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

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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: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
This commit is contained in:
Tejun Heo 2013-05-14 13:52:31 -07:00
parent aa539cb38f
commit db61367038
1 changed files with 22 additions and 17 deletions
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39
block/blk-cgroup.c
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@ -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)