From 5765033cf77c54897848df683420bb62b6cc3d05 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 27 Sep 2022 08:54:25 +0200 Subject: [PATCH] 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 Signed-off-by: Christoph Hellwig Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20220927065425.257876-1-hch@lst.de Signed-off-by: Jens Axboe --- block/blk-cgroup.c | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 94af5f3f3620..6a5c849ee061 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -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);