zig

btrfs_tree.h (35622B) - Raw

---

 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
 #ifndef _BTRFS_CTREE_H_
 #define _BTRFS_CTREE_H_
 
 #include <linux/btrfs.h>
 #include <linux/types.h>
 #include <stddef.h>
 
 /* ASCII for _BHRfS_M, no terminating nul */
 #define BTRFS_MAGIC 0x4D5F53665248425FULL
 
 #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 65535U
 
 /*
  * This header contains the structure definitions and constants used
  * by file system objects that can be retrieved using
  * the BTRFS_IOC_SEARCH_TREE ioctl.  That means basically anything that
  * is needed to describe a leaf node's key or item contents.
  */
 
 /* holds pointers to all of the tree roots */
 #define BTRFS_ROOT_TREE_OBJECTID 1ULL
 
 /* stores information about which extents are in use, and reference counts */
 #define BTRFS_EXTENT_TREE_OBJECTID 2ULL
 
 /*
  * chunk tree stores translations from logical -> physical block numbering
  * the super block points to the chunk tree
  */
 #define BTRFS_CHUNK_TREE_OBJECTID 3ULL
 
 /*
  * 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 4ULL
 
 /* one per subvolume, storing files and directories */
 #define BTRFS_FS_TREE_OBJECTID 5ULL
 
 /* directory objectid inside the root tree */
 #define BTRFS_ROOT_TREE_DIR_OBJECTID 6ULL
 
 /* holds checksums of all the data extents */
 #define BTRFS_CSUM_TREE_OBJECTID 7ULL
 
 /* holds quota configuration and tracking */
 #define BTRFS_QUOTA_TREE_OBJECTID 8ULL
 
 /* for storing items that use the BTRFS_UUID_KEY* types */
 #define BTRFS_UUID_TREE_OBJECTID 9ULL
 
 /* tracks free space in block groups. */
 #define BTRFS_FREE_SPACE_TREE_OBJECTID 10ULL
 
 /* Holds the block group items for extent tree v2. */
 #define BTRFS_BLOCK_GROUP_TREE_OBJECTID 11ULL
 
 /* Tracks RAID stripes in block groups. */
 #define BTRFS_RAID_STRIPE_TREE_OBJECTID 12ULL
 
 /* device stats in the device tree */
 #define BTRFS_DEV_STATS_OBJECTID 0ULL
 
 /* for storing balance parameters in the root tree */
 #define BTRFS_BALANCE_OBJECTID -4ULL
 
 /* orphan objectid for tracking unlinked/truncated files */
 #define BTRFS_ORPHAN_OBJECTID -5ULL
 
 /* does write ahead logging to speed up fsyncs */
 #define BTRFS_TREE_LOG_OBJECTID -6ULL
 #define BTRFS_TREE_LOG_FIXUP_OBJECTID -7ULL
 
 /* for space balancing */
 #define BTRFS_TREE_RELOC_OBJECTID -8ULL
 #define BTRFS_DATA_RELOC_TREE_OBJECTID -9ULL
 
 /*
  * extent checksums all have this objectid
  * this allows them to share the logging tree
  * for fsyncs
  */
 #define BTRFS_EXTENT_CSUM_OBJECTID -10ULL
 
 /* For storing free space cache */
 #define BTRFS_FREE_SPACE_OBJECTID -11ULL
 
 /*
  * The inode number assigned to the special inode for storing
  * free ino cache
  */
 #define BTRFS_FREE_INO_OBJECTID -12ULL
 
 /* dummy objectid represents multiple objectids */
 #define BTRFS_MULTIPLE_OBJECTIDS -255ULL
 
 /*
  * All files have objectids in this range.
  */
 #define BTRFS_FIRST_FREE_OBJECTID 256ULL
 #define BTRFS_LAST_FREE_OBJECTID -256ULL
 #define BTRFS_FIRST_CHUNK_TREE_OBJECTID 256ULL
 
