On 10/5/21 3:18 PM, Andrew Morton wrote:
> 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;
> _
Yep, that'll work!
--
Jens Axboe
