Re: [PATCH v3 1/2] mm: Provide empty function for kmem_dump_obj() when CONFIG_PRINTK=n

[Matthew Wilcox]

On Wed, Aug 02, 2023 at 11:45:16AM +0800, thunder.leizhen@xxxxxxxxxxxxxxx wrote:
> +++ b/include/linux/slab.h
> @@ -246,6 +246,9 @@ size_t ksize(const void *objp);
>  #ifdef CONFIG_PRINTK
>  bool kmem_valid_obj(void *object);
>  void kmem_dump_obj(void *object);
> +#else
> +static inline bool kmem_valid_obj(void *object) { return false; }

That is very confusing.  kmem_valid_obj() looks like a function which
should exist regardless of CONFIG_PRINTK and to have it always return
false if CONFIG_PRINTK isn't set seems weird.

I see we have one caller of kmem_valid_obj() right now.  Which means it
shouldn't be an EXPORT_SYMBOL since that caller is not a module.

I think the right solution is to convert kmem_dump_obj() to
work the same way as vmalloc_dump_obj().  ie:

+++ b/mm/util.c
@@ -1057,11 +1057,8 @@ 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;

... with corresponding changes to eliminate kmem_valid_obj() as a
symbol.