linux-kernel - Re: [PATCH] mm: slub: fix format mismatches in slab

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Date:	Wed, 5 Nov 2014 13:48:42 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Andrey Ryabinin <a.ryabinin@...sung.com>
cc:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH] mm: slub: fix format mismatches in slab_err() callers

On Wed, 5 Nov 2014, Andrey Ryabinin wrote:

> Adding __printf(3, 4) to slab_err exposed following:
> 
> mm/slub.c: In function ‘check_slab’:
> mm/slub.c:852:4: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 4 has type ‘const char *’ [-Wformat=]
>     s->name, page->objects, maxobj);
>     ^
> mm/slub.c:852:4: warning: too many arguments for format [-Wformat-extra-args]
> mm/slub.c:857:4: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 4 has type ‘const char *’ [-Wformat=]
>     s->name, page->inuse, page->objects);
>     ^
> mm/slub.c:857:4: warning: too many arguments for format [-Wformat-extra-args]
> 

Wow, that's an ancient issue, thanks for finding it.

> mm/slub.c: In function ‘on_freelist’:
> mm/slub.c:905:4: warning: format ‘%d’ expects argument of type ‘int’, but argument 5 has type ‘long unsigned int’ [-Wformat=]
>     "should be %d", page->objects, max_objects);
> 
> Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Pekka Enberg <penberg@...nel.org>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> ---
>  mm/slub.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 80c170e..850a94a 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -849,12 +849,12 @@ static int check_slab(struct kmem_cache *s, struct page *page)
>  	maxobj = order_objects(compound_order(page), s->size, s->reserved);
>  	if (page->objects > maxobj) {
>  		slab_err(s, page, "objects %u > max %u",
> -			s->name, page->objects, maxobj);
> +			page->objects, maxobj);
>  		return 0;
>  	}
>  	if (page->inuse > page->objects) {
>  		slab_err(s, page, "inuse %u > max %u",
> -			s->name, page->inuse, page->objects);
> +			page->inuse, page->objects);
>  		return 0;
>  	}
>  	/* Slab_pad_check fixes things up after itself */
> @@ -902,7 +902,7 @@ static int on_freelist(struct kmem_cache *s, struct page *page, void *search)
>  
>  	if (page->objects != max_objects) {
>  		slab_err(s, page, "Wrong number of objects. Found %d but "
> -			"should be %d", page->objects, max_objects);
> +			"should be %ld", page->objects, max_objects);
>  		page->objects = max_objects;
>  		slab_fix(s, "Number of objects adjusted.");
>  	}

Instead of this hunk, I think that max_objects should be declared as int 
rather than unsigned long since that's what order_objects() returns and it 
is being compared to page->objects which is also int.