more BLK_MQ_F_* simplification v2

more BLK_MQ_F_* simplification v2

[Christoph Hellwig]

Hi Jens,

this series removes another BLK_MQ_F_ that just duplicates an implicit
condition and cleans up the tag allocation policy selection by using
an actual BLK_MQ_F_ flag instead of a two-value enum awkwardly encoded
into it.  If we'd ever grow another policy we'd be much better off just
adding a separate field to the tagset for it.

Changes since v1:
 - use a boolean bitfield for the SCSI RR tag allocation policy selection

Diffstat:
 block/blk-mq-debugfs.c                 |   26 +++-----------------
 block/blk-mq-tag.c                     |   41 ++++++++++-----------------------
 block/blk-mq.c                         |    3 --
 block/blk-mq.h                         |    5 ----
 block/bsg-lib.c                        |    2 -
 block/elevator.c                       |   20 ----------------
 block/genhd.c                          |   28 ++++++++++++----------
 drivers/ata/ahci.h                     |    2 -
 drivers/ata/pata_macio.c               |    2 -
 drivers/ata/sata_mv.c                  |    2 -
 drivers/ata/sata_nv.c                  |    4 +--
 drivers/ata/sata_sil24.c               |    1 
 drivers/block/null_blk/main.c          |    4 +--
 drivers/nvme/host/apple.c              |    1 
 drivers/nvme/host/core.c               |    1 
 drivers/scsi/hisi_sas/hisi_sas_v3_hw.c |    2 -
 drivers/scsi/scsi_lib.c                |    4 +--
 drivers/ufs/core/ufshcd.c              |    1 
 include/linux/blk-mq.h                 |   24 +++++--------------
 include/linux/libata.h                 |    4 +--
 include/scsi/scsi_host.h               |    6 +++-
 21 files changed, 58 insertions(+), 125 deletions(-)

[PATCH 1/4] block: better split mq vs non-mq code in add_disk_fwnode

[Christoph Hellwig]

Add a big conditional for blk-mq vs not mq at the beginning of
add_disk_fwnode so that elevator_init_mq is only called for blk-mq disks,
and add checks that the right methods or set or not set based on the
queue type.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/genhd.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 5da3c9a64e64..befb7a516bcf 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -400,21 +400,23 @@ int __must_check add_disk_fwnode(struct device *parent, struct gendisk *disk,
 	struct device *ddev = disk_to_dev(disk);
 	int ret;
 
-	/* Only makes sense for bio-based to set ->poll_bio */
-	if (queue_is_mq(disk->queue) && disk->fops->poll_bio)
-		return -EINVAL;
-
-	/*
-	 * The disk queue should now be all set with enough information about
-	 * the device for the elevator code to pick an adequate default
-	 * elevator if one is needed, that is, for devices requesting queue
-	 * registration.
-	 */
-	elevator_init_mq(disk->queue);
+	if (queue_is_mq(disk->queue)) {
+		/*
+		 * ->submit_bio and ->poll_bio are bypassed for blk-mq drivers.
+		 */
+		if (disk->fops->submit_bio || disk->fops->poll_bio)
+			return -EINVAL;
 
-	/* Mark bdev as having a submit_bio, if needed */
-	if (disk->fops->submit_bio)
+		/*
+		 * Initialize the I/O scheduler code and pick a default one if
+		 * needed.
+		 */
+		elevator_init_mq(disk->queue);
+	} else {
+		if (!disk->fops->submit_bio)
+			return -EINVAL;
 		bdev_set_flag(disk->part0, BD_HAS_SUBMIT_BIO);
+	}
 
 	/*
 	 * If the driver provides an explicit major number it also must provide
-- 
2.45.2

[PATCH 2/4] block: remove blk_mq_init_bitmaps

[Christoph Hellwig]

The little work done in blk_mq_init_bitmaps is easier done in the only
caller.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.g.garry@oracle.com>
---
 block/blk-mq-tag.c | 38 ++++++++++++--------------------------
 block/blk-mq.h     |  3 ---
 2 files changed, 12 insertions(+), 29 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 2cafcf11ee8b..ab4a66791a20 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -544,30 +544,12 @@ static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
 				       node);
 }
 
