Commit 83462a6c authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

blkcg: Drop unnecessary RCU read [un]locks from blkg_conf_prep/finish() 



Now that all RCU flavors have been combined either holding a spin lock,
disabling irq or disabling preemption implies RCU read lock, so there's no
need to use rcu_read_[un]lock() explicitly while holding queue_lock. This
shouldn't cause any behavior changes.

v2: Description updated. Leave __acquires/release on queue_lock alone.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230413000649.115785-2-tj@kernel.org


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent d8898ee5

block/blk-cgroup.c

+4 −9
Original line number Diff line number Diff line
@@ -699,12 +699,12 @@ struct block_device *blkcg_conf_open_bdev(char **inputp) 
 *

 * Parse per-blkg config update from @input and initialize @ctx with the

 * result.  @ctx->blkg points to the blkg to be updated and @ctx->body the

 * part of @input following MAJ:MIN.  This function returns with RCU read

 * lock and queue lock held and must be paired with blkg_conf_finish().

 * part of @input following MAJ:MIN.  This function returns with queue lock

 * held and must be paired with blkg_conf_finish().

 */

int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,

		   char *input, struct blkg_conf_ctx *ctx)

	__acquires(rcu) __acquires(&bdev->bd_queue->queue_lock)

	__acquires(&bdev->bd_queue->queue_lock)

{

	struct block_device *bdev;

	struct gendisk *disk;
@@ -726,7 +726,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, 
	if (ret)

		goto fail;



	rcu_read_lock();

	spin_lock_irq(&q->queue_lock);



	if (!blkcg_policy_enabled(q, pol)) {
@@ -755,7 +754,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, 


		/* Drop locks to do new blkg allocation with GFP_KERNEL. */

		spin_unlock_irq(&q->queue_lock);

		rcu_read_unlock();



		new_blkg = blkg_alloc(pos, disk, GFP_KERNEL);

		if (unlikely(!new_blkg)) {
@@ -769,7 +767,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, 
			goto fail_exit_queue;

		}



		rcu_read_lock();

		spin_lock_irq(&q->queue_lock);



		if (!blkcg_policy_enabled(q, pol)) {
@@ -805,7 +802,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, 
	radix_tree_preload_end();

fail_unlock:

	spin_unlock_irq(&q->queue_lock);

	rcu_read_unlock();

fail_exit_queue:

	blk_queue_exit(q);

fail:
@@ -832,10 +828,9 @@ EXPORT_SYMBOL_GPL(blkg_conf_prep); 
 * with blkg_conf_prep().

 */

void blkg_conf_finish(struct blkg_conf_ctx *ctx)

	__releases(&ctx->bdev->bd_queue->queue_lock) __releases(rcu)

	__releases(&ctx->bdev->bd_queue->queue_lock)

{

	spin_unlock_irq(&bdev_get_queue(ctx->bdev)->queue_lock);

	rcu_read_unlock();

	blkdev_put_no_open(ctx->bdev);

}

EXPORT_SYMBOL_GPL(blkg_conf_finish);