block: don't handle bio based drivers in blk_revalidate_disk_zones

bio based drivers only need to update q->nr_zones.  Do that manually
instead of overloading blk_revalidate_disk_zones to keep that function
simpler for the next round of changes that will rely even more on the
request based functionality.
Reviewed-by: Javier González <javier@javigon.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-zoned.c

@@ -419,8 +419,9 @@ static int blk_revalidate_zone_cb(struct blk_zone *zone, unsigned int idx,
  *
  * Helper function for low-level device drivers to (re) allocate and initialize
  * a disk request queue zone bitmaps. This functions should normally be called
- * within the disk ->revalidate method. For BIO based queues, no zone bitmap
- * is allocated.
+ * within the disk ->revalidate method for blk-mq based drivers.  For BIO based
+ * drivers only q->nr_zones needs to be updated so that the sysfs exposed value
+ * is correct.
  */
 int blk_revalidate_disk_zones(struct gendisk *disk)
 {
@@ -433,15 +434,8 @@ int blk_revalidate_disk_zones(struct gendisk *disk)
 
 	if (WARN_ON_ONCE(!blk_queue_is_zoned(q)))
 		return -EIO;
-
-	/*
-	 * BIO based queues do not use a scheduler so only q->nr_zones
-	 * needs to be updated so that the sysfs exposed value is correct.
-	 */
-	if (!queue_is_mq(q)) {
-		q->nr_zones = args.nr_zones;
-		return 0;
-	}
+	if (WARN_ON_ONCE(!queue_is_mq(q)))
+		return -EIO;
 
 	/*
 	 * Ensure that all memory allocations in this context are done as

drivers/block/null_blk_main.c

@@ -1576,11 +1576,17 @@ static int null_gendisk_register(struct nullb *nullb)
 	disk->queue		= nullb->q;
 	strncpy(disk->disk_name, nullb->disk_name, DISK_NAME_LEN);
 
+#ifdef CONFIG_BLK_DEV_ZONED
 	if (nullb->dev->zoned) {
-		ret = blk_revalidate_disk_zones(disk);
-		if (ret)
-			return ret;
+		if (queue_is_mq(nullb->q)) {
+			ret = blk_revalidate_disk_zones(disk);
+			if (ret)
+				return ret;
+		} else {
+			nullb->q->nr_zones = blkdev_nr_zones(disk);
+		}
 	}
+#endif
 
 	add_disk(disk);
 	return 0;

drivers/md/dm-table.c

@@ -1954,12 +1954,14 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 	/*
 	 * For a zoned target, the number of zones should be updated for the
 	 * correct value to be exposed in sysfs queue/nr_zones. For a BIO based
-	 * target, this is all that is needed. For a request based target, the
-	 * queue zone bitmaps must also be updated.
-	 * Use blk_revalidate_disk_zones() to handle this.
+	 * target, this is all that is needed.
 	 */
-	if (blk_queue_is_zoned(q))
-		blk_revalidate_disk_zones(t->md->disk);
+#ifdef CONFIG_BLK_DEV_ZONED
+	if (blk_queue_is_zoned(q)) {
+		WARN_ON_ONCE(queue_is_mq(q));
+		q->nr_zones = blkdev_nr_zones(t->md->disk);
+	}
+#endif
 
 	/* Allow reads to exceed readahead limits */
 	q->backing_dev_info->io_pages = limits->max_sectors >> (PAGE_SHIFT - 9);

include/linux/blkdev.h

@@ -375,11 +375,6 @@ static inline unsigned int blkdev_nr_zones(struct gendisk *disk)
 	return 0;
 }
 
-static inline int blk_revalidate_disk_zones(struct gendisk *disk)
-{
-	return 0;
-}
-
 static inline int blkdev_report_zones_ioctl(struct block_device *bdev,
 					    fmode_t mode, unsigned int cmd,
 					    unsigned long arg)