btrfs package
*************


Submodules
==========


btrfs.crc32c module
===================


btrfs.ctree module
==================

This module contains Python object representations for btrfs metadata
items.

Additionally, the helper "FileSystem" provides a convenient way to
start exploring an online btrfs filesystem.

btrfs.ctree.U8(n)

   Parameters:
      **n** (*int*) -- Any number.

   Returns:
      Unsigned 8 bit number.

   Return type:
      int

   Example:

      >>> btrfs.ctree.U8(64)
      64
      >>> btrfs.ctree.U8(-1)
      255
      >>> btrfs.ctree.U8(0x4000)
      0

btrfs.ctree.ULL(n)

   Parameters:
      **n** (*int*) -- Any number.

   Returns:
      Unsigned 64 bit number.

   Return type:
      int

   Example:

      >>> btrfs.ctree.ULL(64)
      64
      >>> btrfs.ctree.ULL(-1)
      18446744073709551615
      >>> btrfs.ctree.ULL(0x4000)
      16384

btrfs.ctree.ROOT_TREE_OBJECTID = 1

   Root tree

btrfs.ctree.EXTENT_TREE_OBJECTID = 2

   Extent tree

btrfs.ctree.CHUNK_TREE_OBJECTID = 3

   Chunk tree

btrfs.ctree.DEV_TREE_OBJECTID = 4

   Device tree

btrfs.ctree.FS_TREE_OBJECTID = 5

   Top level subvolume tree

btrfs.ctree.ROOT_TREE_DIR_OBJECTID = 6

   Used in the root tree to store default subvolume information.

btrfs.ctree.CSUM_TREE_OBJECTID = 7

   Checksum tree

btrfs.ctree.QUOTA_TREE_OBJECTID = 8

   Quota tree

btrfs.ctree.UUID_TREE_OBJECTID = 9

   Subvolume UUID tree

btrfs.ctree.FREE_SPACE_TREE_OBJECTID = 10

   Free space tree

btrfs.ctree.BLOCK_GROUP_TREE_OBJECTID = 11

   Block group tree

btrfs.ctree.DEV_STATS_OBJECTID = 0

   Object ID of device statistics in the Device tree.

btrfs.ctree.BALANCE_OBJECTID = 18446744073709551612

   Object ID to store balance status. (-4)

btrfs.ctree.ORPHAN_OBJECTID = 18446744073709551611

   Object ID to store orphans that need cleaning. (-5)

btrfs.ctree.EXTENT_CSUM_OBJECTID = 18446744073709551606

   Object ID used for checksum items. (-10)

btrfs.ctree.FREE_SPACE_OBJECTID = 18446744073709551605

   Object ID for free space cache v1 items. (-11)

btrfs.ctree.FIRST_FREE_OBJECTID = 256

   First available Object ID for subvolume trees.

btrfs.ctree.LAST_FREE_OBJECTID = 18446744073709551360

   Last available Object ID for subvolume trees. (-256)

btrfs.ctree.FIRST_CHUNK_TREE_OBJECTID = 256

   Object ID for Chunk objects in the Chunk tree.

btrfs.ctree.DEV_ITEMS_OBJECTID = 1

   Object ID for Device items in the Device tree.

btrfs.ctree.INODE_ITEM_KEY = 1

   Key type used by "InodeItem"

btrfs.ctree.INODE_REF_KEY = 12

   Key type used by "InodeRefList"

btrfs.ctree.XATTR_ITEM_KEY = 24

   Key type used by "XAttrItemList"

btrfs.ctree.ORPHAN_ITEM_KEY = 48

   Key type used to track orphaned roots.

btrfs.ctree.DIR_ITEM_KEY = 84

   Key type used by "DirItemList"

btrfs.ctree.DIR_INDEX_KEY = 96

   Key type used by "DirIndex"

btrfs.ctree.EXTENT_DATA_KEY = 108

   Key type used by "FileExtentItem"

btrfs.ctree.EXTENT_CSUM_KEY = 128

   Key type used for checksum items.

btrfs.ctree.ROOT_ITEM_KEY = 132

   Key type used by "RootItem"

btrfs.ctree.ROOT_REF_KEY = 156

   Key type used by "RootRef"

btrfs.ctree.EXTENT_ITEM_KEY = 168

   Key type used by "ExtentItem"

btrfs.ctree.METADATA_ITEM_KEY = 169

   Key type used by "MetaDataItem"

btrfs.ctree.TREE_BLOCK_REF_KEY = 176

   Key type used by "TreeBlockRef"

btrfs.ctree.EXTENT_DATA_REF_KEY = 178

   Key type used by "ExtentDataRef"

btrfs.ctree.SHARED_BLOCK_REF_KEY = 182

   Key type used by "SharedBlockRef"

btrfs.ctree.SHARED_DATA_REF_KEY = 184

   Key type used by "SharedDataRef"

btrfs.ctree.BLOCK_GROUP_ITEM_KEY = 192

   Key type used by "BlockGroupItem"

btrfs.ctree.FREE_SPACE_INFO_KEY = 198

   Key type used by "FreeSpaceInfo"

btrfs.ctree.FREE_SPACE_EXTENT_KEY = 199

   Key type used by "FreeSpaceExtent"

btrfs.ctree.FREE_SPACE_BITMAP_KEY = 200

   Key type used by "FreeSpaceBitmap"

btrfs.ctree.DEV_EXTENT_KEY = 204

   Key type used by "DevExtent"

btrfs.ctree.DEV_ITEM_KEY = 216

   Key type used by "DevItem"

btrfs.ctree.CHUNK_ITEM_KEY = 228

   Key type used by "Chunk"

btrfs.ctree.BALANCE_ITEM_KEY = 248

   Balance status item key. Replaced by *TEMPORARY_ITEM_KEY*.

btrfs.ctree.TEMPORARY_ITEM_KEY = 248

   Key for various short term persistent stored items.

btrfs.ctree.DEV_STATS_KEY = 249

   Device statistics key. Replaced by *PERSISTENT_ITEM_KEY*.

btrfs.ctree.PERSISTENT_ITEM_KEY = 249

   Key for various long term persistent stored items.

btrfs.ctree.BLOCK_GROUP_SINGLE = 0

   Block Group single type. Does not exist in kernel code.

btrfs.ctree.BLOCK_GROUP_DATA = 1

   Block Group DATA type.

btrfs.ctree.BLOCK_GROUP_SYSTEM = 2

   Block Group SYSTEM type.

btrfs.ctree.BLOCK_GROUP_METADATA = 4

   Block Group METADATA type.

btrfs.ctree.BLOCK_GROUP_RAID0 = 8

   Block Group RAID0 profile.

btrfs.ctree.BLOCK_GROUP_RAID1 = 16

   Block Group RAID1 profile.

btrfs.ctree.BLOCK_GROUP_DUP = 32

   Block Group DUP profile.

btrfs.ctree.BLOCK_GROUP_RAID10 = 64

   Block Group RAID10 profile.

btrfs.ctree.BLOCK_GROUP_RAID5 = 128

   Block Group RAID5 profile.

btrfs.ctree.BLOCK_GROUP_RAID6 = 256

   Block Group RAID6 profile.

btrfs.ctree.BLOCK_GROUP_RAID1C3 = 512

   Block Group RAID1C3 profile.

btrfs.ctree.BLOCK_GROUP_RAID1C4 = 1024

   Block Group RAID1C4 profile.

btrfs.ctree.BLOCK_GROUP_TYPE_MASK = 7

   All Block Group type bits (data, system, metadata).

btrfs.ctree.BLOCK_GROUP_PROFILE_MASK = 2040

   All Block Group profile bits (raid1, dup, etc...).

btrfs.ctree.COMPRESS_NONE = 0

   no compression at all

btrfs.ctree.COMPRESS_ZLIB = 1

   zlib compression

btrfs.ctree.COMPRESS_LZO = 2

   lzo compression

btrfs.ctree.COMPRESS_ZSTD = 3

   zstd compression

btrfs.ctree.qgroup_level(objectid)

   Helper to get qgroup level from a qgroup relation objectid.

