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 <n-horiguchi@ah.jp.nec.com>
Reported-by: Xishi Qiu <xishi.qiuxishi@alibaba-inc.com>
Tested-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: <zy.zhengyi@alibaba-inc.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c677c1506d73..e75865d58ba7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8096,3 +8096,33 @@ bool is_free_buddy_page(struct page *page)
 
         return order < MAX_ORDER;
 }
+
+#ifdef CONFIG_MEMORY_FAILURE
+/*
+ * Set PG_hwpoison flag if a given page is confirmed to be a free page.  This
+ * test is performed under the zone lock to prevent a race against page
+ * allocation.
+ */
+bool set_hwpoison_free_buddy_page(struct page *page)
+{
+        struct zone *zone = page_zone(page);
+        unsigned long pfn = page_to_pfn(page);
+        unsigned long flags;
+        unsigned int order;
+        bool hwpoisoned = false;
+
+        spin_lock_irqsave(&zone->lock, flags);
+        for (order = 0; order < MAX_ORDER; order++) {
+                struct page *page_head = page - (pfn & ((1 << order) - 1));
+
+                if (PageBuddy(page_head) && page_order(page_head) >= order) {
+                        if (!TestSetPageHWPoison(page))
+                                hwpoisoned = true;
+                        break;
+                }
+        }
+        spin_unlock_irqrestore(&zone->lock, flags);
+
+        return hwpoisoned;
+}
+#endif