[PATCH] 2.6.16-rc1-mm1 - produce useful info for kzalloc with DEBUG_SLAB

[PATCH] 2.6.16-rc1-mm1 - produce useful info for kzalloc with DEBUG_SLAB

[Valdis.Kletnieks]

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The following patch makes a few minor changes so the CONFIG_DEBUG_SLAB
statistics report the actual caller for kzalloc() - otherwise its call to
kmalloc() just points at kzalloc().  Basically, we force __always_inline on
several routines, so the __builtin_return_address calls point where we
want them to point, even if gcc wouldn't otherwise do it.

Signed-Off-By: Valdis Kletnieks <valdis.kletnieks@vt.edu>
---
 include/linux/slab.h |   10 ++++++++++
 mm/slab.c            |    4 ++--
 mm/util.c            |    2 ++
 3 files changed, 14 insertions(+), 2 deletions(-)

--- linux-2.6.16-rc1-mm1/include/linux/slab.h.slab	2006-01-18 16:12:08.000000000 -0500
+++ linux-2.6.16-rc1-mm1/include/linux/slab.h	2006-01-18 16:12:10.000000000 -0500
@@ -101,7 +101,17 @@ found:
 	return __kmalloc(size, flags);
 }
 
+#ifdef CONFIG_DEBUG_SLAB
+static __always_inline void  *kzalloc(size_t size, gfp_t flags)
+{
+	void *ret = __kmalloc(size, flags);
+	if (ret)
+		memset(ret, 0, size);
+	return ret;
+}
+#else
 extern void *kzalloc(size_t, gfp_t);
+#endif
 
 /**
  * kcalloc - allocate memory for an array. The memory is set to zero.
--- linux-2.6.16-rc1-mm1/mm/slab.c.slab	2006-01-18 16:12:08.000000000 -0500
+++ linux-2.6.16-rc1-mm1/mm/slab.c	2006-01-19 03:13:29.000000000 -0500
@@ -2407,7 +2407,7 @@ static void kfree_debugcheck(const void 
 	}
 }
 
-static void *cache_free_debugcheck(struct kmem_cache *cachep, void *objp,
+static __always_inline void *cache_free_debugcheck(struct kmem_cache *cachep, void *objp,
 				   void *caller)
 {
 	struct page *page;
@@ -2614,7 +2614,7 @@ cache_alloc_debugcheck_before(struct kme
 }
 
 #if DEBUG
-static void *cache_alloc_debugcheck_after(struct kmem_cache *cachep, gfp_t flags,
+static __always_inline void *cache_alloc_debugcheck_after(struct kmem_cache *cachep, gfp_t flags,
 					void *objp, void *caller)
 {
 	if (!objp)
--- linux-2.6.16-rc1-mm1/mm/util.c.slab	2006-01-18 16:11:46.000000000 -0500
+++ linux-2.6.16-rc1-mm1/mm/util.c	2006-01-18 16:12:10.000000000 -0500
@@ -2,6 +2,7 @@
 #include <linux/string.h>
 #include <linux/module.h>
 
+#ifndef CONFIG_DEBUG_SLAB
 /**
  * kzalloc - allocate memory. The memory is set to zero.
  * @size: how many bytes of memory are required.
@@ -15,6 +16,7 @@ void *kzalloc(size_t size, gfp_t flags)
 	return ret;
 }
 EXPORT_SYMBOL(kzalloc);
+#endif
 
 /*
  * kstrdup - allocate space for and copy an existing string



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Re: [PATCH] 2.6.16-rc1-mm1 - produce useful info for kzalloc with DEBUG_SLAB

[Pekka Enberg]

Hi Valdis,

On 1/19/06, Valdis.Kletnieks@vt.edu <Valdis.Kletnieks@vt.edu> wrote:
> The following patch makes a few minor changes so the CONFIG_DEBUG_SLAB
> statistics report the actual caller for kzalloc() - otherwise its call to
> kmalloc() just points at kzalloc().  Basically, we force __always_inline on
> several routines, so the __builtin_return_address calls point where we
> want them to point, even if gcc wouldn't otherwise do it.

Couldn't we use this [1] trick Steven came up with for this?

  1. http://article.gmane.org/gmane.linux.kernel/362494

                                    Pekka

Re: [PATCH] 2.6.16-rc1-mm1 - produce useful info for kzalloc with DEBUG_SLAB

[Valdis.Kletnieks]

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On Thu, 19 Jan 2006 10:58:13 +0200, Pekka Enberg said:
> On 1/19/06, Valdis.Kletnieks@vt.edu <Valdis.Kletnieks@vt.edu> wrote:
> > The following patch makes a few minor changes so the CONFIG_DEBUG_SLAB
> > statistics report the actual caller for kzalloc() - otherwise its call to
> > kmalloc() just points at kzalloc().  Basically, we force __always_inline on
> > several routines, so the __builtin_return_address calls point where we
> > want them to point, even if gcc wouldn't otherwise do it.
> 
> Couldn't we use this [1] trick Steven came up with for this?
> 
>   1. http://article.gmane.org/gmane.linux.kernel/362494

I posted the basic idea of this patch back on Dec 18, Steven came up with
his stuff about 2 weeks later, and it's a bit too creative with its use of
the preprocessor for my tastes,  so I didn't retrofit the idea.

