linux-kernel - Re: [PATCH v3 1/2] lib/sbitmap: convert shallow

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Message-ID: <98e3bdfc-41ed-40b6-92df-4aacab3d92c5@kernel.dk>
Date: Wed, 6 Aug 2025 20:19:09 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Yu Kuai <yukuai1@...weicloud.com>, kernel test robot <lkp@...el.com>,
 akpm@...ux-foundation.org, ming.lei@...hat.com, dlemoal@...nel.org,
 jack@...e.cz
Cc: oe-kbuild-all@...ts.linux.dev, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com,
 johnny.chenyi@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v3 1/2] lib/sbitmap: convert shallow_depth from one word
 to the whole sbitmap

On 8/6/25 7:30 PM, Yu Kuai wrote:
> Hi,
> 
> ? 2025/08/06 17:41, kernel test robot ??:
>> All error/warnings (new ones prefixed by >>):
>>
>>     In file included from ./arch/sparc/include/generated/asm/div64.h:1,
>>                      from include/linux/math.h:6,
>>                      from include/linux/kernel.h:27,
>>                      from include/linux/cpumask.h:11,
>>                      from arch/sparc/include/asm/smp_32.h:15,
>>                      from arch/sparc/include/asm/smp.h:7,
>>                      from arch/sparc/include/asm/switch_to_32.h:5,
>>                      from arch/sparc/include/asm/switch_to.h:7,
>>                      from arch/sparc/include/asm/ptrace.h:120,
>>                      from arch/sparc/include/asm/thread_info_32.h:19,
>>                      from arch/sparc/include/asm/thread_info.h:7,
>>                      from include/linux/thread_info.h:60,
>>                      from arch/sparc/include/asm/current.h:15,
>>                      from include/linux/sched.h:12,
>>                      from lib/sbitmap.c:7:
>>     lib/sbitmap.c: In function '__map_depth_with_shallow':
>>     include/asm-generic/div64.h:183:35: warning: comparison of distinct pointer types lacks a cast
>>       183 |         (void)(((typeof((n)) *)0) == ((uint64_t *)0));  \
>>           |                                   ^~
>>     lib/sbitmap.c:222:20: note: in expansion of macro 'do_div'
>>       222 |         reminder = do_div(shallow_word_depth, sb->depth);
>>           |                    ^~~~~~
> 
> /* The unnecessary pointer compare is there
>  * to check for type safety (n must be 64bit)
>  */
> # define do_div(n,base) ({
> 
> I didn't notice that under specific arch, do_div() will require the fist
> paramater to be 64bit.
> 
> I'll wait a bit longer for people to review the solution before I send a
> new version.

I think it looks good, so please do spin a new version with that fixed
as that's the only thing holding up the inclusion right now.

-- 
Jens Axboe