target: Fix remote-port TMR ABORT + se_cmd fabric stop

To address the bug where fabric driver level shutdown
of se_cmd occurs at the same time when TMR CMD_T_ABORTED
is happening resulting in a -1 ->cmd_kref, this patch
adds a CMD_T_FABRIC_STOP bit that is used to determine
when TMR + driver I_T nexus shutdown is happening
concurrently.

It changes target_sess_cmd_list_set_waiting() to obtain
se_cmd->cmd_kref + set CMD_T_FABRIC_STOP, and drop local
reference in target_wait_for_sess_cmds() and invoke extra
target_put_sess_cmd() during Task Aborted Status (TAS)
when necessary.

Also, it adds a new target_wait_free_cmd() wrapper around
transport_wait_for_tasks() for the special case within
transport_generic_free_cmd() to set CMD_T_FABRIC_STOP,
and is now aware of CMD_T_ABORTED + CMD_T_TAS status
bits to know when an extra transport_put_cmd() during
TAS is required.

Note transport_generic_free_cmd() is expected to block on
cmd->cmd_wait_comp in order to follow what iscsi-target
expects during iscsi_conn context se_cmd shutdown.

Cc: Quinn Tran <quinn.tran@qlogic.com>
Cc: Himanshu Madhani <himanshu.madhani@qlogic.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Andy Grover <agrover@redhat.com>
Cc: Mike Christie <mchristi@redhat.com>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Nicholas Bellinger <nab@daterainc.com>

3 files changed, 150 insertions, 51 deletions

diff --git a/drivers/target/target_core_tmr.c b/drivers/target/target_core_tmr.c
index 3e0d77a4c7b6..82a663ba9800 100644
--- a/drivers/target/target_core_tmr.c
+++ b/drivers/target/target_core_tmr.c
@@ -75,16 +75,18 @@ void core_tmr_release_req(struct se_tmr_req *tmr)
         kfree(tmr);
 }
 
-static void core_tmr_handle_tas_abort(
-        struct se_session *tmr_sess,
-        struct se_cmd *cmd,
-        int tas)
+static void core_tmr_handle_tas_abort(struct se_cmd *cmd, int tas)
 {
-        bool remove = true;
+        unsigned long flags;
+        bool remove = true, send_tas;
         /*
          * TASK ABORTED status (TAS) bit support
          */
-        if (tmr_sess && tmr_sess != cmd->se_sess && tas) {
+        spin_lock_irqsave(&cmd->t_state_lock, flags);
+        send_tas = (cmd->transport_state & CMD_T_TAS);
+        spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+
+        if (send_tas) {
                 remove = false;
                 transport_send_task_abort(cmd);
         }
@@ -107,7 +109,8 @@ static int target_check_cdb_and_preempt(struct list_head *list,
         return 1;
 }
 
-static bool __target_check_io_state(struct se_cmd *se_cmd)
+static bool __target_check_io_state(struct se_cmd *se_cmd,
+                                    struct se_session *tmr_sess, int tas)
 {
         struct se_session *sess = se_cmd->se_sess;
 
@@ -115,21 +118,32 @@ static bool __target_check_io_state(struct se_cmd *se_cmd)
         WARN_ON_ONCE(!irqs_disabled());
         /*
          * If command already reached CMD_T_COMPLETE state within
-         * target_complete_cmd(), this se_cmd has been passed to
-         * fabric driver and will not be aborted.
+         * target_complete_cmd() or CMD_T_FABRIC_STOP due to shutdown,
+         * this se_cmd has been passed to fabric driver and will
+         * not be aborted.
          *
          * Otherwise, obtain a local se_cmd->cmd_kref now for TMR
          * ABORT_TASK + LUN_RESET for CMD_T_ABORTED processing as
          * long as se_cmd->cmd_kref is still active unless zero.
          */
         spin_lock(&se_cmd->t_state_lock);
-        if (se_cmd->transport_state & CMD_T_COMPLETE) {
-                pr_debug("Attempted to abort io tag: %llu already complete,"
+        if (se_cmd->transport_state & (CMD_T_COMPLETE | CMD_T_FABRIC_STOP)) {
+                pr_debug("Attempted to abort io tag: %llu already complete or"
+                        " fabric stop, skipping\n", se_cmd->tag);
+                spin_unlock(&se_cmd->t_state_lock);
+                return false;
+        }
+        if (sess->sess_tearing_down || se_cmd->cmd_wait_set) {
+                pr_debug("Attempted to abort io tag: %llu already shutdown,"
                         " skipping\n", se_cmd->tag);
                 spin_unlock(&se_cmd->t_state_lock);
                 return false;
         }
         se_cmd->transport_state |= CMD_T_ABORTED;
+
+        if ((tmr_sess != se_cmd->se_sess) && tas)
+                se_cmd->transport_state |= CMD_T_TAS;
+
         spin_unlock(&se_cmd->t_state_lock);
 
         return kref_get_unless_zero(&se_cmd->cmd_kref);
@@ -161,7 +175,7 @@ void core_tmr_abort_task(
                 printk("ABORT_TASK: Found referenced %s task_tag: %llu\n",
                         se_cmd->se_tfo->get_fabric_name(), ref_tag);
 
