[PATCH RESEND v3 00/13] blk-mq: Reduce static requests memory footprint for shared sbitmap

[PATCH RESEND v3 00/13] blk-mq: Reduce static requests memory footprint for shared sbitmap

[John Garry]

Currently a full set of static requests are allocated per hw queue per
tagset when shared sbitmap is used.

However, only tagset->queue_depth number of requests may be active at
any given time. As such, only tagset->queue_depth number of static
requests are required.

The same goes for using an IO scheduler, which allocates a full set of
static requests per hw queue per request queue.

This series changes shared sbitmap support by using a shared tags per
tagset and request queue. Ming suggested something along those lines in
v1 review. But we'll keep name "shared sbitmap" name as it is familiar. In
using a shared tags, the static rqs also become shared, reducing the
number of sets of static rqs, reducing memory usage.

Patch "blk-mq: Use shared tags for shared sbitmap support" is a bit big,
and could potentially be broken down. But then maintaining ability to
bisect becomes harder and each sub-patch would get more convoluted.

For megaraid sas driver on my 128-CPU arm64 system with 1x SATA disk, we
save approx. 300MB(!) [370MB -> 60MB]

Baseline is v5.15-rc1

This resend is just a rebase, which applied cleanly.

Changes since v2:
- Make blk_mq_clear_rq_mapping() static again
- Various function renaming for conciseness and consistency
- Add/refactor alloc/free map and rqs function
- Drop the new blk_mq_ops init_request method in favour of passing an
  invalid HW queue index for shared sbitmap
- Add patch to not clear rq mapping for driver tags
- Remove blk_mq_init_bitmap_tags()
- Add some more RB tags (thanks!)

Changes since v1:
- Switch to use blk_mq_tags for shared sbitmap
- Add new blk_mq_ops init request callback
- Add some RB tags (thanks!)

John Garry (13):
  blk-mq: Change rqs check in blk_mq_free_rqs()
  block: Rename BLKDEV_MAX_RQ -> BLKDEV_DEFAULT_RQ
  blk-mq: Relocate shared sbitmap resize in blk_mq_update_nr_requests()
  blk-mq: Invert check in blk_mq_update_nr_requests()
  blk-mq-sched: Rename blk_mq_sched_alloc_{tags -> map_and_rqs}()
  blk-mq-sched: Rename blk_mq_sched_free_{requests -> rqs}()
  blk-mq: Pass driver tags to blk_mq_clear_rq_mapping()
  blk-mq: Don't clear driver tags own mapping
  blk-mq: Add blk_mq_tag_update_sched_shared_sbitmap()
  blk-mq: Add blk_mq_alloc_map_and_rqs()
  blk-mq: Refactor and rename blk_mq_free_map_and_{requests->rqs}()
  blk-mq: Use shared tags for shared sbitmap support
  blk-mq: Stop using pointers for blk_mq_tags bitmap tags

 block/bfq-iosched.c    |   4 +-
 block/blk-core.c       |   4 +-
 block/blk-mq-debugfs.c |   8 +-
 block/blk-mq-sched.c   | 116 +++++++++++------------
 block/blk-mq-sched.h   |   4 +-
 block/blk-mq-tag.c     | 125 +++++++++---------------
 block/blk-mq-tag.h     |  14 +--
 block/blk-mq.c         | 209 ++++++++++++++++++++++++-----------------
 block/blk-mq.h         |  18 ++--
 block/blk.h            |   2 +-
 block/kyber-iosched.c  |   4 +-
 block/mq-deadline.c    |   2 +-
 drivers/block/rbd.c    |   2 +-
 include/linux/blk-mq.h |  15 ++-
 include/linux/blkdev.h |   5 +-
 15 files changed, 256 insertions(+), 276 deletions(-)

-- 
2.26.2

[PATCH RESEND v3 01/13] blk-mq: Change rqs check in blk_mq_free_rqs()

[John Garry]

The original code in commit 24d2f90309b23 ("blk-mq: split out tag
initialization, support shared tags") would check tags->rqs is non-NULL and
then dereference tags->rqs[].

Then in commit 2af8cbe30531 ("blk-mq: split tag ->rqs[] into two"), we
started to dereference tags->static_rqs[], but continued to check non-NULL
tags->rqs.

Check tags->static_rqs as non-NULL instead, which is more logical.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 108a352051be..2316ff27c1f5 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2340,7 +2340,7 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 {
 	struct page *page;
 
-	if (tags->rqs && set->ops->exit_request) {
+	if (tags->static_rqs && set->ops->exit_request) {
 		int i;
 
 		for (i = 0; i < tags->nr_tags; i++) {
-- 
2.26.2

Re: [PATCH RESEND v3 01/13] blk-mq: Change rqs check in blk_mq_free_rqs()

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> The original code in commit 24d2f90309b23 ("blk-mq: split out tag
> initialization, support shared tags") would check tags->rqs is non-NULL and
> then dereference tags->rqs[].
> 
> Then in commit 2af8cbe30531 ("blk-mq: split tag ->rqs[] into two"), we
> started to dereference tags->static_rqs[], but continued to check non-NULL
> tags->rqs.
> 
> Check tags->static_rqs as non-NULL instead, which is more logical.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> ---
>   block/blk-mq.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 108a352051be..2316ff27c1f5 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2340,7 +2340,7 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
>   {
>   	struct page *page;
>   
> -	if (tags->rqs && set->ops->exit_request) {
> +	if (tags->static_rqs && set->ops->exit_request) {
>   		int i;
>   
>   		for (i = 0; i < tags->nr_tags; i++) {
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

[PATCH RESEND v3 02/13] block: Rename BLKDEV_MAX_RQ -> BLKDEV_DEFAULT_RQ

[John Garry]

It is a bit confusing that there is BLKDEV_MAX_RQ and MAX_SCHED_RQ, as
the name BLKDEV_MAX_RQ would imply the max requests always, which it is
not.

Rename to BLKDEV_MAX_RQ to BLKDEV_DEFAULT_RQ, matching it's usage - that being
the default number of requests assigned when allocating a request queue.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-core.c       | 2 +-
 block/blk-mq-sched.c   | 2 +-
 block/blk-mq-sched.h   | 2 +-
 drivers/block/rbd.c    | 2 +-
 include/linux/blkdev.h | 2 +-
 5 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 5454db2fa263..5d7137bec48e 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -568,7 +568,7 @@ struct request_queue *blk_alloc_queue(int node_id)
 
 	blk_queue_dma_alignment(q, 511);
 	blk_set_default_limits(&q->limits);
-	q->nr_requests = BLKDEV_MAX_RQ;
+	q->nr_requests = BLKDEV_DEFAULT_RQ;
 
 	return q;
 
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 0f006cabfd91..2231fb0d4c35 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -606,7 +606,7 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
 	 * Additionally, this is a per-hw queue depth.
 	 */
 	q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth,
-				   BLKDEV_MAX_RQ);
+				   BLKDEV_DEFAULT_RQ);
 
 	queue_for_each_hw_ctx(q, hctx, i) {
 		ret = blk_mq_sched_alloc_tags(q, hctx, i);
diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 5246ae040704..1e46be6c5178 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -5,7 +5,7 @@
 #include "blk-mq.h"
 #include "blk-mq-tag.h"
 
-#define MAX_SCHED_RQ (16 * BLKDEV_MAX_RQ)
+#define MAX_SCHED_RQ (16 * BLKDEV_DEFAULT_RQ)
 
 void blk_mq_sched_assign_ioc(struct request *rq);
 
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index e65c9d706f6f..bf60aebd0cfb 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -836,7 +836,7 @@ struct rbd_options {
 	u32 alloc_hint_flags;  /* CEPH_OSD_OP_ALLOC_HINT_FLAG_* */
 };
 
-#define RBD_QUEUE_DEPTH_DEFAULT	BLKDEV_MAX_RQ
+#define RBD_QUEUE_DEPTH_DEFAULT	BLKDEV_DEFAULT_RQ
 #define RBD_ALLOC_SIZE_DEFAULT	(64 * 1024)
 #define RBD_LOCK_TIMEOUT_DEFAULT 0  /* no timeout */
 #define RBD_READ_ONLY_DEFAULT	false
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 12b9dbcc980e..4baf9435232d 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -40,7 +40,7 @@ struct blk_stat_callback;
 struct blk_keyslot_manager;
 
 #define BLKDEV_MIN_RQ	4
-#define BLKDEV_MAX_RQ	128	/* Default maximum */
+#define BLKDEV_DEFAULT_RQ	128
 
 /* Must be consistent with blk_mq_poll_stats_bkt() */
 #define BLK_MQ_POLL_STATS_BKTS 16
-- 
2.26.2

Re: [PATCH RESEND v3 02/13] block: Rename BLKDEV_MAX_RQ -> BLKDEV_DEFAULT_RQ

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> It is a bit confusing that there is BLKDEV_MAX_RQ and MAX_SCHED_RQ, as
> the name BLKDEV_MAX_RQ would imply the max requests always, which it is
> not.
> 
> Rename to BLKDEV_MAX_RQ to BLKDEV_DEFAULT_RQ, matching it's usage - that being
> the default number of requests assigned when allocating a request queue.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> ---
>   block/blk-core.c       | 2 +-
>   block/blk-mq-sched.c   | 2 +-
>   block/blk-mq-sched.h   | 2 +-
>   drivers/block/rbd.c    | 2 +-
>   include/linux/blkdev.h | 2 +-
>   5 files changed, 5 insertions(+), 5 deletions(-)
>  
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

[PATCH RESEND v3 03/13] blk-mq: Relocate shared sbitmap resize in blk_mq_update_nr_requests()

[John Garry]

For shared sbitmap, if the call to blk_mq_tag_update_depth() was
successful for any hctx when hctx->sched_tags is not set, then it would be
successful for all (due to nature in which blk_mq_tag_update_depth()
fails).

As such, there is no need to call blk_mq_tag_resize_shared_sbitmap() for
each hctx. So relocate the call until after the hctx iteration under the
!q->elevator check, which is equivalent (to !hctx->sched_tags).

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2316ff27c1f5..1a4bb2db30e5 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3616,8 +3616,6 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 		if (!hctx->sched_tags) {
 			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
 							false);
-			if (!ret && blk_mq_is_sbitmap_shared(set->flags))
-				blk_mq_tag_resize_shared_sbitmap(set, nr);
 		} else {
 			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
 							nr, true);
@@ -3635,9 +3633,13 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 	}
 	if (!ret) {
 		q->nr_requests = nr;
-		if (q->elevator && blk_mq_is_sbitmap_shared(set->flags))
-			sbitmap_queue_resize(&q->sched_bitmap_tags,
-					     nr - set->reserved_tags);
+		if (blk_mq_is_sbitmap_shared(set->flags)) {
+			if (q->elevator)
+				sbitmap_queue_resize(&q->sched_bitmap_tags,
+						     nr - set->reserved_tags);
+			else
+				blk_mq_tag_resize_shared_sbitmap(set, nr);
+		}
 	}
 
 	blk_mq_unquiesce_queue(q);
-- 
2.26.2

Re: [PATCH RESEND v3 03/13] blk-mq: Relocate shared sbitmap resize in blk_mq_update_nr_requests()

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> For shared sbitmap, if the call to blk_mq_tag_update_depth() was
> successful for any hctx when hctx->sched_tags is not set, then it would be
> successful for all (due to nature in which blk_mq_tag_update_depth()
> fails).
> 
> As such, there is no need to call blk_mq_tag_resize_shared_sbitmap() for
> each hctx. So relocate the call until after the hctx iteration under the
> !q->elevator check, which is equivalent (to !hctx->sched_tags).
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> ---
>   block/blk-mq.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

[PATCH RESEND v3 04/13] blk-mq: Invert check in blk_mq_update_nr_requests()

[John Garry]

It's easier to read:

if (x)
	X;
else
	Y;

over:

if (!x)
	Y;
else
	X;

No functional change intended.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1a4bb2db30e5..47d6ab725bcc 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3613,18 +3613,18 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 		 * If we're using an MQ scheduler, just update the scheduler
 		 * queue depth. This is similar to what the old code would do.
 		 */
-		if (!hctx->sched_tags) {
-			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
-							false);
-		} else {
+		if (hctx->sched_tags) {
 			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
-							nr, true);
+						      nr, true);
 			if (blk_mq_is_sbitmap_shared(set->flags)) {
 				hctx->sched_tags->bitmap_tags =
 					&q->sched_bitmap_tags;
 				hctx->sched_tags->breserved_tags =
 					&q->sched_breserved_tags;
 			}
+		} else {
+			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
+						      false);
 		}
 		if (ret)
 			break;
-- 
2.26.2

Re: [PATCH RESEND v3 04/13] blk-mq: Invert check in blk_mq_update_nr_requests()

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> It's easier to read:
> 
> if (x)
> 	X;
> else
> 	Y;
> 
> over:
> 
> if (!x)
> 	Y;
> else
> 	X;
> 
> No functional change intended.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> ---
>   block/blk-mq.c | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
> 
Reviewed-by: Hannes Reinecke

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

[PATCH RESEND v3 05/13] blk-mq-sched: Rename blk_mq_sched_alloc_{tags -> map_and_rqs}()

[John Garry]

Function blk_mq_sched_alloc_tags() does same as
__blk_mq_alloc_map_and_request(), so give a similar name to be consistent.

