mm: Remove kmem_valid_obj()

Function kmem_dump_obj() will splat if passed a pointer to a non-slab
object. So nothing calls it directly, instead calling kmem_valid_obj()
first to determine whether the passed pointer to a valid slab object. This
means that merging kmem_valid_obj() into kmem_dump_obj() will make the
code more concise. Therefore, convert kmem_dump_obj() to work the same
way as vmalloc_dump_obj(), removing the need for the kmem_dump_obj()
caller to check kmem_valid_obj().  After this, there are no remaining
calls to kmem_valid_obj() anymore, and it can be safely removed.

Suggested-by: Matthew Wilcox <[email protected]>
Signed-off-by: Zhen Lei <[email protected]>
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>

Author: Zhen Lei

include/linux/slab.h

@@ -245,8 +245,9 @@ DEFINE_FREE(kfree, void *, if (_T) kfree(_T))
 size_t ksize(const void *objp);
 
 #ifdef CONFIG_PRINTK
-bool kmem_valid_obj(void *object);
-void kmem_dump_obj(void *object);
+bool kmem_dump_obj(void *object);
+#else
+static inline bool kmem_dump_obj(void *object) { return false; }
 #endif
 
 /*

mm/slab_common.c

@@ -528,26 +528,6 @@ bool slab_is_available(void)
 }
 
 #ifdef CONFIG_PRINTK
-/**
- * kmem_valid_obj - does the pointer reference a valid slab object?
- * @object: pointer to query.
- *
- * Return: %true if the pointer is to a not-yet-freed object from
- * kmalloc() or kmem_cache_alloc(), either %true or %false if the pointer
- * is to an already-freed object, and %false otherwise.
- */
-bool kmem_valid_obj(void *object)
-{
-	struct folio *folio;
-
-	/* Some arches consider ZERO_SIZE_PTR to be a valid address. */
-	if (object < (void *)PAGE_SIZE || !virt_addr_valid(object))
-		return false;
-	folio = virt_to_folio(object);
-	return folio_test_slab(folio);
-}
-EXPORT_SYMBOL_GPL(kmem_valid_obj);
-
 static void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
 {
 	if (__kfence_obj_info(kpp, object, slab))
@@ -566,25 +546,25 @@ static void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *
  * and, if available, the slab name, return address, and stack trace from
  * the allocation and last free path of that object.
  *
- * This function will splat if passed a pointer to a non-slab object.
- * If you are not sure what type of object you have, you should instead
- * use mem_dump_obj().
+ * Return: %true if the pointer is to a not-yet-freed object from
+ * kmalloc() or kmem_cache_alloc(), either %true or %false if the pointer
+ * is to an already-freed object, and %false otherwise.
  */
-void kmem_dump_obj(void *object)
+bool kmem_dump_obj(void *object)
 {
 	char *cp = IS_ENABLED(CONFIG_MMU) ? "" : "/vmalloc";
 	int i;
 	struct slab *slab;
 	unsigned long ptroffset;
 	struct kmem_obj_info kp = { };
 
-	if (WARN_ON_ONCE(!virt_addr_valid(object)))
-		return;
+	/* Some arches consider ZERO_SIZE_PTR to be a valid address. */
+	if (object < (void *)PAGE_SIZE || !virt_addr_valid(object))
+		return false;
 	slab = virt_to_slab(object);
-	if (WARN_ON_ONCE(!slab)) {
-		pr_cont(" non-slab memory.\n");
-		return;
-	}
+	if (!slab)
+		return false;
+
 	kmem_obj_info(&kp, object, slab);
 	if (kp.kp_slab_cache)
 		pr_cont(" slab%s %s", cp, kp.kp_slab_cache->name);
@@ -621,6 +601,7 @@ void kmem_dump_obj(void *object)
 		pr_info("    %pS\n", kp.kp_free_stack[i]);
 	}
 
+	return true;
 }
 EXPORT_SYMBOL_GPL(kmem_dump_obj);
 #endif

mm/util.c

@@ -1060,10 +1060,8 @@ void mem_dump_obj(void *object)
 {
 	const char *type;
 
-	if (kmem_valid_obj(object)) {
-		kmem_dump_obj(object);
+	if (kmem_dump_obj(object))
 		return;
-	}
 
 	if (vmalloc_dump_obj(object))
 		return;