8001_sas.h | 11 ++++++++---
> drivers/scsi/pm8001/pm80xx_hwi.c | 17 +++--------------
> 4 files changed, 27 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/scsi/pm8001/pm8001_init.c b/drivers/scsi/pm8001/pm8001_init.c
> index 0edc9857a8bd..abb884ddcaf9 100644
> --- a/drivers/scsi/pm8001/pm8001_init.c
> +++ b/drivers/scsi/pm8001/pm8001_init.c
> @@ -196,7 +196,7 @@ static void pm8001_free(struct pm8001_hba_info *pm8001_ha)
> }
> PM8001_CHIP_DISP->chip_iounmap(pm8001_ha);
> flush_workqueue(pm8001_wq);
> - bitmap_free(pm8001_ha->tags);
> + bitmap_free(pm8001_ha->rsvd_tags);
> kfree(pm8001_ha);
> }
>
> @@ -1208,18 +1208,15 @@ 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);
> - if (!pm8001_ha->tags)
> + pm8001_ha->rsvd_tags = bitmap_zalloc(PM8001_RESERVE_SLOT, GFP_KERNEL);
> + if (!pm8001_ha->rsvd_tags)
> goto err_out;
>
> /* Memory region for ccb_info*/
> @@ -1244,7 +1241,6 @@ 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;
> }
>
> return 0;
> diff --git a/drivers/scsi/pm8001/pm8001_sas.c b/drivers/scsi/pm8001/pm8001_sas.c
> index 066dfa9f4683..d60bc311a4e9 100644
> --- a/drivers/scsi/pm8001/pm8001_sas.c
> +++ b/drivers/scsi/pm8001/pm8001_sas.c
> @@ -65,9 +65,14 @@ static int pm8001_find_tag(struct sas_task *task, u32 *tag)
> */
> void pm8001_tag_free(struct pm8001_hba_info *pm8001_ha, u32 tag)
> {
> - void *bitmap = pm8001_ha->tags;
> + void *bitmap = pm8001_ha->rsvd_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);
> @@ -80,18 +85,21 @@ void pm8001_tag_free(struct pm8001_hba_info *pm8001_ha, u32 tag)
> */
> int pm8001_tag_alloc(struct pm8001_hba_info *pm8001_ha, u32 *tag_out)
> {
> - void *bitmap = pm8001_ha->tags;
> + void *bitmap = pm8001_ha->rsvd_tags;
> unsigned long flags;
> unsigned int tag;
>
> spin_lock_irqsave(&pm8001_ha->bitmap_lock, flags);
> - tag = find_first_zero_bit(bitmap, pm8001_ha->tags_num);
> - if (tag >= pm8001_ha->tags_num) {
> + tag = find_first_zero_bit(bitmap, PM8001_RESERVE_SLOT);
> + if (tag >= PM8001_RESERVE_SLOT) {
> spin_unlock_irqrestore(&pm8001_ha->bitmap_lock, flags);
> return -SAS_QUEUE_FULL;
> }
> __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;
> }
Can you move the reserved tags to the _lower_ region of the tagset?
That way the tag allocation scheme matches with what the block-layer
does, and the eventual conversion to reserved tags becomes easier.

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

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