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/files/file_enumerator.h"
  23 #include "base/files/file_path.h"
  24 #include "base/files/file_util.h"
  25 #include "base/lazy_instance.h"
  26 #include "base/location.h"
  27 #include "base/logging.h"
  28 #include "base/memory/scoped_ptr.h"
  29 #include "base/message_loop/message_loop.h"
  30 #include "base/message_loop/message_loop_proxy.h"
  31 #include "base/posix/eintr_wrapper.h"
  32 #include "base/synchronization/lock.h"
  33 #include "base/threading/thread.h"
  34 #include "base/trace_event/trace_event.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   ~FilePathWatcherImpl() override {}
 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   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   void Cancel() override;
 119
 120   // Cleans up and stops observing the message_loop() thread.
 121   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   void WillDestroyCurrentMessageLoop() override;
 127
 128   // Inotify watches are installed for all directory components of |target_|.
 129   // A WatchEntry instance holds:
 130   // - |watch|: the watch descriptor for a component.
 131   // - |subdir|: the subdirectory that identifies the next component.
 132   //   - For the last component, there is no next component, so it is empty.
 133   // - |linkname|: the target of the symlink.
 134   //   - Only if the target being watched is a symbolic link.
 135   struct WatchEntry {
 136     explicit WatchEntry(const FilePath::StringType& dirname)
 137         : watch(InotifyReader::kInvalidWatch),
 138           subdir(dirname) {}
 139
 140     InotifyReader::Watch watch;
 141     FilePath::StringType subdir;
 142     FilePath::StringType linkname;
 143   };
 144   typedef std::vector<WatchEntry> WatchVector;
 145
 146   // Reconfigure to watch for the most specific parent directory of |target_|
 147   // that exists. Also calls UpdateRecursiveWatches() below.
 148   void UpdateWatches();
 149
 150   // Reconfigure to recursively watch |target_| and all its sub-directories.
 151   // - This is a no-op if the watch is not recursive.
 152   // - If |target_| does not exist, then clear all the recursive watches.
 153   // - Assuming |target_| exists, passing kInvalidWatch as |fired_watch| forces
 154   //   addition of recursive watches for |target_|.
 155   // - Otherwise, only the directory associated with |fired_watch| and its
 156   //   sub-directories will be reconfigured.
 157   void UpdateRecursiveWatches(InotifyReader::Watch fired_watch, bool is_dir);
 158
 159   // Enumerate recursively through |path| and add / update watches.
 160   void UpdateRecursiveWatchesForPath(const FilePath& path);
 161
 162   // Do internal bookkeeping to update mappings between |watch| and its
 163   // associated full path |path|.
 164   void TrackWatchForRecursion(InotifyReader::Watch watch, const FilePath& path);
 165
 166   // Remove all the recursive watches.
 167   void RemoveRecursiveWatches();
 168
 169   // |path| is a symlink to a non-existent target. Attempt to add a watch to
 170   // the link target's parent directory. Returns true and update |watch_entry|
 171   // on success.
 172   bool AddWatchForBrokenSymlink(const FilePath& path, WatchEntry* watch_entry);
 173
 174   bool HasValidWatchVector() const;
 175
 176   // Callback to notify upon changes.
 177   FilePathWatcher::Callback callback_;
 178
 179   // The file or directory we're supposed to watch.
 180   FilePath target_;
 181
 182   bool recursive_;
 183
 184   // The vector of watches and next component names for all path components,
 185   // starting at the root directory. The last entry corresponds to the watch for
 186   // |target_| and always stores an empty next component name in |subdir|.
 187   WatchVector watches_;
 188
 189   hash_map<InotifyReader::Watch, FilePath> recursive_paths_by_watch_;
 190   std::map<FilePath, InotifyReader::Watch> recursive_watches_by_path_;
 191
 192   DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl);
 193 };
 194
 195 void InotifyReaderCallback(InotifyReader* reader, int inotify_fd,
 196                            int shutdown_fd) {
 197   // Make sure the file descriptors are good for use with select().
