[PATCH 1/4] blkio_group key change: void * -> request_queue *

[Chad Talbott <ctalbott@google.com>]

Use request_queue to find the blkio_group of a device, rather than a
cfq_data pointer.  Additionally, it allows the blk-cgroup code to
depend on the queue pointer itself.  This avoids doing lookups for
dev_t and facilitates looking up the device's human-readable name in
later patches.
---
 block/blk-cgroup.c  |   17 ++++++++---------
 block/blk-cgroup.h  |   13 +++++++------
 block/cfq-iosched.c |   22 ++++++++++------------
 3 files changed, 25 insertions(+), 27 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 4b686ad..917957d 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -15,6 +15,7 @@
 #include <linux/kdev_t.h>
 #include <linux/module.h>
 #include <linux/err.h>
+#include <linux/genhd.h>
 #include "blk-cgroup.h"
 
 static DEFINE_SPINLOCK(blkio_list_lock);
@@ -64,12 +65,12 @@ void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
 EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_stats);
 
 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
-			struct blkio_group *blkg, void *key, dev_t dev)
+			struct blkio_group *blkg, struct request_queue *queue, dev_t dev)
 {
 	unsigned long flags;
 
 	spin_lock_irqsave(&blkcg->lock, flags);
-	rcu_assign_pointer(blkg->key, key);
+	rcu_assign_pointer(blkg->queue, queue);
 	blkg->blkcg_id = css_id(&blkcg->css);
 	hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
 	spin_unlock_irqrestore(&blkcg->lock, flags);
@@ -117,15 +118,15 @@ out:
 EXPORT_SYMBOL_GPL(blkiocg_del_blkio_group);
 
 /* called under rcu_read_lock(). */
-struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
+struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, struct request_queue *queue)
 {
 	struct blkio_group *blkg;
 	struct hlist_node *n;
-	void *__key;
+	struct request_queue *__queue;
 
 	hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
-		__key = blkg->key;
-		if (__key == key)
+		__queue = blkg->queue;
+		if (__queue == queue)
 			return blkg;
 	}
 
@@ -243,7 +244,6 @@ static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 	struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
 	unsigned long flags;
 	struct blkio_group *blkg;
-	void *key;
 	struct blkio_policy_type *blkiop;
 
 	rcu_read_lock();
@@ -257,7 +257,6 @@ remove_entry:
 
 	blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
 				blkcg_node);
-	key = rcu_dereference(blkg->key);
 	__blkiocg_del_blkio_group(blkg);
 
 	spin_unlock_irqrestore(&blkcg->lock, flags);
@@ -272,7 +271,7 @@ remove_entry:
 	 */
 	spin_lock(&blkio_list_lock);
 	list_for_each_entry(blkiop, &blkio_list, list)
-		blkiop->ops.blkio_unlink_group_fn(key, blkg);
+		blkiop->ops.blkio_unlink_group_fn(blkg);
 	spin_unlock(&blkio_list_lock);
 	goto remove_entry;
 done:
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 8ccc204..9e70c03 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -14,6 +14,7 @@
  */
 
 #include <linux/cgroup.h>
+#include <linux/blkdev.h>
 
 #if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE)
 
@@ -32,7 +33,7 @@ struct blkio_cgroup {
 
 struct blkio_group {
 	/* An rcu protected unique identifier for the group */
-	void *key;
+	struct request_queue *queue;
 	struct hlist_node blkcg_node;
 	unsigned short blkcg_id;
 #ifdef CONFIG_DEBUG_BLK_CGROUP
@@ -49,7 +50,7 @@ struct blkio_group {
 	unsigned long sectors;
 };
 
-typedef void (blkio_unlink_group_fn) (void *key, struct blkio_group *blkg);
+typedef void (blkio_unlink_group_fn) (struct blkio_group *blkg);
 typedef void (blkio_update_group_weight_fn) (struct blkio_group *blkg,
 						unsigned int weight);
 
