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

From: John Garry
Date: Thu Oct 27 2022 - 06:45:21 EST


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@xxxxxxxxxx>
---
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;
};