[PATCHv2 1/7] zsmalloc: factor out pool locking helpers

[Sergey Senozhatsky <senozhatsky@chromium.org>]

We currently have a mix of migrate_{read,write}_lock() helpers
that lock zspages, but it's zs_pool that actually has a ->migrate_lock
access to which is opene-coded.  Factor out pool migrate locking
into helpers, zspage migration locking API will be renamed to
reduce confusion.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 mm/zsmalloc.c | 47 ++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 36 insertions(+), 11 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 6d0e47f7ae33..8972b4b56cd3 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -228,6 +228,31 @@ struct zs_pool {
 	atomic_t compaction_in_progress;
 };
 
+static void pool_write_unlock(struct zs_pool *pool)
+{
+	write_unlock(&pool->migrate_lock);
+}
+
+static void pool_write_lock(struct zs_pool *pool)
+{
+	write_lock(&pool->migrate_lock);
+}
+
+static void pool_read_unlock(struct zs_pool *pool)
+{
+	read_unlock(&pool->migrate_lock);
+}
+
+static void pool_read_lock(struct zs_pool *pool)
+{
+	read_lock(&pool->migrate_lock);
+}
+
+static bool pool_lock_is_contended(struct zs_pool *pool)
+{
+	return rwlock_is_contended(&pool->migrate_lock);
+}
+
 static inline void zpdesc_set_first(struct zpdesc *zpdesc)
 {
 	SetPagePrivate(zpdesc_page(zpdesc));
@@ -1206,7 +1231,7 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle,
 	BUG_ON(in_interrupt());
 
 	/* It guarantees it can get zspage from handle safely */
-	read_lock(&pool->migrate_lock);
+	pool_read_lock(pool);
 	obj = handle_to_obj(handle);
 	obj_to_location(obj, &zpdesc, &obj_idx);
 	zspage = get_zspage(zpdesc);
@@ -1218,7 +1243,7 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle,
 	 * which is smaller granularity.
 	 */
 	migrate_read_lock(zspage);
-	read_unlock(&pool->migrate_lock);
+	pool_read_unlock(pool);
 
 	class = zspage_class(pool, zspage);
 	off = offset_in_page(class->size * obj_idx);
@@ -1453,13 +1478,13 @@ void zs_free(struct zs_pool *pool, unsigned long handle)
 	 * The pool->migrate_lock protects the race with zpage's migration
 	 * so it's safe to get the page from handle.
 	 */
-	read_lock(&pool->migrate_lock);
+	pool_read_lock(pool);
 	obj = handle_to_obj(handle);
 	obj_to_zpdesc(obj, &f_zpdesc);
 	zspage = get_zspage(f_zpdesc);
 	class = zspage_class(pool, zspage);
 	spin_lock(&class->lock);
-	read_unlock(&pool->migrate_lock);
+	pool_read_unlock(pool);
 
 	class_stat_sub(class, ZS_OBJS_INUSE, 1);
 	obj_free(class->size, obj);
@@ -1796,7 +1821,7 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
 	 * The pool migrate_lock protects the race between zpage migration
 	 * and zs_free.
 	 */
-	write_lock(&pool->migrate_lock);
+	pool_write_lock(pool);
 	class = zspage_class(pool, zspage);
 
 	/*
@@ -1833,7 +1858,7 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
 	 * Since we complete the data copy and set up new zspage structure,
 	 * it's okay to release migration_lock.
 	 */
-	write_unlock(&pool->migrate_lock);
+	pool_write_unlock(pool);
 	spin_unlock(&class->lock);
 	migrate_write_unlock(zspage);
 
@@ -1956,7 +1981,7 @@ static unsigned long __zs_compact(struct zs_pool *pool,
 	 * protect the race between zpage migration and zs_free
 	 * as well as zpage allocation/free
 	 */
-	write_lock(&pool->migrate_lock);
+	pool_write_lock(pool);
 	spin_lock(&class->lock);
 	while (zs_can_compact(class)) {
 		int fg;
@@ -1983,14 +2008,14 @@ static unsigned long __zs_compact(struct zs_pool *pool,
 		src_zspage = NULL;
 
 		if (get_fullness_group(class, dst_zspage) == ZS_INUSE_RATIO_100
-		    || rwlock_is_contended(&pool->migrate_lock)) {
+		    || pool_lock_is_contended(pool)) {
 			putback_zspage(class, dst_zspage);
 			dst_zspage = NULL;
 
 			spin_unlock(&class->lock);
-			write_unlock(&pool->migrate_lock);
+			pool_write_unlock(pool);
 			cond_resched();
-			write_lock(&pool->migrate_lock);
+			pool_write_lock(pool);
 			spin_lock(&class->lock);
 		}
 	}
@@ -2002,7 +2027,7 @@ static unsigned long __zs_compact(struct zs_pool *pool,
 		putback_zspage(class, dst_zspage);
 
 	spin_unlock(&class->lock);
-	write_unlock(&pool->migrate_lock);
+	pool_write_unlock(pool);
 
 	return pages_freed;
 }
-- 
2.48.1.262.g85cc9f2d1e-goog