Reimplement dropping of TM requests in a more reliable manner

git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@5395 d57e44dd-8a1f-0410-8b47-8ef2f437770f

iscsi-scst/kernel/iscsi.c

@@ -61,7 +61,8 @@ static struct page *dummy_page;
 static struct scatterlist dummy_sg;
 
 static void cmnd_remove_data_wait_hash(struct iscsi_cmnd *cmnd);
-static void iscsi_send_task_mgmt_resp(struct iscsi_cmnd *req, int status);
+static void iscsi_send_task_mgmt_resp(struct iscsi_cmnd *req, int status,
+	bool dropped);
 static void iscsi_check_send_delayed_tm_resp(struct iscsi_session *sess);
 static void req_cmnd_release(struct iscsi_cmnd *req);
 static int cmnd_insert_data_wait_hash(struct iscsi_cmnd *cmnd);
@@ -2660,7 +2661,7 @@ static void execute_task_management(struct iscsi_cmnd *req)
 
 reject:
 	if (rc != 0)
-		iscsi_send_task_mgmt_resp(req, status);
+		iscsi_send_task_mgmt_resp(req, status, false);
 
 	return;
 }
@@ -3488,7 +3489,8 @@ out:
 	return;
 }
 
-static void iscsi_send_task_mgmt_resp(struct iscsi_cmnd *req, int status)
+static void iscsi_send_task_mgmt_resp(struct iscsi_cmnd *req, int status,
+	bool drop)
 {
 	struct iscsi_cmnd *rsp;
 	struct iscsi_task_mgt_hdr *req_hdr =
@@ -3500,7 +3502,26 @@ static void iscsi_send_task_mgmt_resp(struct iscsi_cmnd *req, int status)
 	TRACE_ENTRY();
 
 	TRACE_MGMT_DBG("TM req %p finished", req);
-	TRACE(TRACE_MGMT, "iSCSI TM fn %d finished, status %d", fn, status);
+	TRACE(TRACE_MGMT, "iSCSI TM fn %d finished, status %d, dropped %d",
+		fn, status, drop);
+
+	if (drop) {
+		spin_lock(&sess->sn_lock);
+		sess->tm_active--;
+		spin_unlock(&sess->sn_lock);
+		if (fn == ISCSI_FUNCTION_TARGET_COLD_RESET) {
+			struct iscsi_target *target = req->conn->session->target;
+
+			PRINT_INFO("Closing all connections for target %x at "
+				"COLD RESET from initiator %s", target->tid,
+				req->conn->session->initiator_name);
+
+			mutex_lock(&target->target_mutex);
+			target_del_all_sess(target, 0);
+			mutex_unlock(&target->target_mutex);
+		}
+		goto out_release;
+	}
 
 	rsp = iscsi_alloc_rsp(req);
 	rsp_hdr = (struct iscsi_task_rsp_hdr *)&rsp->pdu.bhs;
@@ -3569,8 +3590,7 @@ static void iscsi_task_mgmt_fn_done(struct scst_mgmt_cmd *scst_mcmd)
 	int fn = scst_mgmt_cmd_get_fn(scst_mcmd);
 	struct iscsi_cmnd *req = (struct iscsi_cmnd *)
 				scst_mgmt_cmd_get_tgt_priv(scst_mcmd);
-	int status =
-		iscsi_get_mgmt_response(scst_mgmt_cmd_get_status(scst_mcmd));
+	int status = iscsi_get_mgmt_response(scst_mgmt_cmd_get_status(scst_mcmd));
 
 	if ((status == ISCSI_RESPONSE_UNKNOWN_TASK) &&
 	    (fn == SCST_ABORT_TASK)) {
@@ -3592,7 +3612,7 @@ static void iscsi_task_mgmt_fn_done(struct scst_mgmt_cmd *scst_mcmd)
 		sBUG_ON(1);
 		break;
 	default:
-		iscsi_send_task_mgmt_resp(req, status);
+		iscsi_send_task_mgmt_resp(req, status, scst_mgmt_cmd_dropped(scst_mcmd));
 		scst_mgmt_cmd_set_tgt_priv(scst_mcmd, NULL);
 		break;
 	}

scst/README

@@ -603,16 +603,19 @@ Every target should have at least the following entries:
     * 2 - immediately abort all coming commands and drop all coming TM
       commands
 
-    * 3 - immediately abort all coming data transfer commands. This is
-      the most evil mode, because it is not too well handled by many
-      initiator OS'es, including Linux, so they may never recover from
-      it.
+    * 3 - immediately abort all coming data transfer commands.
 
