base/files/file_path_watcher_linux.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/files/file_path_watcher.h"
   6
   7 #include <errno.h>
   8 #include <string.h>
   9 #include <sys/inotify.h>
  10 #include <sys/ioctl.h>
  11 #include <sys/select.h>
  12 #include <unistd.h>
  13
  14 #include <algorithm>
  15 #include <map>
  16 #include <set>
  17 #include <utility>
  18 #include <vector>
  19
  20 #include "base/bind.h"
  21 #include "base/containers/hash_tables.h"
  22 #include "base/debug/trace_event.h"
  23 #include "base/files/file_enumerator.h"
  24 #include "base/files/file_path.h"
  25 #include "base/files/file_util.h"
  26 #include "base/lazy_instance.h"
  27 #include "base/location.h"
  28 #include "base/logging.h"
  29 #include "base/memory/scoped_ptr.h"
  30 #include "base/message_loop/message_loop.h"
  31 #include "base/message_loop/message_loop_proxy.h"
  32 #include "base/posix/eintr_wrapper.h"
  33 #include "base/synchronization/lock.h"
  34 #include "base/threading/thread.h"
  35
  36 namespace base {
  37
  38 namespace {
  39
  40 class FilePathWatcherImpl;
  41
  42 // Singleton to manage all inotify watches.
  43 // TODO(tony): It would be nice if this wasn't a singleton.
  44 // http://crbug.com/38174
  45 class InotifyReader {
  46  public:
  47   typedef int Watch;  // Watch descriptor used by AddWatch and RemoveWatch.
  48   static const Watch kInvalidWatch = -1;
  49
  50   // Watch directory |path| for changes. |watcher| will be notified on each
  51   // change. Returns kInvalidWatch on failure.
  52   Watch AddWatch(const FilePath& path, FilePathWatcherImpl* watcher);
  53
  54   // Remove |watch| if it's valid.
  55   void RemoveWatch(Watch watch, FilePathWatcherImpl* watcher);
  56
  57   // Callback for InotifyReaderTask.
  58   void OnInotifyEvent(const inotify_event* event);
  59
  60  private:
  61   friend struct DefaultLazyInstanceTraits<InotifyReader>;
  62
  63   typedef std::set<FilePathWatcherImpl*> WatcherSet;
  64
  65   InotifyReader();
  66   ~InotifyReader();
  67
  68   // We keep track of which delegates want to be notified on which watches.
  69   hash_map<Watch, WatcherSet> watchers_;
  70
  71   // Lock to protect watchers_.
  72   Lock lock_;
  73
  74   // Separate thread on which we run blocking read for inotify events.
  75   Thread thread_;
  76
  77   // File descriptor returned by inotify_init.
  78   const int inotify_fd_;
  79
  80   // Use self-pipe trick to unblock select during shutdown.
  81   int shutdown_pipe_[2];
  82
  83   // Flag set to true when startup was successful.
  84   bool valid_;
  85
  86   DISALLOW_COPY_AND_ASSIGN(InotifyReader);
  87 };
  88
  89 class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate,
  90                             public MessageLoop::DestructionObserver {
  91  public:
  92   FilePathWatcherImpl();
  93
  94   // Called for each event coming from the watch. |fired_watch| identifies the
  95   // watch that fired, |child| indicates what has changed, and is relative to
  96   // the currently watched path for |fired_watch|.
  97   //
  98   // |created| is true if the object appears.
  99   // |deleted| is true if the object disappears.
 100   // |is_dir| is true if the object is a directory.
 101   void OnFilePathChanged(InotifyReader::Watch fired_watch,
 102                          const FilePath::StringType& child,
 103                          bool created,
 104                          bool deleted,
 105                          bool is_dir);
 106
 107  protected:
 108   virtual ~FilePathWatcherImpl() {}
 109
 110  private:
 111   // Start watching |path| for changes and notify |delegate| on each change.
 112   // Returns true if watch for |path| has been added successfully.
