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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: Tejun Heo <tj@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220927065425.257876-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2022-09-27 08:54:25 +02:00 committed by Jens Axboe
parent 8237c01f16
commit 5765033cf7
1 changed files with 4 additions and 13 deletions
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17
block/blk-cgroup.c
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@ -263,14 +263,6 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk,
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
* 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);
blkg = blkg_lookup(blkcg, q);
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;
}
@ -680,10 +674,8 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
}
blkg = blkg_lookup(blkcg, q);
if (blkg) {
blkg_update_hint(blkcg, blkg);
if (blkg)
goto success;
}
/*
* 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);
if (blkg) {
blkg_update_hint(pos, blkg);
blkg_free(new_blkg);
} else {
blkg = blkg_create(pos, disk, new_blkg);