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Date: Wed, 6 Apr 2022 10:39:04 +0900
From: Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To: John Garry <john.garry@...wei.com>, hch@....de
Cc: linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
linux-doc@...r.kernel.org, linux-scsi@...r.kernel.org
Subject: Re: [PATCH v2 1/2] libata: Use scsi cmnd budget token for qc tag for
SAS host
On 4/4/22 23:53, John Garry wrote:
> For attaining a qc tag for a SAS host we need to allocate a bit in
> ata_port.sas_tag_allocated bitmap.
>
> However we already have a unique tag per device in range
> [0, ATA_MAX_QUEUE) in the scsi cmnd budget token, so just use that
> instead.
The valid range is [0, ATA_MAX_QUEUE - 1]. Tag ATA_MAX_QUEUE is
ATA_TAG_INTERNAL which is never allocated as a valid device tag but used
directly in ata_exec_internal().
>
> Signed-off-by: John Garry <john.garry@...wei.com>
> ---
> drivers/ata/libata-core.c | 14 +++++---------
> drivers/ata/libata-sata.c | 25 ++++---------------------
> drivers/ata/libata-scsi.c | 2 +-
> drivers/ata/libata.h | 7 +++----
> include/linux/libata.h | 1 -
> 5 files changed, 13 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index cceedde51126..1067b2e2be28 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -4566,14 +4566,15 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words)
> /**
> * ata_qc_new_init - Request an available ATA command, and initialize it
> * @dev: Device from whom we request an available command structure
> - * @tag: tag
> + * @scmd: scmd for which to get qc
> *
> * LOCKING:
> * None.
> */
>
> -struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, int tag)
> +struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, struct scsi_cmnd *scmd)
> {
> + int tag = scsi_cmd_to_rq(scmd)->tag;
> struct ata_port *ap = dev->link->ap;
> struct ata_queued_cmd *qc;
>
> @@ -4583,7 +4584,7 @@ struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, int tag)
>
> /* libsas case */
> if (ap->flags & ATA_FLAG_SAS_HOST) {
> - tag = ata_sas_allocate_tag(ap);
> + tag = ata_sas_get_tag(scmd);
> if (tag < 0)
> return NULL;
> }
> @@ -4611,19 +4612,14 @@ struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, int tag)
> */
> void ata_qc_free(struct ata_queued_cmd *qc)
> {
> - struct ata_port *ap;
> unsigned int tag;
>
> WARN_ON_ONCE(qc == NULL); /* ata_qc_from_tag _might_ return NULL */
> - ap = qc->ap;
>
> qc->flags = 0;
> tag = qc->tag;
> - if (ata_tag_valid(tag)) {
> + if (ata_tag_valid(tag))
> qc->tag = ATA_TAG_POISON;
> - if (ap->flags & ATA_FLAG_SAS_HOST)
> - ata_sas_free_tag(tag, ap);
> - }
> }
>
> void __ata_qc_complete(struct ata_queued_cmd *qc)
> diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
> index 044a16daa2d4..c3e9fd7d920c 100644
> --- a/drivers/ata/libata-sata.c
> +++ b/drivers/ata/libata-sata.c
> @@ -1268,29 +1268,12 @@ int ata_sas_queuecmd(struct scsi_cmnd *cmd, struct ata_port *ap)
> }
> EXPORT_SYMBOL_GPL(ata_sas_queuecmd);
>
> -int ata_sas_allocate_tag(struct ata_port *ap)
> +int ata_sas_get_tag(struct scsi_cmnd *scmd)
> {
> - unsigned int max_queue = ap->host->n_tags;
> - unsigned int i, tag;
> + if (WARN_ON_ONCE(scmd->budget_token >= ATA_MAX_QUEUE))
> + return -1;
>
> - for (i = 0, tag = ap->sas_last_tag + 1; i < max_queue; i++, tag++) {
> - tag = tag < max_queue ? tag : 0;
> -
> - /* the last tag is reserved for internal command. */
> - if (ata_tag_internal(tag))
> - continue;
> -
> - if (!test_and_set_bit(tag, &ap->sas_tag_allocated)) {
> - ap->sas_last_tag = tag;
> - return tag;
> - }
> - }
> - return -1;
> -}
> -
> -void ata_sas_free_tag(unsigned int tag, struct ata_port *ap)
> -{
> - clear_bit(tag, &ap->sas_tag_allocated);
> + return scmd->budget_token;
> }
>
> /**
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index 06c9d90238d9..61dd7f7c7743 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -640,7 +640,7 @@ static struct ata_queued_cmd *ata_scsi_qc_new(struct ata_device *dev,
> {
> struct ata_queued_cmd *qc;
>
> - qc = ata_qc_new_init(dev, scsi_cmd_to_rq(cmd)->tag);
> + qc = ata_qc_new_init(dev, cmd);
> if (qc) {
> qc->scsicmd = cmd;
> qc->scsidone = scsi_done;
> diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
> index c9c2496d91ea..92e52090165b 100644
> --- a/drivers/ata/libata.h
> +++ b/drivers/ata/libata.h
> @@ -44,7 +44,7 @@ static inline void ata_force_cbl(struct ata_port *ap) { }
> #endif
> extern u64 ata_tf_to_lba(const struct ata_taskfile *tf);
> extern u64 ata_tf_to_lba48(const struct ata_taskfile *tf);
> -extern struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, int tag);
> +extern struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, struct scsi_cmnd *scmd);
> extern int ata_build_rw_tf(struct ata_taskfile *tf, struct ata_device *dev,
> u64 block, u32 n_block, unsigned int tf_flags,
> unsigned int tag, int class);
> @@ -93,10 +93,9 @@ extern unsigned int ata_read_log_page(struct ata_device *dev, u8 log,
>
> /* libata-sata.c */
> #ifdef CONFIG_SATA_HOST
> -int ata_sas_allocate_tag(struct ata_port *ap);
> -void ata_sas_free_tag(unsigned int tag, struct ata_port *ap);
> +int ata_sas_get_tag(struct scsi_cmnd *scmd);
> #else
> -static inline int ata_sas_allocate_tag(struct ata_port *ap)
> +static inline int ata_sas_get_tag(struct scsi_cmnd *scmd)
> {
> return -EOPNOTSUPP;
> }
> diff --git a/include/linux/libata.h b/include/linux/libata.h
> index 9b1d3d8b1252..16107122e587 100644
> --- a/include/linux/libata.h
> +++ b/include/linux/libata.h
> @@ -820,7 +820,6 @@ struct ata_port {
> unsigned int cbl; /* cable type; ATA_CBL_xxx */
>
> struct ata_queued_cmd qcmd[ATA_MAX_QUEUE + 1];
> - unsigned long sas_tag_allocated; /* for sas tag allocation only */
> u64 qc_active;
> int nr_active_links; /* #links with active qcs */
> unsigned int sas_last_tag; /* track next tag hw expects */
--
Damien Le Moal
Western Digital Research
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