HWPOISON: comment the possible set_page_dirty() race

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b62287db87af..dc47415a5511 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -687,6 +687,8 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
         /*
          * Propagate the dirty bit from PTEs to struct page first, because we
          * need this to decide if we should kill or just drop the page.
+         * XXX: the dirty test could be racy: set_page_dirty() may not always
+         * be called inside page lock (it's recommended but not enforced).
          */
         mapping = page_mapping(p);
         if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) {