path: root/include/uapi/linux/btrfs_tree.h

/* 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>
#ifdef __KERNEL__
#include <linux/stddef.h>
#else
#include <stddef.h>
#endif

/* 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 permane