Similarly rename label err_free_tags -> err_free_map_and_rqs.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq-sched.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 2231fb0d4c35..5f340203e6e5 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -515,9 +515,9 @@ void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx,
 	percpu_ref_put(&q->q_usage_counter);
 }
 
-static int blk_mq_sched_alloc_tags(struct request_queue *q,
-				   struct blk_mq_hw_ctx *hctx,
-				   unsigned int hctx_idx)
+static int blk_mq_sched_alloc_map_and_rqs(struct request_queue *q,
+					  struct blk_mq_hw_ctx *hctx,
+					  unsigned int hctx_idx)
 {
 	struct blk_mq_tag_set *set = q->tag_set;
 	int ret;
@@ -609,15 +609,15 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
 				   BLKDEV_DEFAULT_RQ);
 
 	queue_for_each_hw_ctx(q, hctx, i) {
-		ret = blk_mq_sched_alloc_tags(q, hctx, i);
+		ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i);
 		if (ret)
-			goto err_free_tags;
+			goto err_free_map_and_rqs;
 	}
 
 	if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
 		ret = blk_mq_init_sched_shared_sbitmap(q);
 		if (ret)
-			goto err_free_tags;
+			goto err_free_map_and_rqs;
 	}
 
 	ret = e->ops.init_sched(q, e);
@@ -645,8 +645,8 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
 err_free_sbitmap:
 	if (blk_mq_is_sbitmap_shared(q->tag_set->flags))
 		blk_mq_exit_sched_shared_sbitmap(q);
-err_free_tags:
 	blk_mq_sched_free_requests(q);
+err_free_map_and_rqs:
 	blk_mq_sched_tags_teardown(q);
 	q->elevator = NULL;
 	return ret;
-- 
2.26.2

Re: [PATCH RESEND v3 05/13] blk-mq-sched: Rename blk_mq_sched_alloc_{tags -> map_and_rqs}()

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> Function blk_mq_sched_alloc_tags() does same as
> __blk_mq_alloc_map_and_request(), so give a similar name to be consistent.
> 
> Similarly rename label err_free_tags -> err_free_map_and_rqs.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> ---
>   block/blk-mq-sched.c | 14 +++++++-------
>   1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> index 2231fb0d4c35..5f340203e6e5 100644
> --- a/block/blk-mq-sched.c
> +++ b/block/blk-mq-sched.c
> @@ -515,9 +515,9 @@ void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx,
>   	percpu_ref_put(&q->q_usage_counter);
>   }
>   
> -static int blk_mq_sched_alloc_tags(struct request_queue *q,
> -				   struct blk_mq_hw_ctx *hctx,
> -				   unsigned int hctx_idx)
> +static int blk_mq_sched_alloc_map_and_rqs(struct request_queue *q,
> +					  struct blk_mq_hw_ctx *hctx,
> +					  unsigned int hctx_idx)
>   {
>   	struct blk_mq_tag_set *set = q->tag_set;
>   	int ret;
> @@ -609,15 +609,15 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
>   				   BLKDEV_DEFAULT_RQ);
>   
>   	queue_for_each_hw_ctx(q, hctx, i) {
> -		ret = blk_mq_sched_alloc_tags(q, hctx, i);
> +		ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i);
>   		if (ret)
> -			goto err_free_tags;
> +			goto err_free_map_and_rqs;
>   	}
>   
>   	if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
>   		ret = blk_mq_init_sched_shared_sbitmap(q);
>   		if (ret)
> -			goto err_free_tags;
> +			goto err_free_map_and_rqs;
>   	}
>   
>   	ret = e->ops.init_sched(q, e);
> @@ -645,8 +645,8 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
>   err_free_sbitmap:
>   	if (blk_mq_is_sbitmap_shared(q->tag_set->flags))
>   		blk_mq_exit_sched_shared_sbitmap(q);
> -err_free_tags:
>   	blk_mq_sched_free_requests(q);
> +err_free_map_and_rqs:
>   	blk_mq_sched_tags_teardown(q);
>   	q->elevator = NULL;
>   	return ret;
> 
This is not only a rename, but it also moves the location of the label.
Is that intended?
If so it needs some documentation why this is safe.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH RESEND v3 05/13] blk-mq-sched: Rename blk_mq_sched_alloc_{tags -> map_and_rqs}()

[John Garry]

>> +static int blk_mq_sched_alloc_map_and_rqs(struct request_queue *q,
>> +                      struct blk_mq_hw_ctx *hctx,
>> +                      unsigned int hctx_idx)
>>   {
>>       struct blk_mq_tag_set *set = q->tag_set;
>>       int ret;
>> @@ -609,15 +609,15 @@ int blk_mq_init_sched(struct request_queue *q, 
>> struct elevator_type *e)
>>                      BLKDEV_DEFAULT_RQ);
>>       queue_for_each_hw_ctx(q, hctx, i) {
>> -        ret = blk_mq_sched_alloc_tags(q, hctx, i);
>> +        ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i);
>>           if (ret)
>> -            goto err_free_tags;
>> +            goto err_free_map_and_rqs;
>>       }
>>       if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
>>           ret = blk_mq_init_sched_shared_sbitmap(q);
>>           if (ret)
>> -            goto err_free_tags;
>> +            goto err_free_map_and_rqs;
>>       }
>>       ret = e->ops.init_sched(q, e);
>> @@ -645,8 +645,8 @@ int blk_mq_init_sched(struct request_queue *q, 
>> struct elevator_type *e)
>>   err_free_sbitmap:
>>       if (blk_mq_is_sbitmap_shared(q->tag_set->flags))
>>           blk_mq_exit_sched_shared_sbitmap(q);
>> -err_free_tags:
>>       blk_mq_sched_free_requests(q);
>> +err_free_map_and_rqs:
>>       blk_mq_sched_tags_teardown(q);
>>       q->elevator = NULL;
>>       return ret;
>>
> This is not only a rename, but it also moves the location of the label.
> Is that intended?
> If so it needs some documentation why this is safe.

Yeah, I think you're right.

The final code in the series looks correct, but this is a transient 
breakage.

I'll fix it.

Thanks,
John

[PATCH RESEND v3 06/13] blk-mq-sched: Rename blk_mq_sched_free_{requests -> rqs}()

[John Garry]

To be more concise and consistent in naming, rename
blk_mq_sched_free_requests() -> blk_mq_sched_free_rqs().

Signed-off-by: John Garry <john.garry@huawei.com>
---
 block/blk-core.c     | 2 +-
 block/blk-mq-sched.c | 6 +++---
 block/blk-mq-sched.h | 2 +-
 block/blk.h          | 2 +-
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 5d7137bec48e..3480df0e958c 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -406,7 +406,7 @@ void blk_cleanup_queue(struct request_queue *q)
 	 */
 	mutex_lock(&q->sysfs_lock);
 	if (q->elevator)
-		blk_mq_sched_free_requests(q);
+		blk_mq_sched_free_rqs(q);
 	mutex_unlock(&q->sysfs_lock);
 
 	percpu_ref_exit(&q->q_usage_counter);
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 5f340203e6e5..3ab26154f0ea 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -631,7 +631,7 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
 			ret = e->ops.init_hctx(hctx, i);
 			if (ret) {
 				eq = q->elevator;
-				blk_mq_sched_free_requests(q);
+				blk_mq_sched_free_rqs(q);
 				blk_mq_exit_sched(q, eq);
 				kobject_put(&eq->kobj);
 				return ret;
@@ -645,7 +645,7 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
 err_free_sbitmap:
 	if (blk_mq_is_sbitmap_shared(q->tag_set->flags))
 		blk_mq_exit_sched_shared_sbitmap(q);
-	blk_mq_sched_free_requests(q);
+	blk_mq_sched_free_rqs(q);
 err_free_map_and_rqs:
 	blk_mq_sched_tags_teardown(q);
 	q->elevator = NULL;
@@ -656,7 +656,7 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
  * called in either blk_queue_cleanup or elevator_switch, tagset
  * is required for freeing requests
  */
-void blk_mq_sched_free_requests(struct request_queue *q)
+void blk_mq_sched_free_rqs(struct request_queue *q)
 {
 	struct blk_mq_hw_ctx *hctx;
 	int i;
diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 1e46be6c5178..e70748d18754 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -28,7 +28,7 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx);
 
 int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e);
 void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e);
-void blk_mq_sched_free_requests(struct request_queue *q);
+void blk_mq_sched_free_rqs(struct request_queue *q);
 
 static inline bool
 blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
diff --git a/block/blk.h b/block/blk.h
index 7d2a0ba7ed21..6f125c8cddb0 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -200,7 +200,7 @@ static inline void elevator_exit(struct request_queue *q,
 {
 	lockdep_assert_held(&q->sysfs_lock);
 
-	blk_mq_sched_free_requests(q);
+	blk_mq_sched_free_rqs(q);
 	__elevator_exit(q, e);
 }
 
-- 
2.26.2

Re: [PATCH RESEND v3 06/13] blk-mq-sched: Rename blk_mq_sched_free_{requests -> rqs}()

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> To be more concise and consistent in naming, rename
> blk_mq_sched_free_requests() -> blk_mq_sched_free_rqs().
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
>   block/blk-core.c     | 2 +-
>   block/blk-mq-sched.c | 6 +++---
>   block/blk-mq-sched.h | 2 +-
>   block/blk.h          | 2 +-
>   4 files changed, 6 insertions(+), 6 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

[PATCH RESEND v3 07/13] blk-mq: Pass driver tags to blk_mq_clear_rq_mapping()

[John Garry]

Function blk_mq_clear_rq_mapping() will be used for shared sbitmap tags
in future, so pass a driver tags pointer instead of the tagset container
and HW queue index.

Signed-off-by: John Garry <john.garry@huawei.com>
---
 block/blk-mq.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 47d6ab725bcc..4bae8afdfbe1 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2302,10 +2302,9 @@ static size_t order_to_size(unsigned int order)
 }
 
 /* called before freeing request pool in @tags */
-static void blk_mq_clear_rq_mapping(struct blk_mq_tag_set *set,
-		struct blk_mq_tags *tags, unsigned int hctx_idx)
+static void blk_mq_clear_rq_mapping(struct blk_mq_tags *drv_tags,
+				    struct blk_mq_tags *tags)
 {
-	struct blk_mq_tags *drv_tags = set->tags[hctx_idx];
 	struct page *page;
 	unsigned long flags;
 
@@ -2314,7 +2313,7 @@ static void blk_mq_clear_rq_mapping(struct blk_mq_tag_set *set,
 		unsigned long end = start + order_to_size(page->private);
 		int i;
 
-		for (i = 0; i < set->queue_depth; i++) {
+		for (i = 0; i < drv_tags->nr_tags; i++) {
 			struct request *rq = drv_tags->rqs[i];
 			unsigned long rq_addr = (unsigned long)rq;
 
@@ -2338,8 +2337,11 @@ static void blk_mq_clear_rq_mapping(struct blk_mq_tag_set *set,
 void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 		     unsigned int hctx_idx)
 {
+	struct blk_mq_tags *drv_tags;
 	struct page *page;
 
+	drv_tags = set->tags[hctx_idx];
+
 	if (tags->static_rqs && set->ops->exit_request) {
 		int i;
 
@@ -2353,7 +2355,7 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 		}
 	}
 
-	blk_mq_clear_rq_mapping(set, tags, hctx_idx);
+	blk_mq_clear_rq_mapping(drv_tags, tags);
 
 	while (!list_empty(&tags->page_list)) {
 		page = list_first_entry(&tags->page_list, struct page, lru);
-- 
2.26.2

Re: [PATCH RESEND v3 07/13] blk-mq: Pass driver tags to blk_mq_clear_rq_mapping()

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> Function blk_mq_clear_rq_mapping() will be used for shared sbitmap tags
> in future, so pass a driver tags pointer instead of the tagset container
> and HW queue index.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
>   block/blk-mq.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

[PATCH RESEND v3 08/13] blk-mq: Don't clear driver tags own mapping

[John Garry]

Function blk_mq_clear_rq_mapping() is required to clear the sched tags
mappings in driver tags rqs[].

But there is no need for a driver tags to clear its own mapping, so skip
clearing the mapping in this scenario.

Signed-off-by: John Garry <john.garry@huawei.com>
---
 block/blk-mq.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 4bae8afdfbe1..5229c5420b85 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2308,6 +2308,10 @@ static void blk_mq_clear_rq_mapping(struct blk_mq_tags *drv_tags,
 	struct page *page;
 	unsigned long flags;
 
+	/* There is no need to clear a driver tags own mapping */
+	if (drv_tags == tags)
+		return;
+
 	list_for_each_entry(page, &tags->page_list, lru) {
 		unsigned long start = (unsigned long)page_address(page);
 		unsigned long end = start + order_to_size(page->private);
-- 
2.26.2

Re: [PATCH RESEND v3 08/13] blk-mq: Don't clear driver tags own mapping

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> Function blk_mq_clear_rq_mapping() is required to clear the sched tags
> mappings in driver tags rqs[].
> 
> But there is no need for a driver tags to clear its own mapping, so skip
> clearing the mapping in this scenario.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
>   block/blk-mq.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 4bae8afdfbe1..5229c5420b85 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2308,6 +2308,10 @@ static void blk_mq_clear_rq_mapping(struct blk_mq_tags *drv_tags,
>   	struct page *page;
>   	unsigned long flags;
>   
> +	/* There is no need to clear a driver tags own mapping */
> +	if (drv_tags == tags)
> +		return;
> +
>   	list_for_each_entry(page, &tags->page_list, lru) {
>   		unsigned long start = (unsigned long)page_address(page);
>   		unsigned long end = start + order_to_size(page->private);
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

[PATCH RESEND v3 09/13] blk-mq: Add blk_mq_tag_update_sched_shared_sbitmap()

[John Garry]

Put the functionality to update the sched shared sbitmap size in a common
function.

Since the same formula is always used to resize, and it can be got from
the request queue argument, so just pass the request queue pointer.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq-sched.c | 3 +--
 block/blk-mq-tag.c   | 6 ++++++
 block/blk-mq-tag.h   | 1 +
 block/blk-mq.c       | 3 +--
 4 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 3ab26154f0ea..a3b5a5399bc8 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -575,8 +575,7 @@ static int blk_mq_init_sched_shared_sbitmap(struct request_queue *queue)
 					&queue->sched_breserved_tags;
 	}
 
-	sbitmap_queue_resize(&queue->sched_bitmap_tags,
-			     queue->nr_requests - set->reserved_tags);
+	blk_mq_tag_update_sched_shared_sbitmap(queue);
 
 	return 0;
 }
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 86f87346232a..5f06ad6efc8f 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -634,6 +634,12 @@ void blk_mq_tag_resize_shared_sbitmap(struct blk_mq_tag_set *set, unsigned int s
 	sbitmap_queue_resize(&set->__bitmap_tags, size - set->reserved_tags);
 }
 
+void blk_mq_tag_update_sched_shared_sbitmap(struct request_queue *q)
+{
+	sbitmap_queue_resize(&q->sched_bitmap_tags,
+			     q->nr_requests - q->tag_set->reserved_tags);
+}
+
 /**
  * blk_mq_unique_tag() - return a tag that is unique queue-wide
  * @rq: request for which to compute a unique tag
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index 8ed55af08427..88f3c6485543 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -48,6 +48,7 @@ extern int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 					unsigned int depth, bool can_grow);
 extern void blk_mq_tag_resize_shared_sbitmap(struct blk_mq_tag_set *set,
 					     unsigned int size);
+extern void blk_mq_tag_update_sched_shared_sbitmap(struct request_queue *q);
 
 extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool);
 void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5229c5420b85..5fec444d6399 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3641,8 +3641,7 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 		q->nr_requests = nr;
 		if (blk_mq_is_sbitmap_shared(set->flags)) {
 			if (q->elevator)
-				sbitmap_queue_resize(&q->sched_bitmap_tags,
-						     nr - set->reserved_tags);
+				blk_mq_tag_update_sched_shared_sbitmap(q);
 			else
 				blk_mq_tag_resize_shared_sbitmap(set, nr);
 		}
-- 
2.26.2

Re: [PATCH RESEND v3 09/13] blk-mq: Add blk_mq_tag_update_sched_shared_sbitmap()

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> Put the functionality to update the sched shared sbitmap size in a common
> function.
> 
> Since the same formula is always used to resize, and it can be got from
> the request queue argument, so just pass the request queue pointer.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> ---
>   block/blk-mq-sched.c | 3 +--
>   block/blk-mq-tag.c   | 6 ++++++
>   block/blk-mq-tag.h   | 1 +
>   block/blk-mq.c       | 3 +--
>   4 files changed, 9 insertions(+), 4 deletions(-)
> Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

[PATCH RESEND v3 10/13] blk-mq: Add blk_mq_alloc_map_and_rqs()

[John Garry]

Add a function to combine allocating tags and the associated requests,
and factor out common patterns to use this new function.

