1 /* 2 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com> 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License as published by 6 * the Free Software Foundation; either version 2, or (at your option) 7 * any later version. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; see the file COPYING. If not, write to 16 * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 17 */ 18 19 #include <linux/dcache.h> 20 #include <linux/fs.h> 21 #include <linux/gfp.h> 22 #include <linux/init.h> 23 #include <linux/module.h> 24 #include <linux/mount.h> 25 #include <linux/srcu.h> 26 27 #include <linux/fsnotify_backend.h> 28 #include "fsnotify.h" 29 30 /* 31 * Clear all of the marks on an inode when it is being evicted from core 32 */ 33 void __fsnotify_inode_delete(struct inode *inode) 34 { 35 fsnotify_clear_marks_by_inode(inode); 36 } 37 EXPORT_SYMBOL_GPL(__fsnotify_inode_delete); 38 39 void __fsnotify_vfsmount_delete(struct vfsmount *mnt) 40 { 41 fsnotify_clear_marks_by_mount(mnt); 42 } 43 44 /** 45 * fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes. 46 * @sb: superblock being unmounted. 47 * 48 * Called during unmount with no locks held, so needs to be safe against 49 * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block. 50 */ 51 void fsnotify_unmount_inodes(struct super_block *sb) 52 { 53 struct inode *inode, *iput_inode = NULL; 54 55 spin_lock(&sb->s_inode_list_lock); 56 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { 57 /* 58 * We cannot __iget() an inode in state I_FREEING, 59 * I_WILL_FREE, or I_NEW which is fine because by that point 60 * the inode cannot have any associated watches. 61 */ 62 spin_lock(&inode->i_lock); 63 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) { 64 spin_unlock(&inode->i_lock); 65 continue; 66 } 67 68 /* 69 * If i_count is zero, the inode cannot have any watches and 70 * doing an __iget/iput with MS_ACTIVE clear would actually 71 * evict all inodes with zero i_count from icache which is 72 * unnecessarily violent and may in fact be illegal to do. 73 */ 74 if (!atomic_read(&inode->i_count)) { 75 spin_unlock(&inode->i_lock); 76 continue; 77 } 78 79 __iget(inode); 80 spin_unlock(&inode->i_lock); 81 spin_unlock(&sb->s_inode_list_lock); 82 83 if (iput_inode) 84 iput(iput_inode); 85 86 /* for each watch, send FS_UNMOUNT and then remove it */ 87 fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0); 88 89 fsnotify_inode_delete(inode); 90 91 iput_inode = inode; 92 93 spin_lock(&sb->s_inode_list_lock); 94 } 95 spin_unlock(&sb->s_inode_list_lock); 96 97 if (iput_inode) 98 iput(iput_inode); 99 } 100 101 /* 102 * Given an inode, first check if we care what happens to our children. Inotify 103 * and dnotify both tell their parents about events. If we care about any event 104 * on a child we run all of our children and set a dentry flag saying that the 105 * parent cares. Thus when an event happens on a child it can quickly tell if 106 * if there is a need to find a parent and send the event to the parent. 107 */ 108 void __fsnotify_update_child_dentry_flags(struct inode *inode) 109 { 110 struct dentry *alias; 111 int watched; 112 113 if (!S_ISDIR(inode->i_mode)) 114 return; 115 116 /* determine if the children should tell inode about their events */ 117 watched = fsnotify_inode_watches_children(inode); 118 119 spin_lock(&inode->i_lock); 120 /* run all of the dentries associated with this inode. Since this is a 121 * directory, there damn well better only be one item on this list */ 122 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) { 123 struct dentry *child; 124 125 /* run all of the children of the original inode and fix their 126 * d_flags to indicate parental interest (their parent is the 127 * original inode) */ 128 spin_lock(&alias->d_lock); 129 list_for_each_entry(child, &alias->d_subdirs, d_child) { 130 if (!child->d_inode) 131 continue; 132 133 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED); 134 if (watched) 135 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED; 