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

Andreas Dilger
2006-06-09T23:21:04Z

On Jun 09, 2006 18:52 -0400, Valdis.Kletnieks@vt.edu 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.