// Copyright (c) 2012 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #include "base/files/file_path_watcher.h" #include <errno.h> #include <stddef.h> #include <string.h> #include <sys/inotify.h> #include <sys/ioctl.h> #include <sys/select.h> #include <unistd.h> #include <algorithm> #include <map> #include <set> #include <utility> #include <vector> #include "base/bind.h" #include "base/containers/hash_tables.h" #include "base/files/file_enumerator.h" #include "base/files/file_path.h" #include "base/files/file_util.h" #include "base/lazy_instance.h" #include "base/location.h" #include "base/logging.h" #include "base/macros.h" #include "base/memory/scoped_ptr.h" #include "base/posix/eintr_wrapper.h" #include "base/single_thread_task_runner.h" #include "base/stl_util.h" #include "base/synchronization/lock.h" #include "base/thread_task_runner_handle.h" #include "base/threading/thread.h" #include "base/trace_event/trace_event.h" namespace base { namespace { class FilePathWatcherImpl; // Singleton to manage all inotify watches. // TODO(tony): It would be nice if this wasn't a singleton. // http://crbug.com/38174 class InotifyReader { public: typedef int Watch; // Watch descriptor used by AddWatch and RemoveWatch. static const Watch kInvalidWatch = -1; // Watch directory |path| for changes. |watcher| will be notified on each // change. Returns kInvalidWatch on failure. Watch AddWatch(const FilePath& path, FilePathWatcherImpl* watcher); // Remove |watch| if it's valid. void RemoveWatch(Watch watch, FilePathWatcherImpl* watcher); // Callback for InotifyReaderTask. void OnInotifyEvent(const inotify_event* event); private: friend struct DefaultLazyInstanceTraits<InotifyReader>; typedef std::set<FilePathWatcherImpl*> WatcherSet; InotifyReader(); ~InotifyReader(); // We keep track of which delegates want to be notified on which watches. hash_map<Watch, WatcherSet> watchers_; // Lock to protect watchers_. Lock lock_; // Separate thread on which we run blocking read for inotify events. Thread thread_; // File descriptor returned by inotify_init. const int inotify_fd_; // Use self-pipe trick to unblock select during shutdown. int shutdown_pipe_[2]; // Flag set to true when startup was successful. bool valid_; DISALLOW_COPY_AND_ASSIGN(InotifyReader); }; class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate, public MessageLoop::DestructionObserver { public: FilePathWatcherImpl(); // Called for each event coming from the watch. |fired_watch| identifies the // watch that fired, |child| indicates what has changed, and is relative to // the currently watched path for |fired_watch|. // // |created| is true if the object appears. // |deleted| is true if the object disappears. // |is_dir| is true if the object is a directory. void OnFilePathChanged(InotifyReader::Watch fired_watch, const FilePath::StringType& child, bool created, bool deleted, bool is_dir); protected: ~FilePathWatcherImpl() override {} private: // Start watching |path| for changes and notify |delegate| on each change. // Returns true if watch for |path| has been added successfully. bool Watch(const FilePath& path, bool recursive, const FilePathWatcher::Callback& callback) override; // Cancel the watch. This unregisters the instance with InotifyReader. void Cancel() override; // Cleans up and stops observing the message_loop() thread. void CancelOnMessageLoopThread() override; // Deletion of the FilePathWatcher will call Cancel() to dispose of this // object in the right thread. This also observes destruction of the required // cleanup thread, in case it quits before Cancel() is called. void WillDestroyCurrentMessageLoop() override; // Inotify watches are installed for all directory components of |target_|. // A WatchEntry instance holds: // - |watch|: the watch descriptor for a component. // - |subdir|: the subdirectory that identifies the next component. // - For the last component, there is no next component, so it is empty. // - |linkname|: the target of the symlink. // - Only if the target being watched is a symbolic link. struct WatchEntry { explicit WatchEntry(const