path: root/arch/s390
diff options
authorJan Kara <jack@suse.cz>2012-12-11 16:01:09 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-11 17:22:23 -0800
commite749eb95531ac8349df47f8d46ce2641dcb16589 (patch)
treec78428ed9c92bf0e4915f6dfa6a21d4e58e14465 /arch/s390
parent712cd386fdc983d318fecf302a2a9cb8e9de90c9 (diff)
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 <jack@suse.cz> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/s390')
1 files changed, 3 insertions, 0 deletions
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.
static inline int page_test_and_clear_dirty(unsigned long pfn, int mapped)