Re: Extended partition mapping wrong size

From: Phillip Susi
Date: Tue Apr 06 2010 - 09:58:54 EST

On 4/6/2010 7:47 AM, Karel Zak wrote:
> This is probably kernel bug. It's really insane that the extended
> pseudo partition overflows to the next logical partition.


> Please no. I think the size should not be more than 2 sectors (1024
> bytes). The current concept works for years and we have in userspace
> /etc/partitions parsers that use "if (blocks <= 1)" to detect
> extended partitions.

Could you elaborate a bit on this? What programs have such tests and
what would they do differently if it were larger?

> The other problem are mkfs programs, the space used for alignment
> could be 1MiB (or more) -- it's enough many mkfs programs.

What's wrong with that? If you REALLY want to, there's no reason you
can't create a tiny fs there. Then again, I could swear that once upon
a time the kernel simply did not bother creating a dev node for the
extended partition, and this seems to be a hack that was put in to make
it easy for LILO to install to one. Personally I'd prefer going back to
the old behavior of just not having a useless device there.

> BTW, Linux does not use this policy for the others nested partition
> tables (e.g. Solaris, BSD, Minix, ...). The extended dos partition
> table is exception. The primary partitions for the others nested PT
> are exported to the system with its real size :-)

Indeed, also the hidden space in the logical partitions is also not
exposed, otherwise you would have two dev nodes per logical partition.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at