@@ -101,10 +102,10 @@ static inline void blkiocg_update_blkio_group_dequeue_stats(
 extern struct blkio_cgroup blkio_root_cgroup;
 extern struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup);
 extern void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
-			struct blkio_group *blkg, void *key, dev_t dev);
+			struct blkio_group *blkg, struct request_queue *queue, dev_t dev);
 extern int blkiocg_del_blkio_group(struct blkio_group *blkg);
 extern struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg,
-						void *key);
+						struct request_queue *queue);
 void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
 			unsigned long time, unsigned long sectors);
 #else
@@ -113,7 +114,7 @@ static inline struct blkio_cgroup *
 cgroup_to_blkio_cgroup(struct cgroup *cgroup) { return NULL; }
 
 static inline void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
-			struct blkio_group *blkg, void *key, dev_t dev)
+			struct blkio_group *blkg, struct request_queue *queue, dev_t dev)
 {
 }
 
@@ -121,7 +122,7 @@ static inline int
 blkiocg_del_blkio_group(struct blkio_group *blkg) { return 0; }
 
 static inline struct blkio_group *
-blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key) { return NULL; }
+blkiocg_lookup_group(struct blkio_cgroup *blkcg, struct request_queue *queue) { return NULL; }
 static inline void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
 			unsigned long time, unsigned long sectors)
 {
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index dee9d93..864b39a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -940,13 +940,13 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
 {
 	struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
 	struct cfq_group *cfqg = NULL;
-	void *key = cfqd;
+	struct request_queue *queue = cfqd->queue;
 	int i, j;
 	struct cfq_rb_root *st;
 	struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
 	unsigned int major, minor;
 
-	cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
+	cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, queue));
 	if (cfqg || !create)
 		goto done;
 
@@ -969,7 +969,7 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
 
 	/* Add group onto cgroup list */
 	sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
-	blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
+	blkiocg_add_blkio_group(blkcg, &cfqg->blkg, cfqd->queue,
 					MKDEV(major, minor));
 
 	/* Add group on cfqd list */
@@ -1021,7 +1021,7 @@ static void cfq_put_cfqg(struct cfq_group *cfqg)
 	kfree(cfqg);
 }
 
-static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
+static void cfq_destroy_cfqg(struct cfq_group *cfqg)
 {
 	/* Something wrong if we are trying to remove same group twice */
 	BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
@@ -1047,7 +1047,7 @@ static void cfq_release_cfq_groups(struct cfq_data *cfqd)
 		 * cfqg also.
 		 */
 		if (!blkiocg_del_blkio_group(&cfqg->blkg))
-			cfq_destroy_cfqg(cfqd, cfqg);
+			cfq_destroy_cfqg(cfqg);
 	}
 }
 
@@ -1065,14 +1065,13 @@ static void cfq_release_cfq_groups(struct cfq_data *cfqd)
  * it should not be NULL as even if elevator was exiting, cgroup deltion
  * path got to it first.
  */
-void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
+void cfq_unlink_blkio_group(struct blkio_group *blkg)
 {
 	unsigned long  flags;
-	struct cfq_data *cfqd = key;
 
-	spin_lock_irqsave(cfqd->queue->queue_lock, flags);
-	cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
-	spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
+	spin_lock_irqsave(blkg->queue->queue_lock, flags);
+	cfq_destroy_cfqg(cfqg_of_blkg(blkg));
+	spin_unlock_irqrestore(blkg->queue->queue_lock, flags);
 }
 
 #else /* GROUP_IOSCHED */
@@ -3672,8 +3671,7 @@ static void *cfq_init_queue(struct request_queue *q)
 	 * to make sure that cfq_put_cfqg() does not try to kfree root group
 	 */
 	atomic_set(&cfqg->ref, 1);
-	blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd,
-					0);
+	blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, q, 0);
 #endif
 	/*
 	 * Not strictly needed (since RB_ROOT just clears the node and we