[Devel] Re: [PATCH v2 06/13] slab: Add kmem_cache_gfp_flags() helper function.

[Glauber Costa]

On 03/14/2012 03:21 AM, Suleiman Souhlal wrote:
> On Sun, Mar 11, 2012 at 3:53 AM, Glauber Costa<glommer at parallels.com>  wrote:
>> On 03/10/2012 12:39 AM, Suleiman Souhlal wrote:
>>>
>>> This function returns the gfp flags that are always applied to
>>> allocations of a kmem_cache.
>>>
>>> Signed-off-by: Suleiman Souhlal<suleiman at google.com>
>>> ---
>>>   include/linux/slab_def.h |    6 ++++++
>>>   include/linux/slob_def.h |    6 ++++++
>>>   include/linux/slub_def.h |    6 ++++++
>>>   3 files changed, 18 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
>>> index fbd1117..25f9a6a 100644
>>> --- a/include/linux/slab_def.h
>>> +++ b/include/linux/slab_def.h
>>> @@ -159,6 +159,12 @@ found:
>>>         return __kmalloc(size, flags);
>>>   }
>>>
>>> +static inline gfp_t
>>> +kmem_cache_gfp_flags(struct kmem_cache *cachep)
>>> +{
>>> +       return cachep->gfpflags;
>>> +}
>>> +
>>>   #ifdef CONFIG_NUMA
>>>   extern void *__kmalloc_node(size_t size, gfp_t flags, int node);
>>>   extern void *kmem_cache_alloc_node(struct kmem_cache *, gfp_t flags, int
>>> node);
>>> diff --git a/include/linux/slob_def.h b/include/linux/slob_def.h
>>> index 0ec00b3..3fa527d 100644
>>> --- a/include/linux/slob_def.h
>>> +++ b/include/linux/slob_def.h
>>> @@ -34,4 +34,10 @@ static __always_inline void *__kmalloc(size_t size,
>>> gfp_t flags)
>>>         return kmalloc(size, flags);
>>>   }
>>>
>>> +static inline gfp_t
>>> +kmem_cache_gfp_flags(struct kmem_cache *cachep)
>>> +{
>>> +       return 0;
>>> +}
>>> +
>>>   #endif /* __LINUX_SLOB_DEF_H */
>>> diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
>>> index a32bcfd..5911d81 100644
>>> --- a/include/linux/slub_def.h
>>> +++ b/include/linux/slub_def.h
>>> @@ -313,4 +313,10 @@ static __always_inline void *kmalloc_node(size_t
>>> size, gfp_t flags, int node)
>>>   }
>>>   #endif
>>>
>>> +static inline gfp_t
>>> +kmem_cache_gfp_flags(struct kmem_cache *cachep)
>>> +{
>>> +       return cachep->allocflags;
>>> +}
>>> +
>>
>>
>> Why is this needed? Can't the caller just call
>> mem_cgroup_get_kmem_cache(cachep, flags | cachep->allocflags) ?
>
> Because slub calls this cachep->allocflags, while slab calls it
> cachep->gfpflags.
>

So what?
That function is only called from slab.c anyway. Let slab call it
mem_cgroup_get_kmem_cache(cachep, flags | cachep->allocflags);
and slub
mem_cgroup_get_kmem_cache(cachep, flags | cachep->gfpflags);