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, 9 insertions, 0 deletions

diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 672150b6aaf5..fe25a78fff46 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -616,6 +616,7 @@ struct se_session {
         unsigned                sess_tearing_down:1;
         u64                     sess_bin_isid;
         enum target_prot_op     sup_prot_ops;
+        enum target_prot_type   sess_prot_type;
         struct se_node_acl      *se_node_acl;
         struct se_portal_group *se_tpg;
         void                    *fabric_sess_ptr;
diff --git a/include/target/target_core_fabric.h b/include/target/target_core_fabric.h
index 2f4a2505db4c..c93cfdf0d8e5 100644
--- a/include/target/target_core_fabric.h
+++ b/include/target/target_core_fabric.h
@@ -27,6 +27,14 @@ struct target_core_fabric_ops {
          * inquiry response
          */
         int (*tpg_check_demo_mode_login_only)(struct se_portal_group *);
+        /*
+         * Optionally used as a configfs tunable to determine when
+         * target-core should signal the PROTECT=1 feature bit for
+         * backends that don't support T10-PI, so that either fabric
+         * HW offload or target-core emulation performs the associated
+         * WRITE_STRIP and READ_INSERT operations.
+         */
+        int (*tpg_check_prot_fabric_only)(struct se_portal_group *);
         struct se_node_acl *(*tpg_alloc_fabric_acl)(
                                         struct se_portal_group *);
         void (*tpg_release_fabric_acl)(struct se_portal_group *,