Restore the on_alua_state_change_*() callback functions

Apparently the bind_alua_state functionality is being used. Hence restore
the on_alua_state_change_*() callback functions. The changes compared to
the previous implementation are:
* Only invoke the on_alua_state_change_*() callback functions if the state
  of a local target port group is being modified.
* Report information about ALUA callback activity with PRINT_INFO() instead
  of TRACE_MGMT_DBG().

This patch reverts commit 29548a4ad7 ("scst: Remove the
on_alua_state_change_*() callback functions").


git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@9120 d57e44dd-8a1f-0410-8b47-8ef2f437770f

scst/include/scst.h

@@ -1401,6 +1401,34 @@ struct scst_dev_type {
 	void (*ext_copy_remap)(struct scst_cmd *cmd,
 		struct scst_ext_copy_seg_descr *descr);
 
+	/*
+	 * Called to notify dev handler that a ALUA state change is about to
+	 * be started. Can be used to close open file handlers, which might
+	 * prevent the state switch.
+	 *
+	 * Called under scst_dg_mutex and no activities on the dev handler level
+	 * (for implicit ALUA case supposed to be done by the user space via
+	 * "block" sysfs attribute as described in the README).
+	 *
+	 * OPTIONAL
+	 */
+	void (*on_alua_state_change_start)(struct scst_device *dev,
+		enum scst_tg_state old_state, enum scst_tg_state new_state);
+
+	/*
+	 * Called to notify dev handler that a ALUA state change is about to
+	 * be finished. Can be used to (re)open file handlers closed in
+	 * on_alua_state_change_start().
+	 *
+	 * Called under scst_dg_mutex and no activities on the dev handler level
+	 * (for implicit ALUA case supposed to be done by the user space via
+	 * "block" sysfs attribute as described in the README).
+	 *
+	 * OPTIONAL
+	 */
+	void (*on_alua_state_change_finish)(struct scst_device *dev,
+		enum scst_tg_state old_state, enum scst_tg_state new_state);
+
 	/*
 	 * Called to notify dev handler that a task management command received
 	 *

scst/src/dev_handlers/scst_vdisk.c

@@ -6441,6 +6441,86 @@ static enum compl_status_e nullio_exec_verify(struct vdisk_cmd_params *p)
 	return CMD_SUCCEEDED;
 }
 
+static void blockio_on_alua_state_change_start(struct scst_device *dev,
+	enum scst_tg_state old_state, enum scst_tg_state new_state)
+{
+	struct scst_vdisk_dev *virt_dev = dev->dh_priv;
+	const bool close = virt_dev->dev_active &&
+		new_state != SCST_TG_STATE_OPTIMIZED &&
+		new_state != SCST_TG_STATE_NONOPTIMIZED;
+
+	TRACE_ENTRY();
+
+	/* No other fd activity may happen concurrently with this function. */
+	lockdep_assert_alua_lock_held();
+
+	if (!virt_dev->bind_alua_state)
+		return;
+
+	PRINT_INFO("dev %s: ALUA state change from %s to %s started,%s closing FD",
+		   dev->virt_name, scst_alua_state_name(old_state),
+		   scst_alua_state_name(new_state), close ? "" : " not");
+
+	if (!close)
+		return;
+
+	virt_dev->dev_active = 0;
+
+	vdisk_close_fd(virt_dev);
+
+	TRACE_EXIT();
+	return;
+}
+
+static void blockio_on_alua_state_change_finish(struct scst_device *dev,
+	enum scst_tg_state old_state, enum scst_tg_state new_state)
+{
+	struct scst_vdisk_dev *virt_dev = dev->dh_priv;
+	const bool open = !virt_dev->dev_active &&
+		(new_state == SCST_TG_STATE_OPTIMIZED ||
+		 new_state == SCST_TG_STATE_NONOPTIMIZED);
+	int rc = 0;
+
+	TRACE_ENTRY();
+
+	/* No other fd activity may happen concurrently with this function. */
+	lockdep_assert_alua_lock_held();
+
+	if (!virt_dev->bind_alua_state)
+		return;
+
+	PRINT_INFO("dev %s: ALUA state change from %s to %s finished,%s reopening FD",
+		   dev->virt_name, scst_alua_state_name(old_state),
+		   scst_alua_state_name(new_state), open ? "" : " not");
+
+	if (!open)
+		return;
+
+	virt_dev->dev_active = 1;
+
+	/*
+	 * only reopen fd if tgt_dev_cnt is not zero, otherwise we will
+	 * leak reference.
+	 */
+	if (virt_dev->tgt_dev_cnt)
+		rc = vdisk_open_fd(virt_dev, dev->dev_rd_only);
+
+	if (rc == 0) {
+		if (virt_dev->reexam_pending) {
+			rc = vdisk_reexamine(virt_dev);
+			WARN_ON(rc != 0);
+			virt_dev->reexam_pending = 0;
+		}
+	} else {
+		PRINT_ERROR("dev %s: opening after ALUA state change to %s failed",
+			    dev->virt_name,
+			    scst_alua_state_name(new_state));
+	}
+
+	TRACE_EXIT();
+	return;
+}
+
 static void vdisk_task_mgmt_fn_done(struct scst_mgmt_cmd *mcmd,
 	struct scst_tgt_dev *tgt_dev)
 {
@@ -9316,7 +9396,10 @@ static int vdev_sysfs_process_active_store(
 	res = mutex_lock_interruptible(&scst_mutex);
 	if (res)
 		goto resume;
-	/* To do: verify whether this call is still necessary. */
+	/*
+	 * This is used to serialize against the *_on_alua_state_change_*()
+	 * calls in scst_tg.c
+	 */
 	scst_alua_lock();
 
