iscsi/iser-target: Support multi-sequence sendtargets text response

In case sendtargets response is larger than initiator MRDSL, we
send a partial sendtargets response (setting F=0, C=1, TTT!=0xffffffff),
accept a consecutive empty text message and send the rest of the payload.
In case we are done, we set F=1, C=0, TTT=0xffffffff.
We do that by storing the sendtargets response bytes done under
the session.

This patch also makes iscsit_find_cmd_from_itt public for isert.

(Re-add cmd->maxcmdsn_inc and clear in iscsit_build_text_rsp - nab)

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

3 files changed, 66 insertions, 23 deletions

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 75c29b687f35..f533a0dfa4de 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -1994,6 +1994,7 @@ iscsit_setup_text_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
         cmd->cmd_sn             = be32_to_cpu(hdr->cmdsn);
         cmd->exp_stat_sn        = be32_to_cpu(hdr->exp_statsn);
         cmd->data_direction     = DMA_NONE;
+        cmd->text_in_ptr        = NULL;
 
         return 0;
 }
@@ -2007,9 +2008,13 @@ iscsit_process_text_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
         int cmdsn_ret;
 
         if (!text_in) {
-                pr_err("Unable to locate text_in buffer for sendtargets"
-                       " discovery\n");
-                goto reject;
+                cmd->targ_xfer_tag = be32_to_cpu(hdr->ttt);
+                if (cmd->targ_xfer_tag == 0xFFFFFFFF) {
+                        pr_err("Unable to locate text_in buffer for sendtargets"
+                               " discovery\n");
+                        goto reject;
+                }
+                goto empty_sendtargets;
         }
         if (strncmp("SendTargets", text_in, 11) != 0) {
                 pr_err("Received Text Data that is not"
@@ -2036,6 +2041,7 @@ iscsit_process_text_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
         list_add_tail(&cmd->i_conn_node, &conn->conn_cmd_list);
         spin_unlock_bh(&conn->cmd_lock);
 
+empty_sendtargets:
         iscsit_ack_from_expstatsn(conn, be32_to_cpu(hdr->exp_statsn));
 
         if (!(hdr->opcode & ISCSI_OP_IMMEDIATE)) {
@@ -3385,7 +3391,8 @@ static bool iscsit_check_inaddr_any(struct iscsi_np *np)
 
 static int
 iscsit_build_sendtargets_response(struct iscsi_cmd *cmd,
-                                  enum iscsit_transport_type network_transport)
+                                  enum iscsit_transport_type network_transport,
+                                  int skip_bytes, bool *completed)
 {
         char *payload = NULL;
         struct iscsi_conn *conn = cmd->conn;
@@ -3476,9 +3483,16 @@ iscsit_build_sendtargets_response(struct iscsi_cmd *cmd,
                                                 end_of_buf = 1;
                                                 goto eob;
                                         }
-                                        memcpy(payload + payload_len, buf, len);
-                                        payload_len += len;
-                                        target_name_printed = 1;
+
+                                        if (skip_bytes && len <= skip_bytes) {
+                                                skip_bytes -= len;
+                                        } else {
+                                                memcpy(payload + payload_len, buf, len);
+                                                payload_len += len;
+                                                target_name_printed = 1;
+                                                if (len > skip_bytes)
+                                                        skip_bytes = 0;
+                                        }
                                 }
 
                                 len = sprintf(buf, "TargetAddress="
@@ -3494,15 +3508,24 @@ iscsit_build_sendtargets_response(struct iscsi_cmd *cmd,
                                         end_of_buf = 1;
                                         goto eob;
                                 }
-                                memcpy(payload + payload_len, buf, len);
-                                payload_len += len;
+
+                                if (skip_bytes && len <= skip_bytes) {
+                                        skip_bytes -= len;
+                                } else {
+                                        memcpy(payload + payload_len, buf, len);
+                                        payload_len += len;
+                                        if (len > skip_bytes)
+                                                skip_bytes = 0;
+                                }
                         }
                         spin_unlock(&tpg->tpg_np_lock);
                 }
                 spin_unlock(&tiqn->tiqn_tpg_lock);
 eob:
-                if (end_of_buf)
+                if (end_of_buf) {
+                        *completed = false;
                         break;
+                }
 
                 if (cmd->cmd_flags & IFC_SENDTARGETS_SINGLE)
                         break;
@@ -3520,13 +3543,23 @@ iscsit_build_text_rsp(struct iscsi_cmd *cmd, struct iscsi_conn *conn,
                       enum iscsit_transport_type network_transport)
 {
         int text_length, padding;
+        bool completed = true;
 
-        text_length = iscsit_build_sendtargets_response(cmd, network_transport);
+        text_length = iscsit_build_sendtargets_response(cmd, network_transport,
+                                                        cmd->read_data_done,
+                                                        &completed);
         if (text_length < 0)
                 return text_length;
 
