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>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index c6e4dd3..1a9242c 100644 (file)
--- 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;
 }