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-rw-r--r--include/linux/mm_types.h5
-rw-r--r--mm/slub.c70
2 files changed, 51 insertions, 24 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 34023c6..bfee0bd 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -64,7 +64,10 @@ struct page {
#if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS
spinlock_t ptl;
#endif
- struct kmem_cache *slab; /* SLUB: Pointer to slab */
+ struct {
+ struct kmem_cache *slab; /* SLUB: Pointer to slab */
+ void *end; /* SLUB: end marker */
+ };
struct page *first_page; /* Compound tail pages */
};
union {
diff --git a/mm/slub.c b/mm/slub.c
index 2dacaf5..5995626 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -280,15 +280,32 @@ static inline struct kmem_cache_cpu *get_cpu_slab(struct kmem_cache *s, int cpu)
#endif
}
+/*
+ * The end pointer in a slab is special. It points to the first object in the
+ * slab but has bit 0 set to mark it.
+ *
+ * Note that SLUB relies on page_mapping returning NULL for pages with bit 0
+ * in the mapping set.
+ */
+static inline int is_end(void *addr)
+{
+ return (unsigned long)addr & PAGE_MAPPING_ANON;
+}
+
+void *slab_address(struct page *page)
+{
+ return page->end - PAGE_MAPPING_ANON;
+}
+
static inline int check_valid_pointer(struct kmem_cache *s,
struct page *page, const void *object)
{
void *base;
- if (!object)
+ if (object == page->end)
return 1;
- base = page_address(page);
+ base = slab_address(page);
if (object < base || object >= base + s->objects * s->size ||
(object - base) % s->size) {
return 0;
@@ -321,7 +338,8 @@ static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
/* Scan freelist */
#define for_each_free_object(__p, __s, __free) \
- for (__p = (__free); __p; __p = get_freepointer((__s), __p))
+ for (__p = (__free); (__p) != page->end; __p = get_freepointer((__s),\
+ __p))
/* Determine object index from a given position */
static inline int slab_index(void *p, struct kmem_cache *s, void *addr)
@@ -473,7 +491,7 @@ static void slab_fix(struct kmem_cache *s, char *fmt, ...)
static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
{
unsigned int off; /* Offset of last byte */
- u8 *addr = page_address(page);
+ u8 *addr = slab_address(page);
print_tracking(s, p);
@@ -651,7 +669,7 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page)
if (!(s->flags & SLAB_POISON))
return 1;
- start = page_address(page);
+ start = slab_address(page);
end = start + (PAGE_SIZE << s->order);
length = s->objects * s->size;
remainder = end - (start + length);
@@ -718,7 +736,7 @@ static int check_object(struct kmem_cache *s, struct page *page,
* of the free objects in this slab. May cause
* another error because the object count is now wrong.
*/
- set_freepointer(s, p, NULL);
+ set_freepointer(s, p, page->end);
return 0;
}
return 1;
@@ -752,18 +770,18 @@ static int on_freelist(struct kmem_cache *s, struct page *page, void *search)
void *fp = page->freelist;
void *object = NULL;
- while (fp && nr <= s->objects) {
+ while (fp != page->end && nr <= s->objects) {
if (fp == search)
return 1;
if (!check_valid_pointer(s, page, fp)) {
if (object) {
object_err(s, page, object,
"Freechain corrupt");
- set_freepointer(s, object, NULL);
+ set_freepointer(s, object, page->end);
break;
} else {
slab_err(s, page, "Freepointer corrupt");
- page->freelist = NULL;
+ page->freelist = page->end;
page->inuse = s->objects;
slab_fix(s, "Freelist cleared");
return 0;
@@ -869,7 +887,7 @@ bad:
*/
slab_fix(s, "Marking all objects used");
page->inuse = s->objects;
- page->freelist = NULL;
+ page->freelist = page->end;
}
return 0;
}
@@ -910,7 +928,7 @@ static int free_debug_processing(struct kmem_cache *s, struct page *page,
}
/* Special debug activities for freeing objects */
- if (!SlabFrozen(page) && !page->freelist)
+ if (!SlabFrozen(page) && page->freelist == page->end)