+        if (completed) {
+                hdr->flags |= ISCSI_FLAG_CMD_FINAL;
+        } else {
+                hdr->flags |= ISCSI_FLAG_TEXT_CONTINUE;
+                cmd->read_data_done += text_length;
+                if (cmd->targ_xfer_tag == 0xFFFFFFFF)
+                        cmd->targ_xfer_tag = session_get_next_ttt(conn->sess);
+        }
         hdr->opcode = ISCSI_OP_TEXT_RSP;
-        hdr->flags |= ISCSI_FLAG_CMD_FINAL;
         padding = ((-text_length) & 3);
         hton24(hdr->dlength, text_length);
         hdr->itt = cmd->init_task_tag;
@@ -3535,21 +3568,25 @@ iscsit_build_text_rsp(struct iscsi_cmd *cmd, struct iscsi_conn *conn,
         hdr->statsn = cpu_to_be32(cmd->stat_sn);
 
         iscsit_increment_maxcmdsn(cmd, conn->sess);
+        /*
+         * Reset maxcmdsn_inc in multi-part text payload exchanges to
+         * correctly increment MaxCmdSN for each response answering a
+         * non immediate text request with a valid CmdSN.
+         */
+        cmd->maxcmdsn_inc = 0;
         hdr->exp_cmdsn = cpu_to_be32(conn->sess->exp_cmd_sn);
         hdr->max_cmdsn = cpu_to_be32(conn->sess->max_cmd_sn);
 
-        pr_debug("Built Text Response: ITT: 0x%08x, StatSN: 0x%08x,"
-                " Length: %u, CID: %hu\n", cmd->init_task_tag, cmd->stat_sn,
-                text_length, conn->cid);
+        pr_debug("Built Text Response: ITT: 0x%08x, TTT: 0x%08x, StatSN: 0x%08x,"
+                " Length: %u, CID: %hu F: %d C: %d\n", cmd->init_task_tag,
+                cmd->targ_xfer_tag, cmd->stat_sn, text_length, conn->cid,
+                !!(hdr->flags & ISCSI_FLAG_CMD_FINAL),
+                !!(hdr->flags & ISCSI_FLAG_TEXT_CONTINUE));
 
         return text_length + padding;
 }
 EXPORT_SYMBOL(iscsit_build_text_rsp);
 
-/*
- *      FIXME: Add support for F_BIT and C_BIT when the length is longer than
- *      MaxRecvDataSegmentLength.
- */
 static int iscsit_send_text_rsp(
         struct iscsi_cmd *cmd,
         struct iscsi_conn *conn)
@@ -4013,9 +4050,15 @@ static int iscsi_target_rx_opcode(struct iscsi_conn *conn, unsigned char *buf)
                 ret = iscsit_handle_task_mgt_cmd(conn, cmd, buf);
                 break;
         case ISCSI_OP_TEXT:
-                cmd = iscsit_allocate_cmd(conn, TASK_INTERRUPTIBLE);
-                if (!cmd)
-                        goto reject;
+                if (hdr->ttt != cpu_to_be32(0xFFFFFFFF)) {
+                        cmd = iscsit_find_cmd_from_itt(conn, hdr->itt);
+                        if (!cmd)
+                                goto reject;
+                } else {
+                        cmd = iscsit_allocate_cmd(conn, TASK_INTERRUPTIBLE);
+                        if (!cmd)
+                                goto reject;
+                }
 
                 ret = iscsit_handle_text_cmd(conn, cmd, buf);
                 break;
diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
index c211d3f2726c..390df8ed72b2 100644
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -390,6 +390,7 @@ struct iscsi_cmd *iscsit_find_cmd_from_itt(
                         init_task_tag, conn->cid);
         return NULL;
 }
+EXPORT_SYMBOL(iscsit_find_cmd_from_itt);
 
 struct iscsi_cmd *iscsit_find_cmd_from_itt_or_dump(
         struct iscsi_conn *conn,
diff --git a/drivers/target/iscsi/iscsi_target_util.h b/drivers/target/iscsi/iscsi_target_util.h
index a68508c4fec8..1ab754a671ff 100644
--- a/drivers/target/iscsi/iscsi_target_util.h
+++ b/drivers/target/iscsi/iscsi_target_util.h
@@ -16,7 +16,6 @@ extern struct iscsi_r2t *iscsit_get_holder_for_r2tsn(struct iscsi_cmd *, u32);
 extern int iscsit_sequence_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
                                unsigned char * ,__be32 cmdsn);
 extern int iscsit_check_unsolicited_dataout(struct iscsi_cmd *, unsigned char *);
-extern struct iscsi_cmd *iscsit_find_cmd_from_itt(struct iscsi_conn *, itt_t);
 extern struct iscsi_cmd *iscsit_find_cmd_from_itt_or_dump(struct iscsi_conn *,
                         itt_t, u32);
 extern struct iscsi_cmd *iscsit_find_cmd_from_ttt(struct iscsi_conn *, u32);