-int blk_mq_init_bitmaps(struct sbitmap_queue *bitmap_tags,
-			struct sbitmap_queue *breserved_tags,
-			unsigned int queue_depth, unsigned int reserved,
-			int node, int alloc_policy)
-{
-	unsigned int depth = queue_depth - reserved;
-	bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
-
-	if (bt_alloc(bitmap_tags, depth, round_robin, node))
-		return -ENOMEM;
-	if (bt_alloc(breserved_tags, reserved, round_robin, node))
-		goto free_bitmap_tags;
-
-	return 0;
-
-free_bitmap_tags:
-	sbitmap_queue_free(bitmap_tags);
-	return -ENOMEM;
-}
-
 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 				     unsigned int reserved_tags,
 				     int node, int alloc_policy)
 {
+	unsigned int depth = total_tags - reserved_tags;
+	bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
 	struct blk_mq_tags *tags;
 
 	if (total_tags > BLK_MQ_TAG_MAX) {
@@ -582,14 +564,18 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 	tags->nr_tags = total_tags;
 	tags->nr_reserved_tags = reserved_tags;
 	spin_lock_init(&tags->lock);
+	if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
+		goto out_free_tags;
+	if (bt_alloc(&tags->breserved_tags, reserved_tags, round_robin, node))
+		goto out_free_bitmap_tags;
 
-	if (blk_mq_init_bitmaps(&tags->bitmap_tags, &tags->breserved_tags,
-				total_tags, reserved_tags, node,
-				alloc_policy) < 0) {
-		kfree(tags);
-		return NULL;
-	}
 	return tags;
+
+out_free_bitmap_tags:
+	sbitmap_queue_free(&tags->bitmap_tags);
+out_free_tags:
+	kfree(tags);
+	return NULL;
 }
 
 void blk_mq_free_tags(struct blk_mq_tags *tags)
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 89a20fffa4b1..3bb9ea80f9b6 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -165,9 +165,6 @@ struct blk_mq_alloc_data {
 struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags,
 		unsigned int reserved_tags, int node, int alloc_policy);
 void blk_mq_free_tags(struct blk_mq_tags *tags);
-int blk_mq_init_bitmaps(struct sbitmap_queue *bitmap_tags,
-		struct sbitmap_queue *breserved_tags, unsigned int queue_depth,
-		unsigned int reserved, int node, int alloc_policy);
 
 unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data);
 unsigned long blk_mq_get_tags(struct blk_mq_alloc_data *data, int nr_tags,
-- 
2.45.2

[PATCH 3/4] block: remove BLK_MQ_F_NO_SCHED

[Christoph Hellwig]

The only queues that really can't support a scheduler are those that
do not have a gendisk associated with them, and thus can't be used for
non-passthrough commands.  In addition to those null_blk can optionally
set the flag, which is a bad odd.  Replace the null_blk usage with
BLK_MQ_F_NO_SCHED_BY_DEFAULT to keep the expected semantics and then
remove BLK_MQ_F_NO_SCHED as the non-disk queues never call into
elevator_init_mq or blk_register_queue which adds the sysfs attributes.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-mq-debugfs.c        |  1 -
 block/bsg-lib.c               |  2 +-
 block/elevator.c              | 20 --------------------
 drivers/block/null_blk/main.c |  4 ++--
 drivers/nvme/host/apple.c     |  1 -
 drivers/nvme/host/core.c      |  1 -
 drivers/ufs/core/ufshcd.c     |  1 -
 include/linux/blk-mq.h        |  2 --
 8 files changed, 3 insertions(+), 29 deletions(-)

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 4b6b20ccdb53..64b3c333aa47 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -185,7 +185,6 @@ static const char *const hctx_flag_name[] = {
 	HCTX_FLAG_NAME(STACKING),
 	HCTX_FLAG_NAME(TAG_HCTX_SHARED),
 	HCTX_FLAG_NAME(BLOCKING),
-	HCTX_FLAG_NAME(NO_SCHED),
 	HCTX_FLAG_NAME(NO_SCHED_BY_DEFAULT),
 };
 #undef HCTX_FLAG_NAME
diff --git a/block/bsg-lib.c b/block/bsg-lib.c
index 32da4a4429ce..93523d8f8195 100644
--- a/block/bsg-lib.c
+++ b/block/bsg-lib.c
@@ -381,7 +381,7 @@ struct request_queue *bsg_setup_queue(struct device *dev, const char *name,
 	set->queue_depth = 128;
 	set->numa_node = NUMA_NO_NODE;
 	set->cmd_size = sizeof(struct bsg_job) + dd_job_size;
-	set->flags = BLK_MQ_F_NO_SCHED | BLK_MQ_F_BLOCKING;
+	set->flags = BLK_MQ_F_BLOCKING;
 	if (blk_mq_alloc_tag_set(set))
 		goto out_tag_set;
 