On the other hand, I'm not *that* attached to my solution - if somebody wants
to code a patch Steven's way and toss it to Andrew, they're welcome to do so,
and we'll let Andrew decide. ;)

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Re: [PATCH] 2.6.16-rc1-mm1 - produce useful info for kzalloc with DEBUG_SLAB

[Pekka J Enberg]

On Thu, 19 Jan 2006 Valdis.Kletnieks@vt.edu wrote:
> I posted the basic idea of this patch back on Dec 18, Steven came up with
> his stuff about 2 weeks later, and it's a bit too creative with its use of
> the preprocessor for my tastes,  so I didn't retrofit the idea.
> 
> On the other hand, I'm not *that* attached to my solution - if somebody wants
> to code a patch Steven's way and toss it to Andrew, they're welcome to do so,
> and we'll let Andrew decide. ;)

Actually, no need to do preprocessor tricks. Valdis, can you confirm that 
this patch actually fixes your problem? It is against 2.6.16-rc1-mm1.

			Pekka

[PATCH] slab: fix kzalloc and kstrdup caller report for CONFIG_DEBUG_SLAB

From: Pekka Enberg <penberg@cs.helsinki.fi>

This patch fixes kzalloc() and kstrdup() caller report for CONFIG_DEBUG_SLAB.
We must pass the caller to __cache_alloc() instead of directly doing
__builtin_return_address(0) there; otherwise kzalloc() and kstrdup() are
reported as the allocation site instead of the real one.

Thanks to Valdis Kletnieks for reporting the problem and Steven Rostedt for
the original idea.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
---

 include/linux/slab.h |    7 +++++++
 mm/slab.c            |   28 +++++++++++++++++++++++-----
 2 files changed, 30 insertions(+), 5 deletions(-)

Index: 2.6-mm/include/linux/slab.h
===================================================================
--- 2.6-mm.orig/include/linux/slab.h
+++ 2.6-mm/include/linux/slab.h
@@ -76,7 +76,14 @@ struct cache_sizes {
 	kmem_cache_t	*cs_dmacachep;
 };
 extern struct cache_sizes malloc_sizes[];
+
+#ifndef CONFIG_DEBUG_SLAB
 extern void *__kmalloc(size_t, gfp_t);
+#else
+extern void *__kmalloc_track_caller(size_t, gfp_t, void*);
+#define __kmalloc(size, flags) \
+    __kmalloc_track_caller(size, flags, __builtin_return_address(0))
+#endif
 
 static inline void *kmalloc(size_t size, gfp_t flags)
 {
Index: 2.6-mm/mm/slab.c
===================================================================
--- 2.6-mm.orig/mm/slab.c
+++ 2.6-mm/mm/slab.c
@@ -2699,7 +2699,8 @@ static inline void *____cache_alloc(stru
 	return objp;
 }
 
-static inline void *__cache_alloc(struct kmem_cache *cachep, gfp_t flags)
+static __always_inline void *
+__cache_alloc(struct kmem_cache *cachep, gfp_t flags, void *caller)
 {
 	unsigned long save_flags;
 	void *objp;
@@ -2710,7 +2711,7 @@ static inline void *__cache_alloc(struct
 	objp = ____cache_alloc(cachep, flags);
 	local_irq_restore(save_flags);
 	objp = cache_alloc_debugcheck_after(cachep, flags, objp,
-					    __builtin_return_address(0));
+					    caller);
 	prefetchw(objp);
 	return objp;
 }
@@ -2939,7 +2940,7 @@ static inline void __cache_free(struct k
  */
 void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
 {
-	return __cache_alloc(cachep, flags);
+	return __cache_alloc(cachep, flags, __builtin_return_address(0));
 }
 EXPORT_SYMBOL(kmem_cache_alloc);
 
@@ -3053,7 +3054,7 @@ EXPORT_SYMBOL(kmalloc_node);
  * platforms.  For example, on i386, it means that the memory must come
  * from the first 16MB.
  */
-void *__kmalloc(size_t size, gfp_t flags)
+static inline void *__do_kmalloc(size_t size, gfp_t flags, void *caller)
 {
 	struct kmem_cache *cachep;
 
@@ -3065,10 +3066,27 @@ void *__kmalloc(size_t size, gfp_t flags
 	cachep = __find_general_cachep(size, flags);
 	if (unlikely(cachep == NULL))
 		return NULL;
-	return __cache_alloc(cachep, flags);
+	return __cache_alloc(cachep, flags, caller);
+}
+
+#ifndef CONFIG_DEBUG_SLAB
+
+void *__kmalloc(size_t size, gfp_t flags)
+{
+	return __do_kmalloc(size, flags, NULL);
 }
 EXPORT_SYMBOL(__kmalloc);
 
+#else
+
+void *__kmalloc_track_caller(size_t size, gfp_t flags, void *caller)
+{
+	return __do_kmalloc(size, flags, caller);
+}
+EXPORT_SYMBOL(__kmalloc_track_caller);
+
+#endif
+
 #ifdef CONFIG_SMP
 /**
  * __alloc_percpu - allocate one copy of the object for every present