FilePath::StringType& dirname) : watch(InotifyReader::kInvalidWatch), subdir(dirname) {} InotifyReader::Watch watch; FilePath::StringType subdir; FilePath::StringType linkname; }; typedef std::vector<WatchEntry> WatchVector; // Reconfigure to watch for the most specific parent directory of |target_| // that exists. Also calls UpdateRecursiveWatches() below. void UpdateWatches(); // Reconfigure to recursively watch |target_| and all its sub-directories. // - This is a no-op if the watch is not recursive. // - If |target_| does not exist, then clear all the recursive watches. // - Assuming |target_| exists, passing kInvalidWatch as |fired_watch| forces // addition of recursive watches for |target_|. // - Otherwise, only the directory associated with |fired_watch| and its // sub-directories will be reconfigured. void UpdateRecursiveWatches(InotifyReader::Watch fired_watch, bool is_dir); // Enumerate recursively through |path| and add / update watches. void UpdateRecursiveWatchesForPath(const FilePath& path); // Do internal bookkeeping to update mappings between |watch| and its // associated full path |path|. void TrackWatchForRecursion(InotifyReader::Watch watch, const FilePath& path); // Remove all the recursive watches. void RemoveRecursiveWatches(); // |path| is a symlink to a non-existent target. Attempt to add a watch to // the link target's parent directory. Update |watch_entry| on success. void AddWatchForBrokenSymlink(const FilePath& path, WatchEntry* watch_entry); bool HasValidWatchVector() const; // Callback to notify upon changes. FilePathWatcher::Callback callback_; // The file or directory we're supposed to watch. FilePath target_; bool recursive_; // The vector of watches and next component names for all path components, // starting at the root directory. The last entry corresponds to the watch for // |target_| and always stores an empty next component name in |subdir|. WatchVector watches_; hash_map<InotifyReader::Watch, FilePath> recursive_paths_by_watch_; std::map<FilePath, InotifyReader::Watch> recursive_watches_by_path_; DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl); }; void InotifyReaderCallback(InotifyReader* reader, int inotify_fd, int shutdown_fd) { // Make sure the file descriptors are good for use with select(). CHECK_LE(0, inotify_fd); CHECK_GT(FD_SETSIZE, inotify_fd); CHECK_LE(0, shutdown_fd); CHECK_GT(FD_SETSIZE, shutdown_fd); trace_event::TraceLog::GetInstance()->SetCurrentThreadBlocksMessageLoop(); while (true) { fd_set rfds; FD_ZERO(&rfds); FD_SET(inotify_fd, &rfds); FD_SET(shutdown_fd, &rfds); // Wait until some inotify events are available. int select_result = HANDLE_EINTR(select(std::max(inotify_fd, shutdown_fd) + 1, &rfds, NULL, NULL, NULL)); if (select_result < 0) { DPLOG(WARNING) << "select failed"; return; } if (FD_ISSET(shutdown_fd, &rfds)) return; // Adjust buffer size to current event queue size. int buffer_size; int ioctl_result = HANDLE_EINTR(ioctl(inotify_fd, FIONREAD, &buffer_size)); if (ioctl_result != 0) { DPLOG(WARNING) << "ioctl failed"; return; } std::vector<char> buffer(buffer_size); ssize_t bytes_read = HANDLE_EINTR(read(inotify_fd, &buffer[0], buffer_size)); if (bytes_read < 0) { DPLOG(WARNING) << "read from inotify fd failed"; return; } ssize_t i = 0; while (i < bytes_read) { inotify_event* event = reinterpret_cast<inotify_event*>(&buffer[i]); size_t event_size = sizeof(inotify_event) + event->len; DCHECK(i + event_size <= static_cast<size_t>(bytes_read)); reader->OnInotifyEvent(event); i += event_size; } } } static LazyInstance<InotifyReader>::Leaky g_inotify_reader = LAZY_INSTANCE_INITIALIZER; InotifyReader::InotifyReader() : thread_("inotify_reader"), inotify_fd_(inotify_init()), valid_(false) { if (inotify_fd_ < 0) PLOG(ERROR) << "inotify_init() failed"; shutdown_pipe_[0] = -1; shutdown_pipe_[1] = -1; if (inotify_fd_ >= 0 && pipe(shutdown_pipe_) == 0 && thread_.Start()) { thread_.task_runner()->PostTask( FROM_HERE, Bind(&InotifyReaderCallback, this, inotify_fd_, shutdown_pipe_[0])); valid_ = true; } } InotifyReader::~InotifyReader() { if (valid_) { // Write to the