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Re: [dm-devel] [PATCH] Check region size during dirty log creation



Am Mittwoch, den 29.10.2008, 15:43 +0000 schrieb Alasdair G Kergon:
> On Wed, Oct 29, 2008 at 04:07:30PM +0100, Heinz Mauelshagen wrote:
> > Am Mittwoch, den 29.10.2008, 13:56 +0000 schrieb Alasdair G Kergon:
> > > On Wed, Oct 29, 2008 at 02:02:08PM +0100, Heinz Mauelshagen wrote:
> > > The validation should be consistent between userspace and kernel.
> > It should be sufficiently restrictive in the kernel to prevent
> > programming errors causing oopses. It can be called via the kernel
> > interface by any application anyway, so doesn't need to enforce our
> > uspace restrictions (think direct IOCTL calls).
>  
> Surely the validation in the two places should match?

I'm arguing, that the kernel should only restrict to prevent against
programming errors.

> Why would userspace need a tighter restriction than the kernel?

Because of specific application requirements.
Why shouldn't we support 2 sector dirty log region sizes for any
application who wants them ?

> One or the other is incorrect.
> - E.g. Does kcopyd handle sub-page regions OK now?

kcopyd allows copying io regions of single sectors.

Heinz

> 
> Alasdair


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