linux/drivers/md/dm-target.c
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   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
  14#define DM_MSG_PREFIX "target"
  15
  16static LIST_HEAD(_targets);
  17static DECLARE_RWSEM(_lock);
  18
  19#define DM_MOD_NAME_SIZE 32
  20
  21static inline struct target_type *__find_target_type(const char *name)
  22{
  23        struct target_type *tt;
  24
  25        list_for_each_entry(tt, &_targets, list)
  26                if (!strcmp(name, tt->name))
  27                        return tt;
  28
  29        return NULL;
  30}
  31
  32static struct target_type *get_target_type(const char *name)
  33{
  34        struct target_type *tt;
  35
  36        down_read(&_lock);
  37
  38        tt = __find_target_type(name);
  39        if (tt && !try_module_get(tt->module))
  40                tt = NULL;
  41
  42        up_read(&_lock);
  43        return tt;
  44}
  45
  46static void load_module(const char *name)
  47{
  48        request_module("dm-%s", name);
  49}
  50
  51struct target_type *dm_get_target_type(const char *name)
  52{
  53        struct target_type *tt = get_target_type(name);
  54
  55        if (!tt) {
  56                load_module(name);
  57                tt = get_target_type(name);
  58        }
  59
  60        return tt;
  61}
  62
  63void dm_put_target_type(struct target_type *tt)
  64{
  65        down_read(&_lock);
  66        module_put(tt->module);
  67        up_read(&_lock);
  68}
  69
  70int dm_target_iterate(void (*iter_func)(struct target_type *tt,
  71                                        void *param), void *param)
  72{
  73        struct target_type *tt;
  74
  75        down_read(&_lock);
  76        list_for_each_entry(tt, &_targets, list)
  77                iter_func(tt, param);
  78        up_read(&_lock);
  79
  80        return 0;
  81}
  82
  83int dm_register_target(struct target_type *tt)
  84{
  85        int rv = 0;
  86
  87        down_write(&_lock);
  88        if (__find_target_type(tt->name))
  89                rv = -EEXIST;
  90        else
  91                list_add(&tt->list, &_targets);
  92
  93        up_write(&_lock);
  94        return rv;
  95}
  96
  97void dm_unregister_target(struct target_type *tt)
  98{
  99        down_write(&_lock);
 100        if (!__find_target_type(tt->name)) {
 101                DMCRIT("Unregistering unrecognised target: %s", tt->name);
 102                BUG();
 103        }
 104
 105        list_del(&tt->list);
 106
 107        up_write(&_lock);
 108}
 109
 110/*
 111 * io-err: always fails an io, useful for bringing
 112 * up LVs that have holes in them.
 113 */
 114static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args)
 115{
 116        /*
 117         * Return error for discards instead of -EOPNOTSUPP
 118         */
 119        tt->num_discard_bios = 1;
 120
 121        return 0;
 122}
 123
 124static void io_err_dtr(struct dm_target *tt)
 125{
 126        /* empty */
 127}
 128
 129static int io_err_map(struct dm_target *tt, struct bio *bio)
 130{
 131        return -EIO;
 132}
 133
 134static struct target_type error_target = {
 135        .name = "error",
 136        .version = {1, 1, 0},
 137        .ctr  = io_err_ctr,
 138        .dtr  = io_err_dtr,
 139        .map  = io_err_map,
 140};
 141
 142int __init dm_target_init(void)
 143{
 144        return dm_register_target(&error_target);
 145}
 146
 147void dm_target_exit(void)
 148{
 149        dm_unregister_target(&error_target);
 150}
 151
 152EXPORT_SYMBOL(dm_register_target);
 153EXPORT_SYMBOL(dm_unregister_target);
 154
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