 
 /*
  * 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 1ULL
 
 #define BTRFS_BTREE_INODE_OBJECTID 1
 
 #define BTRFS_EMPTY_SUBVOL_DIR_OBJECTID 2
 
 #define BTRFS_DEV_REPLACE_DEVID 0ULL
 
 /*
  * 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
 
 /*
  * Special __inline__ ref key which stores the id of the subvolume which originally
  * created the extent. This subvolume owns the extent permanently from the
  * perspective of simple quotas. Needed to know which subvolume to free quota
  * usage from when the extent is deleted.
  *
  * Stored as an __inline__ ref rather to avoid wasting space on a separate item on
  * top of the existing extent item. However, unlike the other __inline__ refs,
  * there is one one owner ref per extent rather than one per extent.
  *
  * Because of this, it goes at the front of the list of __inline__ refs, and thus
  * must have a lower type value than any other __inline__ ref type (to satisfy the
  * disk format rule that __inline__ refs have non-decreasing type).
  */
 #define BTRFS_EXTENT_OWNER_REF_KEY	172
 
 #define BTRFS_TREE_BLOCK_REF_KEY	176
 
 #define BTRFS_EXTENT_DATA_REF_KEY	178
 
 /*
  * Obsolete key. Defintion removed in 6.6, value may be reused in the future.
  *
  * #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
 
 #define BTRFS_RAID_STRIPE_KEY	230
 
 /*
  * 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).
  */
 #if BTRFS_UUID_SIZE != 16
 #error "UUID items require BTRFS_UUID_SIZE == 16!"
 #endif
 #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
 
 /* csum types */
 enum btrfs_csum_type {
 	BTRFS_CSUM_TYPE_CRC32	= 0,
 	BTRFS_CSUM_TYPE_XXHASH	= 1,
 	BTRFS_CSUM_TYPE_SHA256	= 2,
 	BTRFS_CSUM_TYPE_BLAKE2	= 3,
 };
 
 /*
  * 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
 
 static __inline__ __u8 btrfs_dir_flags_to_ftype(__u8 flags)
 {
 	return flags & ~BTRFS_FT_ENCRYPTED;
 }
 
 /*
  * Inode flags
  */
 #define BTRFS_INODE_NODATASUM		(1U << 0)
 #define BTRFS_INODE_NODATACOW		(1U << 1)
 #define BTRFS_INODE_READONLY		(1U << 2)
 #define BTRFS_INODE_NOCOMPRESS		(1U << 3)
 #define BTRFS_INODE_PREALLOC		(1U << 4)
 #define BTRFS_INODE_SYNC		(1U << 5)
 #define BTRFS_INODE_IMMUTABLE		(1U << 6)
 #define BTRFS_INODE_APPEND		(1U << 7)
 #define BTRFS_INODE_NODUMP		(1U << 8)
 #define BTRFS_INODE_NOATIME		(1U << 9)
 #define BTRFS_INODE_DIRSYNC		(1U << 10)
 #define BTRFS_INODE_COMPRESS		(1U << 11)
 
 #define BTRFS_INODE_ROOT_ITEM_INIT	(1U << 31)
 
 #define BTRFS_INODE_FLAG_MASK						\
 	(BTRFS_INODE_NODATASUM |					\
 	 BTRFS_INODE_NODATACOW |					\
 	 BTRFS_INODE_READONLY |						\
 	 BTRFS_INODE_NOCOMPRESS |					\
 	 BTRFS_INODE_PREALLOC |						\
 	 BTRFS_INODE_SYNC |						\
 	 BTRFS_INODE_IMMUTABLE |					\
 	 BTRFS_INODE_APPEND |						\
 	 BTRFS_INODE_NODUMP |						\
 	 BTRFS_INODE_NOATIME |						\
 	 BTRFS_INODE_DIRSYNC |						\
 	 BTRFS_INODE_COMPRESS |						\
 	 BTRFS_INODE_ROOT_ITEM_INIT)
 
 #define BTRFS_INODE_RO_VERITY		(1U << 0)
 
 #define BTRFS_INODE_RO_FLAG_MASK	(BTRFS_INODE_RO_VERITY)
 
 /*
  * 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 {
 	__le64 objectid;
 	__u8 type;
 	__le64 offset;
 } __attribute__ ((__packed__));
 
 struct btrfs_key {
 	__u64 objectid;
 	__u8 type;
 	__u64 offset;
 } __attribute__ ((__packed__));
 
 /*
  * Every tree block (leaf or node) starts with this header.
  */
 struct btrfs_header {
 	/* These first four must match the super block */
 	__u8 csum[BTRFS_CSUM_SIZE];
 	/* FS specific uuid */
 	__u8 fsid[BTRFS_FSID_SIZE];
 	/* Which block this node is supposed to live in */
 	__le64 bytenr;
 	__le64 flags;
 
