Re: [RFC 3/4] Add checks to current destructor uses

[Christoph Lameter <clameter@sgi.com>]

On Thu, 22 Jun 2006, Pekka J Enberg wrote:

> On Mon, 19 Jun 2006, Christoph Lameter wrote:
> > slab: Add checks to current destructor uses
> > 
> > We will be adding new destructor options soon. So insure that all
> > existing destructors only react to SLAB_DTOR_DESTROY.
> 
> Hmm, I don't see the slab allocator passing SLAB_DTOR_DESTROY anywhere in 
> this patch?  Please don't introduce changesets that break the kernel.  
> It's bad for stuff like git bisect.

Correct. Thanks.

Fixed up patch:

slab: Add checks to current destructor uses

We will be adding new destructor options soon. So insure that all
existing destructors only react to SLAB_DTOR_DESTROY.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.17/arch/i386/mm/pgtable.c
===================================================================
--- linux-2.6.17.orig/arch/i386/mm/pgtable.c	2006-06-17 18:49:35.000000000 -0700
+++ linux-2.6.17/arch/i386/mm/pgtable.c	2006-06-22 12:38:29.179955802 -0700
@@ -226,15 +226,19 @@ void pgd_ctor(void *pgd, kmem_cache_t *c
 }
 
 /* never called when PTRS_PER_PMD > 1 */
-void pgd_dtor(void *pgd, kmem_cache_t *cache, unsigned long unused)
+void pgd_dtor(void *pgd, kmem_cache_t *cache, unsigned long slab_flags)
 {
 	unsigned long flags; /* can be called from interrupt context */
 
+	if (!(slab_flags & SLAB_DTOR_DESTROY))
+		return;
+
 	spin_lock_irqsave(&pgd_lock, flags);
 	pgd_list_del(pgd);
 	spin_unlock_irqrestore(&pgd_lock, flags);
 }
 
+
 pgd_t *pgd_alloc(struct mm_struct *mm)
 {
 	int i;
Index: linux-2.6.17/include/linux/slab.h
===================================================================
--- linux-2.6.17.orig/include/linux/slab.h	2006-06-17 18:49:35.000000000 -0700
+++ linux-2.6.17/include/linux/slab.h	2006-06-22 12:38:29.180932304 -0700
@@ -53,6 +53,9 @@ typedef struct kmem_cache kmem_cache_t;
 #define SLAB_CTOR_ATOMIC	0x002UL		/* tell constructor it can't sleep */
 #define	SLAB_CTOR_VERIFY	0x004UL		/* tell constructor it's a verify call */
 
+/* flags passed to a constructor func */
+#define SLAB_DTOR_DESTROY	0x1000UL	/* Called during slab destruction */
+
 #ifndef CONFIG_SLOB
 
 /* prototypes */
Index: linux-2.6.17/arch/frv/mm/pgalloc.c
===================================================================
--- linux-2.6.17.orig/arch/frv/mm/pgalloc.c	2006-06-17 18:49:35.000000000 -0700
+++ linux-2.6.17/arch/frv/mm/pgalloc.c	2006-06-22 12:38:29.212180365 -0700
@@ -120,10 +120,13 @@ void pgd_ctor(void *pgd, kmem_cache_t *c
 }
 
 /* never called when PTRS_PER_PMD > 1 */
-void pgd_dtor(void *pgd, kmem_cache_t *cache, unsigned long unused)
+void pgd_dtor(void *pgd, kmem_cache_t *cache, unsigned long slab_flags)
 {
 	unsigned long flags; /* can be called from interrupt context */
 
+	if (!(slab_flags & SLAB_DTOR_DESTROY))
+		return;
+
 	spin_lock_irqsave(&pgd_lock, flags);
 	pgd_list_del(pgd);
 	spin_unlock_irqrestore(&pgd_lock, flags);
Index: linux-2.6.17/mm/slab.c
===================================================================
--- linux-2.6.17.orig/mm/slab.c	2006-06-22 12:35:58.685386714 -0700
+++ linux-2.6.17/mm/slab.c	2006-06-22 12:39:37.971586394 -0700
@@ -1689,7 +1689,8 @@ static void slab_destroy_objs(struct kme
 					   "was overwritten");
 		}
 		if (cachep->dtor && !(cachep->flags & SLAB_POISON))
-			(cachep->dtor) (objp + obj_offset(cachep), cachep, 0);
+			(cachep->dtor) (objp + obj_offset(cachep), cachep,
+				SLAB_DTOR_DESTROY);
 	}
 }
 #else
@@ -1699,7 +1700,7 @@ static void slab_destroy_objs(struct kme
 		int i;
 		for (i = 0; i < cachep->num; i++) {
 			void *objp = index_to_obj(cachep, slabp, i);
-			(cachep->dtor) (objp, cachep, 0);
+			(cachep->dtor) (objp, cachep, SLAB_DTOR_DESTROY);
 		}
 	}
 }
@@ -2661,7 +2662,8 @@ static void *cache_free_debugcheck(struc
 		/* we want to cache poison the object,
 		 * call the destruction callback
 		 */
-		cachep->dtor(objp + obj_offset(cachep), cachep, 0);
+		cachep->dtor(objp + obj_offset(cachep), cachep,
+			SLAB_DTOR_DESTROY);
 	}
 #ifdef CONFIG_DEBUG_SLAB_LEAK
 	slab_bufctl(slabp)[objnr] = BUFCTL_FREE;
-
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