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         if (ti->use < 0)
  82                 BUG();
  83         up_read(&_lock);
  84
  85         return;
  86 }
  87
  88 static struct tt_internal *alloc_target(struct target_type *t)
  89 {
  90         struct tt_internal *ti = kmalloc(sizeof(*ti), GFP_KERNEL);
  91
  92         if (ti) {
  93                 memset(ti, 0, sizeof(*ti));
  94                 ti->tt = *t;
  95         }
  96
  97         return ti;
  98 }
  99
 100
 101 int dm_target_iterate(void (*iter_func)(struct target_type *tt,
 102                                         void *param), void *param)
 103 {
 104         struct tt_internal *ti;
 105
 106         down_read(&_lock);
 107         list_for_each_entry (ti, &_targets, list)
 108                 iter_func(&ti->tt, param);
 109         up_read(&_lock);
 110
 111         return 0;
 112 }
 113
 114 int dm_register_target(struct target_type *t)
 115 {
 116         int rv = 0;
 117         struct tt_internal *ti = alloc_target(t);
 118
 119         if (!ti)
 120                 return -ENOMEM;
 121
 122         down_write(&_lock);
 123         if (__find_target_type(t->name))
 124                 rv = -EEXIST;
 125         else
 126                 list_add(&ti->list, &_targets);
 127
 128         up_write(&_lock);
 129         if (rv)
 130                 kfree(ti);
 131         return rv;
 132 }
 133
 134 int dm_unregister_target(struct target_type *t)
 135 {
 136         struct tt_internal *ti;
 137
 138         down_write(&_lock);
 139         if (!(ti = __find_target_type(t->name))) {
 140                 up_write(&_lock);
 141                 return -EINVAL;
 142         }
 143
 144         if (ti->use) {
 145                 up_write(&_lock);
 146                 return -ETXTBSY;
 147         }
 148
 149         list_del(&ti->list);
 150         kfree(ti);
 151
 152         up_write(&_lock);
 153         return 0;
 154 }
 155
 156 /*
 157  * io-err: always fails an io, useful for bringing
 158  * up LVs that have holes in them.
 159  */
 160 static int io_err_ctr(struct dm_target *ti, unsigned int argc, char **args)
 161 {
 162         return 0;
 163 }
 164
 165 static void io_err_dtr(struct dm_target *ti)
 166 {
 167         /* empty */
 168 }
 169
 170 static int io_err_map(struct dm_target *ti, struct bio *bio,
 171                       union map_info *map_context)
 172 {
 173         return -EIO;
 174 }
 175
 176 static struct target_type error_target = {
 177         .name = "error",
 178         .version = {1, 0, 1},
 179         .ctr  = io_err_ctr,
 180         .dtr  = io_err_dtr,
 181         .map  = io_err_map,
 182 };
 183
 184 int __init dm_target_init(void)
 185 {
 186         return dm_register_target(&error_target);
 187 }
 188
 189 void dm_target_exit(void)
 190 {
 191         if (dm_unregister_target(&error_target))
 192                 DMWARN("error target unregistration failed");
 193 }
 194
 195 EXPORT_SYMBOL(dm_register_target);
 196 EXPORT_SYMBOL(dm_unregister_target);