1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2001 Sistina Software (UK) Limited 4 * 5 * This file is released under the GPL. 6 */ 7 8 #include "dm-core.h" 9 10 #include <linux/module.h> 11 #include <linux/init.h> 12 #include <linux/kmod.h> 13 #include <linux/bio.h> 14 #include <linux/dax.h> 15 16 #define DM_MSG_PREFIX "target" 17 18 static LIST_HEAD(_targets); 19 static DECLARE_RWSEM(_lock); 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 DMERR("%s: '%s' target already registered", 90 __func__, tt->name); 91 rv = -EEXIST; 92 } else { 93 list_add(&tt->list, &_targets); 94 } 95 up_write(&_lock); 96 97 return rv; 98 } 99 EXPORT_SYMBOL(dm_register_target); 100 101 void dm_unregister_target(struct target_type *tt) 102 { 103 down_write(&_lock); 104 if (!__find_target_type(tt->name)) { 105 DMCRIT("Unregistering unrecognised target: %s", tt->name); 106 BUG(); 107 } 108 109 list_del(&tt->list); 110 111 up_write(&_lock); 112 } 113 EXPORT_SYMBOL(dm_unregister_target); 114 115 /* 116 * io-err: always fails an io, useful for bringing 117 * up LVs that have holes in them. 118 */ 119 static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args) 120 { 121 /* 122 * Return error for discards instead of -EOPNOTSUPP 123 */ 124 tt->num_discard_bios = 1; 125 tt->discards_supported = true; 126 127 return 0; 128 } 129 130 static void io_err_dtr(struct dm_target *tt) 131 { 132 /* empty */ 133 } 134 135 static int io_err_map(struct dm_target *tt, struct bio *bio) 136 { 137 return DM_MAPIO_KILL; 138 } 139 140 static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq, 141 union map_info *map_context, 142 struct request **clone) 143 { 144 return DM_MAPIO_KILL; 145 } 146 147 static void io_err_release_clone_rq(struct request *clone, 148 union map_info *map_context) 149 { 150 } 151 152 static void io_err_io_hints(struct dm_target *ti, struct queue_limits *limits) 153 { 154 limits->max_discard_sectors = UINT_MAX; 155 limits->max_hw_discard_sectors = UINT_MAX; 156 limits->discard_granularity = 512; 157 } 158 159 static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff, 160 long nr_pages, enum dax_access_mode mode, void **kaddr, 161 pfn_t *pfn) 162 { 163 return -EIO; 164 } 165 166 static struct target_type error_target = { 167 .name = "error", 168 .version = {1, 6, 0}, 169 .features = DM_TARGET_WILDCARD, 170 .ctr = io_err_ctr, 171 .dtr = io_err_dtr, 172 .map = io_err_map, 173 .clone_and_map_rq = io_err_clone_and_map_rq, 174 .release_clone_rq = io_err_release_clone_rq, 175 .io_hints = io_err_io_hints, 176 .direct_access = io_err_dax_direct_access, 177 }; 178 179 int __init dm_target_init(void) 180 { 181 return dm_register_target(&error_target); 182 } 183 184 void dm_target_exit(void) 185 { 186 dm_unregister_target(&error_target); 187 } 188