mm: add comment on storage key dirty bit semantics

[can-eth-gw-linux.git] / arch / s390 / include / asm / page.h

diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 6d5367060a5656a92d5d1b95f28dc3097fa47e78..39faa4ac966075298ea1d6fb1843d9c85cf792a5 100644 (file)
--- a/arch/s390/include/asm/page.h
+++ b/arch/s390/include/asm/page.h
@@ -158,6 +158,9 @@ static inline int page_reset_referenced(unsigned long addr)
  * race against modification of the referenced bit. This function
  * should therefore only be called if it is not mapped in any
  * address space.
+ *
+ * Note that the bit gets set whenever page content is changed. That means
+ * also when the page is modified by DMA or from inside the kernel.
  */
 #define __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY
 static inline int page_test_and_clear_dirty(unsigned long pfn, int mapped)