 	/* Allowed to be different from the super from here on down */
 	__u8 chunk_tree_uuid[BTRFS_UUID_SIZE];
 	__le64 generation;
 	__le64 owner;
 	__le32 nritems;
 	__u8 level;
 } __attribute__ ((__packed__));
 
 /*
  * 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 {
 	__le64 tree_root;
 	__le64 tree_root_gen;
 
 	__le64 chunk_root;
 	__le64 chunk_root_gen;
 
 	__le64 extent_root;
 	__le64 extent_root_gen;
 
 	__le64 fs_root;
 	__le64 fs_root_gen;
 
 	__le64 dev_root;
 	__le64 dev_root_gen;
 
 	__le64 csum_root;
 	__le64 csum_root_gen;
 
 	__le64 total_bytes;
 	__le64 bytes_used;
 	__le64 num_devices;
 	/* future */
 	__le64 unused_64[4];
 
 	__u8 tree_root_level;
 	__u8 chunk_root_level;
 	__u8 extent_root_level;
 	__u8 fs_root_level;
 	__u8 dev_root_level;
 	__u8 csum_root_level;
 	/* future and to align */
 	__u8 unused_8[10];
 } __attribute__ ((__packed__));
 
 /*
  * 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;
 	__le32 offset;
 	__le32 size;
 } __attribute__ ((__packed__));
 
 /*
  * 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[];
 } __attribute__ ((__packed__));
 
 /*
  * All non-leaf blocks are nodes, they hold only keys and pointers to other
  * blocks.
  */
 struct btrfs_key_ptr {
 	struct btrfs_disk_key key;
 	__le64 blockptr;
 	__le64 generation;
 } __attribute__ ((__packed__));
 
 struct btrfs_node {
 	struct btrfs_header header;
 	struct btrfs_key_ptr ptrs[];
 } __attribute__ ((__packed__));
 
 struct btrfs_dev_item {
 	/* the internal btrfs device id */
 	__le64 devid;
 
 	/* size of the device */
 	__le64 total_bytes;
 
 	/* bytes used */
 	__le64 bytes_used;
 
 	/* optimal io alignment for this device */
 	__le32 io_align;
 
 	/* optimal io width for this device */
 	__le32 io_width;
 
 	/* minimal io size for this device */
 	__le32 sector_size;
 
 	/* type and info about this device */
 	__le64 type;
 
 	/* expected generation for this device */
 	__le64 generation;
 
 	/*
 	 * starting byte of this partition on the device,
 	 * to allow for stripe alignment in the future
 	 */
 	__le64 start_offset;
 
 	/* grouping information for allocation decisions */
 	__le32 dev_group;
 
 	/* seek speed 0-100 where 100 is fastest */
 	__u8 seek_speed;
 
 	/* bandwidth 0-100 where 100 is fastest */
 	__u8 bandwidth;
 
 	/* btrfs generated uuid for this device */
 	__u8 uuid[BTRFS_UUID_SIZE];
 
 	/* uuid of FS who owns this device */
 	__u8 fsid[BTRFS_UUID_SIZE];
 } __attribute__ ((__packed__));
 
 struct btrfs_stripe {
 	__le64 devid;
 	__le64 offset;
 	__u8 dev_uuid[BTRFS_UUID_SIZE];
 } __attribute__ ((__packed__));
 
 struct btrfs_chunk {
 	/* size of this chunk in bytes */
 	__le64 length;
 
 	/* objectid of the root referencing this chunk */
 	__le64 owner;
 
 	__le64 stripe_len;
 	__le64 type;
 
 	/* optimal io alignment for this chunk */
 	__le32 io_align;
 
 	/* optimal io width for this chunk */
 	__le32 io_width;
 
 	/* minimal io size for this chunk */
 	__le32 sector_size;
 
 	/* 2^16 stripes is quite a lot, a second limit is the size of a single
 	 * item in the btree
 	 */
 	__le16 num_stripes;
 
 	/* sub stripes only matter for raid10 */
 	__le16 sub_stripes;
 	struct btrfs_stripe stripe;
 	/* additional stripes go here */
 } __attribute__ ((__packed__));
 
 /*
  * The super block basically lists the main trees of the FS.
  */
 struct btrfs_super_block {
 	/* The first 4 fields must match struct btrfs_header */
 	__u8 csum[BTRFS_CSUM_SIZE];
 	/* FS specific UUID, visible to user */
 	__u8 fsid[BTRFS_FSID_SIZE];
 	/* This block number */
 	__le64 bytenr;
 	__le64 flags;
 
