io-controller: Add a new interface "weight_device" for IO-Controller

Currently, IO Controller makes use of blkio.weight to assign weight for
all devices. Here a new user interface "blkio.weight_device" is introduced to
assign different weights for different devices. blkio.weight becomes the
default value for devices which are not configured by "blkio.weight_device"

You can use the following format to assigned specific weight for a given
device:
#echo "major:minor weight" > blkio.weight_device

major:minor represents device number.

And you can remove weight for a given device as following:
#echo "major:minor 0" > blkio.weight_device

V1->V2 changes:
- use user interface "weight_device" instead of "policy" suggested by Vivek
- rename some struct suggested by Vivek
- rebase to 2.6-block "for-linus" branch
- remove an useless list_empty check pointed out by Li Zefan
- some trivial typo fix

V2->V3 changes:
- Move policy_*_node() functions up to get rid of forward declarations
- rename related functions by adding prefix "blkio_"

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index bfce085b1962..3c27bdfc97b9 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -70,6 +70,7 @@ struct blkio_cgroup {
         unsigned int weight;
         spinlock_t lock;
         struct hlist_head blkg_list;
+        struct list_head policy_list; /* list of blkio_policy_node */
 };
 
 struct blkio_group_stats {
@@ -119,6 +120,15 @@ struct blkio_group {
         struct blkio_group_stats stats;
 };
 
+struct blkio_policy_node {
+        struct list_head node;
+        dev_t dev;
+        unsigned int weight;
+};
+
+extern unsigned int blkcg_get_weight(struct blkio_cgroup *blkcg,
+                                     dev_t dev);
+
 typedef void (blkio_unlink_group_fn) (void *key, struct blkio_group *blkg);
 typedef void (blkio_update_group_weight_fn) (struct blkio_group *blkg,
                                                 unsigned int weight);