Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v3 13/23] mm/mmap: Make vm_special_mapping::mremap return
 void
To:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        linux-kernel@vger.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@gmail.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Guo Ren <guoren@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Ingo Molnar <mingo@redhat.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Russell King <linux@armlinux.org.uk>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Will Deacon <will@kernel.org>, x86@kernel.org
References: <20210611180242.711399-1-dima@arista.com>
 <20210611180242.711399-14-dima@arista.com>
 <901f4541-ee96-5d6b-5453-559731d65e82@csgroup.eu>
From:   Dmitry Safonov <dima@arista.com>
Message-ID: <e8b98439-6e53-b3ac-af78-bb814292349e@arista.com>
Date:   Mon, 21 Jun 2021 22:12:44 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.11.0
MIME-Version: 1.0
In-Reply-To: <901f4541-ee96-5d6b-5453-559731d65e82@csgroup.eu>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 6/17/21 8:20 AM, Christophe Leroy wrote:
> 
> 
> Le 11/06/2021 à 20:02, Dmitry Safonov a écrit :
>> Previously .mremap() callback had to return (int) to provide
>> a way to restrict resizing of a special mapping. Now it's
>> restricted by providing .may_split = special_mapping_split.
>>
>> Removing (int) return simplifies further changes to
>> special_mapping_mremap() as it won't need save ret code from the
>> callback. Also, it removes needless `return 0` from callbacks.
>>
>> Signed-off-by: Dmitry Safonov <dima@arista.com>
>> ---
>>   arch/arm/kernel/process.c | 3 +--
>>   arch/arm64/kernel/vdso.c  | 4 +---
>>   arch/mips/vdso/genvdso.c  | 3 +--
>>   arch/x86/entry/vdso/vma.c | 4 +---
>>   include/linux/mm_types.h  | 4 ++--
>>   mm/mmap.c                 | 2 +-
>>   6 files changed, 7 insertions(+), 13 deletions(-)
>>
> 
> Build failure:
> 
>   CC      arch/powerpc/kernel/vdso.o
> arch/powerpc/kernel/vdso.c:93:19: error: initialization of 'void
> (*)(const struct vm_special_mapping *, struct vm_area_struct *)' from
> incompatible pointer type 'int (*)(const struct vm_special_mapping *,
> struct vm_area_struct *)' [-Werror=incompatible-pointer-types]
>    93 |         .mremap = vdso32_mremap,
>       |                   ^~~~~~~~~~~~~
> arch/powerpc/kernel/vdso.c:93:19: note: (near initialization for
> 'vdso32_spec.mremap')
> arch/powerpc/kernel/vdso.c:98:19: error: initialization of 'void
> (*)(const struct vm_special_mapping *, struct vm_area_struct *)' from
> incompatible pointer type 'int (*)(const struct vm_special_mapping *,
> struct vm_area_struct *)' [-Werror=incompatible-pointer-types]
>    98 |         .mremap = vdso64_mremap,
>       |                   ^~~~~~~~~~~~~
> arch/powerpc/kernel/vdso.c:98:19: note: (near initialization for
> 'vdso64_spec.mremap')
> cc1: all warnings being treated as errors
> make[3]: *** [arch/powerpc/kernel/vdso.o] Error 1
> make[2]: *** [arch/powerpc/kernel] Error 2
> make[1]: *** [arch/powerpc] Error 2
> make: *** [__sub-make] Error 2
> 

Thanks for reporting, Christophe, I'll fix that in v4.

Thanks,
          Dmitry