From: Darrick J. Wong <darrick.wong@xxxxxxxxxx> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --- .../xfs-data-structures/common_types.rst | 61 ++++ .../filesystems/xfs-data-structures/magic.rst | 277 ++++++++++++++++++++ .../filesystems/xfs-data-structures/overview.rst | 2 3 files changed, 340 insertions(+) create mode 100644 Documentation/filesystems/xfs-data-structures/common_types.rst create mode 100644 Documentation/filesystems/xfs-data-structures/magic.rst diff --git a/Documentation/filesystems/xfs-data-structures/common_types.rst b/Documentation/filesystems/xfs-data-structures/common_types.rst new file mode 100644 index 000000000000..63de847924c6 --- /dev/null +++ b/Documentation/filesystems/xfs-data-structures/common_types.rst @@ -0,0 +1,61 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +Common XFS Types +---------------- + +All the following XFS types can be found in xfs\_types.h. NULL values are +always -1 on disk (ie. all bits for the value set to one). + +**xfs\_ino\_t** + Unsigned 64 bit absolute `inode number <#inode-numbers>`__. + +**xfs\_off\_t** + Signed 64 bit file offset. + +**xfs\_daddr\_t** + Signed 64 bit disk address (sectors). + +**xfs\_agnumber\_t** + Unsigned 32 bit `AG number <#allocation-groups>`__. + +**xfs\_agblock\_t** + Unsigned 32 bit AG relative block number. + +**xfs\_extlen\_t** + Unsigned 32 bit `extent <#data-extents>`__ length in blocks. + +**xfs\_extnum\_t** + Signed 32 bit number of extents in a data fork. + +**xfs\_aextnum\_t** + Signed 16 bit number of extents in an attribute fork. + +**xfs\_dablk\_t** + Unsigned 32 bit block number for `directories <#directories>`__ and + `extended attributes <#extended-attributes>`__. + +**xfs\_dahash\_t** + Unsigned 32 bit hash of a directory file name or extended attribute name. + +**xfs\_fsblock\_t** + Unsigned 64 bit filesystem block number combining `AG + number <#allocation-groups>`__ and block offset into the AG. + +**xfs\_rfsblock\_t** + Unsigned 64 bit raw filesystem block number. + +**xfs\_rtblock\_t** + Unsigned 64 bit extent number in the `real-time <#real-time-devices>`__ + sub-volume. + +**xfs\_fileoff\_t** + Unsigned 64 bit block offset into a file. + +**xfs\_filblks\_t** + Unsigned 64 bit block count for a file. + +**uuid\_t** + 16-byte universally unique identifier (UUID). + +**xfs\_fsize\_t** + Signed 64 bit byte size of a file. diff --git a/Documentation/filesystems/xfs-data-structures/magic.rst b/Documentation/filesystems/xfs-data-structures/magic.rst new file mode 100644 index 000000000000..f5e57581645d --- /dev/null +++ b/Documentation/filesystems/xfs-data-structures/magic.rst @@ -0,0 +1,277 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +Magic Numbers +------------- + +These are the magic numbers that are known to XFS, along with links to the +relevant chapters. Magic numbers tend to have consistent locations: + +- 32-bit magic numbers are always at offset zero in the block. + +- 16-bit magic numbers for the directory and attribute B+tree are at offset + eight. + +- The quota magic number is at offset zero. + +- The inode magic is at the beginning of each inode. + +.. list-table:: + :widths: 28 12 8 34 + :header-rows: 1 + + * - Flag + - Hexadecimal + - ASCII + - Data structure + * - XFS_SB_MAGIC + - 0x58465342 + - XFSB + - `Superblock <#superblocks>`__ + * - XFS_AGF_MAGIC + - 0x58414746 + - XAGF + - `Free Space <#ag-free-space-block>`__ + * - XFS_AGI_MAGIC + - 0x58414749 + - XAGI + - `Inode Information <#inode-information>`__ + * - XFS_AGFL_MAGIC + - 0x5841464c + - XAFL + - `Free Space List <#ag-free-list>`__, v5 only + * - XFS_DINODE_MAGIC + - 0x494e + - IN + - `Inodes <#inode-core>`__ + * - XFS_DQUOT_MAGIC + - 0x4451 + - DQ + - `Quota Inodes <#quota-inodes>`__ + * - XFS_SYMLINK_MAGIC + - 0x58534c4d + - XSLM + - `Symbolic Links <#extent-symbolic-links>`__ + * - XFS_ABTB_MAGIC + - 0x41425442 + - ABTB + - `Free Space by Block B+tree <#ag-free-space-b-trees>`__ + * - XFS_ABTB_CRC_MAGIC + - 0x41423342 + - AB3B + - `Free Space by Block B+tree <#ag-free-space-b-trees>`__, v5 only + * - XFS_ABTC_MAGIC + - 0x41425443 + - ABTC + - `Free Space by Size B+tree <#ag-free-space-b-trees>`__ + * - XFS_ABTC_CRC_MAGIC + - 0x41423343 + - AB3C + - `Free Space by Size B+tree <#ag-free-space-b-trees>`__, v5 only + * - XFS_IBT_MAGIC + - 0x49414254 + - IABT + - `Inode B+tree <#inode-b-trees>`__ + * - XFS_IBT_CRC_MAGIC + - 0x49414233 + - IAB3 + - `Inode B+tree <#inode-b-trees>`__, v5 only + * - XFS_FIBT_MAGIC + - 0x46494254 + - FIBT + - `Free Inode B+tree <#inode-b-trees>`__ + * - XFS_FIBT_CRC_MAGIC + - 0x46494233 + - FIB3 + - `Free Inode B+tree <#inode-b-trees>`__, v5 only + * - XFS_BMAP_MAGIC + - 0x424d4150 + - BMAP + - `B+Tree Extent List <#b-tree-extent-list>`__ + * - XFS_BMAP_CRC_MAGIC + - 0x424d4133 + - BMA3 + - `B+Tree Extent List <#b-tree-extent-list>`__, v5 only + * - XLOG_HEADER_MAGIC_NUM + - 0xfeedbabe + - + - `Log Records <#log-records>`__ + * - XFS_DA_NODE_MAGIC + - 0xfebe + - + - `Directory/Attribute Node <#directory-attribute-internal-node>`__ + * - XFS_DA3_NODE_MAGIC + - 0x3ebe + - + - `Directory/Attribute Node <#directory-attribute-internal-node>`__, v5 only + * - XFS_DIR2_BLOCK_MAGIC + - 0x58443242 + - XD2B + - `Block Directory Data <#block-directories>`__ + * - XFS_DIR3_BLOCK_MAGIC + - 0x58444233 + - XDB3 + - `Block Directory Data <#block-directories>`__, v5 only + * - XFS_DIR2_DATA_MAGIC + - 0x58443244 + - XD2D + - `Leaf Directory Data <#leaf-directories>`__ + * - XFS_DIR3_DATA_MAGIC + - 0x58444433 + - XDD3 + - `Leaf Directory Data <#leaf-directories>`__, v5 only + * - XFS_DIR2_LEAF1_MAGIC + - 0xd2f1 + - + - `Leaf Directory <#leaf-directories>`__ + * - XFS_DIR3_LEAF1_MAGIC + - 0x3df1 + - + - `Leaf Directory <#leaf-directories>`__, v5 only + * - XFS_DIR2_LEAFN_MAGIC + - 0xd2ff + - + - `Node Directory <#node-directories>`__ + * - XFS_DIR3_LEAFN_MAGIC + - 0x3dff + - + - `Node Directory <#node-directories>`__, v5 only + * - XFS_DIR2_FREE_MAGIC + - 0x58443246 + - XD2F + - `Node Directory Free Space <#node-directories>`__ + * - XFS_DIR3_FREE_MAGIC + - 0x58444633 + - XDF3 + - `Node Directory Free Space <#node-directories>`__, v5 only + * - XFS_ATTR_LEAF_MAGIC + - 0xfbee + - + - `Leaf Attribute <#leaf-attributes>`__ + * - XFS_ATTR3_LEAF_MAGIC + - 0x3bee + - + - `Leaf Attribute <#leaf-attributes>`__, v5 only + * - XFS_ATTR3_RMT_MAGIC + - 0x5841524d + - XARM + - `Remote Attribute Value <#remote-attribute-values>`__, v5 only + * - XFS_RMAP_CRC_MAGIC + - 0x524d4233 + - RMB3 + - `Reverse Mapping B+tree <#reverse-mapping-b-tree>`__, v5 only + * - XFS_RTRMAP_CRC_MAGIC + - 0x4d415052 + - MAPR + - `Real-Time Reverse Mapping B+tree <#real-time-reverse-mapping-b-tree>`__, v5 only + * - XFS_REFC_CRC_MAGIC + - 0x52334643 + - R3FC + - `Reference Count B+tree <#reference-count-b-tree>`__, v5 only + * - XFS_MD_MAGIC + - 0x5846534d + - XFSM + - `Metadata Dumps <#metadata-dumps>`__ + +The magic numbers for log items are at offset zero in each log item, but items +are not aligned to blocks. + +.. list-table:: + :widths: 24 12 8 36 + :header-rows: 1 + + * - Flag + - Hexadecimal + - ASCII + - Data structure + * - XFS_TRANS_HEADER_MAGIC + - 0x5452414e + - TRAN + - `Log Transactions <#transaction-headers>`__ + * - XFS_LI_EFI + - 0x1236 + - + - `Extent Freeing Intent