Commit 001bea73 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

blkcg: replace blkcg_policy->pd_size with ->pd_alloc/free_fn() methods 



A blkg (blkcg_gq) represents the relationship between a cgroup and
request_queue.  Each active policy has a pd (blkg_policy_data) on each
blkg.  The pd's were allocated by blkcg core and each policy could
request to allocate extra space at the end by setting
blkcg_policy->pd_size larger than the size of pd.

This is a bit unusual but was done this way mostly to simplify error
handling and all the existing use cases could be handled this way;
however, this is becoming too restrictive now that percpu memory can
be allocated without blocking.

This introduces two new mandatory blkcg_policy methods - pd_alloc_fn()
and pd_free_fn() - which are used to allocate and release pd for a
given policy.  As pd allocation is now done from policy side, it can
simply allocate a larger area which embeds pd at the beginning.  This
change makes ->pd_size pointless.  Removed.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 3e418710

block/blk-cgroup.c

+11 −10
Original line number Diff line number Diff line
@@ -68,7 +68,8 @@ static void blkg_free(struct blkcg_gq *blkg) 
		return;



	for (i = 0; i < BLKCG_MAX_POLS; i++)

		kfree(blkg->pd[i]);

		if (blkg->pd[i])

			blkcg_policy[i]->pd_free_fn(blkg->pd[i]);



	if (blkg->blkcg != &blkcg_root)

		blk_exit_rl(&blkg->rl);
@@ -114,7 +115,7 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q, 
			continue;



		/* alloc per-policy data and attach it to blkg */

		pd = kzalloc_node(pol->pd_size, gfp_mask, q->node);

		pd = pol->pd_alloc_fn(gfp_mask, q->node);

		if (!pd)

			goto err_free;
@@ -1057,7 +1058,7 @@ int blkcg_activate_policy(struct request_queue *q, 
	blk_queue_bypass_start(q);

pd_prealloc:

	if (!pd_prealloc) {

		pd_prealloc = kzalloc_node(pol->pd_size, GFP_KERNEL, q->node);

		pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q->node);

		if (!pd_prealloc) {

			ret = -ENOMEM;

			goto out_bypass_end;
@@ -1072,7 +1073,7 @@ pd_prealloc: 
		if (blkg->pd[pol->plid])

			continue;



		pd = kzalloc_node(pol->pd_size, GFP_NOWAIT, q->node);

		pd = pol->pd_alloc_fn(GFP_NOWAIT, q->node);

		if (!pd)

			swap(pd, pd_prealloc);

		if (!pd) {
@@ -1093,7 +1094,8 @@ pd_prealloc: 
	spin_unlock_irq(q->queue_lock);

out_bypass_end:

	blk_queue_bypass_end(q);

	kfree(pd_prealloc);

	if (pd_prealloc)

		pol->pd_free_fn(pd_prealloc);

	return ret;

}

EXPORT_SYMBOL_GPL(blkcg_activate_policy);
@@ -1128,8 +1130,10 @@ void blkcg_deactivate_policy(struct request_queue *q, 
		if (pol->pd_exit_fn)

			pol->pd_exit_fn(blkg);



		kfree(blkg->pd[pol->plid]);

		if (blkg->pd[pol->plid]) {

			pol->pd_free_fn(blkg->pd[pol->plid]);

			blkg->pd[pol->plid] = NULL;

		}



		spin_unlock(&blkg->blkcg->lock);

	}
@@ -1151,9 +1155,6 @@ int blkcg_policy_register(struct blkcg_policy *pol) 
	struct blkcg *blkcg;

	int i, ret;



	if (WARN_ON(pol->pd_size < sizeof(struct blkg_policy_data)))

		return -EINVAL;



	mutex_lock(&blkcg_pol_register_mutex);

	mutex_lock(&blkcg_pol_mutex);

block/blk-throttle.c

+12 −1
Original line number Diff line number Diff line
@@ -403,6 +403,11 @@ static void throtl_service_queue_exit(struct throtl_service_queue *sq) 
	del_timer_sync(&sq->pending_timer);

}



static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)

{

	return kzalloc_node(sizeof(struct throtl_grp), gfp, node);

}



static void throtl_pd_init(struct blkcg_gq *blkg)

{

	struct throtl_grp *tg = blkg_to_tg(blkg);
@@ -493,6 +498,11 @@ static void throtl_pd_exit(struct blkcg_gq *blkg) 
	throtl_service_queue_exit(&tg->service_queue);

}



static void throtl_pd_free(struct blkg_policy_data *pd)

{

	kfree(pd);

}



static void throtl_pd_reset_stats(struct blkcg_gq *blkg)

