Slab allocators: Drop support for destructors
There is no user of destructors left. There is no reason why we should keep
checking for destructors calls in the slab allocators.
The RFC for this patch was discussed at
http://marc.info/?l=linux-kernel&m=117882364330705&w=2
Destructors were mainly used for list management which required them to take a
spinlock. Taking a spinlock in a destructor is a bit risky since the slab
allocators may run the destructors anytime they decide a slab is no longer
needed.
Patch drops destructor support. Any attempt to use a destructor will BUG().
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slab.c b/mm/slab.c
index 944b205..1234443 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -409,9 +409,6 @@
/* constructor func */
void (*ctor) (void *, struct kmem_cache *, unsigned long);
- /* de-constructor func */
- void (*dtor) (void *, struct kmem_cache *, unsigned long);
-
/* 5) cache creation/removal */
const char *name;
struct list_head next;
@@ -1911,20 +1908,11 @@
slab_error(cachep, "end of a freed object "
"was overwritten");
}
- if (cachep->dtor && !(cachep->flags & SLAB_POISON))
- (cachep->dtor) (objp + obj_offset(cachep), cachep, 0);
}
}
#else
static void slab_destroy_objs(struct kmem_cache *cachep, struct slab *slabp)
{
- if (cachep->dtor) {
- int i;
- for (i = 0; i < cachep->num; i++) {
- void *objp = index_to_obj(cachep, slabp, i);
- (cachep->dtor) (objp, cachep, 0);
- }
- }
}
#endif
@@ -2124,7 +2112,7 @@
* @align: The required alignment for the objects.
* @flags: SLAB flags
* @ctor: A constructor for the objects.
- * @dtor: A destructor for the objects.
+ * @dtor: A destructor for the objects (not implemented anymore).
*
* Returns a ptr to the cache on success, NULL on failure.
* Cannot be called within a int, but can be interrupted.
@@ -2159,7 +2147,7 @@
* Sanity checks... these are all serious usage bugs.
*/
if (!name || in_interrupt() || (size < BYTES_PER_WORD) ||
- (size > (1 << MAX_OBJ_ORDER) * PAGE_SIZE) || (dtor && !ctor)) {
+ (size > (1 << MAX_OBJ_ORDER) * PAGE_SIZE) || dtor) {
printk(KERN_ERR "%s: Early error in slab %s\n", __FUNCTION__,
name);
BUG();
@@ -2213,9 +2201,6 @@
if (flags & SLAB_DESTROY_BY_RCU)
BUG_ON(flags & SLAB_POISON);
#endif
- if (flags & SLAB_DESTROY_BY_RCU)
- BUG_ON(dtor);
-
/*
* Always checks flags, a caller might be expecting debug support which
* isn't available.
@@ -2370,7 +2355,6 @@
BUG_ON(!cachep->slabp_cache);
}
cachep->ctor = ctor;
- cachep->dtor = dtor;
cachep->name = name;
if (setup_cpu_cache(cachep)) {
@@ -2835,7 +2819,6 @@
* Perform extra freeing checks:
* - detect bad pointers.
* - POISON/RED_ZONE checking
- * - destructor calls, for caches with POISON+dtor
*/
static void kfree_debugcheck(const void *objp)
{
@@ -2894,12 +2877,6 @@
BUG_ON(objnr >= cachep->num);
BUG_ON(objp != index_to_obj(cachep, slabp, objnr));
- if (cachep->flags & SLAB_POISON && cachep->dtor) {
- /* we want to cache poison the object,
- * call the destruction callback
- */
- cachep->dtor(objp + obj_offset(cachep), cachep, 0);
- }
#ifdef CONFIG_DEBUG_SLAB_LEAK
slab_bufctl(slabp)[objnr] = BUFCTL_FREE;
#endif