target: Convert ->transport_wait_for_tasks usage to transport_generic_free_cmd

This patch converts se_cmd->transport_wait_for_tasks(se_cmd, 1) usage to use
transport_generic_free_cmd() directly in target-core and iscsi-target fabric
usage.  The includes:

*) Removal of the optional transport_generic_free_cmd() call from within
   transport_generic_wait_for_tasks()
*) Usage of existing SCF_SUPPORTED_SAM_OPCODE to determine when
   transport_generic_wait_for_tasks() processing may occur instead of
   checking se_cmd->transport_wait_for_tasks()
*) Move transport_generic_wait_for_tasks() call ahead of core_dec_lacl_count()
   and transport_lun_remove_cmd() in transport_generic_free_cmd() to follow
   existing logic for iscsi-target w/ se_cmd->transport_wait_for_tasks(se_cmd, 1)
*) Removal of se_cmd->transport_wait_for_tasks() function pointer
*) Rename transport_generic_wait_for_tasks() -> transport_wait_for_tasks(), and
   add docbook comment.
*) Add EXPORT_SYMBOL for transport_wait_for_tasks()

For the case in iscsi_target_erl2.c:iscsit_prepare_cmds_for_realligance()
where se_cmd->transport_wait_for_tasks(se_cmd, 0) is called, this patch
adds a direct call to transport_wait_for_tasks().

(hch: Fix transport_generic_free_cmd() usage in iscsit_release_commands_from_conn)
(nab: Add patch: Ensure that TMRs hit wait_for_tasks logic during release)

Reported-by: Christoph Hellwig <hch@lst.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

3 files changed, 50 insertions, 85 deletions

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 354a8339a3f9..e4b9ba296dcf 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -3940,7 +3940,6 @@ static void iscsit_release_commands_from_conn(struct iscsi_conn *conn)
 {
         struct iscsi_cmd *cmd = NULL, *cmd_tmp = NULL;
         struct iscsi_session *sess = conn->sess;
-        struct se_cmd *se_cmd;
         /*
          * We expect this function to only ever be called from either RX or TX
          * thread context via iscsit_close_connection() once the other context
@@ -3953,16 +3952,13 @@ static void iscsit_release_commands_from_conn(struct iscsi_conn *conn)
                         list_del(&cmd->i_list);
                         spin_unlock_bh(&conn->cmd_lock);
                         iscsit_increment_maxcmdsn(cmd, sess);
-                        se_cmd = &cmd->se_cmd;
                         /*
                          * Special cases for active iSCSI TMR, and
                          * transport_lookup_cmd_lun() failing from
                          * iscsit_get_lun_for_cmd() in iscsit_handle_scsi_cmd().
                          */
-                        if (cmd->tmr_req && se_cmd->transport_wait_for_tasks)
-                                se_cmd->transport_wait_for_tasks(se_cmd, 1);
-                        else if (cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD)
-                                transport_release_cmd(se_cmd);
+                        if (cmd->tmr_req)
+                                transport_generic_free_cmd(&cmd->se_cmd, 1);
                         else
                                 iscsit_release_cmd(cmd);
 
@@ -3973,10 +3969,8 @@ static void iscsit_release_commands_from_conn(struct iscsi_conn *conn)
                 spin_unlock_bh(&conn->cmd_lock);
 
                 iscsit_increment_maxcmdsn(cmd, sess);
-                se_cmd = &cmd->se_cmd;
 
-                if (se_cmd->transport_wait_for_tasks)
-                        se_cmd->transport_wait_for_tasks(se_cmd, 1);
+                transport_generic_free_cmd(&cmd->se_cmd, 1);
 