 198   CHECK_LE(0, inotify_fd);
 199   CHECK_GT(FD_SETSIZE, inotify_fd);
 200   CHECK_LE(0, shutdown_fd);
 201   CHECK_GT(FD_SETSIZE, shutdown_fd);
 202
 203   trace_event::TraceLog::GetInstance()->SetCurrentThreadBlocksMessageLoop();
 204
 205   while (true) {
 206     fd_set rfds;
 207     FD_ZERO(&rfds);
 208     FD_SET(inotify_fd, &rfds);
 209     FD_SET(shutdown_fd, &rfds);
 210
 211     // Wait until some inotify events are available.
 212     int select_result =
 213       HANDLE_EINTR(select(std::max(inotify_fd, shutdown_fd) + 1,
 214                           &rfds, NULL, NULL, NULL));
 215     if (select_result < 0) {
 216       DPLOG(WARNING) << "select failed";
 217       return;
 218     }
 219
 220     if (FD_ISSET(shutdown_fd, &rfds))
 221       return;
 222
 223     // Adjust buffer size to current event queue size.
 224     int buffer_size;
 225     int ioctl_result = HANDLE_EINTR(ioctl(inotify_fd, FIONREAD,
 226                                           &buffer_size));
 227
 228     if (ioctl_result != 0) {
 229       DPLOG(WARNING) << "ioctl failed";
 230       return;
 231     }
 232
 233     std::vector<char> buffer(buffer_size);
 234
 235     ssize_t bytes_read = HANDLE_EINTR(read(inotify_fd, &buffer[0],
 236                                            buffer_size));
 237
 238     if (bytes_read < 0) {
 239       DPLOG(WARNING) << "read from inotify fd failed";
 240       return;
 241     }
 242
 243     ssize_t i = 0;
 244     while (i < bytes_read) {
 245       inotify_event* event = reinterpret_cast<inotify_event*>(&buffer[i]);
 246       size_t event_size = sizeof(inotify_event) + event->len;
 247       DCHECK(i + event_size <= static_cast<size_t>(bytes_read));
 248       reader->OnInotifyEvent(event);
 249       i += event_size;
 250     }
 251   }
 252 }
 253
 254 static LazyInstance<InotifyReader>::Leaky g_inotify_reader =
 255     LAZY_INSTANCE_INITIALIZER;
 256
 257 InotifyReader::InotifyReader()
 258     : thread_("inotify_reader"),
 259       inotify_fd_(inotify_init()),
 260       valid_(false) {
 261   if (inotify_fd_ < 0)
 262     PLOG(ERROR) << "inotify_init() failed";
 263
 264   shutdown_pipe_[0] = -1;
 265   shutdown_pipe_[1] = -1;
 266   if (inotify_fd_ >= 0 && pipe(shutdown_pipe_) == 0 && thread_.Start()) {
 267     thread_.message_loop()->PostTask(
 268         FROM_HERE,
 269         Bind(&InotifyReaderCallback, this, inotify_fd_, shutdown_pipe_[0]));
 270     valid_ = true;
 271   }
 272 }
 273
 274 InotifyReader::~InotifyReader() {
 275   if (valid_) {
 276     // Write to the self-pipe so that the select call in InotifyReaderTask
 277     // returns.
