drivers/md/dm-path-selector.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software.
   3  * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
   4  *
   5  * Module Author: Heinz Mauelshagen
   6  *
   7  * This file is released under the GPL.
   8  *
   9  * Path selector registration.
  10  */
  11
  12 #include <linux/device-mapper.h>
  13 #include <linux/module.h>
  14
  15 #include "dm-path-selector.h"
  16
  17 #include <linux/slab.h>
  18
  19 struct ps_internal {
  20         struct path_selector_type pst;
  21         struct list_head list;
  22 };
  23
  24 #define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
  25
  26 static LIST_HEAD(_path_selectors);
  27 static DECLARE_RWSEM(_ps_lock);
  28
  29 static struct ps_internal *__find_path_selector_type(const char *name)
  30 {
  31         struct ps_internal *psi;
  32
  33         list_for_each_entry(psi, &_path_selectors, list) {
  34                 if (!strcmp(name, psi->pst.name))
  35                         return psi;
  36         }
  37
  38         return NULL;
  39 }
  40
  41 static struct ps_internal *get_path_selector(const char *name)
  42 {
  43         struct ps_internal *psi;
  44
  45         down_read(&_ps_lock);
  46         psi = __find_path_selector_type(name);
  47         if (psi && !try_module_get(psi->pst.module))
  48                 psi = NULL;
  49         up_read(&_ps_lock);
  50
  51         return psi;
  52 }
  53
  54 struct path_selector_type *dm_get_path_selector(const char *name)
  55 {
  56         struct ps_internal *psi;
  57
  58         if (!name)
  59                 return NULL;
  60
  61         psi = get_path_selector(name);
  62         if (!psi) {
  63                 request_module("dm-%s", name);
  64                 psi = get_path_selector(name);
  65         }
  66
  67         return psi ? &psi->pst : NULL;
  68 }
  69
  70 void dm_put_path_selector(struct path_selector_type *pst)
  71 {
  72         struct ps_internal *psi;
  73
  74         if (!pst)
  75                 return;
  76
  77         down_read(&_ps_lock);
  78         psi = __find_path_selector_type(pst->name);
  79         if (!psi)
  80                 goto out;
  81
  82         module_put(psi->pst.module);
  83 out:
  84         up_read(&_ps_lock);
  85 }
  86
  87 static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
  88 {
  89         struct ps_internal *psi = kzalloc(sizeof(*psi), GFP_KERNEL);
  90
  91         if (psi)
  92                 psi->pst = *pst;
  93
  94         return psi;
  95 }
  96
  97 int dm_register_path_selector(struct path_selector_type *pst)
  98 {
  99         int r = 0;
 100         struct ps_internal *psi = _alloc_path_selector(pst);
 101
 102         if (!psi)
 103                 return -ENOMEM;
 104
 105         down_write(&_ps_lock);
 106
 107         if (__find_path_selector_type(pst->name)) {
 108                 kfree(psi);
 109                 r = -EEXIST;
 110         } else
 111                 list_add(&psi->list, &_path_selectors);
 112
 113         up_write(&_ps_lock);
 114
 115         return r;
 116 }
 117
 118 int dm_unregister_path_selector(struct path_selector_type *pst)
 119 {
 120         struct ps_internal *psi;
 121
 122         down_write(&_ps_lock);
 123
 124         psi = __find_path_selector_type(pst->name);
 125         if (!psi) {
 126                 up_write(&_ps_lock);
 127                 return -EINVAL;
 128         }
 129
 130         list_del(&psi->list);
 131
 132         up_write(&_ps_lock);
 133
 134         kfree(psi);
 135
 136         return 0;
 137 }
 138
 139 EXPORT_SYMBOL_GPL(dm_register_path_selector);
 140 EXPORT_SYMBOL_GPL(dm_unregister_path_selector);