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Subject[PATCH] slab: object to index mapping cleanup
From: Pekka Enberg <penberg@cs.helsinki.fi>

This patch cleans up the object to index mapping that has been spread around
mm/slab.c.

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

mm/slab.c | 34 +++++++++++++++++++++++-----------
1 file changed, 23 insertions(+), 11 deletions(-)

Index: 2.6-git/mm/slab.c
===================================================================
--- 2.6-git.orig/mm/slab.c
+++ 2.6-git/mm/slab.c
@@ -608,6 +608,18 @@ static inline struct slab *virt_to_slab(
return page_get_slab(page);
}

+static inline void *index_to_obj(struct kmem_cache *cache, struct slab *slab,
+ unsigned int idx)
+{
+ return slab->s_mem + cache->buffer_size * idx;
+}
+
+static inline unsigned int obj_to_index(struct kmem_cache *cache,
+ struct slab *slab, void *obj)
+{
+ return (unsigned)(obj - slab->s_mem) / cache->buffer_size;
+}
+
/* These are the default caches for kmalloc. Custom caches can have other sizes. */
struct cache_sizes malloc_sizes[] = {
#define CACHE(x) { .cs_size = (x) },
@@ -1450,18 +1462,18 @@ static void check_poison_obj(struct kmem
* exist:
*/
struct slab *slabp = virt_to_slab(objp);
- int objnr;
+ unsigned int objnr;

- objnr = (unsigned)(objp - slabp->s_mem) / cachep->buffer_size;
+ objnr = obj_to_index(cachep, slabp, objp);
if (objnr) {
- objp = slabp->s_mem + (objnr - 1) * cachep->buffer_size;
+ objp = index_to_obj(cachep, slabp, objnr - 1);
realobj = (char *)objp + obj_offset(cachep);
printk(KERN_ERR "Prev obj: start=%p, len=%d\n",
realobj, size);
print_objinfo(cachep, objp, 2);
}
if (objnr + 1 < cachep->num) {
- objp = slabp->s_mem + (objnr + 1) * cachep->buffer_size;
+ objp = index_to_obj(cachep, slabp, objnr + 1);
realobj = (char *)objp + obj_offset(cachep);
printk(KERN_ERR "Next obj: start=%p, len=%d\n",
realobj, size);
@@ -1480,7 +1492,7 @@ static void slab_destroy_objs(struct kme
{
int i;
for (i = 0; i < cachep->num; i++) {
- void *objp = slabp->s_mem + cachep->buffer_size * i;
+ void *objp = index_to_obj(cachep, slabp, i);

if (cachep->flags & SLAB_POISON) {
#ifdef CONFIG_DEBUG_PAGEALLOC
@@ -1513,7 +1525,7 @@ static void slab_destroy_objs(struct kme
if (cachep->dtor) {
int i;
for (i = 0; i < cachep->num; i++) {
- void *objp = slabp->s_mem + cachep->buffer_size * i;
+ void *objp = index_to_obj(cachep, slabp, i);
(cachep->dtor) (objp, cachep, 0);
}
}
@@ -2189,7 +2201,7 @@ static void cache_init_objs(struct kmem_
int i;

for (i = 0; i < cachep->num; i++) {
- void *objp = slabp->s_mem + cachep->buffer_size * i;
+ void *objp = index_to_obj(cachep, slabp, i);
#if DEBUG
/* need to poison the objs? */
if (cachep->flags & SLAB_POISON)
@@ -2245,7 +2257,7 @@ static void kmem_flagcheck(struct kmem_c

static void *slab_get_obj(struct kmem_cache *cachep, struct slab *slabp, int nodeid)
{
- void *objp = slabp->s_mem + (slabp->free * cachep->buffer_size);
+ void *objp = index_to_obj(cachep, slabp, slabp->free);
kmem_bufctl_t next;

slabp->inuse++;
@@ -2262,7 +2274,7 @@ static void *slab_get_obj(struct kmem_ca
static void slab_put_obj(struct kmem_cache *cachep, struct slab *slabp, void *objp,
int nodeid)
{
- unsigned int objnr = (unsigned)(objp-slabp->s_mem) / cachep->buffer_size;
+ unsigned int objnr = obj_to_index(cachep, slabp, objp);

#if DEBUG
/* Verify that the slab belongs to the intended node */
@@ -2448,10 +2460,10 @@ static void *cache_free_debugcheck(struc
if (cachep->flags & SLAB_STORE_USER)
*dbg_userword(cachep, objp) = caller;

- objnr = (unsigned)(objp - slabp->s_mem) / cachep->buffer_size;
+ objnr = obj_to_index(cachep, slabp, objp);

BUG_ON(objnr >= cachep->num);
- BUG_ON(objp != slabp->s_mem + objnr * cachep->buffer_size);
+ BUG_ON(objp != index_to_obj(cachep, slabp, objnr));

if (cachep->flags & SLAB_DEBUG_INITIAL) {
/* Need to call the slab's constructor so the
-
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