blkcg: add request_queue->root_blkg

With per-queue policy activation, root blkg creation will be moved to
blkcg core.  Add q->root_blkg in preparation.  For blk-throtl, this
replaces throtl_data->root_tg; however, cfq needs to keep
cfqd->root_group for !CONFIG_CFQ_GROUP_IOSCHED.

This is to prepare for per-queue policy activation and doesn't cause
any functional difference.

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, 2 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d2c69f8c188..b01c377fd73 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -31,6 +31,7 @@ struct blk_trace;
 struct request;
 struct sg_io_hdr;
 struct bsg_job;
+struct blkio_group;
 
 #define BLKDEV_MIN_RQ   4
 #define BLKDEV_MAX_RQ   128     /* Default maximum */
@@ -369,6 +370,7 @@ struct request_queue {
 
         struct list_head        icq_list;
 #ifdef CONFIG_BLK_CGROUP
+        struct blkio_group      *root_blkg;
         struct list_head        blkg_list;
 #endif