1 files changed, 196 insertions, 0 deletions
diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
new file mode 100644
index 00000000000..aecd9e0c261
--- /dev/null
+++ b/drivers/md/dm-target.c
@@ -0,0 +1,196 @@
+/*
+ * Copyright (C) 2001 Sistina Software (UK) Limited
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm.h"
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kmod.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+
+struct tt_internal {
+	struct target_type tt;
+
+	struct list_head list;
+	long use;
+};
+
+static LIST_HEAD(_targets);
+static DECLARE_RWSEM(_lock);
+
+#define DM_MOD_NAME_SIZE 32
+
+static inline struct tt_internal *__find_target_type(const char *name)
+{
+	struct tt_internal *ti;
+
+	list_for_each_entry (ti, &_targets, list)
+		if (!strcmp(name, ti->tt.name))
+			return ti;
+
+	return NULL;
+}
+
+static struct tt_internal *get_target_type(const char *name)
+{
+	struct tt_internal *ti;
+
+	down_read(&_lock);
+
+	ti = __find_target_type(name);
+	if (ti) {
+		if ((ti->use == 0) && !try_module_get(ti->tt.module))
+			ti = NULL;
+		else
+			ti->use++;
+	}
+
+	up_read(&_lock);
+	return ti;
+}
+
+static void load_module(const char *name)
+{
+	request_module("dm-%s", name);
+}
+
+struct target_type *dm_get_target_type(const char *name)
+{
+	struct tt_internal *ti = get_target_type(name);
+
+	if (!ti) {
+		load_module(name);
+		ti = get_target_type(name);
+	}
+
+	return ti ? &ti->tt : NULL;
+}
+
+void dm_put_target_type(struct target_type *t)
+{
+	struct tt_internal *ti = (struct tt_internal *) t;
+
+	down_read(&_lock);
+	if (--ti->use == 0)
+		module_put(ti->tt.module);
+
+	if (ti->use < 0)
+		BUG();
+	up_read(&_lock);
+
+	return;
+}
+
+static struct tt_internal *alloc_target(struct target_type *t)
+{
+	struct tt_internal *ti = kmalloc(sizeof(*ti), GFP_KERNEL);
+
+	if (ti) {
+		memset(ti, 0, sizeof(*ti));
+		ti->tt = *t;
+	}
+
+	return ti;
+}
+
+
+int dm_target_iterate(void (*iter_func)(struct target_type *tt,
+					void *param), void *param)
+{
+	struct tt_internal *ti;
+
+	down_read(&_lock);
+	list_for_each_entry (ti, &_targets, list)
+		iter_func(&ti->tt, param);
+	up_read(&_lock);
+
+	return 0;
+}
+
+int dm_register_target(struct target_type *t)
+{
+	int rv = 0;
+	struct tt_internal *ti = alloc_target(t);
+
+	if (!ti)
+		return -ENOMEM;
+
+	down_write(&_lock);
+	if (__find_target_type(t->name))
+		rv = -EEXIST;
+	else
+		list_add(&ti->list, &_targets);
+
+	up_write(&_lock);
+	if (rv)
+		kfree(ti);
+	return rv;
+}
+
+int dm_unregister_target(struct target_type *t)
+{
+	struct tt_internal *ti;
+
+	down_write(&_lock);
+	if (!(ti = __find_target_type(t->name))) {
+		up_write(&_lock);
+		return -EINVAL;
+	}
+
+	if (ti->use) {
+		up_write(&_lock);
+		return -ETXTBSY;
+	}
+
+	list_del(&ti->list);
+	kfree(ti);
+
+	up_write(&_lock);
+	return 0;
+}
+
+/*
+ * io-err: always fails an io, useful for bringing
+ * up LVs that have holes in them.
+ */
+static int io_err_ctr(struct dm_target *ti, unsigned int argc, char **args)
+{
+	return 0;
+}
+
+static void io_err_dtr(struct dm_target *ti)
+{
+	/* empty */
+}
+
+static int io_err_map(struct dm_target *ti, struct bio *bio,
+		      union map_info *map_context)
+{
+	return -EIO;
+}
+
+static struct target_type error_target = {
+	.name = "error",
+	.version = {1, 0, 1},
+	.ctr  = io_err_ctr,
+	.dtr  = io_err_dtr,
+	.map  = io_err_map,
+};
+
+int __init dm_target_init(void)
+{
+	return dm_register_target(&error_target);
+}
+
+void dm_target_exit(void)
+{
+	if (dm_unregister_target(&error_target))
+		DMWARN("error target unregistration failed");
+}
+
+EXPORT_SYMBOL(dm_register_target);
+EXPORT_SYMBOL(dm_unregister_target);