Re: [patch] ksm: check for ERR_PTR from follow_page()

[Johannes Weiner]

On Wed, Apr 21, 2010 at 10:58:07PM +0200, Andrea Arcangeli wrote:
> On Wed, Apr 21, 2010 at 10:53:05PM +0200, Johannes Weiner wrote:
> > + * Returns the mapped (struct page *), %NULL if no mapping exists, or
> > + * an error pointer if there is a mapping to something not represented
> > + * by a page descriptor (see also vm_normal_page()).
> 
> where exactly in vm_normal_page? Note I already checked vm_normal_page
> before sending the prev email and I didn't immediately see.  I search
> return and they all return NULL except the return pfn_to_page(pfn), so
> is pfn_to_page that returns -EFAULT (the implementations I checked
> don't but there are plenty that I didn't check...).

It's not vm_normal_page() that returns -EFAULT.  It is follow_page()
that translates NULL from vm_normal_page() into -EFAULT.
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