Re: [PATCH RFC v3 1/7] ata: libata-scsi: Add ata_scsi_queue_internal()

John Garry
2022-10-27T10:45:18Z

On 27/10/2022 02:42, Damien Le Moal wrote:
> On 10/25/22 19:32, John Garry wrote:
>> Add a function to handle queued ATA internal SCSI cmnds - does much the
>> same as ata_exec_internal_sg() does (which will be fixed up later to
>> actually queue internal cmnds through this function).
>>
>> Signed-off-by: John Garry <john.garry@huawei.com>
>> ---
>> drivers/ata/libata-sata.c | 3 +++
>> drivers/ata/libata-scsi.c | 43 +++++++++++++++++++++++++++++++++++++++
>> drivers/ata/libata.h | 3 ++-
>> include/linux/libata.h | 6 ++++++
>> 4 files changed, 54 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
>> index b6806d41a8c5..e8b828c56542 100644
>> --- a/drivers/ata/libata-sata.c
>> +++ b/drivers/ata/libata-sata.c
>> @@ -1258,6 +1258,9 @@ int ata_sas_queuecmd(struct scsi_cmnd *cmd, struct ata_port *ap)
>> {
>> int rc = 0;
>>
>> + if (blk_mq_is_reserved_rq(scsi_cmd_to_rq(cmd)))
>> + return ata_scsi_queue_internal(cmd, ap->link.device);
>> +
>> if (likely(ata_dev_enabled(ap->link.device)))
>> rc = __ata_scsi_queuecmd(cmd, ap->link.device);
>> else {
>> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
>> index 476e0ef4bd29..30d7c90b0c35 100644
>> --- a/drivers/ata/libata-scsi.c
>> +++ b/drivers/ata/libata-scsi.c
>> @@ -3965,6 +3965,49 @@ static inline ata_xlat_func_t ata_get_xlat_func(struct ata_device *dev, u8 cmd)
>> return NULL;
>> }
>>
>> +unsigned int ata_scsi_queue_internal(struct scsi_cmnd *scmd,
>> + struct ata_device *dev)
>> +{
>> + struct ata_link *link = dev->link;
>> + struct ata_port *ap = link->ap;
>> + struct ata_queued_cmd *qc;
>> +
>> + /* no internal command while frozen */
>> + if (ap->pflags & ATA_PFLAG_FROZEN)
>> + goto did_err;
>> +
>> + /* initialize internal qc */
>> + qc = __ata_qc_from_tag(ap, ATA_TAG_INTERNAL);
>> + link->preempted_tag = link->active_tag;
>> + link->preempted_sactive = link->sactive;
>> + ap->preempted_qc_active = ap->qc_active;
>> + ap->preempted_nr_active_links = ap->nr_active_links;
>> + link->active_tag = ATA_TAG_POISON;
>> + link->sactive = 0;
>> + ap->qc_active = 0;
>> + ap->nr_active_links = 0;
>> +
>> + if (qc->dma_dir != DMA_NONE) {
>> + int n_elem;
>> +
>> + n_elem = 1;
>> + qc->n_elem = n_elem;
>> + qc->sg = scsi_sglist(scmd);
>> + qc->nbytes = qc->sg->length;
>> + ata_sg_init(qc, qc->sg, n_elem);
>> + }
>> +
>> + scmd->submitter = SUBMITTED_BY_BLOCK_LAYER;
>> +
>> + ata_qc_issue(qc);
>
> Arg, no ! This potentially mixes NCQ and non-NCQ commands, which is
> forbidden by ATA spec. You need to use something like:
>
> if (ap->ops->qc_defer) {
> if ((rc = ap->ops->qc_defer(qc)))
> goto defer;
> }
>
> ata_qc_issue(qc);
>
> which is done in __ata_scsi_queuecmd() -> ata_scsi_translate()
>
> Unless you guarantee that ata_scsi_queue_internal() is always called
> from libata EH context ?

This will be called synchronously called from ata_exec_internal_sg(), so
the same rules on NCQ vs non-NCQ would apply here. As I see,
ata_exec_internal_sg() assumes non-NCQ mode and is not multi-thread safe.

Thanks,
John

>
>> +
>> + return 0;
>> +did_err:
>> + scmd->result = (DID_ERROR << 16);
>> + scsi_done(scmd);
>> + return 0;
>> +}
>> +
>> int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev)
>> {
>> u8 scsi_op = scmd->cmnd[0];
>> diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
>> index 0c2df1e60768..15cd1cd618b8 100644
>> --- a/drivers/ata/libata.h
>> +++ b/drivers/ata/libata.h
>> @@ -82,7 +82,6 @@ extern int ata_port_probe(struct ata_port *ap);
>> extern void __ata_port_probe(struct ata_port *ap);
>> extern unsigned int ata_read_log_page(struct ata_device *dev, u8 log,
>> u8 page, void *buf, unsigned int sectors);
>> -
>> #define to_ata_port(d) container_of(d, struct ata_port, tdev)
>>
>> /* libata-acpi.c */
>> @@ -130,6 +129,8 @@ extern int ata_scsi_user_scan(struct Scsi_Host *shost, unsigned int channel,
>> void ata_scsi_sdev_config(struct scsi_device *sdev);
>> int ata_scsi_dev_config(struct scsi_device *sdev, struct ata_device *dev);
>> int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev);
>> +unsigned int ata_scsi_queue_internal(struct scsi_cmnd *scmd,
>> + struct ata_device *dev);
>>
>> /* libata-eh.c */
>> extern unsigned int ata_internal_cmd_timeout(struct ata_device *dev, u8 cmd);
>> diff --git a/include/linux/libata.h b/include/linux/libata.h
>> index 827d5838cd23..8938b584520f 100644
>> --- a/include/linux/libata.h
>> +++ b/include/linux/libata.h
>> @@ -764,7 +764,9 @@ struct ata_link {
>>
>> struct device tdev;
>> unsigned int active_tag; /* active tag on this link */
>> + unsigned int preempted_tag;
>> u32 sactive; /* active NCQ commands */
>> + u32 preempted_sactive;
>>
>> unsigned int flags; /* ATA_LFLAG_xxx */
>>
>> @@ -857,6 +859,10 @@ struct ata_port {
>> #ifdef CONFIG_ATA_ACPI
>> struct ata_acpi_gtm __acpi_init_gtm; /* use ata_acpi_init_gtm() */
>> #endif
>> +
>> + u64 preempted_qc_active;
>> + int preempted_nr_active_links;
>> +
>> /* owned by EH */
>> u8 sector_buf[ATA_SECT_SIZE] ____cacheline_aligned;
>> };
>