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 struct tt_internal {
  16         struct target_type tt;
  17
  18         struct list_head list;
  19         long use;
  20 };
  21
  22 static LIST_HEAD(_targets);
  23 static DECLARE_RWSEM(_lock);
  24
  25 #define DM_MOD_NAME_SIZE 32
  26
  27 static inline struct tt_internal *__find_target_type(const char *name)
  28 {
  29         struct tt_internal *ti;
  30
  31         list_for_each_entry (ti, &_targets, list)
  32                 if (!strcmp(name, ti->tt.name))
  33                         return ti;
  34
  35         return NULL;
  36 }
  37
  38 static struct tt_internal *get_target_type(const char *name)
  39 {
  40         struct tt_internal *ti;
  41
  42         down_read(&_lock);
  43
  44         ti = __find_target_type(name);
  45         if (ti) {
  46                 if ((ti->use == 0) && !try_module_get(ti->tt.module))
  47                         ti = NULL;
  48                 else
  49                         ti->use++;
  50         }
  51
  52         up_read(&_lock);
  53         return ti;
  54 }
  55
  56 static void load_module(const char *name)
  57 {
  58         request_module("dm-%s", name);
  59 }
  60
  61 struct target_type *dm_get_target_type(const char *name)
  62 {
  63         struct tt_internal *ti = get_target_type(name);
  64
  65         if (!ti) {
  66                 load_module(name);
  67                 ti = get_target_type(name);
  68         }
  69
  70         return ti ? &ti->tt : NULL;
  71 }
  72
  73 void dm_put_target_type(struct target_type *t)
  74 {
  75         struct tt_internal *ti = (struct tt_internal *) t;
  76
  77         down_read(&_lock);
  78         if (--ti->use == 0)
  79                 module_put(ti->tt.module);
  80
  81         BUG_ON(ti->use < 0);
  82         up_read(&_lock);
  83
  84         return;
  85 }
  86
  87 static struct tt_internal *alloc_target(struct target_type *t)
  88 {
  89         struct tt_internal *ti = kmalloc(sizeof(*ti), GFP_KERNEL);
  90
  91         if (ti) {
  92                 memset(ti, 0, sizeof(*ti));
  93                 ti->tt = *t;
  94         }
  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 int 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                 up_write(&_lock);
 140                 return -EINVAL;
 141         }
 142
 143         if (ti->use) {
 144                 up_write(&_lock);
 145                 return -ETXTBSY;
 146         }
 147
 148         list_del(&ti->list);
 149         kfree(ti);
 150
 151         up_write(&_lock);
 152         return 0;
 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         if (dm_unregister_target(&error_target))
 191                 DMWARN("error target unregistration failed");
 192 }
 193
 194 EXPORT_SYMBOL(dm_register_target);
 195 EXPORT_SYMBOL(dm_unregister_target);