 278     ssize_t ret = HANDLE_EINTR(write(shutdown_pipe_[1], "", 1));
 279     DPCHECK(ret > 0);
 280     DCHECK_EQ(ret, 1);
 281     thread_.Stop();
 282   }
 283   if (inotify_fd_ >= 0)
 284     close(inotify_fd_);
 285   if (shutdown_pipe_[0] >= 0)
 286     close(shutdown_pipe_[0]);
 287   if (shutdown_pipe_[1] >= 0)
 288     close(shutdown_pipe_[1]);
 289 }
 290
 291 InotifyReader::Watch InotifyReader::AddWatch(
 292     const FilePath& path, FilePathWatcherImpl* watcher) {
 293   if (!valid_)
 294     return kInvalidWatch;
 295
 296   AutoLock auto_lock(lock_);
 297
 298   Watch watch = inotify_add_watch(inotify_fd_, path.value().c_str(),
 299                                   IN_ATTRIB | IN_CREATE | IN_DELETE |
 300                                   IN_CLOSE_WRITE | IN_MOVE |
 301                                   IN_ONLYDIR);
 302
 303   if (watch == kInvalidWatch)
 304     return kInvalidWatch;
 305
 306   watchers_[watch].insert(watcher);
 307
 308   return watch;
 309 }
 310
 311 void InotifyReader::RemoveWatch(Watch watch, FilePathWatcherImpl* watcher) {
 312   if (!valid_ || (watch == kInvalidWatch))
 313     return;
 314
 315   AutoLock auto_lock(lock_);
 316
 317   watchers_[watch].erase(watcher);
 318
 319   if (watchers_[watch].empty()) {
 320     watchers_.erase(watch);
 321     inotify_rm_watch(inotify_fd_, watch);
 322   }
 323 }
 324
 325 void InotifyReader::OnInotifyEvent(const inotify_event* event) {
 326   if (event->mask & IN_IGNORED)
 327     return;
 328
 329   FilePath::StringType child(event->len ? event->name : FILE_PATH_LITERAL(""));
 330   AutoLock auto_lock(lock_);
 331
 332   for (WatcherSet::iterator watcher = watchers_[event->wd].begin();
 333        watcher != watchers_[event->wd].end();
 334        ++watcher) {
 335     (*watcher)->OnFilePathChanged(event->wd,
 336                                   child,
 337                                   event->mask & (IN_CREATE | IN_MOVED_TO),
 338                                   event->mask & (IN_DELETE | IN_MOVED_FROM),
 339                                   event->mask & IN_ISDIR);
 340   }
 341 }
 342
 343 FilePathWatcherImpl::FilePathWatcherImpl()
 344     : recursive_(false) {
 345 }
 346
 347 void FilePathWatcherImpl::OnFilePathChanged(InotifyReader::Watch fired_watch,
 348                                             const FilePath::StringType& child,
 349                                             bool created,
 350                                             bool deleted,
 351                                             bool is_dir) {
 352   if (!message_loop()->BelongsToCurrentThread()) {
 353     // Switch to message_loop() to access |watches_| safely.
 354     message_loop()->PostTask(
 355         FROM_HERE,
 356         Bind(&FilePathWatcherImpl::OnFilePathChanged, this,
 357              fired_watch, child, created, deleted, is_dir));
 358     return;
 359   }
 360
 361   // Check to see if CancelOnMessageLoopThread() has already been called.
 362   // May happen when code flow reaches here from the PostTask() above.
 363   if (watches_.empty()) {
 364     DCHECK(target_.empty());
 365     return;
 366   }
 367
 368   DCHECK(MessageLoopForIO::current());
 369   DCHECK(HasValidWatchVector());
 370
 371   // Used below to avoid multiple recursive updates.
 372   bool did_update = false;
 373
 374   // Find the entry in |watches_| that corresponds to |fired_watch|.
 375   for (size_t i = 0; i < watches_.size(); ++i) {
 376     const WatchEntry& watch_entry = watches_[i];
 377     if (fired_watch != watch_entry.watch)
 378       continue;
 379
 380     // Check whether a path component of |target_| changed.
 381     bool change_on_target_path =
 382         child.empty() ||
 383         (child == watch_entry.linkname) ||
 384         (child == watch_entry.subdir);
 385
 386     // Check if the change references |target_| or a direct child of |target_|.
 387     bool target_changed;
 388     if (watch_entry.subdir.empty()) {
 389       // The fired watch is for a WatchEntry without a subdir. Thus for a given
 390       // |target_| = "/path/to/foo", this is for "foo". Here, check either:
 391       // - the target has no symlink: it is the target and it changed.
 392       // - the target has a symlink, and it matches |child|.
 393       target_changed = (watch_entry.linkname.empty() ||
 394                         child == watch_entry.linkname);
 395     } else {
 396       // The fired watch is for a WatchEntry with a subdir. Thus for a given
 397       // |target_| = "/path/to/foo", this is for {"/", "/path", "/path/to"}.
 398       // So we can safely access the next WatchEntry since we have not reached
 399       // the end yet. Check |watch_entry| is for "/path/to", i.e. the next
 400       // element is "foo".
