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

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Message-ID: <7d2b0108-4d16-97fb-5de9-7438414d9ca4@huaweicloud.com>
Date: Thu, 7 Aug 2025 09:30:49 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: kernel test robot <lkp@...el.com>, Yu Kuai <yukuai1@...weicloud.com>,
 axboe@...nel.dk, 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

Hi,

在 2025/08/06 17:41, kernel test robot 写道:
> 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.

Thanks,
Kuai