On Sun, 11 Aug 2024, Pedro Falcato wrote:
> > > diff --git a/mm/slab_common.c b/mm/slab_common.c
> > > index 40b582a014b..1abe6a577d5 100644
> > > --- a/mm/slab_common.c
> > > +++ b/mm/slab_common.c
> > > @@ -88,6 +88,19 @@ unsigned int kmem_cache_size(struct kmem_cache *s)
> > > EXPORT_SYMBOL(kmem_cache_size);
> > >
> > > #ifdef CONFIG_DEBUG_VM
> > > +
> > > +static bool kmem_cache_is_duplicate_name(const char *name)
> > > +{
> > > + struct kmem_cache *s;
> > > +
> > > + list_for_each_entry(s, &slab_caches, list) {
> > > + if (!strcmp(s->name, name))
> > > + return true;
> > > + }
> > > +
> > > + return false;
> > > +}
> > > +
> > > static int kmem_cache_sanity_check(const char *name, unsigned int size)
> > > {
> > > if (!name || in_interrupt() || size > KMALLOC_MAX_SIZE) {
> > > @@ -95,6 +108,11 @@ static int kmem_cache_sanity_check(const char *name, unsigned int size)
> > > return -EINVAL;
> > > }
> > >
> > > + if (kmem_cache_is_duplicate_name(name)) {
> > > + /* Duplicate names will confuse slabtop, et al */
> > > + pr_warn("%s: name %s already exists as a cache\n", __func__, name);
> >
> >
> > Shouldn't this be a full WARN_ON() instead of pr_warn()? I assume we'll
> > be interested in who is adding the cache when the name already exists.
>
> panic_on_warn? :)
>
Would get the problem fixed up pretty fast, no? :)
> Personally I don't have anything against WARN_ON, but we've seen that
> panic_on_warn is a real thing on real systems, and DEBUG_VM is also
> set on real prod configs (like Fedora does/used to do). I've sent out
> one or two loose patches for problems I did find in my own testing
> around, but there may be many more (e.g some drivers may call
> kmem_cache_create repeatedly in some sort of callback, like 9pfs was
> doing when mounting; this is not greppable). And I'd guess grepping
> for cache names tends to be easy enough?
>
Can we add a dump_stack() to make this way easier instead of hiding who is
creating the duplicate name?
