linux-kernel - Re: [PATCH v6 1/4] mm/slub: enable debugging memory wasting of kmalloc

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Date:   Tue, 1 Nov 2022 15:57:46 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     John Thomson <lists@...nthomson.fastmail.com.au>
CC:     Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Andrey Konovalov <andreyknvl@...il.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
        Robin Murphy <robin.murphy@....com>,
        John Garry <john.garry@...wei.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>,
        <linux-mips@...r.kernel.org>
Subject: Re: [PATCH v6 1/4] mm/slub: enable debugging memory wasting of
 kmalloc

Hi Thomson,

Thanks for testing!

+ mips maintainer and mail list. The original report is here

https://lore.kernel.org/lkml/becf2ac3-2a90-4f3a-96d9-a70f67c66e4a@app.fastmail.com/

On Tue, Nov 01, 2022 at 12:18:19AM +0000, John Thomson wrote:
> > As I can't reproduce it locally yet, could you help try 3 tests separately:
> > * change the O2/O3 compile option to O1
> > * try the attached 0001 patch (which cut part of commit)
> > * try attached 0001+0002 patch
> 
> None of these changed my outcome.

0001 patch chops off most of the functional changes, and it still
fails. I'm wondering if it is related to the function arguments'
passing, I noticed this is a 32 bits MIPS platform (from your config)   

> I also tried compiling the same linux tree & config with the Bootlin toolchain
> (mipsel-buildroot-linux-gnu-gcc.br_real (Buildroot 2021.11-4428-g6b6741b) 12.2.0)
> with the same results.
> I will look into finding or building a mips clang toolchain.
 
Yes, Hyeonggon's suggestion makes sense, different compiler may
show some difference.

> No JTAG capability to debug, sorry.
> 
> I get the same outcome with either the ZBOOT vmlinuz, or vmlinux
> 
> Same happening with 6.1-rc3
> 
> 
> After some blind poking around changing (how much of the commit affected) mm/slub.c,
> I may have got lucky. it appears as though this is all I need to boot:
> (against 6.1-rc3), and with the Bootlin toolchain. Will test my other build system as well.
> 
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3276,7 +3276,7 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>         c = slub_get_cpu_ptr(s->cpu_slab);
>  #endif
>  
> -       p = ___slab_alloc(s, gfpflags, node, addr, c, orig_size);
> +       p = ___slab_alloc(s, gfpflags, node, addr, c, 0);

___slab_alloc()'s argument number has been changed from 5 to 6, and
some others from 4 to 5.

Thanks,
Feng


>  #ifdef CONFIG_PREEMPT_COUNT
>         slub_put_cpu_ptr(s->cpu_slab);
>  #endif