Re: Files and direcories with dir_index not accessable

On Aug 23, 2006  12:29 +0200, J�rg Sommer wrote:
> > I suspect there is some problem with the filename hash calculation for
> > 8-bit characters and this is doing the lookup in the wrong leaf block.
> 
> What can I do? I tried to reproduce this problem with a smaller file
> system, but I was alright. Is the ‘Directory Hash Seed’ important? And, I
> use tea as hash algorithm.

Yes, the hash seed is important.  This essentially randomizes the on-disk
directory order for a given sequence of filenames, so that it is difficult
to develop hash-collision attacks on large directories.

What you can do is to put some debugging into the kernel to print out the
hash values and the leaf block number that the ext3 code is using to do
the (failed) lookup.  Compare this to the hash value and leaf block that is
used when the file is initially added to the directory, and the corresponding
values from the debugfs dump.

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


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