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 #else #define __error_injectable(alternative) alternative #endif and the usage here would be: __error_injectable(static inline) int should_failslab(...) Does that look acceptable, or is it too confusing that "static inline" is specified there as the storage class to use when error injection is actually disabled? > { > if (__should_failslab(s, gfpflags)) > return -ENOMEM; > return 0; > } > -ALLOW_ERROR_INJECTION(should_failslab, ERRNO); > +ALLOW_ERROR_INJECTION_KEY(should_failslab, ERRNO, &should_failslab_active); > + > +static __always_inline int should_failslab_wrapped(struct kmem_cache *s, > + gfp_t gfp) > +{ > + if (static_branch_unlikely(&should_failslab_active)) > + return should_failslab(s, gfp); > + else > + return 0; > +} > +#else > +static __always_inline int should_failslab_wrapped(struct kmem_cache *s, > + gfp_t gfp) > +{ > + return false; > +} > +#endif > > static __fastpath_inline > struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s, gfp_t flags) > @@ -3889,7 +3913,7 @@ struct kmem_cache *slab_pre_alloc_hook(struct > kmem_cache *s, gfp_t flags) > > might_alloc(flags); > > - if (unlikely(should_failslab(s, flags))) > + if (should_failslab_wrapped(s, flags)) > return NULL; > > return s; >
