From d4ae9916ea2947341180d2b538f48875ff393a86 Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Thu, 23 Aug 2018 17:00:42 -0700 Subject: mm: soft-offline: close the race against page allocation A process can be killed with SIGBUS(BUS_MCEERR_AR) when it tries to allocate a page that was just freed on the way of soft-offline. This is undesirable because soft-offline (which is about corrected error) is less aggressive than hard-offline (which is about uncorrected error), and we can make soft-offline fail and keep using the page for good reason like "system is busy." Two main changes of this patch are: - setting migrate type of the target page to MIGRATE_ISOLATE. As done in free_unref_page_commit(), this makes kernel bypass pcplist when freeing the page. So we can assume that the page is in freelist just after put_page() returns, - setting PG_hwpoison on free page under zone->lock which protects freelists, so this allows us to avoid setting PG_hwpoison on a page that is decided to be allocated soon. [akpm@linux-foundation.org: tweak set_hwpoison_free_buddy_page() comment] Link: http://lkml.kernel.org/r/1531452366-11661-3-git-send-email-n-horiguchi@ah.jp.nec.com Signed-off-by: Naoya Horiguchi Reported-by: Xishi Qiu Tested-by: Mike Kravetz Cc: Michal Hocko Cc: Cc: Mike Kravetz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/migrate.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm/migrate.c') diff --git a/mm/migrate.c b/mm/migrate.c index 91a99457127c..d6a2e89b086a 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1212,7 +1212,7 @@ out: * intentionally. Although it's rather weird, * it's how HWPoison flag works at the moment. */ - if (!test_set_page_hwpoison(page)) + if (set_hwpoison_free_buddy_page(page)) num_poisoned_pages_inc(); } } else { -- cgit v1.2.1