block: inherit the zoned characteristics in blk_stack_limits

Lift the code from device mapper into blk_stack_limits to inherity
the stacking limitations.  This ensures we do the right thing for
all stacked zoned block devices.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Tested-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-settings.c

@@ -609,6 +609,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 		t->chunk_sectors = min_not_zero(t->chunk_sectors,
 						b->chunk_sectors);
 
+	t->zoned = max(t->zoned, b->zoned);
 	return ret;
 }
 EXPORT_SYMBOL(blk_stack_limits);

drivers/md/dm-table.c

@@ -467,9 +467,6 @@ static int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev,
 		       q->limits.logical_block_size,
 		       q->limits.alignment_offset,
 		       (unsigned long long) start << SECTOR_SHIFT);
-
-	limits->zoned = blk_queue_zoned_model(q);
-
 	return 0;
 }
 
@@ -1528,22 +1525,6 @@ int dm_calculate_queue_limits(struct dm_table *table,
 			       dm_device_name(table->md),
 			       (unsigned long long) ti->begin,
 			       (unsigned long long) ti->len);
-
-		/*
-		 * FIXME: this should likely be moved to blk_stack_limits(), would
-		 * also eliminate limits->zoned stacking hack in dm_set_device_limits()
-		 */
-		if (limits->zoned == BLK_ZONED_NONE && ti_limits.zoned != BLK_ZONED_NONE) {
-			/*
-			 * By default, the stacked limits zoned model is set to
-			 * BLK_ZONED_NONE in blk_set_stacking_limits(). Update
-			 * this model using the first target model reported
-			 * that is not BLK_ZONED_NONE. This will be either the
-			 * first target device zoned model or the model reported
-			 * by the target .io_hints.
-			 */
-			limits->zoned = ti_limits.zoned;
-		}
 	}
 
 	/*

include/linux/blkdev.h

@@ -306,11 +306,14 @@ enum blk_queue_state {
 
 /*
  * Zoned block device models (zoned limit).
+ *
+ * Note: This needs to be ordered from the least to the most severe
+ * restrictions for the inheritance in blk_stack_limits() to work.
  */
 enum blk_zoned_model {
-	BLK_ZONED_NONE,	/* Regular block device */
-	BLK_ZONED_HA,	/* Host-aware zoned block device */
-	BLK_ZONED_HM,	/* Host-managed zoned block device */
+	BLK_ZONED_NONE = 0,	/* Regular block device */
+	BLK_ZONED_HA,		/* Host-aware zoned block device */
+	BLK_ZONED_HM,		/* Host-managed zoned block device */
 };
 
 struct queue_limits {