Some functions only call blk_mq_alloc_map_and_rqs() now, but more
functionality will be added later to those functions.

Also make blk_mq_alloc_rq_map() and blk_mq_alloc_rqs() static since they
are only used in blk-mq.c, and finally rename some functions for
conciseness and consistency with other function names:
- __blk_mq_alloc_map_and_{request -> rqs}()
- blk_mq_alloc_{map_and_requests -> set_map_and_rqs}()

Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: John Garry <john.garry@huawei.com>
---
 block/blk-mq-sched.c | 15 +++--------
 block/blk-mq-tag.c   |  9 +------
 block/blk-mq.c       | 62 +++++++++++++++++++++++++-------------------
 block/blk-mq.h       |  9 ++-----
 4 files changed, 42 insertions(+), 53 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index a3b5a5399bc8..17752f39e144 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -519,21 +519,12 @@ static int blk_mq_sched_alloc_map_and_rqs(struct request_queue *q,
 					  struct blk_mq_hw_ctx *hctx,
 					  unsigned int hctx_idx)
 {
-	struct blk_mq_tag_set *set = q->tag_set;
-	int ret;
+	hctx->sched_tags = blk_mq_alloc_map_and_rqs(q->tag_set, hctx_idx,
+						    q->nr_requests);
 
-	hctx->sched_tags = blk_mq_alloc_rq_map(set, hctx_idx, q->nr_requests,
-					       set->reserved_tags, set->flags);
 	if (!hctx->sched_tags)
 		return -ENOMEM;
-
-	ret = blk_mq_alloc_rqs(set, hctx->sched_tags, hctx_idx, q->nr_requests);
-	if (ret) {
-		blk_mq_free_rq_map(hctx->sched_tags, set->flags);
-		hctx->sched_tags = NULL;
-	}
-
-	return ret;
+	return 0;
 }
 
 /* called in queue's release handler, tagset has gone away */
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 5f06ad6efc8f..d0b5e52be3c8 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -592,7 +592,6 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 	if (tdepth > tags->nr_tags) {
 		struct blk_mq_tag_set *set = hctx->queue->tag_set;
 		struct blk_mq_tags *new;
-		bool ret;
 
 		if (!can_grow)
 			return -EINVAL;
@@ -604,15 +603,9 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 		if (tdepth > MAX_SCHED_RQ)
 			return -EINVAL;
 
-		new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth,
-				tags->nr_reserved_tags, set->flags);
+		new = blk_mq_alloc_map_and_rqs(set, hctx->queue_num, tdepth);
 		if (!new)
 			return -ENOMEM;
-		ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
-		if (ret) {
-			blk_mq_free_rq_map(new, set->flags);
-			return -ENOMEM;
-		}
 
 		blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
 		blk_mq_free_rq_map(*tagsptr, set->flags);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5fec444d6399..46772773b9c4 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2383,11 +2383,11 @@ void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags)
 	blk_mq_free_tags(tags, flags);
 }
 
-struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
-					unsigned int hctx_idx,
-					unsigned int nr_tags,
-					unsigned int reserved_tags,
-					unsigned int flags)
+static struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
+					       unsigned int hctx_idx,
+					       unsigned int nr_tags,
+					       unsigned int reserved_tags,
+					       unsigned int flags)
 {
 	struct blk_mq_tags *tags;
 	int node;
@@ -2435,8 +2435,9 @@ static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
 	return 0;
 }
 
-int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
-		     unsigned int hctx_idx, unsigned int depth)
+static int blk_mq_alloc_rqs(struct blk_mq_tag_set *set,
+			    struct blk_mq_tags *tags,
+			    unsigned int hctx_idx, unsigned int depth)
 {
 	unsigned int i, j, entries_per_page, max_order = 4;
 	size_t rq_size, left;
@@ -2847,25 +2848,34 @@ static void blk_mq_init_cpu_queues(struct request_queue *q,
 	}
 }
 
-static bool __blk_mq_alloc_map_and_request(struct blk_mq_tag_set *set,
-					int hctx_idx)
+struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
+					     unsigned int hctx_idx,
+					     unsigned int depth)
 {
-	unsigned int flags = set->flags;
-	int ret = 0;
+	struct blk_mq_tags *tags;
+	int ret;
 
-	set->tags[hctx_idx] = blk_mq_alloc_rq_map(set, hctx_idx,
-					set->queue_depth, set->reserved_tags, flags);
-	if (!set->tags[hctx_idx])
-		return false;
+	tags = blk_mq_alloc_rq_map(set, hctx_idx, depth, set->reserved_tags,
+				   set->flags);
+	if (!tags)
+		return NULL;
 
-	ret = blk_mq_alloc_rqs(set, set->tags[hctx_idx], hctx_idx,
-				set->queue_depth);
-	if (!ret)
-		return true;
+	ret = blk_mq_alloc_rqs(set, tags, hctx_idx, depth);
+	if (ret) {
+		blk_mq_free_rq_map(tags, set->flags);
+		return NULL;
+	}
 
-	blk_mq_free_rq_map(set->tags[hctx_idx], flags);
-	set->tags[hctx_idx] = NULL;
-	return false;
+	return tags;
+}
+
+static bool __blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
+				       int hctx_idx)
+{
+	set->tags[hctx_idx] = blk_mq_alloc_map_and_rqs(set, hctx_idx,
+						       set->queue_depth);
+
+	return set->tags[hctx_idx];
 }
 
 static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
@@ -2910,7 +2920,7 @@ static void blk_mq_map_swqueue(struct request_queue *q)
 			hctx_idx = set->map[j].mq_map[i];
 			/* unmapped hw queue can be remapped after CPU topo changed */
 			if (!set->tags[hctx_idx] &&
-			    !__blk_mq_alloc_map_and_request(set, hctx_idx)) {
+			    !__blk_mq_alloc_map_and_rqs(set, hctx_idx)) {
 				/*
 				 * If tags initialization fail for some hctx,
 				 * that hctx won't be brought online.  In this
@@ -3343,7 +3353,7 @@ static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
 	int i;
 
 	for (i = 0; i < set->nr_hw_queues; i++) {
-		if (!__blk_mq_alloc_map_and_request(set, i))
+		if (!__blk_mq_alloc_map_and_rqs(set, i))
 			goto out_unwind;
 		cond_resched();
 	}
@@ -3362,7 +3372,7 @@ static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
  * may reduce the depth asked for, if memory is tight. set->queue_depth
  * will be updated to reflect the allocated depth.
  */
-static int blk_mq_alloc_map_and_requests(struct blk_mq_tag_set *set)
+static int blk_mq_alloc_set_map_and_rqs(struct blk_mq_tag_set *set)
 {
 	unsigned int depth;
 	int err;
@@ -3528,7 +3538,7 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 	if (ret)
 		goto out_free_mq_map;
 
-	ret = blk_mq_alloc_map_and_requests(set);
+	ret = blk_mq_alloc_set_map_and_rqs(set);
 	if (ret)
 		goto out_free_mq_map;
 
diff --git a/block/blk-mq.h b/block/blk-mq.h
index d08779f77a26..83585a344568 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -55,13 +55,8 @@ void blk_mq_put_rq_ref(struct request *rq);
 void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 		     unsigned int hctx_idx);
 void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags);
-struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
-					unsigned int hctx_idx,
-					unsigned int nr_tags,
-					unsigned int reserved_tags,
-					unsigned int flags);
-int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
-		     unsigned int hctx_idx, unsigned int depth);
+struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
+				unsigned int hctx_idx, unsigned int depth);
 
 /*
  * Internal helpers for request insertion into sw queues
-- 
2.26.2

Re: [PATCH RESEND v3 10/13] blk-mq: Add blk_mq_alloc_map_and_rqs()

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> Add a function to combine allocating tags and the associated requests,
> and factor out common patterns to use this new function.
> 
> Some functions only call blk_mq_alloc_map_and_rqs() now, but more
> functionality will be added later to those functions.
> 
> Also make blk_mq_alloc_rq_map() and blk_mq_alloc_rqs() static since they
> are only used in blk-mq.c, and finally rename some functions for
> conciseness and consistency with other function names:
> - __blk_mq_alloc_map_and_{request -> rqs}()
> - blk_mq_alloc_{map_and_requests -> set_map_and_rqs}()
> 
> Suggested-by: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
>   block/blk-mq-sched.c | 15 +++--------
>   block/blk-mq-tag.c   |  9 +------
>   block/blk-mq.c       | 62 +++++++++++++++++++++++++-------------------
>   block/blk-mq.h       |  9 ++-----
>   4 files changed, 42 insertions(+), 53 deletions(-)
> Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

[PATCH RESEND v3 11/13] blk-mq: Refactor and rename blk_mq_free_map_and_{requests->rqs}()

[John Garry]

Refactor blk_mq_free_map_and_requests() such that it can be used at many
sites at which the tag map and rqs are freed.

Also rename to blk_mq_free_map_and_rqs(), which is shorter and matches the
alloc equivalent.

Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: John Garry <john.garry@huawei.com>
---
 block/blk-mq-tag.c |  3 +--
 block/blk-mq.c     | 40 ++++++++++++++++++++++++----------------
 block/blk-mq.h     |  4 +++-
 3 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index d0b5e52be3c8..fcc33581ce5e 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -607,8 +607,7 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 		if (!new)
 			return -ENOMEM;
 
-		blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
-		blk_mq_free_rq_map(*tagsptr, set->flags);
+		blk_mq_free_map_and_rqs(set, *tagsptr, hctx->queue_num);
 		*tagsptr = new;
 	} else {
 		/*
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 46772773b9c4..464ea20b9bcb 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2878,15 +2878,15 @@ static bool __blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
 	return set->tags[hctx_idx];
 }
 
-static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
-					 unsigned int hctx_idx)
+void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
+			     struct blk_mq_tags *tags,
+			     unsigned int hctx_idx)
 {
 	unsigned int flags = set->flags;
 
-	if (set->tags && set->tags[hctx_idx]) {
-		blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx);
-		blk_mq_free_rq_map(set->tags[hctx_idx], flags);
-		set->tags[hctx_idx] = NULL;
+	if (tags) {
+		blk_mq_free_rqs(set, tags, hctx_idx);
+		blk_mq_free_rq_map(tags, flags);
 	}
 }
 
@@ -2967,8 +2967,10 @@ static void blk_mq_map_swqueue(struct request_queue *q)
 			 * fallback in case of a new remap fails
 			 * allocation
 			 */
-			if (i && set->tags[i])
-				blk_mq_free_map_and_requests(set, i);
+			if (i && set->tags[i]) {
+				blk_mq_free_map_and_rqs(set, set->tags[i], i);
+				set->tags[i] = NULL;
+			}
 
 			hctx->tags = NULL;
 			continue;
@@ -3264,8 +3266,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
 		struct blk_mq_hw_ctx *hctx = hctxs[j];
 
 		if (hctx) {
-			if (hctx->tags)
-				blk_mq_free_map_and_requests(set, j);
+			blk_mq_free_map_and_rqs(set, set->tags[j], j);
+			set->tags[j] = NULL;
 			blk_mq_exit_hctx(q, set, hctx, j);
 			hctxs[j] = NULL;
 		}
@@ -3361,8 +3363,10 @@ static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
 	return 0;
 
 out_unwind:
-	while (--i >= 0)
-		blk_mq_free_map_and_requests(set, i);
+	while (--i >= 0) {
+		blk_mq_free_map_and_rqs(set, set->tags[i], i);
+		set->tags[i] = NULL;
+	}
 
 	return -ENOMEM;
 }
@@ -3557,8 +3561,10 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 	return 0;
 
 out_free_mq_rq_maps:
-	for (i = 0; i < set->nr_hw_queues; i++)
-		blk_mq_free_map_and_requests(set, i);
+	for (i = 0; i < set->nr_hw_queues; i++) {
+		blk_mq_free_map_and_rqs(set, set->tags[i], i);
+		set->tags[i] = NULL;
+	}
 out_free_mq_map:
 	for (i = 0; i < set->nr_maps; i++) {
 		kfree(set->map[i].mq_map);
@@ -3590,8 +3596,10 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
 {
 	int i, j;
 
-	for (i = 0; i < set->nr_hw_queues; i++)
-		blk_mq_free_map_and_requests(set, i);
+	for (i = 0; i < set->nr_hw_queues; i++) {
+		blk_mq_free_map_and_rqs(set, set->tags[i], i);
+		set->tags[i] = NULL;
+	}
 
 	if (blk_mq_is_sbitmap_shared(set->flags))
 		blk_mq_exit_shared_sbitmap(set);
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 83585a344568..bcb0ca89d37a 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -57,7 +57,9 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags);
 struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
 				unsigned int hctx_idx, unsigned int depth);
-
+void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
+			     struct blk_mq_tags *tags,
+			     unsigned int hctx_idx);
 /*
  * Internal helpers for request insertion into sw queues
  */
-- 
2.26.2

Re: [PATCH RESEND v3 11/13] blk-mq: Refactor and rename blk_mq_free_map_and_{requests->rqs}()

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> Refactor blk_mq_free_map_and_requests() such that it can be used at many
> sites at which the tag map and rqs are freed.
> 
> Also rename to blk_mq_free_map_and_rqs(), which is shorter and matches the
> alloc equivalent.
> 
> Suggested-by: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
>   block/blk-mq-tag.c |  3 +--
>   block/blk-mq.c     | 40 ++++++++++++++++++++++++----------------
>   block/blk-mq.h     |  4 +++-
>   3 files changed, 28 insertions(+), 19 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

[PATCH RESEND v3 12/13] blk-mq: Use shared tags for shared sbitmap support

[John Garry]

Currently we use separate sbitmap pairs and active_queues atomic_t for
shared sbitmap support.

