From cb6eb4757e1ea7867bcfe4b8a8b6199cc803b8c2 Mon Sep 17 00:00:00 2001 From: Anand Jain Date: Thu, 7 Sep 2023 00:16:41 +0800 Subject: [PATCH] btrfs: comment about fsid and metadata_uuid relationship Add a comment explaining the relationship between fsid and metadata_uuid in the on-disk superblock and the in-memory struct btrfs_fs_devices. Signed-off-by: Anand Jain Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/volumes.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index 2128a032c3b74..576bfcb5b7648 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]; -- 2.30.2