                 spin_lock_bh(&conn->cmd_lock);
         }
diff --git a/drivers/target/iscsi/iscsi_target_erl2.c b/drivers/target/iscsi/iscsi_target_erl2.c
index 000356baf0b5..c3803b2fdd65 100644
--- a/drivers/target/iscsi/iscsi_target_erl2.c
+++ b/drivers/target/iscsi/iscsi_target_erl2.c
@@ -143,12 +143,10 @@ void iscsit_free_connection_recovery_entires(struct iscsi_session *sess)
                         list_del(&cmd->i_list);
                         cmd->conn = NULL;
                         spin_unlock(&cr->conn_recovery_cmd_lock);
-                        if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD) ||
-                            !(cmd->se_cmd.transport_wait_for_tasks))
+                        if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD))
                                 iscsit_release_cmd(cmd);
                         else
-                                cmd->se_cmd.transport_wait_for_tasks(
-                                                &cmd->se_cmd, 1);
+                                transport_generic_free_cmd(&cmd->se_cmd, 1);
                         spin_lock(&cr->conn_recovery_cmd_lock);
                 }
                 spin_unlock(&cr->conn_recovery_cmd_lock);
@@ -170,12 +168,10 @@ void iscsit_free_connection_recovery_entires(struct iscsi_session *sess)
                         list_del(&cmd->i_list);
                         cmd->conn = NULL;
                         spin_unlock(&cr->conn_recovery_cmd_lock);
-                        if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD) ||
-                            !(cmd->se_cmd.transport_wait_for_tasks))
+                        if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD))
                                 iscsit_release_cmd(cmd);
                         else
-                                cmd->se_cmd.transport_wait_for_tasks(
-                                                &cmd->se_cmd, 1);
+                                transport_generic_free_cmd(&cmd->se_cmd, 1);
                         spin_lock(&cr->conn_recovery_cmd_lock);
                 }
                 spin_unlock(&cr->conn_recovery_cmd_lock);
@@ -260,12 +256,10 @@ void iscsit_discard_cr_cmds_by_expstatsn(
                 iscsit_remove_cmd_from_connection_recovery(cmd, sess);
 
                 spin_unlock(&cr->conn_recovery_cmd_lock);
-                if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD) ||
-                    !(cmd->se_cmd.transport_wait_for_tasks))
+                if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD))
                         iscsit_release_cmd(cmd);
                 else
-                        cmd->se_cmd.transport_wait_for_tasks(
-                                        &cmd->se_cmd, 1);
+                        transport_generic_free_cmd(&cmd->se_cmd, 1);
                 spin_lock(&cr->conn_recovery_cmd_lock);
         }
         spin_unlock(&cr->conn_recovery_cmd_lock);
@@ -319,12 +313,10 @@ int iscsit_discard_unacknowledged_ooo_cmdsns_for_conn(struct iscsi_conn *conn)
                 list_del(&cmd->i_list);
 
                 spin_unlock_bh(&conn->cmd_lock);
-                if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD) ||
-                    !(cmd->se_cmd.transport_wait_for_tasks))
+                if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD))
                         iscsit_release_cmd(cmd);
                 else
-                        cmd->se_cmd.transport_wait_for_tasks(
-                                        &cmd->se_cmd, 1);
+                        transport_generic_free_cmd(&cmd->se_cmd, 1);
                 spin_lock_bh(&conn->cmd_lock);
         }
         spin_unlock_bh(&conn->cmd_lock);
@@ -378,12 +370,10 @@ int iscsit_prepare_cmds_for_realligance(struct iscsi_conn *conn)
                         list_del(&cmd->i_list);
                         spin_unlock_bh(&conn->cmd_lock);
 
-                        if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD) ||
-                            !(cmd->se_cmd.transport_wait_for_tasks))
+                        if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD))
                                 iscsit_release_cmd(cmd);
                         else
-                                cmd->se_cmd.transport_wait_for_tasks(
-                                                &cmd->se_cmd, 1);
+                                transport_generic_free_cmd(&cmd->se_cmd, 1);
                         spin_lock_bh(&conn->cmd_lock);
                         continue;
                 }
@@ -404,12 +394,10 @@ int iscsit_prepare_cmds_for_realligance(struct iscsi_conn *conn)
                         list_del(&cmd->i_list);
                         spin_unlock_bh(&conn->cmd_lock);
 
-                        if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD) ||
-                            !(cmd->se_cmd.transport_wait_for_tasks))
+                        if (!(cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD))
                                 iscsit_release_cmd(cmd);
                         else
-                                cmd->se_cmd.transport_wait_for_tasks(
-                                                &cmd->se_cmd, 1);
+                                transport_generic_free_cmd(&cmd->se_cmd, 1);
                         spin_lock_bh(&conn->cmd_lock);
                         continue;
                 }
@@ -434,9 +422,8 @@ int iscsit_prepare_cmds_for_realligance(struct iscsi_conn *conn)
 
                 iscsit_free_all_datain_reqs(cmd);
 
