blkcg: remove static policy ID enums

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>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 4 insertions, 11 deletions

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 26949731108f..be80d6eb6531 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) { }