mm, hwpoison: avoid trying to unpoison reserved page

For reserved pages, HWPoison flag will be set without increasing the page
refcnt.  So we shouldn't even try to unpoison these pages and thus
decrease the page refcnt unexpectly.  Add a PageReserved() check to filter
this case out and remove the below unneeded zero page (zero page is
reserved) check.

Link: https://lkml.kernel.org/r/20220818130016.45313-7-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index aba275bbf07ed3b91c7229a87057463356a0251c..869e0c241e045327d4df505a8794c3a4fe22ded3 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2351,7 +2351,7 @@ int unpoison_memory(unsigned long pfn)
                goto unlock_mutex;
        }
 
-       if (PageSlab(page) || PageTable(page))
+       if (PageSlab(page) || PageTable(page) || PageReserved(page))
                goto unlock_mutex;
 
        ret = get_hwpoison_page(p, MF_UNPOISON);
@@ -2382,7 +2382,7 @@ int unpoison_memory(unsigned long pfn)
                freeit = !!TestClearPageHWPoison(p);
 
                put_page(page);
-               if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1)) {
+               if (freeit) {
                        put_page(page);
                        ret = 0;
                }