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-rw-r--r--block/blk-mq-tag.c14
-rw-r--r--block/blk-mq.c4
2 files changed, 17 insertions, 1 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index c0c4e63583ae..8c5cc115b3f8 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -320,6 +320,18 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
struct blk_mq_hw_ctx *hctx;
int i;
+ /*
+ * __blk_mq_update_nr_hw_queues will update the nr_hw_queues and
+ * queue_hw_ctx after freeze the queue. So we could use q_usage_counter
+ * to avoid race with it. __blk_mq_update_nr_hw_queues will users
+ * synchronize_rcu to ensure all of the users go out of the critical
+ * section below and see zeroed q_usage_counter.
+ */
+ rcu_read_lock();
+ if (percpu_ref_is_zero(&q->q_usage_counter)) {
+ rcu_read_unlock();
+ return;
+ }
queue_for_each_hw_ctx(q, hctx, i) {
struct blk_mq_tags *tags = hctx->tags;
@@ -335,7 +347,7 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
}
-
+ rcu_read_unlock();
}
static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9c8c8c71a13f..81cb84b17b73 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2977,6 +2977,10 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
list_for_each_entry(q, &set->tag_list, tag_set_list)
blk_mq_freeze_queue(q);
/*
+ * Sync with blk_mq_queue_tag_busy_iter.
+ */
+ synchronize_rcu();
+ /*
* Switch IO scheduler to 'none', cleaning up the data associated
* with the previous scheduler. We will switch back once we are done
* updating the new sw to hw queue mappings.