[PATCH v3 0/3] blk-ioprio: remove per-disk structure

[PATCH v3 0/3] blk-ioprio: remove per-disk structure

[Yu Kuai]

From: Yu Kuai <yukuai3@huawei.com>

Changes in v3:
 - also fix indentation in path 1;
 - add reviewed tag by hch;

Changes in v2:
 - add patch 1;

The idea is that ioprio doesn't need to access blkg, all it needs is
blkcg, hence blk_register_policy() is enough, and blk_activate_policy()
is not needed.

Yu Kuai (3):
  blk-cgroup: check for pd_(alloc|free)_fn in blkcg_activate_policy()
  blk-ioprio: remove ioprio_blkcg_from_bio()
  blk-ioprio: remove per-disk structure

 block/blk-cgroup.c | 23 +++++++++++--------
 block/blk-ioprio.c | 57 +---------------------------------------------
 block/blk-ioprio.h |  9 --------
 3 files changed, 14 insertions(+), 75 deletions(-)

-- 
2.39.2

[PATCH v3 1/3] blk-cgroup: check for pd_(alloc|free)_fn in blkcg_activate_policy()

[Yu Kuai]

From: Yu Kuai <yukuai3@huawei.com>

Currently all policies implement pd_(alloc|free)_fn, however, this is
not necessary for ioprio that only works for blkcg, not blkg.

There are no functional changes, prepare to cleanup activating ioprio
policy.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 37e6cc91d576..3fa21b941e89 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1554,6 +1554,14 @@ int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol)
 	if (blkcg_policy_enabled(q, pol))
 		return 0;
 
+	/*
+	 * Policy is allowed to be registered without pd_alloc_fn/pd_free_fn,
+	 * for example, ioprio. Such policy will work on blkcg level, not disk
+	 * level, and don't need to be activated.
+	 */
+	if (WARN_ON_ONCE(!pol->pd_alloc_fn || !pol->pd_free_fn))
+		return -EINVAL;
+
 	if (queue_is_mq(q))
 		blk_mq_freeze_queue(q);
 retry:
@@ -1733,9 +1741,12 @@ int blkcg_policy_register(struct blkcg_policy *pol)
 		goto err_unlock;
 	}
 
-	/* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs */
+	/*
+	 * Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs, and policy
+	 * without pd_alloc_fn/pd_free_fn can't be activated.
+	 */
 	if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
-		(!pol->pd_alloc_fn ^ !pol->pd_free_fn))
+	    (!pol->pd_alloc_fn ^ !pol->pd_free_fn))
 		goto err_unlock;
 
 	/* register @pol */
-- 
2.39.2

Re: [PATCH v3 1/3] blk-cgroup: check for pd_(alloc|free)_fn in blkcg_activate_policy()

[Tejun Heo]

On Fri, Jul 19, 2024 at 03:15:04PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> Currently all policies implement pd_(alloc|free)_fn, however, this is
> not necessary for ioprio that only works for blkcg, not blkg.
> 
> There are no functional changes, prepare to cleanup activating ioprio
> policy.
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

[PATCH v3 2/3] blk-ioprio: remove ioprio_blkcg_from_bio()

[Yu Kuai]

From: Yu Kuai <yukuai3@huawei.com>

Currently, if config is enabled, then ioprio is always enabled by
default from blkcg_init_disk(), hence there is no point to check if
the policy is enabled from blkg in ioprio_blkcg_from_bio(). Hence remove
it and get blkcg directly from bio.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-ioprio.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c
index 4051fada01f1..ae52b418e984 100644
--- a/block/blk-ioprio.c
+++ b/block/blk-ioprio.c
@@ -84,16 +84,6 @@ ioprio_blkcg_from_css(struct cgroup_subsys_state *css)
 	return blkcg_to_ioprio_blkcg(css_to_blkcg(css));
 }
 
