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-rw-r--r--block/blk-cgroup.c14
1 files changed, 9 insertions, 5 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index f9797b244eb..87ea95d1f53 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -504,8 +504,9 @@ static const char *blkg_dev_name(struct blkcg_gq *blkg)
*
* This function invokes @prfill on each blkg of @blkcg if pd for the
* policy specified by @pol exists. @prfill is invoked with @sf, the
- * policy data and @data. If @show_total is %true, the sum of the return
- * values from @prfill is printed with "Total" label at the end.
+ * policy data and @data and the matching queue lock held. If @show_total
+ * is %true, the sum of the return values from @prfill is printed with
+ * "Total" label at the end.
*
* This is to be used to construct print functions for
* cftype->read_seq_string method.
@@ -520,11 +521,14 @@ void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
struct hlist_node *n;
u64 total = 0;
- spin_lock_irq(&blkcg->lock);
- hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
+ spin_lock_irq(blkg->q->queue_lock);
if (blkcg_policy_enabled(blkg->q, pol))
total += prfill(sf, blkg->pd[pol->plid], data);
- spin_unlock_irq(&blkcg->lock);
+ spin_unlock_irq(blkg->q->queue_lock);
+ }
+ rcu_read_unlock();
if (show_total)
seq_printf(sf, "Total %llu\n", (unsigned long long)total);