drivers/md/dm-target.c

   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 struct tt_internal {
  18         struct target_type tt;
  19
  20         struct list_head list;
  21         long use;
  22 };
  23
  24 static LIST_HEAD(_targets);
  25 static DECLARE_RWSEM(_lock);
  26
  27 #define DM_MOD_NAME_SIZE 32
  28
  29 static inline struct tt_internal *__find_target_type(const char *name)
  30 {
  31         struct tt_internal *ti;
  32
  33         list_for_each_entry (ti, &_targets, list)
  34                 if (!strcmp(name, ti->tt.name))
  35                         return ti;
  36
  37         return NULL;
  38 }
  39
  40 static struct tt_internal *get_target_type(const char *name)
  41 {
  42         struct tt_internal *ti;
  43
  44         down_read(&_lock);
  45
  46         ti = __find_target_type(name);
  47         if (ti) {
  48                 if ((ti->use == 0) && !try_module_get(ti->tt.module))
  49                         ti = NULL;
  50                 else
  51                         ti->use++;
  52         }
  53
  54         up_read(&_lock);
  55         return ti;
  56 }
  57
  58 static void load_module(const char *name)
  59 {
  60         request_module("dm-%s", name);
  61 }
  62
  63 struct target_type *dm_get_target_type(const char *name)
  64 {
  65         struct tt_internal *ti = get_target_type(name);
  66
  67         if (!ti) {
  68                 load_module(name);
  69                 ti = get_target_type(name);
  70         }
  71
  72         return ti ? &ti->tt : NULL;
  73 }
  74
  75 void dm_put_target_type(struct target_type *t)
  76 {
  77         struct tt_internal *ti = (struct tt_internal *) t;
  78
  79         down_read(&_lock);
  80         if (--ti->use == 0)
  81                 module_put(ti->tt.module);
  82
  83         BUG_ON(ti->use < 0);
  84         up_read(&_lock);
  85
  86         return;
  87 }
  88
  89 static struct tt_internal *alloc_target(struct target_type *t)
  90 {
  91         struct tt_internal *ti = kzalloc(sizeof(*ti), GFP_KERNEL);
  92
  93         if (ti)
  94                 ti->tt = *t;
  95
  96         return ti;
  97 }
  98
  99
 100 int dm_target_iterate(void (*iter_func)(struct target_type *tt,
 101                                         void *param), void *param)
 102 {
 103         struct tt_internal *ti;
 104
 105         down_read(&_lock);
 106         list_for_each_entry (ti, &_targets, list)
 107                 iter_func(&ti->tt, param);
 108         up_read(&_lock);
 109
 110         return 0;
 111 }
 112
 113 int dm_register_target(struct target_type *t)
 114 {
 115         int rv = 0;
 116         struct tt_internal *ti = alloc_target(t);
 117
 118         if (!ti)
 119                 return -ENOMEM;
 120
 121         down_write(&_lock);
 122         if (__find_target_type(t->name))
 123                 rv = -EEXIST;
 124         else
 125                 list_add(&ti->list, &_targets);
 126
 127         up_write(&_lock);
 128         if (rv)
 129                 kfree(ti);
 130         return rv;
 131 }
 132
 133 void dm_unregister_target(struct target_type *t)
 134 {
 135         struct tt_internal *ti;
 136
 137         down_write(&_lock);
 138         if (!(ti = __find_target_type(t->name))) {
 139                 DMCRIT("Unregistering unrecognised target: %s", t->name);
 140                 BUG();
 141         }
 142
 143         if (ti->use) {
 144                 DMCRIT("Attempt to unregister target still in use: %s",
 145                        t->name);
 146                 BUG();
 147         }
 148
 149         list_del(&ti->list);
 150         kfree(ti);
 151
 152         up_write(&_lock);
 153 }
 154
 155 /*
 156  * io-err: always fails an io, useful for bringing
 157  * up LVs that have holes in them.
 158  */
 159 static int io_err_ctr(struct dm_target *ti, unsigned int argc, char **args)
 160 {
 161         return 0;
 162 }
 163
 164 static void io_err_dtr(struct dm_target *ti)
 165 {
 166         /* empty */
 167 }
 168
 169 static int io_err_map(struct dm_target *ti, struct bio *bio,
 170                       union map_info *map_context)
 171 {
 172         return -EIO;
 173 }
 174
 175 static struct target_type error_target = {
 176         .name = "error",
 177         .version = {1, 0, 1},
 178         .ctr  = io_err_ctr,
 179         .dtr  = io_err_dtr,
 180         .map  = io_err_map,
 181 };
 182
 183 int __init dm_target_init(void)
 184 {
 185         return dm_register_target(&error_target);
 186 }
 187
 188 void dm_target_exit(void)
 189 {
 190         dm_unregister_target(&error_target);
 191 }
 192
 193 EXPORT_SYMBOL(dm_register_target);
 194 EXPORT_SYMBOL(dm_unregister_target);