Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --- design/XFS_Filesystem_Structure/docinfo.xml | 1 design/XFS_Filesystem_Structure/magic.asciidoc | 86 ++++++++++++++++++++ .../xfs_filesystem_structure.asciidoc | 2 3 files changed, 89 insertions(+) create mode 100644 design/XFS_Filesystem_Structure/magic.asciidoc diff --git a/design/XFS_Filesystem_Structure/docinfo.xml b/design/XFS_Filesystem_Structure/docinfo.xml index 8ed38d9..6189fd6 100644 --- a/design/XFS_Filesystem_Structure/docinfo.xml +++ b/design/XFS_Filesystem_Structure/docinfo.xml @@ -103,6 +103,7 @@ <member>Add v5 fields.</member> <member>Discuss metadata integrity.</member> <member>Document the free inode B+tree.</member> + <member>Create an index of magic numbers.</member> </simplelist> </revdescription> </revision> diff --git a/design/XFS_Filesystem_Structure/magic.asciidoc b/design/XFS_Filesystem_Structure/magic.asciidoc new file mode 100644 index 0000000..301cfa0 --- /dev/null +++ b/design/XFS_Filesystem_Structure/magic.asciidoc @@ -0,0 +1,86 @@ += 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. + +[options="header"] +|===== +| Flag | Hexadecimal | ASCII | Data structure +| +XFS_SB_MAGIC+ | 0x58465342 | XFSB | xref:Superblocks[Superblock] +| +XFS_AGF_MAGIC+ | 0x58414746 | XAGF | xref:AG_Free_Space_Block[Free Space] +| +XFS_AGI_MAGIC+ | 0x58414749 | XAGI | xref:Inode_Information[Inode Information] +| +XFS_AGFL_MAGIC+ | 0x5841464c | XAFL | xref:AG_Free_List[Free Space List], v5 only +| +XFS_DINODE_MAGIC+ | 0x494e | IN | xref:Inode_Core[Inodes] +| +XFS_DQUOT_MAGIC+ | 0x4451 | DQ | xref:Quota_Inodes[Quota Inodes] +| +XFS_SYMLINK_MAGIC+ | 0x58534c4d | XSLM | xref:Extent_Symbolic_Links[Symbolic Links] +| +XFS_ABTB_MAGIC+ | 0x41425442 | ABTB | xref:AG_Free_Space_Btrees[Free Space by Block B+tree] +| +XFS_ABTB_CRC_MAGIC+ | 0x41423342 | AB3B | xref:AG_Free_Space_Btrees[Free Space by Block B+tree], v5 only +| +XFS_ABTC_MAGIC+ | 0x41425443 | ABTC | xref:AG_Free_Space_Btrees[Free Space by Size B+tree] +| +XFS_ABTC_CRC_MAGIC+ | 0x41423343 | AB3C | xref:AG_Free_Space_Btrees[Free Space by Size B+tree], v5 only +| +XFS_IBT_MAGIC+ | 0x49414254 | IABT | xref:Inode_Btrees[Inode B+tree] +| +XFS_IBT_CRC_MAGIC+ | 0x49414233 | IAB3 | xref:Inode_Btrees[Inode B+tree], v5 only +| +XFS_FIBT_MAGIC+ | 0x46494254 | FIBT | xref:Inode_Btrees[Free Inode B+tree] +| +XFS_FIBT_CRC_MAGIC+ | 0x46494233 | FIB3 | xref:Inode_Btrees[Free Inode B+tree], v5 only +| +XFS_BMAP_MAGIC+ | 0x424d4150 | BMAP | xref:Btree_Extent_List[B+Tree Extent List] +| +XFS_BMAP_CRC_MAGIC+ | 0x424d4133 | BMA3 | xref:Btree_Extent_List[B+Tree Extent List], v5 only +| +XLOG_HEADER_MAGIC_NUM+ | 0xfeedbabe | | xref:Log_Records[Log Records] +| +XFS_DA_NODE_MAGIC+ | 0xfebe | | xref:Directory_Attribute_Internal_Node[Directory/Attribute Node] +| +XFS_DA3_NODE_MAGIC+ | 0x3ebe | | xref:Directory_Attribute_Internal_Node[Directory/Attribute Node], v5 only +| +XFS_DIR2_BLOCK_MAGIC+ | 0x58443242 | XD2B | xref:Block_Directories[Block Directory