Re: [PATCH 2/2] mm/slub: Fix slab_mutex circular locking problem in slab_attr_store()

[Waiman Long]

On 4/24/20 12:16 PM, Qian Cai wrote:
> > On Apr 24, 2020, at 11:12 AM, Waiman Long <longman@xxxxxxxxxx> wrote:
> >
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 183ccc364ccf..255981180489 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -5567,13 +5567,30 @@ static ssize_t slab_attr_store(struct kobject *kobj,
> > 		return -EIO;
> >
> > 	err = attribute->store(s, buf, len);
> > -#ifdef CONFIG_MEMCG
> > -	if (slab_state >= FULL && err >= 0 && is_root_cache(s)) {
> > -		struct kmem_cache *c;
> > +#ifdef CONFIG_MEMCG_KMEM
> > +	if (slab_state >= FULL && err >= 0 && is_root_cache(s) &&
> > +	    !list_empty(&s->memcg_params.children)) {
> > +		struct kmem_cache *c, **pcaches;
> > +		int idx, max, cnt = 0;
> > +		size_t size = s->max_attr_size;
> > +		struct memcg_cache_array *arr;
> > +
> > +		/*
> > +		 * Make atomic update to s->max_attr_size.
> > +		 */
> > +		do {
> > +			if (len <= size)
> > +				break;
> > +		} while (!try_cmpxchg(&s->max_attr_size, &size, len));
> try_cmpxchg() is only available on x86.
>
> mm/slub.c: In function âslab_attr_storeâ:
> mm/slub.c:5613:13: error: implicit declaration of function âtry_cmpxchgâ; did you mean âxa_cmpxchgâ? [-Werror=implicit-function-declaration]
>     } while (!try_cmpxchg(&s->max_attr_size, &size, len));
>               ^~~~~~~~~~~
>               xa_cmpxchg
Oh, sorry about that. Will fix it and send out v2.

Cheers,
Longman