linux-kernel - Re: [PATCH v4 1/4] ublk: change ublk IO command defines to enum

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Message-ID: <0f8160eb-f504-5069-5c78-783bce59b214@kernel.org>
Date:   Thu, 29 Jun 2023 10:14:28 +0900
From:   Damien Le Moal <dlemoal@...nel.org>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Andreas Hindborg <nmi@...aspace.dk>,
        Hans Holmberg <Hans.Holmberg@....com>,
        Aravind Ramesh <Aravind.Ramesh@....com>,
        Jens Axboe <axboe@...nel.dk>,
        "open list:BLOCK LAYER" <linux-block@...r.kernel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Matias Bjorling <Matias.Bjorling@....com>,
        Andreas Hindborg <a.hindborg@...sung.com>,
        open list <linux-kernel@...r.kernel.org>, gost.dev@...sung.com,
        Minwoo Im <minwoo.im.dev@...il.com>
Subject: Re: [PATCH v4 1/4] ublk: change ublk IO command defines to enum

On 6/29/23 09:38, Ming Lei wrote:
> On Thu, Jun 29, 2023 at 07:47:47AM +0900, Damien Le Moal wrote:
>> On 6/29/23 04:06, Andreas Hindborg wrote:
>>> From: Andreas Hindborg <a.hindborg@...sung.com>
>>>
>>> This change is in preparation for zoned storage support.
>>>
>>> Signed-off-by: Andreas Hindborg <a.hindborg@...sung.com>
>>> ---
>>>  include/uapi/linux/ublk_cmd.h | 23 +++++++++++++++++------
>>>  1 file changed, 17 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
>>> index 4b8558db90e1..471b3b983045 100644
>>> --- a/include/uapi/linux/ublk_cmd.h
>>> +++ b/include/uapi/linux/ublk_cmd.h
>>> @@ -229,12 +229,23 @@ struct ublksrv_ctrl_dev_info {
>>>  	__u64   reserved2;
>>>  };
>>>  
>>> -#define		UBLK_IO_OP_READ		0
>>> -#define		UBLK_IO_OP_WRITE		1
>>> -#define		UBLK_IO_OP_FLUSH		2
>>> -#define		UBLK_IO_OP_DISCARD	3
>>> -#define		UBLK_IO_OP_WRITE_SAME	4
>>> -#define		UBLK_IO_OP_WRITE_ZEROES	5
>>> +enum ublk_op {
>>> +	UBLK_IO_OP_READ = 0,
>>> +	UBLK_IO_OP_WRITE = 1,
>>> +	UBLK_IO_OP_FLUSH = 2,
>>> +	UBLK_IO_OP_DISCARD = 3,
>>> +	UBLK_IO_OP_WRITE_SAME = 4,
>>> +	UBLK_IO_OP_WRITE_ZEROES = 5,
>>> +	UBLK_IO_OP_ZONE_OPEN = 10,
>>> +	UBLK_IO_OP_ZONE_CLOSE = 11,
>>> +	UBLK_IO_OP_ZONE_FINISH = 12,
>>> +	UBLK_IO_OP_ZONE_APPEND = 13,
>>> +	UBLK_IO_OP_ZONE_RESET = 15,
>>> +	__UBLK_IO_OP_DRV_IN_START = 32,
>>> +	__UBLK_IO_OP_DRV_IN_END = 96,
>>> +	__UBLK_IO_OP_DRV_OUT_START = __UBLK_IO_OP_DRV_IN_END,
>>> +	__UBLK_IO_OP_DRV_OUT_END = 160,
>>> +};
>>
>> This patch does not do what the title says. You are also introducing the zone
>> operations, and the very obscure __UBLK_IO_OP_DRV_XXX operations without an
>> explanation. Also, why the "__" prefix for these ? I do not see the point...
> 
> It should be to reserve space for ublk passthrough OP.

A comment about that would be nice.

> 
>> Given that this is a uapi, a comment to explain the less obvious commands would
>> be nice.
>>
>> So I think the change to an enum for the existing ops can be done either in
>> patch 2 or as a separate patch and the introduction of the zone operations done
>> in patch 3 or as a separate patch.
> 
> Also it might break userspace by changing to enum from macro for existed
> definition, cause userspace may check something by '#ifdef UBLK_IO_OP_*',
> so probably it is better to keep these OPs as enum, or at least keep
> existed definition as macro.

Then let's keep defining things with #define instead of an enum.

> 
> Thanks,
> Ming
> 

-- 
Damien Le Moal
Western Digital Research