diff --git a/block/elevator.c b/block/elevator.c
index be6e994256ac..b81216c48b6b 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -547,14 +547,6 @@ void elv_unregister(struct elevator_type *e)
 }
 EXPORT_SYMBOL_GPL(elv_unregister);
 
-static inline bool elv_support_iosched(struct request_queue *q)
-{
-	if (!queue_is_mq(q) ||
-	    (q->tag_set->flags & BLK_MQ_F_NO_SCHED))
-		return false;
-	return true;
-}
-
 /*
  * For single queue devices, default to using mq-deadline. If we have multiple
  * queues or mq-deadline is not available, default to "none".
@@ -580,9 +572,6 @@ void elevator_init_mq(struct request_queue *q)
 	struct elevator_type *e;
 	int err;
 
-	if (!elv_support_iosched(q))
-		return;
-
 	WARN_ON_ONCE(blk_queue_registered(q));
 
 	if (unlikely(q->elevator))
@@ -714,9 +703,6 @@ void elv_iosched_load_module(struct gendisk *disk, const char *buf,
 	struct elevator_type *found;
 	const char *name;
 
-	if (!elv_support_iosched(disk->queue))
-		return;
-
 	strscpy(elevator_name, buf, sizeof(elevator_name));
 	name = strstrip(elevator_name);
 
@@ -734,9 +720,6 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,
 	char elevator_name[ELV_NAME_MAX];
 	int ret;
 
-	if (!elv_support_iosched(disk->queue))
-		return count;
-
 	strscpy(elevator_name, buf, sizeof(elevator_name));
 	ret = elevator_change(disk->queue, strstrip(elevator_name));
 	if (!ret)
@@ -751,9 +734,6 @@ ssize_t elv_iosched_show(struct gendisk *disk, char *name)
 	struct elevator_type *cur = NULL, *e;
 	int len = 0;
 
-	if (!elv_support_iosched(q))
-		return sprintf(name, "none\n");
-
 	if (!q->elevator) {
 		len += sprintf(name+len, "[none] ");
 	} else {
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 178e62cd9a9f..d94ef37480bd 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -1792,7 +1792,7 @@ static int null_init_global_tag_set(void)
 	tag_set.queue_depth = g_hw_queue_depth;
 	tag_set.numa_node = g_home_node;
 	if (g_no_sched)
-		tag_set.flags |= BLK_MQ_F_NO_SCHED;
+		tag_set.flags |= BLK_MQ_F_NO_SCHED_BY_DEFAULT;
 	if (g_shared_tag_bitmap)
 		tag_set.flags |= BLK_MQ_F_TAG_HCTX_SHARED;
 	if (g_blocking)
@@ -1817,7 +1817,7 @@ static int null_setup_tagset(struct nullb *nullb)
 	nullb->tag_set->queue_depth = nullb->dev->hw_queue_depth;
 	nullb->tag_set->numa_node = nullb->dev->home_node;
 	if (nullb->dev->no_sched)
-		nullb->tag_set->flags |= BLK_MQ_F_NO_SCHED;
+		nullb->tag_set->flags |= BLK_MQ_F_NO_SCHED_BY_DEFAULT;
 	if (nullb->dev->shared_tag_bitmap)
 		nullb->tag_set->flags |= BLK_MQ_F_TAG_HCTX_SHARED;
 	if (nullb->dev->blocking)
diff --git a/drivers/nvme/host/apple.c b/drivers/nvme/host/apple.c
index 83c60468542c..1de11b722f04 100644
--- a/drivers/nvme/host/apple.c
+++ b/drivers/nvme/host/apple.c
@@ -1251,7 +1251,6 @@ static int apple_nvme_alloc_tagsets(struct apple_nvme *anv)
 	anv->admin_tagset.timeout = NVME_ADMIN_TIMEOUT;
 	anv->admin_tagset.numa_node = NUMA_NO_NODE;
 	anv->admin_tagset.cmd_size = sizeof(struct apple_nvme_iod);
-	anv->admin_tagset.flags = BLK_MQ_F_NO_SCHED;
 	anv->admin_tagset.driver_data = &anv->adminq;
 
