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slub: correct to calculate num of acquired objects in get_partial_node()

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There is a subtle bug when calculating a number of acquired objects.

Currently, we calculate "available = page->objects - page->inuse",
after acquire_slab() is called in get_partial_node().

In acquire_slab() with mode = 1, we always set new.inuse = page->objects.
So,

	acquire_slab(s, n, page, object == NULL);

	if (!object) {
		c->page = page;
		stat(s, ALLOC_FROM_PARTIAL);
		object = t;
		available = page->objects - page->inuse;

		!!! availabe is always 0 !!!
	...

Therfore, "available > s->cpu_partial / 2" is always false and
we always go to second iteration.
This patch correct this problem.

After that, we don't need return value of put_cpu_partial().
So remove it.

Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
This commit is contained in:
Joonsoo Kim 2013-01-21 17:01:25 +09:00 committed by Pekka Enberg
parent 7d557b3cb6
commit 633b076464
1 changed files with 9 additions and 8 deletions
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17
mm/slub.c
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@ -1493,7 +1493,7 @@ static inline void remove_partial(struct kmem_cache_node *n,
*/
static inline void *acquire_slab(struct kmem_cache *s,
struct kmem_cache_node *n, struct page *page,
int mode)
int mode, int *objects)
{
void *freelist;
unsigned long counters;
@ -1507,6 +1507,7 @@ static inline void *acquire_slab(struct kmem_cache *s,
freelist = page->freelist;
counters = page->counters;
new.counters = counters;
*objects = new.objects - new.inuse;
if (mode) {
new.inuse = page->objects;
new.freelist = NULL;
@ -1528,7 +1529,7 @@ static inline void *acquire_slab(struct kmem_cache *s,
return freelist;
}
static int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain);
static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain);
static inline bool pfmemalloc_match(struct page *page, gfp_t gfpflags);
/*
@ -1539,6 +1540,8 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
{
struct page *page, *page2;
void *object = NULL;
int available = 0;
int objects;
/*
* Racy check. If we mistakenly see no partial slabs then we
@ -1552,22 +1555,21 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
spin_lock(&n->list_lock);
list_for_each_entry_safe(page, page2, &n->partial, lru) {
void *t;
int available;
if (!pfmemalloc_match(page, flags))
continue;
t = acquire_slab(s, n, page, object == NULL);
t = acquire_slab(s, n, page, object == NULL, &objects);
if (!t)
break;
available += objects;
if (!object) {
c->page = page;
stat(s, ALLOC_FROM_PARTIAL);
object = t;
available = page->objects - page->inuse;
} else {
available = put_cpu_partial(s, page, 0);
put_cpu_partial(s, page, 0);
stat(s, CPU_PARTIAL_NODE);
}
if (kmem_cache_debug(s) || available > s->cpu_partial / 2)
@ -1946,7 +1948,7 @@ static void unfreeze_partials(struct kmem_cache *s,
* If we did not find a slot then simply move all the partials to the
* per node partial list.
*/
static int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
{
struct page *oldpage;
int pages;
@ -1984,7 +1986,6 @@ static int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
page->next = oldpage;
} while (this_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) != oldpage);
return pobjects;
}
static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)