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>

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 94e1b052abbce01a2ecc359ed32d621acf0a24ac..59685918167e51d80a2808861b3f2f7744dec3a7 100644 (file)
--- 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