Re: [RFC][PATCH v1 10/11] mm: clear PageHWPoison in memory hotremove

[Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>]

On Fri, Nov 09, 2018 at 03:47:14PM +0900, Naoya Horiguchi wrote:
> One hopeful usecase of memory hotplug is to replace half-broken DIMMs
> with new ones, so it makes sense to clear hwpoison info at the time of
> memory hotremove.
> 
> I hope that this patch covers the topic discussed in
> https://lkml.org/lkml/2018/1/17/1228
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> ---
>  mm/page_alloc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git v4.19-mmotm-2018-10-30-16-08/mm/page_alloc.c v4.19-mmotm-2018-10-30-16-08_patched/mm/page_alloc.c
> index 970d6ff..27826b3 100644
> --- v4.19-mmotm-2018-10-30-16-08/mm/page_alloc.c
> +++ v4.19-mmotm-2018-10-30-16-08_patched/mm/page_alloc.c
> @@ -8139,8 +8139,9 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
>  		 * The HWPoisoned page may be not in buddy system, and
>  		 * page_count() is not 0.
>  		 */
> -		if (unlikely(!PageBuddy(page) && PageHWPoison(page))) {
> +		if (unlikely(!PageBuddy(page) && TestClearPageHWPoison(page))) {
>  			pfn++;
> +			num_poisoned_pages_dec();
>  			SetPageReserved(page);
>  			continue;
>  		}

Kbuild test robot shows that this patch causes build errors on
!CONFIG_MEMORY_FAILURE, which should be fixed by the following changes.

Thanks,
Naoya Horiguchi
---
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6c496dab246d..559092915fe6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2785,6 +2785,10 @@ static inline void num_poisoned_pages_dec(void)
 {
 	atomic_long_dec(&num_poisoned_pages);
 }
+#else
+static inline void num_poisoned_pages_dec(void)
+{
+}
 #endif
 
 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index ab0bde073050..1461384aa1a3 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -385,6 +385,7 @@ extern bool set_hwpoison_free_buddy_page(struct page *page);
 extern bool clear_hwpoison_free_buddy_page(struct page *page);
 #else
 PAGEFLAG_FALSE(HWPoison)
+TESTCLEARFLAG_FALSE(HWPoison)
 static inline bool set_hwpoison_free_buddy_page(struct page *page)
 {
 	return false;