 	/*
@@ -9798,6 +9881,8 @@ static struct scst_dev_type vdisk_blk_devtype = {
 	.detach_tgt =		vdisk_detach_tgt,
 	.parse =		non_fileio_parse,
 	.exec =			blockio_exec,
+	.on_alua_state_change_start = blockio_on_alua_state_change_start,
+	.on_alua_state_change_finish = blockio_on_alua_state_change_finish,
 	.task_mgmt_fn_done =	vdisk_task_mgmt_fn_done,
 	.get_supported_opcodes = vdisk_get_supported_opcodes,
 	.devt_priv =		(void *)blockio_ops,

scst/src/scst_tg.c

@@ -964,18 +964,26 @@ out_fail:
 }
 
 /*
- * __scst_tgt_set_state - Update the ALUA filter of a LUN
+ * __scst_tgt_set_state - Update the ALUA filter of a LUN and invoke callbacks
  * @tg: ALUA target group of which the state is changing.
  * @tgt_dev: LUN to be updated.
  * @state: new ALUA state.
+ * @invoke_callbacks: Whether or not to invoke the on_alua_state_changed_*
+ *	callback functions.
  */
 static void __scst_tgt_set_state(struct scst_target_group *tg,
-	struct scst_tgt_dev *tgt_dev, enum scst_tg_state state)
+	struct scst_tgt_dev *tgt_dev, enum scst_tg_state state,
+	bool invoke_callbacks)
 {
 	bool gen_ua = state != SCST_TG_STATE_TRANSITIONING;
 	struct scst_tgt *tgt = tgt_dev->sess->tgt;
+	enum scst_tg_state old_state = tg->state;
+	struct scst_device *dev = tgt_dev->dev;
 	struct scst_dev_group *dg = tg->dg;
 
+	if (invoke_callbacks && dev->handler->on_alua_state_change_start)
+		dev->handler->on_alua_state_change_start(dev, old_state,
+							 state);
 	/*
 	 * If the ALUA state transition is caused by an STPG command and if
 	 * the STPG command has been received through the target port of which
@@ -985,6 +993,9 @@ static void __scst_tgt_set_state(struct scst_target_group *tg,
 	    tid_equal(dg->stpg_transport_id, tgt_dev->sess->transport_id))
 		gen_ua = false;
 	scst_tg_change_tgt_dev_state(tgt_dev, state, gen_ua);
+	if (invoke_callbacks && dev->handler->on_alua_state_change_finish)
+		dev->handler->on_alua_state_change_finish(dev, old_state,
+							  state);
 }
 
 /*
@@ -1000,6 +1011,7 @@ static void __scst_tg_set_state(struct scst_target_group *tg,
 	struct scst_tgt_dev *tgt_dev;
 	struct scst_tg_tgt *tg_tgt;
 	struct scst_tgt *tgt;
+	bool invoke_callbacks;
 
 	sBUG_ON(state >= ARRAY_SIZE(scst_alua_filter));
 	lockdep_assert_held(&scst_dg_mutex);
@@ -1007,23 +1019,25 @@ static void __scst_tg_set_state(struct scst_target_group *tg,
 	if (tg->state == state)
 		return;
 
-	tg->state = state;
-
 	list_for_each_entry(dg_dev, &tg->dg->dev_list, entry) {
+		invoke_callbacks = true;
 		dev = dg_dev->dev;
 		list_for_each_entry(tgt_dev, &dev->dev_tgt_dev_list,
 				    dev_tgt_dev_list_entry) {
 			tgt = tgt_dev->sess->tgt;
 			list_for_each_entry(tg_tgt, &tg->tgt_list, entry) {
 				if (tg_tgt->tgt == tgt) {
-					__scst_tgt_set_state(tg, tgt_dev,
-							     state);
+					__scst_tgt_set_state(tg, tgt_dev, state,
+							     invoke_callbacks);
+					invoke_callbacks = false;
 					break;
 				}
 			}
 		}
 	}
 
+	tg->state = state;
+
 	scst_check_alua_invariant();
 
 	PRINT_INFO("Changed ALUA state of %s/%s into %s", tg->dg->name,