-static struct ioprio_blkcg *ioprio_blkcg_from_bio(struct bio *bio)
-{
-	struct blkg_policy_data *pd = blkg_to_pd(bio->bi_blkg, &ioprio_policy);
-
-	if (!pd)
-		return NULL;
-
-	return blkcg_to_ioprio_blkcg(pd->blkg->blkcg);
-}
-
 static int ioprio_show_prio_policy(struct seq_file *sf, void *v)
 {
 	struct ioprio_blkcg *blkcg = ioprio_blkcg_from_css(seq_css(sf));
@@ -186,7 +176,7 @@ static struct blkcg_policy ioprio_policy = {
 
 void blkcg_set_ioprio(struct bio *bio)
 {
-	struct ioprio_blkcg *blkcg = ioprio_blkcg_from_bio(bio);
+	struct ioprio_blkcg *blkcg = blkcg_to_ioprio_blkcg(bio->bi_blkg->blkcg);
 	u16 prio;
 
 	if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE)
-- 
2.39.2

Re: [PATCH v3 2/3] blk-ioprio: remove ioprio_blkcg_from_bio()

[Tejun Heo]

On Fri, Jul 19, 2024 at 03:15:05PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> Currently, if config is enabled, then ioprio is always enabled by
> default from blkcg_init_disk(), hence there is no point to check if
> the policy is enabled from blkg in ioprio_blkcg_from_bio(). Hence remove
> it and get blkcg directly from bio.
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

[PATCH v3 3/3] blk-ioprio: remove per-disk structure

[Yu Kuai]

From: Yu Kuai <yukuai3@huawei.com>

ioprio works on the blk-cgroup level, all disks in the same cgroup
are the same, and the struct ioprio_blkg doesn't have anything in it.
Hence register the policy is enough, because cpd_alloc/free_fn will
be handled for each blk-cgroup, and there is no need to activate the
policy for disk. Hence remove blk_ioprio_init/exit and
ioprio_alloc/free_pd.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.c |  8 --------
 block/blk-ioprio.c | 45 ---------------------------------------------
 block/blk-ioprio.h |  9 ---------
 3 files changed, 62 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 3fa21b941e89..c58c858aa970 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1458,7 +1458,6 @@ int blkcg_init_disk(struct gendisk *disk)
 	struct request_queue *q = disk->queue;
 	struct blkcg_gq *new_blkg, *blkg;
 	bool preloaded;
-	int ret;
 
 	new_blkg = blkg_alloc(&blkcg_root, disk, GFP_KERNEL);
 	if (!new_blkg)
@@ -1478,15 +1477,8 @@ int blkcg_init_disk(struct gendisk *disk)
 	if (preloaded)
 		radix_tree_preload_end();
 
-	ret = blk_ioprio_init(disk);
-	if (ret)
-		goto err_destroy_all;
-
 	return 0;
 
-err_destroy_all:
-	blkg_destroy_all(disk);
-	return ret;
 err_unlock:
 	spin_unlock_irq(&q->queue_lock);
 	if (preloaded)
diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c
index ae52b418e984..8fff7ccc0ac7 100644
--- a/block/blk-ioprio.c
+++ b/block/blk-ioprio.c
@@ -49,14 +49,6 @@ static const char *policy_name[] = {
 
 static struct blkcg_policy ioprio_policy;
 
-/**
- * struct ioprio_blkg - Per (cgroup, request queue) data.
- * @pd: blkg_policy_data structure.
- */
-struct ioprio_blkg {
-	struct blkg_policy_data pd;
-};
-
 /**
  * struct ioprio_blkcg - Per cgroup data.
  * @cpd: blkcg_policy_data structure.
@@ -67,11 +59,6 @@ struct ioprio_blkcg {
 	enum prio_policy	 prio_policy;
 };
 
-static inline struct ioprio_blkg *pd_to_ioprio(struct blkg_policy_data *pd)
-{
-	return pd ? container_of(pd, struct ioprio_blkg, pd) : NULL;
-}
-
 static struct ioprio_blkcg *blkcg_to_ioprio_blkcg(struct blkcg *blkcg)
 {
 	return container_of(blkcg_to_cpd(blkcg, &ioprio_policy),
@@ -108,25 +95,6 @@ static ssize_t ioprio_set_prio_policy(struct kernfs_open_file *of, char *buf,
 	return nbytes;
 }
 