-                if (!__target_check_io_state(se_cmd)) {
+                if (!__target_check_io_state(se_cmd, se_sess, 0)) {
                         spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
                         target_put_sess_cmd(se_cmd);
                         goto out;
@@ -230,7 +244,8 @@ static void core_tmr_drain_tmr_list(
 
                 spin_lock(&sess->sess_cmd_lock);
                 spin_lock(&cmd->t_state_lock);
-                if (!(cmd->transport_state & CMD_T_ACTIVE)) {
+                if (!(cmd->transport_state & CMD_T_ACTIVE) ||
+                     (cmd->transport_state & CMD_T_FABRIC_STOP)) {
                         spin_unlock(&cmd->t_state_lock);
                         spin_unlock(&sess->sess_cmd_lock);
                         continue;
@@ -240,15 +255,22 @@ static void core_tmr_drain_tmr_list(
                         spin_unlock(&sess->sess_cmd_lock);
                         continue;
                 }
+                if (sess->sess_tearing_down || cmd->cmd_wait_set) {
+                        spin_unlock(&cmd->t_state_lock);
+                        spin_unlock(&sess->sess_cmd_lock);
+                        continue;
+                }
                 cmd->transport_state |= CMD_T_ABORTED;
                 spin_unlock(&cmd->t_state_lock);
 
                 rc = kref_get_unless_zero(&cmd->cmd_kref);
-                spin_unlock(&sess->sess_cmd_lock);
                 if (!rc) {
                         printk("LUN_RESET TMR: non-zero kref_get_unless_zero\n");
+                        spin_unlock(&sess->sess_cmd_lock);
                         continue;
                 }
+                spin_unlock(&sess->sess_cmd_lock);
+
                 list_move_tail(&tmr_p->tmr_list, &drain_tmr_list);
         }
         spin_unlock_irqrestore(&dev->se_tmr_lock, flags);
@@ -325,7 +347,7 @@ static void core_tmr_drain_state_list(
                         continue;
 
                 spin_lock(&sess->sess_cmd_lock);
-                rc = __target_check_io_state(cmd);
+                rc = __target_check_io_state(cmd, tmr_sess, tas);
                 spin_unlock(&sess->sess_cmd_lock);
                 if (!rc)
                         continue;
@@ -364,7 +386,7 @@ static void core_tmr_drain_state_list(
                 cancel_work_sync(&cmd->work);
                 transport_wait_for_tasks(cmd);
 
-                core_tmr_handle_tas_abort(tmr_sess, cmd, tas);
+                core_tmr_handle_tas_abort(cmd, tas);
                 target_put_sess_cmd(cmd);
         }
 }
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 94e372af9e28..3441b159e306 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2431,18 +2431,33 @@ static void transport_write_pending_qf(struct se_cmd *cmd)
         }
 }
 
+static bool
+__transport_wait_for_tasks(struct se_cmd *, bool, bool *, bool *,
+                           unsigned long *flags);
+
+static void target_wait_free_cmd(struct se_cmd *cmd, bool *aborted, bool *tas)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&cmd->t_state_lock, flags);
+        __transport_wait_for_tasks(cmd, true, aborted, tas, &flags);
+        spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+}
+
 int transport_generic_free_cmd(struct se_cmd *cmd, int wait_for_tasks)
 {
         int ret = 0;
+        bool aborted = false, tas = false;
 
         if (!(cmd->se_cmd_flags & SCF_SE_LUN_CMD)) {
                 if (wait_for_tasks && (cmd->se_cmd_flags & SCF_SCSI_TMR_CDB))
-                        transport_wait_for_tasks(cmd);
+                        target_wait_free_cmd(cmd, &aborted, &tas);
 
-                ret = transport_put_cmd(cmd);
+                if (!aborted || tas)
+                        ret = transport_put_cmd(cmd);
         } else {
                 if (wait_for_tasks)
-                        transport_wait_for_tasks(cmd);
+                        target_wait_free_cmd(cmd, &aborted, &tas);
                 /*
                  * Handle WRITE failure case where transport_generic_new_cmd()
                  * has already added se_cmd to state_list, but fabric has
@@ -2454,7 +2469,20 @@ int transport_generic_free_cmd(struct se_cmd *cmd, int wait_for_tasks)
                 if (cmd->se_lun)
                         transport_lun_remove_cmd(cmd);
 
