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>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b62287d..dc47415 100644 (file)
--- 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.
        /*
         * 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)) {
         */
        mapping = page_mapping(p);
        if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) {