 401       bool next_watch_may_be_for_target = watches_[i + 1].subdir.empty();
 402       if (next_watch_may_be_for_target) {
 403         // The current |watch_entry| is for "/path/to", so check if the |child|
 404         // that changed is "foo".
 405         target_changed = watch_entry.subdir == child;
 406       } else {
 407         // The current |watch_entry| is not for "/path/to", so the next entry
 408         // cannot be "foo". Thus |target_| has not changed.
 409         target_changed = false;
 410       }
 411     }
 412
 413     // Update watches if a directory component of the |target_| path
 414     // (dis)appears. Note that we don't add the additional restriction of
 415     // checking the event mask to see if it is for a directory here as changes
 416     // to symlinks on the target path will not have IN_ISDIR set in the event
 417     // masks. As a result we may sometimes call UpdateWatches() unnecessarily.
 418     if (change_on_target_path && (created || deleted) && !did_update) {
 419       UpdateWatches();
 420       did_update = true;
 421     }
 422
 423     // Report the following events:
 424     //  - The target or a direct child of the target got changed (in case the
 425     //    watched path refers to a directory).
 426     //  - One of the parent directories got moved or deleted, since the target
 427     //    disappears in this case.
 428     //  - One of the parent directories appears. The event corresponding to
 429     //    the target appearing might have been missed in this case, so recheck.
 430     if (target_changed ||
 431         (change_on_target_path && deleted) ||
 432         (change_on_target_path && created && PathExists(target_))) {
 433       if (!did_update) {
 434         UpdateRecursiveWatches(fired_watch, is_dir);
 435         did_update = true;
 436       }
 437       callback_.Run(target_, false /* error */);
 438       return;
 439     }
 440   }
 441
 442   if (ContainsKey(recursive_paths_by_watch_, fired_watch)) {
 443     if (!did_update)
 444       UpdateRecursiveWatches(fired_watch, is_dir);
 445     callback_.Run(target_, false /* error */);
 446   }
 447 }
 448
 449 bool FilePathWatcherImpl::Watch(const FilePath& path,
 450                                 bool recursive,
 451                                 const FilePathWatcher::Callback& callback) {
 452   DCHECK(target_.empty());
 453   DCHECK(MessageLoopForIO::current());
 454
 455   set_message_loop(MessageLoopProxy::current());
 456   callback_ = callback;
 457   target_ = path;
 458   recursive_ = recursive;
 459   MessageLoop::current()->AddDestructionObserver(this);
 460
 461   std::vector<FilePath::StringType> comps;
 462   target_.GetComponents(&comps);
 463   DCHECK(!comps.empty());
 464   for (size_t i = 1; i < comps.size(); ++i)
 465     watches_.push_back(WatchEntry(comps[i]));
 466   watches_.push_back(WatchEntry(FilePath::StringType()));
 467   UpdateWatches();
 468   return true;
 469 }
 470
 471 void FilePathWatcherImpl::Cancel() {
 472   if (callback_.is_null()) {
 473     // Watch was never called, or the message_loop() thread is already gone.
 474     set_cancelled();
 475     return;
 476   }
 477
 478   // Switch to the message_loop() if necessary so we can access |watches_|.
 479   if (!message_loop()->BelongsToCurrentThread()) {
 480     message_loop()->PostTask(FROM_HERE,
 481                              Bind(&FilePathWatcher::CancelWatch,
 482                                   make_scoped_refptr(this)));
 483   } else {
 484     CancelOnMessageLoopThread();
 485   }
 486 }
 487
 488 void FilePathWatcherImpl::CancelOnMessageLoopThread() {
 489   DCHECK(message_loop()->BelongsToCurrentThread());
 490   set_cancelled();
 491
 492   if (!callback_.is_null()) {
 493     MessageLoop::current()->RemoveDestructionObserver(this);
 494     callback_.Reset();
 495   }
 496
 497   for (size_t i = 0; i < watches_.size(); ++i)
 498     g_inotify_reader.Get().RemoveWatch(watches_[i].watch, this);
 499   watches_.clear();
 500   target_.clear();
 501
 502   if (recursive_)
 503     RemoveRecursiveWatches();
 504 }
 505
 506 void FilePathWatcherImpl::WillDestroyCurrentMessageLoop() {
 507   CancelOnMessageLoopThread();
 508 }
 509
 510 void FilePathWatcherImpl::UpdateWatches() {
 511   // Ensure this runs on the message_loop() exclusively in order to avoid
 512   // concurrency issues.
