[PATCH v2 16/21] mm/slab: move kfree() from slab_common.c to slub.c

[Vlastimil Babka]

This should result in better code. Currently kfree() makes a function
call between compilation units to __kmem_cache_free() which does its own
virt_to_slab(), throwing away the struct slab pointer we already had in
kfree(). Now it can be reused. Additionally kfree() can now inline the
whole SLUB freeing fastpath.

Also move over free_large_kmalloc() as the only callsites are now in
slub.c, and make it static.

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
 mm/slab.h        |  4 ----
 mm/slab_common.c | 45 ---------------------------------------------
 mm/slub.c        | 51 ++++++++++++++++++++++++++++++++++++++++++++++-----
 3 files changed, 46 insertions(+), 54 deletions(-)

diff --git a/mm/slab.h b/mm/slab.h
index 5ae6a978e9c2..35a55c4a407d 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -395,8 +395,6 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags, unsigned long caller);
 void *__kmem_cache_alloc_node(struct kmem_cache *s, gfp_t gfpflags,
 			      int node, size_t orig_size,
 			      unsigned long caller);
-void __kmem_cache_free(struct kmem_cache *s, void *x, unsigned long caller);
-
 gfp_t kmalloc_fix_flags(gfp_t flags);
 
 /* Functions provided by the slab allocators */
@@ -559,8 +557,6 @@ static inline int memcg_alloc_slab_cgroups(struct slab *slab,
 }
 #endif /* CONFIG_MEMCG_KMEM */
 
-void free_large_kmalloc(struct folio *folio, void *object);
-
 size_t __ksize(const void *objp);
 
 static inline size_t slab_ksize(const struct kmem_cache *s)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index bbc2e3f061f1..f4f275613d2a 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -963,22 +963,6 @@ void __init create_kmalloc_caches(slab_flags_t flags)
 	slab_state = UP;
 }
 
-void free_large_kmalloc(struct folio *folio, void *object)
-{
-	unsigned int order = folio_order(folio);
-
-	if (WARN_ON_ONCE(order == 0))
-		pr_warn_once("object pointer: 0x%p\n", object);
-
-	kmemleak_free(object);
-	kasan_kfree_large(object);
-	kmsan_kfree_large(object);
-
-	mod_lruvec_page_state(folio_page(folio, 0), NR_SLAB_UNRECLAIMABLE_B,
-			      -(PAGE_SIZE << order));
-	__free_pages(folio_page(folio, 0), order);
-}
-
 static void *__kmalloc_large_node(size_t size, gfp_t flags, int node);
 static __always_inline
 void *__do_kmalloc_node(size_t size, gfp_t flags, int node, unsigned long caller)
@@ -1023,35 +1007,6 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t flags,
 }
 EXPORT_SYMBOL(__kmalloc_node_track_caller);
 
-/**
- * kfree - free previously allocated memory
- * @object: pointer returned by kmalloc() or kmem_cache_alloc()
- *
- * If @object is NULL, no operation is performed.
- */
-void kfree(const void *object)
-{
-	struct folio *folio;
-	struct slab *slab;
-	struct kmem_cache *s;
-
-	trace_kfree(_RET_IP_, object);
-
-	if (unlikely(ZERO_OR_NULL_PTR(object)))
-		return;
-
-	folio = virt_to_folio(object);
-	if (unlikely(!folio_test_slab(folio))) {
-		free_large_kmalloc(folio, (void *)object);
-		return;
-	}
-
-	slab = folio_slab(folio);
-	s = slab->slab_cache;
-	__kmem_cache_free(s, (void *)object, _RET_IP_);
-}
-EXPORT_SYMBOL(kfree);
-
 /**
  * __ksize -- Report full size of underlying allocation
  * @object: pointer to the object
diff --git a/mm/slub.c b/mm/slub.c
index cc801f8258fe..2baa9e94d9df 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4197,11 +4197,6 @@ static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
 	return cachep;
 }
 
-void __kmem_cache_free(struct kmem_cache *s, void *x, unsigned long caller)
-{
-	slab_free(s, virt_to_slab(x), x, NULL, &x, 1, caller);
-}
-
 /**
  * kmem_cache_free - Deallocate an object
  * @s: The cache the allocation was from.
@@ -4220,6 +4215,52 @@ void kmem_cache_free(struct kmem_cache *s, void *x)
 }
 EXPORT_SYMBOL(kmem_cache_free);
 
+static void free_large_kmalloc(struct folio *folio, void *object)
+{
+	unsigned int order = folio_order(folio);
+
+	if (WARN_ON_ONCE(order == 0))
+		pr_warn_once("object pointer: 0x%p\n", object);
+
+	kmemleak_free(object);
+	kasan_kfree_large(object);
+	kmsan_kfree_large(object);
+
+	mod_lruvec_page_state(folio_page(folio, 0), NR_SLAB_UNRECLAIMABLE_B,
+			      -(PAGE_SIZE << order));
+	__free_pages(folio_page(folio, 0), order);
+}
+
+/**
+ * kfree - free previously allocated memory
+ * @object: pointer returned by kmalloc() or kmem_cache_alloc()
+ *
+ * If @object is NULL, no operation is performed.
+ */
+void kfree(const void *object)
+{
+	struct folio *folio;
+	struct slab *slab;
+	struct kmem_cache *s;
+	void *x = (void *)object;
+
+	trace_kfree(_RET_IP_, object);
+
+	if (unlikely(ZERO_OR_NULL_PTR(object)))
+		return;
+
+	folio = virt_to_folio(object);
+	if (unlikely(!folio_test_slab(folio))) {
+		free_large_kmalloc(folio, (void *)object);
+		return;
+	}
+
+	slab = folio_slab(folio);
+	s = slab->slab_cache;
+	slab_free(s, slab, x, NULL, &x, 1, _RET_IP_);
+}
+EXPORT_SYMBOL(kfree);
+
 struct detached_freelist {
 	struct slab *slab;
 	void *tail;

-- 
2.42.1