Re: [PATCH 13/13] maps#2: Add /proc/kpagemap interface

[Dave Hansen <hansendc@us.ibm.com>]

On Fri, 2007-04-06 at 17:03 -0500, Matt Mackall wrote:
> 
> +static ssize_t kpagemap_read(struct file *file, char __user *buf,
> +                            size_t count, loff_t *ppos)
> +{
...
> +               for (; i < 2 * chunk / KPMSIZE; i += 2, pfn++) {
> +                       ppage = pfn_to_page(pfn);
> +                       if (!ppage) {
> +                               page[i] = 0;
> +                               page[i + 1] = 0;
> +                       } else {
> +                               page[i] = ppage->flags;
> +                               page[i + 1] = atomic_read(&ppage->_count);
> +                       }
> +               } 

I think this needs a pfn_valid() check for sparse/discontig systems.  I
think we'll oops if we have holes because we don't check pfn_valid()
inside of pfn_to_page().

-- Dave

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