-                if ((cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD) &&
-                     cmd->se_cmd.transport_wait_for_tasks)
-                        cmd->se_cmd.transport_wait_for_tasks(&cmd->se_cmd, 0);
+                if (cmd->se_cmd.se_cmd_flags & SCF_SE_LUN_CMD)
+                        transport_wait_for_tasks(&cmd->se_cmd);
                 /*
                  * Add the struct iscsi_cmd to the connection recovery cmd list
                  */
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index ae1efc7c9ec6..f8de042e532e 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1638,8 +1638,6 @@ static int transport_check_alloc_task_attr(struct se_cmd *cmd)
         return 0;
 }
 
-static void transport_generic_wait_for_tasks(struct se_cmd *, int);
-
 /*      transport_generic_allocate_tasks():
  *
  *      Called from fabric RX Thread.
@@ -1651,12 +1649,6 @@ int transport_generic_allocate_tasks(
         int ret;
 
         transport_generic_prepare_cdb(cdb);
-
-        /*
-         * This is needed for early exceptions.
-         */
-        cmd->transport_wait_for_tasks = &transport_generic_wait_for_tasks;
-
         /*
          * Ensure that the received CDB is less than the max (252 + 8) bytes
          * for VARIABLE_LENGTH_CMD
@@ -1739,7 +1731,7 @@ int transport_handle_cdb_direct(
          * Set TRANSPORT_NEW_CMD state and cmd->t_transport_active=1 following
          * transport_generic_handle_cdb*() -> transport_add_cmd_to_queue()
          * in existing usage to ensure that outstanding descriptors are handled
-         * correctly during shutdown via transport_generic_wait_for_tasks()
+         * correctly during shutdown via transport_wait_for_tasks()
          *
          * Also, we don't take cmd->t_state_lock here as we only expect
          * this to be called for initial descriptor submission.
@@ -1819,11 +1811,6 @@ EXPORT_SYMBOL(transport_generic_handle_data);
 int transport_generic_handle_tmr(
         struct se_cmd *cmd)
 {
-        /*
-         * This is needed for early exceptions.
-         */
-        cmd->transport_wait_for_tasks = &transport_generic_wait_for_tasks;
-
         transport_add_cmd_to_queue(cmd, TRANSPORT_PROCESS_TMR);
         return 0;
 }
@@ -2504,8 +2491,6 @@ void transport_new_cmd_failure(struct se_cmd *se_cmd)
         spin_unlock_irqrestore(&se_cmd->t_state_lock, flags);
 }
 
-static void transport_nop_wait_for_tasks(struct se_cmd *, int);
-
 static inline u32 transport_get_sectors_6(
         unsigned char *cdb,
         struct se_cmd *cmd,
@@ -2780,7 +2765,6 @@ static int transport_get_sense_data(struct se_cmd *cmd)
 static int
 transport_handle_reservation_conflict(struct se_cmd *cmd)
 {
-        cmd->transport_wait_for_tasks = &transport_nop_wait_for_tasks;
         cmd->se_cmd_flags |= SCF_SCSI_CDB_EXCEPTION;
         cmd->se_cmd_flags |= SCF_SCSI_RESERVATION_CONFLICT;
         cmd->scsi_status = SAM_STAT_RESERVATION_CONFLICT;
@@ -2881,8 +2865,6 @@ static int transport_generic_cmd_sequencer(
          * Check for an existing UNIT ATTENTION condition
          */
         if (core_scsi3_ua_check(cmd, cdb) < 0) {
-                cmd->transport_wait_for_tasks =
-                                &transport_nop_wait_for_tasks;
                 cmd->se_cmd_flags |= SCF_SCSI_CDB_EXCEPTION;
                 cmd->scsi_sense_reason = TCM_CHECK_CONDITION_UNIT_ATTENTION;
                 return -EINVAL;
@@ -2892,7 +2874,6 @@ static int transport_generic_cmd_sequencer(
          */
         ret = su_dev->t10_alua.alua_state_check(cmd, cdb, &alua_ascq);
         if (ret != 0) {
-                cmd->transport_wait_for_tasks = &transport_nop_wait_for_tasks;
                 /*
                  * Set SCSI additional sense code (ASC) to 'LUN Not Accessible';
                  * The ALUA additional sense code qualifier (ASCQ) is determined
@@ -3396,7 +3377,6 @@ static int transport_generic_cmd_sequencer(
                 pr_warn("TARGET_CORE[%s]: Unsupported SCSI Opcode"
                         " 0x%02x, sending CHECK_CONDITION.\n",
                         cmd->se_tfo->get_fabric_name(), cdb[0]);
-                cmd->transport_wait_for_tasks = &transport_nop_wait_for_tasks;
                 goto out_unsupported_cdb;
         }
 
