Re: [PATCH 1/2] mdadm: Fix array size mismatch after grow

[Lukasz Florczak <lukasz.florczak@linux.intel.com>]

On Tue, 21 Jun 2022 00:28:18 +0800, Coly Li <colyli@suse.de> wrote:

> > 2022年6月3日 22:30，Lukasz Florczak
> > <lukasz.florczak@linux.intel.com> 写道：
> > 
> > On Mon, 30 May 2022 18:01:05 +0800, Coly Li <colyli@suse.de> wrote:
> > 
> > Hi Coly,  
> >> Hi Lukasz,
> >> 
> >>   
> >>> 2022年4月7日 22:27，Lukasz Florczak
> >>> <lukasz.florczak@linux.intel.com> 写道：
> >>> 
> >>> imsm_fix_size_mismatch() is invoked to fix the problem, but it
> >>> couldn't proceed due to migration check. This patch allows for
> >>> intended behavior.  
> >> 
> >> 
> >> Could you please explain a bit more about why “it couldn’t proceed
> >> due to migration”, and what is the “intended behavior”? It may help
> >> me to understand your change and response faster.  
> > 
> > The intended behavior here is to fix the array size after grow that
> > is displayed in mdadm detail, since there can be a mismatch if the
> > raid was created in EFI [1]. That is the array size is not
> > consistent with the formula: 
> > Array_size * block_size = Num_stripes * Chunk_size *
> > Num_of_data_drives 
> > 
> > That fix couldn't happen as the metadata update part was efficiently
> > omitted with continue statement after the migration type condition
> > was met. 
> > 
> > About migration I didn't go that much into detail, but it was an
> > issue that dev->vol.migr_type was still in MIGR_GEN_MIGR state even
> > though imsm_fix_size_mismatch() was called after migration has been
> > finished, at least from the mdadm's point of view. That happens
> > because this value is changed later, afaik, by mdmon. The initial
> > idea here must've been not to change the array size during
> > migration, but that is not valid since its state is just not
> > updated yet.
> > 
> > [1]
> > https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/commit/?id=895ffd992954069e4ea67efb8a85bb0fd72c3707
> >  
> 
> Copied, thanks for the hint.
> 
> BTW, now I do the imsm related test with IMSM_NO_PLATFORM=1 and
> IMSM_DEVNAME_AS_SERIAL=1. To test situation as the above text
> mentioned, do I have to find a real hardware with VROC supported?

Hi Coly,

Having a real hardware with VROC support would be the most convenient
solution here. However, you could do a quick hack to overcome this
situation. That would be commenting out the line:
array_size = round_size_to_mb(array_blocks, data_disks);
in init_super_imsm_volume(). Then creating RAID in OS should have the
same size mismatch issues as size per drive won't be aligned to 1MiB
(considering you create raid with size not aligned to 1MiB) - raid
size created in EFI only has to be multiple of sector size and chunk
size.
Hope this helps you.

Thanks,
Lukasz
> 
> Coly Li
>