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path: root/block/blk-cgroup.c
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Diffstat (limited to 'block/blk-cgroup.c')
-rw-r--r--block/blk-cgroup.c228
1 files changed, 154 insertions, 74 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index d6e4555c982f..d6d59ad105b4 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -54,6 +54,17 @@ struct blkio_cgroup *bio_blkio_cgroup(struct bio *bio)
}
EXPORT_SYMBOL_GPL(bio_blkio_cgroup);
+static bool blkcg_policy_enabled(struct request_queue *q,
+ const struct blkio_policy_type *pol)
+{
+ return pol && test_bit(pol->plid, q->blkcg_pols);
+}
+
+static size_t blkg_pd_size(const struct blkio_policy_type *pol)
+{
+ return sizeof(struct blkg_policy_data) + pol->pdata_size;
+}
+
/**
* blkg_free - free a blkg
* @blkg: blkg to free
@@ -111,12 +122,11 @@ static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
struct blkio_policy_type *pol = blkio_policy[i];
struct blkg_policy_data *pd;
- if (!pol)
+ if (!blkcg_policy_enabled(q, pol))
continue;
/* alloc per-policy data and attach it to blkg */
- pd = kzalloc_node(sizeof(*pd) + pol->pdata_size, GFP_ATOMIC,
- q->node);
+ pd = kzalloc_node(blkg_pd_size(pol), GFP_ATOMIC, q->node);
if (!pd) {
blkg_free(blkg);
return NULL;
@@ -130,7 +140,7 @@ static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkio_policy_type *pol = blkio_policy[i];
- if (pol)
+ if (blkcg_policy_enabled(blkg->q, pol))
pol->ops.blkio_init_group_fn(blkg);
}
@@ -236,36 +246,6 @@ static void blkg_destroy(struct blkio_group *blkg)
blkg_put(blkg);
}
-/*
- * XXX: This updates blkg policy data in-place for root blkg, which is
- * necessary across elevator switch and policy registration as root blkgs
- * aren't shot down. This broken and racy implementation is temporary.
- * Eventually, blkg shoot down will be replaced by proper in-place update.
- */
-void update_root_blkg_pd(struct request_queue *q,
- const struct blkio_policy_type *pol)
-{
- struct blkio_group *blkg = blkg_lookup(&blkio_root_cgroup, q);
- struct blkg_policy_data *pd;
-
- if (!blkg)
- return;
-
- kfree(blkg->pd[pol->plid]);
- blkg->pd[pol->plid] = NULL;
-
- if (!pol)
- return;
-
- pd = kzalloc(sizeof(*pd) + pol->pdata_size, GFP_KERNEL);
- WARN_ON_ONCE(!pd);
-
- blkg->pd[pol->plid] = pd;
- pd->blkg = blkg;
- pol->ops.blkio_init_group_fn(blkg);
-}
-EXPORT_SYMBOL_GPL(update_root_blkg_pd);
-
/**
* blkg_destroy_all - destroy all blkgs associated with a request_queue
* @q: request_queue of interest
@@ -339,7 +319,8 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkio_policy_type *pol = blkio_policy[i];
- if (pol && pol->ops.blkio_reset_group_stats_fn)
+ if (blkcg_policy_enabled(blkg->q, pol) &&
+ pol->ops.blkio_reset_group_stats_fn)
pol->ops.blkio_reset_group_stats_fn(blkg);
}
}
@@ -385,7 +366,7 @@ void blkcg_print_blkgs(struct seq_file *sf, struct blkio_cgroup *blkcg,
spin_lock_irq(&blkcg->lock);
hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