However a full sets of static requests are used per HW queue, which is
quite wasteful, considering that the total number of requests usable at
any given time across all HW queues is limited by the shared sbitmap depth.

As such, it is considerably more memory efficient in the case of shared
sbitmap to allocate a set of static rqs per tag set or request queue, and
not per HW queue.

So replace the sbitmap pairs and active_queues atomic_t with a shared
tags per tagset and request queue, which will hold a set of shared static
rqs.

Since there is now no valid HW queue index to be passed to the blk_mq_ops
.init and .exit_request callbacks, pass an invalid index token. This
changes the semantics of the APIs, such that the callback would need to
validate the HW queue index before using it. Currently no user of shared
sbitmap actually uses the HW queue index (as would be expected).

Continue to use term "shared sbitmap" for now, as the meaning is known.

Signed-off-by: John Garry <john.garry@huawei.com>
---
 block/blk-mq-sched.c   | 84 +++++++++++++++++++-------------------
 block/blk-mq-tag.c     | 61 +++++++++-------------------
 block/blk-mq-tag.h     |  6 +--
 block/blk-mq.c         | 92 ++++++++++++++++++++++++------------------
 block/blk-mq.h         |  5 ++-
 include/linux/blk-mq.h | 15 ++++---
 include/linux/blkdev.h |  3 +-
 7 files changed, 127 insertions(+), 139 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 17752f39e144..428da4949d80 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -519,6 +519,11 @@ static int blk_mq_sched_alloc_map_and_rqs(struct request_queue *q,
 					  struct blk_mq_hw_ctx *hctx,
 					  unsigned int hctx_idx)
 {
+	if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
+		hctx->sched_tags = q->shared_sbitmap_tags;
+		return 0;
+	}
+
 	hctx->sched_tags = blk_mq_alloc_map_and_rqs(q->tag_set, hctx_idx,
 						    q->nr_requests);
 
@@ -527,61 +532,54 @@ static int blk_mq_sched_alloc_map_and_rqs(struct request_queue *q,
 	return 0;
 }
 
+static void blk_mq_exit_sched_shared_sbitmap(struct request_queue *queue)
+{
+	blk_mq_free_rq_map(queue->shared_sbitmap_tags);
+	queue->shared_sbitmap_tags = NULL;
+}
+
 /* called in queue's release handler, tagset has gone away */
-static void blk_mq_sched_tags_teardown(struct request_queue *q)
+static void blk_mq_sched_tags_teardown(struct request_queue *q, unsigned int flags)
 {
 	struct blk_mq_hw_ctx *hctx;
 	int i;
 
 	queue_for_each_hw_ctx(q, hctx, i) {
 		if (hctx->sched_tags) {
-			blk_mq_free_rq_map(hctx->sched_tags, hctx->flags);
+			if (!blk_mq_is_sbitmap_shared(q->tag_set->flags))
+				blk_mq_free_rq_map(hctx->sched_tags);
 			hctx->sched_tags = NULL;
 		}
 	}
+
+	if (blk_mq_is_sbitmap_shared(flags))
+		blk_mq_exit_sched_shared_sbitmap(q);
 }
 
 static int blk_mq_init_sched_shared_sbitmap(struct request_queue *queue)
 {
 	struct blk_mq_tag_set *set = queue->tag_set;
-	int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags);
-	struct blk_mq_hw_ctx *hctx;
-	int ret, i;
 
 	/*
 	 * Set initial depth at max so that we don't need to reallocate for
 	 * updating nr_requests.
 	 */
-	ret = blk_mq_init_bitmaps(&queue->sched_bitmap_tags,
-				  &queue->sched_breserved_tags,
-				  MAX_SCHED_RQ, set->reserved_tags,
-				  set->numa_node, alloc_policy);
-	if (ret)
-		return ret;
-
-	queue_for_each_hw_ctx(queue, hctx, i) {
-		hctx->sched_tags->bitmap_tags =
-					&queue->sched_bitmap_tags;
-		hctx->sched_tags->breserved_tags =
-					&queue->sched_breserved_tags;
-	}
+	queue->shared_sbitmap_tags = blk_mq_alloc_map_and_rqs(set,
+						BLK_MQ_NO_HCTX_IDX,
+						MAX_SCHED_RQ);
+	if (!queue->shared_sbitmap_tags)
+		return -ENOMEM;
 
 	blk_mq_tag_update_sched_shared_sbitmap(queue);
 
 	return 0;
 }
 
-static void blk_mq_exit_sched_shared_sbitmap(struct request_queue *queue)
-{
-	sbitmap_queue_free(&queue->sched_bitmap_tags);
-	sbitmap_queue_free(&queue->sched_breserved_tags);
-}
-
 int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
 {
+	unsigned int i, flags = q->tag_set->flags;
 	struct blk_mq_hw_ctx *hctx;
 	struct elevator_queue *eq;
-	unsigned int i;
 	int ret;
 
 	if (!e) {
@@ -598,21 +596,21 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
 	q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth,
 				   BLKDEV_DEFAULT_RQ);
 
-	queue_for_each_hw_ctx(q, hctx, i) {
-		ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i);
+	if (blk_mq_is_sbitmap_shared(flags)) {
+		ret = blk_mq_init_sched_shared_sbitmap(q);
 		if (ret)
-			goto err_free_map_and_rqs;
+			return ret;
 	}
 
-	if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
-		ret = blk_mq_init_sched_shared_sbitmap(q);
+	queue_for_each_hw_ctx(q, hctx, i) {
+		ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i);
 		if (ret)
 			goto err_free_map_and_rqs;
 	}
 
 	ret = e->ops.init_sched(q, e);
 	if (ret)
-		goto err_free_sbitmap;
+		goto err_free_map_and_rqs;
 
 	blk_mq_debugfs_register_sched(q);
 
@@ -632,12 +630,10 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
 
 	return 0;
 
-err_free_sbitmap:
-	if (blk_mq_is_sbitmap_shared(q->tag_set->flags))
-		blk_mq_exit_sched_shared_sbitmap(q);
-	blk_mq_sched_free_rqs(q);
 err_free_map_and_rqs:
-	blk_mq_sched_tags_teardown(q);
+	blk_mq_sched_free_rqs(q);
+	blk_mq_sched_tags_teardown(q, flags);
+
 	q->elevator = NULL;
 	return ret;
 }
@@ -651,9 +647,15 @@ void blk_mq_sched_free_rqs(struct request_queue *q)
 	struct blk_mq_hw_ctx *hctx;
 	int i;
 
-	queue_for_each_hw_ctx(q, hctx, i) {
-		if (hctx->sched_tags)
-			blk_mq_free_rqs(q->tag_set, hctx->sched_tags, i);
+	if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
+		blk_mq_free_rqs(q->tag_set, q->shared_sbitmap_tags,
+				BLK_MQ_NO_HCTX_IDX);
+	} else {
+		queue_for_each_hw_ctx(q, hctx, i) {
+			if (hctx->sched_tags)
+				blk_mq_free_rqs(q->tag_set,
+						hctx->sched_tags, i);
+		}
 	}
 }
 
@@ -674,8 +676,6 @@ void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
 	blk_mq_debugfs_unregister_sched(q);
 	if (e->type->ops.exit_sched)
 		e->type->ops.exit_sched(e);
-	blk_mq_sched_tags_teardown(q);
-	if (blk_mq_is_sbitmap_shared(flags))
-		blk_mq_exit_sched_shared_sbitmap(q);
+	blk_mq_sched_tags_teardown(q, flags);
 	q->elevator = NULL;
 }
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index fcc33581ce5e..29b93ea0ea27 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -27,10 +27,11 @@ bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
 	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
 		struct request_queue *q = hctx->queue;
 		struct blk_mq_tag_set *set = q->tag_set;
+		struct blk_mq_tags *tags = set->shared_sbitmap_tags;
 
 		if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) &&
 		    !test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
-			atomic_inc(&set->active_queues_shared_sbitmap);
+			atomic_inc(&tags->active_queues);
 	} else {
 		if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
 		    !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
@@ -61,10 +62,12 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
 	struct blk_mq_tag_set *set = q->tag_set;
 
 	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
+		struct blk_mq_tags *tags = set->shared_sbitmap_tags;
+
 		if (!test_and_clear_bit(QUEUE_FLAG_HCTX_ACTIVE,
 					&q->queue_flags))
 			return;
-		atomic_dec(&set->active_queues_shared_sbitmap);
+		atomic_dec(&tags->active_queues);
 	} else {
 		if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
 			return;
@@ -510,38 +513,10 @@ static int blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
 	return 0;
 }
 
-int blk_mq_init_shared_sbitmap(struct blk_mq_tag_set *set)
-{
-	int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags);
-	int i, ret;
-
-	ret = blk_mq_init_bitmaps(&set->__bitmap_tags, &set->__breserved_tags,
-				  set->queue_depth, set->reserved_tags,
-				  set->numa_node, alloc_policy);
-	if (ret)
-		return ret;
-
-	for (i = 0; i < set->nr_hw_queues; i++) {
-		struct blk_mq_tags *tags = set->tags[i];
-
-		tags->bitmap_tags = &set->__bitmap_tags;
-		tags->breserved_tags = &set->__breserved_tags;
-	}
-
-	return 0;
-}
-
-void blk_mq_exit_shared_sbitmap(struct blk_mq_tag_set *set)
-{
-	sbitmap_queue_free(&set->__bitmap_tags);
-	sbitmap_queue_free(&set->__breserved_tags);
-}
-
 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 				     unsigned int reserved_tags,
-				     int node, unsigned int flags)
+				     int node, int alloc_policy)
 {
-	int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(flags);
 	struct blk_mq_tags *tags;
 
 	if (total_tags > BLK_MQ_TAG_MAX) {
@@ -557,9 +532,6 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 	tags->nr_reserved_tags = reserved_tags;
 	spin_lock_init(&tags->lock);
 
-	if (blk_mq_is_sbitmap_shared(flags))
-		return tags;
-
 	if (blk_mq_init_bitmap_tags(tags, node, alloc_policy) < 0) {
 		kfree(tags);
 		return NULL;
@@ -567,12 +539,10 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 	return tags;
 }
 
-void blk_mq_free_tags(struct blk_mq_tags *tags, unsigned int flags)
+void blk_mq_free_tags(struct blk_mq_tags *tags)
 {
-	if (!blk_mq_is_sbitmap_shared(flags)) {
-		sbitmap_queue_free(tags->bitmap_tags);
-		sbitmap_queue_free(tags->breserved_tags);
-	}
+	sbitmap_queue_free(tags->bitmap_tags);
+	sbitmap_queue_free(tags->breserved_tags);
 	kfree(tags);
 }
 
@@ -603,6 +573,13 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 		if (tdepth > MAX_SCHED_RQ)
 			return -EINVAL;
 
+		/*
+		 * Only the sbitmap needs resizing since we allocated the max
+		 * initially.
+		 */
+		if (blk_mq_is_sbitmap_shared(set->flags))
+			return 0;
+
 		new = blk_mq_alloc_map_and_rqs(set, hctx->queue_num, tdepth);
 		if (!new)
 			return -ENOMEM;
@@ -623,12 +600,14 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 
 void blk_mq_tag_resize_shared_sbitmap(struct blk_mq_tag_set *set, unsigned int size)
 {
-	sbitmap_queue_resize(&set->__bitmap_tags, size - set->reserved_tags);
+	struct blk_mq_tags *tags = set->shared_sbitmap_tags;
+
+	sbitmap_queue_resize(&tags->__bitmap_tags, size - set->reserved_tags);
 }
 
 void blk_mq_tag_update_sched_shared_sbitmap(struct request_queue *q)
 {
-	sbitmap_queue_resize(&q->sched_bitmap_tags,
+	sbitmap_queue_resize(q->shared_sbitmap_tags->bitmap_tags,
 			     q->nr_requests - q->tag_set->reserved_tags);
 }
 
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index 88f3c6485543..e433e39a9cfa 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -30,16 +30,14 @@ struct blk_mq_tags {
 
 extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags,
 					unsigned int reserved_tags,
-					int node, unsigned int flags);
-extern void blk_mq_free_tags(struct blk_mq_tags *tags, unsigned int flags);
+					int node, int alloc_policy);
+extern void blk_mq_free_tags(struct blk_mq_tags *tags);
 extern 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);
 
-extern int blk_mq_init_shared_sbitmap(struct blk_mq_tag_set *set);
-extern void blk_mq_exit_shared_sbitmap(struct blk_mq_tag_set *set);
 extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data);
 extern void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx,
 			   unsigned int tag);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 464ea20b9bcb..1bb33a402294 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2344,7 +2344,10 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 	struct blk_mq_tags *drv_tags;
 	struct page *page;
 
-	drv_tags = set->tags[hctx_idx];
+	if (blk_mq_is_sbitmap_shared(set->flags))
+		drv_tags = set->shared_sbitmap_tags;
+	else
+		drv_tags = set->tags[hctx_idx];
 
 	if (tags->static_rqs && set->ops->exit_request) {
 		int i;
@@ -2354,6 +2357,7 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 
 			if (!rq)
 				continue;
+
 			set->ops->exit_request(set, rq, hctx_idx);
 			tags->static_rqs[i] = NULL;
 		}
@@ -2373,21 +2377,20 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 	}
 }
 
-void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags)
+void blk_mq_free_rq_map(struct blk_mq_tags *tags)
 {
 	kfree(tags->rqs);
 	tags->rqs = NULL;
 	kfree(tags->static_rqs);
 	tags->static_rqs = NULL;
 
