Slab allocators: consistent ZERO_SIZE_PTR support and NULL result semantics
Define ZERO_OR_NULL_PTR macro to be able to remove the checks from the
allocators. Move ZERO_SIZE_PTR related stuff into slab.h.
Make ZERO_SIZE_PTR work for all slab allocators and get rid of the
WARN_ON_ONCE(size == 0) that is still remaining in SLAB.
Make slub return NULL like the other allocators if a too large memory segment
is requested via __kmalloc.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slub.c b/mm/slub.c
index 1b0a95d..548d78d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2270,10 +2270,11 @@
int index = kmalloc_index(size);
if (!index)
- return NULL;
+ return ZERO_SIZE_PTR;
/* Allocation too large? */
- BUG_ON(index < 0);
+ if (index < 0)
+ return NULL;
#ifdef CONFIG_ZONE_DMA
if ((flags & SLUB_DMA)) {
@@ -2314,9 +2315,10 @@
{
struct kmem_cache *s = get_slab(size, flags);
- if (s)
- return slab_alloc(s, flags, -1, __builtin_return_address(0));
- return ZERO_SIZE_PTR;
+ if (ZERO_OR_NULL_PTR(s))
+ return s;
+
+ return slab_alloc(s, flags, -1, __builtin_return_address(0));
}
EXPORT_SYMBOL(__kmalloc);
@@ -2325,9 +2327,10 @@
{
struct kmem_cache *s = get_slab(size, flags);
- if (s)
- return slab_alloc(s, flags, node, __builtin_return_address(0));
- return ZERO_SIZE_PTR;
+ if (ZERO_OR_NULL_PTR(s))
+ return s;
+
+ return slab_alloc(s, flags, node, __builtin_return_address(0));
}
EXPORT_SYMBOL(__kmalloc_node);
#endif
@@ -2378,7 +2381,7 @@
* this comparison would be true for all "negative" pointers
* (which would cover the whole upper half of the address space).
*/
- if ((unsigned long)x <= (unsigned long)ZERO_SIZE_PTR)
+ if (ZERO_OR_NULL_PTR(x))
return;
page = virt_to_head_page(x);
@@ -2687,8 +2690,8 @@
{
struct kmem_cache *s = get_slab(size, gfpflags);
- if (!s)
- return ZERO_SIZE_PTR;
+ if (ZERO_OR_NULL_PTR(s))
+ return s;
return slab_alloc(s, gfpflags, -1, caller);
}
@@ -2698,8 +2701,8 @@
{
struct kmem_cache *s = get_slab(size, gfpflags);
- if (!s)
- return ZERO_SIZE_PTR;
+ if (ZERO_OR_NULL_PTR(s))
+ return s;
return slab_alloc(s, gfpflags, node, caller);
}