[PATCHv4 6/9] zsmalloc: pass limit on pages per-zspage to zs_create_pool()

[Sergey Senozhatsky <senozhatsky@chromium.org>]

Allow zsmalloc pool owner to specify max number of pages
per-zspage (during pool creation), so that different pools
can have different characteristics.

By default we pass ZS_DEFAULT_PAGES_PER_ZSPAGE which is 4
(matches the current order 2 zspages limit).

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 drivers/block/zram/zram_drv.c |  3 ++-
 include/linux/zsmalloc.h      |  2 +-
 mm/zsmalloc.c                 | 11 +++++++----
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 90b0c66bbd5b..bec02f636bce 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1247,7 +1247,8 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
 	if (!zram->table)
 		return false;
 
-	zram->mem_pool = zs_create_pool(zram->disk->disk_name);
+	zram->mem_pool = zs_create_pool(zram->disk->disk_name,
+					ZS_DEFAULT_PAGES_PER_ZSPAGE);
 	if (!zram->mem_pool) {
 		vfree(zram->table);
 		return false;
diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h
index b6b8654a2d45..28f2b9cb1c47 100644
--- a/include/linux/zsmalloc.h
+++ b/include/linux/zsmalloc.h
@@ -50,7 +50,7 @@ struct zs_pool_stats {
 
 struct zs_pool;
 
-struct zs_pool *zs_create_pool(const char *name);
+struct zs_pool *zs_create_pool(const char *name, unsigned long num_pages);
 void zs_destroy_pool(struct zs_pool *pool);
 
 unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t flags);
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index d329bd673baa..42987a913f45 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -366,7 +366,7 @@ static void *zs_zpool_create(const char *name, gfp_t gfp,
 	 * different contexts and its caller must provide a valid
 	 * gfp mask.
 	 */
-	return zs_create_pool(name);
+	return zs_create_pool(name, ZS_DEFAULT_PAGES_PER_ZSPAGE);
 }
 
 static void zs_zpool_destroy(void *pool)
@@ -2195,6 +2195,7 @@ static int zs_register_shrinker(struct zs_pool *pool)
 /**
  * zs_create_pool - Creates an allocation pool to work from.
  * @name: pool name to be created
+ * @num_pages: maximum number of pages per-zspage
  *
  * This function must be called before anything when using
  * the zsmalloc allocator.
@@ -2202,18 +2203,20 @@ static int zs_register_shrinker(struct zs_pool *pool)
  * On success, a pointer to the newly created pool is returned,
  * otherwise NULL.
  */
-struct zs_pool *zs_create_pool(const char *name)
+struct zs_pool *zs_create_pool(const char *name, unsigned long num_pages)
 {
 	int i;
 	struct zs_pool *pool;
 	struct size_class *prev_class = NULL;
-	unsigned long num_pages;
+
+	if (WARN_ON(num_pages < ZS_MIN_PAGES_PER_ZSPAGE ||
+		    num_pages > ZS_MAX_PAGES_PER_ZSPAGE))
+		return NULL;
 
 	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
 	if (!pool)
 		return NULL;
 
-	num_pages = ZS_DEFAULT_PAGES_PER_ZSPAGE;
 	/* min_alloc_size must be multiple of ZS_ALIGN */
 	pool->min_alloc_size = num_pages << PAGE_SHIFT >> OBJ_INDEX_BITS;
 	pool->min_alloc_size = max(pool->min_alloc_size, ZS_MIN_ALLOC_SIZE);
-- 
2.38.1.273.g43a17bfeac-goog