 	/* Allowed to be different from the btrfs_header from here own down */
 	__le64 magic;
 	__le64 generation;
 	__le64 root;
 	__le64 chunk_root;
 	__le64 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.
 	 */
 	__le64 __unused_log_root_transid;
 	__le64 total_bytes;
 	__le64 bytes_used;
 	__le64 root_dir_objectid;
 	__le64 num_devices;
 	__le32 sectorsize;
 	__le32 nodesize;
 	__le32 __unused_leafsize;
 	__le32 stripesize;
 	__le32 sys_chunk_array_size;
 	__le64 chunk_root_generation;
 	__le64 compat_flags;
 	__le64 compat_ro_flags;
 	__le64 incompat_flags;
 	__le16 csum_type;
 	__u8 root_level;
 	__u8 chunk_root_level;
 	__u8 log_root_level;
 	struct btrfs_dev_item dev_item;
 
 	char label[BTRFS_LABEL_SIZE];
 
 	__le64 cache_generation;
 	__le64 uuid_tree_generation;
 
 	/* The UUID written into btree blocks */
 	__u8 metadata_uuid[BTRFS_FSID_SIZE];
 
 	__u64 nr_global_roots;
 
 	/* Future expansion */
 	__le64 reserved[27];
 	__u8 sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE];
 	struct btrfs_root_backup super_roots[BTRFS_NUM_BACKUP_ROOTS];
 
 	/* Padded to 4096 bytes */
 	__u8 padding[565];
 } __attribute__ ((__packed__));
 
 #define BTRFS_FREE_SPACE_EXTENT	1
 #define BTRFS_FREE_SPACE_BITMAP	2
 
 struct btrfs_free_space_entry {
 	__le64 offset;
 	__le64 bytes;
 	__u8 type;
 } __attribute__ ((__packed__));
 
 struct btrfs_free_space_header {
 	struct btrfs_disk_key location;
 	__le64 generation;
 	__le64 num_entries;
 	__le64 num_bitmaps;
 } __attribute__ ((__packed__));
 
 struct btrfs_raid_stride {
 	/* The id of device this raid extent lives on. */
 	__le64 devid;
 	/* The physical location on disk. */
 	__le64 physical;
 } __attribute__ ((__packed__));
 
 struct btrfs_stripe_extent {
 	/* An array of raid strides this stripe is composed of. */
 	__DECLARE_FLEX_ARRAY(struct btrfs_raid_stride, strides);
 } __attribute__ ((__packed__));
 
 #define BTRFS_HEADER_FLAG_WRITTEN	(1ULL << 0)
 #define BTRFS_HEADER_FLAG_RELOC		(1ULL << 1)
 
 /* Super block flags */
 /* Errors detected */
 #define BTRFS_SUPER_FLAG_ERROR		(1ULL << 2)
 
 #define BTRFS_SUPER_FLAG_SEEDING	(1ULL << 32)
 #define BTRFS_SUPER_FLAG_METADUMP	(1ULL << 33)
 #define BTRFS_SUPER_FLAG_METADUMP_V2	(1ULL << 34)
 #define BTRFS_SUPER_FLAG_CHANGING_FSID	(1ULL << 35)
 #define BTRFS_SUPER_FLAG_CHANGING_FSID_V2 (1ULL << 36)
 
 /*
  * Those are temporaray flags utilized by btrfs-progs to do offline conversion.
  * They are rejected by kernel.
  * But still keep them all here to avoid conflicts.
  */
 #define BTRFS_SUPER_FLAG_CHANGING_BG_TREE	(1ULL << 38)
 #define BTRFS_SUPER_FLAG_CHANGING_DATA_CSUM	(1ULL << 39)
 #define BTRFS_SUPER_FLAG_CHANGING_META_CSUM	(1ULL << 40)
 
 /*
  * items in the extent btree are used to record the objectid of the
  * owner of the block and the number of references
  */
 
 struct btrfs_extent_item {
 	__le64 refs;
 	__le64 generation;
 	__le64 flags;
 } __attribute__ ((__packed__));
 
 struct btrfs_extent_item_v0 {
 	__le32 refs;
 } __attribute__ ((__packed__));
 
 
 #define BTRFS_EXTENT_FLAG_DATA		(1ULL << 0)
 #define BTRFS_EXTENT_FLAG_TREE_BLOCK	(1ULL << 1)
 
