mm/zsmalloc: adjust order of functions

Currently functions in zsmalloc.c does not arranged in a readable and
reasonable sequence.  With the more and more functions added, we may
meet below inconvenience.  For example:

Current functions:

    void zs_init()
    {
    }

    static void get_maxobj_per_zspage()
    {
    }

Then I want to add a func_1() which is called from zs_init(), and this
new added function func_1() will used get_maxobj_per_zspage() which is
defined below zs_init().

    void func_1()
    {
        get_maxobj_per_zspage()
    }

    void zs_init()
    {
        func_1()
    }

    static void get_maxobj_per_zspage()
    {
    }

This will cause compiling issue. So we must add a declaration:

    static void get_maxobj_per_zspage();

before func_1() if we do not put get_maxobj_per_zspage() before
func_1().

In addition, puting module_[init|exit] functions at the bottom of the
file conforms to our habit.

So, this patch ajusts function sequence as:

    /* helper functions */
    ...
    obj_location_to_handle()
    ...

    /* Some exported functions */
    ...

    zs_map_object()
    zs_unmap_object()

    zs_malloc()
    zs_free()

    zs_init()
    zs_exit()

Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/zsmalloc.c

@@ -884,19 +884,6 @@ static struct notifier_block zs_cpu_nb = {
 	.notifier_call = zs_cpu_notifier
 };
 
-static void zs_unregister_cpu_notifier(void)
-{
-	int cpu;
-
-	cpu_notifier_register_begin();
-
-	for_each_online_cpu(cpu)
-		zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu);
-	__unregister_cpu_notifier(&zs_cpu_nb);
-
-	cpu_notifier_register_done();
-}
-
 static int zs_register_cpu_notifier(void)
 {
 	int cpu, uninitialized_var(ret);
@@ -914,40 +901,28 @@ static int zs_register_cpu_notifier(void)
 	return notifier_to_errno(ret);
 }
 
-static void init_zs_size_classes(void)
+static void zs_unregister_cpu_notifier(void)
 {
-	int nr;
+	int cpu;
 
-	nr = (ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1;
-	if ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) % ZS_SIZE_CLASS_DELTA)
-		nr += 1;
+	cpu_notifier_register_begin();
 
-	zs_size_classes = nr;
-}
+	for_each_online_cpu(cpu)
+		zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu);
+	__unregister_cpu_notifier(&zs_cpu_nb);
 
-static void __exit zs_exit(void)
-{
-#ifdef CONFIG_ZPOOL
-	zpool_unregister_driver(&zs_zpool_driver);
-#endif
-	zs_unregister_cpu_notifier();
+	cpu_notifier_register_done();
 }
 
-static int __init zs_init(void)
+static void init_zs_size_classes(void)
 {
-	int ret = zs_register_cpu_notifier();
-
-	if (ret) {
-		zs_unregister_cpu_notifier();
-		return ret;
-	}
+	int nr;
 
-	init_zs_size_classes();
+	nr = (ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1;
+	if ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) % ZS_SIZE_CLASS_DELTA)
+		nr += 1;
 
-#ifdef CONFIG_ZPOOL
-	zpool_register_driver(&zs_zpool_driver);
-#endif
-	return 0;
+	zs_size_classes = nr;
 }
 
 static unsigned int get_maxobj_per_zspage(int size, int pages_per_zspage)
@@ -967,113 +942,101 @@ static bool can_merge(struct size_class *prev, int size, int pages_per_zspage)
 	return true;
 }
 
+unsigned long zs_get_total_pages(struct zs_pool *pool)
+{
+	return atomic_long_read(&pool->pages_allocated);
+}
+EXPORT_SYMBOL_GPL(zs_get_total_pages);
+
 /**
- * zs_create_pool - Creates an allocation pool to work from.
- * @flags: allocation flags used to allocate pool metadata
+ * zs_map_object - get address of allocated object from handle.
+ * @pool: pool from which the object was allocated
+ * @handle: handle returned from zs_malloc
  *
- * This function must be called before anything when using
- * the zsmalloc allocator.
+ * Before using an object allocated from zs_malloc, it must be mapped using
+ * this function. When done with the object, it must be unmapped using
+ * zs_unmap_object.
  *
- * On success, a pointer to the newly created pool is returned,
- * otherwise NULL.
+ * Only one object can be mapped per cpu at a time. There is no protection
+ * against nested mappings.
+ *
+ * This function returns with preemption and page faults disabled.
  */
-struct zs_pool *zs_create_pool(gfp_t flags)
+void *zs_map_object(struct zs_pool *pool, unsigned long handle,
+			enum zs_mapmode mm)
 {
-	int i;
-	struct zs_pool *pool;
-	struct size_class *prev_class = NULL;
+	struct page *page;
+	unsigned long obj_idx, off;
 
