Re: Alpha no longer recognises certain partition tables (v2.6.38)

From: Michael Cree
Date: Tue Mar 15 2011 - 21:23:50 EST


On 16/03/2011, at 4:10 AM, Linus Torvalds wrote:
On Tue, Mar 15, 2011 at 2:06 AM, Michael Cree <mcree@xxxxxxxxxxxx> wrote:
v2.6.38 boot reports it can't recognise the partition table on the system
disk on my Alpha and panics when it can't find the root device.

It worked at v2.6.38-rc7.

While I haven't done a bisect to fully verify I nevertheless suggest the
following patch as the likely cause:

1eafbfe Fix corrupted OSF partition table parsing

That sounds likely. What does something like the attached do? In
particular, what's the printed-out value of the OSF npartitions thing?

Also, it's quite possible that we should raise the value of
MAX_OSF_PARTITIONS. If I checked it right, the d_partitions[] array
starts at byte offset 148 in the sector, and it's 16 bytes in size, so
there _could_ be up to 22 partitions there. The fact that we had
defined the 'struct disklabel' to only contain 8 partitions is I think
from documentation, not a technical "there can be only eight".

I am not able to run the patch until much later today but I think the number of partitions is the issue. I have three disks, all with bsd type partition tables, and the kernel sees the partition tables of two of them (they both have fewer than five partitions) but the system disk has about nine (or it might be ten) partitions. I didn't know the limit when creating them some time ago and assumed fdisk would flag an error if the number of permitted partitions was exceeded! What's more it worked with recent kernels until now.

I'll give the patch a whirl later (my) today.

Cheers
Michael.

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