Comment 2 for bug 203704

Maybe. It depends on how rigorous the check is. Kernel memory, where I
believe the actual mount of a reiserfs partition would usually take place,
can never be swapped as far as I know. That leaves a userspace program that
deals with an rfs partition, like mkreiserfs. Since those programs would
never operate (with good results) on an in-use swap partition, the chances
that the data contained in the header would match the relevant data for a
swap partition is highly unlikely. Looking at the reiserfs header (
http://homes.cerias.purdue.edu/~florian/reiser/reiserfs.php) one could check
the partition two ways: by computing (# of blocks in partition) * (block
size), which is more likely to be inaccurate due to volume size not matching
partition size, or by just checking if the header points to a valid root
node (by checking the node height value). This pattern seems relatively
unlikely to be reproduced in a swap partition.

This is a rather rigorous check, I will admit, but the reason I flagged this
as vol_id's problem was because often the space left in the beginning of
volumes is used for bootloader-related stuff. I think that it is more
desirable that mkreiserfs touch only what is needed. This hasn't been a
problem with linux distros in the past, obviously because this value was not
computed, but I think backwards compatibility is always a plus if we can get
it.

I don't know the code at all for vol_id, but if those who do thing this
approach is useful, worthwhile, and doable, I'm wiling to research and
submit a patch to this effect.

On Wed, Mar 19, 2008 at 7:01 PM, Colin Watson <email address hidden>
wrote:

> 0x10000 is in the middle of swap data. If vol_id checked for that first,
> wouldn't it be quite possible (not even all that unlikely if a reiserfs
> superblock had been swapped out ...) for it to run into something that
> looked like reiserfs or any other filesystem in the middle of the swap
> data? The swap data could be anything.
>
> I have to say that mkreiserfs seems like the buggy program here.
>
> --
> vol_id reports swap instead of resierfs
> https://bugs.launchpad.net/bugs/203704
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