-static struct blkg_policy_data *
-ioprio_alloc_pd(struct gendisk *disk, struct blkcg *blkcg, gfp_t gfp)
-{
-	struct ioprio_blkg *ioprio_blkg;
-
-	ioprio_blkg = kzalloc(sizeof(*ioprio_blkg), gfp);
-	if (!ioprio_blkg)
-		return NULL;
-
-	return &ioprio_blkg->pd;
-}
-
-static void ioprio_free_pd(struct blkg_policy_data *pd)
-{
-	struct ioprio_blkg *ioprio_blkg = pd_to_ioprio(pd);
-
-	kfree(ioprio_blkg);
-}
-
 static struct blkcg_policy_data *ioprio_alloc_cpd(gfp_t gfp)
 {
 	struct ioprio_blkcg *blkcg;
@@ -169,9 +137,6 @@ static struct blkcg_policy ioprio_policy = {
 
 	.cpd_alloc_fn	= ioprio_alloc_cpd,
 	.cpd_free_fn	= ioprio_free_cpd,
-
-	.pd_alloc_fn	= ioprio_alloc_pd,
-	.pd_free_fn	= ioprio_free_pd,
 };
 
 void blkcg_set_ioprio(struct bio *bio)
@@ -209,16 +174,6 @@ void blkcg_set_ioprio(struct bio *bio)
 		bio->bi_ioprio = prio;
 }
 
-void blk_ioprio_exit(struct gendisk *disk)
-{
-	blkcg_deactivate_policy(disk, &ioprio_policy);
-}
-
-int blk_ioprio_init(struct gendisk *disk)
-{
-	return blkcg_activate_policy(disk, &ioprio_policy);
-}
-
 static int __init ioprio_init(void)
 {
 	return blkcg_policy_register(&ioprio_policy);
diff --git a/block/blk-ioprio.h b/block/blk-ioprio.h
index b6afb8e80de0..9265143f9bc9 100644
--- a/block/blk-ioprio.h
+++ b/block/blk-ioprio.h
@@ -9,17 +9,8 @@ struct request_queue;
 struct bio;
 
 #ifdef CONFIG_BLK_CGROUP_IOPRIO
-int blk_ioprio_init(struct gendisk *disk);
-void blk_ioprio_exit(struct gendisk *disk);
 void blkcg_set_ioprio(struct bio *bio);
 #else
-static inline int blk_ioprio_init(struct gendisk *disk)
-{
-	return 0;
-}
-static inline void blk_ioprio_exit(struct gendisk *disk)
-{
-}
 static inline void blkcg_set_ioprio(struct bio *bio)
 {
 }
-- 
2.39.2

Re: [PATCH v3 3/3] blk-ioprio: remove per-disk structure

[Tejun Heo]

On Fri, Jul 19, 2024 at 03:15:06PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> ioprio works on the blk-cgroup level, all disks in the same cgroup
> are the same, and the struct ioprio_blkg doesn't have anything in it.
> Hence register the policy is enough, because cpd_alloc/free_fn will
> be handled for each blk-cgroup, and there is no need to activate the
> policy for disk. Hence remove blk_ioprio_init/exit and
> ioprio_alloc/free_pd.
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

Re: [PATCH v3 0/3] blk-ioprio: remove per-disk structure

[Jens Axboe]

On Fri, 19 Jul 2024 15:15:03 +0800, Yu Kuai wrote:
> Changes in v3:
>  - also fix indentation in path 1;
>  - add reviewed tag by hch;
> 
> Changes in v2:
>  - add patch 1;
> 
> [...]

Applied, thanks!

[1/3] blk-cgroup: check for pd_(alloc|free)_fn in blkcg_activate_policy()
      commit: b925680cf08356a27ab83c0b707c0fcf61ab0bb9
[2/3] blk-ioprio: remove ioprio_blkcg_from_bio()
      commit: 746af0f4f529ba40bfa474c5b7509bd52f9863d9
[3/3] blk-ioprio: remove per-disk structure
      commit: 19c8bb716c283093a355a95a4162dc6a880dbeb0

Best regards,
-- 
Jens Axboe