-                ret = transport_put_cmd(cmd);
+                if (!aborted || tas)
+                        ret = transport_put_cmd(cmd);
+        }
+        /*
+         * If the task has been internally aborted due to TMR ABORT_TASK
+         * or LUN_RESET, target_core_tmr.c is responsible for performing
+         * the remaining calls to target_put_sess_cmd(), and not the
+         * callers of this function.
+         */
+        if (aborted) {
+                pr_debug("Detected CMD_T_ABORTED for ITT: %llu\n", cmd->tag);
+                wait_for_completion(&cmd->cmd_wait_comp);
+                cmd->se_tfo->release_cmd(cmd);
+                ret = 1;
         }
         return ret;
 }
@@ -2509,6 +2537,7 @@ static void target_release_cmd_kref(struct kref *kref)
         struct se_cmd *se_cmd = container_of(kref, struct se_cmd, cmd_kref);
         struct se_session *se_sess = se_cmd->se_sess;
         unsigned long flags;
+        bool fabric_stop;
 
         spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
         if (list_empty(&se_cmd->se_cmd_list)) {
@@ -2517,13 +2546,19 @@ static void target_release_cmd_kref(struct kref *kref)
                 se_cmd->se_tfo->release_cmd(se_cmd);
                 return;
         }
-        if (se_sess->sess_tearing_down && se_cmd->cmd_wait_set) {
+
+        spin_lock(&se_cmd->t_state_lock);
+        fabric_stop = (se_cmd->transport_state & CMD_T_FABRIC_STOP);
+        spin_unlock(&se_cmd->t_state_lock);
+
+        if (se_cmd->cmd_wait_set || fabric_stop) {
+                list_del_init(&se_cmd->se_cmd_list);
                 spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
                 target_free_cmd_mem(se_cmd);
                 complete(&se_cmd->cmd_wait_comp);
                 return;
         }
-        list_del(&se_cmd->se_cmd_list);
+        list_del_init(&se_cmd->se_cmd_list);
         spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
 
         target_free_cmd_mem(se_cmd);
@@ -2555,6 +2590,7 @@ void target_sess_cmd_list_set_waiting(struct se_session *se_sess)
 {
         struct se_cmd *se_cmd;
         unsigned long flags;
+        int rc;
 
         spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
         if (se_sess->sess_tearing_down) {
@@ -2564,8 +2600,15 @@ void target_sess_cmd_list_set_waiting(struct se_session *se_sess)
         se_sess->sess_tearing_down = 1;
         list_splice_init(&se_sess->sess_cmd_list, &se_sess->sess_wait_list);
 
-        list_for_each_entry(se_cmd, &se_sess->sess_wait_list, se_cmd_list)
-                se_cmd->cmd_wait_set = 1;
+        list_for_each_entry(se_cmd, &se_sess->sess_wait_list, se_cmd_list) {
+                rc = kref_get_unless_zero(&se_cmd->cmd_kref);
+                if (rc) {
+                        se_cmd->cmd_wait_set = 1;
+                        spin_lock(&se_cmd->t_state_lock);
+                        se_cmd->transport_state |= CMD_T_FABRIC_STOP;
+                        spin_unlock(&se_cmd->t_state_lock);
+                }
+        }
 
         spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
 }
@@ -2578,15 +2621,25 @@ void target_wait_for_sess_cmds(struct se_session *se_sess)
 {
         struct se_cmd *se_cmd, *tmp_cmd;
         unsigned long flags;
+        bool tas;
 
         list_for_each_entry_safe(se_cmd, tmp_cmd,
                                 &se_sess->sess_wait_list, se_cmd_list) {
-                list_del(&se_cmd->se_cmd_list);
+                list_del_init(&se_cmd->se_cmd_list);
 
                 pr_debug("Waiting for se_cmd: %p t_state: %d, fabric state:"
                         " %d\n", se_cmd, se_cmd->t_state,
                         se_cmd->se_tfo->get_cmd_state(se_cmd));
 
+                spin_lock_irqsave(&se_cmd->t_state_lock, flags);
+                tas = (se_cmd->transport_state & CMD_T_TAS);
+                spin_unlock_irqrestore(&se_cmd->t_state_lock, flags);
+
+                if (!target_put_sess_cmd(se_cmd)) {
+                        if (tas)
+                                target_put_sess_cmd(se_cmd);
+                }
+
                 wait_for_completion(&se_cmd->cmd_wait_comp);
                 pr_debug("After cmd_wait_comp: se_cmd: %p t_state: %d"
                         " fabric state: %d\n", se_cmd, se_cmd->t_state,
@@ -2608,53 +2661,75 @@ void transport_clear_lun_ref(struct se_lun *lun)
         wait_for_completion(&lun->lun_ref_comp);
 }
 
