linux-kernel - Re: [PATCH] mm/huge_memory.c: introduce folio_split

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Message-ID: <60B3DC06-7135-4410-BBDD-9D7B914598CE@nvidia.com>
Date: Fri, 14 Nov 2025 21:36:07 -0500
From: Zi Yan <ziy@...dia.com>
To: Balbir Singh <balbirs@...dia.com>
Cc: kernel test robot <lkp@...el.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, dri-devel@...ts.freedesktop.org, llvm@...ts.linux.dev,
 oe-kbuild-all@...ts.linux.dev, Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>, Joshua Hahn <joshua.hahnjy@...il.com>,
 Rakie Kim <rakie.kim@...com>, Byungchul Park <byungchul@...com>,
 Gregory Price <gourry@...rry.net>, Ying Huang <ying.huang@...ux.alibaba.com>,
 Alistair Popple <apopple@...dia.com>, Oscar Salvador <osalvador@...e.de>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>,
 Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
 Barry Song <baohua@...nel.org>, Lyude Paul <lyude@...hat.com>,
 Danilo Krummrich <dakr@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Ralph Campbell <rcampbell@...dia.com>,
 Mika Penttilä <mpenttil@...hat.com>,
 Matthew Brost <matthew.brost@...el.com>,
 Francois Dugast <francois.dugast@...el.com>
Subject: Re: [PATCH] mm/huge_memory.c: introduce folio_split_unmapped

On 14 Nov 2025, at 21:33, Balbir Singh wrote:

> On 11/15/25 13:15, kernel test robot wrote:
>> Hi Balbir,
>>
>> kernel test robot noticed the following build warnings:
>>
>> [auto build test WARNING on akpm-mm/mm-everything]
>>
>> url:    https://github.com/intel-lab-lkp/linux/commits/Balbir-Singh/mm-huge_memory-c-introduce-folio_split_unmapped/20251114-093541
>> base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
>> patch link:    https://lore.kernel.org/r/20251114012228.2634882-1-balbirs%40nvidia.com
>> patch subject: [PATCH] mm/huge_memory.c: introduce folio_split_unmapped
>> config: arm64-randconfig-002-20251115 (https://download.01.org/0day-ci/archive/20251115/202511151007.F1gixfc8-lkp@intel.com/config)
>> compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff)
>> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251115/202511151007.F1gixfc8-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/202511151007.F1gixfc8-lkp@intel.com/
>>
>> All warnings (new ones prefixed by >>):
>>
>>>> mm/huge_memory.c:3751:6: warning: variable 'nr_shmem_dropped' set but not used [-Wunused-but-set-variable]
>>     3751 |         int nr_shmem_dropped = 0;
>>          |             ^
>>    1 warning generated.
>>
>>
>> vim +/nr_shmem_dropped +3751 mm/huge_memory.c
>>
>
> [...]
>
> Thanks for the report, I'll send an updated version after I investigate it

nr_shmem_dropped is updated in __folio_freeze_and_split_unmapped() but
is used in its caller. It needs to be passed into __folio_freeze_and_split_unmapped().

--
Best Regards,
Yan, Zi