 513   DCHECK(message_loop()->BelongsToCurrentThread());
 514   DCHECK(HasValidWatchVector());
 515
 516   // Walk the list of watches and update them as we go.
 517   FilePath path(FILE_PATH_LITERAL("/"));
 518   bool path_valid = true;
 519   for (size_t i = 0; i < watches_.size(); ++i) {
 520     WatchEntry& watch_entry = watches_[i];
 521     InotifyReader::Watch old_watch = watch_entry.watch;
 522     watch_entry.watch = InotifyReader::kInvalidWatch;
 523     watch_entry.linkname.clear();
 524     if (path_valid) {
 525       watch_entry.watch = g_inotify_reader.Get().AddWatch(path, this);
 526       if (watch_entry.watch == InotifyReader::kInvalidWatch) {
 527         if (IsLink(path)) {
 528           path_valid = AddWatchForBrokenSymlink(path, &watch_entry);
 529         } else {
 530           path_valid = false;
 531         }
 532       }
 533     }
 534     if (old_watch != watch_entry.watch)
 535       g_inotify_reader.Get().RemoveWatch(old_watch, this);
 536     path = path.Append(watch_entry.subdir);
 537   }
 538
 539   UpdateRecursiveWatches(InotifyReader::kInvalidWatch,
 540                          false /* is directory? */);
 541 }
 542
 543 void FilePathWatcherImpl::UpdateRecursiveWatches(
 544     InotifyReader::Watch fired_watch,
 545     bool is_dir) {
 546   if (!recursive_)
 547     return;
 548
 549   if (!DirectoryExists(target_)) {
 550     RemoveRecursiveWatches();
 551     return;
 552   }
 553
 554   // Check to see if this is a forced update or if some component of |target_|
 555   // has changed. For these cases, redo the watches for |target_| and below.
 556   if (!ContainsKey(recursive_paths_by_watch_, fired_watch)) {
 557     UpdateRecursiveWatchesForPath(target_);
 558     return;
 559   }
 560
 561   // Underneath |target_|, only directory changes trigger watch updates.
 562   if (!is_dir)
 563     return;
 564
 565   const FilePath& changed_dir = recursive_paths_by_watch_[fired_watch];
 566
 567   std::map<FilePath, InotifyReader::Watch>::iterator start_it =
 568       recursive_watches_by_path_.lower_bound(changed_dir);
 569   std::map<FilePath, InotifyReader::Watch>::iterator end_it = start_it;
 570   for (; end_it != recursive_watches_by_path_.end(); ++end_it) {
 571     const FilePath& cur_path = end_it->first;
 572     if (!changed_dir.IsParent(cur_path))
 573       break;
 574     if (!DirectoryExists(cur_path))
 575       g_inotify_reader.Get().RemoveWatch(end_it->second, this);
 576   }
 577   recursive_watches_by_path_.erase(start_it, end_it);
 578   UpdateRecursiveWatchesForPath(changed_dir);
 579 }
 580
 581 void FilePathWatcherImpl::UpdateRecursiveWatchesForPath(const FilePath& path) {
 582   DCHECK(recursive_);
 583   DCHECK(!path.empty());
 584   DCHECK(DirectoryExists(path));
 585
 586   // Note: SHOW_SYM_LINKS exposes symlinks as symlinks, so they are ignored
 587   // rather than followed. Following symlinks can easily lead to the undesirable
 588   // situation where the entire file system is being watched.
 589   FileEnumerator enumerator(
 590       path,
 591       true /* recursive enumeration */,
 592       FileEnumerator::DIRECTORIES | FileEnumerator::SHOW_SYM_LINKS);
 593   for (FilePath current = enumerator.Next();
 594        !current.empty();
 595        current = enumerator.Next()) {
 596     DCHECK(enumerator.GetInfo().IsDirectory());
 597
 598     if (!ContainsKey(recursive_watches_by_path_, current)) {
 599       // Add new watches.
