[Ocfs2-devel] [PATCH 1/2] Initalize bitmap_cpg of ocfs2_super to be the maximum,take 1

[Sunil Mushran]

We encountered this during offline resize.

While fsck.ocfs2 was updated to fix this issue, we never
did address the same in mkfs.

As the chances that a user will encounter this is fairly low,
we could always bail online resize if it encountered this issue.
(A dirty read of the global bitmap from tune should suffice.)

If so, ask user to run fsck.

Comments?

Mark Fasheh wrote:
> On Fri, Nov 16, 2007 at 04:41:10PM +0800, tao.ma wrote:
>   
>> This value is initialized from global_bitmap->id2.i_chain.cl_cpg. If there
>> is only 1 group, it will be equal to the total clusters in the volume. So
>> as for online resize, it should change for all the nodes in the cluster.
>> It isn't easy and there is no corresponding lock for it.
>>     
>
> Yeah, there's little point in having it that way. We probably want to update
> mkfs.ocfs2 to write out the correct value.
>
>
>   
>> bitmap_cpg is only used in 2 areas:
>> 1. Check whether the suballoc is too large for us to allocate from the global
>>    bitmap, so it is little used. And now the suballoc size is 2048, it rarely
>>    meet this situation and the check is almost useless.
>> 2. Calculate which group a cluster belongs to. We use it during truncate to
>>    figure out which cluster group an extent belongs too. But we should be OK
>>    if we increase it though as the cluster group calculated shouldn't change
>>    and we only ever have a small bitmap_cpg on file systems with a single
>>    cluster group.
>>     
>
> Did you test a very large extend on a very small (less than 1 cluster group)
> file system?
> 	--Mark
>
> --
> Mark Fasheh
> Senior Software Developer, Oracle
> mark.fasheh at oracle.com
>
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