 /* following flags only apply to tree blocks */
 
 /* use full backrefs for extent pointers in the block */
 #define BTRFS_BLOCK_FLAG_FULL_BACKREF	(1ULL << 8)
 
 #define BTRFS_BACKREF_REV_MAX		256
 #define BTRFS_BACKREF_REV_SHIFT		56
 #define BTRFS_BACKREF_REV_MASK		(((u64)BTRFS_BACKREF_REV_MAX - 1) << \
 					 BTRFS_BACKREF_REV_SHIFT)
 
 #define BTRFS_OLD_BACKREF_REV		0
 #define BTRFS_MIXED_BACKREF_REV		1
 
 /*
  * this flag is only used internally by scrub and may be changed at any time
  * it is only declared here to avoid collisions
  */
 #define BTRFS_EXTENT_FLAG_SUPER		(1ULL << 48)
 
 struct btrfs_tree_block_info {
 	struct btrfs_disk_key key;
 	__u8 level;
 } __attribute__ ((__packed__));
 
 struct btrfs_extent_data_ref {
 	__le64 root;
 	__le64 objectid;
 	__le64 offset;
 	__le32 count;
 } __attribute__ ((__packed__));
 
 struct btrfs_shared_data_ref {
 	__le32 count;
 } __attribute__ ((__packed__));
 
 struct btrfs_extent_owner_ref {
 	__le64 root_id;
 } __attribute__ ((__packed__));
 
 struct btrfs_extent_inline_ref {
 	__u8 type;
 	__le64 offset;
 } __attribute__ ((__packed__));
 
 /* dev extents record free space on individual devices.  The owner
  * field points back to the chunk allocation mapping tree that allocated
  * the extent.  The chunk tree uuid field is a way to double check the owner
  */
 struct btrfs_dev_extent {
 	__le64 chunk_tree;
 	__le64 chunk_objectid;
 	__le64 chunk_offset;
 	__le64 length;
 	__u8 chunk_tree_uuid[BTRFS_UUID_SIZE];
 } __attribute__ ((__packed__));
 
 struct btrfs_inode_ref {
 	__le64 index;
 	__le16 name_len;
 	/* name goes here */
 } __attribute__ ((__packed__));
 
 struct btrfs_inode_extref {
 	__le64 parent_objectid;
 	__le64 index;
 	__le16 name_len;
 	__u8   name[];
 	/* name goes here */
 } __attribute__ ((__packed__));
 
 struct btrfs_timespec {
 	__le64 sec;
 	__le32 nsec;
 } __attribute__ ((__packed__));
 
 struct btrfs_inode_item {
 	/* nfs style generation number */
 	__le64 generation;
 	/* transid that last touched this inode */
 	__le64 transid;
 	__le64 size;
 	__le64 nbytes;
 	__le64 block_group;
 	__le32 nlink;
 	__le32 uid;
 	__le32 gid;
 	__le32 mode;
 	__le64 rdev;
 	__le64 flags;
 
 	/* modification sequence number for NFS */
 	__le64 sequence;
 
 	/*
 	 * a little future expansion, for more than this we can
 	 * just grow the inode item and version it
 	 */
 	__le64 reserved[4];
 	struct btrfs_timespec atime;
 	struct btrfs_timespec ctime;
 	struct btrfs_timespec mtime;
 	struct btrfs_timespec otime;
 } __attribute__ ((__packed__));
 
 struct btrfs_dir_log_item {
 	__le64 end;
 } __attribute__ ((__packed__));
 
 struct btrfs_dir_item {
 	struct btrfs_disk_key location;
 	__le64 transid;
 	__le16 data_len;
 	__le16 name_len;
 	__u8 type;
 } __attribute__ ((__packed__));
 
 #define BTRFS_ROOT_SUBVOL_RDONLY	(1ULL << 0)
 
 /*
  * Internal in-memory flag that a subvolume has been marked for deletion but
  * still visible as a directory
  */
 #define BTRFS_ROOT_SUBVOL_DEAD		(1ULL << 48)
 
 struct btrfs_root_item {
 	struct btrfs_inode_item inode;
 	__le64 generation;
 	__le64 root_dirid;
 	__le64 bytenr;
 	__le64 byte_limit;
 	__le64 bytes_used;
 	__le64 last_snapshot;
 	__le64 flags;
 	__le32 refs;
 	struct btrfs_disk_key drop_progress;
 	__u8 drop_level;
 	__u8 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.
 	 */
 	__le64 generation_v2;
 	__u8 uuid[BTRFS_UUID_SIZE];
 	__u8 parent_uuid[BTRFS_UUID_SIZE];
 	__u8 received_uuid[BTRFS_UUID_SIZE];
 	__le64 ctransid; /* updated when an inode changes */
 	__le64 otransid; /* trans when created */
 	__le64 stransid; /* trans when sent. non-zero for received subvol */
 	__le64 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;
 	__le64 reserved[8]; /* for future */
 } __attribute__ ((__packed__));
 
