target/sbc: Add sbc_dif_read_strip software emulation

Split up __sbc_dif_verify_read() so that VERIFY READ emulation can
perform target-core specific READ_STRIP, seperate from the existing
FILEIO/RAMDISK backend emulation code.

Also add sbc_dif_read_strip() in order to determine number of sectors
using cmd->prot_length, and skip the extra sbc_dif_copy_prot().
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Quinn Tran <quinn.tran@qlogic.com>
Cc: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_sbc.c

@@ -1271,8 +1271,8 @@ sbc_dif_verify_write(struct se_cmd *cmd, sector_t start, unsigned int sectors,
 }
 EXPORT_SYMBOL(sbc_dif_verify_write);
 
-sense_reason_t
-sbc_dif_verify_read(struct se_cmd *cmd, sector_t start, unsigned int sectors,
+static sense_reason_t
+__sbc_dif_verify_read(struct se_cmd *cmd, sector_t start, unsigned int sectors,
 		      unsigned int ei_lba, struct scatterlist *sg, int sg_off)
 {
 	struct se_device *dev = cmd->se_dev;
@@ -1326,8 +1326,31 @@ sbc_dif_verify_read(struct se_cmd *cmd, sector_t start, unsigned int sectors,
 		kunmap_atomic(paddr);
 		kunmap_atomic(daddr);
 	}
-	sbc_dif_copy_prot(cmd, sectors, true, sg, sg_off);
 
 	return 0;
 }
+
+sense_reason_t
+sbc_dif_read_strip(struct se_cmd *cmd)
+{
+	struct se_device *dev = cmd->se_dev;
+	u32 sectors = cmd->prot_length / dev->prot_length;
+
+	return __sbc_dif_verify_read(cmd, cmd->t_task_lba, sectors, 0,
+				     cmd->t_prot_sg, 0);
+}
+
+sense_reason_t
+sbc_dif_verify_read(struct se_cmd *cmd, sector_t start, unsigned int sectors,
+		    unsigned int ei_lba, struct scatterlist *sg, int sg_off)
+{
+	sense_reason_t rc;
+
+	rc = __sbc_dif_verify_read(cmd, start, sectors, ei_lba, sg, sg_off);
+	if (rc)
+		return rc;
+
+	sbc_dif_copy_prot(cmd, sectors, true, sg, sg_off);
+	return 0;
+}
 EXPORT_SYMBOL(sbc_dif_verify_read);

include/target/target_core_backend.h

@@ -78,6 +78,7 @@ sense_reason_t	sbc_dif_verify_write(struct se_cmd *, sector_t, unsigned int,
 				     unsigned int, struct scatterlist *, int);
 sense_reason_t	sbc_dif_verify_read(struct se_cmd *, sector_t, unsigned int,
 				    unsigned int, struct scatterlist *, int);
+sense_reason_t	sbc_dif_read_strip(struct se_cmd *);
 
 void	transport_set_vpd_proto_id(struct t10_vpd *, unsigned char *);
 int	transport_set_vpd_assoc(struct t10_vpd *, unsigned char *);