Fix some of the more egregious missing xfs_db examples so that the reader can appreciate what the data structures look like. Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --- .../allocation_groups.asciidoc | 74 ++++++++++++++++++++ .../XFS_Filesystem_Structure/data_extents.asciidoc | 41 +++++++++++ .../XFS_Filesystem_Structure/directories.asciidoc | 55 +++++++++++++++ design/XFS_Filesystem_Structure/docinfo.xml | 1 4 files changed, 168 insertions(+), 3 deletions(-) diff --git a/design/XFS_Filesystem_Structure/allocation_groups.asciidoc b/design/XFS_Filesystem_Structure/allocation_groups.asciidoc index e958039..7d4c11b 100644 --- a/design/XFS_Filesystem_Structure/allocation_groups.asciidoc +++ b/design/XFS_Filesystem_Structure/allocation_groups.asciidoc @@ -831,7 +831,79 @@ image::images/20b.png[] ==== xfs_db AGI Example -TODO + +This is an AGI of a freshly populated filesystem: + +---- +xfs_db> agi 0 +xfs_db> p +magicnum = 0x58414749 +versionnum = 1 +seqno = 0 +length = 825457 +count = 5440 +root = 3 +level = 1 +freecount = 9 +newino = 5792 +dirino = null +unlinked[0-63] = +uuid = 3dfa1e5c-5a5f-4ca2-829a-000e453600fe +lsn = 0x1000032c2 +crc = 0x14cb7e5c (correct) +free_root = 4 +free_level = 1 +---- + +From this example, we see that the inode B+tree is rooted at AG block 3 and +that the free inode B+tree is rooted at AG block 4. Let's look at the +inode B+tree: + +---- +xfs_db> addr root +xfs_db> p +magic = 0x49414233 +level = 0 +numrecs = 85 +leftsib = null +rightsib = null +bno = 24 +lsn = 0x1000032c2 +uuid = 3dfa1e5c-5a5f-4ca2-829a-000e453600fe +owner = 0 +crc = 0x768f9592 (correct) +recs[1-85] = [startino,freecount,free] + 1:[96,0,0] 2:[160,0,0] 3:[224,0,0] 4:[288,0,0] + 5:[352,0,0] 6:[416,0,0] 7:[480,0,0] 8:[544,0,0] + 9:[608,0,0] 10:[672,0,0] 11:[736,0,0] 12:[800,0,0] + ... + 85:[5792,9,0xff80000000000000] +---- + +Most of the inode chunks on this filesystem are totally full, since the +free+ +value is zero. This means that we ought to expect inode 160 to be linked +somewhere in the directory structure. However, notice that 0xff80000000000000 +in record 85 -- this means that we would expect inode 5856 to be free. Moving +on to the free inode B+tree, we see that this is indeed the case: + +---- +xfs_db> addr free_root +xfs_db> p +magic = 0x46494233 +level = 0 +numrecs = 1 +leftsib = null +rightsib = null +bno = 32 +lsn = 0x1000032c2 +uuid = 3dfa1e5c-5a5f-4ca2-829a-000e453600fe +owner = 0 +crc = 0x338af88a (correct) +recs[1] = [startino,freecount,free] 1:[5792,9,0xff80000000000000] +---- + +Observe also that the AGI's +agi_newino+ points to this chunk, which has never +been fully allocated. [[Real-time_Devices]] == Real-time Devices diff --git a/design/XFS_Filesystem_Structure/data_extents.asciidoc b/design/XFS_Filesystem_Structure/data_extents.asciidoc index d1617f1..5df6623 100644 --- a/design/XFS_Filesystem_Structure/data_extents.asciidoc +++ b/design/XFS_Filesystem_Structure/data_extents.asciidoc @@ -302,4 +302,43 @@ image::images/36.png[] === xfs_db bmbt Example -TODO +In this example, we dissect the data fork of a VM image that is sufficiently +sparse and interleaved to have become a B+tree. + +---- +xfs_db> inode 132 +xfs_db> p +core.magic = 0x494e +core.mode = 0100600 +core.version = 3 +core.format = 3 (btree) +... +u3.bmbt.level = 1 +u3.bmbt.numrecs = 3 +u3.bmbt.keys[1-3] = [startoff] 1:[0] 