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Re: btrfs trim erases bootloader area
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From: |
Chris Murphy |
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Subject: |
Re: btrfs trim erases bootloader area |
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Date: |
Thu, 7 Jan 2016 15:05:42 -0700 |
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?
Chris Murphy