[dm-devel] [Patch] Target message ioctl

[Alasdair G Kergon]

[I'll check the corresponding dmsetup changes into CVS next.]

Add message-passing ioctl for multipath configuration etc.

zero_message is a trivial implementation for easy testing.

Probably worth splitting string into words before passing to target
(i.e. pass in argc, argv instead of message)
or else exporting some version of split_args function.

--- diff/drivers/md/dm-ioctl.c	2004-06-01 19:59:25.000000000 +0100
+++ source/drivers/md/dm-ioctl.c	2004-06-08 20:53:24.000000000 +0100
@@ -1097,6 +1097,59 @@
 	return r;
 }
 
+/*
+ * Pass a message to the target that's at the supplied device offset.
+ */
+static int target_message(struct dm_ioctl *param, size_t param_size)
+{
+	int r;
+	struct mapped_device *md;
+	struct dm_table *table;
+	struct dm_target *ti;
+	struct dm_target_msg *tmsg = (void *) param + param->data_start;
+
+	md = find_device(param);
+	if (!md)
+		return -ENXIO;
+
+	r = __dev_status(md, param);
+	if (r)
+		goto out;
+
+	if (tmsg < (struct dm_target_msg *) (param + 1) ||
+	    invalid_str(tmsg->message, (void *) param + param_size)) {
+		DMWARN("Invalid target message parameters.");
+		r = -EINVAL;
+		goto out;
+	}
+
+	table = dm_get_table(md);
+	if (!table)
+		goto out;
+
+	if (tmsg->sector >= dm_table_get_size(table)) {
+		DMWARN("Target message sector outside device.");
+		r = -EINVAL;
+		goto out_table;
+	}
+
+	ti = dm_table_find_target(table, tmsg->sector);
+	if (ti->type->message)
+		r = ti->type->message(ti, tmsg->message);
+	else {
+		DMWARN("Target type does not support messages");
+		r = -EINVAL;
+	}
+
+ out_table:
+	dm_table_put(table);
+
+ out:
+	param->data_size = 0;
+	dm_put(md);
+	return r;
+}
+
 /*-----------------------------------------------------------------
  * Implementation of open/close/ioctl on the special char
  * device.
@@ -1123,7 +1176,9 @@
 		{DM_TABLE_DEPS_CMD, table_deps},
 		{DM_TABLE_STATUS_CMD, table_status},
 
-		{DM_LIST_VERSIONS_CMD, list_versions}
+		{DM_LIST_VERSIONS_CMD, list_versions},
+
+		{DM_TARGET_MSG_CMD, target_message}
 	};
 
 	return (cmd >= ARRAY_SIZE(_ioctls)) ? NULL : _ioctls[cmd].fn;
--- diff/drivers/md/dm-zero.c	2004-06-07 14:17:05.000000000 +0100
+++ source/drivers/md/dm-zero.c	2004-06-08 20:53:25.000000000 +0100
@@ -64,11 +64,18 @@
 	return 0;
 }
 
+static int zero_message(struct dm_target *ti, char *message)
+{
+	DMERR("dm-zero message received: %s", message);
+	return 0;
+}
+
 static struct target_type zero_target = {
 	.name   = "zero",
 	.module = THIS_MODULE,
 	.ctr    = zero_ctr,
 	.map    = zero_map,
+	.message = zero_message,
 };
 
 int __init dm_zero_init(void)
--- diff/include/linux/device-mapper.h	2004-06-07 14:24:46.000000000 +0100
+++ source/include/linux/device-mapper.h	2004-06-08 20:53:25.000000000 +0100
@@ -59,6 +59,8 @@
 typedef int (*dm_status_fn) (struct dm_target *ti, status_type_t status_type,
 			     char *result, unsigned int maxlen);
 
+typedef int (*dm_message_fn) (struct dm_target *ti, char *message);
+
 void dm_error(const char *message);
 
 /*
@@ -84,6 +86,7 @@
 	dm_suspend_fn suspend;
 	dm_resume_fn resume;
 	dm_status_fn status;
+	dm_message_fn message;
 };
 
 struct io_restrictions {
--- diff/include/linux/dm-ioctl.h	2004-05-19 22:12:59.000000000 +0100
+++ source/include/linux/dm-ioctl.h	2004-06-08 20:53:25.000000000 +0100
@@ -76,6 +76,9 @@
  *
  * DM_TABLE_STATUS:
  * Return the targets status for the 'active' table.
+ *
+ * DM_TARGET_MSG:
+ * Pass a message string to the target at a specific offset of a device.
  */
 
 /*
@@ -179,6 +182,15 @@
 };
 
 /*
+ * Used to pass message to a target
+ */
+struct dm_target_msg {
+	uint64_t sector;	/* Device sector */
+
+	char message[0];
+};
+
+/*
  * If you change this make sure you make the corresponding change
  * to dm-ioctl.c:lookup_ioctl()
  */
@@ -204,6 +216,7 @@
 
 	/* Added later */
 	DM_LIST_VERSIONS_CMD,
+	DM_TARGET_MSG_CMD,
 };
 
 /*
@@ -232,6 +245,7 @@
 #define DM_TABLE_DEPS_32    _IOWR(DM_IOCTL, DM_TABLE_DEPS_CMD, ioctl_struct)
 #define DM_TABLE_STATUS_32  _IOWR(DM_IOCTL, DM_TABLE_STATUS_CMD, ioctl_struct)
 #define DM_LIST_VERSIONS_32 _IOWR(DM_IOCTL, DM_LIST_VERSIONS_CMD, ioctl_struct)
+#define DM_TARGET_MSG_32    _IOWR(DM_IOCTL, DM_TARGET_MSG_CMD, ioctl_struct)
 #endif
 
 #define DM_IOCTL 0xfd
@@ -254,10 +268,12 @@
 
 #define DM_LIST_VERSIONS _IOWR(DM_IOCTL, DM_LIST_VERSIONS_CMD, struct dm_ioctl)
 
+#define DM_TARGET_MSG	 _IOWR(DM_IOCTL, DM_TARGET_MSG_CMD, struct dm_ioctl)
+
 #define DM_VERSION_MAJOR	4
-#define DM_VERSION_MINOR	1
+#define DM_VERSION_MINOR	2
 #define DM_VERSION_PATCHLEVEL	0
-#define DM_VERSION_EXTRA	"-ioctl (2003-12-10)"
+#define DM_VERSION_EXTRA	"-ioctl (2004-06-08)"
 
 /* Status bits */
 #define DM_READONLY_FLAG	(1 << 0) /* In/Out */