 /*
  * Btrfs root item used to be smaller than current size.  The old format ends
  * at where member generation_v2 is.
  */
 static __inline__ __u32 btrfs_legacy_root_item_size(void)
 {
 	return offsetof(struct btrfs_root_item, generation_v2);
 }
 
 /*
  * this is used for both forward and backward root refs
  */
 struct btrfs_root_ref {
 	__le64 dirid;
 	__le64 sequence;
 	__le16 name_len;
 } __attribute__ ((__packed__));
 
 struct btrfs_disk_balance_args {
 	/*
 	 * profiles to operate on, single is denoted by
 	 * BTRFS_AVAIL_ALLOC_BIT_SINGLE
 	 */
 	__le64 profiles;
 
 	/*
 	 * usage filter
 	 * BTRFS_BALANCE_ARGS_USAGE with a single value means '0..N'
 	 * BTRFS_BALANCE_ARGS_USAGE_RANGE - range syntax, min..max
 	 */
 	union {
 		__le64 usage;
 		struct {
 			__le32 usage_min;
 			__le32 usage_max;
 		};
 	};
 
 	/* devid filter */
 	__le64 devid;
 
 	/* devid subset filter [pstart..pend) */
 	__le64 pstart;
 	__le64 pend;
 
 	/* btrfs virtual address space subset filter [vstart..vend) */
 	__le64 vstart;
 	__le64 vend;
 
 	/*
 	 * profile to convert to, single is denoted by
 	 * BTRFS_AVAIL_ALLOC_BIT_SINGLE
 	 */
 	__le64 target;
 
 	/* BTRFS_BALANCE_ARGS_* */
 	__le64 flags;
 
 	/*
 	 * BTRFS_BALANCE_ARGS_LIMIT with value 'limit'
 	 * BTRFS_BALANCE_ARGS_LIMIT_RANGE - the extend version can use minimum
 	 * and maximum
 	 */
 	union {
 		__le64 limit;
 		struct {
 			__le32 limit_min;
 			__le32 limit_max;
 		};
 	};
 
 	/*
 	 * Process chunks that cross stripes_min..stripes_max devices,
 	 * BTRFS_BALANCE_ARGS_STRIPES_RANGE
 	 */
 	__le32 stripes_min;
 	__le32 stripes_max;
 
 	__le64 unused[6];
 } __attribute__ ((__packed__));
 
 /*
  * store balance parameters to disk so that balance can be properly
  * resumed after crash or unmount
  */
 struct btrfs_balance_item {
 	/* BTRFS_BALANCE_* */
 	__le64 flags;
 
 	struct btrfs_disk_balance_args data;
 	struct btrfs_disk_balance_args meta;
 	struct btrfs_disk_balance_args sys;
 
 	__le64 unused[4];
 } __attribute__ ((__packed__));
 
 enum {
 	BTRFS_FILE_EXTENT_INLINE   = 0,
 	BTRFS_FILE_EXTENT_REG      = 1,
 	BTRFS_FILE_EXTENT_PREALLOC = 2,
 	BTRFS_NR_FILE_EXTENT_TYPES = 3,
 };
 
 struct btrfs_file_extent_item {
 	/*
 	 * transaction id that created this extent
 	 */
 	__le64 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.
 	 */
 	__le64 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.
 	 */
 	__u8 compression;
 	__u8 encryption;
 	__le16 other_encoding; /* spare for later use */
 
 	/* are we __inline__ data or a real extent? */
 	__u8 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.
 	 */
 	__le64 disk_bytenr;
 	__le64 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
 	 */
 	__le64 offset;
 	/*
 	 * the logical number of file blocks (no csums included).  This
 	 * always reflects the size uncompressed and without encoding.
 	 */
 	__le64 num_bytes;
 
 } __attribute__ ((__packed__));
 
 struct btrfs_csum_item {
 	__u8 csum;
 } __attribute__ ((__packed__));
 
 struct btrfs_dev_stats_item {
 	/*
 	 * grow this item struct at the end for future enhancements and keep
 	 * the existing values unchanged
 	 */
 	__le64 values[BTRFS_DEV_STAT_VALUES_MAX];
 } __attribute__ ((__packed__));
 
