scst: Add user space control for suspend/resume activities

Useful to speed up mass management



git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@6693 d57e44dd-8a1f-0410-8b47-8ef2f437770f

scst/README

@@ -441,6 +441,19 @@ following entries:
    have different IDs and SNs. For instance, VDISK dev handler uses this
    ID to generate T10 vendor specific identifier and SN of the devices.
 
+ - suspend - globally suspends or releases all SCSI activities on all
+   devices. Useful for mass management, like adding or deleting LUNs.
+   Writing to it value v:
+
+	* v > 0 - suspends activities, but waits no more, than v seconds
+
+	* v = 0 - suspends activities, waits indefinitely
+
+	* V < 0 - releases activities.
+
+   Reading from this attribute returns number of previous suspend
+   requests.
+
  - threads - allows to read and set number of global SCST I/O threads.
    Those threads used with async. dev handlers, for instance, vdisk
    BLOCKIO or NULLIO.

scst/README_in-tree

@@ -305,6 +305,19 @@ following entries:
    have different IDs and SNs. For instance, VDISK dev handler uses this
    ID to generate T10 vendor specific identifier and SN of the devices.
 
+ - suspend - globally suspends or releases all SCSI activities on all
+   devices. Useful for mass management, like adding or deleting LUNs.
+   Writing to it value v:
+
+	* v > 0 - suspends activities, but waits no more, than v seconds
+
+	* v = 0 - suspends activities, waits indefinitely
+
+	* V < 0 - releases activities.
+
+   Reading from this attribute returns number of previous suspend
+   requests.
+
  - threads - allows to read and set number of global SCST I/O threads.
    Those threads used with async. dev handlers, for instance, vdisk
    BLOCKIO or NULLIO.

scst/src/scst_main.c

@@ -1057,6 +1057,11 @@ static void __scst_resume_activity(void)
 
 	TRACE_ENTRY();
 
+	if (suspend_count == 0) {
+		PRINT_WARNING("Resume without suspend");
+		goto out;
+	}
+
 	suspend_count--;
 	TRACE_MGMT_DBG("suspend_count %d left", suspend_count);
 	if (suspend_count > 0)
@@ -1117,6 +1122,11 @@ void scst_resume_activity(void)
 }
 EXPORT_SYMBOL_GPL(scst_resume_activity);
 
+int scst_get_suspend_count(void)
+{
+	return suspend_count;
+}
+
 static int scst_register_device(struct scsi_device *scsidp)
 {
 	int res;

scst/src/scst_priv.h

@@ -729,6 +729,8 @@ void scst_ext_unblock_dev(struct scst_device *dev, bool stpg);
 void __scst_ext_blocking_done(struct scst_device *dev);
 void scst_ext_blocking_done(struct scst_device *dev);
 
+int scst_get_suspend_count(void);
+
 /*
  * Increases global SCST ref counters which prevent from entering into suspended
  * activities stage, so protects from any global management operations.

scst/src/scst_sysfs.c

@@ -7056,6 +7056,55 @@ static struct kobj_attribute scst_max_tasklet_cmd_attr =
 	__ATTR(max_tasklet_cmd, S_IRUGO | S_IWUSR, scst_max_tasklet_cmd_show,
 	       scst_max_tasklet_cmd_store);
 
+static ssize_t scst_suspend_show(struct kobject *kobj,
+				 struct kobj_attribute *attr, char *buf)
+{
+	int count;
+
+	TRACE_ENTRY();
+
+	count = sprintf(buf, "%d\n", scst_get_suspend_count());
+
+	TRACE_EXIT();
+	return count;
+}
+
+static ssize_t scst_suspend_store(struct kobject *kobj,
+	struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	int res;
+	long val;
+
+	TRACE_ENTRY();
+
+	res = kstrtol(buf, 0, &val);
+	if (res != 0) {
+		PRINT_ERROR("kstrtoul() for %s failed: %d ", buf, res);
+		goto out;
+	}
+
+	if (val >= 0) {
+		PRINT_INFO("SYSFS: suspending activities (timeout %ld)...", val);
+		res = scst_suspend_activity(val*HZ);
+		if (res == 0)
+			PRINT_INFO("sysfs suspending done");
+	} else {
+		PRINT_INFO("SYSFS: resuming activities");
+		scst_resume_activity();
+	}
+
+	if (res == 0)
+		res = count;
+
+out:
+	TRACE_EXIT_RES(res);
+	return res;
+}
+
+static struct kobj_attribute scst_suspend_attr =
+	__ATTR(suspend, S_IRUGO | S_IWUSR, scst_suspend_show,
+	       scst_suspend_store);
+
 #if defined(CONFIG_SCST_DEBUG) || defined(CONFIG_SCST_TRACING)
 
 static ssize_t scst_main_trace_level_show(struct kobject *kobj,
@@ -7281,6 +7330,7 @@ static struct attribute *scst_sysfs_root_default_attrs[] = {
 	&scst_threads_attr.attr,
 	&scst_setup_id_attr.attr,
 	&scst_max_tasklet_cmd_attr.attr,
+	&scst_suspend_attr.attr,
 #if defined(CONFIG_SCST_DEBUG) || defined(CONFIG_SCST_TRACING)
 	&scst_main_trace_level_attr.attr,
 #endif