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SubjectRe: Memory corruption during hibernation since 2.6.31
Date
On Thursday 29 July 2010 07:24:29 KAMEZAWA Hiroyuki wrote:
> On Thu, 29 Jul 2010 14:23:33 +0900 (JST)
>
> KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
> > Can you please add explicit commenting in the code?
>
> How about this ?
> ==
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
> At hibernation, all pages-should-be-saved are written into a image (here,
> swap). Then, swap_map[], memmap etcs are also saved into disks.
>
> But, swap allocation happens one by one. So, the final image of swap_map[]
> is different from saved one and the commit
> c9e444103b5e7a5a3519f9913f59767f92e33baf changes page's state while
> assiging swap. Because memory can be modified in hibernation is only
> not-to-be-save memory. it's a breakage.
>
> This patch fixes it by disabling swap entry reuse at hibernation.

6 days with no crash - so the patch seems to work.



> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
> mm/swapfile.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.34.org/mm/swapfile.c
> ===================================================================
> --- linux-2.6.34.org.orig/mm/swapfile.c
> +++ linux-2.6.34.org/mm/swapfile.c
> @@ -315,8 +315,15 @@ checks:
> if (offset > si->highest_bit)
> scan_base = offset = si->lowest_bit;
>
> - /* reuse swap entry of cache-only swap if not busy. */
> - if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
> + /*
> + * reuse swap entry of cache-only swap if not busy &&
> + * when we're called via pageout(). At hibernation, swap-reuse
> + * is harmful because it changes memory status...which may
> + * be saved already.
> + */
> + if (vm_swap_full()
> + && usage == SWAP_HAS_CACHE
> + && si->swap_map[offset] == SWAP_HAS_CACHE) {
> int swap_was_freed;
> spin_unlock(&swap_lock);
> swap_was_freed = __try_to_reclaim_swap(si, offset);
>


--
Ondrej Zary


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