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

[Daniel Kiper]

On Wed, May 09, 2018 at 09:36:55PM +0200, Goffredo Baroncelli wrote:
> 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 ?

Sadly I know nothing about that.

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

I agree mostly with your replies. Please respin the patches
and I will take a look at v2.

Thank you for doing the work.

Daniel