Re: kmem_cache_attr (was Re: [PATCH 04/36] usercopy: Prepare for usercopy whitelisting)

From: Matthew Wilcox
Date: Tue Jan 16 2018 - 16:03:27 EST


On Tue, Jan 16, 2018 at 12:17:01PM -0600, Christopher Lameter wrote:
> Draft patch of how the data structs could change. kmem_cache_attr is read
> only.

Looks good. Although I would add Kees' user feature:

struct kmem_cache_attr {
char name[16];
unsigned int size;
unsigned int align;
+ unsigned int useroffset;
+ unsigned int usersize;
slab_flags_t flags;
kmem_cache_ctor ctor;
}

And I'd start with
+struct kmem_cache *kmem_cache_create_attr(const kmem_cache_attr *);

leaving the old kmem_cache_create to kmalloc a kmem_cache_attr and
initialise it.

Can we also do something like this?

-#define KMEM_CACHE(__struct, __flags) kmem_cache_create(#__struct,\
- sizeof(struct __struct), __alignof__(struct __struct),\
- (__flags), NULL)
+#define KMEM_CACHE(__struct, __flags) ({ \
+ const struct kmem_cache_attr kca ## __stringify(__struct) = { \
+ .name = #__struct, \
+ .size = sizeof(struct __struct), \
+ .align = __alignof__(struct __struct), \
+ .flags = (__flags), \
+ }; \
+ kmem_cache_create_attr(&kca ## __stringify(__struct)); \
+})

That way we won't need to convert any of those users.