[Cluster-devel] [PATCH] libgfs2: Return the rgrp count in lgfs2_rgrps_plan()

[Andrew Price <anprice@redhat.com>]

Hi Bob,

On 12/10/15 16:47, Bob Peterson wrote:
> ----- Original Message -----
>> lgfs2_rgrps_plan() previously returned one of the rgrp sizes
>> specifically so that gfs2_grow could check it. This check was also done
>> inside the function so the return value would always be 0 when the rgrp
>> size was too small anyway (really this means that there's not enough
>> space in which to place sensibly sized rgrps). As returning 0 is
>> sufficient to pass back the same information, we can return the resource
>> group count from lgfs2_rgrps_plan() instead, as that is a more useful
>> value in general.
>>
> Hi Andy,
>
> Does this all work with a tiny file system that only has one resource group?
> I remember trying to code similar things and Abhi kept having to fix it
> because of problems with single-rgrp file systems. Bear in mind, I haven't
> looked at the rest of this function in detail, so I'm speaking somewhat out
> of ignorance.

I'm not sure which problems you're referring to to test for them but 
this patch is essentially cosmetic so it doesn't change the behaviour of 
mkfs.gfs2 nor gfs2_grow. I have done various tests with small file 
systems since the lgfs2_rgrp* functions were introduced though and 
they've held up well (or have been fixed), and those functions are 
well-covered by the test suite.

That said, to double-check I've created a 9M fs (minimum journal size is 
8M) and ran a successful mount-fill-umount-fsck-mount-grow-umount-fsck 
test on it. The initial resource groups were obviously tiny (ri_length = 
1) but the ones gfs2_grow added were much larger, which is expected as 
lgfs2_rgrps_plan() doesn't use the existing rgrps' sizes in its 
calculations.

Cheers,
Andy