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

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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: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230413000649.115785-2-tj@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tejun Heo 2023-04-12 14:06:46 -10:00 committed by Jens Axboe
parent d8898ee50e
commit 83462a6c97
1 changed files with 4 additions and 9 deletions
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13
block/blk-cgroup.c
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@ -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 * 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 * 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 * part of @input following MAJ:MIN. This function returns with queue lock
* lock and queue lock held and must be paired with blkg_conf_finish(). * held and must be paired with blkg_conf_finish().
*/ */
int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
char *input, struct blkg_conf_ctx *ctx) 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 block_device *bdev;
struct gendisk *disk; struct gendisk *disk;
@ -726,7 +726,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
if (ret) if (ret)
goto fail; goto fail;
rcu_read_lock();
spin_lock_irq(&q->queue_lock); spin_lock_irq(&q->queue_lock);
if (!blkcg_policy_enabled(q, pol)) { 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. */ /* Drop locks to do new blkg allocation with GFP_KERNEL. */
spin_unlock_irq(&q->queue_lock); spin_unlock_irq(&q->queue_lock);
rcu_read_unlock();
new_blkg = blkg_alloc(pos, disk, GFP_KERNEL); new_blkg = blkg_alloc(pos, disk, GFP_KERNEL);
if (unlikely(!new_blkg)) { if (unlikely(!new_blkg)) {
@ -769,7 +767,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
goto fail_exit_queue; goto fail_exit_queue;
} }
rcu_read_lock();
spin_lock_irq(&q->queue_lock); spin_lock_irq(&q->queue_lock);
if (!blkcg_policy_enabled(q, pol)) { 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(); radix_tree_preload_end();
fail_unlock: fail_unlock:
spin_unlock_irq(&q->queue_lock); spin_unlock_irq(&q->queue_lock);
rcu_read_unlock();
fail_exit_queue: fail_exit_queue:
blk_queue_exit(q); blk_queue_exit(q);
fail: fail:
@ -832,10 +828,9 @@ EXPORT_SYMBOL_GPL(blkg_conf_prep);
* with blkg_conf_prep(). * with blkg_conf_prep().
*/ */
void blkg_conf_finish(struct blkg_conf_ctx *ctx) 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); spin_unlock_irq(&bdev_get_queue(ctx->bdev)->queue_lock);
rcu_read_unlock();
blkdev_put_no_open(ctx->bdev); blkdev_put_no_open(ctx->bdev);
} }
EXPORT_SYMBOL_GPL(blkg_conf_finish); EXPORT_SYMBOL_GPL(blkg_conf_finish);