{

	struct throtl_grp *tg = blkg_to_tg(blkg);
@@ -1468,12 +1478,13 @@ static void throtl_shutdown_wq(struct request_queue *q) 
}



static struct blkcg_policy blkcg_policy_throtl = {

	.pd_size		= sizeof(struct throtl_grp),

	.cftypes		= throtl_files,



	.pd_alloc_fn		= throtl_pd_alloc,

	.pd_init_fn		= throtl_pd_init,

	.pd_online_fn		= throtl_pd_online,

	.pd_exit_fn		= throtl_pd_exit,

	.pd_free_fn		= throtl_pd_free,

	.pd_reset_stats_fn	= throtl_pd_reset_stats,

};

block/cfq-iosched.c

+12 −1
Original line number Diff line number Diff line
@@ -1582,6 +1582,11 @@ static void cfq_cpd_init(const struct blkcg *blkcg) 
	}

}



static struct blkg_policy_data *cfq_pd_alloc(gfp_t gfp, int node)

{

	return kzalloc_node(sizeof(struct cfq_group), gfp, node);

}



static void cfq_pd_init(struct blkcg_gq *blkg)

{

	struct cfq_group *cfqg = blkg_to_cfqg(blkg);
@@ -1618,6 +1623,11 @@ static void cfq_pd_offline(struct blkcg_gq *blkg) 
	cfqg_stats_xfer_dead(cfqg);

}



static void cfq_pd_free(struct blkg_policy_data *pd)

{

	return kfree(pd);

}



/* offset delta from cfqg->stats to cfqg->dead_stats */

static const int dead_stats_off_delta = offsetof(struct cfq_group, dead_stats) -

					offsetof(struct cfq_group, stats);
@@ -4633,13 +4643,14 @@ static struct elevator_type iosched_cfq = { 


#ifdef CONFIG_CFQ_GROUP_IOSCHED

static struct blkcg_policy blkcg_policy_cfq = {

	.pd_size		= sizeof(struct cfq_group),

	.cpd_size		= sizeof(struct cfq_group_data),

	.cftypes		= cfq_blkcg_files,



	.cpd_init_fn		= cfq_cpd_init,

	.pd_alloc_fn		= cfq_pd_alloc,

	.pd_init_fn		= cfq_pd_init,

	.pd_offline_fn		= cfq_pd_offline,

	.pd_free_fn		= cfq_pd_free,

	.pd_reset_stats_fn	= cfq_pd_reset_stats,

};

#endif

include/linux/blk-cgroup.h

+9 −9
Original line number Diff line number Diff line
@@ -68,13 +68,11 @@ struct blkg_rwstat { 
 * request_queue (q).  This is used by blkcg policies which need to track

 * information per blkcg - q pair.

 *

 * There can be multiple active blkcg policies and each has its private

 * data on each blkg, the size of which is determined by

 * blkcg_policy->pd_size.  blkcg core allocates and frees such areas

 * together with blkg and invokes pd_init/exit_fn() methods.

 *

 * Such private data must embed struct blkg_policy_data (pd) at the

 * beginning and pd_size can't be smaller than pd.

 * There can be multiple active blkcg policies and each blkg:policy pair is

 * represented by a blkg_policy_data which is allocated and freed by each

 * policy's pd_alloc/free_fn() methods.  A policy can allocate private data

 * area by allocating larger data structure which embeds blkg_policy_data

 * at the beginning.

 */

struct blkg_policy_data {

	/* the blkg and policy id this per-policy data belongs to */
@@ -126,16 +124,16 @@ struct blkcg_gq { 
};



typedef void (blkcg_pol_init_cpd_fn)(const struct blkcg *blkcg);

typedef struct blkg_policy_data *(blkcg_pol_alloc_pd_fn)(gfp_t gfp, int node);

typedef void (blkcg_pol_init_pd_fn)(struct blkcg_gq *blkg);

typedef void (blkcg_pol_online_pd_fn)(struct blkcg_gq *blkg);

typedef void (blkcg_pol_offline_pd_fn)(struct blkcg_gq *blkg);

typedef void (blkcg_pol_exit_pd_fn)(struct blkcg_gq *blkg);

typedef void (blkcg_pol_free_pd_fn)(struct blkg_policy_data *pd);

typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkcg_gq *blkg);



struct blkcg_policy {

	int				plid;

	/* policy specific private data size */

	size_t				pd_size;

	/* policy specific per-blkcg data size */

	size_t				cpd_size;

	/* cgroup files for the policy */
@@ -143,10 +141,12 @@ struct blkcg_policy { 


	/* operations */

	blkcg_pol_init_cpd_fn		*cpd_init_fn;

	blkcg_pol_alloc_pd_fn		*pd_alloc_fn;

	blkcg_pol_init_pd_fn		*pd_init_fn;

	blkcg_pol_online_pd_fn		*pd_online_fn;

	blkcg_pol_offline_pd_fn		*pd_offline_fn;

	blkcg_pol_exit_pd_fn		*pd_exit_fn;

	blkcg_pol_free_pd_fn		*pd_free_fn;

	blkcg_pol_reset_pd_stats_fn	*pd_reset_stats_fn;

};

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