Btrfs —— Mechanisms of Btrfs & FAQ

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.