 	ret = blk_mq_alloc_tag_set(&anv->admin_tagset);
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 42283d268500..c2250ddef5a2 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4564,7 +4564,6 @@ int nvme_alloc_admin_tag_set(struct nvme_ctrl *ctrl, struct blk_mq_tag_set *set,
 		/* Reserved for fabric connect and keep alive */
 		set->reserved_tags = 2;
 	set->numa_node = ctrl->numa_node;
-	set->flags = BLK_MQ_F_NO_SCHED;
 	if (ctrl->ops->flags & NVME_F_BLOCKING)
 		set->flags |= BLK_MQ_F_BLOCKING;
 	set->cmd_size = cmd_size;
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 8a01e4393159..fd53c9f402c3 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -10412,7 +10412,6 @@ static int ufshcd_add_scsi_host(struct ufs_hba *hba)
 		.nr_hw_queues	= 1,
 		.queue_depth	= hba->nutmrs,
 		.ops		= &ufshcd_tmf_ops,
-		.flags		= BLK_MQ_F_NO_SCHED,
 	};
 	err = blk_mq_alloc_tag_set(&hba->tmf_tag_set);
 	if (err < 0)
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 6340293511c9..f2ff0ffa0535 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -676,8 +676,6 @@ enum {
 	BLK_MQ_F_STACKING	= 1 << 2,
 	BLK_MQ_F_TAG_HCTX_SHARED = 1 << 3,
 	BLK_MQ_F_BLOCKING	= 1 << 4,
-	/* Do not allow an I/O scheduler to be configured. */
-	BLK_MQ_F_NO_SCHED	= 1 << 5,
 
 	/*
 	 * Select 'none' during queue registration in case of a single hwq
-- 
2.45.2

[PATCH 4/4] block: simplify tag allocation policy selection

[Christoph Hellwig]

Use a plain BLK_MQ_F_* flag to select the round robin tag selection
instead of overlaying an enum with just two possible values into the
flags space.

Doing so allows adding a BLK_MQ_F_MAX sentinel for simplified overflow
checking in the messy debugfs helpers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-mq-debugfs.c                 | 25 ++++---------------------
 block/blk-mq-tag.c                     |  5 ++---
 block/blk-mq.c                         |  3 +--
 block/blk-mq.h                         |  2 +-
 drivers/ata/ahci.h                     |  2 +-
 drivers/ata/pata_macio.c               |  2 +-
 drivers/ata/sata_mv.c                  |  2 +-
 drivers/ata/sata_nv.c                  |  4 ++--
 drivers/ata/sata_sil24.c               |  1 -
 drivers/scsi/hisi_sas/hisi_sas_v3_hw.c |  2 +-
 drivers/scsi/scsi_lib.c                |  4 ++--
 include/linux/blk-mq.h                 | 22 +++++++---------------
 include/linux/libata.h                 |  4 ++--
 include/scsi/scsi_host.h               |  6 ++++--
 14 files changed, 29 insertions(+), 55 deletions(-)

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 64b3c333aa47..adf5f0697b6b 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -172,19 +172,13 @@ static int hctx_state_show(void *data, struct seq_file *m)
 	return 0;
 }
 
-#define BLK_TAG_ALLOC_NAME(name) [BLK_TAG_ALLOC_##name] = #name
-static const char *const alloc_policy_name[] = {
-	BLK_TAG_ALLOC_NAME(FIFO),
-	BLK_TAG_ALLOC_NAME(RR),
-};
-#undef BLK_TAG_ALLOC_NAME
-
 #define HCTX_FLAG_NAME(name) [ilog2(BLK_MQ_F_##name)] = #name
 static const char *const hctx_flag_name[] = {
 	HCTX_FLAG_NAME(TAG_QUEUE_SHARED),
 	HCTX_FLAG_NAME(STACKING),
 	HCTX_FLAG_NAME(TAG_HCTX_SHARED),
 	HCTX_FLAG_NAME(BLOCKING),
+	HCTX_FLAG_NAME(TAG_RR),
 	HCTX_FLAG_NAME(NO_SCHED_BY_DEFAULT),
 };
 #undef HCTX_FLAG_NAME
@@ -192,22 +186,11 @@ static const char *const hctx_flag_name[] = {
 static int hctx_flags_show(void *data, struct seq_file *m)
 {
 	struct blk_mq_hw_ctx *hctx = data;
-	const int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(hctx->flags);
 
