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Subject[PATCH 3/8] blkcg: remove static policy ID enums
Date
Remove BLKIO_POLICY_* enums and let blkio_policy_register() allocate
@pol->plid dynamically on registration. The maximum number of blkcg
policies which can be registered at the same time is defined by
BLKCG_MAX_POLS constant added to include/linux/blkdev.h.

Note that blkio_policy_register() now may fail. Policy init functions
updated accordingly and unnecessary ifdefs removed from cfq_init().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
---
block/blk-cgroup.c | 59 +++++++++++++++++++++++++++++++++++------------
block/blk-cgroup.h | 15 +++---------
block/blk-throttle.c | 4 +--
block/cfq-iosched.c | 25 +++++++++++---------
include/linux/blkdev.h | 7 +++++-
5 files changed, 69 insertions(+), 41 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b123152..2d4d7d6 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -31,7 +31,7 @@ static LIST_HEAD(all_q_list);
struct blkio_cgroup blkio_root_cgroup = { .cfq_weight = 2 * CFQ_WEIGHT_DEFAULT };
EXPORT_SYMBOL_GPL(blkio_root_cgroup);

-static struct blkio_policy_type *blkio_policy[BLKIO_NR_POLICIES];
+static struct blkio_policy_type *blkio_policy[BLKCG_MAX_POLS];

struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
{
@@ -67,7 +67,7 @@ static void blkg_free(struct blkio_group *blkg)
if (!blkg)
return;

- for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkio_policy_type *pol = blkio_policy[i];
struct blkg_policy_data *pd = blkg->pd[i];

@@ -107,7 +107,7 @@ static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
blkg->refcnt = 1;
cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));

- for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkio_policy_type *pol = blkio_policy[i];
struct blkg_policy_data *pd;

@@ -127,7 +127,7 @@ static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
}

/* invoke per-policy init */
- for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkio_policy_type *pol = blkio_policy[i];

if (pol)
@@ -320,7 +320,7 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
* anyway. If you get hit by a race, retry.
*/
hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
- for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkio_policy_type *pol = blkio_policy[i];

if (pol && pol->ops.blkio_reset_group_stats_fn)
@@ -729,46 +729,75 @@ struct cgroup_subsys blkio_subsys = {
};
EXPORT_SYMBOL_GPL(blkio_subsys);

-void blkio_policy_register(struct blkio_policy_type *blkiop)
+/**
+ * blkio_policy_register - register a blkcg policy
+ * @blkiop: blkcg policy to register
+ *
+ * Register @blkiop with blkcg core. Might sleep and @blkiop may be
+ * modified on successful registration. Returns 0 on success and -errno on
+ * failure.
+ */
+int blkio_policy_register(struct blkio_policy_type *blkiop)
{
struct request_queue *q;
+ int i, ret;

mutex_lock(&blkcg_pol_mutex);

- blkcg_bypass_start();
+ /* find an empty slot */
+ ret = -ENOSPC;
+ for (i = 0; i < BLKCG_MAX_POLS; i++)
+ if (!blkio_policy[i])
+ break;
+ if (i >= BLKCG_MAX_POLS)
+ goto out_unlock;

- BUG_ON(blkio_policy[blkiop->plid]);
- blkio_policy[blkiop->plid] = blkiop;
+ /* register and update blkgs */
+ blkiop->plid = i;
+ blkio_policy[i] = blkiop;
+
+ blkcg_bypass_start();
list_for_each_entry(q, &all_q_list, all_q_node)
update_root_blkg_pd(q, blkiop);
-
blkcg_bypass_end();

+ /* everything is in place, add intf files for the new policy */
if (blkiop->cftypes)
WARN_ON(cgroup_add_cftypes(&blkio_subsys, blkiop->cftypes));
-
+ ret = 0;
+out_unlock:
mutex_unlock(&blkcg_pol_mutex);
+ return ret;
}
EXPORT_SYMBOL_GPL(blkio_policy_register);

+/**
+ * blkiop_policy_unregister - unregister a blkcg policy
+ * @blkiop: blkcg policy to unregister
+ *
+ * Undo blkio_policy_register(@blkiop). Might sleep.
+ */
void blkio_policy_unregister(struct blkio_policy_type *blkiop)
{
struct request_queue *q;

mutex_lock(&blkcg_pol_mutex);

+ if (WARN_ON(blkio_policy[blkiop->plid] != blkiop))
+ goto out_unlock;
+
+ /* kill the intf files first */
if (blkiop->cftypes)
cgroup_rm_cftypes(&blkio_subsys, blkiop->cftypes);

- blkcg_bypass_start();
-
- BUG_ON(blkio_policy[blkiop->plid] != blkiop);
+ /* unregister and update blkgs */
blkio_policy[blkiop->plid] = NULL;

+ blkcg_bypass_start();
list_for_each_entry(q, &all_q_list, all_q_node)
update_root_blkg_pd(q, blkiop);
blkcg_bypass_end();
-
+out_unlock:
mutex_unlock(&blkcg_pol_mutex);
}
EXPORT_SYMBOL_GPL(blkio_policy_unregister);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 49116d3..cacdcaea 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -17,13 +17,6 @@
#include <linux/u64_stats_sync.h>
#include <linux/seq_file.h>

