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SubjectRe: [Patch 8/8] kexec: allow to shrink reserved memory
On Fri, 21 Aug 2009 09:59:27 +0800
Amerigo Wang <xiyou.wangcong@gmail.com> wrote:

> On Fri, Aug 21, 2009 at 09:34:52AM +0900, KAMEZAWA Hiroyuki wrote:
> >On Thu, 20 Aug 2009 17:15:56 +0800
> >Amerigo Wang <amwang@redhat.com> wrote:
> >
> >> > The, problem is whether memmap is there or not. That's all.
> >> > plz see init sequence and check there are memmap.
> >> > If memory-for-crash is obtained via bootmem,
> >> > Don't you try to free memory hole ?
> >> >
> >>
> >> Hi,
> >>
> >> It looks like that mem_map has 'struct page' for the reserved memory, I
> >> checked my "early_node_map[] active PFN ranges" output, the reserved
> >> memory area for crash kernel is right in one range. Am I missing
> >> something here?
> >>
> >> I don't know why that oops comes out, maybe because of no PTE for thoese
> >> pages?
> >>
> >Hmm ? Could you show me the code you use ?
>
> (Sorry that I reply to you with my gmail, my work email can't send out
> this message, probably because one of the destinations is broken...
> I am the same person, don't be confused. :-)
>
> Sure. Below is it:
>
> + for (addr = end + 1; addr < crashk_res.end; addr += PAGE_SIZE) {
> + printk(KERN_DEBUG "PFN is valid? %d\n", pfn_valid(addr>>PAGE_SHIFT));
> + ClearPageReserved(virt_to_page(addr));
> + init_page_count(virt_to_page(addr));
> + free_page(addr);
> + totalram_pages++;
> + }
>
>
> pfn_valid() returns 1, and oops happens at ClearPageReserved().
> ('addr' is right between crashk_res.start and crashk_res.end)

Confused,
if pfn_valid(addr >> PAGE_SHIFT) == true

you should do
ClearPageReserved(pfn_to_page(addr >> PAGE_SHIFT));

because addr is physical address, not virtual.
I guess crashk_res.end is physical address....

Thanks,
-Kame


>
> Thank you!
>



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