blkcg: perpcu_ref init/exit should be done from blkg_alloc/free() (ef069b97) · Commits · 戴 / test

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, ("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 <tj@kernel.org> Fixes: ("blkcg: change blkg reference counting to use percpu_ref") Cc: Dennis Zhou <dennis@kernel.org> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/blk-cgroup.c

+4 −9

Original line number	Diff line number	Diff line
		@@ -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:

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