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 = kmalloc(sizeof(*ti), GFP_KERNEL);
  92
  93         if (ti) {
  94                 memset(ti, 0, sizeof(*ti));
  95                 ti->tt = *t;
  96         }
  97
  98         return ti;
  99 }
 100
 101
 102 int dm_target_iterate(void (*iter_func)(struct target_type *tt,
 103                                         void *param), void *param)
 104 {
 105         struct tt_internal *ti;
 106
 107         down_read(&_lock);
 108         list_for_each_entry (ti, &_targets, list)
 109                 iter_func(&ti->tt, param);
 110         up_read(&_lock);
 111
 112         return 0;
 113 }
 114
 115 int dm_register_target(struct target_type *t)
 116 {
 117         int rv = 0;
 118         struct tt_internal *ti = alloc_target(t);
 119
 120         if (!ti)
 121                 return -ENOMEM;
 122
 123         down_write(&_lock);
 124         if (__find_target_type(t->name))
 125                 rv = -EEXIST;
 126         else
 127                 list_add(&ti->list, &_targets);
 128
 129         up_write(&_lock);
 130         if (rv)
 131                 kfree(ti);
 132         return rv;
 133 }
 134
 135 int dm_unregister_target(struct target_type *t)
 136 {
 137         struct tt_internal *ti;
 138
 139         down_write(&_lock);
 140         if (!(ti = __find_target_type(t->name))) {
 141                 up_write(&_lock);
 142                 return -EINVAL;
 143         }
 144
 145         if (ti->use) {
 146                 up_write(&_lock);
 147                 return -ETXTBSY;
 148         }
 149
 150         list_del(&ti->list);
 151         kfree(ti);
 152
 153         up_write(&_lock);
 154         return 0;
 155 }
 156
 157 /*
 158  * io-err: always fails an io, useful for bringing
 159  * up LVs that have holes in them.
 160  */
 161 static int io_err_ctr(struct dm_target *ti, unsigned int argc, char **args)
 162 {
 163         return 0;
 164 }
 165
 166 static void io_err_dtr(struct dm_target *ti)
 167 {
 168         /* empty */
 169 }
 170
 171 static int io_err_map(struct dm_target *ti, struct bio *bio,
 172                       union map_info *map_context)
 173 {
 174         return -EIO;
 175 }
 176
 177 static struct target_type error_target = {
 178         .name = "error",
 179         .version = {1, 0, 1},
 180         .ctr  = io_err_ctr,
 181         .dtr  = io_err_dtr,
 182         .map  = io_err_map,
 183 };
 184
 185 int __init dm_target_init(void)
 186 {
 187         return dm_register_target(&error_target);
 188 }
 189
 190 void dm_target_exit(void)
 191 {
 192         if (dm_unregister_target(&error_target))
 193                 DMWARN("error target unregistration failed");
 194 }
 195
 196 EXPORT_SYMBOL(dm_register_target);
 197 EXPORT_SYMBOL(dm_unregister_target);