 113   virtual bool Watch(const FilePath& path,
 114                      bool recursive,
 115                      const FilePathWatcher::Callback& callback) OVERRIDE;
 116
 117   // Cancel the watch. This unregisters the instance with InotifyReader.
 118   virtual void Cancel() OVERRIDE;
 119
 120   // Cleans up and stops observing the message_loop() thread.
 121   virtual void CancelOnMessageLoopThread() OVERRIDE;
 122
 123   // Deletion of the FilePathWatcher will call Cancel() to dispose of this
 124   // object in the right thread. This also observes destruction of the required
 125   // cleanup thread, in case it quits before Cancel() is called.
 126   virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
 127
 128   // Inotify watches are installed for all directory components of |target_|. A
 129   // WatchEntry instance holds the watch descriptor for a component and the
 130   // subdirectory for that identifies the next component. If a symbolic link
 131   // is being watched, the target of the link is also kept.
 132   struct WatchEntry {
 133     explicit WatchEntry(const FilePath::StringType& dirname)
 134         : watch(InotifyReader::kInvalidWatch),
 135           subdir(dirname) {}
 136
 137     InotifyReader::Watch watch;
 138     FilePath::StringType subdir;
 139     FilePath::StringType linkname;
 140   };
 141   typedef std::vector<WatchEntry> WatchVector;
 142
 143   // Reconfigure to watch for the most specific parent directory of |target_|
 144   // that exists. Also calls UpdateRecursiveWatches() below.
 145   void UpdateWatches();
 146
 147   // Reconfigure to recursively watch |target_| and all its sub-directories.
 148   // - This is a no-op if the watch is not recursive.
 149   // - If |target_| does not exist, then clear all the recursive watches.
 150   // - Assuming |target_| exists, passing kInvalidWatch as |fired_watch| forces
 151   //   addition of recursive watches for |target_|.
 152   // - Otherwise, only the directory associated with |fired_watch| and its
 153   //   sub-directories will be reconfigured.
 154   void UpdateRecursiveWatches(InotifyReader::Watch fired_watch, bool is_dir);
 155
 156   // Enumerate recursively through |path| and add / update watches.
 157   void UpdateRecursiveWatchesForPath(const FilePath& path);
 158
 159   // Do internal bookkeeping to update mappings between |watch| and its
 160   // associated full path |path|.
 161   void TrackWatchForRecursion(InotifyReader::Watch watch, const FilePath& path);
 162
 163   // Remove all the recursive watches.
 164   void RemoveRecursiveWatches();
 165
 166   // |path| is a symlink to a non-existent target. Attempt to add a watch to
 167   // the link target's parent directory. Returns true and update |watch_entry|
 168   // on success.
 169   bool AddWatchForBrokenSymlink(const FilePath& path, WatchEntry* watch_entry);
 170
 171   bool HasValidWatchVector() const;
 172
 173   // Callback to notify upon changes.
 174   FilePathWatcher::Callback callback_;
 175
 176   // The file or directory we're supposed to watch.
 177   FilePath target_;
 178
 179   bool recursive_;
 180
 181   // The vector of watches and next component names for all path components,
 182   // starting at the root directory. The last entry corresponds to the watch for
 183   // |target_| and always stores an empty next component name in |subdir|.
 184   WatchVector watches_;
 185
 186   hash_map<InotifyReader::Watch, FilePath> recursive_paths_by_watch_;
 187   std::map<FilePath, InotifyReader::Watch> recursive_watches_by_path_;
 188
 189   DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl);
 190 };
 191
 192 void InotifyReaderCallback(InotifyReader* reader, int inotify_fd,
 193                            int shutdown_fd) {
 194   // Make sure the file descriptors are good for use with select().
