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Diffstat (limited to 'block/blk-cgroup.c')
-rw-r--r--block/blk-cgroup.c41
1 files changed, 32 insertions, 9 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index c8b28ec5dde9..fc49be622e05 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -34,6 +34,8 @@
#include "blk-ioprio.h"
#include "blk-throttle.h"
+static void __blkcg_rstat_flush(struct blkcg *blkcg, int cpu);
+
/*
* blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
* blkcg_pol_register_mutex nests outside of it and synchronizes entire
@@ -56,6 +58,8 @@ static LIST_HEAD(all_blkcgs); /* protected by blkcg_pol_mutex */
bool blkcg_debug_stats = false;
+static DEFINE_RAW_SPINLOCK(blkg_stat_lock);
+
#define BLKG_DESTROY_BATCH_SIZE 64
/*
@@ -163,10 +167,20 @@ static void blkg_free(struct blkcg_gq *blkg)
static void __blkg_release(struct rcu_head *rcu)
{
struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
+ struct blkcg *blkcg = blkg->blkcg;
+ int cpu;
#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
WARN_ON(!bio_list_empty(&blkg->async_bios));
#endif
+ /*
+ * Flush all the non-empty percpu lockless lists before releasing
+ * us, given these stat belongs to us.
+ *
+ * blkg_stat_lock is for serializing blkg stat update
+ */
+ for_each_possible_cpu(cpu)
+ __blkcg_rstat_flush(blkcg, cpu);
/* release the blkcg and parent blkg refs this blkg has been holding */
css_put(&blkg->blkcg->css);
@@ -965,16 +979,12 @@ static void blkcg_iostat_update(struct blkcg_gq *blkg, struct blkg_iostat *cur,
u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
}
-static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
+static void __blkcg_rstat_flush(struct blkcg *blkcg, int cpu)
{
- struct blkcg *blkcg = css_to_blkcg(css);
struct llist_head *lhead = per_cpu_ptr(blkcg->lhead, cpu);
struct llist_node *lnode;
struct blkg_iostat_set *bisc, *next_bisc;
-
- /* Root-level stats are sourced from system-wide IO stats */
- if (!cgroup_parent(css->cgroup))
- return;
+ unsigned long flags;
rcu_read_lock();
@@ -983,6 +993,14 @@ static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
goto out;
/*
+ * For covering concurrent parent blkg update from blkg_release().
+ *
+ * When flushing from cgroup, cgroup_rstat_lock is always held, so
+ * this lock won't cause contention most of time.
+ */
+ raw_spin_lock_irqsave(&blkg_stat_lock, flags);
+
+ /*
* Iterate only the iostat_cpu's queued in the lockless list.
*/
llist_for_each_entry_safe(bisc, next_bisc, lnode, lnode) {
@@ -1005,13 +1023,19 @@ static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
if (parent && parent->parent)
blkcg_iostat_update(parent, &blkg->iostat.cur,
&blkg->iostat.last);
- percpu_ref_put(&blkg->refcnt);
}
-
+ raw_spin_unlock_irqrestore(&blkg_stat_lock, flags);
out:
rcu_read_unlock();
}
+static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
+{
+ /* Root-level stats are sourced from system-wide IO stats */
+ if (cgroup_parent(css->cgroup))
+ __blkcg_rstat_flush(css_to_blkcg(css), cpu);
+}
+
/*
* We source root cgroup stats from the system-wide stats to avoid
* tracking the same information twice and incurring overhead when no
@@ -2092,7 +2116,6 @@ void blk_cgroup_bio_start(struct bio *bio)
llist_add(&bis->lnode, lhead);
WRITE_ONCE(bis->lqueued, true);
- percpu_ref_get(&bis->blkg->refcnt);
}
u64_stats_update_end_irqrestore(&bis->sync, flags);