Re: read error on superblock

[dexen deVries <dexen.devries-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hi again,


I've copied the whole filesystem elsewhere (to a file) with `ddrescue'. It found 
one damaged area on the drive, but apparently neither at start nor at the end 
of partition.

The FS on the drive was marked as `dirty' (requiring recovery upon mount). My 
guess is that kernel attempted recovery, and gave up upon read error.

Unfortunately, the `norecovery' option did not help with the drive; it only 
helped once i've moved whole FS to file.


Log from ddrescue:


# Rescue Logfile. Created by GNU ddrescue version 1.14
# Command line: ddrescue /dev/sdc3 sda3 sda3.log
# current_pos  current_status
0x149E0CCC00     +
#      pos        size  status
0x00000000  0x149E0CC000  +
0x149E0CC000  0x00001000  -
0x149E0CD000  0x11220D3000  +


my understanding is, the following line describes the damaged area, format: 
start length status-marker (`-' for error)
0x149E0CC000  0x00001000  -


Once the FS was copied to a file, it mounted correctly:
# mount -o ro,loop,norecovery ./sda3.img ./some-mountpoint 


My gripe with current (linux-3.5.0) NILFS2 driver is that I couldn't tell it 
to ignore read errors and thus force it to mount the filesystem. Ony after I've 
moved some 160GB of FS to a file (that's a bit tedious :P) it opened the FS 
just fine.


Cheers,
-- 
dexen deVries

1972 - Dennis Ritchie invents a powerful gun that shoots both forward and 
backward simultaneously. Not satisfied with the number of deaths and permanent 
maimings from that invention he invents C and Unix.
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