From ef069b97feec11c2399bbc5f6f347b35482105dc Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 13 Jun 2019 15:30:39 -0700 Subject: [PATCH] blkcg: perpcu_ref init/exit should be done from blkg_alloc/free() blkg alloc is performed as a separate step from the rest of blkg creation so that GFP_KERNEL allocations can be used when creating blkgs from configuration file writes because otherwise user actions may fail due to failures of opportunistic GFP_NOWAIT allocations. While making blkgs use percpu_ref, 7fcf2b033b84 ("blkcg: change blkg reference counting to use percpu_ref") incorrectly added unconditional opportunistic percpu_ref_init() to blkg_create() breaking this guarantee. This patch moves percpu_ref_init() to blkg_alloc() so makes it use @gfp_mask that blkg_alloc() is called with. Also, percpu_ref_exit() is moved to blkg_free() for consistency. Signed-off-by: Tejun Heo Fixes: 7fcf2b033b84 ("blkcg: change blkg reference counting to use percpu_ref") Cc: Dennis Zhou Signed-off-by: Jens Axboe --- block/blk-cgroup.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index e4715b3..04d2869 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -79,6 +79,7 @@ static void blkg_free(struct blkcg_gq *blkg) blkg_rwstat_exit(&blkg->stat_ios); blkg_rwstat_exit(&blkg->stat_bytes); + percpu_ref_exit(&blkg->refcnt); kfree(blkg); } @@ -86,8 +87,6 @@ static void __blkg_release(struct rcu_head *rcu) { struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head); - percpu_ref_exit(&blkg->refcnt); - /* release the blkcg and parent blkg refs this blkg has been holding */ css_put(&blkg->blkcg->css); if (blkg->parent) @@ -132,6 +131,9 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q, if (!blkg) return NULL; + if (percpu_ref_init(&blkg->refcnt, blkg_release, 0, gfp_mask)) + goto err_free; + if (blkg_rwstat_init(&blkg->stat_bytes, gfp_mask) || blkg_rwstat_init(&blkg->stat_ios, gfp_mask)) goto err_free; @@ -244,11 +246,6 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, blkg_get(blkg->parent); } - ret = percpu_ref_init(&blkg->refcnt, blkg_release, 0, - GFP_NOWAIT | __GFP_NOWARN); - if (ret) - goto err_cancel_ref; - /* invoke per-policy init */ for (i = 0; i < BLKCG_MAX_POLS; i++) { struct blkcg_policy *pol = blkcg_policy[i]; @@ -281,8 +278,6 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, blkg_put(blkg); return ERR_PTR(ret); -err_cancel_ref: - percpu_ref_exit(&blkg->refcnt); err_put_congested: wb_congested_put(wb_congested); err_put_css: -- 2.7.4