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-rw-r--r--fs/btrfs/volumes.h9
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 2128a032c3b7..576bfcb5b764 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -290,6 +290,15 @@ struct btrfs_fs_devices {
* - Following shall be true at all times:
* - metadata_uuid == btrfs_header::fsid
* - metadata_uuid == btrfs_dev_item::fsid
+ *
+ * - Relations between fsid and metadata_uuid in sb and fs_devices:
+ * - Normal:
+ * fs_devices->fsid == fs_devices->metadata_uuid == sb->fsid
+ * sb->metadata_uuid == 0
+ *
+ * - When the BTRFS_FEATURE_INCOMPAT_METADATA_UUID flag is set:
+ * fs_devices->fsid == sb->fsid
+ * fs_devices->metadata_uuid == sb->metadata_uuid
*/
u8 metadata_uuid[BTRFS_FSID_SIZE];