1 /* 2 * Copyright (C) 2001 Sistina Software (UK) Limited 3 * 4 * This file is released under the GPL. 5 */ 6 7 #include "dm.h" 8 9 #include <linux/module.h> 10 #include <linux/init.h> 11 #include <linux/kmod.h> 12 #include <linux/bio.h> 13 #include <linux/slab.h> 14 15 #define DM_MSG_PREFIX "target" 16 17 static LIST_HEAD(_targets); 18 static DECLARE_RWSEM(_lock); 19 20 #define DM_MOD_NAME_SIZE 32 21 22 static inline struct target_type *__find_target_type(const char *name) 23 { 24 struct target_type *tt; 25 26 list_for_each_entry(tt, &_targets, list) 27 if (!strcmp(name, tt->name)) 28 return tt; 29 30 return NULL; 31 } 32 33 static struct target_type *get_target_type(const char *name) 34 { 35 struct target_type *tt; 36 37 down_read(&_lock); 38 39 tt = __find_target_type(name); 40 if (tt && !try_module_get(tt->module)) 41 tt = NULL; 42 43 up_read(&_lock); 44 return tt; 45 } 46 47 static void load_module(const char *name) 48 { 49 request_module("dm-%s", name); 50 } 51 52 struct target_type *dm_get_target_type(const char *name) 53 { 54 struct target_type *tt = get_target_type(name); 55 56 if (!tt) { 57 load_module(name); 58 tt = get_target_type(name); 59 } 60 61 return tt; 62 } 63 64 void dm_put_target_type(struct target_type *tt) 65 { 66 down_read(&_lock); 67 module_put(tt->module); 68 up_read(&_lock); 69 } 70 71 int dm_target_iterate(void (*iter_func)(struct target_type *tt, 72 void *param), void *param) 73 { 74 struct target_type *tt; 75 76 down_read(&_lock); 77 list_for_each_entry(tt, &_targets, list) 78 iter_func(tt, param); 79 up_read(&_lock); 80 81 return 0; 82 } 83 84 int dm_register_target(struct target_type *tt) 85 { 86 int rv = 0; 87 88 down_write(&_lock); 89 if (__find_target_type(tt->name)) 90 rv = -EEXIST; 91 else 92 list_add(&tt->list, &_targets); 93 94 up_write(&_lock); 95 return rv; 96 } 97 98 void dm_unregister_target(struct target_type *tt) 99 { 100 down_write(&_lock); 101 if (!__find_target_type(tt->name)) { 102 DMCRIT("Unregistering unrecognised target: %s", tt->name); 103 BUG(); 104 } 105 106 list_del(&tt->list); 107 108 up_write(&_lock); 109 } 110 111 /* 112 * io-err: always fails an io, useful for bringing 113 * up LVs that have holes in them. 114 */ 115 static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args) 116 { 117 return 0; 118 } 119 120 static void io_err_dtr(struct dm_target *tt) 121 { 122 /* empty */ 123 } 124 125 static int io_err_map(struct dm_target *tt, struct bio *bio, 126 union map_info *map_context) 127 { 128 return -EIO; 129 } 130 131 static struct target_type error_target = { 132 .name = "error", 133 .version = {1, 0, 1}, 134 .ctr = io_err_ctr, 135 .dtr = io_err_dtr, 136 .map = io_err_map, 137 }; 138 139 int __init dm_target_init(void) 140 { 141 return dm_register_target(&error_target); 142 } 143 144 void dm_target_exit(void) 145 { 146 dm_unregister_target(&error_target); 147 } 148 149 EXPORT_SYMBOL(dm_register_target); 150 EXPORT_SYMBOL(dm_unregister_target); 151