[Ocfs2-devel] lvb length issue [was Re: [ocfs2-tools-devel] question of ocfs2_controld (Jun 27)]

[Joel Becker]

On Tue, Jul 07, 2009 at 11:01:13AM -0500, David Teigland wrote:
> On Mon, Jul 06, 2009 at 08:26:39PM +0800, Coly Li wrote:
> > DLM_USER_LVB_LEN is defined to 32.
> 
> > DLM_LVB_LEN is 64.
> 
> Yes, the kernel dlm api allows a variable lvb size, but the user dlm api fixes
> it at 32.
> 
> Do you need to actually use a 64 byte lvb from userspace?  Or do you just need
> to create the locksapce with a 64 byte lvb?  We could add a flag to work
> around the later fairly easily.  Changing the dlm user/kernel interface to
> copy variable size lvb's would take some significant work.

	In this case, it's userspace utilities locking to verify no one
else is doing anything in the cluster.  coly has noticed mkfs.ocfs2, but
tunefs.ocfs2 and fsck.ocfs2 do the same thing.
	While a 64byte user lvb would be ideal, I think a flag to work
around it would be great.  If the flag says "I know this lockspace may
have !32byte LVBs, but I promise not to use them", and you can error
when someone tries to set/get LVBs in that case, I think it works.

Joel

-- 

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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127