Re: [PATCH 07/11] unpaged: COW on VM_UNPAGED

[Nick Piggin]

David S. Miller wrote:
> From: Hugh Dickins <hugh@xxxxxxxxxxx>
> Date: Thu, 17 Nov 2005 19:37:23 +0000 (GMT)
>
>
> > Remove the BUG_ON(vma->vm_flags & VM_UNPAGED) from do_wp_page, and let
> > it do Copy-On-Write without touching the VM_UNPAGED's page counts - but
> > this is incomplete, because the anonymous page it inserts will itself
> > need to be handled, here and in other functions - next patch.
> >
> > We still don't copy the page if the pfn is invalid, because the
> > copy_user_highpage interface does not allow it.  But that's not been
> > a problem in the past: can be added in later if the need arises.
> >
> > Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
>
>
> Do we even need this?  It is a very serious question...

I think for 2.6.15, yes. We [read: I :(] was too hasty in removing
this completely. However I think it would not be unresonable to spit
out a warning, and remove it in 2.6.??

Looks like Hugh's done a very good job of this, however keeping
complexity down is always a good thing.

--
SUSE Labs, Novell Inc.

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