libata: add extra internal command

Bump the internal tag to 32, instead of stealing the last tag in
our regular command space. This works just fine, since we don't
actually need a separate hardware tag for this. Internal commands
cannot coexist with NCQ commands.

As a bonus, we get rid of the special casing of what tag to use
for the internal command.

This is in preparation for utilizing all 32 commands for normal IO.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Tejun Heo <tj@kernel.org>

drivers/ata/libata-core.c

@@ -1570,7 +1570,7 @@ unsigned ata_exec_internal_sg(struct ata_device *dev,
 	u8 command = tf->command;
 	int auto_timeout = 0;
 	struct ata_queued_cmd *qc;
-	unsigned int tag, preempted_tag;
+	unsigned int preempted_tag;
 	u32 preempted_sactive;
 	u64 preempted_qc_active;
 	int preempted_nr_active_links;
@@ -1588,20 +1588,10 @@ unsigned ata_exec_internal_sg(struct ata_device *dev,
 	}
 
 	/* initialize internal qc */
+	qc = __ata_qc_from_tag(ap, ATA_TAG_INTERNAL);
 
-	/* XXX: Tag 0 is used for drivers with legacy EH as some
-	 * drivers choke if any other tag is given.  This breaks
-	 * ata_tag_internal() test for those drivers.  Don't use new
-	 * EH stuff without converting to it.
-	 */
-	if (ap->ops->error_handler)
-		tag = ATA_TAG_INTERNAL;
-	else
-		tag = 0;
-
-	qc = __ata_qc_from_tag(ap, tag);
-
-	qc->tag = qc->hw_tag = tag;
+	qc->tag = ATA_TAG_INTERNAL;
+	qc->hw_tag = 0;
 	qc->scsicmd = NULL;
 	qc->ap = ap;
 	qc->dev = dev;
@@ -5156,7 +5146,7 @@ void ata_qc_free(struct ata_queued_cmd *qc)
 
 	qc->flags = 0;
 	tag = qc->tag;
-	if (likely(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);
@@ -5415,7 +5405,7 @@ void ata_qc_issue(struct ata_queued_cmd *qc)
 		WARN_ON_ONCE(link->sactive);
 
 		ap->nr_active_links++;
-		link->active_tag = qc->hw_tag;
+		link->active_tag = qc->tag;
 	}
 
 	qc->flags |= ATA_QCFLAG_ACTIVE;

drivers/ata/libata-eh.c

@@ -1057,7 +1057,8 @@ static int ata_do_link_abort(struct ata_port *ap, struct ata_link *link)
 	/* we're gonna abort all commands, no need for fast drain */
 	ata_eh_set_pending(ap, 0);
 
-	for (tag = 0; tag < ATA_MAX_QUEUE; tag++) {
+	/* include internal tag in iteration */
+	for (tag = 0; tag <= ATA_MAX_QUEUE; tag++) {
 		struct ata_queued_cmd *qc = ata_qc_from_tag(ap, tag);
 
 		if (qc && (!link || qc->dev->link == link)) {

include/linux/libata.h

@@ -125,9 +125,8 @@ enum {
 	LIBATA_MAX_PRD		= ATA_MAX_PRD / 2,
 	LIBATA_DUMB_MAX_PRD	= ATA_MAX_PRD / 4,	/* Worst case */
 	ATA_DEF_QUEUE		= 1,
-	/* tag ATA_MAX_QUEUE - 1 is reserved for internal commands */
 	ATA_MAX_QUEUE		= 32,
-	ATA_TAG_INTERNAL	= ATA_MAX_QUEUE - 1,
+	ATA_TAG_INTERNAL	= ATA_MAX_QUEUE,
 	ATA_SHORT_PAUSE		= 16,
 
 	ATAPI_MAX_DRAIN		= 16 << 10,
@@ -850,7 +849,7 @@ struct ata_port {
 	unsigned int		udma_mask;
 	unsigned int		cbl;	/* cable type; ATA_CBL_xxx */
 
-	struct ata_queued_cmd	qcmd[ATA_MAX_QUEUE];
+	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 */
@@ -1486,14 +1485,14 @@ extern void ata_port_pbar_desc(struct ata_port *ap, int bar, ssize_t offset,
 			       const char *name);
 #endif
 
-static inline unsigned int ata_tag_valid(unsigned int tag)
+static inline bool ata_tag_internal(unsigned int tag)
 {
-	return (tag < ATA_MAX_QUEUE) ? 1 : 0;
+	return tag == ATA_TAG_INTERNAL;
 }
 
-static inline bool ata_tag_internal(unsigned int tag)
+static inline bool ata_tag_valid(unsigned int tag)
 {
-	return tag == ATA_TAG_INTERNAL;
+	return tag < ATA_MAX_QUEUE || ata_tag_internal(tag);
 }
 
 /*
@@ -1656,7 +1655,7 @@ static inline void ata_qc_set_polling(struct ata_queued_cmd *qc)
 static inline struct ata_queued_cmd *__ata_qc_from_tag(struct ata_port *ap,
 						       unsigned int tag)
 {
-	if (likely(ata_tag_valid(tag)))
+	if (ata_tag_valid(tag))
 		return &ap->qcmd[tag];
 	return NULL;
 }