- if (blkg->pd[pol->plid])
+ if (blkcg_policy_enabled(blkg->q, pol))
total += prfill(sf, blkg->pd[pol->plid]->pdata, data);
spin_unlock_irq(&blkcg->lock);
@@ -510,7 +491,10 @@ int blkg_conf_prep(struct blkio_cgroup *blkcg,
rcu_read_lock();
spin_lock_irq(disk->queue->queue_lock);
- blkg = blkg_lookup_create(blkcg, disk->queue, false);
+ if (blkcg_policy_enabled(disk->queue, pol))
+ blkg = blkg_lookup_create(blkcg, disk->queue, false);
+ else
+ blkg = ERR_PTR(-EINVAL);
if (IS_ERR(blkg)) {
ret = PTR_ERR(blkg);
@@ -712,30 +696,6 @@ static int blkiocg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
return ret;
}
-static void blkcg_bypass_start(void)
- __acquires(&all_q_mutex)
-{
- struct request_queue *q;
-
- mutex_lock(&all_q_mutex);
-
- list_for_each_entry(q, &all_q_list, all_q_node) {
- blk_queue_bypass_start(q);
- blkg_destroy_all(q, false);
- }
-}
-
-static void blkcg_bypass_end(void)
- __releases(&all_q_mutex)
-{
- struct request_queue *q;
-
- list_for_each_entry(q, &all_q_list, all_q_node)
- blk_queue_bypass_end(q);
-
- mutex_unlock(&all_q_mutex);
-}
-
struct cgroup_subsys blkio_subsys = {
.name = "blkio",
.create = blkiocg_create,
@@ -749,6 +709,139 @@ struct cgroup_subsys blkio_subsys = {
EXPORT_SYMBOL_GPL(blkio_subsys);
/**
+ * blkcg_activate_policy - activate a blkcg policy on a request_queue
+ * @q: request_queue of interest
+ * @pol: blkcg policy to activate
+ *
+ * Activate @pol on @q. Requires %GFP_KERNEL context. @q goes through
+ * bypass mode to populate its blkgs with policy_data for @pol.
+ *
+ * Activation happens with @q bypassed, so nobody would be accessing blkgs
+ * from IO path. Update of each blkg is protected by both queue and blkcg
+ * locks so that holding either lock and testing blkcg_policy_enabled() is
+ * always enough for dereferencing policy data.
+ *
+ * The caller is responsible for synchronizing [de]activations and policy
+ * [un]registerations. Returns 0 on success, -errno on failure.
+ */
+int blkcg_activate_policy(struct request_queue *q,
+ const struct blkio_policy_type *pol)
+{
+ LIST_HEAD(pds);
+ struct blkio_group *blkg;
+ struct blkg_policy_data *pd, *n;
+ int cnt = 0, ret;
+
+ if (blkcg_policy_enabled(q, pol))
+ return 0;
+
+ blk_queue_bypass_start(q);
+
+ /* make sure the root blkg exists and count the existing blkgs */
+ spin_lock_irq(q->queue_lock);
+
+ rcu_read_lock();
+ blkg = blkg_lookup_create(&blkio_root_cgroup, q, true);
+ rcu_read_unlock();
+
+ if (IS_ERR(blkg)) {
+ ret = PTR_ERR(blkg);
+ goto out_unlock;
+ }
+ q->root_blkg = blkg;
+
+ list_for_each_entry(blkg, &q->blkg_list, q_node)
+ cnt++;
+
+ spin_unlock_irq(q->queue_lock);
+
+ /* allocate policy_data for all existing blkgs */
+ while (cnt--) {
+ pd = kzalloc_node(blkg_pd_size(pol), GFP_KERNEL, q->node);
+ if (!pd) {
+ ret = -ENOMEM;
+ goto out_free;
+ }
+ list_add_tail(&pd->alloc_node, &pds);
+ }
+
+ /*
+ * Install the allocated pds. With @q bypassing, no new blkg
+ * should have been created while the queue lock was dropped.