@@ -4304,17 +4284,20 @@ EXPORT_SYMBOL(transport_release_cmd);
 
 void transport_generic_free_cmd(struct se_cmd *cmd, int wait_for_tasks)
 {
-        if (!(cmd->se_cmd_flags & SCF_SE_LUN_CMD))
+        if (!(cmd->se_cmd_flags & SCF_SE_LUN_CMD)) {
+                if (wait_for_tasks && cmd->se_tmr_req)
+                         transport_wait_for_tasks(cmd);
+
                 transport_release_cmd(cmd);
-        else {
+        } else {
+                if (wait_for_tasks)
+                        transport_wait_for_tasks(cmd);
+
                 core_dec_lacl_count(cmd->se_sess->se_node_acl, cmd);
 
                 if (cmd->se_lun)
                         transport_lun_remove_cmd(cmd);
 
-                if (wait_for_tasks && cmd->transport_wait_for_tasks)
-                        cmd->transport_wait_for_tasks(cmd, 0);
-
                 transport_free_dev_tasks(cmd);
 
                 transport_put_cmd(cmd);
@@ -4322,13 +4305,6 @@ void transport_generic_free_cmd(struct se_cmd *cmd, int wait_for_tasks)
 }
 EXPORT_SYMBOL(transport_generic_free_cmd);
 
-static void transport_nop_wait_for_tasks(
-        struct se_cmd *cmd,
-        int remove_cmd)
-{
-        return;
-}
-
 /*      transport_lun_wait_for_tasks():
  *
  *      Called from ConfigFS context to stop the passed struct se_cmd to allow
@@ -4498,21 +4474,30 @@ int transport_clear_lun_from_sessions(struct se_lun *lun)
         return 0;
 }
 
-/*      transport_generic_wait_for_tasks():
+/**
+ * transport_wait_for_tasks - wait for completion to occur
+ * @cmd:        command to wait
  *
- *      Called from frontend or passthrough context to wait for storage engine
- *      to pause and/or release frontend generated struct se_cmd.
+ * Called from frontend fabric context to wait for storage engine
+ * to pause and/or release frontend generated struct se_cmd.
  */
-static void transport_generic_wait_for_tasks(
-        struct se_cmd *cmd,
-        int remove_cmd)
+void transport_wait_for_tasks(struct se_cmd *cmd)
 {
         unsigned long flags;
 
-        if (!(cmd->se_cmd_flags & SCF_SE_LUN_CMD) && !(cmd->se_tmr_req))
-                return;
-
         spin_lock_irqsave(&cmd->t_state_lock, flags);
+        if (!(cmd->se_cmd_flags & SCF_SE_LUN_CMD) && !(cmd->se_tmr_req)) {
+                spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+                return;
+        }
+        /*
+         * Only perform a possible wait_for_tasks if SCF_SUPPORTED_SAM_OPCODE
+         * has been set in transport_set_supported_SAM_opcode().
+         */
+        if (!(cmd->se_cmd_flags & SCF_SUPPORTED_SAM_OPCODE) && !cmd->se_tmr_req) {
+                spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+                return;
+        }
         /*
          * If we are already stopped due to an external event (ie: LUN shutdown)
          * sleep until the connection can have the passed struct se_cmd back.
@@ -4552,8 +4537,10 @@ static void transport_generic_wait_for_tasks(
                 atomic_set(&cmd->transport_lun_stop, 0);
         }
         if (!atomic_read(&cmd->t_transport_active) ||
-             atomic_read(&cmd->t_transport_aborted))
-                goto remove;
+             atomic_read(&cmd->t_transport_aborted)) {
+                spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+                return;
+        }
 
         atomic_set(&cmd->t_transport_stop, 1);
 
@@ -4576,13 +4563,10 @@ static void transport_generic_wait_for_tasks(
         pr_debug("wait_for_tasks: Stopped wait_for_compltion("
                 "&cmd->t_transport_stop_comp) for ITT: 0x%08x\n",
                 cmd->se_tfo->get_task_tag(cmd));
-remove:
-        spin_unlock_irqrestore(&cmd->t_state_lock, flags);
-        if (!remove_cmd)
-                return;
 
-        transport_generic_free_cmd(cmd, 0);
+        spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 }
+EXPORT_SYMBOL(transport_wait_for_tasks);
 
 static int transport_get_sense_codes(
         struct se_cmd *cmd,