[RFC 06/11] mm: remove SWAP_MLOCK in ttu

Minchan Kim
2017-03-02T06:39:32Z

ttu don't need to return SWAP_MLOCK. Instead, just return SWAP_FAIL
because it means the page is not-swappable so it should move to
another LRU list(active or unevictable). putback friends will
move it to right list depending on the page's LRU flag.

A side effect is shrink_page_list accounts unevictable list movement
by PGACTIVATE but I don't think it corrupts something severe.

Signed-off-by: Minchan Kim <minchan@kernel.org>
---
include/linux/rmap.h | 1 -
mm/rmap.c | 3 +--
mm/vmscan.c | 14 +++-----------
3 files changed, 4 insertions(+), 14 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 1b0cd4c..3630d4d 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -297,6 +297,5 @@ static inline int page_mkclean(struct page *page)
#define SWAP_SUCCESS 0
#define SWAP_AGAIN 1
#define SWAP_FAIL 2
-#define SWAP_MLOCK 3

#endif /* _LINUX_RMAP_H */
diff --git a/mm/rmap.c b/mm/rmap.c
index 61ae694..47898a1 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1328,7 +1328,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
*/
mlock_vma_page(page);
}
- ret = SWAP_MLOCK;
+ ret = SWAP_FAIL;
page_vma_mapped_walk_done(&pvmw);
break;
}
@@ -1494,7 +1494,6 @@ static int page_mapcount_is_zero(struct page *page)
* SWAP_SUCCESS - we succeeded in removing all mappings
* SWAP_AGAIN - we missed a mapping, try again later
* SWAP_FAIL - the page is unswappable
- * SWAP_MLOCK - page is mlocked.
*/
int try_to_unmap(struct page *page, enum ttu_flags flags)
{
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 91cef05..3cdd270b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -981,7 +981,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
sc->nr_scanned++;

if (unlikely(!page_evictable(page)))
- goto cull_mlocked;
+ goto activate_locked;

if (!sc->may_unmap && page_mapped(page))
goto keep_locked;
@@ -1146,8 +1146,6 @@ static unsigned long shrink_page_list(struct list_head *page_list,
goto activate_locked;
case SWAP_AGAIN:
goto keep_locked;
- case SWAP_MLOCK:
- goto cull_mlocked;
case SWAP_SUCCESS:
; /* try to free the page below */
}
@@ -1289,16 +1287,10 @@ static unsigned long shrink_page_list(struct list_head *page_list,
list_add(&page->lru, &free_pages);
continue;

-cull_mlocked:
- if (PageSwapCache(page))
- try_to_free_swap(page);
- unlock_page(page);
- list_add(&page->lru, &ret_pages);
- continue;
-
activate_locked:
/* Not a candidate for swapping, so reclaim swap space. */
- if (PageSwapCache(page) && mem_cgroup_swap_full(page))
+ if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
+ PageMlocked(page)))
try_to_free_swap(page);
VM_BUG_ON_PAGE(PageActive(page), page);
SetPageActive(page);
--
2.7.4