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      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/file_util.h"
     24 #include "base/files/file_enumerator.h"
     25 #include "base/files/file_path.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
    670