Commit 5765033c authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
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blk-cgroup: don't update the blkg lookup hint in blkg_conf_prep 



blkg_conf_prep just creates a new blkg structure, there is no real
need to update the lookup hint which should only be done on a
successful lookup in the I/O path.

Suggested-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220927065425.257876-1-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 8237c01f

block/blk-cgroup.c

+4 −13
Original line number Original line Diff line number Diff line
@@ -263,14 +263,6 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk, 
	return NULL;

	return NULL;

}

}





static void blkg_update_hint(struct blkcg *blkcg, struct blkcg_gq *blkg)

{

	lockdep_assert_held(&blkg->q->queue_lock);



	if (blkcg != &blkcg_root && blkg != rcu_dereference(blkcg->blkg_hint))

		rcu_assign_pointer(blkcg->blkg_hint, blkg);

}



/*

/*

 * If @new_blkg is %NULL, this function tries to allocate a new one as

 * If @new_blkg is %NULL, this function tries to allocate a new one as

 * necessary using %GFP_NOWAIT.  @new_blkg is always consumed on return.

 * necessary using %GFP_NOWAIT.  @new_blkg is always consumed on return.
@@ -383,7 +375,9 @@ static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, 
	spin_lock_irqsave(&q->queue_lock, flags);

	spin_lock_irqsave(&q->queue_lock, flags);

	blkg = blkg_lookup(blkcg, q);

	blkg = blkg_lookup(blkcg, q);

	if (blkg) {

	if (blkg) {

		blkg_update_hint(blkcg, blkg);

		if (blkcg != &blkcg_root &&

		    blkg != rcu_dereference(blkcg->blkg_hint))

			rcu_assign_pointer(blkcg->blkg_hint, blkg);

		goto found;

		goto found;

	}

	}
@@ -680,10 +674,8 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, 
	}

	}





	blkg = blkg_lookup(blkcg, q);

	blkg = blkg_lookup(blkcg, q);

	if (blkg) {

	if (blkg)

		blkg_update_hint(blkcg, blkg);

		goto success;

		goto success;

	}





	/*

	/*

	 * Create blkgs walking down from blkcg_root to @blkcg, so that all

	 * Create blkgs walking down from blkcg_root to @blkcg, so that all
@@ -727,7 +719,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, 




		blkg = blkg_lookup(pos, q);

		blkg = blkg_lookup(pos, q);

		if (blkg) {

		if (blkg) {

			blkg_update_hint(pos, blkg);

			blkg_free(new_blkg);

			blkg_free(new_blkg);

		} else {

		} else {

			blkg = blkg_create(pos, disk, new_blkg);

			blkg = blkg_create(pos, disk, new_blkg);