Re: [Ext2-devel] [RFC 0/13] extents and 48bit ext3

On Jun 09, 2006 18:52 -0400, Valdis.Kletnieks@xxxxxx wrote:
On Fri, 09 Jun 2006 20:33:18 +0400, Alex Tomas said:
one who needs/wants to go back may get rid of extents by:
a) remounting w/o extents option
b) copying new-fashion-style files so that copies use blockmap
c) dropping extents feature in superblock

OK.. Obviously my brain is tiny and easily overfilled.

...

Given that the whole alledged problem with extents is that they're not
backward compatible, how do you read the files in (b) so that you can copy
them, if the data is in the non-compatible extents that you can't read because
you've disabled extents?

You mount with the new kernel without "-o extents", and find files with
extents "lsattr -R /mnt/tmp | awk '/----e / print { $2 }'", copy those
files, mv over old files, unmount.

A similar thing is necessary for ext3 filesystems before you can mount them
as ext2 - they can't be mounted as ext2 until the journal is recovered
(an unrecovered journal is an incompatible feature).

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

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