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