 195   CHECK_LE(0, inotify_fd);
 196   CHECK_GT(FD_SETSIZE, inotify_fd);
 197   CHECK_LE(0, shutdown_fd);
 198   CHECK_GT(FD_SETSIZE, shutdown_fd);
 199
 200   debug::TraceLog::GetInstance()->SetCurrentThreadBlocksMessageLoop();
 201
 202   while (true) {
 203     fd_set rfds;
 204     FD_ZERO(&rfds);
 205     FD_SET(inotify_fd, &rfds);
 206     FD_SET(shutdown_fd, &rfds);
 207
 208     // Wait until some inotify events are available.
 209     int select_result =
 210       HANDLE_EINTR(select(std::max(inotify_fd, shutdown_fd) + 1,
 211                           &rfds, NULL, NULL, NULL));
 212     if (select_result < 0) {
 213       DPLOG(WARNING) << "select failed";
 214       return;
 215     }
 216
 217     if (FD_ISSET(shutdown_fd, &rfds))
 218       return;
 219
 220     // Adjust buffer size to current event queue size.
 221     int buffer_size;
 222     int ioctl_result = HANDLE_EINTR(ioctl(inotify_fd, FIONREAD,
 223                                           &buffer_size));
 224
 225     if (ioctl_result != 0) {
 226       DPLOG(WARNING) << "ioctl failed";
 227       return;
 228     }
 229
 230     std::vector<char> buffer(buffer_size);
 231
 232     ssize_t bytes_read = HANDLE_EINTR(read(inotify_fd, &buffer[0],
 233                                            buffer_size));
 234
 235     if (bytes_read < 0) {
 236       DPLOG(WARNING) << "read from inotify fd failed";
 237       return;
 238     }
 239
 240     ssize_t i = 0;
 241     while (i < bytes_read) {
 242       inotify_event* event = reinterpret_cast<inotify_event*>(&buffer[i]);
 243       size_t event_size = sizeof(inotify_event) + event->len;
 244       DCHECK(i + event_size <= static_cast<size_t>(bytes_read));
 245       reader->OnInotifyEvent(event);
 246       i += event_size;
 247     }
 248   }
 249 }
 250
 251 static LazyInstance<InotifyReader>::Leaky g_inotify_reader =
 252     LAZY_INSTANCE_INITIALIZER;
 253
 254 InotifyReader::InotifyReader()
 255     : thread_("inotify_reader"),
 256       inotify_fd_(inotify_init()),
 257       valid_(false) {
 258   if (inotify_fd_ < 0)
 259     PLOG(ERROR) << "inotify_init() failed";
 260
 261   shutdown_pipe_[0] = -1;
 262   shutdown_pipe_[1] = -1;
 263   if (inotify_fd_ >= 0 && pipe(shutdown_pipe_) == 0 && thread_.Start()) {
 264     thread_.message_loop()->PostTask(
 265         FROM_HERE,
 266         Bind(&InotifyReaderCallback, this, inotify_fd_, shutdown_pipe_[0]));
 267     valid_ = true;
 268   }
 269 }
 270
 271 InotifyReader::~InotifyReader() {
 272   if (valid_) {
 273     // Write to the self-pipe so that the select call in InotifyReaderTask
 274     // returns.