+ */
+ spin_lock_irq(q->queue_lock);
+
+ list_for_each_entry(blkg, &q->blkg_list, q_node) {
+ if (WARN_ON(list_empty(&pds))) {
+ /* umm... this shouldn't happen, just abort */
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+ pd = list_first_entry(&pds, struct blkg_policy_data, alloc_node);
+ list_del_init(&pd->alloc_node);
+
+ /* grab blkcg lock too while installing @pd on @blkg */
+ spin_lock(&blkg->blkcg->lock);
+
+ blkg->pd[pol->plid] = pd;
+ pd->blkg = blkg;
+ pol->ops.blkio_init_group_fn(blkg);
+
+ spin_unlock(&blkg->blkcg->lock);
+ }
+
+ __set_bit(pol->plid, q->blkcg_pols);
+ ret = 0;
+out_unlock:
+ spin_unlock_irq(q->queue_lock);
+out_free:
+ blk_queue_bypass_end(q);
+ list_for_each_entry_safe(pd, n, &pds, alloc_node)
+ kfree(pd);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(blkcg_activate_policy);
+
+/**
+ * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
+ * @q: request_queue of interest
+ * @pol: blkcg policy to deactivate
+ *
+ * Deactivate @pol on @q. Follows the same synchronization rules as
+ * blkcg_activate_policy().
+ */
+void blkcg_deactivate_policy(struct request_queue *q,
+ const struct blkio_policy_type *pol)
+{
+ struct blkio_group *blkg;
+
+ if (!blkcg_policy_enabled(q, pol))
+ return;
+
+ blk_queue_bypass_start(q);
+ spin_lock_irq(q->queue_lock);
+
+ __clear_bit(pol->plid, q->blkcg_pols);
+
+ list_for_each_entry(blkg, &q->blkg_list, q_node) {
+ /* grab blkcg lock too while removing @pd from @blkg */
+ spin_lock(&blkg->blkcg->lock);
+
+ if (pol->ops.blkio_exit_group_fn)
+ pol->ops.blkio_exit_group_fn(blkg);
+
+ kfree(blkg->pd[pol->plid]);
+ blkg->pd[pol->plid] = NULL;
+
+ spin_unlock(&blkg->blkcg->lock);
+ }
+
+ spin_unlock_irq(q->queue_lock);
+ blk_queue_bypass_end(q);
+}
+EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
+
+/**
* blkio_policy_register - register a blkcg policy
* @blkiop: blkcg policy to register
*
@@ -758,7 +851,6 @@ EXPORT_SYMBOL_GPL(blkio_subsys);
*/
int blkio_policy_register(struct blkio_policy_type *blkiop)
{
- struct request_queue *q;
int i, ret;
mutex_lock(&blkcg_pol_mutex);
@@ -775,11 +867,6 @@ int blkio_policy_register(struct blkio_policy_type *blkiop)
blkiop->plid = i;
blkio_policy[i] = blkiop;
- blkcg_bypass_start();
- list_for_each_entry(q, &all_q_list, all_q_node)
- update_root_blkg_pd(q, blkiop);
- blkcg_bypass_end();
-
/* everything is in place, add intf files for the new policy */
if (blkiop->cftypes)
WARN_ON(cgroup_add_cftypes(&blkio_subsys, blkiop->cftypes));
@@ -798,8 +885,6 @@ EXPORT_SYMBOL_GPL(blkio_policy_register);
*/
void blkio_policy_unregister(struct blkio_policy_type *blkiop)
{
- struct request_queue *q;
-
mutex_lock(&blkcg_pol_mutex);
if (WARN_ON(blkio_policy[blkiop->plid] != blkiop))
@@ -811,11 +896,6 @@ void blkio_policy_unregister(struct blkio_policy_type *blkiop)
/* unregister and update blkgs */
blkio_policy[blkiop->plid] = NULL;
-
- blkcg_bypass_start();
- list_for_each_entry(q, &all_q_list, all_q_node)
- update_root_blkg_pd(q, blkiop);
- blkcg_bypass_end();
out_unlock:
mutex_unlock(&blkcg_pol_mutex);
}