target: Fix ordered task target_setup_cmd_from_cdb exception hang

If a command with a Simple task attribute is failed due to a Unit
Attention, then a subsequent command with an Ordered task attribute
will hang forever.  The reason for this is that the Unit Attention
status is checked for in target_setup_cmd_from_cdb, before the call
to target_execute_cmd, which calls target_handle_task_attr, which
in turn increments dev->simple_cmds.

However, transport_generic_request_failure still calls
transport_complete_task_attr, which will decrement dev->simple_cmds.
In this case, simple_cmds is now -1.  So when a command with the
Ordered task attribute is sent, target_handle_task_attr sees that
dev->simple_cmds is not 0, so it decides it can't execute the
command until all the (nonexistent) Simple commands have completed.

Reported-by: Michael Cyr <mikecyr@linux.vnet.ibm.com>
Tested-by: Michael Cyr <mikecyr@linux.vnet.ibm.com>
Reported-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
Tested-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org # 4.4+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/target_core_internal.h b/drivers/target/target_core_internal.h
index fc91e85f54ba683dd298afc6db1d907192cef598..e2c970a9d61c32c7a95d034f889992a7560fdb64 100644 (file)
--- a/drivers/target/target_core_internal.h
+++ b/drivers/target/target_core_internal.h
@@ -146,6 +146,7 @@ sense_reason_t      target_cmd_size_check(struct se_cmd *cmd, unsigned int size);
 void   target_qf_do_work(struct work_struct *work);
 bool   target_check_wce(struct se_device *dev);
 bool   target_check_fua(struct se_device *dev);
+void   __target_execute_cmd(struct se_cmd *, bool);
 
 /* target_core_stat.c */
 void   target_stat_setup_dev_default_groups(struct se_device *);

diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c
index a9057aa07176ff240748372215333dd531296ca2..04f616b3ba0a848a80d4a70c084c1b45d406c168 100644 (file)
--- a/drivers/target/target_core_sbc.c
+++ b/drivers/target/target_core_sbc.c
@@ -602,7 +602,7 @@ static sense_reason_t compare_and_write_callback(struct se_cmd *cmd, bool succes
        cmd->transport_state |= CMD_T_ACTIVE|CMD_T_BUSY|CMD_T_SENT;
        spin_unlock_irq(&cmd->t_state_lock);
 
-       __target_execute_cmd(cmd);
+       __target_execute_cmd(cmd, false);
 
        kfree(buf);
        return ret;

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 38bf2dcf926af42e94ed060f65813a64f94c9850..a6e1edcfefbdc5a4677dc7c37a351c3ab7bd25f5 100644 (file)
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1303,23 +1303,6 @@ target_setup_cmd_from_cdb(struct se_cmd *cmd, unsigned char *cdb)
 
        trace_target_sequencer_start(cmd);
 
-       /*
-        * Check for an existing UNIT ATTENTION condition
-        */
-       ret = target_scsi3_ua_check(cmd);
-       if (ret)
-               return ret;
-
-       ret = target_alua_state_check(cmd);
-       if (ret)
-               return ret;
-
-       ret = target_check_reservation(cmd);
-       if (ret) {
-               cmd->scsi_status = SAM_STAT_RESERVATION_CONFLICT;
-               return ret;
-       }
-
        ret = dev->transport->parse_cdb(cmd);
        if (ret == TCM_UNSUPPORTED_SCSI_OPCODE)
                pr_warn_ratelimited("%s/%s: Unsupported SCSI Opcode 0x%02x, sending CHECK_CONDITION.\n",
@@ -1761,20 +1744,45 @@ queue_full:
 }
 EXPORT_SYMBOL(transport_generic_request_failure);
 
-void __target_execute_cmd(struct se_cmd *cmd)
+void __target_execute_cmd(struct se_cmd *cmd, bool do_checks)
 {
        sense_reason_t ret;
 
-       if (cmd->execute_cmd) {
-               ret = cmd->execute_cmd(cmd);
-               if (ret) {
-                       spin_lock_irq(&cmd->t_state_lock);
-                       cmd->transport_state &= ~(CMD_T_BUSY|CMD_T_SENT);
-                       spin_unlock_irq(&cmd->t_state_lock);
+       if (!cmd->execute_cmd) {
+               ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+               goto err;
+       }
+       if (do_checks) {
+               /*
+                * Check for an existing UNIT ATTENTION condition after
+                * target_handle_task_attr() has done SAM task attr
+                * checking, and possibly have already defered execution
+                * out to target_restart_delayed_cmds() context.
+                */
+               ret = target_scsi3_ua_check(cmd);
+               if (ret)
+                       goto err;
+
+               ret = target_alua_state_check(cmd);
+               if (ret)
+                       goto err;
 
-                       transport_generic_request_failure(cmd, ret);
+               ret = target_check_reservation(cmd);
+               if (ret) {
+                       cmd->scsi_status = SAM_STAT_RESERVATION_CONFLICT;
+                       goto err;
                }
        }
+
+       ret = cmd->execute_cmd(cmd);
+       if (!ret)
+               return;
+err:
+       spin_lock_irq(&cmd->t_state_lock);
+       cmd->transport_state &= ~(CMD_T_BUSY|CMD_T_SENT);
+       spin_unlock_irq(&cmd->t_state_lock);
+
+       transport_generic_request_failure(cmd, ret);
 }
 
 static int target_write_prot_action(struct se_cmd *cmd)
@@ -1899,7 +1907,7 @@ void target_execute_cmd(struct se_cmd *cmd)
                return;
        }
 
-       __target_execute_cmd(cmd);
+       __target_execute_cmd(cmd, true);
 }
 EXPORT_SYMBOL(target_execute_cmd);
 
@@ -1923,7 +1931,7 @@ static void target_restart_delayed_cmds(struct se_device *dev)
                list_del(&cmd->se_delayed_node);
                spin_unlock(&dev->delayed_cmd_lock);
 
-               __target_execute_cmd(cmd);
+               __target_execute_cmd(cmd, true);
 
                if (cmd->sam_task_attr == TCM_ORDERED_TAG)
                        break;

diff --git a/include/target/target_core_fabric.h b/include/target/target_core_fabric.h
index de44462a7680c2071a4f37088e7241209de117f3..5cd6faa6e0d166ed07444cf5e3735e2626483205 100644 (file)
--- a/include/target/target_core_fabric.h
+++ b/include/target/target_core_fabric.h
@@ -163,7 +163,6 @@ int core_tmr_alloc_req(struct se_cmd *, void *, u8, gfp_t);
 void   core_tmr_release_req(struct se_tmr_req *);
 int    transport_generic_handle_tmr(struct se_cmd *);
 void   transport_generic_request_failure(struct se_cmd *, sense_reason_t);
-void   __target_execute_cmd(struct se_cmd *);
 int    transport_lookup_tmr_lun(struct se_cmd *, u64);
 void   core_allocate_nexus_loss_ua(struct se_node_acl *acl);