This patch enhances the NVMe over Fibre Channel (NVMe-FC) driver to 
handle requests with integrity metadata (DIF).

- Added the inclusion of `<linux/blk-integrity.h>` to enable integrity operations.
- Implemented support for mapping integrity metadata using `blk_rq_map_integrity_sg`.
- Ensures proper handling of requests with integrity metadata, including error cases where mapping fails.

This update improves the reliability of data integrity checks in environments utilizing DIF.

Signed-off-by: Atharva Tiwari <evepolonium@gmail.com>
---
 drivers/nvme/host/fc.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index b81af7919e94..d0343133413f 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -17,6 +17,7 @@
 #include "fc.h"
 #include <scsi/scsi_transport_fc.h>
 #include <linux/blk-mq-pci.h>
+#include <linux/blk-integrity.h>
 
 /* *************************** Data Structures/Defines ****************** */
 
@@ -2620,10 +2621,16 @@ nvme_fc_map_data(struct nvme_fc_ctrl *ctrl, struct request *rq,
 		freq->sg_cnt = 0;
 		return -EFAULT;
 	}
-
-	/*
-	 * TODO: blk_integrity_rq(rq)  for DIF
-	 */
+	/* Handle requests with integrity metadata (DIF) */
+	if (blk_integrity_rq(rq)) {
+		ret = blk_rq_map_integrity_sg(rq, freq->sg_table.sgl);
+		if (ret < 0) {
+			sg_free_table_chained(&freq->sg_table, NVME_INLINE_SG_CNT);
+			freq->sg_cnt = 0;
+			return -EFAULT;
+		}
+		freq->sg_cnt += ret;
+	}
 	return 0;
 }
 
-- 
2.39.5

On Thu, Dec 26, 2024 at 02:44:15PM +0530, Atharva Tiwari wrote:
> This patch enhances the NVMe over Fibre Channel (NVMe-FC) driver to 
> handle requests with integrity metadata (DIF).
> 
> - Added the inclusion of `<linux/blk-integrity.h>` to enable integrity operations.
> - Implemented support for mapping integrity metadata using `blk_rq_map_integrity_sg`.
> - Ensures proper handling of requests with integrity metadata, including error cases where mapping fails.

This isn't really how we write commit logs.  The mechanics are
visible in the patch.  Also please wrap commit log lines after 73
characters.

> +	/* Handle requests with integrity metadata (DIF) */
> +	if (blk_integrity_rq(rq)) {
> +		ret = blk_rq_map_integrity_sg(rq, freq->sg_table.sgl);
> +		if (ret < 0) {
> +			sg_free_table_chained(&freq->sg_table, NVME_INLINE_SG_CNT);
> +			freq->sg_cnt = 0;
> +			return -EFAULT;
> +		}
> +		freq->sg_cnt += ret;
> +	}

Who is going to look at the integrity sglist?  Who is setting a
max_integrity_segments value for nvme-fc?

How was this tested?