linux-kernel - Re: [PATCHv4 02/28] timens: Add timens

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Message-ID: <6e58d0dd-61ae-8566-0f64-badbfe1b20d1@gmail.com>
Date:   Mon, 29 Jul 2019 23:26:37 +0100
From:   Dmitry Safonov <0x7f454c46@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Safonov <dima@...sta.com>
Cc:     linux-kernel@...r.kernel.org, Andrei Vagin <avagin@...nvz.org>,
        Adrian Reber <adrian@...as.de>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jann Horn <jannh@...gle.com>, Jeff Dike <jdike@...toit.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Shuah Khan <shuah@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        containers@...ts.linux-foundation.org, criu@...nvz.org,
        linux-api@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCHv4 02/28] timens: Add timens_offsets

Hi Thomas,

On 6/14/19 2:11 PM, Thomas Gleixner wrote:
> On Wed, 12 Jun 2019, Dmitry Safonov wrote:
> 
>> From: Andrei Vagin <avagin@...nvz.org>
>>
>> Introduce offsets for time namespace. They will contain an adjustment
>> needed to convert clocks to/from host's.
>>
>> Allocate one page for each time namespace that will be premapped into
>> userspace among vvar pages.
>> index 000000000000..7d7cb68ea778
>> --- /dev/null
>> +++ b/include/linux/timens_offsets.h
>> @@ -0,0 +1,8 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +#ifndef _LINUX_TIME_OFFSETS_H
>> +#define _LINUX_TIME_OFFSETS_H
>> +
>> +struct timens_offsets {
>> +};
> 
> That empty struct which is nowhere used looks odd. Can you move that to the
> patch which actually makes use of it?

I've tried to move the structure into patch
[PATCHv4 05/28] timens: Introduce CLOCK_BOOTTIME offset
but that resulted in an ugly patch.

Then I've tried to make it an opaque type here [to keep
allocation/freeing in one commit], and change to a full structure in the
following CLOCK_BOOTTIME patch, but that wasn't any prettier.

So, we've [with Andrei] addressed your critics but this in v5.

Just to let you know, that we haven't silently ignored your review, but
found that it might be prettier to keep the patch as-is..
I'll move it in v6 if it still makes sense in v5.

Thanks much for your time,
          Dmitry