 600       InotifyReader::Watch watch =
 601           g_inotify_reader.Get().AddWatch(current, this);
 602       TrackWatchForRecursion(watch, current);
 603     } else {
 604       // Update existing watches.
 605       InotifyReader::Watch old_watch = recursive_watches_by_path_[current];
 606       DCHECK_NE(InotifyReader::kInvalidWatch, old_watch);
 607       InotifyReader::Watch watch =
 608           g_inotify_reader.Get().AddWatch(current, this);
 609       if (watch != old_watch) {
 610         g_inotify_reader.Get().RemoveWatch(old_watch, this);
 611         recursive_paths_by_watch_.erase(old_watch);
 612         recursive_watches_by_path_.erase(current);
 613         TrackWatchForRecursion(watch, current);
 614       }
 615     }
 616   }
 617 }
 618
 619 void FilePathWatcherImpl::TrackWatchForRecursion(InotifyReader::Watch watch,
 620                                                  const FilePath& path) {
 621   DCHECK(recursive_);
 622   DCHECK(!path.empty());
 623   DCHECK(target_.IsParent(path));
 624
 625   if (watch == InotifyReader::kInvalidWatch)
 626     return;
 627
 628   DCHECK(!ContainsKey(recursive_paths_by_watch_, watch));
 629   DCHECK(!ContainsKey(recursive_watches_by_path_, path));
 630   recursive_paths_by_watch_[watch] = path;
 631   recursive_watches_by_path_[path] = watch;
 632 }
 633
 634 void FilePathWatcherImpl::RemoveRecursiveWatches() {
 635   if (!recursive_)
 636     return;
 637
 638   for (hash_map<InotifyReader::Watch, FilePath>::const_iterator it =
 639            recursive_paths_by_watch_.begin();
 640        it != recursive_paths_by_watch_.end();
 641        ++it) {
 642     g_inotify_reader.Get().RemoveWatch(it->first, this);
 643   }
 644   recursive_paths_by_watch_.clear();
 645   recursive_watches_by_path_.clear();
 646 }
 647
 648 bool FilePathWatcherImpl::AddWatchForBrokenSymlink(const FilePath& path,
 649                                                    WatchEntry* watch_entry) {
 650   DCHECK_EQ(InotifyReader::kInvalidWatch, watch_entry->watch);
 651   FilePath link;
 652   if (!ReadSymbolicLink(path, &link))
 653     return false;
 654
 655   if (!link.IsAbsolute())
 656     link = path.DirName().Append(link);
 657
 658   // Try watching symlink target directory. If the link target is "/", then we
 659   // shouldn't get here in normal situations and if we do, we'd watch "/" for
 660   // changes to a component "/" which is harmless so no special treatment of
 661   // this case is required.
 662   InotifyReader::Watch watch =
 663       g_inotify_reader.Get().AddWatch(link.DirName(), this);
 664   if (watch == InotifyReader::kInvalidWatch) {
 665     // TODO(craig) Symlinks only work if the parent directory for the target
 666     // exist. Ideally we should make sure we've watched all the components of
 667     // the symlink path for changes. See crbug.com/91561 for details.
 668     DPLOG(WARNING) << "Watch failed for "  << link.DirName().value();
 669     return false;
 670   }
 671   watch_entry->watch = watch;
 672   watch_entry->linkname = link.BaseName().value();
 673   return true;
 674 }
 675
 676 bool FilePathWatcherImpl::HasValidWatchVector() const {
 677   if (watches_.empty())
 678     return false;
 679   for (size_t i = 0; i < watches_.size() - 1; ++i) {
 680     if (watches_[i].subdir.empty())
 681       return false;
 682   }
 683   return watches_[watches_.size() - 1].subdir.empty();
 684 }
 685
 686 }  // namespace
 687
 688 FilePathWatcher::FilePathWatcher() {
 689   impl_ = new FilePathWatcherImpl();
 690 }
 691
 692 }  // namespace base