linux-kernel - Re: [PATCH 1/4] mm/swap, memcg: Introduce infrastructure for cgroup-based swap priority

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Message-ID: <aH+csQxNcCmQMgZa@yjaykim-PowerEdge-T330>
Date: Tue, 22 Jul 2025 23:14:09 +0900
From: YoungJun Park <youngjun.park@....com>
To: kernel test robot <lkp@...el.com>
Cc: akpm@...ux-foundation.org, hannes@...xchg.org,
	oe-kbuild-all@...ts.linux.dev, mhocko@...nel.org,
	roman.gushchin@...ux.dev, shakeel.butt@...ux.dev,
	muchun.song@...ux.dev, shikemeng@...weicloud.com,
	kasong@...cent.com, nphamcs@...il.com, bhe@...hat.com,
	baohua@...nel.org, chrisl@...nel.org, cgroups@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, gunho.lee@....com,
	iamjoonsoo.kim@....com, taejoon.song@....com,
	Michal Koutný <mkoutny@...e.com>
Subject: Re: [PATCH 1/4] mm/swap, memcg: Introduce infrastructure for
 cgroup-based swap priority

On Mon, Jul 21, 2025 at 11:13:24PM +0800, kernel test robot wrote:
> Hi Youngjun,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on 347e9f5043c89695b01e66b3ed111755afcf1911]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Youngjun-Park/mm-swap-memcg-Introduce-infrastructure-for-cgroup-based-swap-priority/20250717-042648
> base:   347e9f5043c89695b01e66b3ed111755afcf1911
> patch link:    https://lore.kernel.org/r/20250716202006.3640584-2-youngjun.park%40lge.com
> patch subject: [PATCH 1/4] mm/swap, memcg: Introduce infrastructure for cgroup-based swap priority
> config: loongarch-randconfig-r123-20250721 (https://download.01.org/0day-ci/archive/20250721/202507212243.Lf8fSo0T-lkp@intel.com/config)
> compiler: clang version 19.1.7 (https://github.com/llvm/llvm-project cd708029e0b2869e80abe31ddb175f7c35361f90)
> reproduce: (https://download.01.org/0day-ci/archive/20250721/202507212243.Lf8fSo0T-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202507212243.Lf8fSo0T-lkp@intel.com/
> 
> sparse warnings: (new ones prefixed by >>)
> >> mm/swap_cgroup_priority.c:115:16: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    mm/swap_cgroup_priority.c:115:16: sparse:    struct swap_cgroup_priority [noderef] __rcu *
>    mm/swap_cgroup_priority.c:115:16: sparse:    struct swap_cgroup_priority *
>    mm/swap_cgroup_priority.c:729:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    mm/swap_cgroup_priority.c:729:9: sparse:    struct swap_cgroup_priority [noderef] __rcu *
>    mm/swap_cgroup_priority.c:729:9: sparse:    struct swap_cgroup_priority *
>    mm/swap_cgroup_priority.c:638:25: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    mm/swap_cgroup_priority.c:638:25: sparse:    struct swap_cgroup_priority [noderef] __rcu *
>    mm/swap_cgroup_priority.c:638:25: sparse:    struct swap_cgroup_priority *
> 
> vim +115 mm/swap_cgroup_priority.c
> 
>    108	
>    109	static struct swap_cgroup_priority *get_swap_cgroup_priority(
>    110		struct mem_cgroup *memcg)
>    111	{
>    112		if (!memcg)
>    113			return NULL;
>    114	
>  > 115		return rcu_dereference(memcg->swap_priority);
>    116	}
>    117	
> 

This part of the code, which retrieves the object, 
is expected to be properly updated in a subsequent patch series. 
Therefore, I believe it's reasonable to leave it as-is for now.

Best Regard,
Youngjun Park