 #define BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS	0
 #define BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_AVOID	1
 
 struct btrfs_dev_replace_item {
 	/*
 	 * grow this item struct at the end for future enhancements and keep
 	 * the existing values unchanged
 	 */
 	__le64 src_devid;
 	__le64 cursor_left;
 	__le64 cursor_right;
 	__le64 cont_reading_from_srcdev_mode;
 
 	__le64 replace_state;
 	__le64 time_started;
 	__le64 time_stopped;
 	__le64 num_write_errors;
 	__le64 num_uncorrectable_read_errors;
 } __attribute__ ((__packed__));
 
 /* different types of block groups (and chunks) */
 #define BTRFS_BLOCK_GROUP_DATA		(1ULL << 0)
 #define BTRFS_BLOCK_GROUP_SYSTEM	(1ULL << 1)
 #define BTRFS_BLOCK_GROUP_METADATA	(1ULL << 2)
 #define BTRFS_BLOCK_GROUP_RAID0		(1ULL << 3)
 #define BTRFS_BLOCK_GROUP_RAID1		(1ULL << 4)
 #define BTRFS_BLOCK_GROUP_DUP		(1ULL << 5)
 #define BTRFS_BLOCK_GROUP_RAID10	(1ULL << 6)
 #define BTRFS_BLOCK_GROUP_RAID5         (1ULL << 7)
 #define BTRFS_BLOCK_GROUP_RAID6         (1ULL << 8)
 #define BTRFS_BLOCK_GROUP_RAID1C3       (1ULL << 9)
 #define BTRFS_BLOCK_GROUP_RAID1C4       (1ULL << 10)
 #define BTRFS_BLOCK_GROUP_RESERVED	(BTRFS_AVAIL_ALLOC_BIT_SINGLE | \
 					 BTRFS_SPACE_INFO_GLOBAL_RSV)
 
 #define BTRFS_BLOCK_GROUP_TYPE_MASK	(BTRFS_BLOCK_GROUP_DATA |    \
 					 BTRFS_BLOCK_GROUP_SYSTEM |  \
 					 BTRFS_BLOCK_GROUP_METADATA)
 
 #define BTRFS_BLOCK_GROUP_PROFILE_MASK	(BTRFS_BLOCK_GROUP_RAID0 |   \
 					 BTRFS_BLOCK_GROUP_RAID1 |   \
 					 BTRFS_BLOCK_GROUP_RAID1C3 | \
 					 BTRFS_BLOCK_GROUP_RAID1C4 | \
 					 BTRFS_BLOCK_GROUP_RAID5 |   \
 					 BTRFS_BLOCK_GROUP_RAID6 |   \
 					 BTRFS_BLOCK_GROUP_DUP |     \
 					 BTRFS_BLOCK_GROUP_RAID10)
 #define BTRFS_BLOCK_GROUP_RAID56_MASK	(BTRFS_BLOCK_GROUP_RAID5 |   \
 					 BTRFS_BLOCK_GROUP_RAID6)
 
 #define BTRFS_BLOCK_GROUP_RAID1_MASK	(BTRFS_BLOCK_GROUP_RAID1 |   \
 					 BTRFS_BLOCK_GROUP_RAID1C3 | \
 					 BTRFS_BLOCK_GROUP_RAID1C4)
 
 /*
  * We need a bit for restriper to be able to tell when chunks of type
  * SINGLE are available.  This "extended" profile format is used in
  * fs_info->avail_*_alloc_bits (in-memory) and balance item fields
  * (on-disk).  The corresponding on-disk bit in chunk.type is reserved
  * to avoid remappings between two formats in future.
  */
 #define BTRFS_AVAIL_ALLOC_BIT_SINGLE	(1ULL << 48)
 
 /*
  * A fake block group type that is used to communicate global block reserve
  * size to userspace via the SPACE_INFO ioctl.
  */
 #define BTRFS_SPACE_INFO_GLOBAL_RSV	(1ULL << 49)
 