-	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
-	if (!pool)
-		return NULL;
+	unsigned int class_idx;
+	enum fullness_group fg;
+	struct size_class *class;
+	struct mapping_area *area;
+	struct page *pages[2];
 
-	pool->size_class = kcalloc(zs_size_classes, sizeof(struct size_class *),
-			GFP_KERNEL);
-	if (!pool->size_class) {
-		kfree(pool);
-		return NULL;
-	}
+	BUG_ON(!handle);
 
 	/*
-	 * Iterate reversly, because, size of size_class that we want to use
-	 * for merging should be larger or equal to current size.
+	 * Because we use per-cpu mapping areas shared among the
+	 * pools/users, we can't allow mapping in interrupt context
+	 * because it can corrupt another users mappings.
 	 */
-	for (i = zs_size_classes - 1; i >= 0; i--) {
-		int size;
-		int pages_per_zspage;
-		struct size_class *class;
-
-		size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
-		if (size > ZS_MAX_ALLOC_SIZE)
-			size = ZS_MAX_ALLOC_SIZE;
-		pages_per_zspage = get_pages_per_zspage(size);
-
-		/*
-		 * size_class is used for normal zsmalloc operation such
-		 * as alloc/free for that size. Although it is natural that we
-		 * have one size_class for each size, there is a chance that we
-		 * can get more memory utilization if we use one size_class for
-		 * many different sizes whose size_class have same
-		 * characteristics. So, we makes size_class point to
-		 * previous size_class if possible.
-		 */
-		if (prev_class) {
-			if (can_merge(prev_class, size, pages_per_zspage)) {
-				pool->size_class[i] = prev_class;
-				continue;
-			}
-		}
-
-		class = kzalloc(sizeof(struct size_class), GFP_KERNEL);
-		if (!class)
-			goto err;
+	BUG_ON(in_interrupt());
 
-		class->size = size;
-		class->index = i;
-		class->pages_per_zspage = pages_per_zspage;
-		spin_lock_init(&class->lock);
-		pool->size_class[i] = class;
+	obj_handle_to_location(handle, &page, &obj_idx);
+	get_zspage_mapping(get_first_page(page), &class_idx, &fg);
+	class = pool->size_class[class_idx];
+	off = obj_idx_to_offset(page, obj_idx, class->size);
 
-		prev_class = class;
+	area = &get_cpu_var(zs_map_area);
+	area->vm_mm = mm;
+	if (off + class->size <= PAGE_SIZE) {
+		/* this object is contained entirely within a page */
+		area->vm_addr = kmap_atomic(page);
+		return area->vm_addr + off;
 	}
 
-	pool->flags = flags;
-
-	return pool;
+	/* this object spans two pages */
+	pages[0] = page;
+	pages[1] = get_next_page(page);
+	BUG_ON(!pages[1]);
 
-err:
-	zs_destroy_pool(pool);
-	return NULL;
+	return __zs_map_object(area, pages, off, class->size);
 }
-EXPORT_SYMBOL_GPL(zs_create_pool);
+EXPORT_SYMBOL_GPL(zs_map_object);
 
-void zs_destroy_pool(struct zs_pool *pool)
+void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
 {
-	int i;
+	struct page *page;
+	unsigned long obj_idx, off;
 
-	for (i = 0; i < zs_size_classes; i++) {
-		int fg;
-		struct size_class *class = pool->size_class[i];
+	unsigned int class_idx;
+	enum fullness_group fg;
+	struct size_class *class;
+	struct mapping_area *area;
 
-		if (!class)
-			continue;
+	BUG_ON(!handle);
 