 275     ssize_t ret = HANDLE_EINTR(write(shutdown_pipe_[1], "", 1));
 276     DPCHECK(ret > 0);
 277     DCHECK_EQ(ret, 1);
 278     thread_.Stop();
 279   }
 280   if (inotify_fd_ >= 0)
 281     close(inotify_fd_);
 282   if (shutdown_pipe_[0] >= 0)
 283     close(shutdown_pipe_[0]);
 284   if (shutdown_pipe_[1] >= 0)
 285     close(shutdown_pipe_[1]);
 286 }
 287
 288 InotifyReader::Watch InotifyReader::AddWatch(
 289     const FilePath& path, FilePathWatcherImpl* watcher) {
 290   if (!valid_)
 291     return kInvalidWatch;
 292
 293   AutoLock auto_lock(lock_);
 294
 295   Watch watch = inotify_add_watch(inotify_fd_, path.value().c_str(),
 296                                   IN_ATTRIB | IN_CREATE | IN_DELETE |
 297                                   IN_CLOSE_WRITE | IN_MOVE |
 298                                   IN_ONLYDIR);
 299
 300   if (watch == kInvalidWatch)
 301     return kInvalidWatch;
 302
 303   watchers_[watch].insert(watcher);
 304
 305   return watch;
 306 }
 307
 308 void InotifyReader::RemoveWatch(Watch watch, FilePathWatcherImpl* watcher) {
 309   if (!valid_ || (watch == kInvalidWatch))
 310     return;
 311
 312   AutoLock auto_lock(lock_);
 313
 314   watchers_[watch].erase(watcher);
 315
 316   if (watchers_[watch].empty()) {
 317     watchers_.erase(watch);
 318     inotify_rm_watch(inotify_fd_, watch);
 319   }
 320 }
 321
 322 void InotifyReader::OnInotifyEvent(const inotify_event* event) {
 323   if (event->mask & IN_IGNORED)
 324     return;
 325
 326   FilePath::StringType child(event->len ? event->name : FILE_PATH_LITERAL(""));
 327   AutoLock auto_lock(lock_);
 328
 329   for (WatcherSet::iterator watcher = watchers_[event->wd].begin();
 330        watcher != watchers_[event->wd].end();
 331        ++watcher) {
 332     (*watcher)->OnFilePathChanged(event->wd,
 333                                   child,
 334                                   event->mask & (IN_CREATE | IN_MOVED_TO),
 335                                   event->mask & (IN_DELETE | IN_MOVED_FROM),
 336                                   event->mask & IN_ISDIR);
 337   }
 338 }
 339
 340 FilePathWatcherImpl::FilePathWatcherImpl()
 341     : recursive_(false) {
 342 }
 343
 344 void FilePathWatcherImpl::OnFilePathChanged(InotifyReader::Watch fired_watch,
 345                                             const FilePath::StringType& child,
 346                                             bool created,
 347                                             bool deleted,
 348                                             bool is_dir) {
 349   if (!message_loop()->BelongsToCurrentThread()) {
 350     // Switch to message_loop() to access |watches_| safely.
 351     message_loop()->PostTask(
 352         FROM_HERE,
 353         Bind(&FilePathWatcherImpl::OnFilePathChanged, this,
 354              fired_watch, child, created, deleted, is_dir));
 355     return;
 356   }
 357
 358   // Check to see if CancelOnMessageLoopThread() has already been called.
 359   // May happen when code flow reaches here from the PostTask() above.
 360   if (watches_.empty()) {
 361     DCHECK(target_.empty());
 362     return;
 363   }
 364
 365   DCHECK(MessageLoopForIO::current());
 366   DCHECK(HasValidWatchVector());
 367
 368   // Used below to avoid multiple recursive updates.
 369   bool did_update = false;
 370
 371   // Find the entry in |watches_| that corresponds to |fired_watch|.
 372   for (size_t i = 0; i < watches_.size(); ++i) {
 373     const WatchEntry& watch_entry = watches_[i];
 374     if (fired_watch != watch_entry.watch)
 375       continue;
 376
 377     // Check whether a path component of |target_| changed.
 378     bool change_on_target_path =
 379         child.empty() ||
 380         (child == watch_entry.linkname) ||
 381         (child == watch_entry.subdir);
 382
 383     // Check if the change references |target_| or a direct child of |target_|.
 384     bool is_watch_for_target = watch_entry.subdir.empty();
 385     bool target_changed =
 386         (is_watch_for_target && (child == watch_entry.linkname)) ||
 387         (is_watch_for_target && watch_entry.linkname.empty()) ||
 388         (watch_entry.subdir == child && watches_[i + 1].subdir.empty());
 389
 390     // Update watches if a directory component of the |target_| path
 391     // (dis)appears. Note that we don't add the additional restriction of
 392     // checking the event mask to see if it is for a directory here as changes
 393     // to symlinks on the target path will not have IN_ISDIR set in the event
 394     // masks. As a result we may sometimes call UpdateWatches() unnecessarily.
