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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: Mahendran Ganesh <opensource.ganesh@gmail.com>
Suggested-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mahendran Ganesh 2014-12-12 16:57:01 -08:00 committed by Linus Torvalds
parent af4ee5e977
commit 40f9fb8cff
1 changed files with 32 additions and 6 deletions
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38
mm/zsmalloc.c
View File

@ -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);