self-pipe so that the select call in InotifyReaderTask // returns. ssize_t ret = HANDLE_EINTR(write(shutdown_pipe_[1], "", 1)); DPCHECK(ret > 0); DCHECK_EQ(ret, 1); thread_.Stop(); } if (inotify_fd_ >= 0) close(inotify_fd_); if (shutdown_pipe_[0] >= 0) close(shutdown_pipe_[0]); if (shutdown_pipe_[1] >= 0) close(shutdown_pipe_[1]); } InotifyReader::Watch InotifyReader::AddWatch( const FilePath& path, FilePathWatcherImpl* watcher) { if (!valid_) return kInvalidWatch; AutoLock auto_lock(lock_); Watch watch = inotify_add_watch(inotify_fd_, path.value().c_str(), IN_ATTRIB | IN_CREATE | IN_DELETE | IN_CLOSE_WRITE | IN_MOVE | IN_ONLYDIR); if (watch == kInvalidWatch) return kInvalidWatch; watchers_[watch].insert(watcher); return watch; } void InotifyReader::RemoveWatch(Watch watch, FilePathWatcherImpl* watcher) { if (!valid_ || (watch == kInvalidWatch)) return; AutoLock auto_lock(lock_); watchers_[watch].erase(watcher); if (watchers_[watch].empty()) { watchers_.erase(watch); inotify_rm_watch(inotify_fd_, watch); } } void InotifyReader::OnInotifyEvent(const inotify_event* event) { if (event->mask & IN_IGNORED) return; FilePath::StringType child(event->len ? event->name : FILE_PATH_LITERAL("")); AutoLock auto_lock(lock_); for (WatcherSet::iterator watcher = watchers_[event->wd].begin(); watcher != watchers_[event->wd].end(); ++watcher) { (*watcher)->OnFilePathChanged(event->wd, child, event->mask & (IN_CREATE | IN_MOVED_TO), event->mask & (IN_DELETE | IN_MOVED_FROM), event->mask & IN_ISDIR); } } FilePathWatcherImpl::FilePathWatcherImpl() : recursive_(false) { } void FilePathWatcherImpl::OnFilePathChanged(InotifyReader::Watch fired_watch, const FilePath::StringType& child, bool created, bool deleted, bool is_dir) { if (!task_runner()->BelongsToCurrentThread()) { // Switch to task_runner() to access |watches_| safely. task_runner()->PostTask(FROM_HERE, Bind(&FilePathWatcherImpl::OnFilePathChanged, this, fired_watch, child, created, deleted, is_dir)); return; } // Check to see if CancelOnMessageLoopThread() has already been called. // May happen when code flow reaches here from the PostTask() above. if (watches_.empty()) { DCHECK(target_.empty()); return; } DCHECK(MessageLoopForIO::current()); DCHECK(HasValidWatchVector()); // Used below to avoid multiple recursive updates. bool did_update = false; // Find the entry in |watches_| that corresponds to |fired_watch|. for (size_t i = 0; i < watches_.size(); ++i) { const WatchEntry& watch_entry = watches_[i]; if (fired_watch != watch_entry.watch) continue; // Check whether a path component of |target_| changed. bool change_on_target_path = child.empty() || (child == watch_entry.linkname) || (child == watch_entry.subdir); // Check if the change references |target_| or a direct child of |target_|. bool target_changed; if (watch_entry.subdir.empty()) { // The fired watch is for a WatchEntry without a subdir. Thus for a given // |target_| = "/path/to/foo", this is for "foo". Here, check either: // - the target has no symlink: it is the target and it changed. // - the target has a symlink, and it matches |child|. target_changed = (watch_entry.linkname.empty() || child == watch_entry.linkname); } else { // The fired watch is for a WatchEntry with a subdir. Thus for a given // |target_| = "/path/to/foo", this is for {"/", "/path", "/path/to"}. // So we can safely access the next WatchEntry since we have not reached // the end yet. Check |watch_entry| is for "/path/to", i.e. the next // element is "foo". bool next_watch_may_be_for_target = watches_[i + 1].subdir.empty(); if (next_watch_may_be_for_target) { // The current |watch_entry| is for "/path/to", so check if the |child| // that changed is "foo". target_changed = watch_entry.subdir == child; } else { // The current |watch_entry| is not for "/path/to", so the next entry // cannot be "foo". Thus |target_| has not changed. target_changed = false; } } // Update watches if a directory component of the |target_| path // (dis)appears. Note that we don't add the additional restriction of // checking the event mask to see if it is for a directory here as changes // to symlinks on the target path will not have IN_ISDIR set in the event // masks. As a result we may sometimes call UpdateWatches() unnecessarily. if (change_on_target_path && (created || deleted) && !did_update) { UpdateWatches(); did_update = true; } // Report the following events: // - The target or a direct child of the target got changed (in case the // watched path refers to a directory). // - One of the parent directories got moved or deleted, since the target // disappears in this case. // - One of the parent directories appears. The event corresponding to // the target appearing might have been missed in this case, so recheck. if (target_changed || (change_on_target_path && deleted) || (change_on_target_path && created && PathExists(target_))) { if (!did_update) { UpdateRecursiveWatches(fired_watch, is_dir); did_update = true; } callback_.Run(target_, false /* error */); return; } } if (ContainsKey(recursive_paths_by_watch_, fired_watch)) { if (!did_update) UpdateRecursiveWatches(fired_watch, is_dir); callback_.Run(target_, false /* error */); } } bool FilePathWatcherImpl::Watch(const FilePath& path, bool recursive, const FilePathWatcher::Callback& callback) { DCHECK(target_.empty()); DCHECK(MessageLoopForIO::current()); set_task_runner(ThreadTaskRunnerHandle::Get()); callback_ = callback; target_ = path; recursive_ = recursive; MessageLoop::current()->AddDestructionObserver(this); std::vector<FilePath::StringType> comps; target_.GetComponents(&comps); DCHECK(!comps.empty()); for (size_t i = 1; i < comps.size(); ++i) watches_.push_back(WatchEntry(comps[i])); watches_.push_back(WatchEntry(FilePath::StringType())); UpdateWatches(); return true; } void FilePathWatcherImpl::Cancel() { if (callback_.is_null()) { // Watch was never called, or the message_loop() thread is already gone. set_cancelled(); return; } // Switch to the message_loop() if necessary so we can access |watches_|. if (!task_runner()->BelongsToCurrentThread()) { task_runner()->PostTask(FROM_HERE, Bind(&FilePathWatcher::CancelWatch, make_scoped_refptr(this))); } else { CancelOnMessageLoopThread(); } } void FilePathWatcherImpl::CancelOnMessageLoopThread() { DCHECK(task_runner()->BelongsToCurrentThread()); set_cancelled(); if (!callback_.is_null()) { MessageLoop::current()->RemoveDestructionObserver(this); callback_.Reset(); } for (size_t i = 0; i < watches_.size(); ++i) g_inotify_reader.Get().RemoveWatch(watches_[i].watch, this); watches_.clear(); target_.clear(); if (recursive_) RemoveRecursiveWatches(); } void FilePathWatcherImpl::WillDestroyCurrentMessageLoop() { CancelOnMessageLoopThread(); } void FilePathWatcherImpl::UpdateWatches() { // Ensure this runs on the message_loop() exclusively in order to avoid // concurrency issues. DCHECK(task_runner()->BelongsToCurrentThread()); DCHECK(HasValidWatchVector()); // Walk the list of watches and update them as we go. FilePath path(FILE_PATH_LITERAL("/")); for (size_t i = 0; i < watches_.size(); ++i) { WatchEntry& watch_entry = watches_[i]; InotifyReader::Watch old_watch = watch_entry.watch; watch_entry.watch = InotifyReader::kInvalidWatch; watch_entry.linkname.clear(); watch_entry.watch = g_inotify_reader.Get().AddWatch(path, this); if (watch_entry.watch == InotifyReader::kInvalidWatch) { // Ignore the error code (beyond symlink handling) to attempt to add // watches on accessible children of unreadable directories. Note that // this is a best-effort attempt; we may not catch events in this // scenario. if (IsLink(path)) AddWatchForBrokenSymlink(path, &watch_entry); } if (old_watch != watch_entry.watch) g_inotify_reader.Get().RemoveWatch(old_watch, this); path = path.Append(watch_entry.subdir); } UpdateRecursiveWatches(InotifyReader::kInvalidWatch, false /* is directory? */); } void FilePathWatcherImpl::UpdateRecursiveWatches( InotifyReader::Watch fired_watch, bool is_dir) { if (!recursive_) return; if (!DirectoryExists(target_)) { RemoveRecursiveWatches(); return; } // Check to see if this is a forced update or if some component of |target_| // has changed. For these cases, redo the watches for |target_| and