-	BUILD_BUG_ON(ARRAY_SIZE(hctx_flag_name) !=
-			BLK_MQ_F_ALLOC_POLICY_START_BIT);
-	BUILD_BUG_ON(ARRAY_SIZE(alloc_policy_name) != BLK_TAG_ALLOC_MAX);
+	BUILD_BUG_ON(ARRAY_SIZE(hctx_flag_name) != ilog2(BLK_MQ_F_MAX));
 
-	seq_puts(m, "alloc_policy=");
-	if (alloc_policy < ARRAY_SIZE(alloc_policy_name) &&
-	    alloc_policy_name[alloc_policy])
-		seq_puts(m, alloc_policy_name[alloc_policy]);
-	else
-		seq_printf(m, "%d", alloc_policy);
-	seq_puts(m, " ");
-	blk_flags_show(m,
-		       hctx->flags ^ BLK_ALLOC_POLICY_TO_MQ_FLAG(alloc_policy),
-		       hctx_flag_name, ARRAY_SIZE(hctx_flag_name));
+	blk_flags_show(m, hctx->flags, hctx_flag_name,
+			ARRAY_SIZE(hctx_flag_name));
 	seq_puts(m, "\n");
 	return 0;
 }
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index ab4a66791a20..b9f417d980b4 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -545,11 +545,10 @@ static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
 }
 
 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
-				     unsigned int reserved_tags,
-				     int node, int alloc_policy)
+		unsigned int reserved_tags, unsigned int flags, int node)
 {
 	unsigned int depth = total_tags - reserved_tags;
-	bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
+	bool round_robin = flags & BLK_MQ_F_TAG_RR;
 	struct blk_mq_tags *tags;
 
 	if (total_tags > BLK_MQ_TAG_MAX) {
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 17f10683d640..2e6132f778fd 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3476,8 +3476,7 @@ static struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
 	if (node == NUMA_NO_NODE)
 		node = set->numa_node;
 
-	tags = blk_mq_init_tags(nr_tags, reserved_tags, node,
-				BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
+	tags = blk_mq_init_tags(nr_tags, reserved_tags, set->flags, node);
 	if (!tags)
 		return NULL;
 
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 3bb9ea80f9b6..c872bbbe6411 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -163,7 +163,7 @@ struct blk_mq_alloc_data {
 };
 
 struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags,
-		unsigned int reserved_tags, int node, int alloc_policy);
+		unsigned int reserved_tags, unsigned int flags, int node);
 void blk_mq_free_tags(struct blk_mq_tags *tags);
 
 unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data);
diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index 8f40f75ba08c..06781bdde0d2 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -396,7 +396,7 @@ extern const struct attribute_group *ahci_sdev_groups[];
 	.shost_groups		= ahci_shost_groups,			\
 	.sdev_groups		= ahci_sdev_groups,			\
 	.change_queue_depth     = ata_scsi_change_queue_depth,		\
-	.tag_alloc_policy       = BLK_TAG_ALLOC_RR,             	\
+	.tag_alloc_policy_rr	= true,					\
 	.device_configure	= ata_scsi_device_configure
 
 extern struct ata_port_operations ahci_ops;
diff --git a/drivers/ata/pata_macio.c b/drivers/ata/pata_macio.c
index f2f36e55a1f4..4b01bb6880b0 100644
--- a/drivers/ata/pata_macio.c
+++ b/drivers/ata/pata_macio.c
@@ -935,7 +935,7 @@ static const struct scsi_host_template pata_macio_sht = {
 	.device_configure	= pata_macio_device_configure,
 	.sdev_groups		= ata_common_sdev_groups,
 	.can_queue		= ATA_DEF_QUEUE,
-	.tag_alloc_policy	= BLK_TAG_ALLOC_RR,
+	.tag_alloc_policy_rr	= true,
 };
 
