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

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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>
This commit is contained in:
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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18
include/linux/blk-cgroup.h
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@@ -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;
};