-	blk_mq_free_tags(tags, flags);
+	blk_mq_free_tags(tags);
 }
 
 static struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
 					       unsigned int hctx_idx,
 					       unsigned int nr_tags,
-					       unsigned int reserved_tags,
-					       unsigned int flags)
+					       unsigned int reserved_tags)
 {
 	struct blk_mq_tags *tags;
 	int node;
@@ -2396,7 +2399,8 @@ 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, flags);
+	tags = blk_mq_init_tags(nr_tags, reserved_tags, node,
+				BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
 	if (!tags)
 		return NULL;
 
@@ -2404,7 +2408,7 @@ static struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
 				 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
 				 node);
 	if (!tags->rqs) {
-		blk_mq_free_tags(tags, flags);
+		blk_mq_free_tags(tags);
 		return NULL;
 	}
 
@@ -2413,7 +2417,7 @@ static struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
 					node);
 	if (!tags->static_rqs) {
 		kfree(tags->rqs);
-		blk_mq_free_tags(tags, flags);
+		blk_mq_free_tags(tags);
 		return NULL;
 	}
 
@@ -2855,14 +2859,13 @@ struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
 	struct blk_mq_tags *tags;
 	int ret;
 
-	tags = blk_mq_alloc_rq_map(set, hctx_idx, depth, set->reserved_tags,
-				   set->flags);
+	tags = blk_mq_alloc_rq_map(set, hctx_idx, depth, set->reserved_tags);
 	if (!tags)
 		return NULL;
 
 	ret = blk_mq_alloc_rqs(set, tags, hctx_idx, depth);
 	if (ret) {
-		blk_mq_free_rq_map(tags, set->flags);
+		blk_mq_free_rq_map(tags);
 		return NULL;
 	}
 
@@ -2872,6 +2875,12 @@ struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
 static bool __blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
 				       int hctx_idx)
 {
+	if (blk_mq_is_sbitmap_shared(set->flags)) {
+		set->tags[hctx_idx] = set->shared_sbitmap_tags;
+
+		return true;
+	}
+
 	set->tags[hctx_idx] = blk_mq_alloc_map_and_rqs(set, hctx_idx,
 						       set->queue_depth);
 
@@ -2882,14 +2891,22 @@ void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
 			     struct blk_mq_tags *tags,
 			     unsigned int hctx_idx)
 {
-	unsigned int flags = set->flags;
-
 	if (tags) {
 		blk_mq_free_rqs(set, tags, hctx_idx);
-		blk_mq_free_rq_map(tags, flags);
+		blk_mq_free_rq_map(tags);
 	}
 }
 
+static void __blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
+				      struct blk_mq_tags *tags,
+				      unsigned int hctx_idx)
+{
+	if (blk_mq_is_sbitmap_shared(set->flags))
+		return;
+
+	blk_mq_free_map_and_rqs(set, tags, hctx_idx);
+}
+
 static void blk_mq_map_swqueue(struct request_queue *q)
 {
 	unsigned int i, j, hctx_idx;
@@ -2968,7 +2985,7 @@ static void blk_mq_map_swqueue(struct request_queue *q)
 			 * allocation
 			 */
 			if (i && set->tags[i]) {
-				blk_mq_free_map_and_rqs(set, set->tags[i], i);
+				__blk_mq_free_map_and_rqs(set, set->tags[i], i);
 				set->tags[i] = NULL;
 			}
 
@@ -3266,7 +3283,7 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
 		struct blk_mq_hw_ctx *hctx = hctxs[j];
 
 		if (hctx) {
-			blk_mq_free_map_and_rqs(set, set->tags[j], j);
+			__blk_mq_free_map_and_rqs(set, set->tags[j], j);
 			set->tags[j] = NULL;
 			blk_mq_exit_hctx(q, set, hctx, j);
 			hctxs[j] = NULL;
@@ -3354,6 +3371,14 @@ static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
 {
 	int i;
 
+	if (blk_mq_is_sbitmap_shared(set->flags)) {
+		set->shared_sbitmap_tags = blk_mq_alloc_map_and_rqs(set,
+						BLK_MQ_NO_HCTX_IDX,
+						set->queue_depth);
+		if (!set->shared_sbitmap_tags)
+			return -ENOMEM;
+	}
+
 	for (i = 0; i < set->nr_hw_queues; i++) {
 		if (!__blk_mq_alloc_map_and_rqs(set, i))
 			goto out_unwind;
@@ -3364,10 +3389,15 @@ static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
 
 out_unwind:
 	while (--i >= 0) {
-		blk_mq_free_map_and_rqs(set, set->tags[i], i);
+		__blk_mq_free_map_and_rqs(set, set->tags[i], i);
 		set->tags[i] = NULL;
 	}
 
+	if (blk_mq_is_sbitmap_shared(set->flags)) {
+		blk_mq_free_map_and_rqs(set, set->shared_sbitmap_tags,
+					BLK_MQ_NO_HCTX_IDX);
+	}
+
 	return -ENOMEM;
 }
 
@@ -3546,25 +3576,11 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 	if (ret)
 		goto out_free_mq_map;
 
-	if (blk_mq_is_sbitmap_shared(set->flags)) {
-		atomic_set(&set->active_queues_shared_sbitmap, 0);
-
-		if (blk_mq_init_shared_sbitmap(set)) {
-			ret = -ENOMEM;
-			goto out_free_mq_rq_maps;
-		}
-	}
-
 	mutex_init(&set->tag_list_lock);
 	INIT_LIST_HEAD(&set->tag_list);
 
 	return 0;
 
-out_free_mq_rq_maps:
-	for (i = 0; i < set->nr_hw_queues; i++) {
-		blk_mq_free_map_and_rqs(set, set->tags[i], i);
-		set->tags[i] = NULL;
-	}
 out_free_mq_map:
 	for (i = 0; i < set->nr_maps; i++) {
 		kfree(set->map[i].mq_map);
@@ -3597,12 +3613,14 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
 	int i, j;
 
 	for (i = 0; i < set->nr_hw_queues; i++) {
-		blk_mq_free_map_and_rqs(set, set->tags[i], i);
+		__blk_mq_free_map_and_rqs(set, set->tags[i], i);
 		set->tags[i] = NULL;
 	}
 
-	if (blk_mq_is_sbitmap_shared(set->flags))
-		blk_mq_exit_shared_sbitmap(set);
+	if (blk_mq_is_sbitmap_shared(set->flags)) {
+		blk_mq_free_map_and_rqs(set, set->shared_sbitmap_tags,
+					BLK_MQ_NO_HCTX_IDX);
+	}
 
 	for (j = 0; j < set->nr_maps; j++) {
 		kfree(set->map[j].mq_map);
@@ -3640,12 +3658,6 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 		if (hctx->sched_tags) {
 			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
 						      nr, true);
-			if (blk_mq_is_sbitmap_shared(set->flags)) {
-				hctx->sched_tags->bitmap_tags =
-					&q->sched_bitmap_tags;
-				hctx->sched_tags->breserved_tags =
-					&q->sched_breserved_tags;
-			}
 		} else {
 			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
 						      false);
diff --git a/block/blk-mq.h b/block/blk-mq.h
index bcb0ca89d37a..b34385211e0a 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -54,7 +54,7 @@ void blk_mq_put_rq_ref(struct request *rq);
  */
 void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 		     unsigned int hctx_idx);
-void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags);
+void blk_mq_free_rq_map(struct blk_mq_tags *tags);
 struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
 				unsigned int hctx_idx, unsigned int depth);
 void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
@@ -331,10 +331,11 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
 	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
 		struct request_queue *q = hctx->queue;
 		struct blk_mq_tag_set *set = q->tag_set;
+		struct blk_mq_tags *tags = set->shared_sbitmap_tags;
 
 		if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
 			return true;
-		users = atomic_read(&set->active_queues_shared_sbitmap);
+		users = atomic_read(&tags->active_queues);
 	} else {
 		if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
 			return true;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 13ba1861e688..808854a8ebc4 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -232,13 +232,11 @@ enum hctx_type {
  * @flags:	   Zero or more BLK_MQ_F_* flags.
  * @driver_data:   Pointer to data owned by the block driver that created this
  *		   tag set.
- * @active_queues_shared_sbitmap:
- * 		   number of active request queues per tag set.
- * @__bitmap_tags: A shared tags sbitmap, used over all hctx's
- * @__breserved_tags:
- *		   A shared reserved tags sbitmap, used over all hctx's
  * @tags:	   Tag sets. One tag set per hardware queue. Has @nr_hw_queues
  *		   elements.
+ * @shared_sbitmap_tags:
+ *		   Shared sbitmap set of tags. Has @nr_hw_queues elements. If
+ *		   set, shared by all @tags.
  * @tag_list_lock: Serializes tag_list accesses.
  * @tag_list:	   List of the request queues that use this tag set. See also
  *		   request_queue.tag_set_list.
@@ -255,12 +253,11 @@ struct blk_mq_tag_set {
 	unsigned int		timeout;
 	unsigned int		flags;
 	void			*driver_data;
-	atomic_t		active_queues_shared_sbitmap;
 
-	struct sbitmap_queue	__bitmap_tags;
-	struct sbitmap_queue	__breserved_tags;
 	struct blk_mq_tags	**tags;
 
+	struct blk_mq_tags	*shared_sbitmap_tags;
+
 	struct mutex		tag_list_lock;
 	struct list_head	tag_list;
 };
@@ -432,6 +429,8 @@ enum {
 	((policy & ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1)) \
 		<< BLK_MQ_F_ALLOC_POLICY_START_BIT)
 
+#define BLK_MQ_NO_HCTX_IDX	(-1U)
+
 struct gendisk *__blk_mq_alloc_disk(struct blk_mq_tag_set *set, void *queuedata,
 		struct lock_class_key *lkclass);
 #define blk_mq_alloc_disk(set, queuedata)				\
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 4baf9435232d..17e50e5ef47b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -459,8 +459,7 @@ struct request_queue {
 
 	atomic_t		nr_active_requests_shared_sbitmap;
 
-	struct sbitmap_queue	sched_bitmap_tags;
-	struct sbitmap_queue	sched_breserved_tags;
+	struct blk_mq_tags	*shared_sbitmap_tags;
 
 	struct list_head	icq_list;
 #ifdef CONFIG_BLK_CGROUP
-- 
2.26.2

Re: [PATCH RESEND v3 12/13] blk-mq: Use shared tags for shared sbitmap support

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> Currently we use separate sbitmap pairs and active_queues atomic_t for
> shared sbitmap support.
> 
> However a full sets of static requests are used per HW queue, which is
> quite wasteful, considering that the total number of requests usable at
> any given time across all HW queues is limited by the shared sbitmap depth.
> 
> As such, it is considerably more memory efficient in the case of shared
> sbitmap to allocate a set of static rqs per tag set or request queue, and
> not per HW queue.
> 
> So replace the sbitmap pairs and active_queues atomic_t with a shared
> tags per tagset and request queue, which will hold a set of shared static
> rqs.
> 
> Since there is now no valid HW queue index to be passed to the blk_mq_ops
> .init and .exit_request callbacks, pass an invalid index token. This
> changes the semantics of the APIs, such that the callback would need to
> validate the HW queue index before using it. Currently no user of shared
> sbitmap actually uses the HW queue index (as would be expected).
> 
> Continue to use term "shared sbitmap" for now, as the meaning is known.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
>   block/blk-mq-sched.c   | 84 +++++++++++++++++++-------------------
>   block/blk-mq-tag.c     | 61 +++++++++-------------------
>   block/blk-mq-tag.h     |  6 +--
>   block/blk-mq.c         | 92 ++++++++++++++++++++++++------------------
>   block/blk-mq.h         |  5 ++-
>   include/linux/blk-mq.h | 15 ++++---
>   include/linux/blkdev.h |  3 +-
>   7 files changed, 127 insertions(+), 139 deletions(-)
> 
> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> index 17752f39e144..428da4949d80 100644
> --- a/block/blk-mq-sched.c
> +++ b/block/blk-mq-sched.c
> @@ -519,6 +519,11 @@ static int blk_mq_sched_alloc_map_and_rqs(struct request_queue *q,
>   					  struct blk_mq_hw_ctx *hctx,
>   					  unsigned int hctx_idx)
>   {
> +	if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
> +		hctx->sched_tags = q->shared_sbitmap_tags;
> +		return 0;
> +	}
> +
>   	hctx->sched_tags = blk_mq_alloc_map_and_rqs(q->tag_set, hctx_idx,
>   						    q->nr_requests);
>   
> @@ -527,61 +532,54 @@ static int blk_mq_sched_alloc_map_and_rqs(struct request_queue *q,
>   	return 0;
>   }
>   
> +static void blk_mq_exit_sched_shared_sbitmap(struct request_queue *queue)
> +{
> +	blk_mq_free_rq_map(queue->shared_sbitmap_tags);
> +	queue->shared_sbitmap_tags = NULL;
> +}
> +
>   /* called in queue's release handler, tagset has gone away */
> -static void blk_mq_sched_tags_teardown(struct request_queue *q)
> +static void blk_mq_sched_tags_teardown(struct request_queue *q, unsigned int flags)
>   {
>   	struct blk_mq_hw_ctx *hctx;
>   	int i;
>   
>   	queue_for_each_hw_ctx(q, hctx, i) {
>   		if (hctx->sched_tags) {
> -			blk_mq_free_rq_map(hctx->sched_tags, hctx->flags);
> +			if (!blk_mq_is_sbitmap_shared(q->tag_set->flags))
> +				blk_mq_free_rq_map(hctx->sched_tags);
>   			hctx->sched_tags = NULL;
>   		}
>   	}
> +
> +	if (blk_mq_is_sbitmap_shared(flags))
> +		blk_mq_exit_sched_shared_sbitmap(q);
>   }
>   
>   static int blk_mq_init_sched_shared_sbitmap(struct request_queue *queue)
>   {
>   	struct blk_mq_tag_set *set = queue->tag_set;
> -	int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags);
> -	struct blk_mq_hw_ctx *hctx;
> -	int ret, i;
>   
>   	/*
>   	 * Set initial depth at max so that we don't need to reallocate for
>   	 * updating nr_requests.
>   	 */
> -	ret = blk_mq_init_bitmaps(&queue->sched_bitmap_tags,
> -				  &queue->sched_breserved_tags,
> -				  MAX_SCHED_RQ, set->reserved_tags,
> -				  set->numa_node, alloc_policy);
> -	if (ret)
> -		return ret;
> -
> -	queue_for_each_hw_ctx(queue, hctx, i) {
> -		hctx->sched_tags->bitmap_tags =
> -					&queue->sched_bitmap_tags;
> -		hctx->sched_tags->breserved_tags =
> -					&queue->sched_breserved_tags;
> -	}
> +	queue->shared_sbitmap_tags = blk_mq_alloc_map_and_rqs(set,
> +						BLK_MQ_NO_HCTX_IDX,
> +						MAX_SCHED_RQ);
> +	if (!queue->shared_sbitmap_tags)
> +		return -ENOMEM;
>   

Any particular reason why the 'shared_sbitmap_tags' pointer is added to 
the request queue and not the tagset?
Everything else is located there, so I would have found it more logical
to add the 'shared_sbitmap_tags' pointer to the tagset, not the queue ...