-		if (class->index != i)
-			continue;
+	obj_handle_to_location(handle, &page, &obj_idx);
+	get_zspage_mapping(get_first_page(page), &class_idx, &fg);
+	class = pool->size_class[class_idx];
+	off = obj_idx_to_offset(page, obj_idx, class->size);
 
-		for (fg = 0; fg < _ZS_NR_FULLNESS_GROUPS; fg++) {
-			if (class->fullness_list[fg]) {
-				pr_info("Freeing non-empty class with size %db, fullness group %d\n",
-					class->size, fg);
-			}
-		}
-		kfree(class);
-	}
+	area = this_cpu_ptr(&zs_map_area);
+	if (off + class->size <= PAGE_SIZE)
+		kunmap_atomic(area->vm_addr);
+	else {
+		struct page *pages[2];
 
-	kfree(pool->size_class);
-	kfree(pool);
+		pages[0] = page;
+		pages[1] = get_next_page(page);
+		BUG_ON(!pages[1]);
+
+		__zs_unmap_object(area, pages, off, class->size);
+	}
+	put_cpu_var(zs_map_area);
 }
-EXPORT_SYMBOL_GPL(zs_destroy_pool);
+EXPORT_SYMBOL_GPL(zs_unmap_object);
 
 /**
  * zs_malloc - Allocate block of given size from pool.
@@ -1176,100 +1139,137 @@ void zs_free(struct zs_pool *pool, unsigned long obj)
 EXPORT_SYMBOL_GPL(zs_free);
 
 /**
- * zs_map_object - get address of allocated object from handle.
- * @pool: pool from which the object was allocated
- * @handle: handle returned from zs_malloc
- *
- * Before using an object allocated from zs_malloc, it must be mapped using
- * this function. When done with the object, it must be unmapped using
- * zs_unmap_object.
+ * zs_create_pool - Creates an allocation pool to work from.
+ * @flags: allocation flags used to allocate pool metadata
  *
- * Only one object can be mapped per cpu at a time. There is no protection
- * against nested mappings.
+ * This function must be called before anything when using
+ * the zsmalloc allocator.
  *
- * This function returns with preemption and page faults disabled.
+ * On success, a pointer to the newly created pool is returned,
+ * otherwise NULL.
  */
-void *zs_map_object(struct zs_pool *pool, unsigned long handle,
-			enum zs_mapmode mm)
+struct zs_pool *zs_create_pool(gfp_t flags)
 {
-	struct page *page;
-	unsigned long obj_idx, off;
+	int i;
+	struct zs_pool *pool;
+	struct size_class *prev_class = NULL;
 
-	unsigned int class_idx;
-	enum fullness_group fg;
-	struct size_class *class;
-	struct mapping_area *area;
-	struct page *pages[2];
+	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
+	if (!pool)
+		return NULL;
 
-	BUG_ON(!handle);
+	pool->size_class = kcalloc(zs_size_classes, sizeof(struct size_class *),
+			GFP_KERNEL);
+	if (!pool->size_class) {
+		kfree(pool);
+		return NULL;
+	}
 
 	/*
-	 * Because we use per-cpu mapping areas shared among the
-	 * pools/users, we can't allow mapping in interrupt context
-	 * because it can corrupt another users mappings.
+	 * Iterate reversly, because, size of size_class that we want to use
+	 * for merging should be larger or equal to current size.
 	 */
-	BUG_ON(in_interrupt());
+	for (i = zs_size_classes - 1; i >= 0; i--) {
+		int size;
+		int pages_per_zspage;
+		struct size_class *class;
 
-	obj_handle_to_location(handle, &page, &obj_idx);
-	get_zspage_mapping(get_first_page(page), &class_idx, &fg);
-	class = pool->size_class[class_idx];
-	off = obj_idx_to_offset(page, obj_idx, class->size);
+		size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
+		if (size > ZS_MAX_ALLOC_SIZE)
+			size = ZS_MAX_ALLOC_SIZE;
+		pages_per_zspage = get_pages_per_zspage(size);
 