remove_full(s, page);
if (s->flags & SLAB_STORE_USER)
set_track(s, object, TRACK_FREE, addr);
@@ -1102,6 +1120,7 @@ static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
SetSlabDebug(page);
start = page_address(page);
+ page->end = start + 1;
if (unlikely(s->flags & SLAB_POISON))
memset(start, POISON_INUSE, PAGE_SIZE << s->order);
@@ -1113,7 +1132,7 @@ static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
last = p;
}
setup_object(s, page, last);
- set_freepointer(s, last, NULL);
+ set_freepointer(s, last, page->end);
page->freelist = start;
page->inuse = 0;
@@ -1129,7 +1148,7 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
void *p;
slab_pad_check(s, page);
- for_each_object(p, s, page_address(page))
+ for_each_object(p, s, slab_address(page))
check_object(s, page, p, 0);
ClearSlabDebug(page);
}
@@ -1139,6 +1158,7 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE,
-pages);
+ page->mapping = NULL;
__free_pages(page, s->order);
}
@@ -1341,7 +1361,7 @@ static void unfreeze_slab(struct kmem_cache *s, struct page *page, int tail)
ClearSlabFrozen(page);
if (page->inuse) {
- if (page->freelist)
+ if (page->freelist != page->end)
add_partial(n, page, tail);
else if (SlabDebug(page) && (s->flags & SLAB_STORE_USER))
add_full(n, page);
@@ -1377,8 +1397,12 @@ static void deactivate_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
* Merge cpu freelist into freelist. Typically we get here
* because both freelists are empty. So this is unlikely
* to occur.
+ *
+ * We need to use _is_end here because deactivate slab may
+ * be called for a debug slab. Then c->freelist may contain
+ * a dummy pointer.
*/
- while (unlikely(c->freelist)) {
+ while (unlikely(!is_end(c->freelist))) {
void **object;
tail = 0; /* Hot objects. Put the slab first */
@@ -1478,7 +1502,7 @@ static void *__slab_alloc(struct kmem_cache *s,
goto another_slab;
load_freelist:
object = c->page->freelist;
- if (unlikely(!object))
+ if (unlikely(object == c->page->end))
goto another_slab;
if (unlikely(SlabDebug(c->page)))
goto debug;
@@ -1486,7 +1510,7 @@ load_freelist:
object = c->page->freelist;
c->freelist = object[c->offset];
c->page->inuse = s->objects;
- c->page->freelist = NULL;
+ c->page->freelist = c->page->end;
c->node = page_to_nid(c->page);
slab_unlock(c->page);
return object;
@@ -1550,7 +1574,7 @@ static __always_inline void *slab_alloc(struct kmem_cache *s,
local_irq_save(flags);
c = get_cpu_slab(s, smp_processor_id());
- if (unlikely(!c->freelist || !node_match(c, node)))
+ if (unlikely(is_end(c->freelist) || !node_match(c, node)))
object = __slab_alloc(s, gfpflags, node, addr, c);
@@ -1614,7 +1638,7 @@ checks_ok:
* was not on the partial list before
* then add it.
*/
- if (unlikely(!prior))
+ if (unlikely(prior == page->end))
add_partial(get_node(s, page_to_nid(page)), page, 1);
out_unlock:
@@ -1622,7 +1646,7 @@ out_unlock:
return;
slab_empty:
- if (prior)
+ if (prior != page->end)
/*
* Slab still on the partial list.
*/
@@ -1842,7 +1866,7 @@ static void init_kmem_cache_cpu(struct kmem_cache *s,
struct kmem_cache_cpu *c)
{
c->page = NULL;
- c->freelist = NULL;
+ c->freelist = (void *)PAGE_MAPPING_ANON;
c->node = 0;
c->offset = s->offset / sizeof(void *);
c->objsize = s->objsize;
@@ -3105,7 +3129,7 @@ static int validate_slab(struct kmem_cache *s, struct page *page,
unsigned long *map)
{
void *p;
- void *addr = page_address(page);
+ void *addr = slab_address(page);
if (!check_slab(s, page) ||
!on_freelist(s, page, NULL))
@@ -3385,7 +3409,7 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
static void process_slab(struct loc_track *t, struct kmem_cache *s,
struct page *page, enum track_item alloc)
{
- void *addr = page_address(page);
+ void *addr = slab_address(page);
DECLARE_BITMAP(map, s->objects);
void *p;
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