linux-kernel - Re: [PATCH 18/20] mm/slub: remove slab_alloc() and __kmem_cache_alloc

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Date:   Tue, 14 Nov 2023 21:31:03 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Kees Cook <keescook@...omium.org>
Cc:     David Rientjes <rientjes@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Marco Elver <elver@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        kasan-dev@...glegroups.com, cgroups@...r.kernel.org
Subject: Re: [PATCH 18/20] mm/slub: remove slab_alloc() and
 __kmem_cache_alloc_lru() wrappers

On 11/14/23 05:50, Kees Cook wrote:
> On Mon, Nov 13, 2023 at 08:13:59PM +0100, Vlastimil Babka wrote:
>> slab_alloc() is a thin wrapper around slab_alloc_node() with only one
>> caller.  Replace with direct call of slab_alloc_node().
>> __kmem_cache_alloc_lru() itself is a thin wrapper with two callers,
>> so replace it with direct calls of slab_alloc_node() and
>> trace_kmem_cache_alloc().
> 
> I'd have a sense that with 2 callers a wrapper is still useful?

Well it bothered me how many layers everything went through, it makes it
harder to comprehend the code.

>> 
>> This also makes sure _RET_IP_ has always the expected value and not
>> depending on inlining decisions.

And there's also this argument. We should evaluate _RET_IP_ in
kmem_cache_alloc() and kmem_cache_alloc_lru().

>> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
>> [...]
>>  void *kmem_cache_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node)
>>  {
>> -	void *ret = slab_alloc_node(s, NULL, gfpflags, node, _RET_IP_, s->object_size);
>> +	void *ret = slab_alloc_node(s, NULL, gfpflags, node, _RET_IP_,
>> +				    s->object_size);
>>  
> 
> Whitespace change here isn't mentioned in the commit log.

OK, will mention.

> Regardless:
> 
> Reviewed-by: Kees Cook <keescook@...omium.org>

Thanks!