drivers/md/dm-path-selector.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2003 Sistina Software.
   4  * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
   5  *
   6  * Module Author: Heinz Mauelshagen
   7  *
   8  * This file is released under the GPL.
   9  *
  10  * Path selector registration.
  11  */
  12
  13 #include <linux/device-mapper.h>
  14 #include <linux/module.h>
  15
  16 #include "dm-path-selector.h"
  17
  18 #include <linux/slab.h>
  19
  20 struct ps_internal {
  21         struct path_selector_type pst;
  22         struct list_head list;
  23 };
  24
  25 #define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
  26
  27 static LIST_HEAD(_path_selectors);
  28 static DECLARE_RWSEM(_ps_lock);
  29
  30 static struct ps_internal *__find_path_selector_type(const char *name)
  31 {
  32         struct ps_internal *psi;
  33
  34         list_for_each_entry(psi, &_path_selectors, list) {
  35                 if (!strcmp(name, psi->pst.name))
  36                         return psi;
  37         }
  38
  39         return NULL;
  40 }
  41
  42 static struct ps_internal *get_path_selector(const char *name)
  43 {
  44         struct ps_internal *psi;
  45
  46         down_read(&_ps_lock);
  47         psi = __find_path_selector_type(name);
  48         if (psi && !try_module_get(psi->pst.module))
  49                 psi = NULL;
  50         up_read(&_ps_lock);
  51
  52         return psi;
  53 }
  54
  55 struct path_selector_type *dm_get_path_selector(const char *name)
  56 {
  57         struct ps_internal *psi;
  58
  59         if (!name)
  60                 return NULL;
  61
  62         psi = get_path_selector(name);
  63         if (!psi) {
  64                 request_module("dm-%s", name);
  65                 psi = get_path_selector(name);
  66         }
  67
  68         return psi ? &psi->pst : NULL;
  69 }
  70
  71 void dm_put_path_selector(struct path_selector_type *pst)
  72 {
  73         struct ps_internal *psi;
  74
  75         if (!pst)
  76                 return;
  77
  78         down_read(&_ps_lock);
  79         psi = __find_path_selector_type(pst->name);
  80         if (!psi)
  81                 goto out;
  82
  83         module_put(psi->pst.module);
  84 out:
  85         up_read(&_ps_lock);
  86 }
  87
  88 static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
  89 {
  90         struct ps_internal *psi = kzalloc(sizeof(*psi), GFP_KERNEL);
  91
  92         if (psi)
  93                 psi->pst = *pst;
  94
  95         return psi;
  96 }
  97
  98 int dm_register_path_selector(struct path_selector_type *pst)
  99 {
 100         int r = 0;
 101         struct ps_internal *psi = _alloc_path_selector(pst);
 102
 103         if (!psi)
 104                 return -ENOMEM;
 105
 106         down_write(&_ps_lock);
 107
 108         if (__find_path_selector_type(pst->name)) {
 109                 kfree(psi);
 110                 r = -EEXIST;
 111         } else
 112                 list_add(&psi->list, &_path_selectors);
 113
 114         up_write(&_ps_lock);
 115
 116         return r;
 117 }
 118 EXPORT_SYMBOL_GPL(dm_register_path_selector);
 119
 120 int dm_unregister_path_selector(struct path_selector_type *pst)
 121 {
 122         struct ps_internal *psi;
 123
 124         down_write(&_ps_lock);
 125
 126         psi = __find_path_selector_type(pst->name);
 127         if (!psi) {
 128                 up_write(&_ps_lock);
 129                 return -EINVAL;
 130         }
 131
 132         list_del(&psi->list);
 133
 134         up_write(&_ps_lock);
 135
 136         kfree(psi);
 137
 138         return 0;
 139 }
 140 EXPORT_SYMBOL_GPL(dm_unregister_path_selector);