[RFC] scsi: support packing multi-segment in UNMAP command

As SPEC describes that it can support unmapping one or more LBA range
in single UNMAP command, however, previously we only pack one LBA
range in UNMAP command by default no matter device gives the block
limits that says it can support in-batch UNMAP.

This patch tries to set max_discard_segments config according to block
limits of device, and supports in-batch UNMAP.

Signed-off-by: Chao Yu <chao@kernel.org>
---
 drivers/scsi/sd.c | 30 +++++++++++++++++++-----------
 drivers/scsi/sd.h |  1 +
 2 files changed, 20 insertions(+), 11 deletions(-)

Ping,

Any comments?

Thanks,

On 2022/5/21 19:32, Chao Yu wrote:
> As SPEC describes that it can support unmapping one or more LBA range
> in single UNMAP command, however, previously we only pack one LBA
> range in UNMAP command by default no matter device gives the block
> limits that says it can support in-batch UNMAP.
> 
> This patch tries to set max_discard_segments config according to block
> limits of device, and supports in-batch UNMAP.
> 
> Signed-off-by: Chao Yu <chao@kernel.org>
> ---
>   drivers/scsi/sd.c | 30 +++++++++++++++++++-----------
>   drivers/scsi/sd.h |  1 +
>   2 files changed, 20 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index dc6e55761fd1..be070457c78d 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -790,6 +790,7 @@ static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
>   	q->limits.discard_granularity =
>   		max(sdkp->physical_block_size,
>   		    sdkp->unmap_granularity * logical_block_size);
> +	blk_queue_max_discard_segments(q, sdkp->max_block_desc_count);
>   	sdkp->provisioning_mode = mode;
>   
>   	switch (mode) {
> @@ -837,10 +838,10 @@ static blk_status_t sd_setup_unmap_cmnd(struct scsi_cmnd *cmd)
>   {
>   	struct scsi_device *sdp = cmd->device;
>   	struct request *rq = scsi_cmd_to_rq(cmd);
> +	struct bio *bio;
>   	struct scsi_disk *sdkp = scsi_disk(rq->q->disk);
> -	u64 lba = sectors_to_logical(sdp, blk_rq_pos(rq));
> -	u32 nr_blocks = sectors_to_logical(sdp, blk_rq_sectors(rq));
> -	unsigned int data_len = 24;
> +	unsigned short segments = blk_rq_nr_discard_segments(rq);
> +	unsigned int data_len = 8 + 16 * segments, i = 0;
>   	char *buf;
>   
>   	rq->special_vec.bv_page = mempool_alloc(sd_page_pool, GFP_ATOMIC);
> @@ -853,13 +854,20 @@ static blk_status_t sd_setup_unmap_cmnd(struct scsi_cmnd *cmd)
>   
>   	cmd->cmd_len = 10;
>   	cmd->cmnd[0] = UNMAP;
> -	cmd->cmnd[8] = 24;
> +	cmd->cmnd[8] = data_len;
>   
>   	buf = bvec_virt(&rq->special_vec);
> -	put_unaligned_be16(6 + 16, &buf[0]);
> -	put_unaligned_be16(16, &buf[2]);
> -	put_unaligned_be64(lba, &buf[8]);
> -	put_unaligned_be32(nr_blocks, &buf[16]);
> +	put_unaligned_be16(6 + 16 * segments, &buf[0]);
> +	put_unaligned_be16(16 * segments, &buf[2]);
> +
> +	__rq_for_each_bio(bio, rq) {
> +		u64 lba = sectors_to_logical(sdp, bio->bi_iter.bi_sector);
> +		u32 nr_blocks = sectors_to_logical(sdp, bio_sectors(bio));
> +
> +		put_unaligned_be64(lba, &buf[8 + 16 * i]);
> +		put_unaligned_be32(nr_blocks, &buf[8 + 16 * i + 8]);
> +		i++;
> +	}
>   
>   	cmd->allowed = sdkp->max_retries;
>   	cmd->transfersize = data_len;
> @@ -2859,7 +2867,7 @@ static void sd_read_block_limits(struct scsi_disk *sdkp)
>   	sdkp->opt_xfer_blocks = get_unaligned_be32(&buffer[12]);
>   
>   	if (buffer[3] == 0x3c) {
> -		unsigned int lba_count, desc_count;
> +		unsigned int lba_count;
>   
>   		sdkp->max_ws_blocks = (u32)get_unaligned_be64(&buffer[36]);
>   
> @@ -2867,9 +2875,9 @@ static void sd_read_block_limits(struct scsi_disk *sdkp)
>   			goto out;
>   
>   		lba_count = get_unaligned_be32(&buffer[20]);
> -		desc_count = get_unaligned_be32(&buffer[24]);
> +		sdkp->max_block_desc_count = get_unaligned_be32(&buffer[24]);
>   
> -		if (lba_count && desc_count)
> +		if (lba_count && sdkp->max_block_desc_count)
>   			sdkp->max_unmap_blocks = lba_count;
>   
>   		sdkp->unmap_granularity = get_unaligned_be32(&buffer[28]);
> diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
> index 0a33a4b68ffb..e396bcaf76ca 100644
> --- a/drivers/scsi/sd.h
> +++ b/drivers/scsi/sd.h
> @@ -99,6 +99,7 @@ struct scsi_disk {
>   	u32		opt_xfer_blocks;
>   	u32		max_ws_blocks;
>   	u32		max_unmap_blocks;
> +	u32		max_block_desc_count;
>   	u32		unmap_granularity;
>   	u32		unmap_alignment;
>   	u32		index;

Chao,

> Any comments?

It's on my list of things to look at for 5.20.

On 2022/5/25 9:42, Martin K. Petersen wrote:
> 
> Chao,
> 
>> Any comments?
> 
> It's on my list of things to look at for 5.20.

Martin, thanks!

Thanks,

>