linux-kernel - Re: [PATCH v6 6/6] loop: Add support for REQ

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Message-ID: <20200212170156.GM6874@magnolia>
Date:   Wed, 12 Feb 2020 09:01:56 -0800
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     martin.petersen@...cle.com, bob.liu@...cle.com, axboe@...nel.dk,
        agk@...hat.com, snitzer@...hat.com, dm-devel@...hat.com,
        song@...nel.org, tytso@....edu, adilger.kernel@...ger.ca,
        Chaitanya.Kulkarni@....com, ming.lei@...hat.com, osandov@...com,
        jthumshirn@...e.de, minwoo.im.dev@...il.com, damien.lemoal@....com,
        andrea.parri@...rulasolutions.com, hare@...e.com, tj@...nel.org,
        ajay.joshi@....com, sagi@...mberg.me, dsterba@...e.com,
        bvanassche@....org, dhowells@...hat.com, asml.silence@...il.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 6/6] loop: Add support for REQ_ALLOCATE

On Mon, Feb 10, 2020 at 12:34:04PM +0300, Kirill Tkhai wrote:
> Support for new modifier of REQ_OP_WRITE_ZEROES command.
> This results in allocation extents in backing file instead
> of actual blocks zeroing.
> 
> Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
> Reviewed-by: Bob Liu <bob.liu@...cle.com>
> ---
>  drivers/block/loop.c |   15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 739b372a5112..bfe76d9adf09 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -581,6 +581,15 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
>  	return 0;
>  }
>  
> +static unsigned int write_zeroes_to_fallocate_mode(unsigned int flags)
> +{
> +	if (flags & REQ_ALLOCATE)
> +		return 0;
> +	if (flags & REQ_NOUNMAP)
> +		return FALLOC_FL_ZERO_RANGE;
> +	return FALLOC_FL_PUNCH_HOLE;
> +}
> +
>  static int do_req_filebacked(struct loop_device *lo, struct request *rq)
>  {
>  	struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
> @@ -604,9 +613,7 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq)
>  		 * write zeroes the range.  Otherwise, punch them out.
>  		 */

Please update this comment to reflect the new REQ_ALLOCATE mode, and
move it to where you define write_zeroes_to_fallocate_mode().

With that fixed,

Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>

--D

>  		return lo_fallocate(lo, rq, pos,
> -			(rq->cmd_flags & REQ_NOUNMAP) ?
> -				FALLOC_FL_ZERO_RANGE :
> -				FALLOC_FL_PUNCH_HOLE);
> +			write_zeroes_to_fallocate_mode(rq->cmd_flags));
>  	case REQ_OP_DISCARD:
>  		return lo_fallocate(lo, rq, pos, FALLOC_FL_PUNCH_HOLE);
>  	case REQ_OP_WRITE:
> @@ -877,6 +884,7 @@ static void loop_config_discard(struct loop_device *lo)
>  		q->limits.discard_alignment = 0;
>  		blk_queue_max_discard_sectors(q, 0);
>  		blk_queue_max_write_zeroes_sectors(q, 0);
> +		blk_queue_max_allocate_sectors(q, 0);
>  		blk_queue_flag_clear(QUEUE_FLAG_DISCARD, q);
>  		return;
>  	}
> @@ -886,6 +894,7 @@ static void loop_config_discard(struct loop_device *lo)
>  
>  	blk_queue_max_discard_sectors(q, UINT_MAX >> 9);
>  	blk_queue_max_write_zeroes_sectors(q, UINT_MAX >> 9);
> +	blk_queue_max_allocate_sectors(q, UINT_MAX >> 9);
>  	blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
>  }
>  
> 
>