   Parameters:
      **objectid** (*int*) -- 64-bit object ID field.

   Returns:
      qgroup level.

   Return type:
      int

btrfs.ctree.qgroup_subvid(objectid)

   Helper to get qgroup subvolume ID from a qgroup relation objectid.

   Parameters:
      **objectid** (*int*) -- 64-bit object ID field.

   Returns:
      qgroup subvolume ID.

   Return type:
      int

exception btrfs.ctree.ItemNotFoundError

   Bases: "IndexError"

   Helper exception for lookup convenience functions.

   If a convenience function on a "btrfs.ctree.FileSystem" object is
   supposed to return exactly one object at a specific location, and
   no object is found, this type of exception is raised.

   An example is the "block_group()" helper, which raises this error
   if no block group item is found at the exact specified location.

class btrfs.ctree.Key(objectid, type_, offset)

   Bases: "object"

   Btrfs metadata trees have a key space of 136-bit numbers.

   A full 136-bit tree key is composed as:
      (objectid << 72) + (type << 64) + offset

   Parameters:
      * **objectid** (*Union**[**int**, **str**]*) -- 64-bit object ID
        number or string representation.

      * **type_** (*Union**[**int**, **str**]*) -- 8-bit type number
        or string representation.

      * **offset** (*Union**[**int**, **str**]*) -- 64-bit offset
        number or string representation.

   Key objects support sorting and simple addition and subtraction.
   Also, when subtracting 1 from a zero key, the value wraps around to
   the largest value possible, vice versa.

   Example:

      >>> key1 = btrfs.ctree.Key(425, 'DIR_ITEM', 17818406)
      >>> key1
      Key(425, 84, 17818406)
      >>> str(key1)
      '(425 DIR_ITEM 17818406)'
      >>> key2 = btrfs.ctree.Key(442, btrfs.ctree.EXTENT_DATA_KEY, 0)
      >>> key2 > key1
      True

      >>> min_key = btrfs.ctree.Key(0, 0, 0)
      >>> min_key
      Key(0, 0, 0)
      >>> str(min_key)
      '(0 0 0)'
      >>> min_key - 1
      Key(18446744073709551615, 255, 18446744073709551615)
      >>> str(min_key - 1)
      '(-1 255 -1)'

   The *-1* value in the string representation is just a convenience
   way to write the maximum allowed number. The actual value for a 64
   bit number is still 18446744073709551615, and for 8 bit that's 255
   of course.

   For example, when setting up a minimum and maximum key for a
   metadata search, the arithmetic that can be done helps quickly
   defining the maximum value. The next example shows the key range
   for finding all intormation about an inode in a filesystem tree:

   Example:

      >>> inum = 31337
      >>> min_key = btrfs.ctree.Key(inum, 0, 0)
      >>> max_key = btrfs.ctree.Key(inum + 1, 0, 0) - 1
      >>>
      >>> min_key
      Key(31337, 0, 0)
      >>> max_key
      Key(31337, 255, 18446744073709551615)

   Last but not least, the utils module contains the helper function
   "parse_key_string()" to dissect a full text key string:

   Example:

      >>> btrfs.utils.parse_key_string('(535 EXTENT_DATA 0)')
      Key(535, 108, 0)

   property objectid

      Key Object ID

   property type

      Key Type

   property offset

      Key Offset

   property key

      Full numeric 136-bit key value.

class btrfs.ctree.DiskKey(data)

   Bases: "Key"

   Object representation of struct *btrfs_disk_key*.

   Objects of this type are used in metadata search results.

class btrfs.ctree.FileSystem(path)

   Bases: "object"

   The FileSystem object is a bit of a spider in the web of this
   library. It contains a lot of convenience methods providing quick
   access to all kinds of functionality.

   Parameters:
      **path** (*str*) -- Path to the mounted filesystem.

   Variables:
      * **path** (*str*) -- The filesystem path used to initialize
        this object.

      * **fsid** (*uuid.UUID*) -- Filesystem ID.

      * **nodesize** (*int*) -- B-tree node size (same as leaf size).

      * **sectorsize** (*int*) -- Smallest allocatable block size in
        bytes for storing data.

   The fsid, nodesize and sectorsize values are cached from a call to
   "fs_info()" when initializing the object.

   It is highly recommended to use the built in context manager. Doing
   so prevents leaking the internal open file descriptor.

   Example:

      >>> with btrfs.ctree.FileSystem('/') as fs:
      ...     print(fs.top_level().generation)
      ...
      3382004

   fs_info()

      Returns:
         General filesystem information.

      Return type:
         "btrfs.ioctl.FsInfo"

   dev_info(devid)

      Parameters:
         **devid** (*int*) -- Device ID.

      Returns:
         Device information.

      Return type:
         "btrfs.ioctl.DevInfo"

   dev_stats(devid, reset=False)

      Parameters:
         * **devid** (*int*) -- Device ID.

         * **reset** (*bool*) -- Reset device error counters to zero.

      Returns:
         Device statistics.

      Return type:
         "btrfs.ioctl.DevStats"

   space_info()

      Returns:
         Space information

      Return type:
         List["btrfs.ioctl.SpaceInfo"]

   search(tree, min_key=None, max_key=None)

      Retrieve all metadata items within a specific range. This is
      basically a thin wrapper around the "search_v2()" with a bit
      limited functionality, but suited for almost all use cases when
      quickly searching around.

      Parameters:
         * **tree** (*int*) -- The metadata tree we're searching in.

         * **min_key** (*btrfs.ctree.Key*) -- Minimum key value for
           items to return.

         * **max_key** (*btrfs.ctree.Key*) -- Maximum key value for
           items to return.

      Returns:
         Any metadata item found in the search range, as sub class of
         "ItemData", helped by the "btrfs.ctree.classify()" function.

      Return type:
         Iterator["ItemData"]

   devices(min_devid=1, max_devid=18446744073709551615)

      Parameters:
         * **min_devid** (*int*) -- Lowest Device ID to search for.

         * **max_devid** (*int*) -- Highest Device ID to search for.

      Returns:
         Device Items from the Chunk tree.

      Return type:
         Iterator["DevItem"]

   chunks(min_vaddr=0, max_vaddr=18446744073709551615, nr_items=None)

      Parameters:
         * **min_vaddr** (*int*) -- Lowest virtual address to search
           for.

         * **max_vaddr** (*int*) -- Highest virtual address to search
           for.

         * **nr_items** (*int*) -- Maximum amount of items to return.
           Defaults to no limit.

      Returns:
         Chunk items from the Chunk tree.

      Return type:
         Iterator["Chunk"]

   dev_extents(min_devid=1, max_devid=18446744073709551615)

      Parameters:
         * **min_devid** (*int*) -- Lowest Device ID to search for.

         * **max_devid** (*int*) -- Highest Device ID to search for.

      Returns:
         Device Extent Items from the Device tree.

      Return type:
         Iterator["DevExtent"]

   block_groups(min_vaddr=0, max_vaddr=18446744073709551615, nr_items=None)

      Parameters:
         * **min_vaddr** (*int*) -- Lowest virtual address to search
           for.

         * **max_vaddr** (*int*) -- Highest virtual address to search
           for.

         * **nr_items** (*int*) -- Maximum amount of items to return.
           Defaults to no limit.

      Returns:
         Block Group items from the Extent Tree or Block Group Tree

      Return type:
         Iterator["BlockGroupItem"]

   block_group(vaddr, length=None)

      Parameters:
         * **vaddr** (*int*) -- Starting virtual address of the block
           group.

         * **length** (*int*) -- Block group length (optional). If
           this information is already known, it can be used to
           construct an exact match for the search key.

      Returns:
         Block Group Item

      Return type:
         "BlockGroupItem"

      Raises:
         "ItemNotFoundError" if no Block Group Item can be found at
         the address.

   extents(min_vaddr=0, max_vaddr=18446744073709551615, load_data_refs=False, load_metadata_refs=False)

      Parameters:
         * **min_vaddr** (*int*) -- Lowest virtual address to search
           for.

         * **max_vaddr** (*int*) -- Highest virtual address to search
           for.

         * **load_data_refs** (*bool*) -- Parse and load backreference
           information for data extents.

         * **load_metadata_refs** (*bool*) -- Parse and load
           backreference information for metadata extents.

      Returns:
         Extent and MetaData Items from the Extent tree

      Return type:
         Iterator[Union["ExtentItem", "MetaDataItem"]]

      The 'refs' are backreference information. These sub items are
      stored inside the "ExtentItem" and "MetaDataItem" Items, and
      overflow to separately indexed items. When dealing with search
      results in user space, these backreferences are of little use to
      us, since the search API only allows us to search in tree
      leaves. So, they're ignored by default.

   top_level()

      Returns:
         The top level subvolume with ID 5, a.k.a. *FS_TREE_OBJECTID*.

      Return type:
         "RootItem"

   subvolumes(min_id=256, max_id=18446744073709551360)

      Parameters:
         * **min_id** (*int*) -- Lowest subvolume ID to search for.

         * **max_id** (*int*) -- Highest subvolume ID to search for.

      Returns:
         Root Items from the Root tree, containing subvolume
         information.

      Return type:
         Iterator["RootItem"]

   orphan_subvol_ids()

      Returns:
         ObjectID numbers of orphaned items in the Root tree.

      Return type:
         List[int]

   free_space_extents(min_vaddr=0, max_vaddr=18446744073709551615)

      Parameters:
         * **min_vaddr** (*int*) -- Minimum virtual address when
           searching for free space.

         * **max_vaddr** (*int*) -- Maximum virtual address when
           searching for free space.

      Returns:
         Free space extent information from the Free Space Tree.

      Return type:
         Iterator["btrfs.free_space_tree.FreeSpaceExtent"]

      Note:

        The Free Space Tree can contain both Free Space Extent Items
        and Free Space Bitmap Items, which contain a more compact
        representation of free space extents. This helper function
        will transparently unpack these bitmaps and return one type of
        helper object, the "FreeSpaceExtent" object.

   sync()

      Call the btrfs sync kernel function, causing a transaction
      commit.

   features()

      Returns:
         Filesystem Features.

      Return type:
         "btrfs.ioctl.FeatureFlags"

   mixed_groups()

      Returns:
         True if this filesystem used mixed block groups with metadata
         and data in the same block groups, else False.

      Return type:
         bool

   usage()

      Returns:
         Detailed filesystem usage information.

      Return type:
         "btrfs.fs_usage.FsUsage"

class btrfs.ctree.ItemData(header)

   Bases: "object"

   ItemData is a base class for all tree item types.

   Variables:
      **key** -- Key under which this item is stored in the tree.

class btrfs.ctree.SubItem

   Bases: "object"

class btrfs.ctree.DevItem(header, data)

   Bases: "ItemData"

   Object representation of struct *btrfs_dev_item*.

   A *DevItem* contains information about a single block device that
   is attached to the filesystem.

   * Tree: *CHUNK_TREE_OBJECTID* (3)

   * Key objectid: *DEV_ITEMS_OBJECTID* (1)

   * Key type: *DEV_ITEM_KEY* (216)

   * Key offset: Device ID.

   Variables:
      * **devid** (*int*) -- Device ID.

      * **total_bytes** (*int*) -- Total amount of bytes.

      * **bytes_used** (*int*) -- Total amount of allocated bytes.

      * **io_align** (*int*) -- *Not used*, set to same value as
        sector_size.

      * **io_width** (*int*) -- *Not used*, set to same value as
        sector_size.

      * **sector_size** (*int*) -- Smallest IO block size to use.

      * **type** (*int*) -- *Not used*

      * **generation** (*int*) -- *Not used*

      * **start_offset** (*int*) -- *Not used*

      * **dev_group** (*int*) -- *Not used*

      * **seek_speed** (*int*) -- *Not used*

      * **bandwidth** (*int*) -- *Not used*

      * **uuid** (*uuid.UUID*) -- Device UUID.

      * **fsid** (*uuid.UUID*) -- Filesystem ID.

class btrfs.ctree.Chunk(header, data)

   Bases: "ItemData"

   Object representation of struct *btrfs_chunk*.

   A *Chunk* is a piece of virtual address space. A *Chunk* has a 1 to
   1 relationship to a "BlockGroupItem", and a 1 to many relationship
   with a fixed amount of "Stripe" objects.

   * Tree: *CHUNK_TREE_OBJECTID* (3)

   * Key objectid: *FIRST_CHUNK_TREE_OBJECTID* (256)

   * Key type: *CHUNK_ITEM_KEY* (228)

   * Key offset: Virtual address.

   Variables:
      * **vaddr** (*int*) -- Virtual address where the Chunk starts
        (taken from the offset field of the item key).

      * **length** (*int*) -- Chunk length in bytes,

      * **owner** (*int*) -- Extent tree the chunk belongs to. *Not
        used*, always 2 now.

      * **stripe_len** (*int*) -- Hardcoded to *BTRFS_STRIPE_LEN*,
        which is 64kiB.

      * **type** (*int*) -- Block group flags for the corresponding
        block group. So, a Chunk **type** contains both Block Group
        **type** and **profile**.

      * **io_align** (*int*) -- *Not used*, see *stripe_len*.

      * **io_width** (*int*) -- *Not used*, see *stripe_len*.

      * **sector_size** (*int*) -- Smallest IO block size to use.

      * **num_stripes** (*int*) -- Amount of "Stripe" (or, also the
        amount of "Device Extent") objects related to this *Chunk*.

      * **sub_stripes** (*int*) -- A hack for *RAID10*. For *RAID10*
        this value is 2, otherwise 1.

      * **stripes** (List["Stripe"]) -- "Stripe" Items that are stored
        inside this Chunk Item.

class btrfs.ctree.Stripe(data)

   Bases: "SubItem"

   Object representation of struct *btrfs_stripe*.

   A list of *Stripe* items is hidden inside the *Chunk* item and each
   of them contains information that points to the beginning of a
   *Device Extent*, which is an actual allocated piece of physical
   disk space in which data ends up that is written to the virtual
   address space of the *Chunk*.

   Variables:
      * **devid** (*int*) -- Device ID of the device that holds the
        *Device Extent*.

      * **offset** (*int*) -- Physical address on the device where the
        *Device Extent* starts.

      * **uuid** (*uuid.UUID*) -- Device UUID of the device with the
        above listed devid.

class btrfs.ctree.DevExtent(header, data)

   Bases: "ItemData"

   Object representation of struct *btrfs_dev_extent*.

   The *Device Extent* is a range of physical address space allocated
   from one of the attached devices and used by a *Chunk* to store
   data.

   * Tree: *DEV_TREE_OBJECTID* (4)

   * Key objectid: Device ID.

   * Key type: *DEV_EXTENT_KEY* (204)

   * Key offset: Physical address.

   Variables:
      * **devid** (*int*) -- Device ID of the device that holds this
        *Device Extent* (taken from the objectid field of the item
        key).

      * **paddr** (*int*) -- Physical address on the device where the
        *Device Extent* starts (taken from the offset field of the
        item key).

      * **chunk_tree** (*int*) -- Chunk tree the device extent belongs
        to. This is always 3 now.

      * **chunk_offset** (*int*) -- Virtual address of the related
        *Chunk*.

      * **length** (*int*) -- Length in physical bytes.

      * **chunk_tree_uuid** (*uuid.UUID*) -- UUID of the chunk tree
        that this *Device Extent* belongs to. This is currently always
        the UUID of tree 3.

   property vaddr

      Alias for the chunk_offset attribute.

class btrfs.ctree.BlockGroupItem(header, data)

   Bases: "ItemData"

   Object representation of struct *btrfs_block_group_item*.

   The *Block Group* has a 1 to 1 relationship with a *Chunk* and
   tracks some usage information about a range of virtual address
   space.

   * Tree: *EXTENT_TREE_OBJECTID* (2) or *BLOCK_GROUP_TREE_OBJECTID*
     (11)

   * Key objectid: Virtual address.

   * Key type: *BLOCK_GROUP_ITEM_KEY* (192)

   * Key offset: Block Group length.

   If the block_group_tree feature is enabled on the filesystem, these
   items can be found inside the Block Group Tree instead of the
   Extent Tree.

   Variables:
      * **vaddr** (*int*) -- Virtual address where the Bock Group
        starts (taken from the objectid field of the item key).

      * **length** (*int*) -- Block Group length in bytes (taken from
        the offset field of the item key).

      * **used** (*int*) -- Amount of bytes used by Extents in the
        Block Group.

      * **chunk_objectid** (*int*) -- Object ID of the Chunk this
        Block Group relates to. Currently always 256.

      * **flags** (*int*) -- Type and profile for this Block Group.
        e.g. 0x11, which is *DATA|RAID1*.

   property used_pct

      Convenience property that calculates the percentage of usage.

class btrfs.ctree.ExtentItem(header, data, load_data_refs=True, load_metadata_refs=True)

   Bases: "ItemData"

   Object representation of struct *btrfs_extent_item*.

   An "ExtentItem" lives in the Extent Tree and tracks information
   about a piece of virtual address space that is in use. A
   FileExtentItem object from a subvolume tree can point to it, to let
   us know a file in the filesystem uses part of this extent.

   * Tree: *EXTENT_TREE_OBJECTID* (2)

   * Key objectid: Virtual address.

   * Key type: *EXTENT_ITEM_KEY* (168)

   * Key offset: Extent length.

   If the *skinny_metadata* feature is enabled in the filesystem, then
   metadata extents are stored separately as "MetaDataItem".

   An "ExtentItem" includes inline backreference items. In the kernel,
   this information is used to be able to find out which different
   inodes in subvolume trees are using data from this extent. For us,
   in userspace, this information is not very relevant, since we
   cannot look into B-tree nodes using the kernel search API. So, by
   default the backreference information is ignored when creating
   these kind of objects from a metadata search.

   Instead, to find out who is referencing data from an extent, the
   "btrfs.ioctl.logical_ino()" and "btrfs.ioctl.logical_ino_v2()"
   functions can be used.

   Variables:
      * **vaddr** (*int*) -- Virtual address where the Extent starts
        (taken from the objectid field of the item key).

      * **length** (*int*) -- Length of the extent in bytes (taken
        from the offset field of the item key).

      * **refs** (*int*) -- Amount of explicit references to this
        extent.

      * **generation** (*int*) -- Generation of the filesystem when
        this extent was created.

      * **flags** (*int*) -- Some flags describing which type of
        extent this is.

   The flags are an or-ed combination of one or more of the following
   values (available as attribute of this module):

   * EXTENT_FLAG_DATA: This extent contains data.

   * EXTENT_FLAG_TREE_BLOCK: This extent contains a metadata tree
     block.

   * BLOCK_FLAG_FULL_BACKREF: The tree block backreference contains a
     full back reference.

   When backreference information is being loaded, there are a few
   additional lists present in this object. Also, when using the
   "FileSystem.extents()" helper to retrieve extent information, then
   separately stored backreference items which do not fit into the
   extent item itself any more are also appended to these lists:

   If the extent is a data extent, then this object contains:

   Variables:
      * **extent_data_refs** (List[Union["InlineExtentDataRef",
        "ExtentDataRef"]]) -- Indirect back references.

      * **shared_data_refs** (List[Union["InlineSharedDataRef",
        "SharedDataRef"]]) -- Shared back references.

   If the extent is a metadata tree block, then this object contains:

   Variables:
      * **tree_block_refs** (List[Union["InlineTreeBlockRef",
        "TreeBlockRef"]]) -- Tree block backreferences.

      * **shared_block_refs** (List[Union["InlineSharedBlockRef",
        "SharedBlockRef"]]) -- Shared tree block backreferences.

   Further documentation of backreferences is out of scope for this
   module. Please refer to the btrfs wiki about resolving extent
   backreferences for more information.

class btrfs.ctree.ExtentDataRef(header, data)

   Bases: "ItemData"

   Object representation of struct *btrfs_extent_data_ref*.

   Documentation of this item is out of scope for this module. Please
   refer to the btrfs wiki about resolving extent backreferences for
   more information.

   * Tree: *EXTENT_TREE_OBJECTID* (2)

   * Key type: *EXTENT_DATA_REF_KEY* (178)

   Variables:
      * **root** (*int*) -- root

      * **objectid** (*int*) -- objectid

      * **offset** (*int*) -- offset

      * **count** (*int*) -- count

class btrfs.ctree.InlineExtentDataRef(data)

   Bases: "ExtentDataRef"

   Identical content to "ExtentDataRef", but the backreference was
   inlined in the extent item.

class btrfs.ctree.SharedDataRef(header, data)

   Bases: "ItemData"

   Object representation of struct *btrfs_shared_data_ref*.

   Documentation of this item is out of scope for this module. Please
   refer to the btrfs wiki about resolving extent backreferences for
   more information.

   * Tree: *EXTENT_TREE_OBJECTID* (2)

   * Key type: *SHARED_DATA_REF_KEY* (184)

   Variables:
      * **parent** (*int*) -- parent

      * **count** (*int*) -- count

class btrfs.ctree.InlineSharedDataRef(data)

   Bases: "SharedDataRef"

   Identical content to "SharedDataRef", but the backreference was
   inlined in the extent item.

class btrfs.ctree.TreeBlockInfo(data)

   Bases: "SubItem"

   Object representation of struct *btrfs_tree_block_info*.

   Documentation of this item is out of scope for this module. Please
   refer to the btrfs wiki about resolving extent backreferences for
   more information.

   Variables:
      * **key** ("Key") -- key

      * **level** (*int*) -- level

class btrfs.ctree.MetaDataItem(header, data, load_refs=True)

   Bases: "ItemData"

   Object representation of struct *btrfs_metadata_item*.

   A "MetaDataItem" lives in the Extent Tree and tracks information
   about a piece of virtual address space that is in use to store a
   metadata tree block.

   * Tree: *EXTENT_TREE_OBJECTID* (2)

   * Key objectid: Virtual address.

   * Key type: *METADATA_ITEM_KEY* (169)

   * Key offset: Extent length.

   If the *skinny_metadata* filesystem feature is enabled, metadata
   extents are tracked using this item type, which encodes all
   necessecary data in a more compact way than using a regular extent
   item.

   Variables:
      * **vaddr** (*int*) -- Virtual address where the Extent starts
        (taken from the objectid field of the item key).

      * **skinny_level** (*int*) -- Tree level. field of the item
        key).

      * **refs** (*int*) -- Amount of explicit references to this
        extent.

      * **generation** (*int*) -- Generation of the filesystem when
        this extent was created.

      * **flags** (*int*) -- See below.

   The flags are an or-ed combination of one or more of the following
   values (available as attribute of this module):

   * EXTENT_FLAG_TREE_BLOCK: This extent contains a metadata tree
     block.

   * BLOCK_FLAG_FULL_BACKREF: The tree block backreference contains a
     full back reference.

   When backreference information is being loaded, there are a few
   additional lists present in this object. Also, when using the
   "FileSystem.extents()" helper to retrieve extent information, then
   separately stored backreference items which do not fit into the
   extent item itself any more are also appended to these lists:

   Variables:
      * **tree_block_refs** (List[Union["InlineTreeBlockRef",
        "TreeBlockRef"]]) -- Tree block backreferences.

      * **shared_block_refs** (List[Union["InlineSharedBlockRef",
        "SharedBlockRef"]]) -- Shared tree block backreferences.

   Further documentation of backreferences is out of scope for this
   module. Please refer to the btrfs wiki about resolving extent
   backreferences for more information.

class btrfs.ctree.TreeBlockRef(header)

   Bases: "ItemData"

   Tree block reference

   Documentation of this item is out of scope for this module. Please
   refer to the btrfs wiki about resolving extent backreferences for
   more information.

   * Tree: *EXTENT_TREE_OBJECTID* (2)

   * Key type: *TREE_BLOCK_REF_KEY* (176)

   Variables:
      **root** (*int*) -- root

class btrfs.ctree.InlineTreeBlockRef(root)

   Bases: "TreeBlockRef"

   Identical content to "TreeBlockRef", but the backreference was
   inlined in the extent item.

class btrfs.ctree.SharedBlockRef(header)

   Bases: "ItemData"

   Shared tree block reference

   Documentation of this item is out of scope for this module. Please
   refer to the btrfs wiki about resolving extent backreferences for
   more information.

   * Tree: *EXTENT_TREE_OBJECTID* (2)

   * Key type: *SHARED_BLOCK_REF_KEY* (182)

   Variables:
      **parent** (*int*) -- parent

class btrfs.ctree.InlineSharedBlockRef(parent)

   Bases: "SharedBlockRef"

   Identical content to "SharedBlockRef", but the backreference was
   inlined in the extent item.

class btrfs.ctree.TimeSpec(data)

   Bases: "object"

   Object representation of struct *btrfs_timespec*.

   The "TimeSpec" type of item is used embedded in other metadata
   items when a time value needs to be stored. Examples are the mtime,
   ctime etc fields in an inode item.

   It's also possible to create objects of this type manually. To do
   so, use the static "from_values()" helper function. (The regular
   object constructor is reserved for the code parsing metadata items
   from search queries.)

   Variables:
      * **sec** (*int*) -- seconds

      * **nsec** (*int*) -- nanoseconds

   Example:

      >>> my_time = btrfs.ctree.TimeSpec.from_values(1546280270, 4044945)
      >>> my_time.sec
      1546280270
      >>> my_time.nsec
      4044945
      >>> my_time.iso8601
      '2018-12-31T18:17:50.404495'

   static from_values(sec, nsec)

      Create a Timespec object

      Parameters:
         * **sec** (*int*) -- seconds

         * **nsec** (*int*) -- nanoseconds

   property iso8601

      Return the timestamp as ISO8601 formatted string.

class btrfs.ctree.InodeItem(header, data)

   Bases: "ItemData"

   Object representation of struct *btrfs_inode_item*.

   The inode item stores information of a single file or directory.
   Not the name, because a file can have multiple names.

   * Tree: *FS_TREE_OBJECTID* (5) or any other subvolume tree.

   * Key objectid: Inode number.

   * Key type: *INODE_ITEM_KEY* (1)

   * Key offset: 0

   Variables:
      * **objectid** (*int*) -- The inode number. (taken from the
        objectid field of the item key).

      * **generation** (*int*) -- Generation of the filesystem when
        the inode was created.

      * **transid** (*int*) -- Generation of the filesystem when the
        inode was last changed.

      * **size** (*int*) -- File size in bytes.

      * **nbytes** (*int*) -- Allocated disk blocks for this file in
        bytes.

      * **block_group** (*int*) -- Only used for free space cache v1,
        for which it's the related block group virtual address.

      * **nlink** (*int*) -- Amount of hardlinks the file has.

      * **uid** (*int*) -- Numerical user id of the owner of the file.

      * **gid** (*int*) -- Numerical group id of the owner of the
        file.

      * **mode** (*int*) -- File permissions.

      * **rdev** (*int*) -- Major and minor device numbers for special
        files.

      * **flags** (*int*) -- Inode flags, see below.

      * **sequence** (*int*) -- Sequence number for NFS.

      * **atime** ("TimeSpec") -- Time of last access.

      * **ctime** ("TimeSpec") -- Time of last file metadata change.
        Also updated when file contents change.

      * **mtime** ("TimeSpec") -- Time of last modification to file
        contents.

      * **otime** ("TimeSpec") -- Time of file birth.

   The flags are an or-ed combination of one or more of the following
   values (available as attribute of this module):

   * INODE_NODATASUM

   * INODE_NODATACOW

   * INODE_READONLY

   * INODE_NOCOMPRESS

   * INODE_PREALLOC

   * INODE_SYNC

   * INODE_IMMUTABLE

   * INODE_APPEND

   * INODE_NODUMP

   * INODE_NOATIME

   * INODE_DIRSYNC

   * INODE_COMPRESS

class btrfs.ctree.InodeRefList(header, data)

   Bases: "ItemData", "MutableSequence"

   A collection of struct *btrfs_inode_ref* indexed under a single
   tree key.

   A "InodeRefList" is a list of "InodeRef" objects which contain
   information about every name the inode is known under in a single
   directory. So, when we already know the inode number of a file, we
   can find in which places it has hardlinks pointing at it.

   * Tree: *FS_TREE_OBJECTID* (5) or any other subvolume tree.

   * Key objectid: Inode number.

   * Key type: *INODE_REF_KEY* (12)

   * Key offset: Inode number of the containing directory.

   This class is a helper that does not exist in Btrfs itself.

   Besides acting as an immutable list of "InodeRef" objects, there
   are some additional attributes:

   Variables:
      * **objectid** (*int*) -- Inode number of the file. (taken from
        the objectid field of the item key)

      * **parent_objectid** (*int*) -- Inode number of the containing
        directory. (taken from the offset field of the item key)

   insert(index, value)

      Not implemented.

class btrfs.ctree.InodeRef(data, pos)

   Bases: "SubItem"

   Object representation of struct *btrfs_inode_ref*.

   Also see "InodeRefList".

   Variables:
      * **index** (*int*) -- Directory index number in the containing
        directory. Refer to the *parent_objectid* attribute of the
        "InodeRefList" object that contains this "InodeRef" to find
        the inode number of the directory.

      * **name_len** (*int*) -- Amount of bytes used to store the
        filename.

      * **name** (*bytes*) -- Filename as bytes.

class btrfs.ctree.InodeExtrefList(header, data)

   Bases: "ItemData", "MutableSequence"

   A collection of struct *btrfs_inode_extref* indexed under a single
   tree key.

   A "InodeExtrefList" is a list of "InodeExtref" objects. By default,
   names under which a file is known are stored in the "InodeRefList"
   of "InodeRef". However, if a file has so many hardlinks that that
   item would become bigger than a metadata page, the rest of the
   items are stored separately.

   * Tree: *FS_TREE_OBJECTID* (5) or any other subvolume tree.

   * Key objectid: Inode number.

   * Key type: *INODE_EXTREF_KEY* (13)

   * Key offset: "extref_hash()" of the filename.

   The "InodeExtref" item is a list because multiple different
   filenames can end up having the same crc32 value.

   This class is a helper that does not exist in Btrfs itself.

   Besides acting as an immutable list of "InodeExtRef" objects, there
   are some additional attributes:

   Variables:
      * **objectid** (*int*) -- Inode number of the file. (taken from
        the objectid field of the item key)

      * **extref_hash** (*int*) -- "extref_hash()" of the filename.
        (taken from the offset field of the item key)

   insert(index, value)

      Not implemented.

class btrfs.ctree.InodeExtref(data, pos)

   Bases: "object"

   Object representation of struct *btrfs_inode_extref*.

   Also see "InodeExtrefList".

   Variables:
      * **parent_objectid** (*int*) -- Inode number of the containing
        directory.

      * **index** (*int*) -- Directory index number in the containing
        directory.

      * **name_len** (*int*) -- Amount of bytes used to store the
        filename.

      * **name** (*bytes*) -- Filename as bytes.

class btrfs.ctree.DirItemList(header, data)

   Bases: "ItemData", "MutableSequence"

   A collection of struct *btrfs_dir_item* indexed under a single tree
   key.

   A "DirItemList" is a list of "DirItem" objects. Based on a filename
   hash, they point to the inode item for the corresponding file.
   Since multiple different filenames can end up having the same name
   hash, this item can contain multiple "DirItem" objects.

   * Tree: *FS_TREE_OBJECTID* (5) or any other subvolume tree.

   * Key objectid: Inode number of the directory.

   * Key type: *DIR_ITEM_KEY* (84)

   * Key offset: "name_hash()" of the filename.

   This class is a helper that does not exist in Btrfs itself.

   Besides acting as an immutable list of "DirItem" objects, there are
   some additional attributes:

   Variables:
      * **objectid** (*int*) -- Inode number of the directory. (taken
        from the objectid field of the item key)

      * **name_hash** (*int*) -- "name_hash()" of the filename. (taken
        from the offset field of the item key)

   insert(index, value)

      Not implemented.

class btrfs.ctree.XAttrItemList(header, data)

   Bases: "DirItemList"

   A collection of struct *btrfs_dir_item*, used to store extended
   attributes and indexed under a single tree key.

   An "XAttrItemList" is a list of "XAttrItem" objects, which contain
   key value pairs in the *name* and *data* fields of the dir_item
   struct.  Since multiple different keys can end up having the same
   name hash, this item can contain multiple "XAttrItem" objects.

   * Tree: *FS_TREE_OBJECTID* (5) or any other subvolume tree.

   * Key objectid: Inode number of a file on which the xattr is set.

   * Key type: *XATTR_ITEM_KEY* (24)

   * Key offset: "name_hash()" of the key.

   This class is a helper that does not exist in Btrfs itself.

   Besides acting as an immutable list of "XAttrItem" objects, there
   are some additional attributes:

   Variables:
      * **objectid** (*int*) -- Inode number of a file on which the
        xattr is set. (taken from the objectid field of the item key)

      * **name_hash** (*int*) -- "name_hash()" of the xattr key.
        (taken from the offset field of the item key)

class btrfs.ctree.DirItem(data, pos)

   Bases: "SubItem"

   Object representation of struct *btrfs_dir_item*.

   Based on the name hash of a filename, this object directly points
   to the inode item for the corresponding file. Using this mapping
   allows quick file access when the name is known, even in
   directories with a large amount of files in them.

   Also see "DirItemList".

   Variables:
      * **location** ("DiskKey") -- Key of the file inode item.

      * **transid** (*int*) -- Generation of the filesystem when this
        item was created.

      * **data_len** (*int*) -- *Not used*, always 0.

      * **name_len** (*int*) -- Amount of bytes used to store the
        filename.

      * **type** (*int*) -- File type that is represented by the inode
        item that is being referenced.

      * **name** (*bytes*) -- Filename as bytes.

   File type is one of the following values (available as attribute of
   this module):

   * FT_UNKNOWN

   * FT_REG_FILE

   * FT_DIR

   * FT_CHRDEV

   * FT_BLKDEV

   * FT_FIFO

   * FT_SOCK

   * FT_SYMLINK

   * FT_XATTR

   * FT_MAX

class btrfs.ctree.XAttrItem(data, pos)

   Bases: "DirItem"

   Object representation of struct *btrfs_dir_item*, used to store
   extended attribute information.

   This object contains a key and value for an extended attribute on a
   file. It reuses the *dir_item* data structure.

   Also see "XattrItemList".

   Variables:
      * **transid** (*int*) -- Generation of the filesystem when this
        item was created.

      * **name_len** (*int*) -- Amount of bytes used to store the key.

      * **data_len** (*int*) -- Amount of bytes used to store the
        value.

      * **name** (*bytes*) -- Key as bytes.

      * **data** (*bytes*) -- Value as bytes.

class btrfs.ctree.DirIndex(header, data)

   Bases: "ItemData"

   Object representation of struct *btrfs_dir_item*, but used to store
   filenames ordered on directory index.

   The "DirIndex" objects list the contents of a directory in the
   order in which items were added.

   * Tree: *FS_TREE_OBJECTID* (5) or any other subvolume tree.

   * Key objectid: Inode number of the directory.

   * Key type: *DIR_INDEX_KEY* (96)

   * Key offset: Index in the directory.

   Variables:
      * **objectid** (*int*) -- Inode number of the directory. (taken
        from the objectid field of the item key)

      * **index** (*int*) -- Index in the directory. (taken from the
        offset field of the item key)

      * **location** ("DiskKey") -- Key of the file inode item.

      * **transid** (*int*) -- Generation of the filesystem when this
        item was created.

      * **data_len** (*int*) -- *Not used*, always 0.

      * **name_len** (*int*) -- Amount of bytes used to store the
        filename.

      * **type** (*int*) -- File type that is represented by the inode
        item that is being referenced.

      * **name** (*bytes*) -- Filename as bytes.

   File type is one of the following values (available as attribute of
   this module):

   * FT_UNKNOWN

   * FT_REG_FILE

   * FT_DIR

   * FT_CHRDEV

   * FT_BLKDEV

   * FT_FIFO

   * FT_SOCK

   * FT_SYMLINK

   * FT_XATTR

   * FT_MAX

class btrfs.ctree.RootItem(header, data)

   Bases: "ItemData"

   Object representation of struct *btrfs_root_item*.

   The "RootItem" lives in the root tree, a.k.a. the 'tree of trees'.
   It contains information about the root metadata node of another
   tree.

   * Tree: *ROOT_TREE_OBJECTID* (1).

   * Key objectid: Tree ID.

   * Key type: *ROOT_ITEM_KEY* (132)

   * Key offset: Index in the directory.

   Variables:
      * **objectid** (*int*) -- Tree ID. (taken from the objectid
        field of the item key)

      * **inode** ("InodeItem") -- Embedded inode item. Only the flags
        field of it is used.

      * **generation** (*int*) -- Generation of the filesystem when
        this root was created.

      * **root_dirid** (*int*) -- Objectid for the root directory in a
        subvolume tree (always 256 in that case). 0 for other trees.

      * **bytenr** (*int*) -- Virtual address of the root node of this
        tree.

      * **byte_limit** (*int*) -- *Not used*

      * **bytes_used** (*int*) -- *Not used*

      * **last_snapshot** (*int*) -- The generation of the filesystem
        when the most recent snapshot of a subvolume was made.

      * **flags** (*int*) -- See below.

      * **refs** (*int*) -- *Not used*, either 0 or 1.

      * **drop_progress** ("DiskKey") -- Key of the last removed item
        during cleanup of a removed subvolume.

      * **drop_level** (*int*) -- The tree level of the metadata node
        or leaf that contains the key from drop_progress.

      * **level** (*int*) -- The height of the tree that this root
        item refers to.

   The flags are an or-ed combination of one or more of the following
   values (available as attribute of this module):

   * ROOT_SUBVOL_RDONLY: The subvolume is read only.

   The following fields were introduced in Linux 3.6. Btrfs would
   still allow using the filesystem with an older kernel, but if the
   content of generation_v2 does not match generation, all new fields
   would be invalidated:

   Variables:
      * **generation_v2** (*int*) -- Same value as generation.

      * **uuid** ("uuid.UUID") -- Subvolume UUID.

      * **parent_uuid** ("uuid.UUID") -- Subvolume UUID that this
        subvolume is a snapshot of.

      * **received_uuid** ("uuid.UUID") -- Subvolume UUID of the
        subvolume that this subvolume was duplicated from using
        send/receive.

      * **ctransid** (*int*) -- Generation when the tree was last
        modified.

      * **otransid** (*int*) -- Generation when the tree was created.

      * **stransid** (*int*) -- Generation of the filesystem from
        which a subvolume was sent. Only used if this is a received
        subvolume.

      * **rtransid** (*int*) -- Generation of this filesystem when the
        subvolume was received.

      * **ctime** ("TimeSpec") -- Timestamp for ctransid.

      * **otime** ("TimeSpec") -- Timestamp for otransid.

      * **stime** ("TimeSpec") -- Timestamp for stransid.

      * **rtime** ("TimeSpec") -- Timestamp for rtransid.

class btrfs.ctree.RootRef(header, data)

   Bases: "ItemData"

   Object representation of *btrfs_root_ref*.

   The "RootRef" item lives in the root tree, a.k.a. the 'tree of
   trees'.  It contains information about the place where a subvolume
   is located inside another subvolume.

   * Tree: *ROOT_TREE_OBJECTID* (1).

   * Key objectid: Parent tree ID.

   * Key type: *ROOT_REF_KEY* (156)

   * Key offset: Tree ID of the subvolume.

   Variables:
      * **parent_tree** (*int*) -- Containing Tree ID. (taken from the
        objectid field of the item key)

      * **tree** (*int*) -- Tree ID of the subvolume. (taken from the
        offset field of the item key)

      * **dirid** (*int*) -- Inode number of the containing directory.

      * **sequence** (*int*) -- Directory index number in the
        containing directory.

      * **name_len** (*int*) -- Amount of bytes used to store the
        filename.

      * **name** (*bytes*) -- Filename as bytes.

   When combining this information with a call to the ino_lookup
   ioctl, we can quickly figure out the relative path inside the
   containing subvolume.

   E.g. for (259 ROOT_REF 1052) in the root tree, with dirid 20197,
   sequence 65 and name baz, we can do btrfs.ioctl.ino_lookup(fd, 259,
   20197). The result is e.g. name_bytes=b'foo/bar/', so the location
   inside the containing subvolume is foo/bar/baz.

   When doing such a thing recursively, the same output as seen in
   btrfs sub list -a can be produced.

class btrfs.ctree.FileExtentItem(header, data)

   Bases: "ItemData"

   Object representation of *btrfs_file_extent_item*.

   For every piece of a file, the "FileExtentItem" points to the data
   extent where the actual data is stored. A "FileExtentItem" does not
   have to reference a complete extent. It can also use part of it.

   * Tree: *FS_TREE_OBJECTID* (5) or any other subvolume tree.

   * Key objectid: Inode number of the file.

   * Key type: *EXTENT_DATA_KEY* (108)

   * Key offset: Logical offset in the file where the referenced data
     appears.

   Variables:
      * **objectid** (*int*) -- The inode number of the file. (taken
        from the objectid field of the item key).

      * **logical_offset** (*int*) -- Logical offset in the file where
        the referenced data appears. (taken from the offset field of
        the item key).

      * **generation** (*int*) -- Generation of the filesystem when
        this file extent was created.

      * **ram_bytes** (*int*) -- Upper limit on the memory needed in
        bytes to store the extent after decompression.

      * **compression** (*int*) -- Compression type, see below.

   The compression field can have one of the following values
   (available as attribute of this module):

   * COMPRESS_NONE

   * COMPRESS_ZLIB

   * COMPRESS_LZO

   * COMPRESS_ZSTD

   Variables:
      * **encryption** (*int*) -- *Not used* Encryption type, always
        0.

      * **other_encoding** (*int*) -- *Not used*

      * **type** (*int*) -- Type of extent, see below.

   The extent type can be one of the following:

   * FILE_EXTENT_INLINE: This is an inline extent. The data is stored
     inside
        the metadata leaf, right after the type field.

   * FILE_EXTENT_REG: This is a regular extent.

   * FILE_EXTENT_PREALLOC: Preallocated extent (for which no actual
     data is
        written yet).

   If the extent type is FILE_EXTENT_INLINE, the following fields are
   *not* available:

   Variables:
      * **disk_bytenr** (*int*) -- Virtual address of the data extent
        we reference a range from.

      * **disk_num_bytes** (*int*) -- Size of the data extent we
        reference a range from.

      * **offset** (*int*) -- The offset inside the data extent where
        the data we need starts.

      * **num_bytes** (*int*) -- The amount of bytes to be used from
        that offset onwards.

   This means that (disk_bytenr EXTENT_ITEM disk_num_bytes) is the
   tree key of the extent item in the extent tree. Also, remember that
   these numbers will always be multiples of disk block sizes, because
   that's how it gets cowed. We don't just use 1 or 2 bytes from
   another extent.

class btrfs.ctree.FreeSpaceInfo(header, data)

   Bases: "ItemData"

   Object representation of struct *btrfs_free_space_info*.

   The free space tree contains a free space info item for every block
   group.

   * Tree: *FREE_SPACE_TREE_OBJECTID* (10).

   * Key objectid: Virtual address.

   * Key type: *FREE_SPACE_INFO_KEY* (198)

   * Key offset: Block Group length.

   Variables:
      * **vaddr** (*int*) -- Virtual address. (taken from the objectid
        field of the item key)

      * **length** (*int*) -- Block Group length. (taken from the
        offset field of the item key)

      * **extent_count** (*int*) -- Amount of free space extents in
        the Block Group.

      * **flags** (*int*) -- A flag indicating if the free space for
        this Block Group is stored as bitmap. The flag is
        *FREE_SPACE_USING_BITMAPS*, available as attribute of this
        module.

class btrfs.ctree.FreeSpaceExtent(header, data)

   Bases: "ItemData"

   Object representation for free space extent information.

   * Tree: *FREE_SPACE_TREE_OBJECTID* (10).

   * Key objectid: Virtual address of the start of the free space.

   * Key type: *FREE_SPACE_EXTENT_KEY* (199)

   * Key offset: Length of the free space.

   Note that this metadata object type does not have actual item data.
   All needed information is encoded in the item key.

   Variables:
      * **vaddr** (*int*) -- Virtual address of the start of the free
        space. (taken from the objectid field of the item key)

      * **length** (*int*) -- Length of the free space. (taken from
        the offset field of the item key)

class btrfs.ctree.FreeSpaceBitmap(header, data)

   Bases: "ItemData"

   Object representation for free space bitmap information.

   * Tree: *FREE_SPACE_TREE_OBJECTID* (10).

   * Key objectid: Virtual address of the start of the free space
     bitmap.

   * Key type: *FREE_SPACE_BITMAP_KEY* (200)

   * Key offset: Length of the covered virtual address space.

   Variables:
      * **vaddr** (*int*) -- Virtual address of the start of the free
        space bitmap. (taken from the objectid field of the item key)

      * **length** (*int*) -- Length of the covered virtual address
        space. (taken from the offset field of the item key)

      * **bitmap** (*bytes*) -- The free space bitmap.

   unpack(sectorsize)

      Unpack the free space bitmap.

      Parameters:
         **sectorsize** (*int*) -- sectorsize property of the
         filesystem.

      Returns:
         A generator of "btrfs.free_space_tree.FreeSpaceExtent"
         tuples.

      Return type:
         Iterator["btrfs.free_space_tree.FreeSpaceExtent"]

class btrfs.ctree.OrphanItem(header, _)

   Bases: "ItemData"

   Object representation for orphan item information from the root
   tree.

   * Tree: *ROOT_TREE_OBJECTID* (1).

   * Key objectid: *ORPHAN_OBJECTID* (-5).

   * Key type: *ORPHAN_ITEM_KEY* (48).

   * Key offset: objectid of the item in the root tree that is
     orphaned and
        needs to be cleaned up.

   Variables:
      **objectid** (*int*) -- objectid of the item in the root tree
      that is orphaned and needs to be cleaned up. (taken from the
      offset field of the item key)

class btrfs.ctree.NotImplementedItem(header, data)

   Bases: "ItemData"

   Placeholder object for metadata item types that have not been
   implemented yet.

class btrfs.ctree.UnknownItem(header, data)

   Bases: "ItemData"

   Placeholder object for metadata item types that are unrecognized.

btrfs.ctree.classify(header, data)

   Convenience function to automatically convert an item header and
   data into one of the object types in this module.

   Parameters:
      * **header** ("btrfs.ioctl.SearchHeader") -- Search header.

      * **data** (*bytes*) -- Item data.

   Returns:
      Object representing the metadata item.

   Return type:
      Subclass of "ItemData"

   Example:

      >>> with btrfs.FileSystem('/') as fs:
      ...     chunk_tree_objects = btrfs.ioctl.search_v2(fs.fd, 3)
      ...     btrfs.utils.pretty_print(
      ...         (btrfs.ctree.classify(header, data)
      ...          for header, data in chunk_tree_objects)
      ...     )

   The search function returns a generator, which we name
   chunk_tree_objects. The pretty printer can handle any iterable, so
   the above fragment will, in a 'streaming' way, dump the chunk tree
   on the screen.


btrfs.free_space_tree module
============================


btrfs.fs_usage module
=====================


btrfs.ioctl module
==================


btrfs.utils module
==================


btrfs.volumes module
====================


Module contents
===============
