Re: [PATCH V2] Add support for BTRFS raid5/6 to GRUB

[Goffredo Baroncelli]

On 05/09/2018 07:00 PM, Daniel Kiper wrote:
> On Tue, Apr 24, 2018 at 09:13:09PM +0200, Goffredo Baroncelli wrote:
>>
>> Hi All,
>>
>> the aim of this patches set is to provide support for a BTRFS raid5/6
>>  filesystem in GRUB.
>>
>> The first patch, implements the basic support for raid5/6. I.e this works 
>> when
>>  all the disks
>> are present.
>>
>> The next 4 patches, are preparatory ones.
>>
>> The last two implements the support for raid5/6 recovery. It allow to read
>> from the filesystem even when 1 or 2 (for raid 6) disk(s) are missing.
>>
>> The last one is the more controversial. The code for the raid6 recovery is
>> copied from the GRUB file reaid6_recovery.c . I preferred this approach,
>> because the original code assumes that the read is GRUB_DISK_SECTOR_SIZE
>> bytes based (512 bytes). Instead the GRUB BTRFS implementation need to
>> read the disk with a granularity of the byte.
>> I tried to update the code (and the function which the code calls), but
>> the change was quite invasive. So for now I preferred to duplicating the
>> code, to get some feedback.
>>
>> I tested the code in grub-emu, and it works (for me) both with all the disks,
>>  and with some disks missing. I checked the sh1sums calculated from grub and
>> from linux and these matched.
>>
>> Comments are welcome.
> 
> Mostly nitpicks. However, if we can reuse reaid6_recovery.c somehow that
> will be great. Even if this require some more patches.

I liked the idea too. I am not sure to be able to tests all the cases. Do you 
know if it exists a list of tests about raid6_recovery and dm ?

Anyway, I update the patch. Tomorrow I will test these and then I issue the 
patch set.

BR

> 
> Daniel
> 
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