Re: [PATCH 1/2] block: change REQ_OP_ZONE_RESET and REQ_OP_ZONE_RESET_ALL to be odd numbers

[Damien Le Moal <Damien.LeMoal@wdc.com>]

On 2020/07/13 21:35, Coly Li wrote:
> Currently REQ_OP_ZONE_RESET and REQ_OP_ZONE_RESET_ALL are defined as
> even numbers 6 and 8, such zone reset bios are treated as READ bios by
> bio_data_dir(), which is obviously misleading.
> 
> The macro bio_data_dir() is defined in include/linux/bio.h as,
>  55 #define bio_data_dir(bio) \
>  56         (op_is_write(bio_op(bio)) ? WRITE : READ)
> 
> And op_is_write() is defined in include/linux/blk_types.h as,
> 397 static inline bool op_is_write(unsigned int op)
> 398 {
> 399         return (op & 1);
> 400 }
> 
> The convention of op_is_write() is when there is data transfer then the
> op code should be odd number, and treat as a write op. bio_data_dir()
> treats all bio direction as READ if op_is_write() reports false, and
> WRITE if op_is_write() reports true.
> 
> Because REQ_OP_ZONE_RESET and REQ_OP_ZONE_RESET_ALL are even numbers,
> although they don't transfer data but reporting them as READ bio by
> bio_data_dir() is misleading and might be wrong. Because these two
> commands will reset the writer pointers of the resetting zones, and all
> content after the reset write pointer will be invalid and unaccessible,
> obviously they are not READ bios in any means.
> 
> This patch changes REQ_OP_ZONE_RESET from 6 to 15, and changes
> REQ_OP_ZONE_RESET_ALL from 8 to 17. Now bios with these two op code
> can be treated as WRITE by bio_data_dir(). Although they don't transfer
> data, now we keep them consistent with REQ_OP_DISCARD and
> REQ_OP_WRITE_ZEROES with the ituition that they change on-media content

s/ituition/assumption

> and should be WRITE request.
> 
> Signed-off-by: Coly Li <colyli@suse.de>
> Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Hannes Reinecke <hare@suse.de>
> Cc: Jens Axboe <axboe@fb.com>
> Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> Cc: Keith Busch <kbusch@kernel.org>
> Cc: Shaun Tancheff <shaun.tancheff@seagate.com>
> ---
>  include/linux/blk_types.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index ccb895f911b1..447b46a0accf 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -300,12 +300,8 @@ enum req_opf {
>  	REQ_OP_DISCARD		= 3,
>  	/* securely erase sectors */
>  	REQ_OP_SECURE_ERASE	= 5,
> -	/* reset a zone write pointer */
> -	REQ_OP_ZONE_RESET	= 6,
>  	/* write the same sector many times */
>  	REQ_OP_WRITE_SAME	= 7,
> -	/* reset all the zone present on the device */
> -	REQ_OP_ZONE_RESET_ALL	= 8,
>  	/* write the zero filled sector many times */
>  	REQ_OP_WRITE_ZEROES	= 9,
>  	/* Open a zone */
> @@ -316,6 +312,10 @@ enum req_opf {
>  	REQ_OP_ZONE_FINISH	= 12,
>  	/* write data at the current zone write pointer */
>  	REQ_OP_ZONE_APPEND	= 13,
> +	/* reset a zone write pointer */
> +	REQ_OP_ZONE_RESET	= 15,
> +	/* reset all the zone present on the device */
> +	REQ_OP_ZONE_RESET_ALL	= 17,
>  
>  	/* SCSI passthrough using struct scsi_request */
>  	REQ_OP_SCSI_IN		= 32,
> 

Looks good to me. Zone reset is very similar to a discard, albeit stronger (zone
reset is not a hint). So defining these ops as having the same data dir makes sense.

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>

-- 
Damien Le Moal
Western Digital Research