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Commit ef069b97 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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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, 7fcf2b03 ("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: default avatarTejun Heo <tj@kernel.org>
Fixes: 7fcf2b03 ("blkcg: change blkg reference counting to use percpu_ref")
Cc: Dennis Zhou <dennis@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent f539da82

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: