"""
#define BTRFS_SUPER_INFO_OFFSET 0x00010000
/* ASCII for _BHRfS_M, no terminating nul */
#define BTRFS_MAGIC 0x4D5F53665248425F
#define BTRFS_MAX_LEVEL 8
/*
* We can actually store much bigger names, but lets not confuse the rest of
* linux.
*/
#define BTRFS_NAME_LEN 255
/*
* Theoretical limit is larger, but we keep this down to a sane value. That
* should limit greatly the possibility of collisions on inode ref items.
*/
#define BTRFS_LINK_MAX 65535
/* holds pointers to all of the tree roots */
#define BTRFS_ROOT_TREE_OBJECTID 1
/* stores information about which extents are in use, and reference counts */
#define BTRFS_EXTENT_TREE_OBJECTID 2
/*
* chunk tree stores translations from logical -> physical block numbering
* the super block points to the chunk tree
*/
#define BTRFS_CHUNK_TREE_OBJECTID 3
/*
* stores information about which areas of a given device are in use.
* one per device. The tree of tree roots points to the device tree
*/
#define BTRFS_DEV_TREE_OBJECTID 4
/* one per subvolume, storing files and directories */
#define BTRFS_FS_TREE_OBJECTID 5
/* directory objectid inside the root tree */
#define BTRFS_ROOT_TREE_DIR_OBJECTID 6
/* holds checksums of all the data extents */
#define BTRFS_CSUM_TREE_OBJECTID 7
/* holds quota configuration and tracking */
#define BTRFS_QUOTA_TREE_OBJECTID 8
/* for storing items that use the BTRFS_UUID_KEY* types */
#define BTRFS_UUID_TREE_OBJECTID 9
/* tracks free space in block groups. */
#define BTRFS_FREE_SPACE_TREE_OBJECTID 10
/* Holds the block group items for extent tree v2. */
#define BTRFS_BLOCK_GROUP_TREE_OBJECTID 11
/* device stats in the device tree */
#define BTRFS_DEV_STATS_OBJECTID 0
/* for storing balance parameters in the root tree */
#define BTRFS_BALANCE_OBJECTID -4
/* orphan objectid for tracking unlinked/truncated files */
#define BTRFS_ORPHAN_OBJECTID -5
/* does write ahead logging to speed up fsyncs */
#define BTRFS_TREE_LOG_OBJECTID -6
#define BTRFS_TREE_LOG_FIXUP_OBJECTID -7
/* for space balancing */
#define BTRFS_TREE_RELOC_OBJECTID -8
#define BTRFS_DATA_RELOC_TREE_OBJECTID -9
/*
* extent checksums all have this objectid
* this allows them to share the logging tree
* for fsyncs
*/
#define BTRFS_EXTENT_CSUM_OBJECTID -10
/* For storing free space cache */
#define BTRFS_FREE_SPACE_OBJECTID -11
/*
* The inode number assigned to the special inode for storing
* free ino cache
*/
#define BTRFS_FREE_INO_OBJECTID -12
/* dummy objectid represents multiple objectids */
#define BTRFS_MULTIPLE_OBJECTIDS -255
/*
* All files have objectids in this range.
*/
#define BTRFS_FIRST_FREE_OBJECTID 256
#define BTRFS_LAST_FREE_OBJECTID -256
#define BTRFS_FIRST_CHUNK_TREE_OBJECTID 256
/*
* the device items go into the chunk tree. The key is in the form
* [ 1 BTRFS_DEV_ITEM_KEY device_id ]
*/
#define BTRFS_DEV_ITEMS_OBJECTID 1
#define BTRFS_BTREE_INODE_OBJECTID 1
#define BTRFS_EMPTY_SUBVOL_DIR_OBJECTID 2
#define BTRFS_DEV_REPLACE_DEVID 0
/*
* inode items have the data typically returned from stat and store other
* info about object characteristics. There is one for every file and dir in
* the FS
*/
#define BTRFS_INODE_ITEM_KEY 1
#define BTRFS_INODE_REF_KEY 12
#define BTRFS_INODE_EXTREF_KEY 13
#define BTRFS_XATTR_ITEM_KEY 24
/*
* fs verity items are stored under two different key types on disk.
* The descriptor items:
* [ inode objectid, BTRFS_VERITY_DESC_ITEM_KEY, offset ]
*
* At offset 0, we store a btrfs_verity_descriptor_item which tracks the size
* of the descriptor item and some extra data for encryption.
* Starting at offset 1, these hold the generic fs verity descriptor. The
* latter are opaque to btrfs, we just read and write them as a blob for the
* higher level verity code. The most common descriptor size is 256 bytes.
*
* The merkle tree items:
* [ inode objectid, BTRFS_VERITY_MERKLE_ITEM_KEY, offset ]
*
* These also start at offset 0, and correspond to the merkle tree bytes. When
* fsverity asks for page 0 of the merkle tree, we pull up one page starting at
* offset 0 for this key type. These are also opaque to btrfs, we're blindly
* storing whatever fsverity sends down.
*/
#define BTRFS_VERITY_DESC_ITEM_KEY 36
#define BTRFS_VERITY_MERKLE_ITEM_KEY 37
#define BTRFS_ORPHAN_ITEM_KEY 48
/* reserve 2-15 close to the inode for later flexibility */
/*
* dir items are the name -> inode pointers in a directory. There is one
* for every name in a directory. BTRFS_DIR_LOG_ITEM_KEY is no longer used
* but it's still defined here for documentation purposes and to help avoid
* having its numerical value reused in the future.
*/
#define BTRFS_DIR_LOG_ITEM_KEY 60
#define BTRFS_DIR_LOG_INDEX_KEY 72
#define BTRFS_DIR_ITEM_KEY 84
#define BTRFS_DIR_INDEX_KEY 96
/*
* extent data is for file data
*/
#define BTRFS_EXTENT_DATA_KEY 108
/*
* extent csums are stored in a separate tree and hold csums for
* an entire extent on disk.
*/
#define BTRFS_EXTENT_CSUM_KEY 128
/*
* root items point to tree roots. They are typically in the root
* tree used by the super block to find all the other trees
*/
#define BTRFS_ROOT_ITEM_KEY 132
/*
* root backrefs tie subvols and snapshots to the directory entries that
* reference them
*/
#define BTRFS_ROOT_BACKREF_KEY 144
/*
* root refs make a fast index for listing all of the snapshots and
* subvolumes referenced by a given root. They point directly to the
* directory item in the root that references the subvol
*/
#define BTRFS_ROOT_REF_KEY 156
/*
* extent items are in the extent map tree. These record which blocks
* are used, and how many references there are to each block
*/
#define BTRFS_EXTENT_ITEM_KEY 168
/*
* The same as the BTRFS_EXTENT_ITEM_KEY, except it's metadata we already know
* the length, so we save the level in key->offset instead of the length.
*/
#define BTRFS_METADATA_ITEM_KEY 169
#define BTRFS_TREE_BLOCK_REF_KEY 176
#define BTRFS_EXTENT_DATA_REF_KEY 178
#define BTRFS_EXTENT_REF_V0_KEY 180
#define BTRFS_SHARED_BLOCK_REF_KEY 182
#define BTRFS_SHARED_DATA_REF_KEY 184
/*
* block groups give us hints into the extent allocation trees. Which
* blocks are free etc etc
*/
#define BTRFS_BLOCK_GROUP_ITEM_KEY 192
/*
* Every block group is represented in the free space tree by a free space info
* item, which stores some accounting information. It is keyed on
* (block_group_start, FREE_SPACE_INFO, block_group_length).
*/
#define BTRFS_FREE_SPACE_INFO_KEY 198
/*
* A free space extent tracks an extent of space that is free in a block group.
* It is keyed on (start, FREE_SPACE_EXTENT, length).
*/
#define BTRFS_FREE_SPACE_EXTENT_KEY 199
/*
* When a block group becomes very fragmented, we convert it to use bitmaps
* instead of extents. A free space bitmap is keyed on
* (start, FREE_SPACE_BITMAP, length); the corresponding item is a bitmap with
* (length / sectorsize) bits.
*/
#define BTRFS_FREE_SPACE_BITMAP_KEY 200
#define BTRFS_DEV_EXTENT_KEY 204
#define BTRFS_DEV_ITEM_KEY 216
#define BTRFS_CHUNK_ITEM_KEY 228
/*
* Records the overall state of the qgroups.
* There's only one instance of this key present,
* (0, BTRFS_QGROUP_STATUS_KEY, 0)
*/
#define BTRFS_QGROUP_STATUS_KEY 240
/*
* Records the currently used space of the qgroup.
* One key per qgroup, (0, BTRFS_QGROUP_INFO_KEY, qgroupid).
*/
#define BTRFS_QGROUP_INFO_KEY 242
/*
* Contains the user configured limits for the qgroup.
* One key per qgroup, (0, BTRFS_QGROUP_LIMIT_KEY, qgroupid).
*/
#define BTRFS_QGROUP_LIMIT_KEY 244
/*
* Records the child-parent relationship of qgroups. For
* each relation, 2 keys are present:
* (childid, BTRFS_QGROUP_RELATION_KEY, parentid)
* (parentid, BTRFS_QGROUP_RELATION_KEY, childid)
*/
#define BTRFS_QGROUP_RELATION_KEY 246
/*
* Obsolete name, see BTRFS_TEMPORARY_ITEM_KEY.
*/
#define BTRFS_BALANCE_ITEM_KEY 248
/*
* The key type for tree items that are stored persistently, but do not need to
* exist for extended period of time. The items can exist in any tree.
*
* [subtype, BTRFS_TEMPORARY_ITEM_KEY, data]
*
* Existing items:
*
* - balance status item
* (BTRFS_BALANCE_OBJECTID, BTRFS_TEMPORARY_ITEM_KEY, 0)
*/
#define BTRFS_TEMPORARY_ITEM_KEY 248
/*
* Obsolete name, see BTRFS_PERSISTENT_ITEM_KEY
*/
#define BTRFS_DEV_STATS_KEY 249
/*
* The key type for tree items that are stored persistently and usually exist
* for a long period, eg. filesystem lifetime. The item kinds can be status
* information, stats or preference values. The item can exist in any tree.
*
* [subtype, BTRFS_PERSISTENT_ITEM_KEY, data]
*
* Existing items:
*
* - device statistics, store IO stats in the device tree, one key for all
* stats
* (BTRFS_DEV_STATS_OBJECTID, BTRFS_DEV_STATS_KEY, 0)
*/
#define BTRFS_PERSISTENT_ITEM_KEY 249
/*
* Persistently stores the device replace state in the device tree.
* The key is built like this: (0, BTRFS_DEV_REPLACE_KEY, 0).
*/
#define BTRFS_DEV_REPLACE_KEY 250
/*
* Stores items that allow to quickly map UUIDs to something else.
* These items are part of the filesystem UUID tree.
* The key is built like this:
* (UUID_upper_64_bits, BTRFS_UUID_KEY*, UUID_lower_64_bits).
*/
#define BTRFS_UUID_KEY_SUBVOL 251 /* for UUIDs assigned to subvols */
#define BTRFS_UUID_KEY_RECEIVED_SUBVOL 252 /* for UUIDs assigned to received subvols */
/*
* string items are for debugging. They just store a short string of
* data in the FS
*/
#define BTRFS_STRING_ITEM_KEY 253
/* Maximum metadata block size (nodesize) */
#define BTRFS_MAX_METADATA_BLOCKSIZE 65536
/* 32 bytes in various csum fields */
#define BTRFS_CSUM_SIZE 32
/*
* flags definitions for directory entry item type
*
* Used by:
* struct btrfs_dir_item.type
*
* Values 0..7 must match common file type values in fs_types.h.
*/
#define BTRFS_FT_UNKNOWN 0
#define BTRFS_FT_REG_FILE 1
#define BTRFS_FT_DIR 2
#define BTRFS_FT_CHRDEV 3
#define BTRFS_FT_BLKDEV 4
#define BTRFS_FT_FIFO 5
#define BTRFS_FT_SOCK 6
#define BTRFS_FT_SYMLINK 7
#define BTRFS_FT_XATTR 8
#define BTRFS_FT_MAX 9
/* Directory contains encrypted data */
#define BTRFS_FT_ENCRYPTED 0x80
/*
* Inode flags
*/
#define BTRFS_INODE_NODATASUM (1 << 0)
#define BTRFS_INODE_NODATACOW (1 << 1)
#define BTRFS_INODE_READONLY (1 << 2)
#define BTRFS_INODE_NOCOMPRESS (1 << 3)
#define BTRFS_INODE_PREALLOC (1 << 4)
#define BTRFS_INODE_SYNC (1 << 5)
#define BTRFS_INODE_IMMUTABLE (1 << 6)
#define BTRFS_INODE_APPEND (1 << 7)
#define BTRFS_INODE_NODUMP (1 << 8)
#define BTRFS_INODE_NOATIME (1 << 9)
#define BTRFS_INODE_DIRSYNC (1 << 10)
#define BTRFS_INODE_COMPRESS (1 << 11)
#define BTRFS_INODE_ROOT_ITEM_INIT (1 << 31)
#define BTRFS_VOL_NAME_MAX 255
#define BTRFS_LABEL_SIZE 256
#define BTRFS_FSID_SIZE 16
#define BTRFS_UUID_SIZE 16
/* different types of block groups (and chunks) */
flag BTRFS_BLOCK_GROUP : uint64 {
DATA = 0x0001
SYSTEM = 0x0002
METADATA = 0x0004
RAID0 = 0x0008
RAID1 = 0x0010
DUP = 0x0020
RAID10 = 0x0040
RAID5 = 0x0080
RAID6 = 0x0100
RAID1C3 = 0x0200
RAID1C4 = 0x0400
};
/*
* The key defines the order in the tree, and so it also defines (optimal)
* block layout.
*
* objectid corresponds to the inode number.
*
* type tells us things about the object, and is a kind of stream selector.
* so for a given inode, keys with type of 1 might refer to the inode data,
* type of 2 may point to file data in the btree and type == 3 may point to
* extents.
*
* offset is the starting byte offset for this key in the stream.
*
* btrfs_disk_key is in disk byte order. struct btrfs_key is always
* in cpu native order. Otherwise they are identical and their sizes
* should be the same (ie both packed)
*/
struct btrfs_disk_key {
uint64 objectid;
uint8 type;
uint64 offset;
};
/*
* Every tree block (leaf or node) starts with this header.
*/
struct btrfs_header {
/* These first four must match the super block */
char csum[BTRFS_CSUM_SIZE];
/* FS specific uuid */
char fsid[BTRFS_FSID_SIZE];
/* Which block this node is supposed to live in */
uint64 bytenr;
uint64 flags;
/* Allowed to be different from the super from here on down */
char chunk_tree_uuid[BTRFS_UUID_SIZE];
uint64 generation;
uint64 owner;
uint32 nritems;
uint8 level;
};
/*
* This is a very generous portion of the super block, giving us room to
* translate 14 chunks with 3 stripes each.
*/
#define BTRFS_SYSTEM_CHUNK_ARRAY_SIZE 2048
/*
* Just in case we somehow lose the roots and are not able to mount, we store
* an array of the roots from previous transactions in the super.
*/
#define BTRFS_NUM_BACKUP_ROOTS 4
struct btrfs_root_backup {
uint64 tree_root;
uint64 tree_root_gen;
uint64 chunk_root;
uint64 chunk_root_gen;
uint64 extent_root;
uint64 extent_root_gen;
uint64 fs_root;
uint64 fs_root_gen;
uint64 dev_root;
uint64 dev_root_gen;
uint64 csum_root;
uint64 csum_root_gen;
uint64 total_bytes;
uint64 bytes_used;
uint64 num_devices;
/* future */
uint64 unused_64[4];
uint8 tree_root_level;
uint8 chunk_root_level;
uint8 extent_root_level;
uint8 fs_root_level;
uint8 dev_root_level;
uint8 csum_root_level;
/* future and to align */
char unused_8[10];
};
/*
* A leaf is full of items. offset and size tell us where to find the item in
* the leaf (relative to the start of the data area)
*/
struct btrfs_item {
struct btrfs_disk_key key;
uint32 offset;
uint32 size;
};
/*
* Leaves have an item area and a data area:
* [item0, item1....itemN] [free space] [dataN...data1, data0]
*
* The data is separate from the items to get the keys closer together during
* searches.
*/
struct btrfs_leaf {
struct btrfs_header header;
struct btrfs_item items[];
};
/*
* All non-leaf blocks are nodes, they hold only keys and pointers to other
* blocks.
*/
struct btrfs_key_ptr {
struct btrfs_disk_key key;
uint64 blockptr;
uint64 generation;
};
struct btrfs_node {
struct btrfs_header header;
struct btrfs_key_ptr ptrs[];
};
struct btrfs_dev_item {
/* the internal btrfs device id */
uint64 devid;
/* size of the device */
uint64 total_bytes;
/* bytes used */
uint64 bytes_used;
/* optimal io alignment for this device */
uint32 io_align;
/* optimal io width for this device */
uint32 io_width;
/* minimal io size for this device */
uint32 sector_size;
/* type and info about this device */
uint64 type;
/* expected generation for this device */
uint64 generation;
/*
* starting byte of this partition on the device,
* to allow for stripe alignment in the future
*/
uint64 start_offset;
/* grouping information for allocation decisions */
uint32 dev_group;
/* seek speed 0-100 where 100 is fastest */
uint8 seek_speed;
/* bandwidth 0-100 where 100 is fastest */
uint8 bandwidth;
/* btrfs generated uuid for this device */
char uuid[BTRFS_UUID_SIZE];
/* uuid of FS who owns this device */
char fsid[BTRFS_UUID_SIZE];
};
struct btrfs_stripe {
uint64 devid;
uint64 offset;
char dev_uuid[BTRFS_UUID_SIZE];
};
struct btrfs_chunk {
/* size of this chunk in bytes */
uint64 length;
/* objectid of the root referencing this chunk */
uint64 owner;
uint64 stripe_len;
BTRFS_BLOCK_GROUP type;
/* optimal io alignment for this chunk */
uint32 io_align;
/* optimal io width for this chunk */
uint32 io_width;
/* minimal io size for this chunk */
uint32 sector_size;
/* 2^16 stripes is quite a lot, a second limit is the size of a single
* item in the btree
*/
uint16 num_stripes;
/* sub stripes only matter for raid10 */
uint16 sub_stripes;
struct btrfs_stripe stripe[num_stripes];
/* additional stripes go here */
};
/*
* The super block basically lists the main trees of the FS.
*/
struct btrfs_super_block {
/* The first 4 fields must match struct btrfs_header */
char csum[BTRFS_CSUM_SIZE];
/* FS specific UUID, visible to user */
char fsid[BTRFS_FSID_SIZE];
/* This block number */
uint64 bytenr;
uint64 flags;
/* Allowed to be different from the btrfs_header from here own down */
uint64 magic;
uint64 generation;
uint64 root;
uint64 chunk_root;
uint64 log_root;
/*
* This member has never been utilized since the very beginning, thus
* it's always 0 regardless of kernel version. We always use
* generation + 1 to read log tree root. So here we mark it deprecated.
*/
uint64 __unused_log_root_transid;
uint64 total_bytes;
uint64 bytes_used;
uint64 root_dir_objectid;
uint64 num_devices;
uint32 sectorsize;
uint32 nodesize;
uint32 __unused_leafsize;
uint32 stripesize;
uint32 sys_chunk_array_size;
uint64 chunk_root_generation;
uint64 compat_flags;
uint64 compat_ro_flags;
uint64 incompat_flags;
uint16 csum_type;
uint8 root_level;
uint8 chunk_root_level;
uint8 log_root_level;
struct btrfs_dev_item dev_item;
char label[BTRFS_LABEL_SIZE];
uint64 cache_generation;
uint64 uuid_tree_generation;
/* The UUID written into btree blocks */
char metadata_uuid[BTRFS_FSID_SIZE];
uint64 nr_global_roots;
/* Future expansion */
uint64 reserved[27];
char sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE];
struct btrfs_root_backup super_roots[BTRFS_NUM_BACKUP_ROOTS];
/* Padded to 4096 bytes */
char padding[565];
};
struct btrfs_inode_ref {
uint64 index;
uint16 name_len;
char name[name_len];
};
struct btrfs_inode_extref {
uint64 parent_objectid;
uint64 index;
uint16 name_len;
char name[name_len];
};
struct btrfs_timespec {
uint64 sec;
uint32 nsec;
};
struct btrfs_inode_item {
/* nfs style generation number */
uint64 generation;
/* transid that last touched this inode */
uint64 transid;
uint64 size;
uint64 nbytes;
uint64 block_group;
uint32 nlink;
uint32 uid;
uint32 gid;
uint32 mode;
uint64 rdev;
uint64 flags;
/* modification sequence number for NFS */
uint64 sequence;
/*
* a little future expansion, for more than this we can
* just grow the inode item and version it
*/
uint64 reserved[4];
struct btrfs_timespec atime;
struct btrfs_timespec ctime;
struct btrfs_timespec mtime;
struct btrfs_timespec otime;
};
struct btrfs_dir_item {
struct btrfs_disk_key location;
uint64 transid;
uint16 data_len;
uint16 name_len;
uint8 type;
char name[name_len];
char data[data_len];
};
struct btrfs_root_item {
struct btrfs_inode_item inode;
uint64 generation;
uint64 root_dirid;
uint64 bytenr;
uint64 byte_limit;
uint64 bytes_used;
uint64 last_snapshot;
uint64 flags;
uint32 refs;
struct btrfs_disk_key drop_progress;
uint8 drop_level;
uint8 level;
/*
* 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.
*/
uint64 generation_v2;
char uuid[BTRFS_UUID_SIZE];
char parent_uuid[BTRFS_UUID_SIZE];
char received_uuid[BTRFS_UUID_SIZE];
uint64 ctransid; /* updated when an inode changes */
uint64 otransid; /* trans when created */
uint64 stransid; /* trans when sent. non-zero for received subvol */
uint64 rtransid; /* trans when received. non-zero for received subvol */
struct btrfs_timespec ctime;
struct btrfs_timespec otime;
struct btrfs_timespec stime;
struct btrfs_timespec rtime;
uint64 reserved[8]; /* for future */
};
/*
* this is used for both forward and backward root refs
*/
struct btrfs_root_ref {
uint64 dirid;
uint64 sequence;
uint16 name_len;
char name[name_len];
};
enum {
BTRFS_FILE_EXTENT_INLINE = 0,
BTRFS_FILE_EXTENT_REG = 1,
BTRFS_FILE_EXTENT_PREALLOC = 2,
BTRFS_NR_FILE_EXTENT_TYPES = 3,
};
enum {
BTRFS_COMPRESS_NONE = 0,
BTRFS_COMPRESS_ZLIB = 1,
BTRFS_COMPRESS_LZO = 2,
BTRFS_COMPRESS_ZSTD = 3,
BTRFS_NR_COMPRESS_TYPES = 4,
};
struct btrfs_file_extent_item_inline {
/*
* transaction id that created this extent
*/
uint64 generation;
/*
* max number of bytes to hold this extent in ram
* when we split a compressed extent we can't know how big
* each of the resulting pieces will be. So, this is
* an upper limit on the size of the extent in ram instead of
* an exact limit.
*/
uint64 ram_bytes;
/*
* 32 bits for the various ways we might encode the data,
* including compression and encryption. If any of these
* are set to something a given disk format doesn't understand
* it is treated like an incompat flag for reading and writing,
* but not for stat.
*/
uint8 compression;
uint8 encryption;
uint16 other_encoding; /* spare for later use */
/* are we inline data or a real extent? */
uint8 type;
};
struct btrfs_file_extent_item_reg {
/*
* transaction id that created this extent
*/
uint64 generation;
/*
* max number of bytes to hold this extent in ram
* when we split a compressed extent we can't know how big
* each of the resulting pieces will be. So, this is
* an upper limit on the size of the extent in ram instead of
* an exact limit.
*/
uint64 ram_bytes;
/*
* 32 bits for the various ways we might encode the data,
* including compression and encryption. If any of these
* are set to something a given disk format doesn't understand
* it is treated like an incompat flag for reading and writing,
* but not for stat.
*/
uint8 compression;
uint8 encryption;
uint16 other_encoding; /* spare for later use */
/* are we inline data or a real extent? */
uint8 type;
/*
* disk space consumed by the extent, checksum blocks are included
* in these numbers
*
* At this offset in the structure, the inline extent data start.
*/
uint64 disk_bytenr;
uint64 disk_num_bytes;
/*
* the logical offset in file blocks (no csums)
* this extent record is for. This allows a file extent to point
* into the middle of an existing extent on disk, sharing it
* between two snapshots (useful if some bytes in the middle of the
* extent have changed
*/
uint64 offset;
/*
* the logical number of file blocks (no csums included). This
* always reflects the size uncompressed and without encoding.
*/
uint64 num_bytes;
};
"""