target: Add protected fabric + unprotected device support

This patch adds a new target_core_fabric_ops callback for allowing fabric
drivers to expose a TPG attribute for signaling when a T10-PI protected
fabric wants to function with an un-protected device without T10-PI.

This specifically is to allow LIO to perform WRITE_STRIP + READ_INSERT
operations when functioning with non T10-PI enabled devices, seperate
from any available hw offloads the fabric supports.

This is done using a new se_sess->sess_prot_type that is set at fabric
session creation time based upon the TPG attribute.  It currently cannot
be changed for individual sessions after initial creation.

Also, update existing target_core_sbc.c code to honor sess_prot_type when
setting up cmd->prot_op + cmd->prot_type assignments.

(Add unlikely and !! boolean conversion in sbc_check_prot - Sagi)

Cc: Martin Petersen <martin.petersen@oracle.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Doug Gilbert <dgilbert@interlog.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

2 files changed, 41 insertions, 11 deletions

diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c
index 95a7a7444965..9efd1fd985ee 100644
--- a/drivers/target/target_core_sbc.c
+++ b/drivers/target/target_core_sbc.c
@@ -581,12 +581,13 @@ sbc_compare_and_write(struct se_cmd *cmd)
 }
 
 static int
-sbc_set_prot_op_checks(u8 protect, enum target_prot_type prot_type,
+sbc_set_prot_op_checks(u8 protect, bool fabric_prot, enum target_prot_type prot_type,
                        bool is_write, struct se_cmd *cmd)
 {
         if (is_write) {
-                cmd->prot_op = protect ? TARGET_PROT_DOUT_PASS :
-                                         TARGET_PROT_DOUT_INSERT;
+                cmd->prot_op = fabric_prot ? TARGET_PROT_DOUT_STRIP :
+                               protect ? TARGET_PROT_DOUT_PASS :
+                               TARGET_PROT_DOUT_INSERT;
                 switch (protect) {
                 case 0x0:
                 case 0x3:
@@ -610,8 +611,9 @@ sbc_set_prot_op_checks(u8 protect, enum target_prot_type prot_type,
                         return -EINVAL;
                 }
         } else {
-                cmd->prot_op = protect ? TARGET_PROT_DIN_PASS :
-                                         TARGET_PROT_DIN_STRIP;
+                cmd->prot_op = fabric_prot ? TARGET_PROT_DIN_INSERT :
+                               protect ? TARGET_PROT_DIN_PASS :
+                               TARGET_PROT_DIN_STRIP;
                 switch (protect) {
                 case 0x0:
                 case 0x1:
@@ -644,11 +646,15 @@ sbc_check_prot(struct se_device *dev, struct se_cmd *cmd, unsigned char *cdb,
                u32 sectors, bool is_write)
 {
         u8 protect = cdb[1] >> 5;
+        int sp_ops = cmd->se_sess->sup_prot_ops;
+        int pi_prot_type = dev->dev_attrib.pi_prot_type;
+        bool fabric_prot = false;
 
         if (!cmd->t_prot_sg || !cmd->t_prot_nents) {
-                if (protect && !dev->dev_attrib.pi_prot_type) {
-                        pr_err("CDB contains protect bit, but device does not"
-                               " advertise PROTECT=1 feature bit\n");
+                if (unlikely(protect &&
+                    !dev->dev_attrib.pi_prot_type && !cmd->se_sess->sess_prot_type)) {
+                        pr_err("CDB contains protect bit, but device + fabric does"
+                               " not advertise PROTECT=1 feature bit\n");
                         return TCM_INVALID_CDB_FIELD;
                 }
                 if (cmd->prot_pto)
@@ -669,15 +675,28 @@ sbc_check_prot(struct se_device *dev, struct se_cmd *cmd, unsigned char *cdb,
                 cmd->reftag_seed = cmd->t_task_lba;
                 break;
         case TARGET_DIF_TYPE0_PROT:
+                /*
+                 * See if the fabric supports T10-PI, and the session has been
+                 * configured to allow export PROTECT=1 feature bit with backend
+                 * devices that don't support T10-PI.
+                 */
+                fabric_prot = is_write ?
+                              !!(sp_ops & (TARGET_PROT_DOUT_PASS | TARGET_PROT_DOUT_STRIP)) :
+                              !!(sp_ops & (TARGET_PROT_DIN_PASS | TARGET_PROT_DIN_INSERT));
+
+                if (fabric_prot && cmd->se_sess->sess_prot_type) {
+                        pi_prot_type = cmd->se_sess->sess_prot_type;
+                        break;
+                }
+                /* Fallthrough */
         default:
                 return TCM_NO_SENSE;
         }
 
-        if (sbc_set_prot_op_checks(protect, dev->dev_attrib.pi_prot_type,
-                                   is_write, cmd))
+        if (sbc_set_prot_op_checks(protect, fabric_prot, pi_prot_type, is_write, cmd))
                 return TCM_INVALID_CDB_FIELD;
 
-        cmd->prot_type = dev->dev_attrib.pi_prot_type;
+        cmd->prot_type = pi_prot_type;
         cmd->prot_length = dev->prot_length * sectors;
 
         /**
@@ -1231,6 +1250,9 @@ sbc_dif_copy_prot(struct se_cmd *cmd, unsigned int sectors, bool read,
         unsigned int i, len, left;
         unsigned int offset = sg_off;
 
+        if (!sg)
+                return;
+
         left = sectors * dev->prot_length;
 
         for_each_sg(cmd->t_prot_sg, psg, cmd->t_prot_nents, i) {
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 4a00ed5c1880..aef989e165ed 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -322,11 +322,19 @@ void __transport_register_session(
         struct se_session *se_sess,
         void *fabric_sess_ptr)
 {
+        struct target_core_fabric_ops *tfo = se_tpg->se_tpg_tfo;
         unsigned char buf[PR_REG_ISID_LEN];
 
         se_sess->se_tpg = se_tpg;
         se_sess->fabric_sess_ptr = fabric_sess_ptr;
         /*
+         * Determine if fabric allows for T10-PI feature bits to be exposed
+         * to initiators for device backends with !dev->dev_attrib.pi_prot_type
+         */
+        if (tfo->tpg_check_prot_fabric_only)
+                se_sess->sess_prot_type = tfo->tpg_check_prot_fabric_only(se_tpg);
+
+        /*
          * Used by struct se_node_acl's under ConfigFS to locate active se_session-t
          *
          * Only set for struct se_session's that will actually be moving I/O.