Re: [Patch] Discard incorrect nested partitions (fixes #29956)

["Grégoire Sutre" <gregoire.sutre@gmail.com>]

On 05/31/2010 08:35 PM, Vladimir 'φ-coder/phcoder' Serbinenko wrote:

> There are few ramifications of this patch. First of all some
> partitions which are just barely outside of the host partition will
> lead to something like "partition not found" errors in grub-probe.

It's not ideal, but IMHO it's better than getting "unknown filesystem"
in grub-probe -t fs while the partition is detected fine by
-t drive.

> This message should be more informative (the easiest way is to issue
> a warning in grub-probe if partitions are discarded except some cases
> where it's known not to affect the functionality like 'd'
> "subpartitions", probably such a warning in grub proper would be too
> annoying though).

A grub_dprintf when the partition is discarded (in the proposed patch)
would only print the message for relevant partitions.

> Then if you check partitions when iterating no need to recheck in
> adjust_range.

Agreed.

>> The patch still accepts sub-partitions that start at the same
>> (absolute) offset as the parent.  For instance, in the above
>> example, ls -l in grub gives both (hd1,msdos1) and
>> (hd1,msdos1,bsd1).  Should we discard (hd0,msdos1,bsd1), i.e.
>> require that sub-partitions start at a strictly positive relative
>> offset?
> No. SUN partitions comonly start at offset 0.

I don't understand what you mean: here bsd1 also starts at (relative)
offset 0, and the above example actually assumed that.

By the way, when several partition identifiers denote the same
partition, the MBI boot_device field can have different values for the
same physical partition.  This means more work (or assumptions) on the
kernel side to identify the root partition.  In the above example,
(hd1,msdos1,bsd1) would be more explicit to the NetBSD kernel than
(hd1,msdos1).

Grégoire