 #define BTRFS_EXTENDED_PROFILE_MASK	(BTRFS_BLOCK_GROUP_PROFILE_MASK | \
 					 BTRFS_AVAIL_ALLOC_BIT_SINGLE)
 
 static __inline__ __u64 chunk_to_extended(__u64 flags)
 {
 	if ((flags & BTRFS_BLOCK_GROUP_PROFILE_MASK) == 0)
 		flags |= BTRFS_AVAIL_ALLOC_BIT_SINGLE;
 
 	return flags;
 }
 static __inline__ __u64 extended_to_chunk(__u64 flags)
 {
 	return flags & ~BTRFS_AVAIL_ALLOC_BIT_SINGLE;
 }
 
 struct btrfs_block_group_item {
 	__le64 used;
 	__le64 chunk_objectid;
 	__le64 flags;
 } __attribute__ ((__packed__));
 
 struct btrfs_free_space_info {
 	__le32 extent_count;
 	__le32 flags;
 } __attribute__ ((__packed__));
 
 #define BTRFS_FREE_SPACE_USING_BITMAPS (1ULL << 0)
 
 #define BTRFS_QGROUP_LEVEL_SHIFT		48
 static __inline__ __u16 btrfs_qgroup_level(__u64 qgroupid)
 {
 	return (__u16)(qgroupid >> BTRFS_QGROUP_LEVEL_SHIFT);
 }
 
 /*
  * is subvolume quota turned on?
  */
 #define BTRFS_QGROUP_STATUS_FLAG_ON		(1ULL << 0)
 /*
  * RESCAN is set during the initialization phase
  */
 #define BTRFS_QGROUP_STATUS_FLAG_RESCAN		(1ULL << 1)
 /*
  * Some qgroup entries are known to be out of date,
  * either because the configuration has changed in a way that
  * makes a rescan necessary, or because the fs has been mounted
  * with a non-qgroup-aware version.
  * Turning qouta off and on again makes it inconsistent, too.
  */
 #define BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT	(1ULL << 2)
 
 /*
  * Whether or not this filesystem is using simple quotas.  Not exactly the
  * incompat bit, because we support using simple quotas, disabling it, then
  * going back to full qgroup quotas.
  */
 #define BTRFS_QGROUP_STATUS_FLAG_SIMPLE_MODE	(1ULL << 3)
 
 #define BTRFS_QGROUP_STATUS_FLAGS_MASK	(BTRFS_QGROUP_STATUS_FLAG_ON |		\
 					 BTRFS_QGROUP_STATUS_FLAG_RESCAN |	\
 					 BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT | \
 					 BTRFS_QGROUP_STATUS_FLAG_SIMPLE_MODE)
 
 #define BTRFS_QGROUP_STATUS_VERSION        1
 
 struct btrfs_qgroup_status_item {
 	__le64 version;
 	/*
 	 * the generation is updated during every commit. As older
 	 * versions of btrfs are not aware of qgroups, it will be
 	 * possible to detect inconsistencies by checking the
 	 * generation on mount time
 	 */
 	__le64 generation;
 
 	/* flag definitions see above */
 	__le64 flags;
 
 	/*
 	 * only used during scanning to record the progress
 	 * of the scan. It contains a logical address
 	 */
 	__le64 rescan;
 
 	/*
 	 * The generation when quotas were last enabled. Used by simple quotas to
 	 * avoid decrementing when freeing an extent that was written before
 	 * enable.
 	 *
 	 * Set only if flags contain BTRFS_QGROUP_STATUS_FLAG_SIMPLE_MODE.
 	 */
 	__le64 enable_gen;
 } __attribute__ ((__packed__));
 
 struct btrfs_qgroup_info_item {
 	__le64 generation;
 	__le64 rfer;
 	__le64 rfer_cmpr;
 	__le64 excl;
 	__le64 excl_cmpr;
 } __attribute__ ((__packed__));
 
 struct btrfs_qgroup_limit_item {
 	/*
 	 * only updated when any of the other values change
 	 */
 	__le64 flags;
 	__le64 max_rfer;
 	__le64 max_excl;
 	__le64 rsv_rfer;
 	__le64 rsv_excl;
 } __attribute__ ((__packed__));
 
 struct btrfs_verity_descriptor_item {
 	/* Size of the verity descriptor in bytes */
 	__le64 size;
 	/*
 	 * When we implement support for fscrypt, we will need to encrypt the
 	 * Merkle tree for encrypted verity files. These 128 bits are for the
 	 * eventual storage of an fscrypt initialization vector.
 	 */
 	__le64 reserved[2];
 	__u8 encryption;
 } __attribute__ ((__packed__));
 
 #endif /* _BTRFS_CTREE_H_ */