Re: [PATCH v7] mm: slub: move sysfs slab alloc/free interfaces to debugfs

[Faiyaz Mohammed]

On 5/25/2021 1:23 PM, Greg KH wrote:
> On Tue, May 25, 2021 at 01:08:05PM +0530, Faiyaz Mohammed wrote:
>> alloc_calls and free_calls implementation in sysfs have two issues,
>> one is PAGE_SIZE limitiation of sysfs and other is it does not adhere
>> to "one value per file" rule.
>>
>> To overcome this issues, move the alloc_calls and free_calls implemeation
>> to debugfs.
>>
>> Rename the alloc_calls/free_calls to alloc_traces/free_traces,
>> to be inline with what it does.
>>
>> Reported-by: kernel test robot <lkp@xxxxxxxxx>
>> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>> Signed-off-by: Faiyaz Mohammed <faiyazm@xxxxxxxxxxxxxx>
>> ---
>> changes in V7:
>>         - Drop the older alloc_calls and free_calls interface.
>> changes in v6:
>>         - https://lore.kernel.org/linux-mm/1621341949-26762-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/
>>
>> changes in v5:
>>         - https://lore.kernel.org/linux-mm/1620296523-21922-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/
>>
>> changes in v4:
>>         - https://lore.kernel.org/linux-mm/1618583239-18124-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/
>>
>> changes in v3:
>>         - https://lore.kernel.org/linux-mm/1617712064-12264-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/
>>
>> changes in v2:
>>         - https://lore.kernel.org/linux-mm/3ac1d3e6-6207-96ad-16a1-0f5139d8b2b5@xxxxxxxxxxxxxx/
>>
>> changes in v1:
>>         - https://lore.kernel.org/linux-mm/1610443287-23933-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/
>>
>>  include/linux/slub_def.h |   8 ++
>>  mm/slab_common.c         |   9 ++
>>  mm/slub.c                | 353 ++++++++++++++++++++++++++++++++++-------------
>>  3 files changed, 276 insertions(+), 94 deletions(-)
>>
>> diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
>> index dcde82a..b413ebe 100644
>> --- a/include/linux/slub_def.h
>> +++ b/include/linux/slub_def.h
>> @@ -159,6 +159,14 @@ static inline void sysfs_slab_release(struct kmem_cache *s)
>>  }
>>  #endif
>>  
>> +#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SLUB_DEBUG)
>> +#define SLAB_SUPPORTS_DEBUGFS
>> +void debugfs_slab_release(struct kmem_cache *);
>> +#else
>> +static inline void debugfs_slab_release(struct kmem_cache *s)
>> +{
>> +}
>> +#endif
>>  void object_err(struct kmem_cache *s, struct page *page,
>>  		u8 *object, char *reason);
>>  
>> diff --git a/mm/slab_common.c b/mm/slab_common.c
>> index a4a5714..873dd79 100644
>> --- a/mm/slab_common.c
>> +++ b/mm/slab_common.c
>> @@ -455,6 +455,9 @@ static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
>>  #else
>>  		slab_kmem_cache_release(s);
>>  #endif
>> +#ifdef SLAB_SUPPORTS_DEBUGFS
>> +		debugfs_slab_release(s);
>> +#endif
> 
> Why do you need these #ifdef if your slub_dev.h file already provides an
> "empty" function for this?
> 
We are not including slub_def.h directly. mm/slab.h includes the
slub_def.h if CONFIG_SLUB enable,

from mm/slab.h
#ifdef CONFIG_SLAB
#include <linux/slab_def.h>
#endif

#ifdef CONFIG_SLUB
#include <linux/slub_def.h>
#endif

so if CONFIG_SLAB is enable then mm/slab.h includes slab_def.h, to avoid
undefined reference error added SLAB_SUPPORTS_DEBUGFS like
SLAB_SUPPORTS_SYSFS.
>>  	}
>>  }
>>  
>> @@ -472,6 +475,9 @@ static int shutdown_cache(struct kmem_cache *s)
>>  #ifdef SLAB_SUPPORTS_SYSFS
>>  		sysfs_slab_unlink(s);
>>  #endif
>> +#ifdef SLAB_SUPPORTS_DEBUGFS
>> +		debugfs_slab_release(s);
>> +#endif
> 
> Same here.
> 
>>  		list_add_tail(&s->list, &slab_caches_to_rcu_destroy);
>>  		schedule_work(&slab_caches_to_rcu_destroy_work);
>>  	} else {
>> @@ -482,6 +488,9 @@ static int shutdown_cache(struct kmem_cache *s)
>>  #else
>>  		slab_kmem_cache_release(s);
>>  #endif
>> +#ifdef SLAB_SUPPORTS_DEBUGFS
>> +		debugfs_slab_release(s);
>> +#endif
> 
> And here.
> 
> What is wrong with your .h file that keeps the need for #ifdef in the .c
> file?
> 
> I thought I've asked about this a number of times in the past, what am I
> missing?
> 
> thanks,
> 
> greg k-h
>