svn commit: r292057 - in head/sys: boot/common geom/part

[Andrey V. Elsukov]

On 10.12.15 18:07, John Baldwin wrote:
> On Thursday, December 10, 2015 10:35:07 AM Andrey V. Elsukov wrote:
>> Author: ae
>> Date: Thu Dec 10 10:35:07 2015
>> New Revision: 292057
>> URL: https://svnweb.freebsd.org/changeset/base/292057
>>
>> Log:
>>   Make detection of GPT a bit more reliable.
>>   
>>   When we are detecting a partition table and didn't find PMBR, try to
>>   read backup GPT header from the last sector and if it is correct,
>>   assume that we have GPT.
> 
> One thing that your commit message did not make clear:
> 
> Does this only detect as valid if no other partition scheme claims the
> disk?  That is, if I overwrite a previously GPT-partitioned disk with a
> different scheme (e.g. MBR), will that disk now probe as GPT instead of
> the new scheme?  If so, this is broken and needs to be reverted.  If this
> somehow does a "low" priority probe and only kicks in if no other scheme
> claims the disk, then this is ok, but you should probably have said so in
> the commit message.

Hi,

GEOM_PART uses different priorities between schemes when does probing.
In your case MBR will have greater priority and MBR will be detected in
result. As it worked before. This change only affects the case, when
there is no MBR signature at all, but we have valid backup GPT header.

-- 
WBR, Andrey V. Elsukov

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