blk-wbt: remove the separate write cache tracking

Use the queue wide write back cache tracking insted of duplicating the
value in strut rq_wb.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20231226090747.204969-1-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-settings.c

@@ -837,8 +837,6 @@ void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
 		blk_queue_flag_set(QUEUE_FLAG_FUA, q);
 	else
 		blk_queue_flag_clear(QUEUE_FLAG_FUA, q);
-
-	wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
 }
 EXPORT_SYMBOL_GPL(blk_queue_write_cache);
 

block/blk-wbt.c

@@ -84,8 +84,6 @@ struct rq_wb {
 	u64 sync_issue;
 	void *sync_cookie;
 
-	unsigned int wc;
-
 	unsigned long last_issue;		/* last non-throttled issue */
 	unsigned long last_comp;		/* last non-throttled comp */
 	unsigned long min_lat_nsec;
@@ -207,7 +205,8 @@ static void wbt_rqw_done(struct rq_wb *rwb, struct rq_wait *rqw,
 	 */
 	if (wb_acct & WBT_DISCARD)
 		limit = rwb->wb_background;
-	else if (rwb->wc && !wb_recent_wait(rwb))
+	else if (test_bit(QUEUE_FLAG_WC, &rwb->rqos.disk->queue->queue_flags) &&
+	         !wb_recent_wait(rwb))
 		limit = 0;
 	else
 		limit = rwb->wb_normal;
@@ -699,13 +698,6 @@ static void wbt_requeue(struct rq_qos *rqos, struct request *rq)
 	}
 }
 
-void wbt_set_write_cache(struct request_queue *q, bool write_cache_on)
-{
-	struct rq_qos *rqos = wbt_rq_qos(q);
-	if (rqos)
-		RQWB(rqos)->wc = write_cache_on;
-}
-
 /*
  * Enable wbt if defaults are configured that way
  */
@@ -918,7 +910,6 @@ int wbt_init(struct gendisk *disk)
 	rwb->last_comp = rwb->last_issue = jiffies;
 	rwb->win_nsec = RWB_WINDOW_NSEC;
 	rwb->enable_state = WBT_STATE_ON_DEFAULT;
-	rwb->wc = test_bit(QUEUE_FLAG_WC, &q->queue_flags);
 	rwb->rq_depth.default_depth = RWB_DEF_DEPTH;
 	rwb->min_lat_nsec = wbt_default_latency_nsec(q);
 	rwb->rq_depth.queue_depth = blk_queue_depth(q);

block/blk-wbt.h

@@ -12,8 +12,6 @@ u64 wbt_get_min_lat(struct request_queue *q);
 void wbt_set_min_lat(struct request_queue *q, u64 val);
 bool wbt_disabled(struct request_queue *);
 
-void wbt_set_write_cache(struct request_queue *, bool);
-
 u64 wbt_default_latency_nsec(struct request_queue *);
 
 #else
@@ -24,9 +22,6 @@ static inline void wbt_disable_default(struct gendisk *disk)
 static inline void wbt_enable_default(struct gendisk *disk)
 {
 }
-static inline void wbt_set_write_cache(struct request_queue *q, bool wc)
-{
-}
 
 #endif /* CONFIG_BLK_WBT */