Data] +| +XFS_DIR3_BLOCK_MAGIC+ | 0x58444233 | XDB3 | xref:Block_Directories[Block Directory Data], v5 only +| +XFS_DIR2_DATA_MAGIC+ | 0x58443244 | XD2D | xref:Leaf_Directories[Leaf Directory Data] +| +XFS_DIR3_DATA_MAGIC+ | 0x58444433 | XDD3 | xref:Leaf_Directories[Leaf Directory Data], v5 only +| +XFS_DIR2_LEAF1_MAGIC+ | 0xd2f1 | | xref:Leaf_Directories[Leaf Directory] +| +XFS_DIR3_LEAF1_MAGIC+ | 0x3df1 | | xref:Leaf_Directories[Leaf Directory], v5 only +| +XFS_DIR2_LEAFN_MAGIC+ | 0xd2ff | | xref:Node_Directories[Node Directory] +| +XFS_DIR3_LEAFN_MAGIC+ | 0x3dff | | xref:Node_Directories[Node Directory], v5 only +| +XFS_DIR2_FREE_MAGIC+ | 0x58443246 | XD2F | xref:Node_Directories[Node Directory Free Space] +| +XFS_DIR3_FREE_MAGIC+ | 0x58444633 | XDF3 | xref:Node_Directories[Node Directory Free Space], v5 only +| +XFS_ATTR_LEAF_MAGIC+ | 0xfbee | | xref:Leaf_Attributes[Leaf Attribute] +| +XFS_ATTR3_LEAF_MAGIC+ | 0x3bee | | xref:Leaf_Attributes[Leaf Attribute], v5 only +| +XFS_ATTR3_RMT_MAGIC+ | 0x5841524d | XARM | xref:Remote_Values[Remote Attribute Value], v5 only +|===== + +The magic numbers for log items are at offset zero in each log item, but items +are not aligned to blocks. + +[options="header"] +|===== +| Flag | Hexadecimal | ASCII | Data structure +| +XFS_TRANS_HEADER_MAGIC+ | 0x5452414e | TRAN | xref:Log_Transaction_Headers[Log Transactions] +| +XFS_LI_EFI+ | 0x1236 | | xref:EFI_Log_Item[Extent Freeing Intent Log Item] +| +XFS_LI_EFD+ | 0x1237 | | xref:EFD_Log_Item[Extent Freeing Done Log Item] +| +XFS_LI_IUNLINK+ | 0x1238 | | Unknown? +| +XFS_LI_INODE+ | 0x123b | | xref:Inode_Log_Item[Inode Updates Log Item] +| +XFS_LI_BUF+ | 0x123c | | xref:Buffer_Log_Item[Buffer Writes Log Item] +| +XFS_LI_DQUOT+ | 0x123d | | xref:Quota_Update_Log_Item[Update Quota Log Item] +| +XFS_LI_QUOTAOFF+ | 0x123e | | xref:Quota_Off_Log_Item[Quota Off Log Item] +| +XFS_LI_ICREATE+ | 0x123f | | xref:Inode_Create_Log_Item[Inode Creation Log Item] +|===== + += Theoretical Limits + +XFS can create really big filesystems! + +[options="header"] +|===== +| Item | 1KiB blocks | 4KiB blocks | 64KiB blocks +| Blocks | 2^52^ | 2^52^ | 2^52^ +| Inodes | 2^63^ | 2^63^ | 2^64^ +| Allocation Groups | 2^32^ | 2^32^ | 2^32^ +| File System Size | 8EiB | 8EiB | 8EiB +| Blocks per AG | 2^31^ | 2^31^ | 2^31^ +| Inodes per AG | 2^32^ | 2^32^ | 2^32^ +| Max AG Size | 2TiB | 8TiB | 128TiB +| Blocks Per File | 2^54^ | 2^54^ | 2^54^ +| 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/design/XFS_Filesystem_Structure/xfs_filesystem_structure.asciidoc b/design/XFS_Filesystem_Structure/xfs_filesystem_structure.asciidoc index 8aacbb7..0ab4906 100644 --- a/design/XFS_Filesystem_Structure/xfs_filesystem_structure.asciidoc +++ b/design/XFS_Filesystem_Structure/xfs_filesystem_structure.asciidoc @@ -50,6 +50,8 @@ include::metadata_integrity.asciidoc[] include::common_types.asciidoc[] +include::magic.asciidoc[] + // return titles to normal :leveloffset: 0 _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
