blk-cgroup: remove unused blk_queue_for_each_rl stub

From: Tao Cui <[email protected]>

blk_queue_for_each_rl() was added by commit a051661ca6d1 ("blkcg:
implement per-blkg request allocation") to iterate over the root request list and per-blkg request lists for the legacy (non-blk-mq) request allocation path. The request_list code, including q->root_rl from struct request_queue, was later removed in 2018 by commit db6d99523560 ("block: remove request_list code").

The macro definition left behind in the !CONFIG_BLK_CGROUP fallback branch of the private block/blk-cgroup.h header now references the removed q->root_rl field, and has no callers in-tree (it would fail to compile if expanded, so it cannot have any out-of-tree users either).

Remove the dead stub.

---
Changes in v2:
- Rebase onto current linux-next head (no code change).
- Add the Reviewed-by tags collected on v1 (Yu Kuai, Tang Yizhou).
- Link to v1: https://lore.kernel.org/r/[email protected]

---
 block/blk-cgroup.h | 3 ---
 1 file changed, 3 deletions(-)

index e67c69839129..ceca6647a5e5 100644
@@ -517,9 +517,6 @@ static inline void blkg_put(struct blkcg_gq *blkg) { }
 static inline void blk_cgroup_bio_start(struct bio *bio) { }
 static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) { return true; }
 
-#define blk_queue_for_each_rl(rl, q)	\
-	for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)
-
 #endif	/* CONFIG_BLK_CGROUP */
 
 #endif /* _BLK_CGROUP_PRIVATE_H */

2.43.0