Log Item <#intent-to-free-an-extent>`__ + * - XFS_LI_EFD + - 0x1237 + - + - `Extent Freeing Done Log Item <#completion-of-intent-to-free-an-extent>`__ + * - XFS_LI_IUNLINK + - 0x1238 + - + - Unknown? + * - XFS_LI_INODE + - 0x123b + - + - `Inode Updates Log Item <#inode-updates>`__ + * - XFS_LI_BUF + - 0x123c + - + - `Buffer Writes Log Item <#buffer-log-item>`__ + * - XFS_LI_DQUOT + - 0x123d + - + - `Update Quota Log Item <#quota-update-data-log-item>`__ + * - XFS_LI_QUOTAOFF + - 0x123e + - + - `Quota Off Log Item <#disable-quota-log-item>`__ + * - XFS_LI_ICREATE + - 0x123f + - + - `Inode Creation Log Item <#inode-creation-log-item>`__ + * - XFS_LI_RUI + - 0x1240 + - + - `Reverse Mapping Update Intent <#reverse-mapping-updates-intent>`__ + * - XFS_LI_RUD + - 0x1241 + - + - `Reverse Mapping Update Done <#completion-of-reverse-mapping-updates>`__ + * - XFS_LI_CUI + - 0x1242 + - + - `Reference Count Update Intent <#reference-count-updates-intent>`__ + * - XFS_LI_CUD + - 0x1243 + - + - `Reference Count Update Done <#completion-of-reference-count-updates>`__ + * - XFS_LI_BUI + - 0x1244 + - + - `File Block Mapping Update Intent <#file-block-mapping-intent>`__ + * - XFS_LI_BUD + - 0x1245 + - + - `File Block Mapping Update Done <#completion-of-file-block-mapping-updates>`__ + +Theoretical Limits +------------------ + +XFS can create really big filesystems! + ++---------------------+---------------------+---------------------+---------------------+ +| Item | 1KiB blocks | 4KiB blocks | 64KiB blocks | ++=====================+=====================+=====================+=====================+ +| Blocks | 2\ :sup:`52` | 2\ :sup:`52` | 2\ :sup:`52` | ++---------------------+---------------------+---------------------+---------------------+ +| Inodes | 2\ :sup:`63` | 2\ :sup:`63` | 2\ :sup:`64` | ++---------------------+---------------------+---------------------+---------------------+ +| Allocation Groups | 2\ :sup:`32` | 2\ :sup:`32` | 2\ :sup:`32` | ++---------------------+---------------------+---------------------+---------------------+ +| File System Size | 8EiB | 8EiB | 8EiB | ++---------------------+---------------------+---------------------+---------------------+ +| Blocks per AG | 2\ :sup:`31` | 2\ :sup:`31` | 2\ :sup:`31` | ++---------------------+---------------------+---------------------+---------------------+ +| Inodes per AG | 2\ :sup:`32` | 2\ :sup:`32` | 2\ :sup:`32` | ++---------------------+---------------------+---------------------+---------------------+ +| Max AG Size | 2TiB | 8TiB | 128TiB | ++---------------------+---------------------+---------------------+---------------------+ +| Blocks Per File | 2\ :sup:`54` | 2\ :sup:`54` | 2\ :sup:`54` | ++---------------------+---------------------+---------------------+---------------------+ +| File Size | 8EiB | 8EiB | 8EiB | ++---------------------+---------------------+---------------------+---------------------+ +| Max Dir Size | 32GiB | 32GiB | 32GiB | ++---------------------+---------------------+---------------------+---------------------+ + +Linux doesn’t suppport files or devices larger than 8EiB, so the block +limitations are largely ignorable. diff --git a/Documentation/filesystems/xfs-data-structures/overview.rst b/Documentation/filesystems/xfs-data-structures/overview.rst index b1b3f711638b..23eb71d65c93 100644 --- a/Documentation/filesystems/xfs-data-structures/overview.rst +++ b/Documentation/filesystems/xfs-data-structures/overview.rst @@ -47,3 +47,5 @@ latency. .. include:: delayed_logging.rst .. include:: reflink.rst .. include:: reconstruction.rst +.. include:: common_types.rst +.. include:: magic.rst
