mm/migration: make isolate_movable_page() return int type

Patch series "HWPOISON: soft offlining for non-lru movable page", v6.

After Minchan's commit bda807d44454 ("mm: migrate: support non-lru movable
page migration"), some type of non-lru page like zsmalloc and
virtio-balloon page also support migration.

Therefore, we can:

1) soft offlining no-lru movable pages, which means when memory
   corrected errors occur on a non-lru movable page, we can stop to use it
   by migrating data onto another page and disable the original (maybe
   half-broken) one.

2) enable memory hotplug for non-lru movable pages, i.e.  we may
   offline blocks, which include such pages, by using non-lru page
   migration.

This patchset is heavily dependent on non-lru movable page migration.

This patch (of 4):

Change the return type of isolate_movable_page() from bool to int.  It
will return 0 when isolate movable page successfully, and return -EBUSY
when it isolates failed.

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

Link: http://lkml.kernel.org/r/1485867981-16037-2-git-send-email-ysxie@foxmail.com
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Suggested-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

3 files changed, 9 insertions, 6 deletions

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index ae8d475a9385..43d5deb0c4cc 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 0aa2757399ee..0fdfde016ee2 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -802,7 +802,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 					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 87f4d0f81819..bbbd170efab7 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 */