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 "dm.h" 13 #include "dm-path-selector.h" 14 15 #include <linux/slab.h> 16 17 struct ps_internal { 18 struct path_selector_type pst; 19 20 struct list_head list; 21 long use; 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) { 48 if ((psi->use == 0) && !try_module_get(psi->pst.module)) 49 psi = NULL; 50 else 51 psi->use++; 52 } 53 up_read(&_ps_lock); 54 55 return psi; 56 } 57 58 struct path_selector_type *dm_get_path_selector(const char *name) 59 { 60 struct ps_internal *psi; 61 62 if (!name) 63 return NULL; 64 65 psi = get_path_selector(name); 66 if (!psi) { 67 request_module("dm-%s", name); 68 psi = get_path_selector(name); 69 } 70 71 return psi ? &psi->pst : NULL; 72 } 73 74 void dm_put_path_selector(struct path_selector_type *pst) 75 { 76 struct ps_internal *psi; 77 78 if (!pst) 79 return; 80 81 down_read(&_ps_lock); 82 psi = __find_path_selector_type(pst->name); 83 if (!psi) 84 goto out; 85 86 if (--psi->use == 0) 87 module_put(psi->pst.module); 88 89 BUG_ON(psi->use < 0); 90 91 out: 92 up_read(&_ps_lock); 93 } 94 95 static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst) 96 { 97 struct ps_internal *psi = kzalloc(sizeof(*psi), GFP_KERNEL); 98 99 if (psi) 100 psi->pst = *pst; 101 102 return psi; 103 } 104 105 int dm_register_path_selector(struct path_selector_type *pst) 106 { 107 int r = 0; 108 struct ps_internal *psi = _alloc_path_selector(pst); 109 110 if (!psi) 111 return -ENOMEM; 112 113 down_write(&_ps_lock); 114 115 if (__find_path_selector_type(pst->name)) { 116 kfree(psi); 117 r = -EEXIST; 118 } else 119 list_add(&psi->list, &_path_selectors); 120 121 up_write(&_ps_lock); 122 123 return r; 124 } 125 126 int dm_unregister_path_selector(struct path_selector_type *pst) 127 { 128 struct ps_internal *psi; 129 130 down_write(&_ps_lock); 131 132 psi = __find_path_selector_type(pst->name); 133 if (!psi) { 134 up_write(&_ps_lock); 135 return -EINVAL; 136 } 137 138 if (psi->use) { 139 up_write(&_ps_lock); 140 return -ETXTBSY; 141 } 142 143 list_del(&psi->list); 144 145 up_write(&_ps_lock); 146 147 kfree(psi); 148 149 return 0; 150 } 151 152 EXPORT_SYMBOL_GPL(dm_register_path_selector); 153 EXPORT_SYMBOL_GPL(dm_unregister_path_selector); 154