On Mon, Aug 31, 2009 at 09:53:10AM +0200, Kay Sievers wrote:
> On Mon, Aug 31, 2009 at 09:21, Thomas Bächler<thomas@xxxxxxxxxxxxx> wrote:
> > Theodore Tso schrieb:
> >>
> >> Hmm, well *that's* a change between the blkid that was in e2fsprogs
> >> and the version that was in util-linux-ng. In e2fsprogs' blkid, I
> >> stopped after I found the first match. As a result, the filesystems
> >> that had the most sophisticated (and thus less prone to false
> >> positives) were put *first*, and filesystems that had sloppy
> >> mkfs/mkswap/dmcrypt-setup programs that didn't zap the first and last
> >> 32k-64k of the partition to prevent false positives were placed later
> >> in the detection table.
> >>
> >> If the new blkid library in util-linux-ng searches the whole list and
> >> finds the *last* match, and it's using the same order of probes as in
> >> e2fsprogs' blkid, it means there will be a significant chance in
> >> behavior, and the danger is that there may be many more false
> >> positives.
> >
> > I think you read me wrong: It's not returning the last result. When it
> > finishes all the probes, it checks if there was exactly one result and
> > prints that. If there was more than one result, it discards them all and
> > returns no result at all. This will lead to no false positives at all, but
> > lots of false negatives with LUKS volumes created with old cryptsetup
> > versions.
>
> Right, and it's the expected behavior.
>
> We can not afford to return anything we are not sure about. It may
> result in serious data corruption and data loss to return the wrong
> type of filesystem. Therefore we don't return anything if we find
We already have such experience. Somewhere in RH bugzilla are reports
from people who *lost data* because LiveCD init script has called
swapon for wrong partition.
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
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