 static struct ata_port_operations pata_macio_ops = {
diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index b8f363370e1a..21c72650f9cc 100644
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -672,7 +672,7 @@ static const struct scsi_host_template mv6_sht = {
 	.dma_boundary		= MV_DMA_BOUNDARY,
 	.sdev_groups		= ata_ncq_sdev_groups,
 	.change_queue_depth	= ata_scsi_change_queue_depth,
-	.tag_alloc_policy	= BLK_TAG_ALLOC_RR,
+	.tag_alloc_policy_rr	= true,
 	.device_configure	= ata_scsi_device_configure
 };
 
diff --git a/drivers/ata/sata_nv.c b/drivers/ata/sata_nv.c
index 36d99043ef50..823cce5ea1e9 100644
--- a/drivers/ata/sata_nv.c
+++ b/drivers/ata/sata_nv.c
@@ -385,7 +385,7 @@ static const struct scsi_host_template nv_adma_sht = {
 	.device_configure	= nv_adma_device_configure,
 	.sdev_groups		= ata_ncq_sdev_groups,
 	.change_queue_depth     = ata_scsi_change_queue_depth,
-	.tag_alloc_policy	= BLK_TAG_ALLOC_RR,
+	.tag_alloc_policy_rr	= true,
 };
 
 static const struct scsi_host_template nv_swncq_sht = {
@@ -396,7 +396,7 @@ static const struct scsi_host_template nv_swncq_sht = {
 	.device_configure	= nv_swncq_device_configure,
 	.sdev_groups		= ata_ncq_sdev_groups,
 	.change_queue_depth     = ata_scsi_change_queue_depth,
-	.tag_alloc_policy	= BLK_TAG_ALLOC_RR,
+	.tag_alloc_policy_rr	= true,
 };
 
 /*
diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
index 72c03cbdaff4..935b13e79dec 100644
--- a/drivers/ata/sata_sil24.c
+++ b/drivers/ata/sata_sil24.c
@@ -378,7 +378,6 @@ static const struct scsi_host_template sil24_sht = {
 	.can_queue		= SIL24_MAX_CMDS,
 	.sg_tablesize		= SIL24_MAX_SGE,
 	.dma_boundary		= ATA_DMA_BOUNDARY,
-	.tag_alloc_policy	= BLK_TAG_ALLOC_FIFO,
 	.sdev_groups		= ata_ncq_sdev_groups,
 	.change_queue_depth	= ata_scsi_change_queue_depth,
 	.device_configure	= ata_scsi_device_configure
diff --git a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
index 79129c977704..35501d0aa655 100644
--- a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
@@ -3345,7 +3345,7 @@ static const struct scsi_host_template sht_v3_hw = {
 	.slave_alloc		= hisi_sas_slave_alloc,
 	.shost_groups		= host_v3_hw_groups,
 	.sdev_groups		= sdev_groups_v3_hw,
-	.tag_alloc_policy	= BLK_TAG_ALLOC_RR,
+	.tag_alloc_policy_rr	= true,
 	.host_reset             = hisi_sas_host_reset,
 	.host_tagset		= 1,
 	.mq_poll		= queue_complete_v3_hw,
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 5cf124e13097..51c496ca9380 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2065,8 +2065,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
 	tag_set->queue_depth = shost->can_queue;
 	tag_set->cmd_size = cmd_size;
 	tag_set->numa_node = dev_to_node(shost->dma_dev);
-	tag_set->flags |=
-		BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
+	if (shost->hostt->tag_alloc_policy_rr)
+		tag_set->flags |= BLK_MQ_F_TAG_RR;
 	if (shost->queuecommand_may_block)
 		tag_set->flags |= BLK_MQ_F_BLOCKING;
 	tag_set->driver_data = shost;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index f2ff0ffa0535..a0a9007cc1e3 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -296,13 +296,6 @@ enum blk_eh_timer_return {
 	BLK_EH_RESET_TIMER,
 };
 
