blk-mq: add tag allocation policy

This is the blk-mq part to support tag allocation policy. The default
allocation policy isn't changed (though it's not a strict FIFO). The new
policy is round-robin for libata. But it's a try-best implementation. If
multiple tasks are competing, the tags returned will be mixed (which is
unavoidable even with !mq, as requests from different tasks can be
mixed in queue)

Cc: Jens Axboe <axboe@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index a7d4a988516f..eb8e694fda06 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1374,7 +1374,8 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
         size_t rq_size, left;
 
         tags = blk_mq_init_tags(set->queue_depth, set->reserved_tags,
-                                set->numa_node);
+                                set->numa_node,
+                                BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
         if (!tags)
                 return NULL;