blkcg: add blkcg_{init|drain|exit}_queue()

Currently block core calls directly into blk-throttle for init, drain
and exit.  This patch adds blkcg_{init|drain|exit}_queue() which wraps
the blk-throttle functions.  This is to give more control and
visiblity to blkcg core layer for proper layering.  Further patches
will add logic common to blkcg policies to the functions.

While at it, collapse blk_throtl_release() into blk_throtl_exit().
There's no reason to keep them separate.

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, 42 insertions, 0 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index d42d826ece39..b302ce1d662b 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -20,6 +20,7 @@
 #include <linux/genhd.h>
 #include <linux/delay.h>
 #include "blk-cgroup.h"
+#include "blk.h"
 
 #define MAX_KEY_LEN 100
 
@@ -1459,6 +1460,47 @@ done:
         return &blkcg->css;
 }
 
+/**
+ * blkcg_init_queue - initialize blkcg part of request queue
+ * @q: request_queue to initialize
+ *
+ * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
+ * part of new request_queue @q.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int blkcg_init_queue(struct request_queue *q)
+{
+        might_sleep();
+
+        return blk_throtl_init(q);
+}
+
+/**
+ * blkcg_drain_queue - drain blkcg part of request_queue
+ * @q: request_queue to drain
+ *
+ * Called from blk_drain_queue().  Responsible for draining blkcg part.
+ */
+void blkcg_drain_queue(struct request_queue *q)
+{
+        lockdep_assert_held(q->queue_lock);
+
+        blk_throtl_drain(q);
+}
+
+/**
+ * blkcg_exit_queue - exit and release blkcg part of request_queue
+ * @q: request_queue being released
+ *
+ * Called from blk_release_queue().  Responsible for exiting blkcg part.
+ */
+void blkcg_exit_queue(struct request_queue *q)
+{
+        blk_throtl_exit(q);
+}
+
 /*
  * We cannot support shared io contexts, as we have no mean to support
  * two tasks with the same ioc in two different groups without major rework