-/* Keep alloc_policy_name[] in sync with the definitions below */
-enum {
-	BLK_TAG_ALLOC_FIFO,	/* allocate starting from 0 */
-	BLK_TAG_ALLOC_RR,	/* allocate starting from last allocated tag */
-	BLK_TAG_ALLOC_MAX
-};
-
 /**
  * struct blk_mq_hw_ctx - State for a hardware queue facing the hardware
  * block device
@@ -677,20 +670,19 @@ enum {
 	BLK_MQ_F_TAG_HCTX_SHARED = 1 << 3,
 	BLK_MQ_F_BLOCKING	= 1 << 4,
 
+	/*
+	 * Alloc tags on a round-robin base instead of the first available one.
+	 */
+	BLK_MQ_F_TAG_RR		= 1 << 5,
+
 	/*
 	 * Select 'none' during queue registration in case of a single hwq
 	 * or shared hwqs instead of 'mq-deadline'.
 	 */
 	BLK_MQ_F_NO_SCHED_BY_DEFAULT	= 1 << 6,
-	BLK_MQ_F_ALLOC_POLICY_START_BIT = 7,
-	BLK_MQ_F_ALLOC_POLICY_BITS = 1,
+
+	BLK_MQ_F_MAX = 1 << 7,
 };
-#define BLK_MQ_FLAG_TO_ALLOC_POLICY(flags) \
-	((flags >> BLK_MQ_F_ALLOC_POLICY_START_BIT) & \
-		((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1))
-#define BLK_ALLOC_POLICY_TO_MQ_FLAG(policy) \
-	((policy & ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1)) \
-		<< BLK_MQ_F_ALLOC_POLICY_START_BIT)
 
 #define BLK_MQ_MAX_DEPTH	(10240)
 #define BLK_MQ_NO_HCTX_IDX	(-1U)
diff --git a/include/linux/libata.h b/include/linux/libata.h
index c1a85d46eba6..be5183d75736 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -1467,13 +1467,13 @@ extern const struct attribute_group *ata_common_sdev_groups[];
 #define ATA_SUBBASE_SHT(drv_name)				\
 	__ATA_BASE_SHT(drv_name),				\
 	.can_queue		= ATA_DEF_QUEUE,		\
-	.tag_alloc_policy	= BLK_TAG_ALLOC_RR,		\
+	.tag_alloc_policy_rr	= true,				\
 	.device_configure	= ata_scsi_device_configure
 
 #define ATA_SUBBASE_SHT_QD(drv_name, drv_qd)			\
 	__ATA_BASE_SHT(drv_name),				\
 	.can_queue		= drv_qd,			\
-	.tag_alloc_policy	= BLK_TAG_ALLOC_RR,		\
+	.tag_alloc_policy_rr	= true,				\
 	.device_configure	= ata_scsi_device_configure
 
 #define ATA_BASE_SHT(drv_name)					\
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 2b4ab0369ffb..02823d6af37d 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -438,8 +438,10 @@ struct scsi_host_template {
 	 */
 	short cmd_per_lun;
 
-	/* If use block layer to manage tags, this is tag allocation policy */
-	int tag_alloc_policy;
+	/*
+	 * Allocate tags starting from last allocated tag.
+	 */
+	bool tag_alloc_policy_rr : 1;
 
 	/*
 	 * Track QUEUE_FULL events and reduce queue depth on demand.
-- 
2.45.2

Re: [PATCH 4/4] block: simplify tag allocation policy selection

[John Garry]

On 06/01/2025 08:35, Christoph Hellwig wrote:
> Use a plain BLK_MQ_F_* flag to select the round robin tag selection
> instead of overlaying an enum with just two possible values into the
> flags space.
> 
> Doing so allows adding a BLK_MQ_F_MAX sentinel for simplified overflow
> checking in the messy debugfs helpers.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---

Looks fine, but some small comments still. However, feel free to add:

Reviewed-by: John Garry <john.g.garry@oracle.com>

>   /*
> diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
> index 72c03cbdaff4..935b13e79dec 100644
> --- a/drivers/ata/sata_sil24.c
> +++ b/drivers/ata/sata_sil24.c
> @@ -378,7 +378,6 @@ static const struct scsi_host_template sil24_sht = {
>   	.can_queue		= SIL24_MAX_CMDS,
>   	.sg_tablesize		= SIL24_MAX_SGE,
>   	.dma_boundary		= ATA_DMA_BOUNDARY,
> -	.tag_alloc_policy	= BLK_TAG_ALLOC_FIFO,

nit: maybe that could be a separate patch, but no biggie

>   	.sdev_groups		= ata_ncq_sdev_groups,
>   	.change_queue_depth	= ata_scsi_change_queue_depth,
>   	.device_configure	= ata_scsi_device_configure
> diff --git a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
> index 79129c977704..35501d0aa655 100644

