block: avoid setting wbt_lat_usec to current value

There's no reason to set wbt min lat and freeze request queue
if current value is the same.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Aleksei Zakharov <zakharov.a.g@yandex.ru>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 3 insertions, 0 deletions

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 94e1b052abbc..59685918167e 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -468,6 +468,9 @@ static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
         else if (val >= 0)
                 val *= 1000ULL;
 
+        if (wbt_get_min_lat(q) == val)
+                return count;
+
         /*
          * Ensure that the queue is idled, in case the latency update
          * ends up either enabling or disabling wbt completely. We can't