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

Christoph Hellwig
2025-01-06T08:35:44Z

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