On Tue, Jun 25, 2024 at 7:24 AM Vlastimil Babka <vbabka@xxxxxxx> wrote: > > On 6/20/24 12:49 AM, Vlastimil Babka wrote: > > --- a/mm/slub.c > > +++ b/mm/slub.c > > @@ -3874,13 +3874,37 @@ static __always_inline void maybe_wipe_obj_freeptr(struct kmem_cache *s, > > 0, sizeof(void *)); > > } > > > > -noinline int should_failslab(struct kmem_cache *s, gfp_t gfpflags) > > +#if defined(CONFIG_FUNCTION_ERROR_INJECTION) || defined(CONFIG_FAILSLAB) > > +DEFINE_STATIC_KEY_FALSE(should_failslab_active); > > + > > +#ifdef CONFIG_FUNCTION_ERROR_INJECTION > > +noinline > > +#else > > +static inline > > +#endif > > +int should_failslab(struct kmem_cache *s, gfp_t gfpflags) > > Note that it has been found that (regardless of this series) gcc may clone > this to a should_failslab.constprop.0 in case the function is empty because > __should_failslab is compiled out (CONFIG_FAILSLAB=n). The "noinline" > doesn't help - the original function stays but only the clone is actually > being called, thus overriding the original function achieves nothing, see: > https://github.com/bpftrace/bpftrace/issues/3258 > > So we could use __noclone to prevent that, and I was thinking by adding > something this to error-injection.h: > > #ifdef CONFIG_FUNCTION_ERROR_INJECTION > #define __error_injectable(alternative) noinline __noclone To prevent such compiler transformations we typically use __used noinline We didn't have a need for __noclone yet. If __used is enough I'd stick to that.