>   	blk_mq_tag_update_sched_shared_sbitmap(queue);
>   
>   	return 0;
>   }
>   
> -static void blk_mq_exit_sched_shared_sbitmap(struct request_queue *queue)
> -{
> -	sbitmap_queue_free(&queue->sched_bitmap_tags);
> -	sbitmap_queue_free(&queue->sched_breserved_tags);
> -}
> -
>   int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
>   {
> +	unsigned int i, flags = q->tag_set->flags;
>   	struct blk_mq_hw_ctx *hctx;
>   	struct elevator_queue *eq;
> -	unsigned int i;
>   	int ret;
>   
>   	if (!e) {
> @@ -598,21 +596,21 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
>   	q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth,
>   				   BLKDEV_DEFAULT_RQ);
>   
> -	queue_for_each_hw_ctx(q, hctx, i) {
> -		ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i);
> +	if (blk_mq_is_sbitmap_shared(flags)) {
> +		ret = blk_mq_init_sched_shared_sbitmap(q); >   		if (ret)
> -			goto err_free_map_and_rqs;
> +			return ret;
>   	}
>   
> -	if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
> -		ret = blk_mq_init_sched_shared_sbitmap(q);
> +	queue_for_each_hw_ctx(q, hctx, i) {
> +		ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i);
>   		if (ret)
>   			goto err_free_map_and_rqs;
>   	}
>   
>   	ret = e->ops.init_sched(q, e);
>   	if (ret)
> -		goto err_free_sbitmap;
> +		goto err_free_map_and_rqs;
>   
>   	blk_mq_debugfs_register_sched(q);
>   
> @@ -632,12 +630,10 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
>   
>   	return 0;
>   
> -err_free_sbitmap:
> -	if (blk_mq_is_sbitmap_shared(q->tag_set->flags))
> -		blk_mq_exit_sched_shared_sbitmap(q);
> -	blk_mq_sched_free_rqs(q);
>   err_free_map_and_rqs:
> -	blk_mq_sched_tags_teardown(q);
> +	blk_mq_sched_free_rqs(q);
> +	blk_mq_sched_tags_teardown(q, flags);
> +
>   	q->elevator = NULL;
>   	return ret;
>   }
> @@ -651,9 +647,15 @@ void blk_mq_sched_free_rqs(struct request_queue *q)
>   	struct blk_mq_hw_ctx *hctx;
>   	int i;
>   
> -	queue_for_each_hw_ctx(q, hctx, i) {
> -		if (hctx->sched_tags)
> -			blk_mq_free_rqs(q->tag_set, hctx->sched_tags, i);
> +	if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
> +		blk_mq_free_rqs(q->tag_set, q->shared_sbitmap_tags,
> +				BLK_MQ_NO_HCTX_IDX);

'if (q->shared_sbitmap_tags)'

would be more obvious here ...

> +	} else {
> +		queue_for_each_hw_ctx(q, hctx, i) {
> +			if (hctx->sched_tags)
> +				blk_mq_free_rqs(q->tag_set,
> +						hctx->sched_tags, i);
> +		}
>   	}
>   }
>   
> @@ -674,8 +676,6 @@ void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
>   	blk_mq_debugfs_unregister_sched(q);
>   	if (e->type->ops.exit_sched)
>   		e->type->ops.exit_sched(e);
> -	blk_mq_sched_tags_teardown(q);
> -	if (blk_mq_is_sbitmap_shared(flags))
> -		blk_mq_exit_sched_shared_sbitmap(q);
> +	blk_mq_sched_tags_teardown(q, flags);
>   	q->elevator = NULL;
>   }
> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
> index fcc33581ce5e..29b93ea0ea27 100644
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -27,10 +27,11 @@ bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
>   	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
>   		struct request_queue *q = hctx->queue;
>   		struct blk_mq_tag_set *set = q->tag_set;
> +		struct blk_mq_tags *tags = set->shared_sbitmap_tags;
>   
>   		if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) &&
>   		    !test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
> -			atomic_inc(&set->active_queues_shared_sbitmap);
> +			atomic_inc(&tags->active_queues);
>   	} else {
>   		if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
>   		    !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
> @@ -61,10 +62,12 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
>   	struct blk_mq_tag_set *set = q->tag_set;
>   
>   	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
> +		struct blk_mq_tags *tags = set->shared_sbitmap_tags;
> +
>   		if (!test_and_clear_bit(QUEUE_FLAG_HCTX_ACTIVE,
>   					&q->queue_flags))
>   			return;
> -		atomic_dec(&set->active_queues_shared_sbitmap);
> +		atomic_dec(&tags->active_queues);
>   	} else {
>   		if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
>   			return;
> @@ -510,38 +513,10 @@ static int blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
>   	return 0;
>   }
>   
> -int blk_mq_init_shared_sbitmap(struct blk_mq_tag_set *set)
> -{
> -	int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags);
> -	int i, ret;
> -
> -	ret = blk_mq_init_bitmaps(&set->__bitmap_tags, &set->__breserved_tags,
> -				  set->queue_depth, set->reserved_tags,
> -				  set->numa_node, alloc_policy);
> -	if (ret)
> -		return ret;
> -
> -	for (i = 0; i < set->nr_hw_queues; i++) {
> -		struct blk_mq_tags *tags = set->tags[i];
> -
> -		tags->bitmap_tags = &set->__bitmap_tags;
> -		tags->breserved_tags = &set->__breserved_tags;
> -	}
> -
> -	return 0;
> -}
> -
> -void blk_mq_exit_shared_sbitmap(struct blk_mq_tag_set *set)
> -{
> -	sbitmap_queue_free(&set->__bitmap_tags);
> -	sbitmap_queue_free(&set->__breserved_tags);
> -}
> -
>   struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
>   				     unsigned int reserved_tags,
> -				     int node, unsigned int flags)
> +				     int node, int alloc_policy)
>   {
> -	int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(flags);
>   	struct blk_mq_tags *tags;
>   
>   	if (total_tags > BLK_MQ_TAG_MAX) {
> @@ -557,9 +532,6 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
>   	tags->nr_reserved_tags = reserved_tags;
>   	spin_lock_init(&tags->lock);
>   
> -	if (blk_mq_is_sbitmap_shared(flags))
> -		return tags;
> -
>   	if (blk_mq_init_bitmap_tags(tags, node, alloc_policy) < 0) {
>   		kfree(tags);
>   		return NULL;
> @@ -567,12 +539,10 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
>   	return tags;
>   }
>   
> -void blk_mq_free_tags(struct blk_mq_tags *tags, unsigned int flags)
> +void blk_mq_free_tags(struct blk_mq_tags *tags)
>   {
> -	if (!blk_mq_is_sbitmap_shared(flags)) {
> -		sbitmap_queue_free(tags->bitmap_tags);
> -		sbitmap_queue_free(tags->breserved_tags);
> -	}
> +	sbitmap_queue_free(tags->bitmap_tags);
> +	sbitmap_queue_free(tags->breserved_tags);
>   	kfree(tags);
>   }
>   
> @@ -603,6 +573,13 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
>   		if (tdepth > MAX_SCHED_RQ)
>   			return -EINVAL;
>   
> +		/*
> +		 * Only the sbitmap needs resizing since we allocated the max
> +		 * initially.
> +		 */
> +		if (blk_mq_is_sbitmap_shared(set->flags))
> +			return 0;
> +
>   		new = blk_mq_alloc_map_and_rqs(set, hctx->queue_num, tdepth);
>   		if (!new)
>   			return -ENOMEM;
> @@ -623,12 +600,14 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
>   
>   void blk_mq_tag_resize_shared_sbitmap(struct blk_mq_tag_set *set, unsigned int size)
>   {
> -	sbitmap_queue_resize(&set->__bitmap_tags, size - set->reserved_tags);
> +	struct blk_mq_tags *tags = set->shared_sbitmap_tags;
> +
> +	sbitmap_queue_resize(&tags->__bitmap_tags, size - set->reserved_tags);
>   }
>   
>   void blk_mq_tag_update_sched_shared_sbitmap(struct request_queue *q)
>   {
> -	sbitmap_queue_resize(&q->sched_bitmap_tags,
> +	sbitmap_queue_resize(q->shared_sbitmap_tags->bitmap_tags,
>   			     q->nr_requests - q->tag_set->reserved_tags);
>   }
>   
> diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
> index 88f3c6485543..e433e39a9cfa 100644
> --- a/block/blk-mq-tag.h
> +++ b/block/blk-mq-tag.h
> @@ -30,16 +30,14 @@ struct blk_mq_tags {
>   
>   extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags,
>   					unsigned int reserved_tags,
> -					int node, unsigned int flags);
> -extern void blk_mq_free_tags(struct blk_mq_tags *tags, unsigned int flags);
> +					int node, int alloc_policy);
> +extern void blk_mq_free_tags(struct blk_mq_tags *tags);
>   extern 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);
>   
> -extern int blk_mq_init_shared_sbitmap(struct blk_mq_tag_set *set);
> -extern void blk_mq_exit_shared_sbitmap(struct blk_mq_tag_set *set);
>   extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data);
>   extern void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx,
>   			   unsigned int tag);
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 464ea20b9bcb..1bb33a402294 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2344,7 +2344,10 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
>   	struct blk_mq_tags *drv_tags;
>   	struct page *page;
>   
> -	drv_tags = set->tags[hctx_idx];
> +	if (blk_mq_is_sbitmap_shared(set->flags))
> +		drv_tags = set->shared_sbitmap_tags;
> +	else
> +		drv_tags = set->tags[hctx_idx];
>   
>   	if (tags->static_rqs && set->ops->exit_request) {
>   		int i;
> @@ -2354,6 +2357,7 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
>   
>   			if (!rq)
>   				continue;
> +
>   			set->ops->exit_request(set, rq, hctx_idx);
>   			tags->static_rqs[i] = NULL;
>   		}

Just adding a newline?

