1 files changed, 173 insertions, 0 deletions
diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
new file mode 100644
index 000000000..64dd0b34f
--- /dev/null
+++ b/drivers/md/dm-target.c
@@ -0,0 +1,173 @@
+/*
+ * Copyright (C) 2001 Sistina Software (UK) Limited
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-core.h"
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kmod.h>
+#include <linux/bio.h>
+
+#define DM_MSG_PREFIX "target"
+
+static LIST_HEAD(_targets);
+static DECLARE_RWSEM(_lock);
+
+static inline struct target_type *__find_target_type(const char *name)
+{
+	struct target_type *tt;
+
+	list_for_each_entry(tt, &_targets, list)
+		if (!strcmp(name, tt->name))
+			return tt;
+
+	return NULL;
+}
+
+static struct target_type *get_target_type(const char *name)
+{
+	struct target_type *tt;
+
+	down_read(&_lock);
+
+	tt = __find_target_type(name);
+	if (tt && !try_module_get(tt->module))
+		tt = NULL;
+
+	up_read(&_lock);
+	return tt;
+}
+
+static void load_module(const char *name)
+{
+	request_module("dm-%s", name);
+}
+
+struct target_type *dm_get_target_type(const char *name)
+{
+	struct target_type *tt = get_target_type(name);
+
+	if (!tt) {
+		load_module(name);
+		tt = get_target_type(name);
+	}
+
+	return tt;
+}
+
+void dm_put_target_type(struct target_type *tt)
+{
+	down_read(&_lock);
+	module_put(tt->module);
+	up_read(&_lock);
+}
+
+int dm_target_iterate(void (*iter_func)(struct target_type *tt,
+					void *param), void *param)
+{
+	struct target_type *tt;
+
+	down_read(&_lock);
+	list_for_each_entry(tt, &_targets, list)
+		iter_func(tt, param);
+	up_read(&_lock);
+
+	return 0;
+}
+
+int dm_register_target(struct target_type *tt)
+{
+	int rv = 0;
+
+	down_write(&_lock);
+	if (__find_target_type(tt->name))
+		rv = -EEXIST;
+	else
+		list_add(&tt->list, &_targets);
+
+	up_write(&_lock);
+	return rv;
+}
+
+void dm_unregister_target(struct target_type *tt)
+{
+	down_write(&_lock);
+	if (!__find_target_type(tt->name)) {
+		DMCRIT("Unregistering unrecognised target: %s", tt->name);
+		BUG();
+	}
+
+	list_del(&tt->list);
+
+	up_write(&_lock);
+}
+
+/*
+ * io-err: always fails an io, useful for bringing
+ * up LVs that have holes in them.
+ */
+static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args)
+{
+	/*
+	 * Return error for discards instead of -EOPNOTSUPP
+	 */
+	tt->num_discard_bios = 1;
+
+	return 0;
+}
+
+static void io_err_dtr(struct dm_target *tt)
+{
+	/* empty */
+}
+
+static int io_err_map(struct dm_target *tt, struct bio *bio)
+{
+	return DM_MAPIO_KILL;
+}
+
+static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,
+				   union map_info *map_context,
+				   struct request **clone)
+{
+	return DM_MAPIO_KILL;
+}
+
+static void io_err_release_clone_rq(struct request *clone,
+				    union map_info *map_context)
+{
+}
+
+static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
+		long nr_pages, void **kaddr, pfn_t *pfn)
+{
+	return -EIO;
+}
+
+static struct target_type error_target = {
+	.name = "error",
+	.version = {1, 5, 0},
+	.features = DM_TARGET_WILDCARD,
+	.ctr  = io_err_ctr,
+	.dtr  = io_err_dtr,
+	.map  = io_err_map,
+	.clone_and_map_rq = io_err_clone_and_map_rq,
+	.release_clone_rq = io_err_release_clone_rq,
+	.direct_access = io_err_dax_direct_access,
+};
+
+int __init dm_target_init(void)
+{
+	return dm_register_target(&error_target);
+}
+
+void dm_target_exit(void)
+{
+	dm_unregister_target(&error_target);
+}
+
+EXPORT_SYMBOL(dm_register_target);
+EXPORT_SYMBOL(dm_unregister_target);