| Message ID | 20230927094401.68205-1-shikemeng@huaweicloud.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/page_alloc: correct start page when guard page debug is enabled | expand |
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 191e552a4c83..e18e0e20eff8 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6691,6 +6691,7 @@ static void break_down_buddy_pages(struct zone *zone, struct page *page, next_page = page; current_buddy = page + size; } + page = next_page; if (set_page_guard(zone, current_buddy, high, migratetype)) continue; @@ -6698,7 +6699,6 @@ static void break_down_buddy_pages(struct zone *zone, struct page *page, if (current_buddy != target) { add_to_free_list(current_buddy, zone, high, migratetype); set_buddy_order(current_buddy, high); - page = next_page; } } }
When guard page debug is enabled and set_page_guard returns success, we miss to forward page to point to start of next split range and we will do split unexpectedly in page range without target page. Move start page update before set_page_guard to fix this. As we split to wrong target page, then splited pages are not able to merge back to original order when target page is put back and splited pages except target page is not usable. To be specific: Consider target page is the third page in buddy page with order 2. | buddy-2 | Page | Target | Page | After break down to target page, we will only set first page to Guard because of bug. | Guard | Page | Target | Page | When we try put_page_back_buddy with target page, the buddy page of target if neither guard nor buddy, Then it's not able to construct original page with order 2 | Guard | Page | buddy-0 | Page | All pages except target page is not in free list and is not usable. Fixes: 06be6ff3d2ec ("mm,hwpoison: rework soft offline for free pages") Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com> Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com> Cc: stable@vger.kernel.org --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)