block: Make writeback throttling defaults consistent for SQ devices
When CFQ is used as an elevator, it disables writeback throttling
because they don't play well together. Later when a different elevator
is chosen for the device, writeback throttling doesn't get enabled
again as it should. Make sure CFQ enables writeback throttling (if it
should be enabled by default) when we switch from it to another IO
scheduler.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index b3b7914..26e1bb6 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -665,6 +665,25 @@ void wbt_disable_default(struct request_queue *q)
}
EXPORT_SYMBOL_GPL(wbt_disable_default);
+/*
+ * Enable wbt if defaults are configured that way
+ */
+void wbt_enable_default(struct request_queue *q)
+{
+ /* Throttling already enabled? */
+ if (q->rq_wb)
+ return;
+
+ /* Queue not registered? Maybe shutting down... */
+ if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
+ return;
+
+ if ((q->mq_ops && IS_ENABLED(CONFIG_BLK_WBT_MQ)) ||
+ (q->request_fn && IS_ENABLED(CONFIG_BLK_WBT_SQ)))
+ wbt_init(q);
+}
+EXPORT_SYMBOL_GPL(wbt_enable_default);
+
u64 wbt_default_latency_nsec(struct request_queue *q)
{
/*