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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: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
hifive-unleashed-5.1
Tejun Heo 2015-08-18 14:55:11 -07:00 committed by Jens Axboe
parent 3e41871046
commit 001bea73e7
4 changed files with 44 additions and 21 deletions
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21
block/blk-cgroup.c
View File

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

13
block/blk-throttle.c
View File

@ -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,
};

13
block/cfq-iosched.c
View File

@ -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

18
include/linux/blk-cgroup.h
View File

@ -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;
};