[RFC 03/11] mm: remove SWAP_DIRTY in ttu

Minchan Kim
2017-03-02T06:39:33Z

If we found lazyfree page is dirty, ttuo can just SetPageSwapBakced
in there like PG_mlocked page and just return with SWAP_FAIL which
is very natural because the page is not swappable right now so that
vmscan can activate it. There is no point to introduce new return
value SWAP_DIRTY in ttu at the moment.

Cc: Shaohua Li <shli@kernel.org>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
include/linux/rmap.h | 1 -
mm/rmap.c | 4 ++--
mm/vmscan.c | 3 ---
3 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index fee10d7..b556eef 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -298,6 +298,5 @@ static inline int page_mkclean(struct page *page)
#define SWAP_AGAIN 1
#define SWAP_FAIL 2
#define SWAP_MLOCK 3
-#define SWAP_DIRTY 4

#endif /* _LINUX_RMAP_H */
diff --git a/mm/rmap.c b/mm/rmap.c
index 8076347..3a14013 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1424,7 +1424,8 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
} else if (!PageSwapBacked(page)) {
/* dirty MADV_FREE page */
set_pte_at(mm, address, pvmw.pte, pteval);
- ret = SWAP_DIRTY;
+ SetPageSwapBacked(page);
+ ret = SWAP_FAIL;
page_vma_mapped_walk_done(&pvmw);
break;
}
@@ -1494,7 +1495,6 @@ static int page_mapcount_is_zero(struct page *page)
* SWAP_AGAIN - we missed a mapping, try again later
* SWAP_FAIL - the page is unswappable
* SWAP_MLOCK - page is mlocked.
- * SWAP_DIRTY - page is dirty MADV_FREE page
*/
int try_to_unmap(struct page *page, enum ttu_flags flags)
{
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7aa89e3..91cef05 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1141,9 +1141,6 @@ static unsigned long shrink_page_list(struct list_head *page_list,
if (page_mapped(page)) {
switch (ret = try_to_unmap(page,
ttu_flags | TTU_BATCH_FLUSH)) {
- case SWAP_DIRTY:
- SetPageSwapBacked(page);
- /* fall through */
case SWAP_FAIL:
nr_unmap_fail++;
goto activate_locked;
--
2.7.4