[lvm-devel] Re: [linux-lvm] A question about the metadata circular buffer

[yuan yuan]

On Fri, Dec 12, 2008 at 8:49 PM, Alasdair G Kergon <agk at redhat.com> wrote:

> On Fri, Dec 12, 2008 at 08:35:46PM +0800, yuan yuan wrote:
> >     if ((new_wrap && old_wrap) ||
> >             (rlocn && (new_wrap || old_wrap) && (new_end >
> rlocn->offset))
> > ||
> >             (mdac->rlocn.size >= mdah->size)) {
> >                 log_error("VG %s metadata too large for circular buffer",
> >                           vg->name);
>
> > My question is , for a circular buffer, why should we check so many
> > conditions instead of just checking (mdac->rlocn.size >= mdah->size)?
>
> The buffer has to hold *two* versions of the metadata during a change,
> the old and the new version, and those two could be different sizes.
>

Does this mean that if the buffer size is 2K, the size of the metadata can't
be larger than 1K?
What will happen if we just hold one version?


>
> Alasdair
> --
> agk at redhat.com
>
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