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Commit db613670 authored by Tejun Heo's avatar Tejun Heo
Browse files

blkcg: invoke blkcg_policy->pd_init() after parent is linked 



Currently, when creating a new blkcg_gq, each policy's pd_init_fn() is
invoked in blkg_alloc() before the parent is linked.  This makes it
difficult for policies to perform initializations which are dependent
on the parent.

This patch moves pd_init_fn() invocations to blkg_create() after the
parent blkg is linked where the new blkg is fully initialized.  As
this means that blkg_free() can't assume that pd's are initialized,
pd_exit_fn() invocations are moved to __blkg_release().  This
guarantees that pd_exit_fn() is also invoked with fully initialized
blkgs with valid parent pointers.

This will help implementing hierarchy support in blk-throttle.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarVivek Goyal <vgoyal@redhat.com>
parent aa539cb3

block/blk-cgroup.c

+22 −17
Original line number Diff line number Diff line
@@ -51,18 +51,8 @@ static void blkg_free(struct blkcg_gq *blkg) 
	if (!blkg)

		return;



	for (i = 0; i < BLKCG_MAX_POLS; i++) {

		struct blkcg_policy *pol = blkcg_policy[i];

		struct blkg_policy_data *pd = blkg->pd[i];



		if (!pd)

			continue;



		if (pol && pol->pd_exit_fn)

			pol->pd_exit_fn(blkg);



		kfree(pd);

	}

	for (i = 0; i < BLKCG_MAX_POLS; i++)

		kfree(blkg->pd[i]);



	blk_exit_rl(&blkg->rl);

	kfree(blkg);
@@ -114,10 +104,6 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q, 
		blkg->pd[i] = pd;

		pd->blkg = blkg;

		pd->plid = i;



		/* invoke per-policy init */

		if (pol->pd_init_fn)

			pol->pd_init_fn(blkg);

	}



	return blkg;
@@ -214,7 +200,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, 
	}

	blkg = new_blkg;



	/* link parent and insert */

	/* link parent */

	if (blkcg_parent(blkcg)) {

		blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);

		if (WARN_ON_ONCE(!blkg->parent)) {
@@ -224,6 +210,15 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, 
		blkg_get(blkg->parent);

	}



	/* invoke per-policy init */

	for (i = 0; i < BLKCG_MAX_POLS; i++) {

		struct blkcg_policy *pol = blkcg_policy[i];



		if (blkg->pd[i] && pol->pd_init_fn)

			pol->pd_init_fn(blkg);

	}



	/* insert */

	spin_lock(&blkcg->lock);

	ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);

	if (likely(!ret)) {
@@ -381,6 +376,16 @@ static void blkg_rcu_free(struct rcu_head *rcu_head) 


void __blkg_release(struct blkcg_gq *blkg)

{

	int i;



	/* tell policies that this one is being freed */

	for (i = 0; i < BLKCG_MAX_POLS; i++) {

		struct blkcg_policy *pol = blkcg_policy[i];



		if (blkg->pd[i] && pol->pd_exit_fn)

			pol->pd_exit_fn(blkg);

	}



	/* release the blkcg and parent blkg refs this blkg has been holding */

	css_put(&blkg->blkcg->css);

	if (blkg->parent)