linux-kernel - Re: [PATCH] slab: Add allow_spin check to eliminate kmemleak warnings

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Message-ID: <b23bcee1-bc5e-427a-904b-7f3b1f4766b1@suse.cz>
Date: Fri, 3 Oct 2025 09:51:45 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: ranxiaokai627@....com, akpm@...ux-foundation.org, cl@...two.org,
 rientjes@...gle.com, roman.gushchin@...ux.dev, harry.yoo@...cle.com,
 ast@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, ran.xiaokai@....com.cn
Subject: Re: [PATCH] slab: Add allow_spin check to eliminate kmemleak warnings

On 9/30/25 08:38, ranxiaokai627@....com wrote:
> From: Ran Xiaokai <ran.xiaokai@....com.cn>
> 
> In slab_post_alloc_hook(), kmemleak check is skipped when
> gfpflags_allow_spinning() returns false since commit 13d872ade8be
> ("slab: Introduce kmalloc_nolock() and kfree_nolock().").
> Therefore, unconditionally calling kmemleak_not_leak() in
> alloc_slab_obj_exts() would trigger the following warning:
> 
> kmemleak: Trying to color unknown object at 0xffff8881057f5000 as Grey
> Call Trace:
>  alloc_slab_obj_exts+0x1b5/0x370
>  __alloc_tagging_slab_alloc_hook+0x9f/0x2d0
>  __kmalloc_cache_noprof+0x1c4/0x5c0
>  __set_page_owner+0x10d/0x1c0
>  post_alloc_hook+0x84/0xf0
>  get_page_from_freelist+0x73b/0x1380
>  __alloc_frozen_pages_noprof+0x110/0x2c0
>  alloc_pages_mpol+0x44/0x140
>  alloc_slab_page+0xac/0x150
>  allocate_slab+0x78/0x3a0
>  ___slab_alloc+0x76b/0xed0
>  __slab_alloc.constprop.0+0x5a/0xb0
> 
> Add the allow_spin check in alloc_slab_obj_exts() to
> eliminate the above warning.
> 
> Fixes: 13d872ade8be ("slab: Introduce kmalloc_nolock() and kfree_nolock().")

Updated commit hash (also above)

> Signed-off-by: Ran Xiaokai <ran.xiaokai@....com.cn>

Added to slab/for-next-fixes, thanks!

> ---
>  mm/slub.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 09cbe580842c..a76275f4870a 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2145,7 +2145,8 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
>  		return 0;
>  	}
>  
> -	kmemleak_not_leak(vec);
> +	if (allow_spin)
> +		kmemleak_not_leak(vec);
>  	return 0;
>  }
>