linux-kernel - [PATCH v1 02/10] mm: remove SWAP

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Date:   Mon, 13 Mar 2017 09:35:45 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <kernel-team@....com>, Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        Minchan Kim <minchan@...nel.org>
Subject: [PATCH v1 02/10] mm: remove SWAP_DIRTY in ttu

If we found lazyfree page is dirty, try_to_unmap_one 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.

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Signed-off-by: Minchan Kim <minchan@...nel.org>
---
 include/linux/rmap.h | 1 -
 mm/rmap.c            | 6 +++---
 mm/vmscan.c          | 3 ---
 3 files changed, 3 insertions(+), 7 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 9dbfa6f..d47af09 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1414,7 +1414,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 			 */
 			if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) {
 				WARN_ON_ONCE(1);
-				ret = SWAP_FAIL;
+				ret = false;
 				page_vma_mapped_walk_done(&pvmw);
 				break;
 			}
@@ -1431,7 +1431,8 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 				 * discarded. Remap the page to page table.
 				 */
 				set_pte_at(mm, address, pvmw.pte, pteval);
-				ret = SWAP_DIRTY;
+				SetPageSwapBacked(page);
+				ret = SWAP_FAIL;
 				page_vma_mapped_walk_done(&pvmw);
 				break;
 			}
@@ -1501,7 +1502,6 @@ 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 a3656f9..b8fd656 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1142,9 +1142,6 @@ 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