linux-kernel - Re: [PATCH v6] mm: slub: move sysfs slab alloc/free interfaces to debugfs

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Date:   Fri, 21 May 2021 13:13:51 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Faiyaz Mohammed <faiyazm@...eaurora.org>, cl@...ux.com,
        penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, glittao@...il.com, greg@...ah.com
Cc:     vinmenon@...eaurora.org
Subject: Re: [PATCH v6] mm: slub: move sysfs slab alloc/free interfaces to
 debugfs

On 5/18/21 2:45 PM, 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>


> @@ -5817,6 +5769,249 @@ static int __init slab_sysfs_init(void)
>  __initcall(slab_sysfs_init);
>  #endif /* CONFIG_SYSFS */
>  
> +#if defined(CONFIG_SLUB_DEBUG) && defined(CONFIG_DEBUG_FS)
> +static int debugfs_slab_alias(struct kmem_cache *s, const char *name)
> +{
> +	struct saved_alias *al;
> +	struct dentry *slab_cache_dir;
> +
> +	if (slab_state == FULL) {
> +		/*
> +		 * If we have a leftover link then remove it.
> +		 */
> +		slab_cache_dir = debugfs_lookup(s->name, slab_debugfs_root);
> +		debugfs_remove(slab_cache_dir);
> +		debugfs_create_symlink(name, slab_debugfs_root, NULL);

v6 got stuck on boot for me, unlike v5, seems like here you should return 0?
That helped

> +	}
> +
> +	al = kmalloc(sizeof(struct saved_alias), GFP_KERNEL);
> +	if (!al)
> +		return -ENOMEM;
> +
> +	al->s = s;
> +	al->name = name;
> +	al->next = alias_list;
> +	alias_list = al;
> +	return 0;
> +}
> +