1/* 2 * Directory notifications for Linux. 3 * 4 * Copyright (C) 2000,2001,2002 Stephen Rothwell 5 * 6 * Copyright (C) 2009 Eric Paris <Red Hat Inc> 7 * dnotify was largly rewritten to use the new fsnotify infrastructure 8 * 9 * This program is free software; you can redistribute it and/or modify it 10 * under the terms of the GNU General Public License as published by the 11 * Free Software Foundation; either version 2, or (at your option) any 12 * later version. 13 * 14 * This program is distributed in the hope that it will be useful, but 15 * WITHOUT ANY WARRANTY; without even the implied warranty of 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 17 * General Public License for more details. 18 */ 19#include <linux/fs.h> 20#include <linux/module.h> 21#include <linux/sched.h> 22#include <linux/dnotify.h> 23#include <linux/init.h> 24#include <linux/spinlock.h> 25#include <linux/slab.h> 26#include <linux/fdtable.h> 27#include <linux/fsnotify_backend.h> 28 29int dir_notify_enable __read_mostly = 1; 30 31static struct kmem_cache *dnotify_struct_cache __read_mostly; 32static struct kmem_cache *dnotify_mark_cache __read_mostly; 33static struct fsnotify_group *dnotify_group __read_mostly; 34 35/* 36 * dnotify will attach one of these to each inode (i_fsnotify_marks) which 37 * is being watched by dnotify. If multiple userspace applications are watching 38 * the same directory with dnotify their information is chained in dn 39 */ 40struct dnotify_mark { 41 struct fsnotify_mark fsn_mark; 42 struct dnotify_struct *dn; 43}; 44 45/* 46 * When a process starts or stops watching an inode the set of events which 47 * dnotify cares about for that inode may change. This function runs the 48 * list of everything receiving dnotify events about this directory and calculates 49 * the set of all those events. After it updates what dnotify is interested in 50 * it calls the fsnotify function so it can update the set of all events relevant 51 * to this inode. 52 */ 53static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark) 54{ 55 __u32 new_mask, old_mask; 56 struct dnotify_struct *dn; 57 struct dnotify_mark *dn_mark = container_of(fsn_mark, 58 struct dnotify_mark, 59 fsn_mark); 60 61 assert_spin_locked(&fsn_mark->lock); 62 63 old_mask = fsn_mark->mask; 64 new_mask = 0; 65 for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next) 66 new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT); 67 fsnotify_set_mark_mask_locked(fsn_mark, new_mask); 68 69 if (old_mask == new_mask) 70 return; 71 72 if (fsn_mark->inode) 73 fsnotify_recalc_inode_mask(fsn_mark->inode); 74} 75 76/* 77 * Mains fsnotify call where events are delivered to dnotify. 78 * Find the dnotify mark on the relevant inode, run the list of dnotify structs 79 * on that mark and determine which of them has expressed interest in receiving 80 * events of this type. When found send the correct process and signal and 81 * destroy the dnotify struct if it was not registered to receive multiple 82 * events. 83 */ 84static int dnotify_handle_event(struct fsnotify_group *group, 85 struct inode *inode, 86 struct fsnotify_mark *inode_mark, 87 struct fsnotify_mark *vfsmount_mark, 88 u32 mask, void *data, int data_type, 89 const unsigned char *file_name, u32 cookie) 90{ 91 struct dnotify_mark *dn_mark; 92 struct dnotify_struct *dn; 93 struct dnotify_struct **prev; 94 struct fown_struct *fown; 95 __u32 test_mask = mask & ~FS_EVENT_ON_CHILD; 96 97 /* not a dir, dnotify doesn't care */ 98 if (!S_ISDIR(inode->i_mode)) 99 return 0; 100 101 BUG_ON(vfsmount_mark); 102 103 dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark); 104 105 spin_lock(&inode_mark->lock); 106 prev = &dn_mark->dn; 107 while ((dn = *prev) != NULL) { 108 if ((dn->dn_mask & test_mask) == 0) { 109 prev = &dn->dn_next; 110 continue; 111 } 112 fown = &dn->dn_filp->f_owner; 113 send_sigio(fown, dn->dn_fd, POLL_MSG); 114 if (dn->dn_mask & FS_DN_MULTISHOT) 115 prev = &dn->dn_next; 