On Fri, Sep 30, 2022 at 10:47:42AM +0200, Rasmus Villemoes wrote:
> The function sysfs_slab_add() has two callers:
>
> One is slab_sysfs_init(), which first initializes slab_kset, and only
> when that succeeds sets slab_state to FULL, and then proceeds to call
> sysfs_slab_add() for all previously created slabs.
>
> The other is __kmem_cache_create(), but only after a
>
> if (slab_state <= UP)
> return 0;
>
> check.
>
> So in other words, sysfs_slab_add() is never called without
> slab_kset (aka the return value of cache_kset()) being non-NULL.
>
> And this is just as well, because if we ever did take this path and
> called kobject_init(&s->kobj), and then later when called again from
> slab_sysfs_init() would end up calling kobject_init_and_add(), we
> would hit
>
> if (kobj->state_initialized) {
> /* do not error out as sometimes we can recover */
> pr_err("kobject (%p): tried to init an initialized object, something is seriously wrong.\n",
> dump_stack();
> }
>
> in kobject.c.
>
> Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
> ---
> mm/slub.c | 5 -----
> 1 file changed, 5 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 4b98dff9be8e..04a7f75a7b1f 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -5937,11 +5937,6 @@ static int sysfs_slab_add(struct kmem_cache *s)
> struct kset *kset = cache_kset(s);
> int unmergeable = slab_unmergeable(s);
>
> - if (!kset) {
> - kobject_init(&s->kobj, &slab_ktype);
> - return 0;
> - }
> -
> if (!unmergeable && disable_higher_order_debug &&
> (slub_debug & DEBUG_METADATA_FLAGS))
> unmergeable = 1;
> --
> 2.37.2
I assumed that it's hit when SLUB failed to initialize slab_kset in
slab_sysfs_init(). (Yeah, it is too unlikely, though....)
And obviously it's a bug if sysfs_slab_add() is called early than
slab_sysfs_init().
--
Thanks,
Hyeonggon
