memory-failure: fix an error of mce_bad_pages statistics

When doing

    $ echo paddr > /sys/devices/system/memory/soft_offline_page

to offline a *free* page, the value of mce_bad_pages will be added, and
the page is set HWPoison flag, but it is still managed by page buddy
alocator.

   $ cat /proc/meminfo | grep HardwareCorrupted

shows the value.

If we offline the same page, the value of mce_bad_pages will be added
*again*, this means the value is incorrect now.  Assume the page is
still free during this short time.

  soft_offline_page()
    get_any_page()
      "else if (is_free_buddy_page(p))" branch return 0
        "goto done";
           "atomic_long_add(1, &mce_bad_pages);"

This patch:

Move poisoned page check at the beginning of the function in order to
fix the error.

Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Tested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 21 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index c6e4dd3e1c08..1a9242c53315 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1419,18 +1419,17 @@ static int soft_offline_huge_page(struct page *page, int flags)
         unsigned long pfn = page_to_pfn(page);
         struct page *hpage = compound_head(page);
 
+        if (PageHWPoison(hpage)) {
+                pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
+                return -EBUSY;
+        }
+
         ret = get_any_page(page, pfn, flags);
         if (ret < 0)
                 return ret;
         if (ret == 0)
                 goto done;
 
-        if (PageHWPoison(hpage)) {
-                put_page(hpage);
-                pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
-                return -EBUSY;
-        }
-
         /* Keep page count to indicate a given hugepage is isolated. */
         ret = migrate_huge_page(hpage, new_page, MPOL_MF_MOVE_ALL, false,
                                 MIGRATE_SYNC);
@@ -1441,12 +1440,11 @@ static int soft_offline_huge_page(struct page *page, int flags)
                 return ret;
         }
 done:
-        if (!PageHWPoison(hpage))
-                atomic_long_add(1 << compound_trans_order(hpage),
-                                &mce_bad_pages);
+        /* keep elevated page count for bad page */
+        atomic_long_add(1 << compound_trans_order(hpage), &mce_bad_pages);
         set_page_hwpoison_huge_page(hpage);
         dequeue_hwpoisoned_huge_page(hpage);
-        /* keep elevated page count for bad page */
+
         return ret;
 }
 
@@ -1488,6 +1486,11 @@ int soft_offline_page(struct page *page, int flags)
                 }
         }
 
+        if (PageHWPoison(page)) {
+                pr_info("soft offline: %#lx page already poisoned\n", pfn);
+                return -EBUSY;
+        }
+
         ret = get_any_page(page, pfn, flags);
         if (ret < 0)
                 return ret;
@@ -1519,19 +1522,11 @@ int soft_offline_page(struct page *page, int flags)
                 return -EIO;
         }
 
-        lock_page(page);
-        wait_on_page_writeback(page);
-
         /*
          * Synchronized using the page lock with memory_failure()
          */
-        if (PageHWPoison(page)) {
-                unlock_page(page);
-                put_page(page);
-                pr_info("soft offline: %#lx page already poisoned\n", pfn);
-                return -EBUSY;
-        }
-
+        lock_page(page);
+        wait_on_page_writeback(page);
         /*
          * Try to invalidate first. This should work for
          * non dirty unmapped page cache pages.
@@ -1583,8 +1578,9 @@ int soft_offline_page(struct page *page, int flags)
                 return ret;
 
 done:
+        /* keep elevated page count for bad page */
         atomic_long_add(1, &mce_bad_pages);
         SetPageHWPoison(page);
-        /* keep elevated page count for bad page */
+
         return ret;
 }