116 else { 117 *prev = dn->dn_next; 118 kmem_cache_free(dnotify_struct_cache, dn); 119 dnotify_recalc_inode_mask(inode_mark); 120 } 121 } 122 123 spin_unlock(&inode_mark->lock); 124 125 return 0; 126} 127 128static void dnotify_free_mark(struct fsnotify_mark *fsn_mark) 129{ 130 struct dnotify_mark *dn_mark = container_of(fsn_mark, 131 struct dnotify_mark, 132 fsn_mark); 133 134 BUG_ON(dn_mark->dn); 135 136 kmem_cache_free(dnotify_mark_cache, dn_mark); 137} 138 139static struct fsnotify_ops dnotify_fsnotify_ops = { 140 .handle_event = dnotify_handle_event, 141}; 142 143/* 144 * Called every time a file is closed. Looks first for a dnotify mark on the 145 * inode. If one is found run all of the ->dn structures attached to that 146 * mark for one relevant to this process closing the file and remove that 147 * dnotify_struct. If that was the last dnotify_struct also remove the 148 * fsnotify_mark. 149 */ 150void dnotify_flush(struct file *filp, fl_owner_t id) 151{ 152 struct fsnotify_mark *fsn_mark; 153 struct dnotify_mark *dn_mark; 154 struct dnotify_struct *dn; 155 struct dnotify_struct **prev; 156 struct inode *inode; 157 158 inode = file_inode(filp); 159 if (!S_ISDIR(inode->i_mode)) 160 return; 161 162 fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode); 163 if (!fsn_mark) 164 return; 165 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); 166 167 mutex_lock(&dnotify_group->mark_mutex); 168 169 spin_lock(&fsn_mark->lock); 170 prev = &dn_mark->dn; 171 while ((dn = *prev) != NULL) { 172 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) { 173 *prev = dn->dn_next; 174 kmem_cache_free(dnotify_struct_cache, dn); 175 dnotify_recalc_inode_mask(fsn_mark); 176 break; 177 } 178 prev = &dn->dn_next; 179 } 180 181 spin_unlock(&fsn_mark->lock); 182 183 /* nothing else could have found us thanks to the dnotify_groups 184 mark_mutex */ 185 if (dn_mark->dn == NULL) 186 fsnotify_destroy_mark_locked(fsn_mark, dnotify_group); 187 188 mutex_unlock(&dnotify_group->mark_mutex); 189 190 fsnotify_put_mark(fsn_mark); 191} 192 193/* this conversion is done only at watch creation */ 194static __u32 convert_arg(unsigned long arg) 195{ 196 __u32 new_mask = FS_EVENT_ON_CHILD; 197 198 if (arg & DN_MULTISHOT) 199 new_mask |= FS_DN_MULTISHOT; 200 if (arg & DN_DELETE) 201 new_mask |= (FS_DELETE | FS_MOVED_FROM); 202 if (arg & DN_MODIFY) 203 new_mask |= FS_MODIFY; 204 if (arg & DN_ACCESS) 205 new_mask |= FS_ACCESS; 206 if (arg & DN_ATTRIB) 207 new_mask |= FS_ATTRIB; 208 if (arg & DN_RENAME) 209 new_mask |= FS_DN_RENAME; 210 if (arg & DN_CREATE) 211 new_mask |= (FS_CREATE | FS_MOVED_TO); 212 213 return new_mask; 214} 215 216/* 217 * If multiple processes watch the same inode with dnotify there is only one 218 * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct 219 * onto that mark. This function either attaches the new dnotify_struct onto 220 * that list, or it |= the mask onto an existing dnofiy_struct. 221 */ 222static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark, 223 fl_owner_t id, int fd, struct file *filp, __u32 mask) 224{ 225 struct dnotify_struct *odn; 226 227 odn = dn_mark->dn; 228 while (odn != NULL) { 229 /* adding more events to existing dnofiy_struct? */ 230 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) { 231 odn->dn_fd = fd; 232 odn->dn_mask |= mask; 233 return -EEXIST; 234 } 235 odn = odn->dn_next; 236 } 237 238 dn->dn_mask = mask; 239 dn->dn_fd = fd; 240 dn->dn_filp = filp; 241 dn->dn_owner = id; 242 dn->dn_next = dn_mark->dn; 243 dn_mark->dn = dn; 244 245 return 0; 246} 247 248/* 249 * When a process calls fcntl to attach a dnotify watch to a directory it ends 250 * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be 251 * attached to the fsnotify_mark. 252 */ 253int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg) 254{ 255 struct dnotify_mark *new_dn_mark, *dn_mark; 256 struct fsnotify_mark *new_fsn_mark, *fsn_mark; 257 struct dnotify_struct *dn; 258 struct