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

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Message-ID: <87a5wizqto.fsf@metaspace.dk>
Date:   Thu, 29 Jun 2023 09:09:07 +0200
From:   "Andreas Hindborg (Samsung)" <nmi@...aspace.dk>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Damien Le Moal <dlemoal@...nel.org>,
        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>,
        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


Ming Lei <ming.lei@...hat.com> writes:

> 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.
>
>> 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.

I can change it back to `#define` again, no problem. I only changed it
to `enum` on request from Ming [1]

Best regards,
Andreas

[1] https://lore.kernel.org/all/ZAHeWieKXtgYUbvz@ovpn-8-18.pek2.redhat.com/