2:[9072] 3:[13136] +u3.bmbt.ptrs[1-3] = 1:8568 2:8569 3:8570 +---- + +As you can see, the block map B+tree is rooted in the inode. This tree has two +levels, so let's go down a level to look at the records: + +---- +xfs_db> addr u3.bmbt.ptrs[1] +xfs_db> p +magic = 0x424d4133 +level = 0 +numrecs = 251 +leftsib = null +rightsib = 8569 +bno = 68544 +lsn = 0x100000006 +uuid = 9579903c-333f-4673-a7d4-3254c05816ea +owner = 132 +crc = 0xc61513dc (correct) +recs[1-251] = [startoff,startblock,blockcount,extentflag] + 1:[0,8520,48,0] 2:[48,4421,16,0] 3:[80,9136,16,0] 4:[96,8569,16,0] + 5:[144,8601,32,0] 6:[192,8637,16,0] 7:[240,8680,16,0] 8:[288,9870,16,0] + 9:[320,9920,16,0] 10:[336,9950,16,0] 11:[384,4004,32,0] + 12:[432,6771,16,0] 13:[480,2702,16,0] 14:[528,8420,16,0] + ... +---- diff --git a/design/XFS_Filesystem_Structure/directories.asciidoc b/design/XFS_Filesystem_Structure/directories.asciidoc index 2df118e..73ede11 100644 --- a/design/XFS_Filesystem_Structure/directories.asciidoc +++ b/design/XFS_Filesystem_Structure/directories.asciidoc @@ -269,8 +269,61 @@ b0: 72 61 6d 65 30 30 30 30 30 33 2e 74 73 74 01 80 rame000003.tst.. c0: 00 84 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ ---- -TODO: 8-byte inode number example +This is an example of mixed 4-byte and 8-byte inodes in a directory: +---- +xfs_db> inode 1024 +xfs_db> p +core.magic = 0x494e +core.mode = 040755 +core.version = 3 +core.format = 1 (local) +core.nlinkv2 = 9 +... +core.size = 125 +core.nblocks = 0 +core.extsize = 0 +core.nextents = 0 +... +u3.sfdir3.hdr.count = 7 +u3.sfdir3.hdr.i8count = 4 +u3.sfdir3.hdr.parent.i8 = 1024 +u3.sfdir3.list[0].namelen = 3 +u3.sfdir3.list[0].offset = 0x60 +u3.sfdir3.list[0].name = "git" +u3.sfdir3.list[0].inumber.i8 = 1027 +u3.sfdir3.list[0].filetype = 2 +u3.sfdir3.list[1].namelen = 4 +u3.sfdir3.list[1].offset = 0x70 +u3.sfdir3.list[1].name = "home" +u3.sfdir3.list[1].inumber.i8 = 13422826546 +u3.sfdir3.list[1].filetype = 2 +u3.sfdir3.list[2].namelen = 10 +u3.sfdir3.list[2].offset = 0x80 +u3.sfdir3.list[2].name = "mike" +u3.sfdir3.list[2].inumber.i8 = 4299308032 +u3.sfdir3.list[2].filetype = 2 +u3.sfdir3.list[3].namelen = 3 +u3.sfdir3.list[3].offset = 0x98 +u3.sfdir3.list[3].name = "mtr" +u3.sfdir3.list[3].inumber.i8 = 13433252916 +u3.sfdir3.list[3].filetype = 2 +u3.sfdir3.list[4].namelen = 3 +u3.sfdir3.list[4].offset = 0xa8 +u3.sfdir3.list[4].name = "vms" +u3.sfdir3.list[4].inumber.i8 = 16647516355 +u3.sfdir3.list[4].filetype = 2 +u3.sfdir3.list[5].namelen = 5 +u3.sfdir3.list[5].offset = 0xb8 +u3.sfdir3.list[5].name = "rsync" +u3.sfdir3.list[5].inumber.i8 = 3494912 +u3.sfdir3.list[5].filetype = 2 +u3.sfdir3.list[6].namelen = 3 +u3.sfdir3.list[6].offset = 0xd0 +u3.sfdir3.list[6].name = "tmp" +u3.sfdir3.list[6].inumber.i8 = 1593379 +u3.sfdir3.list[6].filetype = 2 +---- [[Block_Directories]] == Block Directories diff --git a/design/XFS_Filesystem_Structure/docinfo.xml b/design/XFS_Filesystem_Structure/docinfo.xml index 32a502d..85ccda5 100644 --- a/design/XFS_Filesystem_Structure/docinfo.xml +++ b/design/XFS_Filesystem_Structure/docinfo.xml @@ -83,6 +83,7 @@ <simplelist> <member>Miscellaneous fixes.</member> <member>Add missing field definitions.</member> + <member>Add some missing xfs_db examples.</member> </simplelist> </revdescription> </revision> _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