 395     if (change_on_target_path && (created || deleted) && !did_update) {
 396       UpdateWatches();
 397       did_update = true;
 398     }
 399
 400     // Report the following events:
 401     //  - The target or a direct child of the target got changed (in case the
 402     //    watched path refers to a directory).
 403     //  - One of the parent directories got moved or deleted, since the target
 404     //    disappears in this case.
 405     //  - One of the parent directories appears. The event corresponding to
 406     //    the target appearing might have been missed in this case, so recheck.
 407     if (target_changed ||
 408         (change_on_target_path && deleted) ||
 409         (change_on_target_path && created && PathExists(target_))) {
 410       if (!did_update) {
 411         UpdateRecursiveWatches(fired_watch, is_dir);
 412         did_update = true;
 413       }
 414       callback_.Run(target_, false /* error */);
 415       return;
 416     }
 417   }
 418
 419   if (ContainsKey(recursive_paths_by_watch_, fired_watch)) {
 420     if (!did_update)
 421       UpdateRecursiveWatches(fired_watch, is_dir);
 422     callback_.Run(target_, false /* error */);
 423   }
 424 }
 425
 426 bool FilePathWatcherImpl::Watch(const FilePath& path,
 427                                 bool recursive,
 428                                 const FilePathWatcher::Callback& callback) {
 429   DCHECK(target_.empty());
 430   DCHECK(MessageLoopForIO::current());
 431
 432   set_message_loop(MessageLoopProxy::current().get());
 433   callback_ = callback;
 434   target_ = path;
 435   recursive_ = recursive;
 436   MessageLoop::current()->AddDestructionObserver(this);
 437
 438   std::vector<FilePath::StringType> comps;
 439   target_.GetComponents(&comps);
 440   DCHECK(!comps.empty());
 441   for (size_t i = 1; i < comps.size(); ++i)
 442     watches_.push_back(WatchEntry(comps[i]));
 443   watches_.push_back(WatchEntry(FilePath::StringType()));
 444   UpdateWatches();
 445   return true;
 446 }
 447
 448 void FilePathWatcherImpl::Cancel() {
 449   if (callback_.is_null()) {
 450     // Watch was never called, or the message_loop() thread is already gone.
 451     set_cancelled();
 452     return;
 453   }
 454
 455   // Switch to the message_loop() if necessary so we can access |watches_|.
 456   if (!message_loop()->BelongsToCurrentThread()) {
 457     message_loop()->PostTask(FROM_HERE,
 458                              Bind(&FilePathWatcher::CancelWatch,
 459                                   make_scoped_refptr(this)));
 460   } else {
 461     CancelOnMessageLoopThread();
 462   }
 463 }
 464
 465 void FilePathWatcherImpl::CancelOnMessageLoopThread() {
 466   DCHECK(message_loop()->BelongsToCurrentThread());
 467   set_cancelled();
 468
 469   if (!callback_.is_null()) {
 470     MessageLoop::current()->RemoveDestructionObserver(this);
 471     callback_.Reset();
 472   }
 473
 474   for (size_t i = 0; i < watches_.size(); ++i)
 475     g_inotify_reader.Get().RemoveWatch(watches_[i].watch, this);
 476   watches_.clear();
 477   target_.clear();
 478
 479   if (recursive_)
 480     RemoveRecursiveWatches();
 481 }
 482
 483 void FilePathWatcherImpl::WillDestroyCurrentMessageLoop() {
 484   CancelOnMessageLoopThread();
 485 }
 486
 487 void FilePathWatcherImpl::UpdateWatches() {
 488   // Ensure this runs on the message_loop() exclusively in order to avoid
 489   // concurrency issues.
