linux-kernel - Re: Uninline kcalloc

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Date:	Tue, 14 Feb 2012 12:45:18 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Xi Wang <xi.wang@...il.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Jesper Juhl <jj@...osbits.net>, Jens Axboe <axboe@...nel.dk>,
	Pekka Enberg <penberg@...nel.org>,
	linux-kernel@...r.kernel.org, Matt Mackall <mpm@...enic.com>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: Uninline kcalloc

On Tue, 14 Feb 2012 13:33:40 -0600 (CST)
Christoph Lameter <cl@...ux.com> wrote:

> Subject: Uninline kcalloc
> 
> kcalloc is not used in performance critical ways. So it does not need to
> be inline. If we would add diagnostics to track the overflow occurrences
> then such code would be replicated at all call sites in the kernel.

Uninlining kcalloc() seems reasonable.  But if we're going to uninline
kcalloc() then we also should uninline kmalloc_array().

And yes, it's still called kmalloc_array() in my tree.  I've been
following this discussion for N days waiting for a reason for changing
the original patch and I ain't seen one yet.


From: Xi Wang <xi.wang@...il.com>
Subject: slab: introduce kmalloc_array()

Introduce a kmalloc_array() wrapper that performs integer overflow
checking without zeroing the memory.

Suggested-by: Andrew Morton <akpm@...ux-foundation.org>
Suggested-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Xi Wang <xi.wang@...il.com>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 include/linux/slab.h |   17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff -puN include/linux/slab.h~slab-introduce-kmalloc_array include/linux/slab.h
--- a/include/linux/slab.h~slab-introduce-kmalloc_array
+++ a/include/linux/slab.h
@@ -190,7 +190,7 @@ size_t ksize(const void *);
 #endif
 
 /**
- * kcalloc - allocate memory for an array. The memory is set to zero.
+ * kmalloc_array - allocate memory for an array.
  * @n: number of elements.
  * @size: element size.
  * @flags: the type of memory to allocate.
@@ -240,11 +240,22 @@ size_t ksize(const void *);
  * for general use, and so are not documented here. For a full list of
  * potential flags, always refer to linux/gfp.h.
  */
-static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
+static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
 {
 	if (size != 0 && n > ULONG_MAX / size)
 		return NULL;
-	return __kmalloc(n * size, flags | __GFP_ZERO);
+	return __kmalloc(n * size, flags);
+}
+
+/**
+ * kcalloc - allocate memory for an array. The memory is set to zero.
+ * @n: number of elements.
+ * @size: element size.
+ * @flags: the type of memory to allocate (see kmalloc).
+ */
+static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
+{
+	return kmalloc_array(n, size, flags | __GFP_ZERO);
 }
 
 #if !defined(CONFIG_NUMA) && !defined(CONFIG_SLOB)
_

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