From: Yu Kuai <yukuai3@xxxxxxxxxx>
ioc_lookup_icq() is used by bfq to lookup bfqq from IO path, the helper
have to be protected by queue_lock, which is too heavy. Hence add a new
helper that is lookless, this is safe because both request_queue and ioc
can be pinged by IO that is still issuing.
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
block/blk-ioc.c | 34 ++++++++++++++++++++++++++++++++++
block/blk.h | 1 +
2 files changed, 35 insertions(+)
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index ce82770c72ab..4945b48dfdb6 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -343,6 +343,40 @@ struct io_cq *ioc_lookup_icq(struct request_queue *q)
}
EXPORT_SYMBOL(ioc_lookup_icq);
+/**
+ * ioc_lookup_icq_rcu - lookup io_cq from ioc in io path
+ * @q: the associated request_queue
+ *
+ * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called from
+ * io issue path, either return NULL if current issue io to @q for the first
+ * time, or return a valid icq.
+ */
+struct io_cq *ioc_lookup_icq_rcu(struct request_queue *q)
+{
+ struct io_context *ioc = current->io_context;
+ struct io_cq *icq;
+
+ WARN_ON_ONCE(percpu_ref_is_zero(&q->q_usage_counter));
+
+ if (!ioc)
+ return NULL;
+
+ icq = rcu_dereference(ioc->icq_hint);
+ if (icq && icq->q == q)
+ return icq;
+
+ icq = radix_tree_lookup(&ioc->icq_tree, q->id);
+ if (!icq)
+ return NULL;
+
+ if (WARN_ON_ONCE(icq->q != q))
+ return NULL;
+
+ rcu_assign_pointer(ioc->icq_hint, icq);
+ return icq;
+}
+EXPORT_SYMBOL(ioc_lookup_icq_rcu);
+
/**
* ioc_create_icq - create and link io_cq
* @q: request_queue of interest
diff --git a/block/blk.h b/block/blk.h
index 468aa83c5a22..ef31b3ec1c69 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -461,6 +461,7 @@ static inline void req_set_nomerge(struct request_queue *q, struct request *req)
*/
struct io_cq *ioc_find_get_icq(struct request_queue *q);
struct io_cq *ioc_lookup_icq(struct request_queue *q);
+struct io_cq *ioc_lookup_icq_rcu(struct request_queue *q);
#ifdef CONFIG_BLK_ICQ
void ioc_clear_queue(struct request_queue *q);
#else
--
2.39.2
