Re: btrfs trim erases bootloader area

[Chris Murphy]

On Thu, Jan 7, 2016 at 4:10 PM, Filipe Manana <address@hidden> wrote:
> On Thu, Jan 7, 2016 at 10:05 PM, Chris Murphy <address@hidden> wrote:
>> On Thu, Jan 7, 2016 at 12:16 PM, Filipe Manana <address@hidden> wrote:
>>> On Thu, Jan 7, 2016 at 7:11 PM, Andrei Borzenkov <address@hidden> wrote:
>>>> As discussed on opensuse-factory list, running fstrim on btrfs erases
>>>> bootloader area, rendering system unbootable. See
>>>>
>>>> https://lists.opensuse.org/opensuse-factory/2016-01/msg00067.html
>>>> https://lists.opensuse.org/opensuse-factory/2016-01/msg00090.html
>>>>
>>>> and follow-ups that demonstrate that beginning of device gets zeroed out.
>>>>
>>>> Not sure what we can do, but from GRUB side I can only see disabling
>>>> embedding support on btrfs entirely.
>>>
>>> Try this (sent to the btrfs mailing list yesterday):
>>>
>>> http://git.kernel.org/cgit/linux/kernel/git/fdmanana/linux.git/commit/?h=integration-4.5&id=7b6cb6618b45bb383f9336ec89df5f1f31f9935b
>>>
>>> thanks
>>
>> The description is a bit confusing by referring to MBR, which mainly
>> exists only at LBA 0. In the case of extended partitions, the EBR
>> (using the same MBR format) is still outside the LBA range for Btrfs
>> to apply fitrim ioctl. The VBR however, would be inside that range,
>> and it's that 64KiB bootloader pad Btrfs reserves that's being
>> inadvertently obliterated. Correct?
>
> Right, the title and description is confusing. I lacked the
> terminology and all technical details of grub, so I just used MBR to
> refer to any sector containing code used by the boot loader.
> Do you like the following title/change log better?
>
> http://git.kernel.org/cgit/linux/kernel/git/fdmanana/linux.git/commit/?h=integration-4.5&id=6a340b36b68463ddca2b088c398d94a067a00e82
>
> I'll resend it later or tomorrow.
>

Looks good to me!

-- 
Chris Murphy