[Ocfs2-tools-devel] debugfs.ocfs2: How to use subcommands - 'dx_dump' and 'extent'

[Gang He]

Hi Zhen,

The sub command is not mis-functional.
please use the correct block number as input argument.

for example,
debugfs: stat dir.3019
 Inode: 92719   Mode: 0777   Generation: 2675869844 (0x9f7e8894)
        FS Generation: 2953544313 (0xb00b8279)
        CRC32: 00000000   ECC: 0000
        Type: Directory   Attr: 0x0   Flags: Valid
        Dynamic Features: (0x8) IndexedDir
        User: 0 (root)   Group: 0 (root)   Size: 241664
        Links: 2   Clusters: 8
        ctime: 0x55b7179c 0x1b7ee329 -- Tue Jul 28 13:48:12.461300521 2015
        atime: 0x55b717a6 0x62e1b90 -- Tue Jul 28 13:48:22.103685008 2015
        mtime: 0x55b7179c 0x1b7ee329 -- Tue Jul 28 13:48:12.461300521 2015
        dtime: 0x0 -- Thu Jan  1 08:00:00 1970
        Refcount Block: 0
        Last Extblk: 0   Orphan Slot: 0
        Sub Alloc Slot: 0   Sub Alloc Bit: 7
        Indexed Tree Root: 69153
        Tree Depth: 0   Count: 243   Next Free Rec: 1
        ## Offset        Clusters       Block#          Flags
        0  0             8              10803280        0x0

debugfs: dx_root <69153>
Dir Index Root: 69153   FS Generation: 2953544313 (0xb00b8279)
        Clusters: 8   Last Extblk: 0   Dir Inode: 92719
        Sub Alloc Slot: 0   Sub Alloc Bit: 1
        Flags: (0x0)
        Total Entry Count: 10002
        CRC32: 00000000   ECC: 0000
        Tree Depth: 0   Count: 243   Next Free Rec: 8
        ## Offset        Clusters       Block#          Flags
        0  0             1              10803408        0x0
        1  464146762     1              10803464        0x0
        2  917925469     1              10803432        0x0
        3  1511702967    1              10803448        0x0
        4  1963815431    1              10803416        0x0
        5  2450500483    1              10803456        0x0
        6  2974120705    1              10803424        0x0
        7  3697298737    1              10803440        0x0




Thanks
Gang


>>> 
> Hi all,
> 
> I'm very confused by how to use subcommands of debugfs - 'dx_dump' and 
> 'extent'.
> 
> Quote from man page about debugfs.ocfs2:
> ...
>  dx_dump filespec
>               Display the indexed directory information for the given 
> directory.
>  extent <block#>
>               Display the contents of the extent structure at block#.
> ...
> 
> 1. dx_dump
> I am on a well-worked 3 nodes cluster. 
> Step 1: move ocfs2-tools source (it has directory tree) to /mnt/shared(shared 
> disk mount point);
> Step 2: ls -R - in case it needs to generate indexed directory struct in 
> memory. I don't know much about indexed directory;
> Step 3: debugfs.ocfs2  -> open device -> 'dx_dump /ocfs2-tools' or 'dx_dump 
> <139801>', it show nothing, but "lines ?-?/? (END)
> " 
> 
> And 'stats' show that "indexed-dirs" feature is on.
> 
> 
> 2.extent
> Step 1: created a 5G large file by 'fallocate -l 7G 7g-file.img' in 
> /mnt/shared/;
> Step 2: stat /7g-file.img, the output is:
> 
>         Inode: 193645   Mode: 0644   Generation: 745361378 (0x2c6d4fe2)
>         FS Generation: 3527657941 (0xd243c9d5)
>         CRC32: 00000000   ECC: 0000
>         Type: Regular   Attr: 0x0   Flags: Valid 
>         Dynamic Features: (0x0) 
>         User: 0 (root)   Group: 0 (root)   Size: 7516192768
>         Links: 1   Clusters: 1835008
>         ctime: 0x55b5f1a9 0x2f571f34 -- Mon Jul 27 16:54:01.794238772 2015
>         atime: 0x55b5f1a9 0x26fee434 -- Mon Jul 27 16:54:01.654238772 2015
>         mtime: 0x55b5f1a9 0x2f571f34 -- Mon Jul 27 16:54:01.794238772 2015
>         dtime: 0x0 -- Thu Jan  1 08:00:00 1970
>         Refcount Block: 0
>         Last Extblk: 0   Orphan Slot: 0
>         Sub Alloc Slot: 0   Sub Alloc Bit: 108
>         Tree Depth: 0   Count: 243   Next Free Rec: 57
>         ## Offset        Clusters       Block#          Flags
>         0  0             32255          225793          0x1 Unwritten
>         1  32255         32255          290305          0x1 Unwritten
>         2  64510         32255          322561          0x1 Unwritten
>         3  96765         32255          354817          0x1 Unwritten
>         4  129020        32255          387073          0x1 Unwritten
>         5  161275        32255          419329          0x1 Unwritten
> ...
>          52 1677260       32255          1967617         0x1 Unwritten
>         53 1709515       32255          1999873         0x1 Unwritten
>         54 1741770       32255          2032129         0x1 Unwritten
>         55 1774025       32255          2064385         0x1 Unwritten
>         56 1806280       28728          2096641         0x1 Unwritten
> 
> 
> 
> Step 3: extent <2096641>, and other blockno in filed Block#, but it always 
> shows:
> 
> debugfs: extent <2096641>
> extent: Bad magic number in extent block while reading extent block 2096641
> 
> And I also notice this info - "  Last Extblk: 0 ".
> Why the Last Exblk is 0, even for 7G large file?  
> 
> I don't know much about extent block mechanism.  Please correct me with your 
> experience;-)
> 
> --
> Eric, Ren
> 
> 
> 
> 
> 
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