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Date: Thu, 9 Jan 2014 12:32:26 +0200
From: Sagi Grimberg <sagig@...lanox.com>
To: "Nicholas A. Bellinger" <nab@...erainc.com>,
target-devel <target-devel@...r.kernel.org>
CC: linux-scsi <linux-scsi@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
"Martin K. Petersen" <martin.petersen@...cle.com>,
Christoph Hellwig <hch@....de>, Hannes Reinecke <hare@...e.de>,
Or Gerlitz <ogerlitz@...lanox.com>,
Nicholas Bellinger <nab@...ux-iscsi.org>
Subject: Re: [PATCH 13/14] target/rd: Add DIF protection into rd_execute_rw
On 1/8/2014 10:36 PM, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@...ux-iscsi.org>
>
> This patch adds support for DIF protection into rd_execute_rw() code
> for WRITE/READ I/O using sbc_dif_verify_[write,read]() logic.
>
> It also adds rd_get_prot_table() for locating protection SGLs
> assoicated with the ramdisk backend device.
>
> Cc: Martin K. Petersen <martin.petersen@...cle.com>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Hannes Reinecke <hare@...e.de>
> Cc: Sagi Grimberg <sagig@...lanox.com>
> Cc: Or Gerlitz <ogerlitz@...lanox.com>
> Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
> ---
> drivers/target/target_core_rd.c | 67 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 67 insertions(+)
>
> diff --git a/drivers/target/target_core_rd.c b/drivers/target/target_core_rd.c
> index dd99844..3fd51eb 100644
> --- a/drivers/target/target_core_rd.c
> +++ b/drivers/target/target_core_rd.c
> @@ -363,6 +363,26 @@ static struct rd_dev_sg_table *rd_get_sg_table(struct rd_dev *rd_dev, u32 page)
> return NULL;
> }
>
> +static struct rd_dev_sg_table *rd_get_prot_table(struct rd_dev *rd_dev, u32 page)
> +{
> + struct rd_dev_sg_table *sg_table;
> + u32 i, sg_per_table = (RD_MAX_ALLOCATION_SIZE /
> + sizeof(struct scatterlist));
> +
> + i = page / sg_per_table;
> + if (i < rd_dev->sg_prot_count) {
> + sg_table = &rd_dev->sg_prot_array[i];
> + if ((sg_table->page_start_offset <= page) &&
> + (sg_table->page_end_offset >= page))
> + return sg_table;
> + }
> +
> + pr_err("Unable to locate struct prot rd_dev_sg_table for page: %u\n",
> + page);
> +
> + return NULL;
> +}
> +
> static sense_reason_t
> rd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
> enum dma_data_direction data_direction)
> @@ -377,6 +397,7 @@ rd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
> u32 rd_page;
> u32 src_len;
> u64 tmp;
> + sense_reason_t rc;
>
> if (dev->rd_flags & RDF_NULLIO) {
> target_complete_cmd(cmd, SAM_STAT_GOOD);
> @@ -399,6 +420,29 @@ rd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
> data_direction == DMA_FROM_DEVICE ? "Read" : "Write",
> cmd->t_task_lba, rd_size, rd_page, rd_offset);
>
> + if ((cmd->se_cmd_flags & SCF_PROT) && se_dev->dev_attrib.pi_prot_type &&
> + data_direction == DMA_TO_DEVICE) {
> + sector_t sector = cmd->data_length / se_dev->dev_attrib.block_size;
> + struct rd_dev_sg_table *prot_table;
> + struct scatterlist *prot_sg;
> + u32 prot_offset, prot_page;
> +
> + tmp = cmd->t_task_lba * se_dev->prot_length;
> + prot_offset = do_div(tmp, PAGE_SIZE);
> + prot_page = tmp;
> +
> + prot_table = rd_get_prot_table(dev, prot_page);
> + if (!prot_table)
> + return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
> +
> + prot_sg = &prot_table->sg_table[prot_page - prot_table->page_start_offset];
> +
> + rc = sbc_dif_verify_write(cmd, cmd->t_task_lba, sector, 0,
> + prot_sg, prot_offset);
> + if (rc)
> + return rc;
> + }
> +
> src_len = PAGE_SIZE - rd_offset;
> sg_miter_start(&m, sgl, sgl_nents,
> data_direction == DMA_FROM_DEVICE ?
> @@ -460,6 +504,29 @@ rd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
> }
> sg_miter_stop(&m);
>
> + if ((cmd->se_cmd_flags & SCF_PROT) && se_dev->dev_attrib.pi_prot_type &&
> + data_direction == DMA_FROM_DEVICE) {
> + sector_t sector = cmd->data_length / se_dev->dev_attrib.block_size;
> + struct rd_dev_sg_table *prot_table;
> + struct scatterlist *prot_sg;
> + u32 prot_offset, prot_page;
> +
> + tmp = cmd->t_task_lba * se_dev->prot_length;
> + prot_offset = do_div(tmp, PAGE_SIZE);
> + prot_page = tmp;
> +
> + prot_table = rd_get_prot_table(dev, prot_page);
> + if (!prot_table)
> + return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
> +
> + prot_sg = &prot_table->sg_table[prot_page - prot_table->page_start_offset];
> +
> + rc = sbc_dif_verify_read(cmd, cmd->t_task_lba, sector, 0,
> + prot_sg, prot_offset);
> + if (rc)
> + return rc;
> + }
> +
> target_complete_cmd(cmd, SAM_STAT_GOOD);
> return 0;
> }
I wander how we can skip sbc_dif_verify_xxxx if the transport already
offloaded DIF verify.
I think that the transport should signal the core layer that it is able
to offload DIF (ADD/STRIP/PASS/VERIFY), in which case the core should
turn off the backstore DIF verify emulation to sustain performance. I
assume that if backstore DIF verify is offloaded as well it does not
really matter.
Sagi.
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