linux-kernel - Re: [PATCH] tools/vm/slabinfo: Handle files in debugfs

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Message-ID: <29914f07-6ee5-a562-2b8e-ed15c861f3eb@suse.cz>
Date:   Mon, 4 Apr 2022 15:40:44 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Stéphane Graber <stgraber@...ntu.com>,
        linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Faiyaz Mohammed <faiyazm@...eaurora.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH] tools/vm/slabinfo: Handle files in debugfs

On 3/31/22 16:03, Stéphane Graber wrote:
> Commit 64dd68497be76 relocated and renamed the alloc_calls and
> free_calls files from /sys/kernel/slab/NAME/*_calls over to
> /sys/kernel/debug/slab/NAME/*_calls but didn't update the slabinfo tool
> with the new location.
> 
> This change will now have slabinfo look at the new location (and filenames)
> with a fallback to the prior files.
> 
> Fixes: 64dd68497be76 ("mm: slub: move sysfs slab alloc/free interfaces to debugfs")
> Cc: stable@...r.kernel.org
> Signed-off-by: Stéphane Graber <stgraber@...ntu.com>
> Tested-by: Stéphane Graber <stgraber@...ntu.com>
> ---
>  tools/vm/slabinfo.c | 26 ++++++++++++++++++++++++--
>  1 file changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/vm/slabinfo.c b/tools/vm/slabinfo.c
> index 9b68658b6bb8..5b98f3ee58a5 100644
> --- a/tools/vm/slabinfo.c
> +++ b/tools/vm/slabinfo.c
> @@ -233,6 +233,24 @@ static unsigned long read_slab_obj(struct slabinfo *s, const char *name)
>  	return l;
>  }
>  
> +static unsigned long read_debug_slab_obj(struct slabinfo *s, const char *name)
> +{
> +	char x[128];
> +	FILE *f;
> +	size_t l;
> +
> +	snprintf(x, 128, "/sys/kernel/debug/slab/%s/%s", s->name, name);
> +	f = fopen(x, "r");
> +	if (!f) {
> +		buffer[0] = 0;
> +		l = 0;
> +	} else {
> +		l = fread(buffer, 1, sizeof(buffer), f);
> +		buffer[l] = 0;
> +		fclose(f);
> +	}
> +	return l;
> +}

slabinfo is not the nicest code already, but still this basically duplicates
read_slab_obj() just to add a prefix to the path, so it could be done in a
unified way?

>  
>  /*
>   * Put a size string together
> @@ -409,14 +427,18 @@ static void show_tracking(struct slabinfo *s)
>  {
>  	printf("\n%s: Kernel object allocation\n", s->name);
>  	printf("-----------------------------------------------------------------------\n");
> -	if (read_slab_obj(s, "alloc_calls"))
> +	if (read_debug_slab_obj(s, "alloc_traces"))
> +		printf("%s", buffer);
> +	else if (read_slab_obj(s, "alloc_calls"))
>  		printf("%s", buffer);
>  	else
>  		printf("No Data\n");
>  
>  	printf("\n%s: Kernel object freeing\n", s->name);
>  	printf("------------------------------------------------------------------------\n");
> -	if (read_slab_obj(s, "free_calls"))
> +	if (read_debug_slab_obj(s, "free_traces"))
> +		printf("%s", buffer);
> +	else if (read_slab_obj(s, "free_calls"))
>  		printf("%s", buffer);
>  	else
>  		printf("No Data\n");