     * 4 - immediately abort all coming data transfer commands and drop all
       coming TM commands
 
-   CAUTION! With some target drivers modes 2 and 4 can cause internal
-   resources leaks, so don't abuse those options!
+   Modes 3 and 4 are the most evil ones, because they are not too well
+   handled by many initiator OS'es, including Linux, so they may never
+   recover from it.
+
+   Note, dropping TM commands, i.e. not sending response on them,
+   implemented not for all target drivers. If it's implemented for your
+   particular target driver or not, you can find out by checking traces
+   or the target driver's source code.
 
  - cpu_mask - defines CPU affinity mask for threads serving this target.
    For threads serving LUNs it is used only for devices with

scst/README_in-tree

@@ -465,16 +465,19 @@ Every target should have at least the following entries:
     * 2 - immediately abort all coming commands and drop all coming TM
       commands
 
-    * 3 - immediately abort all coming data transfer commands. This is
-      the most evil mode, because it is not too well handled by many
-      initiator OS'es, including Linux, so they may never recover from
-      it.
+    * 3 - immediately abort all coming data transfer commands.
 
     * 4 - immediately abort all coming data transfer commands and drop all
       coming TM commands
 
-   CAUTION! With some target drivers modes 2 and 4 can cause internal
-   resources leaks, so don't abuse those options!
+   Modes 3 and 4 are the most evil ones, because they are not too well
+   handled by many initiator OS'es, including Linux, so they may never
+   recover from it.
+
+   Note, dropping TM commands, i.e. not sending response on them,
+   implemented not for all target drivers. If it's implemented for your
+   particular target driver or not, you can find out by checking traces
+   or the target driver's source code.
 
  - cpu_mask - defines CPU affinity mask for threads serving this target.
    For threads serving LUNs it is used only for devices with

scst/include/scst.h

@@ -2289,6 +2289,7 @@ struct scst_mgmt_cmd {
 	unsigned int cmd_sn_set:1;	/* set, if cmd_sn field is valid */
 	/* Set if dev handler's task_mgmt_fn_received was called */
 	unsigned int task_mgmt_fn_received_called:1;
+	unsigned int mcmd_dropped:1; /* set if mcmd was dropped */
 
 	/*
 	 * Number of commands to finish before sending response,
@@ -3717,12 +3718,6 @@ static inline int scst_mgmt_cmd_get_status(struct scst_mgmt_cmd *mcmd)
 	return mcmd->status;
 }
 
-/* Returns mgmt cmd's TM fn */
-static inline int scst_mgmt_cmd_get_fn(struct scst_mgmt_cmd *mcmd)
-{
-	return mcmd->fn;
-}
-
 static inline void scst_mgmt_cmd_set_status(struct scst_mgmt_cmd *mcmd,
 	int status)
 {
@@ -3732,6 +3727,18 @@ static inline void scst_mgmt_cmd_set_status(struct scst_mgmt_cmd *mcmd,
 		mcmd->status = status;
 }
 
+/* Returns mgmt cmd's TM fn */
+static inline int scst_mgmt_cmd_get_fn(struct scst_mgmt_cmd *mcmd)
+{
+	return mcmd->fn;
+}
+
+/* Returns true if mgmt cmd should be dropped, i.e. response not sent */
+static inline bool scst_mgmt_cmd_dropped(struct scst_mgmt_cmd *mcmd)
+{
+	return mcmd->mcmd_dropped;
+}
+
 /*
  * Called by dev handler's task_mgmt_fn_*() to notify SCST core that mcmd
  * is going to complete asynchronously.

scst/src/scst_targ.c

@@ -5497,13 +5497,11 @@ static int scst_mgmt_cmd_init(struct scst_mgmt_cmd *mcmd)
 	TRACE_ENTRY();
 
 	t = mcmd->sess->acg->acg_black_hole_type;
-
 	if (unlikely((t == SCST_ACG_BLACK_HOLE_ALL) ||
 		     (t == SCST_ACG_BLACK_HOLE_DATA_MCMD))) {
 		TRACE_MGMT_DBG("Dropping mcmd %p (fn %d, initiator %s)", mcmd,
 			mcmd->fn, mcmd->sess->initiator_name);
-		mcmd->state = SCST_MCMD_STATE_FINISHED;
-		goto out;
+		mcmd->mcmd_dropped = 1;
 	}
 
 	switch (mcmd->fn) {