[PATCH v2 11/18] zsmalloc: separate free_zspage from putback_zspage

[Minchan Kim]

Currently, putback_zspage does free zspage under class->lock
if fullness become ZS_EMPTY but it makes trouble to implement
locking scheme for new zspage migration.
So, this patch is to separate free_zspage from putback_zspage
and free zspage out of class->lock which is preparation for
zspage migration.

Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
 mm/zsmalloc.c | 46 +++++++++++++++++++++++-----------------------
 1 file changed, 23 insertions(+), 23 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 833da8f4ffc9..9c0ab1e92e9b 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -950,7 +950,8 @@ static void reset_page(struct page *page)
 	page_mapcount_reset(page);
 }
 
-static void free_zspage(struct page *first_page)
+static void free_zspage(struct zs_pool *pool, struct size_class *class,
+			struct page *first_page)
 {
 	struct page *nextp, *tmp, *head_extra;
 
@@ -973,6 +974,11 @@ static void free_zspage(struct page *first_page)
 	}
 	reset_page(head_extra);
 	__free_page(head_extra);
+
+	zs_stat_dec(class, OBJ_ALLOCATED, get_maxobj_per_zspage(
+			class->size, class->pages_per_zspage));
+	atomic_long_sub(class->pages_per_zspage,
+				&pool->pages_allocated);
 }
 
 /* Initialize a newly allocated zspage */
@@ -1560,13 +1566,8 @@ void zs_free(struct zs_pool *pool, unsigned long handle)
 	spin_lock(&class->lock);
 	obj_free(class, obj);
 	fullness = fix_fullness_group(class, first_page);
-	if (fullness == ZS_EMPTY) {
-		zs_stat_dec(class, OBJ_ALLOCATED, get_maxobj_per_zspage(
-				class->size, class->pages_per_zspage));
-		atomic_long_sub(class->pages_per_zspage,
-				&pool->pages_allocated);
-		free_zspage(first_page);
-	}
+	if (fullness == ZS_EMPTY)
+		free_zspage(pool, class, first_page);
 	spin_unlock(&class->lock);
 	unpin_tag(handle);
 
@@ -1753,7 +1754,7 @@ static struct page *isolate_target_page(struct size_class *class)
  * @class: destination class
  * @first_page: target page
  *
- * Return @fist_page's fullness_group
+ * Return @first_page's updated fullness_group
  */
 static enum fullness_group putback_zspage(struct zs_pool *pool,
 			struct size_class *class,
@@ -1765,15 +1766,6 @@ static enum fullness_group putback_zspage(struct zs_pool *pool,
 	insert_zspage(class, fullness, first_page);
 	set_zspage_mapping(first_page, class->index, fullness);
 
-	if (fullness == ZS_EMPTY) {
-		zs_stat_dec(class, OBJ_ALLOCATED, get_maxobj_per_zspage(
-			class->size, class->pages_per_zspage));
-		atomic_long_sub(class->pages_per_zspage,
-				&pool->pages_allocated);
-
-		free_zspage(first_page);
-	}
-
 	return fullness;
 }
 
@@ -1836,23 +1828,31 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class)
 			if (!migrate_zspage(pool, class, &cc))
 				break;
 
-			putback_zspage(pool, class, dst_page);
+			VM_BUG_ON_PAGE(putback_zspage(pool, class,
+				dst_page) == ZS_EMPTY, dst_page);
 		}
 
 		/* Stop if we couldn't find slot */
 		if (dst_page == NULL)
 			break;
 
-		putback_zspage(pool, class, dst_page);
-		if (putback_zspage(pool, class, src_page) == ZS_EMPTY)
+		VM_BUG_ON_PAGE(putback_zspage(pool, class,
+				dst_page) == ZS_EMPTY, dst_page);
+		if (putback_zspage(pool, class, src_page) == ZS_EMPTY) {
 			pool->stats.pages_compacted += class->pages_per_zspage;
-		spin_unlock(&class->lock);
+			spin_unlock(&class->lock);
+			free_zspage(pool, class, src_page);
+		} else {
+			spin_unlock(&class->lock);
+		}
+
 		cond_resched();
 		spin_lock(&class->lock);
 	}
 
 	if (src_page)
-		putback_zspage(pool, class, src_page);
+		VM_BUG_ON_PAGE(putback_zspage(pool, class,
+				src_page) == ZS_EMPTY, src_page);
 
 	spin_unlock(&class->lock);
 }
-- 
1.9.1