blkio: Implement dynamic io controlling policy registration

o One of the goals of block IO controller is that it should be able to
  support mulitple io control policies, some of which be operational at
  higher level in storage hierarchy.

o To begin with, we had one io controlling policy implemented by CFQ, and
  I hard coded the CFQ functions called by blkio. This created issues when
  CFQ is compiled as module.

o This patch implements a basic dynamic io controlling policy registration
  functionality in blkio. This is similar to elevator functionality where
  ioschedulers register the functions dynamically.

o Now in future, when more IO controlling policies are implemented, these
  can dynakically register with block IO controller.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 13 insertions, 1 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 7f3f343b0c65..78f4829895bd 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -14,7 +14,6 @@
 #include <linux/ioprio.h>
 #include <linux/blktrace_api.h>
 #include "blk-cgroup.h"
-#include "cfq-iosched.h"
 
 /*
  * tunables
@@ -3855,6 +3854,17 @@ static struct elevator_type iosched_cfq = {
         .elevator_owner =       THIS_MODULE,
 };
 
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+static struct blkio_policy_type blkio_policy_cfq = {
+        .ops = {
+                .blkio_unlink_group_fn =        cfq_unlink_blkio_group,
+                .blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
+        },
+};
+#else
+static struct blkio_policy_type blkio_policy_cfq;
+#endif
+
 static int __init cfq_init(void)
 {
         /*
@@ -3869,6 +3879,7 @@ static int __init cfq_init(void)
                 return -ENOMEM;
 
         elv_register(&iosched_cfq);
+        blkio_policy_register(&blkio_policy_cfq);
 
         return 0;
 }
@@ -3876,6 +3887,7 @@ static int __init cfq_init(void)
 static void __exit cfq_exit(void)
 {
         DECLARE_COMPLETION_ONSTACK(all_gone);
+        blkio_policy_unregister(&blkio_policy_cfq);
         elv_unregister(&iosched_cfq);
         ioc_gone = &all_gone;
         /* ioc_gone's update must be visible before reading ioc_count */