blk-wbt: allow reset of default latency through sysfs

Allow a write of '-1' to reset the default latency target for
a given device. This removes knowledge of the different default
settings for rotational vs non-rotational from user space.

Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/block/blk-wbt.h b/block/blk-wbt.h
index 44dc2173dc1f..9dfc88ad7f30 100644
--- a/block/blk-wbt.h
+++ b/block/blk-wbt.h
@@ -110,6 +110,8 @@ void wbt_disable(struct rq_wb *);
 void wbt_set_queue_depth(struct rq_wb *, unsigned int);
 void wbt_set_write_cache(struct rq_wb *, bool);
 
+u64 wbt_default_latency_nsec(struct request_queue *);
+
 #else
 
 static inline void __wbt_done(struct rq_wb *rwb, enum wbt_flags flags)
@@ -148,6 +150,10 @@ static inline void wbt_set_queue_depth(struct rq_wb *rwb, unsigned int depth)
 static inline void wbt_set_write_cache(struct rq_wb *rwb, bool wc)
 {
 }
+static inline u64 wbt_default_latency_nsec(struct request_queue *q)
+{
+        return 0;
+}
 
 #endif /* CONFIG_BLK_WBT */