[RFC 08/11] mm: make ttu's return boolean

[Minchan Kim]

try_to_unmap returns SWAP_SUCCESS or SWAP_FAIL so it's suitable for
boolean return. This patch changes it.

Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
 include/linux/rmap.h |  4 ++--
 mm/huge_memory.c     |  4 ++--
 mm/memory-failure.c  | 22 ++++++++++------------
 mm/rmap.c            |  8 +++-----
 mm/vmscan.c          |  7 +------
 5 files changed, 18 insertions(+), 27 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 3630d4d..6028c38 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -191,7 +191,7 @@ static inline void page_dup_rmap(struct page *page, bool compound)
 int page_referenced(struct page *, int is_locked,
 			struct mem_cgroup *memcg, unsigned long *vm_flags);
 
-int try_to_unmap(struct page *, enum ttu_flags flags);
+bool try_to_unmap(struct page *, enum ttu_flags flags);
 
 /* Avoid racy checks */
 #define PVMW_SYNC		(1 << 0)
@@ -281,7 +281,7 @@ static inline int page_referenced(struct page *page, int is_locked,
 	return 0;
 }
 
-#define try_to_unmap(page, refs) SWAP_FAIL
+#define try_to_unmap(page, refs) false
 
 static inline int page_mkclean(struct page *page)
 {
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index fe2ccd4..79ea769 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2106,7 +2106,7 @@ static void freeze_page(struct page *page)
 {
 	enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
 		TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
-	int ret;
+	bool ret;
 
 	VM_BUG_ON_PAGE(!PageHead(page), page);
 
@@ -2114,7 +2114,7 @@ static void freeze_page(struct page *page)
 		ttu_flags |= TTU_MIGRATION;
 
 	ret = try_to_unmap(page, ttu_flags);
-	VM_BUG_ON_PAGE(ret != SWAP_SUCCESS, page);
+	VM_BUG_ON_PAGE(!ret, page);
 }
 
 static void unfreeze_page(struct page *page)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b78d080..75fcbd8 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -321,7 +321,7 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
  * wrong earlier.
  */
 static void kill_procs(struct list_head *to_kill, int forcekill, int trapno,
-			  int fail, struct page *page, unsigned long pfn,
+			  bool fail, struct page *page, unsigned long pfn,
 			  int flags)
 {
 	struct to_kill *tk, *next;
@@ -903,13 +903,13 @@ EXPORT_SYMBOL_GPL(get_hwpoison_page);
  * Do all that is necessary to remove user space mappings. Unmap
  * the pages and send SIGBUS to the processes if the data was dirty.
  */
-static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
+static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
 				  int trapno, int flags, struct page **hpagep)
 {
 	enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
 	struct address_space *mapping;
 	LIST_HEAD(tokill);
-	int ret;
+	bool ret;
 	int kill = 1, forcekill;
 	struct page *hpage = *hpagep;
 
@@ -918,20 +918,20 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 	 * other types of pages.
 	 */
 	if (PageReserved(p) || PageSlab(p))
-		return SWAP_SUCCESS;
+		return true;
 	if (!(PageLRU(hpage) || PageHuge(p)))
-		return SWAP_SUCCESS;
+		return true;
 
 	/*
 	 * This check implies we don't kill processes if their pages
 	 * are in the swap cache early. Those are always late kills.
 	 */
 	if (!page_mapped(hpage))
-		return SWAP_SUCCESS;
+		return true;
 
 	if (PageKsm(p)) {
 		pr_err("Memory failure: %#lx: can't handle KSM pages.\n", pfn);
-		return SWAP_FAIL;
+		return false;
 	}
 
 	if (PageSwapCache(p)) {
@@ -971,7 +971,7 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 		collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED);
 
 	ret = try_to_unmap(hpage, ttu);
-	if (ret != SWAP_SUCCESS)
+	if (!ret)
 		pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n",
 		       pfn, page_mapcount(hpage));
 
@@ -986,8 +986,7 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 	 * any accesses to the poisoned memory.
 	 */
 	forcekill = PageDirty(hpage) || (flags & MF_MUST_KILL);
-	kill_procs(&tokill, forcekill, trapno,
-		      ret != SWAP_SUCCESS, p, pfn, flags);
+	kill_procs(&tokill, forcekill, trapno, !ret , p, pfn, flags);
 
 	return ret;
 }
@@ -1229,8 +1228,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 	 * When the raw error page is thp tail page, hpage points to the raw
 	 * page after thp split.
 	 */
-	if (hwpoison_user_mappings(p, pfn, trapno, flags, &hpage)
-	    != SWAP_SUCCESS) {
+	if (!hwpoison_user_mappings(p, pfn, trapno, flags, &hpage)) {
 		action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
 		res = -EBUSY;
 		goto out;
diff --git a/mm/rmap.c b/mm/rmap.c
index da18f21..01f7832 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1489,12 +1489,10 @@ static int page_mapcount_is_zero(struct page *page)
  *
  * Tries to remove all the page table entries which are mapping this
  * page, used in the pageout path.  Caller must hold the page lock.
- * Return values are:
  *
- * SWAP_SUCCESS	- we succeeded in removing all mappings
- * SWAP_FAIL	- the page is unswappable
+ * If unmap is successful, return true. Otherwise, false.
  */
-int try_to_unmap(struct page *page, enum ttu_flags flags)
+bool try_to_unmap(struct page *page, enum ttu_flags flags)
 {
 	struct rmap_walk_control rwc = {
 		.rmap_one = try_to_unmap_one,
@@ -1519,7 +1517,7 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
 	else
 		rmap_walk(page, &rwc);
 
-	return !page_mapcount(page) ? SWAP_SUCCESS: SWAP_FAIL;
+	return !page_mapcount(page) ? true: false;
 }
 
 static int page_not_mapped(struct page *page)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 170c61f..e4b74f1 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -966,7 +966,6 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		int may_enter_fs;
 		enum page_references references = PAGEREF_RECLAIM_CLEAN;
 		bool dirty, writeback;
-		int ret = SWAP_SUCCESS;
 
 		cond_resched();
 
@@ -1139,13 +1138,9 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		 * processes. Try to unmap it here.
 		 */
 		if (page_mapped(page)) {
-			switch (ret = try_to_unmap(page,
-				ttu_flags | TTU_BATCH_FLUSH)) {
-			case SWAP_FAIL:
+			if (!try_to_unmap(page, ttu_flags | TTU_BATCH_FLUSH)) {
 				nr_unmap_fail++;
 				goto activate_locked;
-			case SWAP_SUCCESS:
-				; /* try to free the page below */
 			}
 		}
 
-- 
2.7.4