-	area = &get_cpu_var(zs_map_area);
-	area->vm_mm = mm;
-	if (off + class->size <= PAGE_SIZE) {
-		/* this object is contained entirely within a page */
-		area->vm_addr = kmap_atomic(page);
-		return area->vm_addr + off;
+		/*
+		 * size_class is used for normal zsmalloc operation such
+		 * as alloc/free for that size. Although it is natural that we
+		 * have one size_class for each size, there is a chance that we
+		 * can get more memory utilization if we use one size_class for
+		 * many different sizes whose size_class have same
+		 * characteristics. So, we makes size_class point to
+		 * previous size_class if possible.
+		 */
+		if (prev_class) {
+			if (can_merge(prev_class, size, pages_per_zspage)) {
+				pool->size_class[i] = prev_class;
+				continue;
+			}
+		}
+
+		class = kzalloc(sizeof(struct size_class), GFP_KERNEL);
+		if (!class)
+			goto err;
+
+		class->size = size;
+		class->index = i;
+		class->pages_per_zspage = pages_per_zspage;
+		spin_lock_init(&class->lock);
+		pool->size_class[i] = class;
+
+		prev_class = class;
 	}
 
-	/* this object spans two pages */
-	pages[0] = page;
-	pages[1] = get_next_page(page);
-	BUG_ON(!pages[1]);
+	pool->flags = flags;
 
-	return __zs_map_object(area, pages, off, class->size);
+	return pool;
+
+err:
+	zs_destroy_pool(pool);
+	return NULL;
 }
-EXPORT_SYMBOL_GPL(zs_map_object);
+EXPORT_SYMBOL_GPL(zs_create_pool);
 
-void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
+void zs_destroy_pool(struct zs_pool *pool)
 {
-	struct page *page;
-	unsigned long obj_idx, off;
+	int i;
 
-	unsigned int class_idx;
-	enum fullness_group fg;
-	struct size_class *class;
-	struct mapping_area *area;
+	for (i = 0; i < zs_size_classes; i++) {
+		int fg;
+		struct size_class *class = pool->size_class[i];
 
-	BUG_ON(!handle);
+		if (!class)
+			continue;
 
-	obj_handle_to_location(handle, &page, &obj_idx);
-	get_zspage_mapping(get_first_page(page), &class_idx, &fg);
-	class = pool->size_class[class_idx];
-	off = obj_idx_to_offset(page, obj_idx, class->size);
+		if (class->index != i)
+			continue;
 
-	area = this_cpu_ptr(&zs_map_area);
-	if (off + class->size <= PAGE_SIZE)
-		kunmap_atomic(area->vm_addr);
-	else {
-		struct page *pages[2];
+		for (fg = 0; fg < _ZS_NR_FULLNESS_GROUPS; fg++) {
+			if (class->fullness_list[fg]) {
+				pr_info("Freeing non-empty class with size %db, fullness group %d\n",
+					class->size, fg);
+			}
+		}
+		kfree(class);
+	}
 
-		pages[0] = page;
-		pages[1] = get_next_page(page);
-		BUG_ON(!pages[1]);
+	kfree(pool->size_class);
+	kfree(pool);
+}
+EXPORT_SYMBOL_GPL(zs_destroy_pool);
 
-		__zs_unmap_object(area, pages, off, class->size);
+static int __init zs_init(void)
+{
+	int ret = zs_register_cpu_notifier();
+
+	if (ret) {
+		zs_unregister_cpu_notifier();
+		return ret;
 	}
-	put_cpu_var(zs_map_area);
+
+	init_zs_size_classes();
+
+#ifdef CONFIG_ZPOOL
+	zpool_register_driver(&zs_zpool_driver);
+#endif
+	return 0;
 }
-EXPORT_SYMBOL_GPL(zs_unmap_object);
 
-unsigned long zs_get_total_pages(struct zs_pool *pool)
+static void __exit zs_exit(void)
 {
-	return atomic_long_read(&pool->pages_allocated);
+#ifdef CONFIG_ZPOOL
+	zpool_unregister_driver(&zs_zpool_driver);
+#endif
+	zs_unregister_cpu_notifier();
 }
-EXPORT_SYMBOL_GPL(zs_get_total_pages);
 
 module_init(zs_init);
 module_exit(zs_exit);