Determining filename from absolute sector failure in raid0

[Bryce <bryce@zeniv.linux.org.uk>]

I have a raid0 comprised of 4x identical 300Gb drives

Disk /dev/hdf: 300.0 GB, 300001443840 bytes
255 heads, 63 sectors/track, 36473 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x0009f25f

   Device Boot      Start         End      Blocks   Id  System
/dev/hdf1   *           1       36473   292969341   fd  Linux raid
autodetect

md1 : active raid0 hdk1[0] hdg1[2] hdf1[1] hde1[3]
      1171876864 blocks 256k chunks

hdf recently wobbled and the kernel  happily dumped out the following
message (about 20 odd times)

hdf: dma_intr: status=0x51 { DriveReady SeekComplete Error }
hdf: dma_intr: error=0x40 { UncorrectableError }, LBAsect=216521307,
high=12, low=15194715, sector=216521303
ide: failed opcode was: unknown
end_request: I/O error, dev hdf, sector 216521303

terrific.
smartctl shows
  5 Reallocated_Sector_Ct   0x0033   252   252   063    Pre-fail 
Always       -       16
196 Reallocated_Event_Count 0x0008   251   251   000    Old_age  
Offline      -       2
197 Current_Pending_Sector  0x0008   253   253   000    Old_age  
Offline      -       1
198 Offline_Uncorrectable   0x0008   252   252   000    Old_age  
Offline      -       1

so while a few sectors have been remapped the sector remapping table is
barely used, so I'm reasonably confident the disk is 'ok' in terms of
normal operation
Now my question about all this is how the hell do I determine what file
it was trying to access? (I just want to be sure that whatever file it
was fiddling with isn't a steaming pile of poo now)

normally if it were a single disk it would be reasonably straightforward
to work out what file was being used from debugfs: icheck <block>,
ncheck  <inode from previews operation>
the issue I have with raid0 is, exactly what block should I be pointing
debugfs at since the kernel has given an absolute address on a physical
disk and no logical information as to where in the FS it was at the time ?

tune2fs -l /dev/md1
Block count:              292969216
Block size:               4096

mdadm --examine /dev/hdf1
/dev/hdf1:
          Magic : a92b4efc
        Version : 00.90.00
           UUID : 2132d2e6:a2955ac2:6ad2f3dc:52b3dfd6
  Creation Time : Wed May 26 18:34:06 2004
     Raid Level : raid0
  Used Dev Size : 292969216 (279.40 GiB 300.00 GB)
   Raid Devices : 4
  Total Devices : 4
Preferred Minor : 1

    Update Time : Wed May 26 18:34:06 2004
          State : active
 Active Devices : 4
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 0
       Checksum : bd5e5781 - correct
         Events : 0.5

     Chunk Size : 256K

      Number   Major   Minor   RaidDevice State
this     1      33       65        1      active sync   /dev/hdf1

   0     0      33        1        0      active sync   /dev/hde1
   1     1      33       65        1      active sync   /dev/hdf1
   2     2      34        1        2      active sync   /dev/hdg1
   3     3      34       65        3      active sync             <---
empty. bug? (expected /dev/hdk1)

mdadm --version
mdadm - v2.6.2 - 21st May 2007

Would I be correct in assuming that I start my offset from hde1? do I
need some other funky math to account for striping/blocking?

Or I could just say 'to hell with it' and listen to elevator music all day.


Phil
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