inode *inode; 259 fl_owner_t id = current->files; 260 struct file *f; 261 int destroy = 0, error = 0; 262 __u32 mask; 263 264 /* we use these to tell if we need to kfree */ 265 new_fsn_mark = NULL; 266 dn = NULL; 267 268 if (!dir_notify_enable) { 269 error = -EINVAL; 270 goto out_err; 271 } 272 273 /* a 0 mask means we are explicitly removing the watch */ 274 if ((arg & ~DN_MULTISHOT) == 0) { 275 dnotify_flush(filp, id); 276 error = 0; 277 goto out_err; 278 } 279 280 /* dnotify only works on directories */ 281 inode = file_inode(filp); 282 if (!S_ISDIR(inode->i_mode)) { 283 error = -ENOTDIR; 284 goto out_err; 285 } 286 287 /* expect most fcntl to add new rather than augment old */ 288 dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL); 289 if (!dn) { 290 error = -ENOMEM; 291 goto out_err; 292 } 293 294 /* new fsnotify mark, we expect most fcntl calls to add a new mark */ 295 new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL); 296 if (!new_dn_mark) { 297 error = -ENOMEM; 298 goto out_err; 299 } 300 301 /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */ 302 mask = convert_arg(arg); 303 304 /* set up the new_fsn_mark and new_dn_mark */ 305 new_fsn_mark = &new_dn_mark->fsn_mark; 306 fsnotify_init_mark(new_fsn_mark, dnotify_free_mark); 307 new_fsn_mark->mask = mask; 308 new_dn_mark->dn = NULL; 309 310 /* this is needed to prevent the fcntl/close race described below */ 311 mutex_lock(&dnotify_group->mark_mutex); 312 313 /* add the new_fsn_mark or find an old one. */ 314 fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode); 315 if (fsn_mark) { 316 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); 317 spin_lock(&fsn_mark->lock); 318 } else { 319 fsnotify_add_mark_locked(new_fsn_mark, dnotify_group, inode, 320 NULL, 0); 321 spin_lock(&new_fsn_mark->lock); 322 fsn_mark = new_fsn_mark; 323 dn_mark = new_dn_mark; 324 /* we used new_fsn_mark, so don't free it */ 325 new_fsn_mark = NULL; 326 } 327 328 rcu_read_lock(); 329 f = fcheck(fd); 330 rcu_read_unlock(); 331 332 /* if (f != filp) means that we lost a race and another task/thread 333 * actually closed the fd we are still playing with before we grabbed 334 * the dnotify_groups mark_mutex and fsn_mark->lock. Since closing the 335 * fd is the only time we clean up the marks we need to get our mark 336 * off the list. */ 337 if (f != filp) { 338 /* if we added ourselves, shoot ourselves, it's possible that 339 * the flush actually did shoot this fsn_mark. That's fine too 340 * since multiple calls to destroy_mark is perfectly safe, if 341 * we found a dn_mark already attached to the inode, just sod 342 * off silently as the flush at close time dealt with it. 343 */ 344 if (dn_mark == new_dn_mark) 345 destroy = 1; 346 goto out; 347 } 348 349 __f_setown(filp, task_pid(current), PIDTYPE_PID, 0); 350 351 error = attach_dn(dn, dn_mark, id, fd, filp, mask); 352 /* !error means that we attached the dn to the dn_mark, so don't free it */ 353 if (!error) 354 dn = NULL; 355 /* -EEXIST means that we didn't add this new dn and used an old one. 356 * that isn't an error (and the unused dn should be freed) */ 357 else if (error == -EEXIST) 358 error = 0; 359 360 dnotify_recalc_inode_mask(fsn_mark); 361out: 362 spin_unlock(&fsn_mark->lock); 363 364 if (destroy) 365 fsnotify_destroy_mark_locked(fsn_mark, dnotify_group); 366 367 mutex_unlock(&dnotify_group->mark_mutex); 368 fsnotify_put_mark(fsn_mark); 369out_err: 370 if (new_fsn_mark) 371 fsnotify_put_mark(new_fsn_mark); 372 if (dn) 373 kmem_cache_free(dnotify_struct_cache, dn); 374 return error; 375} 376 377static int __init dnotify_init(void) 378{ 379 dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC); 380 dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC); 381 382 dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops); 383 if (IS_ERR(dnotify_group)) 384 panic("unable to allocate fsnotify group for dnotify\n"); 385 return 0; 386} 387 388module_init(dnotify_init) 389