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