 490   DCHECK(message_loop()->BelongsToCurrentThread());
 491   DCHECK(HasValidWatchVector());
 492
 493   // Walk the list of watches and update them as we go.
 494   FilePath path(FILE_PATH_LITERAL("/"));
 495   bool path_valid = true;
 496   for (size_t i = 0; i < watches_.size(); ++i) {
 497     WatchEntry& watch_entry = watches_[i];
 498     InotifyReader::Watch old_watch = watch_entry.watch;
 499     watch_entry.watch = InotifyReader::kInvalidWatch;
 500     watch_entry.linkname.clear();
 501     if (path_valid) {
 502       watch_entry.watch = g_inotify_reader.Get().AddWatch(path, this);
 503       if (watch_entry.watch == InotifyReader::kInvalidWatch) {
 504         if (IsLink(path)) {
 505           path_valid = AddWatchForBrokenSymlink(path, &watch_entry);
 506         } else {
 507           path_valid = false;
 508         }
 509       }
 510     }
 511     if (old_watch != watch_entry.watch)
 512       g_inotify_reader.Get().RemoveWatch(old_watch, this);
 513     path = path.Append(watch_entry.subdir);
 514   }
 515
 516   UpdateRecursiveWatches(InotifyReader::kInvalidWatch,
 517                          false /* is directory? */);
 518 }
 519
 520 void FilePathWatcherImpl::UpdateRecursiveWatches(
 521     InotifyReader::Watch fired_watch,
 522     bool is_dir) {
 523   if (!recursive_)
 524     return;
 525
 526   if (!DirectoryExists(target_)) {
 527     RemoveRecursiveWatches();
 528     return;
 529   }
 530
 531   // Check to see if this is a forced update or if some component of |target_|
 532   // has changed. For these cases, redo the watches for |target_| and below.
 533   if (!ContainsKey(recursive_paths_by_watch_, fired_watch)) {
 534     UpdateRecursiveWatchesForPath(target_);
 535     return;
 536   }
 537
 538   // Underneath |target_|, only directory changes trigger watch updates.
 539   if (!is_dir)
 540     return;
 541
 542   const FilePath& changed_dir = recursive_paths_by_watch_[fired_watch];
 543
 544   std::map<FilePath, InotifyReader::Watch>::iterator start_it =
 545       recursive_watches_by_path_.lower_bound(changed_dir);
 546   std::map<FilePath, InotifyReader::Watch>::iterator end_it = start_it;
 547   for (; end_it != recursive_watches_by_path_.end(); ++end_it) {
 548     const FilePath& cur_path = end_it->first;
 549     if (!changed_dir.IsParent(cur_path))
 550       break;
 551     if (!DirectoryExists(cur_path))
 552       g_inotify_reader.Get().RemoveWatch(end_it->second, this);
 553   }
 554   recursive_watches_by_path_.erase(start_it, end_it);
 555   UpdateRecursiveWatchesForPath(changed_dir);
 556 }
 557
 558 void FilePathWatcherImpl::UpdateRecursiveWatchesForPath(const FilePath& path) {
 559   DCHECK(recursive_);
 560   DCHECK(!path.empty());
 561   DCHECK(DirectoryExists(path));
 562
 563   // Note: SHOW_SYM_LINKS exposes symlinks as symlinks, so they are ignored
 564   // rather than followed. Following symlinks can easily lead to the undesirable
 565   // situation where the entire file system is being watched.
 566   FileEnumerator enumerator(
 567       path,
 568       true /* recursive enumeration */,
 569       FileEnumerator::DIRECTORIES | FileEnumerator::SHOW_SYM_LINKS);
 570   for (FilePath current = enumerator.Next();
 571        !current.empty();
 572        current = enumerator.Next()) {
 573     DCHECK(enumerator.GetInfo().IsDirectory());
 574
 575     if (!ContainsKey(recursive_watches_by_path_, current)) {
 576       // Add new watches.
