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

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Date:   Tue, 25 May 2021 09:53:23 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Faiyaz Mohammed <faiyazm@...eaurora.org>
Cc:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org, vbabka@...e.cz,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        glittao@...il.com, vinmenon@...eaurora.org
Subject: Re: [PATCH v7] mm: slub: move sysfs slab alloc/free interfaces to
 debugfs

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@...el.com>
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> Signed-off-by: Faiyaz Mohammed <faiyazm@...eaurora.org>
> ---
> 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@codeaurora.org/
> 
> changes in v5:
>         - https://lore.kernel.org/linux-mm/1620296523-21922-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in v4:
>         - https://lore.kernel.org/linux-mm/1618583239-18124-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in v3:
>         - https://lore.kernel.org/linux-mm/1617712064-12264-1-git-send-email-faiyazm@codeaurora.org/
> 
> changes in v2:
>         - https://lore.kernel.org/linux-mm/3ac1d3e6-6207-96ad-16a1-0f5139d8b2b5@codeaurora.org/
> 
> changes in v1:
>         - https://lore.kernel.org/linux-mm/1610443287-23933-1-git-send-email-faiyazm@codeaurora.org/
> 
>  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?

>  	}
>  }
>  
> @@ -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