From e244c9e66f6197f55f6fbb2d5e70714e262cc595 Mon Sep 17 00:00:00 2001
From: David Rientjes <rientjes@google.com>
Date: Wed, 15 Apr 2015 16:14:14 -0700
Subject: [PATCH] mm, mempool: disallow mempools based on slab caches with
constructors
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 restricting 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@google.com>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sebastian Ott <sebott@linux.vnet.ibm.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
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
index b19b3023c8803..69b6951e8fd23 100644
--- 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
index 949970db28741..b60fb85526ed6 100644
--- 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)
{
@@ -334,6 +335,7 @@ 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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