target/sbc: Add sbc_dif_generate software emulation

This patch adds WRITE_INSERT emulation within target-core
using TYPE1 / TYPE3 PI modes in sbc_dif_generate() code.

This is useful in order for existing legacy fabrics that do not
support protection offloads to interact with backend devices that
currently have T10 PI enabled.

v2 changes:
   - Rename to sbc_dif_generate() (Sagi)

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Sagi Grimberg <sagig@mellanox.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>

1 files changed, 44 insertions, 0 deletions

diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c
index f2d73dd4f9a3..cc8c0ba53930 100644
--- a/drivers/target/target_core_sbc.c
+++ b/drivers/target/target_core_sbc.c
@@ -1096,6 +1096,50 @@ err:
 }
 EXPORT_SYMBOL(sbc_execute_unmap);
 
+void
+sbc_dif_generate(struct se_cmd *cmd)
+{
+        struct se_device *dev = cmd->se_dev;
+        struct se_dif_v1_tuple *sdt;
+        struct scatterlist *dsg, *psg = cmd->t_prot_sg;
+        sector_t sector = cmd->t_task_lba;
+        void *daddr, *paddr;
+        int i, j, offset = 0;
+
+        for_each_sg(cmd->t_data_sg, dsg, cmd->t_data_nents, i) {
+                daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
+                paddr = kmap_atomic(sg_page(psg)) + psg->offset;
+
+                for (j = 0; j < dsg->length; j += dev->dev_attrib.block_size) {
+
+                        if (offset >= psg->length) {
+                                kunmap_atomic(paddr);
+                                psg = sg_next(psg);
+                                paddr = kmap_atomic(sg_page(psg)) + psg->offset;
+                                offset = 0;
+                        }
+
+                        sdt = paddr + offset;
+                        sdt->guard_tag = cpu_to_be16(crc_t10dif(daddr + j,
+                                                dev->dev_attrib.block_size));
+                        if (dev->dev_attrib.pi_prot_type == TARGET_DIF_TYPE1_PROT)
+                                sdt->ref_tag = cpu_to_be32(sector & 0xffffffff);
+                        sdt->app_tag = 0;
+
+                        pr_debug("DIF WRITE INSERT sector: %llu guard_tag: 0x%04x"
+                                 " app_tag: 0x%04x ref_tag: %u\n",
+                                 (unsigned long long)sector, sdt->guard_tag,
+                                 sdt->app_tag, be32_to_cpu(sdt->ref_tag));
+
+                        sector++;
+                        offset += sizeof(struct se_dif_v1_tuple);
+                }
+
+                kunmap_atomic(paddr);
+                kunmap_atomic(daddr);
+        }
+}
+
 static sense_reason_t
 sbc_dif_v1_verify(struct se_device *dev, struct se_dif_v1_tuple *sdt,
                   const void *p, sector_t sector, unsigned int ei_lba)