[PATCH V2 03/13] block: move blkcg initialization/destroy into disk allocation/release handler

[Ming Lei]

blkcg works on FS bio level, so it is reasonable to make both blkcg and
gendisk sharing same lifetime. Meantime there won't be any FS IO when
releasing disk, so safe to move blkcg initialization/destroy into disk
allocation/release handler

Long term, we can move blkcg into gendisk completely.

Signed-off-by: Ming Lei <ming.lei at redhat.com>
---
 block/blk-core.c  |  5 -----
 block/blk-sysfs.c |  7 -------
 block/genhd.c     | 14 ++++++++++++++
 3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 2a400fa8cabd..d9477191b303 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -495,17 +495,12 @@ struct request_queue *blk_alloc_queue(int node_id, bool alloc_srcu)
 				PERCPU_REF_INIT_ATOMIC, GFP_KERNEL))
 		goto fail_stats;
 
-	if (blkcg_init_queue(q))
-		goto fail_ref;
-
 	blk_queue_dma_alignment(q, 511);
 	blk_set_default_limits(&q->limits);
 	q->nr_requests = BLKDEV_DEFAULT_RQ;
 
 	return q;
 
-fail_ref:
-	percpu_ref_exit(&q->q_usage_counter);
 fail_stats:
 	blk_free_queue_stats(q->stats);
 fail_split:
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index e20eadfcf5c8..6f326b44fb00 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -751,13 +751,6 @@ static void blk_exit_queue(struct request_queue *q)
 		ioc_clear_queue(q);
 		elevator_exit(q);
 	}
-
-	/*
-	 * Remove all references to @q from the block cgroup controller before
-	 * restoring @q->queue_lock to avoid that restoring this pointer causes
-	 * e.g. blkcg_print_blkgs() to crash.
-	 */
-	blkcg_exit_queue(q);
 }
 
 /**
diff --git a/block/genhd.c b/block/genhd.c
index 626c8406f21a..b9b0db168ce1 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1112,6 +1112,14 @@ static void disk_release(struct device *dev)
 	disk_release_events(disk);
 	kfree(disk->random);
 	xa_destroy(&disk->part_tbl);
+
+	/*
+	 * Remove all references to @q from the block cgroup controller before
+	 * restoring @q->queue_lock to avoid that restoring this pointer causes
+	 * e.g. blkcg_print_blkgs() to crash.
+	 */
+	blkcg_exit_queue(disk->queue);
+
 	disk->queue->disk = NULL;
 	blk_put_queue(disk->queue);
 	iput(disk->part0->bd_inode);	/* frees the disk */
@@ -1308,6 +1316,10 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
 	if (xa_insert(&disk->part_tbl, 0, disk->part0, GFP_KERNEL))
 		goto out_destroy_part_tbl;
 
+	/* todo: move blkcg into gendisk */
+	if (blkcg_init_queue(q))
+		goto out_erase_part0;
+
 	rand_initialize_disk(disk);
 	disk_to_dev(disk)->class = &block_class;
 	disk_to_dev(disk)->type = &disk_type;
@@ -1320,6 +1332,8 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
 #endif
 	return disk;
 
+out_erase_part0:
+	xa_erase(&disk->part_tbl, 0);
 out_destroy_part_tbl:
 	xa_destroy(&disk->part_tbl);
 	disk->part0->bd_disk = NULL;
-- 
2.31.1