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 14 #define DM_MSG_PREFIX "target" 15 16 static LIST_HEAD(_targets); 17 static DECLARE_RWSEM(_lock); 18 19 #define DM_MOD_NAME_SIZE 32 20 21 static inline struct target_type *__find_target_type(const char *name) 22 { 23 struct target_type *tt; 24 25 list_for_each_entry(tt, &_targets, list) 26 if (!strcmp(name, tt->name)) 27 return tt; 28 29 return NULL; 30 } 31 32 static struct target_type *get_target_type(const char *name) 33 { 34 struct target_type *tt; 35 36 down_read(&_lock); 37 38 tt = __find_target_type(name); 39 if (tt && !try_module_get(tt->module)) 40 tt = NULL; 41 42 up_read(&_lock); 43 return tt; 44 } 45 46 static void load_module(const char *name) 47 { 48 request_module("dm-%s", name); 49 } 50 51 struct target_type *dm_get_target_type(const char *name) 52 { 53 struct target_type *tt = get_target_type(name); 54 55 if (!tt) { 56 load_module(name); 57 tt = get_target_type(name); 58 } 59 60 return tt; 61 } 62 63 void dm_put_target_type(struct target_type *tt) 64 { 65 down_read(&_lock); 66 module_put(tt->module); 67 up_read(&_lock); 68 } 69 70 int dm_target_iterate(void (*iter_func)(struct target_type *tt, 71 void *param), void *param) 72 { 73 struct target_type *tt; 74 75 down_read(&_lock); 76 list_for_each_entry(tt, &_targets, list) 77 iter_func(tt, param); 78 up_read(&_lock); 79 80 return 0; 81 } 82 83 int dm_register_target(struct target_type *tt) 84 { 85 int rv = 0; 86 87 down_write(&_lock); 88 if (__find_target_type(tt->name)) 89 rv = -EEXIST; 90 else 91 list_add(&tt->list, &_targets); 92 93 up_write(&_lock); 94 return rv; 95 } 96 97 void dm_unregister_target(struct target_type *tt) 98 { 99 down_write(&_lock); 100 if (!__find_target_type(tt->name)) { 101 DMCRIT("Unregistering unrecognised target: %s", tt->name); 102 BUG(); 103 } 104 105 list_del(&tt->list); 106 107 up_write(&_lock); 108 } 109 110 /* 111 * io-err: always fails an io, useful for bringing 112 * up LVs that have holes in them. 113 */ 114 static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args) 115 { 116 /* 117 * Return error for discards instead of -EOPNOTSUPP 118 */ 119 tt->num_discard_requests = 1; 120 121 return 0; 122 } 123 124 static void io_err_dtr(struct dm_target *tt) 125 { 126 /* empty */ 127 } 128 129 static int io_err_map(struct dm_target *tt, struct bio *bio, 130 union map_info *map_context) 131 { 132 return -EIO; 133 } 134 135 static struct target_type error_target = { 136 .name = "error", 137 .version = {1, 0, 1}, 138 .ctr = io_err_ctr, 139 .dtr = io_err_dtr, 140 .map = io_err_map, 141 }; 142 143 int __init dm_target_init(void) 144 { 145 return dm_register_target(&error_target); 146 } 147 148 void dm_target_exit(void) 149 { 150 dm_unregister_target(&error_target); 151 } 152 153 EXPORT_SYMBOL(dm_register_target); 154 EXPORT_SYMBOL(dm_unregister_target); 155