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

From: Michael Cree
Date: Wed Mar 16 2011 - 03:40:18 EST

On 16/03/11 05:17, Linus Torvalds wrote:
On Tue, Mar 15, 2011 at 8:10 AM, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

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.

Actually, I think it's byte offset 148 in the structure, but the
structure is at offset 64 in the partition sector, so I think that
leaves room for just 18 partitions in one 512-byte sector.

Of course, we do end up reading a whole page, so historically we've
been able to see even more when the sector is aligned right (and it
is, it's the first sector). So by mistake we could have accepted many
more partitions and it just "worked" because we never actually checked
any limits.

OK, I've fallen for that and created too many partitions on my system disk. When using your patch dmesg reports:

[ 7.511714] sd 1:0:0:0: [sdb] 2930277168 512-byte logical blocks: (1.50 TB/1.36 TiB)
[ 7.551753] sd 1:0:0:0: [sdb] Write Protect is off
[ 7.572261] sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00
[ 7.591792] sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 7.633785] OSF: 10 partitions
[ 7.654292] sdb: sdb1 sdb2 sdb3 sdb4 sdb5 sdb6 sdb7 sdb8
[ 7.675777] sd 1:0:0:0: [sdb] Attached SCSI disk

I could get it back to eight partitions but it will require copying the largest partition to another disk and back again as that partition does not meet the conditions for resizing. Part of the reason for so many partitions was a brilliant scheme (or so it seemed at the time) when I repartitioned the disk in a manner that enabled me to do an efficient "in-place" repartitioning of an already well used disk.

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