/* * 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> #define DM_MSG_PREFIX "target" static LIST_HEAD(_targets); static DECLARE_RWSEM(_lock); #define DM_MOD_NAME_SIZE 32 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 0; } static void io_err_dtr(struct dm_target *tt) { /* empty */ } static int io_err_map(struct dm_target *tt, 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) { dm_unregister_target(&error_target); } EXPORT_SYMBOL(dm_register_target); EXPORT_SYMBOL(dm_unregister_target);