btrfs: zoned: allow DUP on meta-data block groups

Allow creating or reading block-groups on a zoned device with DUP as a
meta-data profile.

This works because we're using the zoned_meta_io_lock and REQ_OP_WRITE
operations for meta-data on zoned btrfs, so all writes to meta-data zones
are aligned to the zone's write-pointer.

Upon loading of the block-group, it is ensured both zones do have the same
zone capacity and write-pointer offsets, so no extra machinery is needed
to keep the write-pointers in sync for the meta-data zones. If this
prerequisite is not met, loading of the block-group is refused.
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/zoned.c

@@ -1419,6 +1419,42 @@ int btrfs_load_block_group_zone_info(struct btrfs_block_group *cache, bool new)
 		cache->zone_is_active = test_bit(0, active);
 		break;
 	case BTRFS_BLOCK_GROUP_DUP:
+		if (map->type & BTRFS_BLOCK_GROUP_DATA) {
+			btrfs_err(fs_info, "zoned: profile DUP not yet supported on data bg");
+			ret = -EINVAL;
+			goto out;
+		}
+		if (alloc_offsets[0] == WP_MISSING_DEV) {
+			btrfs_err(fs_info,
+			"zoned: cannot recover write pointer for zone %llu",
+				physical[0]);
+			ret = -EIO;
+			goto out;
+		}
+		if (alloc_offsets[1] == WP_MISSING_DEV) {
+			btrfs_err(fs_info,
+			"zoned: cannot recover write pointer for zone %llu",
+				physical[1]);
+			ret = -EIO;
+			goto out;
+		}
+		if (alloc_offsets[0] != alloc_offsets[1]) {
+			btrfs_err(fs_info,
+			"zoned: write pointer offset mismatch of zones in DUP profile");
+			ret = -EIO;
+			goto out;
+		}
+		if (test_bit(0, active) != test_bit(1, active)) {
+			if (!btrfs_zone_activate(cache)) {
+				ret = -EIO;
+				goto out;
+			}
+		} else {
+			cache->zone_is_active = test_bit(0, active);
+		}
+		cache->alloc_offset = alloc_offsets[0];
+		cache->zone_capacity = min(caps[0], caps[1]);
+		break;
 	case BTRFS_BLOCK_GROUP_RAID1:
 	case BTRFS_BLOCK_GROUP_RAID0:
 	case BTRFS_BLOCK_GROUP_RAID10: