diff mbox series

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

Message ID 20250106083531.799976-5-hch@lst.de (mailing list archive)
State New
Headers show
Series [1/4] block: better split mq vs non-mq code in add_disk_fwnode | expand

Commit Message

Christoph Hellwig Jan. 6, 2025, 8:35 a.m. UTC
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(-)

Comments

John Garry Jan. 6, 2025, 8:50 a.m. UTC | #1
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.
Christoph Hellwig Jan. 6, 2025, 8:55 a.m. UTC | #2
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.
John Garry Jan. 6, 2025, 10:40 a.m. UTC | #3
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.
diff mbox series

Patch

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.