Commit 40f9fb8c authored by Mahendran Ganesh's avatar Mahendran Ganesh Committed by Linus Torvalds
Browse files

mm/zsmalloc: support allocating obj with size of ZS_MAX_ALLOC_SIZE 

I sent a patch [1] for unnecessary check in zsmalloc.  And Minchan Kim
found zsmalloc even does not support allocating an obj with the size of
ZS_MAX_ALLOC_SIZE in some situations.

For example:
   In system with 64KB PAGE_SIZE and 32 bit of physical addr. Then:
   ZS_MIN_ALLOC_SIZE is 32 bytes which is calculated by:
      MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
   ZS_MAX_ALLOC_SIZE is 64KB(in current code, is PAGE_SIZE)
   ZS_SIZE_CLASS_DELTA is 256 bytes
   So, ZS_SIZE_CLASSES = (ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) /
                          ZS_SIZE_CLASS_DELTA + 1
                       = 256

   In zs_create_pool(), the max size obj which can be allocated will be:
      ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA = 32 + 255*256 = 65312

   We can see that 65312 < 65536 (ZS_MAX_ALLOC_SIZE). So we can NOT
   allocate objs with size ZS_MAX_ALLOC_SIZE(65536) which we promise upper
   users we can do.

 [1]  http://lkml.iu.edu/hypermail/linux/kernel/1411.2/03835.html
 [2]  http://lkml.iu.edu/hypermail/linux/kernel/1411.2/04534.html



This patch fixes this issue by dynamiclly calculating zs_size_classes when
module is loaded, allocates buffer with size ZS_MAX_ALLOC_SIZE.  Then the
max obj(size is ZS_MAX_ALLOC_SIZE) can be stored in it.

[akpm@linux-foundation.org: restore ZS_SIZE_CLASSES to fix bisectability]
Signed-off-by: default avatarMahendran Ganesh <opensource.ganesh@gmail.com>
Suggested-by: default avatarMinchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent af4ee5e9

mm/zsmalloc.c

+32 −6
Original line number Diff line number Diff line
@@ -170,6 +170,11 @@ enum fullness_group { 
	ZS_FULL

};



/*

 * number of size_classes

 */

static int zs_size_classes;



/*

 * We assign a page to ZS_ALMOST_EMPTY fullness group when:

 *	n <= N / f, where
@@ -214,7 +219,7 @@ struct link_free { 
};



struct zs_pool {

	struct size_class *size_class[ZS_SIZE_CLASSES];

	struct size_class **size_class;



	gfp_t flags;	/* allocation flags used when growing pool */

	atomic_long_t pages_allocated;
@@ -785,7 +790,7 @@ static inline int __zs_cpu_up(struct mapping_area *area) 
	 */

	if (area->vm_buf)

		return 0;

	area->vm_buf = (char *)__get_free_page(GFP_KERNEL);

	area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL);

	if (!area->vm_buf)

		return -ENOMEM;

	return 0;
@@ -793,8 +798,7 @@ static inline int __zs_cpu_up(struct mapping_area *area) 


static inline void __zs_cpu_down(struct mapping_area *area)

{

	if (area->vm_buf)

		free_page((unsigned long)area->vm_buf);

	kfree(area->vm_buf);

	area->vm_buf = NULL;

}
@@ -912,6 +916,17 @@ static int zs_register_cpu_notifier(void) 
	return notifier_to_errno(ret);

}



static void init_zs_size_classes(void)

{

	int nr;



	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;



	zs_size_classes = nr;

}



static void __exit zs_exit(void)

{

#ifdef CONFIG_ZPOOL
@@ -929,6 +944,8 @@ static int __init zs_init(void) 
		return ret;

	}



	init_zs_size_classes();



#ifdef CONFIG_ZPOOL

	zpool_register_driver(&zs_zpool_driver);

#endif
@@ -972,11 +989,18 @@ struct zs_pool *zs_create_pool(gfp_t flags) 
	if (!pool)

		return NULL;



	pool->size_class = kcalloc(zs_size_classes, sizeof(struct size_class *),

			GFP_KERNEL);

	if (!pool->size_class) {

		kfree(pool);

		return NULL;

	}



	/*

	 * Iterate reversly, because, size of size_class that we want to use

	 * for merging should be larger or equal to current size.

	 */

	for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {

	for (i = zs_size_classes - 1; i >= 0; i--) {

		int size;

		int pages_per_zspage;

		struct size_class *class;
@@ -1029,7 +1053,7 @@ void zs_destroy_pool(struct zs_pool *pool) 
{

	int i;



	for (i = 0; i < ZS_SIZE_CLASSES; i++) {

	for (i = 0; i < zs_size_classes; i++) {

		int fg;

		struct size_class *class = pool->size_class[i];
@@ -1047,6 +1071,8 @@ void zs_destroy_pool(struct zs_pool *pool) 
		}

		kfree(class);

	}



	kfree(pool->size_class);

	kfree(pool);

}

EXPORT_SYMBOL_GPL(zs_destroy_pool);

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