From e749eb95531ac8349df47f8d46ce2641dcb16589 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 11 Dec 2012 16:01:09 -0800 Subject: mm: add comment on storage key dirty bit semantics Add comments that dirty bit in storage key gets set whenever page content is changed. Hopefully if someone will use this function, he'll have a look at one of the two places where we comment on this. Signed-off-by: Jan Kara Cc: Martin Schwidefsky Cc: Mel Gorman Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/s390/include/asm/page.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/s390') diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h index 6d5367060a5..39faa4ac966 100644 --- 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) -- cgit v1.2.3-70-g09d2