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, 15 insertions, 7 deletions

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 1855c67..f0ca569 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -42,12 +42,12 @@ queue_var_store(unsigned long *var, const char *page, size_t count)
 	return count;
 }
 
-static ssize_t queue_var_store64(u64 *var, const char *page)
+static ssize_t queue_var_store64(s64 *var, const char *page)
 {
 	int err;
-	u64 v;
+	s64 v;
 
-	err = kstrtou64(page, 10, &v);
+	err = kstrtos64(page, 10, &v);
 	if (err < 0)
 		return err;
 
@@ -421,18 +421,26 @@ static ssize_t queue_wb_lat_show(struct request_queue *q, char *page)
 static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
 				  size_t count)
 {
+	struct rq_wb *rwb;
 	ssize_t ret;
-	u64 val;
+	s64 val;
 
-	if (!q->rq_wb)
+	rwb = q->rq_wb;
+	if (!rwb)
 		return -EINVAL;
 
 	ret = queue_var_store64(&val, page);
 	if (ret < 0)
 		return ret;
 
-	q->rq_wb->min_lat_nsec = val * 1000ULL;
-	wbt_update_limits(q->rq_wb);
+	if (val == -1)
+		rwb->min_lat_nsec = wbt_default_latency_nsec(q);
+	else if (val >= 0)
+		rwb->min_lat_nsec = val * 1000ULL;
+	else
+		return -EINVAL;
+
+	wbt_update_limits(rwb);
 	return count;
 }