Block group
Description by btrfs_space_info, espcialy btrfs_space_info->flags indictes gruop name for example BTRFS_BLOCK_GROUP_SYSTEM.
Block group item inserted in extent-tree
Stripe width & stripe size
in btrfs_alloc_chunk()
stripe width == num_stripes == numbers of device in array
stripe size == stripe_length == 64KB
貌似in btrfs_alloc_chunk 函数中, min_stripe_size是chunk size 当然这个大小是不包含 raid1的重复部分哦。好像chunk size 等于 stripe size似的。
fs_root
key.objectid = BTRFS_FS_TREE_OBJECTID;
key.type = BTRFS_ROOT_ITEM_KEY;
key.offset = (u64)-1;
fs_info->fs_root = btrfs_read_fs_root(fs_info, &key);
FAQ
Whereis first init chunk_root->root_key->objectid.
In earnth, that happend in __setup_root(). The value is BTRFS_CHUNK_TREE_OBJECTID.