136 else 137 child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED; 138 spin_unlock(&child->d_lock); 139 } 140 spin_unlock(&alias->d_lock); 141 } 142 spin_unlock(&inode->i_lock); 143 } 144 145 /* Notify this dentry's parent about a child's events. */ 146 int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask) 147 { 148 struct dentry *parent; 149 struct inode *p_inode; 150 int ret = 0; 151 152 if (!dentry) 153 dentry = path->dentry; 154 155 if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED)) 156 return 0; 157 158 parent = dget_parent(dentry); 159 p_inode = parent->d_inode; 160 161 if (unlikely(!fsnotify_inode_watches_children(p_inode))) 162 __fsnotify_update_child_dentry_flags(p_inode); 163 else if (p_inode->i_fsnotify_mask & mask) { 164 struct name_snapshot name; 165 166 /* we are notifying a parent so come up with the new mask which 167 * specifies these are events which came from a child. */ 168 mask |= FS_EVENT_ON_CHILD; 169 170 take_dentry_name_snapshot(&name, dentry); 171 if (path) 172 ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH, 173 name.name, 0); 174 else 175 ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE, 176 name.name, 0); 177 release_dentry_name_snapshot(&name); 178 } 179 180 dput(parent); 181 182 return ret; 183 } 184 EXPORT_SYMBOL_GPL(__fsnotify_parent); 185 186 static int send_to_group(struct inode *to_tell, 187 struct fsnotify_mark *inode_mark, 188 struct fsnotify_mark *vfsmount_mark, 189 __u32 mask, const void *data, 190 int data_is, u32 cookie, 191 const unsigned char *file_name, 192 struct fsnotify_iter_info *iter_info) 193 { 194 struct fsnotify_group *group = NULL; 195 __u32 inode_test_mask = 0; 196 __u32 vfsmount_test_mask = 0; 197 198 if (unlikely(!inode_mark && !vfsmount_mark)) { 199 BUG(); 200 return 0; 201 } 202 203 /* clear ignored on inode modification */ 204 if (mask & FS_MODIFY) { 205 if (inode_mark && 206 !(inode_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)) 207 inode_mark->ignored_mask = 0; 208 if (vfsmount_mark && 209 !(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)) 210 vfsmount_mark->ignored_mask = 0; 211 } 212 213 /* does the inode mark tell us to do something? */ 214 if (inode_mark) { 215 group = inode_mark->group; 216 inode_test_mask = (mask & ~FS_EVENT_ON_CHILD); 217 inode_test_mask &= inode_mark->mask; 218 inode_test_mask &= ~inode_mark->ignored_mask; 219 } 220 221 /* does the vfsmount_mark tell us to do something? */ 222 if (vfsmount_mark) { 223 vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD); 224 group = vfsmount_mark->group; 225 vfsmount_test_mask &= vfsmount_mark->mask; 226 vfsmount_test_mask &= ~vfsmount_mark->ignored_mask; 227 if (inode_mark) 228 vfsmount_test_mask &= ~inode_mark->ignored_mask; 229 } 230 231 pr_debug("%s: group=%p to_tell=%p mask=%x inode_mark=%p" 232 " inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x" 233 " data=%p data_is=%d cookie=%d\n", 234 __func__, group, to_tell, mask, inode_mark, 235 inode_test_mask, vfsmount_mark, vfsmount_test_mask, data, 236 data_is, cookie); 237 238 if (!inode_test_mask && !vfsmount_test_mask) 239 return 0; 240 241 return group->ops->handle_event(group, to_tell, inode_mark, 242 vfsmount_mark, mask, data, data_is, 243 file_name, cookie, iter_info); 244 } 245 246 /* 247 * This is the main call to fsnotify. The VFS calls into hook specific functions 248 * in linux/fsnotify.h. Those functions then in turn call here. Here will call 249 * out to all of the registered fsnotify_group. Those groups can then use the 250 * notification event in whatever means they feel necessary. 