Commit 15974993 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

blkcg: make root blkcg allocation use %GFP_KERNEL

Currently, blkcg_activate_policy() depends on %GFP_ATOMIC allocation
from __blkg_lookup_create() for root blkcg creation.  This could make
policy fail unnecessarily.

Make blkg_alloc() take @gfp_mask, __blkg_lookup_create() take an
optional @new_blkg for preallocated blkg, and blkcg_activate_policy()
preload radix tree and preallocate blkg with %GFP_KERNEL before trying
to create the root blkg.

v2: __blkg_lookup_create() was returning %NULL on blkg alloc failure
   instead of ERR_PTR() value.  Fixed.

Signed-off-by: default avatarTejun Heo <>
Acked-by: default avatarVivek Goyal <>
Signed-off-by: default avatarJens Axboe <>
parent 13589864
......@@ -91,16 +91,18 @@ static void blkg_free(struct blkcg_gq *blkg)
* blkg_alloc - allocate a blkg
* @blkcg: block cgroup the new blkg is associated with
* @q: request_queue the new blkg is associated with
* @gfp_mask: allocation mask to use
* Allocate a new blkg assocating @blkcg and @q.
static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q)
static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
gfp_t gfp_mask)
struct blkcg_gq *blkg;
int i;
/* alloc and init base part */
blkg = kzalloc_node(sizeof(*blkg), GFP_ATOMIC, q->node);
blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
if (!blkg)
return NULL;
......@@ -117,7 +119,7 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q)
/* alloc per-policy data and attach it to blkg */
pd = kzalloc_node(pol->pd_size, GFP_ATOMIC, q->node);
pd = kzalloc_node(pol->pd_size, gfp_mask, q->node);
if (!pd) {
return NULL;
......@@ -175,8 +177,13 @@ struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q)
* If @new_blkg is %NULL, this function tries to allocate a new one as
* necessary using %GFP_ATOMIC. @new_blkg is always consumed on return.
static struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
struct request_queue *q)
struct request_queue *q,
struct blkcg_gq *new_blkg)
struct blkcg_gq *blkg;
int ret;
......@@ -188,18 +195,24 @@ static struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
blkg = __blkg_lookup(blkcg, q);
if (blkg) {
rcu_assign_pointer(blkcg->blkg_hint, blkg);
return blkg;
goto out_free;
/* blkg holds a reference to blkcg */
if (!css_tryget(&blkcg->css))
return ERR_PTR(-EINVAL);
if (!css_tryget(&blkcg->css)) {
blkg = ERR_PTR(-EINVAL);
goto out_free;
/* allocate */
ret = -ENOMEM;
blkg = blkg_alloc(blkcg, q);
if (unlikely(!blkg))
goto err_put;
if (!new_blkg) {
new_blkg = blkg_alloc(blkcg, q, GFP_ATOMIC);
if (unlikely(!new_blkg)) {
blkg = ERR_PTR(-ENOMEM);
goto out_put;
blkg = new_blkg;
/* insert */
......@@ -212,10 +225,13 @@ static struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
if (!ret)
return blkg;
blkg = ERR_PTR(ret);
return ERR_PTR(ret);
return blkg;
struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
......@@ -227,7 +243,7 @@ struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
if (unlikely(blk_queue_bypass(q)))
return ERR_PTR(blk_queue_dead(q) ? -EINVAL : -EBUSY);
return __blkg_lookup_create(blkcg, q);
return __blkg_lookup_create(blkcg, q, NULL);
......@@ -726,19 +742,30 @@ int blkcg_activate_policy(struct request_queue *q,
struct blkcg_gq *blkg;
struct blkg_policy_data *pd, *n;
int cnt = 0, ret;
bool preloaded;
if (blkcg_policy_enabled(q, pol))
return 0;
/* preallocations for root blkg */
blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
if (!blkg)
return -ENOMEM;
preloaded = !radix_tree_preload(GFP_KERNEL);
/* make sure the root blkg exists and count the existing blkgs */
blkg = __blkg_lookup_create(&blkcg_root, q);
blkg = __blkg_lookup_create(&blkcg_root, q, blkg);
if (preloaded)
if (IS_ERR(blkg)) {
ret = PTR_ERR(blkg);
goto out_unlock;
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