> @@ -2373,21 +2377,20 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
>   	}
>   }
>   
> -void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags)
> +void blk_mq_free_rq_map(struct blk_mq_tags *tags)
>   {
>   	kfree(tags->rqs);
>   	tags->rqs = NULL;
>   	kfree(tags->static_rqs);
>   	tags->static_rqs = NULL;
>   
> -	blk_mq_free_tags(tags, flags);
> +	blk_mq_free_tags(tags);
>   }
>   
>   static struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
>   					       unsigned int hctx_idx,
>   					       unsigned int nr_tags,
> -					       unsigned int reserved_tags,
> -					       unsigned int flags)
> +					       unsigned int reserved_tags)
>   {
>   	struct blk_mq_tags *tags;
>   	int node;
> @@ -2396,7 +2399,8 @@ 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, flags);
> +	tags = blk_mq_init_tags(nr_tags, reserved_tags, node,
> +				BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
>   	if (!tags)
>   		return NULL;
>   
> @@ -2404,7 +2408,7 @@ static struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
>   				 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
>   				 node);
>   	if (!tags->rqs) {
> -		blk_mq_free_tags(tags, flags);
> +		blk_mq_free_tags(tags);
>   		return NULL;
>   	}
>   
> @@ -2413,7 +2417,7 @@ static struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
>   					node);
>   	if (!tags->static_rqs) {
>   		kfree(tags->rqs);
> -		blk_mq_free_tags(tags, flags);
> +		blk_mq_free_tags(tags);
>   		return NULL;
>   	}
>   
> @@ -2855,14 +2859,13 @@ struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
>   	struct blk_mq_tags *tags;
>   	int ret;
>   
> -	tags = blk_mq_alloc_rq_map(set, hctx_idx, depth, set->reserved_tags,
> -				   set->flags);
> +	tags = blk_mq_alloc_rq_map(set, hctx_idx, depth, set->reserved_tags);
>   	if (!tags)
>   		return NULL;
>   
>   	ret = blk_mq_alloc_rqs(set, tags, hctx_idx, depth);
>   	if (ret) {
> -		blk_mq_free_rq_map(tags, set->flags);
> +		blk_mq_free_rq_map(tags);
>   		return NULL;
>   	}
>   
> @@ -2872,6 +2875,12 @@ struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
>   static bool __blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
>   				       int hctx_idx)
>   {
> +	if (blk_mq_is_sbitmap_shared(set->flags)) {
> +		set->tags[hctx_idx] = set->shared_sbitmap_tags;
> +
> +		return true;
> +	}
> +
>   	set->tags[hctx_idx] = blk_mq_alloc_map_and_rqs(set, hctx_idx,
>   						       set->queue_depth);
>   
> @@ -2882,14 +2891,22 @@ void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
>   			     struct blk_mq_tags *tags,
>   			     unsigned int hctx_idx)
>   {
> -	unsigned int flags = set->flags;
> -
>   	if (tags) {
>   		blk_mq_free_rqs(set, tags, hctx_idx);
> -		blk_mq_free_rq_map(tags, flags);
> +		blk_mq_free_rq_map(tags);
>   	}
>   }
>   
> +static void __blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
> +				      struct blk_mq_tags *tags,
> +				      unsigned int hctx_idx)
> +{
> +	if (blk_mq_is_sbitmap_shared(set->flags))
> +		return;
> +
> +	blk_mq_free_map_and_rqs(set, tags, hctx_idx);
> +}
> +
>   static void blk_mq_map_swqueue(struct request_queue *q)
>   {
>   	unsigned int i, j, hctx_idx;
> @@ -2968,7 +2985,7 @@ static void blk_mq_map_swqueue(struct request_queue *q)
>   			 * allocation
>   			 */
>   			if (i && set->tags[i]) {
> -				blk_mq_free_map_and_rqs(set, set->tags[i], i);
> +				__blk_mq_free_map_and_rqs(set, set->tags[i], i);
>   				set->tags[i] = NULL;
>   			}
>   
> @@ -3266,7 +3283,7 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
>   		struct blk_mq_hw_ctx *hctx = hctxs[j];
>   
>   		if (hctx) {
> -			blk_mq_free_map_and_rqs(set, set->tags[j], j);
> +			__blk_mq_free_map_and_rqs(set, set->tags[j], j);
>   			set->tags[j] = NULL;
>   			blk_mq_exit_hctx(q, set, hctx, j);
>   			hctxs[j] = NULL;
> @@ -3354,6 +3371,14 @@ static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
>   {
>   	int i;
>   
> +	if (blk_mq_is_sbitmap_shared(set->flags)) {
> +		set->shared_sbitmap_tags = blk_mq_alloc_map_and_rqs(set,
> +						BLK_MQ_NO_HCTX_IDX,
> +						set->queue_depth);
> +		if (!set->shared_sbitmap_tags)
> +			return -ENOMEM;
> +	}
> +
>   	for (i = 0; i < set->nr_hw_queues; i++) {
>   		if (!__blk_mq_alloc_map_and_rqs(set, i))
>   			goto out_unwind;
> @@ -3364,10 +3389,15 @@ static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
>   
>   out_unwind:
>   	while (--i >= 0) {
> -		blk_mq_free_map_and_rqs(set, set->tags[i], i);
> +		__blk_mq_free_map_and_rqs(set, set->tags[i], i);
>   		set->tags[i] = NULL;
>   	}
>   
> +	if (blk_mq_is_sbitmap_shared(set->flags)) {
> +		blk_mq_free_map_and_rqs(set, set->shared_sbitmap_tags,
> +					BLK_MQ_NO_HCTX_IDX);
> +	}
> +
>   	return -ENOMEM;
>   }
>   
> @@ -3546,25 +3576,11 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
>   	if (ret)
>   		goto out_free_mq_map;
>   
> -	if (blk_mq_is_sbitmap_shared(set->flags)) {
> -		atomic_set(&set->active_queues_shared_sbitmap, 0);
> -
> -		if (blk_mq_init_shared_sbitmap(set)) {
> -			ret = -ENOMEM;
> -			goto out_free_mq_rq_maps;
> -		}
> -	}
> -
>   	mutex_init(&set->tag_list_lock);
>   	INIT_LIST_HEAD(&set->tag_list);
>   
>   	return 0;
>   
> -out_free_mq_rq_maps:
> -	for (i = 0; i < set->nr_hw_queues; i++) {
> -		blk_mq_free_map_and_rqs(set, set->tags[i], i);
> -		set->tags[i] = NULL;
> -	}
>   out_free_mq_map:
>   	for (i = 0; i < set->nr_maps; i++) {
>   		kfree(set->map[i].mq_map);
> @@ -3597,12 +3613,14 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
>   	int i, j;
>   
>   	for (i = 0; i < set->nr_hw_queues; i++) {
> -		blk_mq_free_map_and_rqs(set, set->tags[i], i);
> +		__blk_mq_free_map_and_rqs(set, set->tags[i], i);
>   		set->tags[i] = NULL;
>   	}
>   
> -	if (blk_mq_is_sbitmap_shared(set->flags))
> -		blk_mq_exit_shared_sbitmap(set);
> +	if (blk_mq_is_sbitmap_shared(set->flags)) {
> +		blk_mq_free_map_and_rqs(set, set->shared_sbitmap_tags,
> +					BLK_MQ_NO_HCTX_IDX);
> +	}
>   
>   	for (j = 0; j < set->nr_maps; j++) {
>   		kfree(set->map[j].mq_map);
> @@ -3640,12 +3658,6 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
>   		if (hctx->sched_tags) {
>   			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
>   						      nr, true);
> -			if (blk_mq_is_sbitmap_shared(set->flags)) {
> -				hctx->sched_tags->bitmap_tags =
> -					&q->sched_bitmap_tags;
> -				hctx->sched_tags->breserved_tags =
> -					&q->sched_breserved_tags;
> -			}
>   		} else {
>   			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
>   						      false);
> diff --git a/block/blk-mq.h b/block/blk-mq.h
> index bcb0ca89d37a..b34385211e0a 100644
> --- a/block/blk-mq.h
> +++ b/block/blk-mq.h
> @@ -54,7 +54,7 @@ void blk_mq_put_rq_ref(struct request *rq);
>    */
>   void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
>   		     unsigned int hctx_idx);
> -void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags);
> +void blk_mq_free_rq_map(struct blk_mq_tags *tags);
>   struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
>   				unsigned int hctx_idx, unsigned int depth);
>   void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
> @@ -331,10 +331,11 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
>   	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
>   		struct request_queue *q = hctx->queue;
>   		struct blk_mq_tag_set *set = q->tag_set;
> +		struct blk_mq_tags *tags = set->shared_sbitmap_tags;
>   
>   		if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
>   			return true;
> -		users = atomic_read(&set->active_queues_shared_sbitmap);
> +		users = atomic_read(&tags->active_queues);
>   	} else {
>   		if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
>   			return true;
> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
> index 13ba1861e688..808854a8ebc4 100644
> --- a/include/linux/blk-mq.h
> +++ b/include/linux/blk-mq.h
> @@ -232,13 +232,11 @@ enum hctx_type {
>    * @flags:	   Zero or more BLK_MQ_F_* flags.
>    * @driver_data:   Pointer to data owned by the block driver that created this
>    *		   tag set.
> - * @active_queues_shared_sbitmap:
> - * 		   number of active request queues per tag set.
> - * @__bitmap_tags: A shared tags sbitmap, used over all hctx's
> - * @__breserved_tags:
> - *		   A shared reserved tags sbitmap, used over all hctx's
>    * @tags:	   Tag sets. One tag set per hardware queue. Has @nr_hw_queues
>    *		   elements.
> + * @shared_sbitmap_tags:
> + *		   Shared sbitmap set of tags. Has @nr_hw_queues elements. If
> + *		   set, shared by all @tags.
>    * @tag_list_lock: Serializes tag_list accesses.
>    * @tag_list:	   List of the request queues that use this tag set. See also
>    *		   request_queue.tag_set_list.
> @@ -255,12 +253,11 @@ struct blk_mq_tag_set {
>   	unsigned int		timeout;
>   	unsigned int		flags;
>   	void			*driver_data;
> -	atomic_t		active_queues_shared_sbitmap;
>   
> -	struct sbitmap_queue	__bitmap_tags;
> -	struct sbitmap_queue	__breserved_tags;
>   	struct blk_mq_tags	**tags;
>   
> +	struct blk_mq_tags	*shared_sbitmap_tags;
> +
>   	struct mutex		tag_list_lock;
>   	struct list_head	tag_list;
>   };
> @@ -432,6 +429,8 @@ enum {
>   	((policy & ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1)) \
>   		<< BLK_MQ_F_ALLOC_POLICY_START_BIT)
>   
> +#define BLK_MQ_NO_HCTX_IDX	(-1U)
> +
>   struct gendisk *__blk_mq_alloc_disk(struct blk_mq_tag_set *set, void *queuedata,
>   		struct lock_class_key *lkclass);
>   #define blk_mq_alloc_disk(set, queuedata)				\
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 4baf9435232d..17e50e5ef47b 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -459,8 +459,7 @@ struct request_queue {
>   
>   	atomic_t		nr_active_requests_shared_sbitmap;
>   
> -	struct sbitmap_queue	sched_bitmap_tags;
> -	struct sbitmap_queue	sched_breserved_tags;
> +	struct blk_mq_tags	*shared_sbitmap_tags;
>   
>   	struct list_head	icq_list;
>   #ifdef CONFIG_BLK_CGROUP
> 
Why the double shared_sbitmap_tags pointer in struct request_queue and 
struct tag_set? To my knowledge there's a 1:1 relationship between 
request_queue and tag_set, so where's the point?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH RESEND v3 12/13] blk-mq: Use shared tags for shared sbitmap support

[John Garry]

...

>>    static int blk_mq_init_sched_shared_sbitmap(struct request_queue *queue)
>>    {
>>    	struct blk_mq_tag_set *set = queue->tag_set;
>> -	int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags);
>> -	struct blk_mq_hw_ctx *hctx;
>> -	int ret, i;
>>    
>>    	/*
>>    	 * Set initial depth at max so that we don't need to reallocate for
>>    	 * updating nr_requests.
>>    	 */
>> -	ret = blk_mq_init_bitmaps(&queue->sched_bitmap_tags,
>> -				  &queue->sched_breserved_tags,
>> -				  MAX_SCHED_RQ, set->reserved_tags,
>> -				  set->numa_node, alloc_policy);
>> -	if (ret)
>> -		return ret;
>> -
>> -	queue_for_each_hw_ctx(queue, hctx, i) {
>> -		hctx->sched_tags->bitmap_tags =
>> -					&queue->sched_bitmap_tags;
>> -		hctx->sched_tags->breserved_tags =
>> -					&queue->sched_breserved_tags;
>> -	}
>> +	queue->shared_sbitmap_tags = blk_mq_alloc_map_and_rqs(set,
>> +						BLK_MQ_NO_HCTX_IDX,
>> +						MAX_SCHED_RQ);
>> +	if (!queue->shared_sbitmap_tags)
>> +		return -ENOMEM;
>>    
> 
> Any particular reason why the 'shared_sbitmap_tags' pointer is added to
> the request queue and not the tagset?
> Everything else is located there, so I would have found it more logical
> to add the 'shared_sbitmap_tags' pointer to the tagset, not the queue ...
> 

We already have it for both. Since commit d97e594c5166 ("blk-mq: Use 
request queue-wide tags for tagset-wide sbitmap"), we have a "shared 
sbitmap" per tagset and per request queue. If you check d97e594c5166 
then it should explain the reason.

>>    	blk_mq_tag_update_sched_shared_sbitmap(queue);
>>    
>>    	return 0;
>>    }
>>    
>> -static void blk_mq_exit_sched_shared_sbitmap(struct request_queue *queue)
>> -{
>> -	sbitmap_queue_free(&queue->sched_bitmap_tags);
>> -	sbitmap_queue_free(&queue->sched_breserved_tags);
>> -}
>> -
>>    int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
>>    {
>> +	unsigned int i, flags = q->tag_set->flags;
>>    	struct blk_mq_hw_ctx *hctx;
>>    	struct elevator_queue *eq;
>> -	unsigned int i;
>>    	int ret;
>>    
>>    	if (!e) {
>> @@ -598,21 +596,21 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
>>    	q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth,
>>    				   BLKDEV_DEFAULT_RQ);
>>    
>> -	queue_for_each_hw_ctx(q, hctx, i) {
>> -		ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i);
>> +	if (blk_mq_is_sbitmap_shared(flags)) {
>> +		ret = blk_mq_init_sched_shared_sbitmap(q); >   		if (ret)
>> -			goto err_free_map_and_rqs;
>> +			return ret;
>>    	}
>>    
>> -	if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
>> -		ret = blk_mq_init_sched_shared_sbitmap(q);
>> +	queue_for_each_hw_ctx(q, hctx, i) {
>> +		ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i);
>>    		if (ret)
>>    			goto err_free_map_and_rqs;
>>    	}
>>    
>>    	ret = e->ops.init_sched(q, e);
>>    	if (ret)
>> -		goto err_free_sbitmap;
>> +		goto err_free_map_and_rqs;
>>    
>>    	blk_mq_debugfs_register_sched(q);
>>    
>> @@ -632,12 +630,10 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
>>    
>>    	return 0;
>>    
>> -err_free_sbitmap:
>> -	if (blk_mq_is_sbitmap_shared(q->tag_set->flags))
>> -		blk_mq_exit_sched_shared_sbitmap(q);
>> -	blk_mq_sched_free_rqs(q);
>>    err_free_map_and_rqs:
>> -	blk_mq_sched_tags_teardown(q);
>> +	blk_mq_sched_free_rqs(q);
>> +	blk_mq_sched_tags_teardown(q, flags);
>> +
>>    	q->elevator = NULL;
>>    	return ret;
>>    }
>> @@ -651,9 +647,15 @@ void blk_mq_sched_free_rqs(struct request_queue *q)
>>    	struct blk_mq_hw_ctx *hctx;
>>    	int i;
>>    
>> -	queue_for_each_hw_ctx(q, hctx, i) {
>> -		if (hctx->sched_tags)
>> -			blk_mq_free_rqs(q->tag_set, hctx->sched_tags, i);
>> +	if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) {
>> +		blk_mq_free_rqs(q->tag_set, q->shared_sbitmap_tags,
>> +				BLK_MQ_NO_HCTX_IDX);
> 
> 'if (q->shared_sbitmap_tags)'
> 
> would be more obvious here ...

I suppose so. I am just doing it this way for consistency.

> 
>> +	} else {
>> +		queue_for_each_hw_ctx(q, hctx, i) {
>> +			if (hctx->sched_tags)
>> +				blk_mq_free_rqs(q->tag_set,
>> +						hctx->sched_tags, i);
>> +		}
>>    	}
>>    }
>>    

...

>>    };
>> @@ -432,6 +429,8 @@ enum {
>>    	((policy & ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1)) \
>>    		<< BLK_MQ_F_ALLOC_POLICY_START_BIT)
>>    
>> +#define BLK_MQ_NO_HCTX_IDX	(-1U)
>> +
>>    struct gendisk *__blk_mq_alloc_disk(struct blk_mq_tag_set *set, void *queuedata,
>>    		struct lock_class_key *lkclass);
>>    #define blk_mq_alloc_disk(set, queuedata)				\
>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
>> index 4baf9435232d..17e50e5ef47b 100644
>> --- a/include/linux/blkdev.h
>> +++ b/include/linux/blkdev.h
>> @@ -459,8 +459,7 @@ struct request_queue {
>>    
>>    	atomic_t		nr_active_requests_shared_sbitmap;
>>    
>> -	struct sbitmap_queue	sched_bitmap_tags;
>> -	struct sbitmap_queue	sched_breserved_tags;
>> +	struct blk_mq_tags	*shared_sbitmap_tags;
>>    
>>    	struct list_head	icq_list;
>>    #ifdef CONFIG_BLK_CGROUP
>>
> Why the double shared_sbitmap_tags pointer in struct request_queue and
> struct tag_set? To my knowledge there's a 1:1 relationship between
> request_queue and tag_set, so where's the point?
> 

As above, we also added a shared sbitmap per request queue.

