mm: memory-failure: avoid false hwpoison page mapped error info

folio->_mapcount is overloaded in SLAB, so folio_mapped() has to be done
after folio_test_slab() is checked. Otherwise slab folio might be treated
as a mapped folio leading to false 'Someone maps the hwpoison page' error
info.

Link: https://lkml.kernel.org/r/20230727115643.639741-4-linmiaohe@huawei.com
Fixes: 230ac719c500 ("mm/hwpoison: don't try to unpoison containment-failed pages")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b32d370b5d43987b1aa0ada9b420b85ce1965b6b..9a285038d7658cbfda1ade9c55c6c96502f258fb 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2499,6 +2499,13 @@ int unpoison_memory(unsigned long pfn)
                goto unlock_mutex;
        }
 
+       if (folio_test_slab(folio) || PageTable(&folio->page) || folio_test_reserved(folio))
+               goto unlock_mutex;
+
+       /*
+        * Note that folio->_mapcount is overloaded in SLAB, so the simple test
+        * in folio_mapped() has to be done after folio_test_slab() is checked.
+        */
        if (folio_mapped(folio)) {
                unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n",
                                 pfn, &unpoison_rs);
@@ -2511,9 +2518,6 @@ int unpoison_memory(unsigned long pfn)
                goto unlock_mutex;
        }
 
-       if (folio_test_slab(folio) || PageTable(&folio->page) || folio_test_reserved(folio))
-               goto unlock_mutex;
-
        ghp = get_hwpoison_page(p, MF_UNPOISON);
        if (!ghp) {
                if (PageHuge(p)) {