251 */ 252 int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is, 253 const unsigned char *file_name, u32 cookie) 254 { 255 struct hlist_node *inode_node = NULL, *vfsmount_node = NULL; 256 struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL; 257 struct fsnotify_group *inode_group, *vfsmount_group; 258 struct fsnotify_mark_connector *inode_conn, *vfsmount_conn; 259 struct fsnotify_iter_info iter_info; 260 struct mount *mnt; 261 int ret = 0; 262 /* global tests shouldn't care about events on child only the specific event */ 263 __u32 test_mask = (mask & ~FS_EVENT_ON_CHILD); 264 265 if (data_is == FSNOTIFY_EVENT_PATH) 266 mnt = real_mount(((const struct path *)data)->mnt); 267 else 268 mnt = NULL; 269 270 /* 271 * Optimization: srcu_read_lock() has a memory barrier which can 272 * be expensive. It protects walking the *_fsnotify_marks lists. 273 * However, if we do not walk the lists, we do not have to do 274 * SRCU because we have no references to any objects and do not 275 * need SRCU to keep them "alive". 276 */ 277 if (!to_tell->i_fsnotify_marks && 278 (!mnt || !mnt->mnt_fsnotify_marks)) 279 return 0; 280 /* 281 * if this is a modify event we may need to clear the ignored masks 282 * otherwise return if neither the inode nor the vfsmount care about 283 * this type of event. 284 */ 285 if (!(mask & FS_MODIFY) && 286 !(test_mask & to_tell->i_fsnotify_mask) && 287 !(mnt && test_mask & mnt->mnt_fsnotify_mask)) 288 return 0; 289 290 iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu); 291 292 if ((mask & FS_MODIFY) || 293 (test_mask & to_tell->i_fsnotify_mask)) { 294 inode_conn = srcu_dereference(to_tell->i_fsnotify_marks, 295 &fsnotify_mark_srcu); 296 if (inode_conn) 297 inode_node = srcu_dereference(inode_conn->list.first, 298 &fsnotify_mark_srcu); 299 } 300 301 if (mnt && ((mask & FS_MODIFY) || 302 (test_mask & mnt->mnt_fsnotify_mask))) { 303 inode_conn = srcu_dereference(to_tell->i_fsnotify_marks, 304 &fsnotify_mark_srcu); 305 if (inode_conn) 306 inode_node = srcu_dereference(inode_conn->list.first, 307 &fsnotify_mark_srcu); 308 vfsmount_conn = srcu_dereference(mnt->mnt_fsnotify_marks, 309 &fsnotify_mark_srcu); 310 if (vfsmount_conn) 311 vfsmount_node = srcu_dereference( 312 vfsmount_conn->list.first, 313 &fsnotify_mark_srcu); 314 } 315 316 /* 317 * We need to merge inode & vfsmount mark lists so that inode mark 318 * ignore masks are properly reflected for mount mark notifications. 319 * That's why this traversal is so complicated... 320 */ 321 while (inode_node || vfsmount_node) { 322 inode_group = NULL; 323 inode_mark = NULL; 324 vfsmount_group = NULL; 325 vfsmount_mark = NULL; 326 327 if (inode_node) { 328 inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu), 329 struct fsnotify_mark, obj_list); 330 inode_group = inode_mark->group; 331 } 332 333 if (vfsmount_node) { 334 vfsmount_mark = hlist_entry(srcu_dereference(vfsmount_node, &fsnotify_mark_srcu), 335 struct fsnotify_mark, obj_list); 336 vfsmount_group = vfsmount_mark->group; 337 } 338 339 if (inode_group && vfsmount_group) { 340 int cmp = fsnotify_compare_groups(inode_group, 341 vfsmount_group); 342 if (cmp > 0) { 343 inode_group = NULL; 344 inode_mark = NULL; 345 } else if (cmp < 0) { 346 vfsmount_group = NULL; 347 vfsmount_mark = NULL; 348 } 349 } 350 351 iter_info.inode_mark = inode_mark; 352 iter_info.vfsmount_mark = vfsmount_mark; 353 354 ret = send_to_group(to_tell, inode_mark, vfsmount_mark, mask, 355 data, data_is, cookie, file_name, 356 &iter_info); 357 358 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS)) 359 goto out; 360 361 if (inode_group) 362 inode_node = srcu_dereference(inode_node->next, 363 &fsnotify_mark_srcu); 364 if (vfsmount_group) 365 vfsmount_node = srcu_dereference(vfsmount_node->next, 366 &fsnotify_mark_srcu); 367 } 368 ret = 0; 369 out: 370 srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx); 371 372 return ret; 373 } 374 EXPORT_SYMBOL_GPL(fsnotify); 375 376 extern struct kmem_cache *fsnotify_mark_connector_cachep; 377 378 static __init int fsnotify_init(void) 379 { 380 int ret; 381 382 BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23); 383 384 ret = init_srcu_struct(&fsnotify_mark_srcu); 385 if (ret) 386 panic("initializing fsnotify_mark_srcu"); 387 388 fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector, 389 SLAB_PANIC); 390 391 return 0; 392 } 393 core_initcall(fsnotify_init); 394