blk-cgroup: pin the gendisk in struct blkcg_gq

Currently each blkcg_gq holds a request_queue reference, which is what
is used in the policies.  But a lot of these interfaces will move over to
use a gendisk, so store a disk in struct blkcg_gq and hold a reference to
it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Andreas Herrmann <aherrmann@suse.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230203150400.3199230-7-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 17 insertions, 18 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 0b3226cbf3f2..0e368387497d 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -116,7 +116,6 @@ static bool blkcg_policy_enabled(struct request_queue *q,
 
 static void blkg_free(struct blkcg_gq *blkg)
 {
-	struct request_queue *q = blkg->q;
 	int i;
 
 	/*
@@ -126,16 +125,16 @@ static void blkg_free(struct blkcg_gq *blkg)
 	 * blkcg_mutex is used to synchronize blkg_free_workfn() and
 	 * blkcg_deactivate_policy().
 	 */
-	mutex_lock(&q->blkcg_mutex);
+	mutex_lock(&blkg->disk->queue->blkcg_mutex);
 	for (i = 0; i < BLKCG_MAX_POLS; i++)
 		if (blkg->pd[i])
 			blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
 	if (blkg->parent)
 		blkg_put(blkg->parent);
 	list_del_init(&blkg->q_node);
-	mutex_unlock(&q->blkcg_mutex);
+	mutex_unlock(&blkg->disk->queue->blkcg_mutex);
 
-	blk_put_queue(q);
+	put_disk(blkg->disk);
 	free_percpu(blkg->iostat_cpu);
 	percpu_ref_exit(&blkg->refcnt);
 	kfree(blkg);
@@ -251,10 +250,12 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk,
 	blkg->iostat_cpu = alloc_percpu_gfp(struct blkg_iostat_set, gfp_mask);
 	if (!blkg->iostat_cpu)
 		goto out_exit_refcnt;
-	if (!blk_get_queue(disk->queue))
+
+	if (test_bit(GD_DEAD, &disk->state))
 		goto out_free_iostat;
+	get_device(disk_to_dev(disk));
+	blkg->disk = disk;
 
-	blkg->q = disk->queue;
 	INIT_LIST_HEAD(&blkg->q_node);
 	spin_lock_init(&blkg->async_bio_lock);
 	bio_list_init(&blkg->async_bios);
@@ -290,7 +291,7 @@ out_free_pds:
 	while (--i >= 0)
 		if (blkg->pd[i])
 			blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
-	blk_put_queue(disk->queue);
+	put_disk(blkg->disk);
 out_free_iostat:
 	free_percpu(blkg->iostat_cpu);
 out_exit_refcnt:
@@ -461,7 +462,7 @@ static void blkg_destroy(struct blkcg_gq *blkg)
 	struct blkcg *blkcg = blkg->blkcg;
 	int i;
 
-	lockdep_assert_held(&blkg->q->queue_lock);
+	lockdep_assert_held(&blkg->disk->queue->queue_lock);
 	lockdep_assert_held(&blkcg->lock);
 
 	/*
@@ -485,7 +486,7 @@ static void blkg_destroy(struct blkcg_gq *blkg)
 
 	blkg->online = false;
 
-	radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
+	radix_tree_delete(&blkcg->blkg_tree, blkg->disk->queue->id);
 	hlist_del_init_rcu(&blkg->blkcg_node);
 
 	/*
@@ -572,9 +573,7 @@ static int blkcg_reset_stats(struct cgroup_subsys_state *css,
 
 const char *blkg_dev_name(struct blkcg_gq *blkg)
 {
-	if (!blkg->q->disk)
-		return NULL;
-	return bdi_dev_name(blkg->q->disk->bdi);
+	return bdi_dev_name(blkg->disk->bdi);
 }
 
 /**
@@ -606,10 +605,10 @@ void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
 
 	rcu_read_lock();
 	hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
-		spin_lock_irq(&blkg->q->queue_lock);
-		if (blkcg_policy_enabled(blkg->q, pol))
+		spin_lock_irq(&blkg->disk->queue->queue_lock);
+		if (blkcg_policy_enabled(blkg->disk->queue, pol))
 			total += prfill(sf, blkg->pd[pol->plid], data);
-		spin_unlock_irq(&blkg->q->queue_lock);
+		spin_unlock_irq(&blkg->disk->queue->queue_lock);
 	}
 	rcu_read_unlock();
 
@@ -1033,9 +1032,9 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
 
 	rcu_read_lock();
 	hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
-		spin_lock_irq(&blkg->q->queue_lock);
+		spin_lock_irq(&blkg->disk->queue->queue_lock);
 		blkcg_print_one_stat(blkg, sf);
-		spin_unlock_irq(&blkg->q->queue_lock);
+		spin_unlock_irq(&blkg->disk->queue->queue_lock);
 	}
 	rcu_read_unlock();
 	return 0;
@@ -1105,7 +1104,7 @@ static void blkcg_destroy_blkgs(struct blkcg *blkcg)
 	while (!hlist_empty(&blkcg->blkg_list)) {
 		struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
 						struct blkcg_gq, blkcg_node);
-		struct request_queue *q = blkg->q;
+		struct request_queue *q = blkg->disk->queue;
 
 		if (need_resched() || !spin_trylock(&q->queue_lock)) {
 			/*