-/**
- * transport_wait_for_tasks - wait for completion to occur
- * @cmd:        command to wait
- *
- * Called from frontend fabric context to wait for storage engine
- * to pause and/or release frontend generated struct se_cmd.
- */
-bool transport_wait_for_tasks(struct se_cmd *cmd)
+static bool
+__transport_wait_for_tasks(struct se_cmd *cmd, bool fabric_stop,
+                           bool *aborted, bool *tas, unsigned long *flags)
+        __releases(&cmd->t_state_lock)
+        __acquires(&cmd->t_state_lock)
 {
-        unsigned long flags;
 
-        spin_lock_irqsave(&cmd->t_state_lock, flags);
+        assert_spin_locked(&cmd->t_state_lock);
+        WARN_ON_ONCE(!irqs_disabled());
+
+        if (fabric_stop)
+                cmd->transport_state |= CMD_T_FABRIC_STOP;
+
+        if (cmd->transport_state & CMD_T_ABORTED)
+                *aborted = true;
+
+        if (cmd->transport_state & CMD_T_TAS)
+                *tas = true;
+
         if (!(cmd->se_cmd_flags & SCF_SE_LUN_CMD) &&
-            !(cmd->se_cmd_flags & SCF_SCSI_TMR_CDB)) {
-                spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+            !(cmd->se_cmd_flags & SCF_SCSI_TMR_CDB))
                 return false;
-        }
 
         if (!(cmd->se_cmd_flags & SCF_SUPPORTED_SAM_OPCODE) &&
-            !(cmd->se_cmd_flags & SCF_SCSI_TMR_CDB)) {
-                spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+            !(cmd->se_cmd_flags & SCF_SCSI_TMR_CDB))
                 return false;
-        }
 
-        if (!(cmd->transport_state & CMD_T_ACTIVE)) {
-                spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+        if (!(cmd->transport_state & CMD_T_ACTIVE))
+                return false;
+
+        if (fabric_stop && *aborted)
                 return false;
-        }
 
         cmd->transport_state |= CMD_T_STOP;
 
-        pr_debug("wait_for_tasks: Stopping %p ITT: 0x%08llx i_state: %d, t_state: %d, CMD_T_STOP\n",
-                cmd, cmd->tag, cmd->se_tfo->get_cmd_state(cmd), cmd->t_state);
+        pr_debug("wait_for_tasks: Stopping %p ITT: 0x%08llx i_state: %d,"
+                 " t_state: %d, CMD_T_STOP\n", cmd, cmd->tag,
+                 cmd->se_tfo->get_cmd_state(cmd), cmd->t_state);
 
-        spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+        spin_unlock_irqrestore(&cmd->t_state_lock, *flags);
 
         wait_for_completion(&cmd->t_transport_stop_comp);
 
-        spin_lock_irqsave(&cmd->t_state_lock, flags);
+        spin_lock_irqsave(&cmd->t_state_lock, *flags);
         cmd->transport_state &= ~(CMD_T_ACTIVE | CMD_T_STOP);
 
-        pr_debug("wait_for_tasks: Stopped wait_for_completion(&cmd->t_transport_stop_comp) for ITT: 0x%08llx\n",
-                cmd->tag);
+        pr_debug("wait_for_tasks: Stopped wait_for_completion(&cmd->"
+                 "t_transport_stop_comp) for ITT: 0x%08llx\n", cmd->tag);
 
+        return true;
+}
+
+/**
+ * transport_wait_for_tasks - wait for completion to occur
+ * @cmd:        command to wait
+ *
+ * Called from frontend fabric context to wait for storage engine
+ * to pause and/or release frontend generated struct se_cmd.
+ */
+bool transport_wait_for_tasks(struct se_cmd *cmd)
+{
+        unsigned long flags;
+        bool ret, aborted = false, tas = false;
+
+        spin_lock_irqsave(&cmd->t_state_lock, flags);
+        ret = __transport_wait_for_tasks(cmd, false, &aborted, &tas, &flags);
         spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 
-        return true;
+        return ret;
 }
 EXPORT_SYMBOL(transport_wait_for_tasks);
 
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 1a76726c45a2..1579539e5669 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -493,6 +493,8 @@ struct se_cmd {
 #define CMD_T_DEV_ACTIVE        (1 << 7)
 #define CMD_T_REQUEST_STOP      (1 << 8)
 #define CMD_T_BUSY              (1 << 9)
+#define CMD_T_TAS               (1 << 10)
+#define CMD_T_FABRIC_STOP       (1 << 11)
         spinlock_t              t_state_lock;
         struct kref             cmd_kref;
         struct completion       t_transport_stop_comp;