On Tue, 5 Oct 2021 09:31:43 -0600 Jens Axboe <axboe@xxxxxxxxx> wrote:
> Allocations can be a very hot path, and this out-of-line function
> call is noticeable.
>
> --- a/include/linux/fault-inject.h
> +++ b/include/linux/fault-inject.h
> @@ -64,8 +64,8 @@ static inline struct dentry *fault_create_debugfs_attr(const char *name,
>
> struct kmem_cache;
>
> -int should_failslab(struct kmem_cache *s, gfp_t gfpflags);
> #ifdef CONFIG_FAILSLAB
> +int should_failslab(struct kmem_cache *s, gfp_t gfpflags);
> extern bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags);
> #else
> static inline bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
> diff --git a/mm/slab.h b/mm/slab.h
> index 58c01a34e5b8..92fd6fe01877 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -491,8 +491,10 @@ static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s,
>
> might_alloc(flags);
>
> +#ifdef CONFIG_FAILSLAB
> if (should_failslab(s, flags))
> return NULL;
> +#endif
Can we avoid the ifdefs here?
>
> if (!memcg_slab_pre_alloc_hook(s, objcgp, size, flags))
> return NULL;
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index ec2bb0beed75..c21bd447f237 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -1323,6 +1323,7 @@ EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc_node);
> EXPORT_TRACEPOINT_SYMBOL(kfree);
> EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);
>
> +#ifdef CONFIG_FAILSLAB
> int should_failslab(struct kmem_cache *s, gfp_t gfpflags)
> {
> if (__should_failslab(s, gfpflags))
> @@ -1330,3 +1331,4 @@ int should_failslab(struct kmem_cache *s, gfp_t gfpflags)
> return 0;
> }
> ALLOW_ERROR_INJECTION(should_failslab, ERRNO);
> +#endif
Like,
--- a/include/linux/fault-inject.h~mm-dont-call-should_failslab-for-config_failslab-fix
+++ a/include/linux/fault-inject.h
@@ -68,6 +68,10 @@ struct kmem_cache;
int should_failslab(struct kmem_cache *s, gfp_t gfpflags);
extern bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags);
#else
+static inline int should_failslab(struct kmem_cache *s, gfp_t gfpflags)
+{
+ return 0;
+}
static inline bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
{
return false;
--- a/mm/slab.h~mm-dont-call-should_failslab-for-config_failslab-fix
+++ a/mm/slab.h
@@ -491,10 +491,8 @@ static inline struct kmem_cache *slab_pr
might_alloc(flags);
-#ifdef CONFIG_FAILSLAB
if (should_failslab(s, flags))
return NULL;
-#endif
if (!memcg_slab_pre_alloc_hook(s, objcgp, size, flags))
return NULL;
_