-enum blkio_policy_id {
- BLKIO_POLICY_PROP = 0, /* Proportional Bandwidth division */
- BLKIO_POLICY_THROTL, /* Throttling */
-
- BLKIO_NR_POLICIES,
-};
-
/* Max limits for throttle policy */
#define THROTL_IOPS_MAX UINT_MAX

@@ -86,7 +79,7 @@ struct blkio_group {
/* reference count */
int refcnt;

- struct blkg_policy_data *pd[BLKIO_NR_POLICIES];
+ struct blkg_policy_data *pd[BLKCG_MAX_POLS];

struct rcu_head rcu_head;
};
@@ -103,7 +96,7 @@ struct blkio_policy_ops {

struct blkio_policy_type {
struct blkio_policy_ops ops;
- enum blkio_policy_id plid;
+ int plid;
size_t pdata_size; /* policy specific private data size */
struct cftype *cftypes; /* cgroup files for the policy */
};
@@ -113,7 +106,7 @@ extern void blkcg_drain_queue(struct request_queue *q);
extern void blkcg_exit_queue(struct request_queue *q);

/* Blkio controller policy registration */
-extern void blkio_policy_register(struct blkio_policy_type *);
+extern int blkio_policy_register(struct blkio_policy_type *);
extern void blkio_policy_unregister(struct blkio_policy_type *);
extern void blkg_destroy_all(struct request_queue *q, bool destroy_root);
extern void update_root_blkg_pd(struct request_queue *q,
@@ -329,7 +322,7 @@ struct blkio_policy_type {
static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
static inline void blkcg_drain_queue(struct request_queue *q) { }
static inline void blkcg_exit_queue(struct request_queue *q) { }
-static inline void blkio_policy_register(struct blkio_policy_type *blkiop) { }
+static inline int blkio_policy_register(struct blkio_policy_type *blkiop) { return 0; }
static inline void blkio_policy_unregister(struct blkio_policy_type *blkiop) { }
static inline void blkg_destroy_all(struct request_queue *q,
bool destory_root) { }
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 07c17c2..0dc4645 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1089,7 +1089,6 @@ static struct blkio_policy_type blkio_policy_throtl = {
.blkio_exit_group_fn = throtl_exit_blkio_group,
.blkio_reset_group_stats_fn = throtl_reset_group_stats,
},
- .plid = BLKIO_POLICY_THROTL,
.pdata_size = sizeof(struct throtl_grp),
.cftypes = throtl_files,
};
@@ -1271,8 +1270,7 @@ static int __init throtl_init(void)
if (!kthrotld_workqueue)
panic("Failed to create kthrotld\n");

- blkio_policy_register(&blkio_policy_throtl);
- return 0;
+ return blkio_policy_register(&blkio_policy_throtl);
}

module_init(throtl_init);
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 7980173..a0fbc51 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -4158,7 +4158,6 @@ static struct blkio_policy_type blkio_policy_cfq = {
.blkio_init_group_fn = cfq_init_blkio_group,
.blkio_reset_group_stats_fn = cfqg_stats_reset,
},
- .plid = BLKIO_POLICY_PROP,
.pdata_size = sizeof(struct cfq_group),
.cftypes = cfq_blkcg_files,
};
@@ -4182,27 +4181,31 @@ static int __init cfq_init(void)
#else
cfq_group_idle = 0;
#endif
+
+ ret = blkio_policy_register(&blkio_policy_cfq);
+ if (ret)
+ return ret;
+
cfq_pool = KMEM_CACHE(cfq_queue, 0);
if (!cfq_pool)
- return -ENOMEM;
+ goto err_pol_unreg;

ret = elv_register(&iosched_cfq);
- if (ret) {
- kmem_cache_destroy(cfq_pool);
- return ret;
- }
+ if (ret)
+ goto err_free_pool;

-#ifdef CONFIG_CFQ_GROUP_IOSCHED
- blkio_policy_register(&blkio_policy_cfq);
-#endif
return 0;
+
+err_free_pool:
+ kmem_cache_destroy(cfq_pool);
+err_pol_unreg:
+ blkio_policy_unregister(&blkio_policy_cfq);
+ return ret;
}

static void __exit cfq_exit(void)
{
-#ifdef CONFIG_CFQ_GROUP_IOSCHED
blkio_policy_unregister(&blkio_policy_cfq);
-#endif
elv_unregister(&iosched_cfq);
kmem_cache_destroy(cfq_pool);
}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 33f1b29..d2c69f8 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -35,6 +35,12 @@ struct bsg_job;
#define BLKDEV_MIN_RQ 4
#define BLKDEV_MAX_RQ 128 /* Default maximum */

+/*
+ * Maximum number of blkcg policies allowed to be registered concurrently.
+ * Defined here to simplify include dependency.
+ */
+#define BLKCG_MAX_POLS 2
+
struct request;
typedef void (rq_end_io_fn)(struct request *, int);

@@ -363,7 +369,6 @@ struct request_queue {

struct list_head icq_list;
#ifdef CONFIG_BLK_CGROUP
- /* XXX: array size hardcoded to avoid include dependency (temporary) */
struct list_head blkg_list;
#endif

--
1.7.7.3


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