 577       InotifyReader::Watch watch =
 578           g_inotify_reader.Get().AddWatch(current, this);
 579       TrackWatchForRecursion(watch, current);
 580     } else {
 581       // Update existing watches.
 582       InotifyReader::Watch old_watch = recursive_watches_by_path_[current];
 583       DCHECK_NE(InotifyReader::kInvalidWatch, old_watch);
 584       InotifyReader::Watch watch =
 585           g_inotify_reader.Get().AddWatch(current, this);
 586       if (watch != old_watch) {
 587         g_inotify_reader.Get().RemoveWatch(old_watch, this);
 588         recursive_paths_by_watch_.erase(old_watch);
 589         recursive_watches_by_path_.erase(current);
 590         TrackWatchForRecursion(watch, current);
 591       }
 592     }
 593   }
 594 }
 595
 596 void FilePathWatcherImpl::TrackWatchForRecursion(InotifyReader::Watch watch,
 597                                                  const FilePath& path) {
 598   DCHECK(recursive_);
 599   DCHECK(!path.empty());
 600   DCHECK(target_.IsParent(path));
 601
 602   if (watch == InotifyReader::kInvalidWatch)
 603     return;
 604
 605   DCHECK(!ContainsKey(recursive_paths_by_watch_, watch));
 606   DCHECK(!ContainsKey(recursive_watches_by_path_, path));
 607   recursive_paths_by_watch_[watch] = path;
 608   recursive_watches_by_path_[path] = watch;
 609 }
 610
 611 void FilePathWatcherImpl::RemoveRecursiveWatches() {
 612   if (!recursive_)
 613     return;
 614
 615   for (hash_map<InotifyReader::Watch, FilePath>::const_iterator it =
 616            recursive_paths_by_watch_.begin();
 617        it != recursive_paths_by_watch_.end();
 618        ++it) {
 619     g_inotify_reader.Get().RemoveWatch(it->first, this);
 620   }
 621   recursive_paths_by_watch_.clear();
 622   recursive_watches_by_path_.clear();
 623 }
 624
 625 bool FilePathWatcherImpl::AddWatchForBrokenSymlink(const FilePath& path,
 626                                                    WatchEntry* watch_entry) {
 627   DCHECK_EQ(InotifyReader::kInvalidWatch, watch_entry->watch);
 628   FilePath link;
 629   if (!ReadSymbolicLink(path, &link))
 630     return false;
 631
 632   if (!link.IsAbsolute())
 633     link = path.DirName().Append(link);
 634
 635   // Try watching symlink target directory. If the link target is "/", then we
 636   // shouldn't get here in normal situations and if we do, we'd watch "/" for
 637   // changes to a component "/" which is harmless so no special treatment of
 638   // this case is required.
 639   InotifyReader::Watch watch =
 640       g_inotify_reader.Get().AddWatch(link.DirName(), this);
 641   if (watch == InotifyReader::kInvalidWatch) {
 642     // TODO(craig) Symlinks only work if the parent directory for the target
 643     // exist. Ideally we should make sure we've watched all the components of
 644     // the symlink path for changes. See crbug.com/91561 for details.
 645     DPLOG(WARNING) << "Watch failed for "  << link.DirName().value();
 646     return false;
 647   }
 648   watch_entry->watch = watch;
 649   watch_entry->linkname = link.BaseName().value();
 650   return true;
 651 }
 652
 653 bool FilePathWatcherImpl::HasValidWatchVector() const {
 654   if (watches_.empty())
 655     return false;
 656   for (size_t i = 0; i < watches_.size() - 1; ++i) {
 657     if (watches_[i].subdir.empty())
 658       return false;
 659   }
 660   return watches_[watches_.size() - 1].subdir.empty();
 661 }
 662
 663 }  // namespace
 664
 665 FilePathWatcher::FilePathWatcher() {
 666   impl_ = new FilePathWatcherImpl();
 667 }
 668
 669 }  // namespace base