[PATCH v5 1/4] mm/migration: make isolate_movable_page() return int type

[ysxie]

From: Yisheng Xie <xieyisheng1@xxxxxxxxxx>

This patch changes the return type of isolate_movable_page()
from bool to int. It will return 0 when isolate movable page
successfully, return -EINVAL when the page is not a non-lru movable
page, and for other cases it will return -EBUSY.

There is no functional change within this patch but prepare
for later patch.

Signed-off-by: Yisheng Xie <xieyisheng1@xxxxxxxxxx>
Suggested-by: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
CC: Vlastimil Babka <vbabka@xxxxxxx>
---
 include/linux/migrate.h |  2 +-
 mm/compaction.c         |  2 +-
 mm/migrate.c            | 11 +++++++----
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index ae8d475..43d5deb 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -37,7 +37,7 @@ extern int migrate_page(struct address_space *,
 			struct page *, struct page *, enum migrate_mode);
 extern int migrate_pages(struct list_head *l, new_page_t new, free_page_t free,
 		unsigned long private, enum migrate_mode mode, int reason);
-extern bool isolate_movable_page(struct page *page, isolate_mode_t mode);
+extern int isolate_movable_page(struct page *page, isolate_mode_t mode);
 extern void putback_movable_page(struct page *page);
 
 extern int migrate_prep(void);
diff --git a/mm/compaction.c b/mm/compaction.c
index 949198d..1d89147 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -802,7 +802,7 @@ static bool too_many_isolated(struct zone *zone)
 					locked = false;
 				}
 
-				if (isolate_movable_page(page, isolate_mode))
+				if (!isolate_movable_page(page, isolate_mode))
 					goto isolate_success;
 			}
 
diff --git a/mm/migrate.c b/mm/migrate.c
index 87f4d0f..bbbd170 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -74,8 +74,9 @@ int migrate_prep_local(void)
 	return 0;
 }
 
-bool isolate_movable_page(struct page *page, isolate_mode_t mode)
+int isolate_movable_page(struct page *page, isolate_mode_t mode)
 {
+	int ret = -EBUSY;
 	struct address_space *mapping;
 
 	/*
@@ -95,8 +96,10 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode)
 	 * assumes anybody doesn't touch PG_lock of newly allocated page
 	 * so unconditionally grapping the lock ruins page's owner side.
 	 */
-	if (unlikely(!__PageMovable(page)))
+	if (unlikely(!__PageMovable(page))) {
+		ret = -EINVAL;
 		goto out_putpage;
+	}
 	/*
 	 * As movable pages are not isolated from LRU lists, concurrent
 	 * compaction threads can race against page migration functions
@@ -125,14 +128,14 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode)
 	__SetPageIsolated(page);
 	unlock_page(page);
 
-	return true;
+	return 0;
 
 out_no_isolated:
 	unlock_page(page);
 out_putpage:
 	put_page(page);
 out:
-	return false;
+	return ret;
 }
 
 /* It should be called on page which is PG_movable */
-- 
1.9.1