block: Simplify blk_mq_dispatch_rq_list() and its callers

The 'nr_budgets' argument of blk_mq_dispatch_rq_list() is either the
number of elements in the 'list' argument or zero. Instead of passing
the number of list elements to blk_mq_dispatch_rq_list(), pass a boolean
argument that indicates whether or not blk_mq_dispatch_rq_list() should
request the block driver for a budget for each request in 'list'.

Remove the code for counting list elements from blk_mq_dispatch_rq_list()
callers where possible. Remove the code that decrements nr_budgets from
blk_mq_dispatch_rq_list() because it is superfluous. Each request that
is processed by blk_mq_dispatch_rq_list() is in one of these two states
if 'get_budget' is false:
* Either the request is on 'list' and the budget for the request has to
  be released from the error path.
* Or the request is not on 'list' and q->mq_ops->queue_rq() has already
  released the budget (ret != BLK_STS_OK) or q->mq_ops->queue_rq() will
  release the budget asynchronously (ret == BLK_STS_OK).

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: John Garry <john.g.garry@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20250415205134.3650042-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 1 insertions, 1 deletions

diff --git a/block/blk-mq.h b/block/blk-mq.h
index 3011a78cf16a..d15ff1e130c8 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -48,7 +48,7 @@ void blk_mq_exit_queue(struct request_queue *q);
 int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr);
 void blk_mq_wake_waiters(struct request_queue *q);
 bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *,
-			     unsigned int);
+			     bool);
 void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list);
 struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
 					struct blk_mq_ctx *start);