blk-mq: bitmap tag: select random tag betweet 0 and (depth - 1)
The selected tag should be selected at random between 0 and
(depth - 1) with probability 1/depth, instead between 0 and
(depth - 2) with probability 1/(depth - 1).
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 5a83d8e..f196e60 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -449,10 +449,7 @@
{
unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
- if (depth > 1)
- *tag = prandom_u32() % (depth - 1);
- else
- *tag = 0;
+ *tag = prandom_u32() % depth;
}
ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page)
