Re: [BUG] e2fsprogs & ext2/3 behave poorly with corrupt group descriptors

On Aug 23, 2006  16:12 -0400, Benjamin LaHaise wrote:
> I had a filesystem corrupted recently (yay laptops) which showed rather 
> poor behaviour with e2fsck, e2image and the filesystem itself.  What 
> happened is that a corrupt copy of one of the group descriptors was 
> written back to disk -- search for the string of 4444s in the sector 
> below.
> 
> e2image dies when attempting to take a snapshot of this filesystem with 
> an -EINVAL when it attempts to dereference the non-extant block group.  
> Similarly, the kernel refuses to mount the filesystem (which I intend to 
> make a patch for shortly), despite the fact that 99% of it is still 
> intact.

What about using one of the backup group descriptors?  I'm not sure about
e2image, but e2fsck should try that automatically (older versions were
worse at that, and if there is still a problem for e2fsck to find backups
this should be fixed).  The kernel can be told to use a backup with
"-o sb=32768" (or 32768 * {3,5,7}^n) when mounting (assuming 4kB blocksize).

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.


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