All occurrences of mempools based on slab caches with object constructors
have been removed from the tree, so disallow creating them.
We can only dereference mem->ctor in mm/mempool.c without including
mm/slab.h in include/linux/mempool.h. So simply note the restriction,
just like the comment restrictig usage of __GFP_ZERO, and warn on
kernels with CONFIG_DEBUG_VM() if such a mempool is allocated from.
We don't want to incur this check on every element allocation, so use
VM_BUG_ON().
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
include/linux/mempool.h | 3 ++-
mm/mempool.c | 2 ++
2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/include/linux/mempool.h b/include/linux/mempool.h
--- a/include/linux/mempool.h
+++ b/include/linux/mempool.h
@@ -36,7 +36,8 @@ extern void mempool_free(void *element, mempool_t *pool);
/*
* A mempool_alloc_t and mempool_free_t that get the memory from
- * a slab that is passed in through pool_data.
+ * a slab cache that is passed in through pool_data.
+ * Note: the slab cache may not have a ctor function.
*/
void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data);
void mempool_free_slab(void *element, void *pool_data);
diff --git a/mm/mempool.c b/mm/mempool.c
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -15,6 +15,7 @@
#include <linux/mempool.h>
#include <linux/blkdev.h>
#include <linux/writeback.h>
+#include "slab.h"
static void add_element(mempool_t *pool, void *element)
{
@@ -332,6 +333,7 @@ EXPORT_SYMBOL(mempool_free);
void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
{
struct kmem_cache *mem = pool_data;
+ VM_BUG_ON(mem->ctor);
return kmem_cache_alloc(mem, gfp_mask);
}
EXPORT_SYMBOL(mempool_alloc_slab);
--
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