Struct btrfs_root_item

#[repr(C, packed(1))]
pub struct btrfs_root_item {

    pub inode: btrfs_inode_item,
    pub generation: c_ulonglong,
    pub root_dirid: c_ulonglong,
    pub bytenr: c_ulonglong,
    pub byte_limit: c_ulonglong,
    pub bytes_used: c_ulonglong,
    pub last_snapshot: c_ulonglong,
    pub flags: c_ulonglong,
    pub refs: c_uint,
    pub drop_progress: btrfs_disk_key,
    pub drop_level: c_uchar,
    pub level: c_uchar,
    pub generation_v2: c_ulonglong,
    pub uuid: [c_uchar; 16],
    pub parent_uuid: [c_uchar; 16],
    pub received_uuid: [c_uchar; 16],
    pub ctransid: c_ulonglong,
    pub otransid: c_ulonglong,
    pub stransid: c_ulonglong,
    pub rtransid: c_ulonglong,
    pub ctime: btrfs_timespec,
    pub otime: btrfs_timespec,
    pub stime: btrfs_timespec,
    pub rtime: btrfs_timespec,
    pub reserved: [c_ulonglong; 8],
}

Fields

inode: btrfs_inode_item

generation: c_ulonglong

root_dirid: c_ulonglong

bytenr: c_ulonglong

byte_limit: c_ulonglong

bytes_used: c_ulonglong

last_snapshot: c_ulonglong

flags: c_ulonglong

refs: c_uint

drop_progress: btrfs_disk_key

drop_level: c_uchar

level: c_uchar

generation_v2: c_ulonglong

The following fields appear after subvol_uuids+subvol_times were introduced. This generation number is used to test if the new fields are valid and up to date while reading the root item. Every time the root item is written out, the “generation” field is copied into this field. If anyone ever mounted the fs with an older kernel, we will have mismatching generation values here and thus must invalidate the new fields. See btrfs_update_root and btrfs_find_last_root for details. the offset of generation_v2 is also used as the start for the memset when invalidating the fields.

uuid: [c_uchar; 16]

parent_uuid: [c_uchar; 16]

received_uuid: [c_uchar; 16]

ctransid: c_ulonglong

updated when an inode changes

otransid: c_ulonglong

trans when created

stransid: c_ulonglong

trans when sent. non-zero for received subvol

rtransid: c_ulonglong

trans when received. non-zero for received subvol

ctime: btrfs_timespec

otime: btrfs_timespec

stime: btrfs_timespec

rtime: btrfs_timespec

reserved: [c_ulonglong; 8]

for future