[PATCH] mm: remove broken 'kzalloc' mempool

[PATCH] mm: remove broken 'kzalloc' mempool

[Sage Weil]

The kzalloc mempool zeros items when they are initially allocated, but
does not rezero used items that are returned to the pool.  Consequently
mempool_alloc()s may return non-zeroed memory.

Since there are/were only two in-tree users for mempool_create_kzalloc_pool(),
and 'fixing' this in a way that will re-zero used (but not new) items
before first use is non-trivial, just remove it.

CC: <linux-mm@kvack.org>
Signed-off-by: Sage Weil <sage@newdream.net>
---
 include/linux/mempool.h |   10 ++--------
 mm/mempool.c            |    7 -------
 2 files changed, 2 insertions(+), 15 deletions(-)

diff --git a/include/linux/mempool.h b/include/linux/mempool.h
index 9be484d..7c08052 100644
--- a/include/linux/mempool.h
+++ b/include/linux/mempool.h
@@ -47,22 +47,16 @@ mempool_create_slab_pool(int min_nr, struct kmem_cache *kc)
 }
 
 /*
- * 2 mempool_alloc_t's and a mempool_free_t to kmalloc/kzalloc and kfree
- * the amount of memory specified by pool_data
+ * a mempool_alloc_t and a mempool_free_t to kmalloc and kfree the
+ * amount of memory specified by pool_data
  */
 void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data);
-void *mempool_kzalloc(gfp_t gfp_mask, void *pool_data);
 void mempool_kfree(void *element, void *pool_data);
 static inline mempool_t *mempool_create_kmalloc_pool(int min_nr, size_t size)
 {
 	return mempool_create(min_nr, mempool_kmalloc, mempool_kfree,
 			      (void *) size);
 }
-static inline mempool_t *mempool_create_kzalloc_pool(int min_nr, size_t size)
-{
-	return mempool_create(min_nr, mempool_kzalloc, mempool_kfree,
-			      (void *) size);
-}
 
 /*
  * A mempool_alloc_t and mempool_free_t for a simple page allocator that
diff --git a/mm/mempool.c b/mm/mempool.c
index a46eb1b..eea4f7d 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -308,13 +308,6 @@ void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
 }
 EXPORT_SYMBOL(mempool_kmalloc);
 
-void *mempool_kzalloc(gfp_t gfp_mask, void *pool_data)
-{
-	size_t size = (size_t) pool_data;
-	return kzalloc(size, gfp_mask);
-}
-EXPORT_SYMBOL(mempool_kzalloc);
-
 void mempool_kfree(void *element, void *pool_data)
 {
 	kfree(element);
-- 
1.5.6.5

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Re: [PATCH] mm: remove broken 'kzalloc' mempool

[Sage Weil]

On Mon, 3 Aug 2009, Sage Weil wrote:
> The kzalloc mempool zeros items when they are initially allocated, but
> does not rezero used items that are returned to the pool.  Consequently
> mempool_alloc()s may return non-zeroed memory.
> 
> Since there are/were only two in-tree users for mempool_create_kzalloc_pool(),
> and 'fixing' this in a way that will re-zero used (but not new) items
> before first use is non-trivial, just remove it.

This should of course only be applied after the fixes for the two callers 
(dm multipath and ibmvscsi), whatever the protocol for order that may 
be...

sage


> 
> CC: <linux-mm@kvack.org>
> Signed-off-by: Sage Weil <sage@newdream.net>
> ---
>  include/linux/mempool.h |   10 ++--------
>  mm/mempool.c            |    7 -------
>  2 files changed, 2 insertions(+), 15 deletions(-)
> 
> diff --git a/include/linux/mempool.h b/include/linux/mempool.h
> index 9be484d..7c08052 100644
> --- a/include/linux/mempool.h
> +++ b/include/linux/mempool.h
> @@ -47,22 +47,16 @@ mempool_create_slab_pool(int min_nr, struct kmem_cache *kc)
>  }
>  
>  /*
> - * 2 mempool_alloc_t's and a mempool_free_t to kmalloc/kzalloc and kfree
> - * the amount of memory specified by pool_data
> + * a mempool_alloc_t and a mempool_free_t to kmalloc and kfree the
> + * amount of memory specified by pool_data
>   */
>  void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data);
> -void *mempool_kzalloc(gfp_t gfp_mask, void *pool_data);
>  void mempool_kfree(void *element, void *pool_data);
>  static inline mempool_t *mempool_create_kmalloc_pool(int min_nr, size_t size)
>  {
>  	return mempool_create(min_nr, mempool_kmalloc, mempool_kfree,
>  			      (void *) size);
>  }
> -static inline mempool_t *mempool_create_kzalloc_pool(int min_nr, size_t size)
> -{
> -	return mempool_create(min_nr, mempool_kzalloc, mempool_kfree,
> -			      (void *) size);
> -}
>  
>  /*
>   * A mempool_alloc_t and mempool_free_t for a simple page allocator that
> diff --git a/mm/mempool.c b/mm/mempool.c
> index a46eb1b..eea4f7d 100644
> --- a/mm/mempool.c
> +++ b/mm/mempool.c
> @@ -308,13 +308,6 @@ void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
>  }
>  EXPORT_SYMBOL(mempool_kmalloc);
>  
> -void *mempool_kzalloc(gfp_t gfp_mask, void *pool_data)
> -{
> -	size_t size = (size_t) pool_data;
> -	return kzalloc(size, gfp_mask);
> -}
> -EXPORT_SYMBOL(mempool_kzalloc);
> -
>  void mempool_kfree(void *element, void *pool_data)
>  {
>  	kfree(element);
> -- 
> 1.5.6.5
> 
> 

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