The reason being that for "shared sbitmap" support, the request queue 
total depth should not grow for an increase in the number of HW queues.

Thanks,
John

[PATCH RESEND v3 13/13] blk-mq: Stop using pointers for blk_mq_tags bitmap tags

[John Garry]

Now that we use shared tags for shared sbitmap support, we don't require
the tags sbitmap pointers, so drop them.

This essentially reverts commit 222a5ae03cdd ("blk-mq: Use pointers for
blk_mq_tags bitmap tags").

Function blk_mq_init_bitmap_tags() is removed also, since it would be only
a wrappper for blk_mq_init_bitmaps().

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: John Garry <john.garry@huawei.com>
---
 block/bfq-iosched.c    |  4 +--
 block/blk-mq-debugfs.c |  8 +++---
 block/blk-mq-tag.c     | 56 +++++++++++++++---------------------------
 block/blk-mq-tag.h     |  7 ++----
 block/blk-mq.c         |  8 +++---
 block/kyber-iosched.c  |  4 +--
 block/mq-deadline.c    |  2 +-
 7 files changed, 35 insertions(+), 54 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index dd13c2bbc29c..4674f85d7df0 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -6894,8 +6894,8 @@ static void bfq_depth_updated(struct blk_mq_hw_ctx *hctx)
 	struct blk_mq_tags *tags = hctx->sched_tags;
 	unsigned int min_shallow;
 
-	min_shallow = bfq_update_depths(bfqd, tags->bitmap_tags);
-	sbitmap_queue_min_shallow_depth(tags->bitmap_tags, min_shallow);
+	min_shallow = bfq_update_depths(bfqd, &tags->bitmap_tags);
+	sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, min_shallow);
 }
 
 static int bfq_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int index)
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 4b66d2776eda..4000376330c9 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -452,11 +452,11 @@ static void blk_mq_debugfs_tags_show(struct seq_file *m,
 		   atomic_read(&tags->active_queues));
 
 	seq_puts(m, "\nbitmap_tags:\n");
-	sbitmap_queue_show(tags->bitmap_tags, m);
+	sbitmap_queue_show(&tags->bitmap_tags, m);
 
 	if (tags->nr_reserved_tags) {
 		seq_puts(m, "\nbreserved_tags:\n");
-		sbitmap_queue_show(tags->breserved_tags, m);
+		sbitmap_queue_show(&tags->breserved_tags, m);
 	}
 }
 
@@ -487,7 +487,7 @@ static int hctx_tags_bitmap_show(void *data, struct seq_file *m)
 	if (res)
 		goto out;
 	if (hctx->tags)
-		sbitmap_bitmap_show(&hctx->tags->bitmap_tags->sb, m);
+		sbitmap_bitmap_show(&hctx->tags->bitmap_tags.sb, m);
 	mutex_unlock(&q->sysfs_lock);
 
 out:
@@ -521,7 +521,7 @@ static int hctx_sched_tags_bitmap_show(void *data, struct seq_file *m)
 	if (res)
 		goto out;
 	if (hctx->sched_tags)
-		sbitmap_bitmap_show(&hctx->sched_tags->bitmap_tags->sb, m);
+		sbitmap_bitmap_show(&hctx->sched_tags->bitmap_tags.sb, m);
 	mutex_unlock(&q->sysfs_lock);
 
 out:
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 29b93ea0ea27..a313e6869639 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -46,9 +46,9 @@ bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
  */
 void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
 {
-	sbitmap_queue_wake_all(tags->bitmap_tags);
+	sbitmap_queue_wake_all(&tags->bitmap_tags);
 	if (include_reserve)
-		sbitmap_queue_wake_all(tags->breserved_tags);
+		sbitmap_queue_wake_all(&tags->breserved_tags);
 }
 
 /*
@@ -104,10 +104,10 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 			WARN_ON_ONCE(1);
 			return BLK_MQ_NO_TAG;
 		}
-		bt = tags->breserved_tags;
+		bt = &tags->breserved_tags;
 		tag_offset = 0;
 	} else {
-		bt = tags->bitmap_tags;
+		bt = &tags->bitmap_tags;
 		tag_offset = tags->nr_reserved_tags;
 	}
 
@@ -153,9 +153,9 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 						data->ctx);
 		tags = blk_mq_tags_from_data(data);
 		if (data->flags & BLK_MQ_REQ_RESERVED)
-			bt = tags->breserved_tags;
+			bt = &tags->breserved_tags;
 		else
-			bt = tags->bitmap_tags;
+			bt = &tags->bitmap_tags;
 
 		/*
 		 * If destination hw queue is changed, fake wake up on
@@ -189,10 +189,10 @@ void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx,
 		const int real_tag = tag - tags->nr_reserved_tags;
 
 		BUG_ON(real_tag >= tags->nr_tags);
-		sbitmap_queue_clear(tags->bitmap_tags, real_tag, ctx->cpu);
+		sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
 	} else {
 		BUG_ON(tag >= tags->nr_reserved_tags);
-		sbitmap_queue_clear(tags->breserved_tags, tag, ctx->cpu);
+		sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
 	}
 }
 
@@ -343,9 +343,9 @@ static void __blk_mq_all_tag_iter(struct blk_mq_tags *tags,
 	WARN_ON_ONCE(flags & BT_TAG_ITER_RESERVED);
 
 	if (tags->nr_reserved_tags)
-		bt_tags_for_each(tags, tags->breserved_tags, fn, priv,
+		bt_tags_for_each(tags, &tags->breserved_tags, fn, priv,
 				 flags | BT_TAG_ITER_RESERVED);
-	bt_tags_for_each(tags, tags->bitmap_tags, fn, priv, flags);
+	bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, flags);
 }
 
 /**
@@ -462,8 +462,8 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
 			continue;
 
 		if (tags->nr_reserved_tags)
-			bt_for_each(hctx, tags->breserved_tags, fn, priv, true);
-		bt_for_each(hctx, tags->bitmap_tags, fn, priv, false);
+			bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
+		bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
 	}
 	blk_queue_exit(q);
 }
@@ -495,24 +495,6 @@ int blk_mq_init_bitmaps(struct sbitmap_queue *bitmap_tags,
 	return -ENOMEM;
 }
 
-static int blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
-				   int node, int alloc_policy)
-{
-	int ret;
-
-	ret = blk_mq_init_bitmaps(&tags->__bitmap_tags,
-				  &tags->__breserved_tags,
-				  tags->nr_tags, tags->nr_reserved_tags,
-				  node, alloc_policy);
-	if (ret)
-		return ret;
-
-	tags->bitmap_tags = &tags->__bitmap_tags;
-	tags->breserved_tags = &tags->__breserved_tags;
-
-	return 0;
-}
-
 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 				     unsigned int reserved_tags,
 				     int node, int alloc_policy)
@@ -532,7 +514,9 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 	tags->nr_reserved_tags = reserved_tags;
 	spin_lock_init(&tags->lock);
 
-	if (blk_mq_init_bitmap_tags(tags, node, alloc_policy) < 0) {
+	if (blk_mq_init_bitmaps(&tags->bitmap_tags, &tags->breserved_tags,
+				total_tags, reserved_tags, node,
+				alloc_policy) < 0) {
 		kfree(tags);
 		return NULL;
 	}
@@ -541,8 +525,8 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 
 void blk_mq_free_tags(struct blk_mq_tags *tags)
 {
-	sbitmap_queue_free(tags->bitmap_tags);
-	sbitmap_queue_free(tags->breserved_tags);
+	sbitmap_queue_free(&tags->bitmap_tags);
+	sbitmap_queue_free(&tags->breserved_tags);
 	kfree(tags);
 }
 
@@ -591,7 +575,7 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 		 * Don't need (or can't) update reserved tags here, they
 		 * remain static and should never need resizing.
 		 */
-		sbitmap_queue_resize(tags->bitmap_tags,
+		sbitmap_queue_resize(&tags->bitmap_tags,
 				tdepth - tags->nr_reserved_tags);
 	}
 
@@ -602,12 +586,12 @@ void blk_mq_tag_resize_shared_sbitmap(struct blk_mq_tag_set *set, unsigned int s
 {
 	struct blk_mq_tags *tags = set->shared_sbitmap_tags;
 
-	sbitmap_queue_resize(&tags->__bitmap_tags, size - set->reserved_tags);
+	sbitmap_queue_resize(&tags->bitmap_tags, size - set->reserved_tags);
 }
 
 void blk_mq_tag_update_sched_shared_sbitmap(struct request_queue *q)
 {
-	sbitmap_queue_resize(q->shared_sbitmap_tags->bitmap_tags,
+	sbitmap_queue_resize(&q->shared_sbitmap_tags->bitmap_tags,
 			     q->nr_requests - q->tag_set->reserved_tags);
 }
 
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index e433e39a9cfa..23747ea2bb53 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -11,11 +11,8 @@ struct blk_mq_tags {
 
 	atomic_t active_queues;
 
-	struct sbitmap_queue *bitmap_tags;
-	struct sbitmap_queue *breserved_tags;
-
-	struct sbitmap_queue __bitmap_tags;
-	struct sbitmap_queue __breserved_tags;
+	struct sbitmap_queue bitmap_tags;
+	struct sbitmap_queue breserved_tags;
 
 	struct request **rqs;
 	struct request **static_rqs;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1bb33a402294..13812b64ed99 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1062,14 +1062,14 @@ static inline unsigned int queued_to_index(unsigned int queued)
 
 static bool __blk_mq_get_driver_tag(struct request *rq)
 {
-	struct sbitmap_queue *bt = rq->mq_hctx->tags->bitmap_tags;
+	struct sbitmap_queue *bt = &rq->mq_hctx->tags->bitmap_tags;
 	unsigned int tag_offset = rq->mq_hctx->tags->nr_reserved_tags;
 	int tag;
 
 	blk_mq_tag_busy(rq->mq_hctx);
 
 	if (blk_mq_tag_is_reserved(rq->mq_hctx->sched_tags, rq->internal_tag)) {
-		bt = rq->mq_hctx->tags->breserved_tags;
+		bt = &rq->mq_hctx->tags->breserved_tags;
 		tag_offset = 0;
 	} else {
 		if (!hctx_may_queue(rq->mq_hctx, bt))
@@ -1112,7 +1112,7 @@ static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
 		struct sbitmap_queue *sbq;
 
 		list_del_init(&wait->entry);
-		sbq = hctx->tags->bitmap_tags;
+		sbq = &hctx->tags->bitmap_tags;
 		atomic_dec(&sbq->ws_active);
 	}
 	spin_unlock(&hctx->dispatch_wait_lock);
@@ -1130,7 +1130,7 @@ static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
 static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
 				 struct request *rq)
 {
-	struct sbitmap_queue *sbq = hctx->tags->bitmap_tags;
+	struct sbitmap_queue *sbq = &hctx->tags->bitmap_tags;
 	struct wait_queue_head *wq;
 	wait_queue_entry_t *wait;
 	bool ret;
diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index 15a8be57203d..9fb735bf1134 100644
--- a/block/kyber-iosched.c
+++ b/block/kyber-iosched.c
@@ -451,11 +451,11 @@ static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx)
 {
 	struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
 	struct blk_mq_tags *tags = hctx->sched_tags;
-	unsigned int shift = tags->bitmap_tags->sb.shift;
+	unsigned int shift = tags->bitmap_tags.sb.shift;
 
 	kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
 
-	sbitmap_queue_min_shallow_depth(tags->bitmap_tags, kqd->async_depth);
+	sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, kqd->async_depth);
 }
 
 static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index 7f3c3932b723..7fd07d00838e 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -519,7 +519,7 @@ static void dd_depth_updated(struct blk_mq_hw_ctx *hctx)
 
 	dd->async_depth = max(1UL, 3 * q->nr_requests / 4);
 
-	sbitmap_queue_min_shallow_depth(tags->bitmap_tags, dd->async_depth);
+	sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, dd->async_depth);
 }
 
 /* Called by blk_mq_init_hctx() and blk_mq_init_sched(). */
-- 
2.26.2

Re: [PATCH RESEND v3 13/13] blk-mq: Stop using pointers for blk_mq_tags bitmap tags

[Hannes Reinecke]

On 9/13/21 5:12 PM, John Garry wrote:
> Now that we use shared tags for shared sbitmap support, we don't require
> the tags sbitmap pointers, so drop them.
> 
> This essentially reverts commit 222a5ae03cdd ("blk-mq: Use pointers for
> blk_mq_tags bitmap tags").
> 
> Function blk_mq_init_bitmap_tags() is removed also, since it would be only
> a wrappper for blk_mq_init_bitmaps().
> 
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
>   block/bfq-iosched.c    |  4 +--
>   block/blk-mq-debugfs.c |  8 +++---
>   block/blk-mq-tag.c     | 56 +++++++++++++++---------------------------
>   block/blk-mq-tag.h     |  7 ++----
>   block/blk-mq.c         |  8 +++---
>   block/kyber-iosched.c  |  4 +--
>   block/mq-deadline.c    |  2 +-
>   7 files changed, 35 insertions(+), 54 deletions(-)
> A round of silent applause :-)

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH RESEND v3 00/13] blk-mq: Reduce static requests memory footprint for shared sbitmap

[John Garry]

On 13/09/2021 16:12, John Garry wrote:
> Currently a full set of static requests are allocated per hw queue per
> tagset when shared sbitmap is used.
> 
> However, only tagset->queue_depth number of requests may be active at
> any given time. As such, only tagset->queue_depth number of static
> requests are required.
> 
> The same goes for using an IO scheduler, which allocates a full set of
> static requests per hw queue per request queue.
> 
> This series changes shared sbitmap support by using a shared tags per
> tagset and request queue. Ming suggested something along those lines in
> v1 review. But we'll keep name "shared sbitmap" name as it is familiar. In
> using a shared tags, the static rqs also become shared, reducing the
> number of sets of static rqs, reducing memory usage.

Hi Ming,

Could you kindly check the remaining few un-reviewed patches in this 
series when you get an opportunity?

Thanks,
John