[PATCH RFC 04/12] mm/slab: make slab_obj_ext() determine object index

["Vlastimil Babka (SUSE)" <vbabka@kernel.org>]

All callers perform the same obj_to_index() calculation to pass the
index. Simplify by passing object pointer instead and determining the
index by slab_obj_ext().

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/memcontrol.c | 12 +++---------
 mm/slab.h       | 14 ++++++++------
 mm/slub.c       | 22 +++++++---------------
 3 files changed, 18 insertions(+), 30 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6dc4888a90f3..4e427286a88a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2865,15 +2865,13 @@ struct mem_cgroup *mem_cgroup_from_obj_slab(struct slab *slab, void *p)
 	 */
 	unsigned long obj_exts;
 	struct slabobj_ext *obj_ext;
-	unsigned int off;
 
 	obj_exts = slab_obj_exts(slab);
 	if (!obj_exts)
 		return NULL;
 
 	get_slab_obj_exts(obj_exts);
-	off = obj_to_index(slab->slab_cache, slab, p);
-	obj_ext = slab_obj_ext(slab, obj_exts, off);
+	obj_ext = slab_obj_ext(slab->slab_cache, slab, obj_exts, p);
 	if (obj_ext->objcg) {
 		struct obj_cgroup *objcg = obj_ext->objcg;
 
@@ -3541,7 +3539,6 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
 	size_t obj_size = obj_full_size(s);
 	struct obj_cgroup *objcg;
 	struct slab *slab;
-	unsigned long off;
 	size_t i;
 
 	/*
@@ -3616,8 +3613,7 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
 
 		obj_exts = slab_obj_exts(slab);
 		get_slab_obj_exts(obj_exts);
-		off = obj_to_index(s, slab, p[i]);
-		obj_ext = slab_obj_ext(slab, obj_exts, off);
+		obj_ext = slab_obj_ext(s, slab, obj_exts, p[i]);
 		obj_cgroup_get(objcg);
 		obj_ext->objcg = objcg;
 		put_slab_obj_exts(obj_exts);
@@ -3635,10 +3631,8 @@ void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,
 		struct obj_cgroup *objcg;
 		struct slabobj_ext *obj_ext;
 		struct obj_stock_pcp *stock;
-		unsigned int off;
 
-		off = obj_to_index(s, slab, p[i]);
-		obj_ext = slab_obj_ext(slab, obj_exts, off);
+		obj_ext = slab_obj_ext(s, slab, obj_exts, p[i]);
 		objcg = obj_ext->objcg;
 		if (!objcg)
 			continue;
diff --git a/mm/slab.h b/mm/slab.h
index 7bd361447c54..36d067d6e7c0 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -646,14 +646,16 @@ static inline unsigned int slab_get_stride(struct slab *slab)
  * Returns a pointer to the object extension associated with the object.
  * Must be called within a section covered by get/put_slab_obj_exts().
  */
-static inline struct slabobj_ext *slab_obj_ext(struct slab *slab,
-					       unsigned long obj_exts,
-					       unsigned int index)
+static inline struct slabobj_ext *
+slab_obj_ext(struct kmem_cache *s, struct slab *slab, unsigned long obj_exts,
+	     const void *obj)
 {
 	struct slabobj_ext *obj_ext;
+	unsigned int index;
 
 	VM_WARN_ON_ONCE(obj_exts != slab_obj_exts(slab));
 
+	index = obj_to_index(s, slab, obj);
 	obj_ext = (struct slabobj_ext *)(obj_exts +
 					 slab_get_stride(slab) * index);
 	return kasan_reset_tag(obj_ext);
@@ -669,9 +671,9 @@ static inline unsigned long slab_obj_exts(struct slab *slab)
 	return 0;
 }
 
-static inline struct slabobj_ext *slab_obj_ext(struct slab *slab,
-					       unsigned long obj_exts,
-					       unsigned int index)
+static inline struct slabobj_ext *
+slab_obj_ext(struct kmem_cache *s, struct slab *slab, unsigned long obj_exts,
+	     const void *obj)
 {
 	return NULL;
 }
diff --git a/mm/slub.c b/mm/slub.c
index 9e25f2dce7a6..5e3f53bcd0d3 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2070,11 +2070,10 @@ static inline void mark_obj_codetag_empty(const void *obj)
 	obj_slab = virt_to_slab(obj);
 	slab_exts = slab_obj_exts(obj_slab);
 	if (slab_exts) {
+		struct slabobj_ext *ext;
+
 		get_slab_obj_exts(slab_exts);
-		unsigned int offs = obj_to_index(obj_slab->slab_cache,
-						 obj_slab, obj);
-		struct slabobj_ext *ext = slab_obj_ext(obj_slab,
-						       slab_exts, offs);
+		ext = slab_obj_ext(obj_slab->slab_cache, obj_slab, slab_exts, obj);
 
 		if (unlikely(is_codetag_empty(&ext->ref))) {
 			put_slab_obj_exts(slab_exts);
@@ -2362,10 +2361,8 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags,
 	 * check should be added before alloc_tag_add().
 	 */
 	if (obj_exts) {
-		unsigned int obj_idx = obj_to_index(s, slab, object);
-
 		get_slab_obj_exts(obj_exts);
-		obj_ext = slab_obj_ext(slab, obj_exts, obj_idx);
+		obj_ext = slab_obj_ext(s, slab, obj_exts, object);
 		alloc_tag_add(&obj_ext->ref, current->alloc_tag, s->size);
 		put_slab_obj_exts(obj_exts);
 	} else {
@@ -2386,7 +2383,6 @@ static noinline void
 __alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,
 			       int objects)
 {
-	int i;
 	unsigned long obj_exts;
 
 	/* slab->obj_exts might not be NULL if it was created for MEMCG accounting. */
@@ -2398,13 +2394,11 @@ __alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p
 		return;
 
 	get_slab_obj_exts(obj_exts);
-	for (i = 0; i < objects; i++) {
-		unsigned int off = obj_to_index(s, slab, p[i]);
-
+	for (int i = 0; i < objects; i++) {
 		if (is_kfence_address(p[i]))
 			continue;
 
-		alloc_tag_sub(&slab_obj_ext(slab, obj_exts, off)->ref, s->size);
+		alloc_tag_sub(&slab_obj_ext(s, slab, obj_exts, p[i])->ref, s->size);
 	}
 	put_slab_obj_exts(obj_exts);
 }
@@ -2489,7 +2483,6 @@ bool memcg_slab_post_charge(void *p, gfp_t flags)
 	struct kmem_cache *s;
 	struct page *page;
 	struct slab *slab;
-	unsigned long off;
 
 	page = virt_to_page(p);
 	if (PageLargeKmalloc(page)) {
@@ -2529,8 +2522,7 @@ bool memcg_slab_post_charge(void *p, gfp_t flags)
 	obj_exts = slab_obj_exts(slab);
 	if (obj_exts) {
 		get_slab_obj_exts(obj_exts);
-		off = obj_to_index(s, slab, p);
-		obj_ext = slab_obj_ext(slab, obj_exts, off);
+		obj_ext = slab_obj_ext(s, slab, obj_exts, p);
 		if (unlikely(obj_ext->objcg)) {
 			put_slab_obj_exts(obj_exts);
 			return true;

-- 
2.55.0