> --- a/include/scsi/scsi_host.h
> +++ b/include/scsi/scsi_host.h
> @@ -438,8 +438,10 @@ struct scsi_host_template {
>   	 */
>   	short cmd_per_lun;
>   
> -	/* If use block layer to manage tags, this is tag allocation policy */
> -	int tag_alloc_policy;
> +	/*
> +	 * Allocate tags starting from last allocated tag.
> +	 */
> +	bool tag_alloc_policy_rr : 1;

Is it proper to use bool here? I am not sure. Others use unsigned int or 
unsigned.

nit: coding style elsewhere in scsi_host_template would be to use 
"tag_alloc_policy_rr:1;"

>   
>   	/*
>   	 * Track QUEUE_FULL events and reduce queue depth on demand.

Re: [PATCH 4/4] block: simplify tag allocation policy selection

[Christoph Hellwig]

On Mon, Jan 06, 2025 at 08:50:20AM +0000, John Garry wrote:
>>   	.can_queue		= SIL24_MAX_CMDS,
>>   	.sg_tablesize		= SIL24_MAX_SGE,
>>   	.dma_boundary		= ATA_DMA_BOUNDARY,
>> -	.tag_alloc_policy	= BLK_TAG_ALLOC_FIFO,
>
> nit: maybe that could be a separate patch, but no biggie

I though about that, but if felt a bit overkill.

>> +	/*
>> +	 * Allocate tags starting from last allocated tag.
>> +	 */
>> +	bool tag_alloc_policy_rr : 1;
>
> Is it proper to use bool here? I am not sure. Others use unsigned int or 
> unsigned.

Yes, you can use any unsigned type for a single-bit bitfield.  Most of
the existing uses just predate the availability of bool or were copy
and pasted after that.

>
> nit: coding style elsewhere in scsi_host_template would be to use 
> "tag_alloc_policy_rr:1;"

Yes, but that's against the normal kernel coding style, so we'd better
stop adding more of that.

Re: [PATCH 4/4] block: simplify tag allocation policy selection

[John Garry]

On 06/01/2025 08:55, Christoph Hellwig wrote:
>>> bool tag_alloc_policy_rr : 1;
>> Is it proper to use bool here? I am not sure. Others use unsigned int or
>> unsigned.
> Yes, you can use any unsigned type for a single-bit bitfield.  Most of
> the existing uses just predate the availability of bool or were copy
> and pasted after that.
> 
>> nit: coding style elsewhere in scsi_host_template would be to use
>> "tag_alloc_policy_rr:1;"
> Yes, but that's against the normal kernel coding style, so we'd better
> stop adding more of that.

I suppose then that the rest should be updated afterwards to be 
consistent (with the kernel coding style). That should be easier than - 
for example - removing extern usage.

Re: more BLK_MQ_F_* simplification v2

[Jens Axboe]

On Mon, 06 Jan 2025 09:35:07 +0100, Christoph Hellwig wrote:
> this series removes another BLK_MQ_F_ that just duplicates an implicit
> condition and cleans up the tag allocation policy selection by using
> an actual BLK_MQ_F_ flag instead of a two-value enum awkwardly encoded
> into it.  If we'd ever grow another policy we'd be much better off just
> adding a separate field to the tagset for it.
> 
> Changes since v1:
>  - use a boolean bitfield for the SCSI RR tag allocation policy selection
> 
> [...]

Applied, thanks!

[1/4] block: better split mq vs non-mq code in add_disk_fwnode
      commit: 6783811569aef24b949992bd5c4e6eaac02a0c30
[2/4] block: remove blk_mq_init_bitmaps
      commit: 68ed45122249083bf45593ed635474282583352c
[3/4] block: remove BLK_MQ_F_NO_SCHED
      commit: e7602bb4f3a1234df8b75728ac3260bcb8242612
[4/4] block: simplify tag allocation policy selection
      commit: ce32496ec1abe866225f2e2005ceda68cf4c7bf4

Best regards,
-- 
Jens Axboe