block: use blk_free_flush_queue() to free hctx->fq in blk_mq_init_hctx

[ Upstream commit b9a1ff504b9492ad6beb7d5606e0e3365d4d8499 ]

kfree() can leak the hctx->fq->flush_rq field.
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NShenghui Wang <shhuiw@foxmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NSasha Levin <sashal@kernel.org>

block/blk-mq.c

@@ -2236,7 +2236,7 @@ static int blk_mq_init_hctx(struct request_queue *q,
 	return 0;
 
  free_fq:
-	kfree(hctx->fq);
+	blk_free_flush_queue(hctx->fq);
  exit_hctx:
 	if (set->ops->exit_hctx)
 		set->ops->exit_hctx(hctx, hctx_idx);