Host Protected Area unconditional disable

[Scott James Remnant]

I only authored the patch that did the module defaults change in the 
kernel rather than as a modprobe.d file.  Part of my reasoning for doing 
this was making the fact we have a different default irritate the kernel 
team enough that they'd eventually get around to a solution that meant 
we didn't have to :p

I'm glad to see my cunning plan worked.

Scott

On 22/12/10 11:29, Andy Whitcroft wrote:
> Traditionally we have turned off Host Protected Area (HPA) on drives
> when it was detected.  Once we had installs in the field in those mode
> we were then unable to turn HPA back on without breaking older installs
> which used the extra space.  The flip side has always been that once
> HPA has been turned off a power cycle is needed to turn it back on.
> This can severely confuse another operating system when it finds the
> disk has changed size.  In rare cases it can cause RAID cards to drop
> RAID sets on the floor thinking they are corrupt.  All bad.
>
> We have long had a request to turn off the unconditional disabling of
> HPA [1].  However as mentioned above this would render those who had
> made use of the protected space in their partitions unbootable.  The
> solution seemed to be to try and work without disabling HPA and only
> disable it if partition access requires it.
>
> It seems that in v2.6.35 a series of patches were committed to mainline
> which handle this situation in exactly the suggested manner, the following
> commits are those which extended the existing IDE functionality to
> ATA drives:
>
>      libata: implement on-demand HPA unlocking
>      libata: use the enlarged capacity after late HPA unlock
>      SCSI: implement sd_unlock_native_capacity()
>
> It therefore seems that from v2.6.35 we should be able to drop our force
> disable of HPA in the commit below.
>
>    commit eaea8ccbd3adf0b36942ae834eaa825094772c95
>    Author: Scott James Remnant<scott at canonical.com>
>    Date: Tue Mar 3 14:20:01 2009 +0000
>
>      UBUNTU: SAUCE: (no-up) libata: Ignore HPA by default.
>
> I am therefore proposing we drop this latter patch for Natty and see who
> screams (I am hoping there will be none).  We might want to get a call
> for testing out on this feature for natty-alpha-2.
>
> Comments?
>
> -apw
>
> [1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/380138