below. if (!ContainsKey(recursive_paths_by_watch_, fired_watch)) { UpdateRecursiveWatchesForPath(target_); return; } // Underneath |target_|, only directory changes trigger watch updates. if (!is_dir) return; const FilePath& changed_dir = recursive_paths_by_watch_[fired_watch]; std::map<FilePath, InotifyReader::Watch>::iterator start_it = recursive_watches_by_path_.lower_bound(changed_dir); std::map<FilePath, InotifyReader::Watch>::iterator end_it = start_it; for (; end_it != recursive_watches_by_path_.end(); ++end_it) { const FilePath& cur_path = end_it->first; if (!changed_dir.IsParent(cur_path)) break; if (!DirectoryExists(cur_path)) g_inotify_reader.Get().RemoveWatch(end_it->second, this); } recursive_watches_by_path_.erase(start_it, end_it); UpdateRecursiveWatchesForPath(changed_dir); } void FilePathWatcherImpl::UpdateRecursiveWatchesForPath(const FilePath& path) { DCHECK(recursive_); DCHECK(!path.empty()); DCHECK(DirectoryExists(path)); // Note: SHOW_SYM_LINKS exposes symlinks as symlinks, so they are ignored // rather than followed. Following symlinks can easily lead to the undesirable // situation where the entire file system is being watched. FileEnumerator enumerator( path, true /* recursive enumeration */, FileEnumerator::DIRECTORIES | FileEnumerator::SHOW_SYM_LINKS); for (FilePath current = enumerator.Next(); !current.empty(); current = enumerator.Next()) { DCHECK(enumerator.GetInfo().IsDirectory()); if (!ContainsKey(recursive_watches_by_path_, current)) { // Add new watches. InotifyReader::Watch watch = g_inotify_reader.Get().AddWatch(current, this); TrackWatchForRecursion(watch, current); } else { // Update existing watches. InotifyReader::Watch old_watch = recursive_watches_by_path_[current]; DCHECK_NE(InotifyReader::kInvalidWatch, old_watch); InotifyReader::Watch watch = g_inotify_reader.Get().AddWatch(current, this); if (watch != old_watch) { g_inotify_reader.Get().RemoveWatch(old_watch, this); recursive_paths_by_watch_.erase(old_watch); recursive_watches_by_path_.erase(current); TrackWatchForRecursion(watch, current); } } } } void FilePathWatcherImpl::TrackWatchForRecursion(InotifyReader::Watch watch, const FilePath& path) { DCHECK(recursive_); DCHECK(!path.empty()); DCHECK(target_.IsParent(path)); if (watch == InotifyReader::kInvalidWatch) return; DCHECK(!ContainsKey(recursive_paths_by_watch_, watch)); DCHECK(!ContainsKey(recursive_watches_by_path_, path)); recursive_paths_by_watch_[watch] = path; recursive_watches_by_path_[path] = watch; } void FilePathWatcherImpl::RemoveRecursiveWatches() { if (!recursive_) return; for (hash_map<InotifyReader::Watch, FilePath>::const_iterator it = recursive_paths_by_watch_.begin(); it != recursive_paths_by_watch_.end(); ++it) { g_inotify_reader.Get().RemoveWatch(it->first, this); } recursive_paths_by_watch_.clear(); recursive_watches_by_path_.clear(); } void FilePathWatcherImpl::AddWatchForBrokenSymlink(const FilePath& path, WatchEntry* watch_entry) { DCHECK_EQ(InotifyReader::kInvalidWatch, watch_entry->watch); FilePath link; if (!ReadSymbolicLink(path, &link)) return; if (!link.IsAbsolute()) link = path.DirName().Append(link); // Try watching symlink target directory. If the link target is "/", then we // shouldn't get here in normal situations and if we do, we'd watch "/" for // changes to a component "/" which is harmless so no special treatment of // this case is required. InotifyReader::Watch watch = g_inotify_reader.Get().AddWatch(link.DirName(), this); if (watch == InotifyReader::kInvalidWatch) { // TODO(craig) Symlinks only work if the parent directory for the target // exist. Ideally we should make sure we've watched all the components of // the symlink path for changes. See crbug.com/91561 for details. DPLOG(WARNING) << "Watch failed for " << link.DirName().value(); return; } watch_entry->watch = watch; watch_entry->linkname = link.BaseName().value(); } bool FilePathWatcherImpl::HasValidWatchVector() const { if (watches_.empty()) return false; for (size_t i = 0; i < watches_.size() - 1; ++i) { if (watches_[i].subdir.empty()) return false; } return watches_[watches_.size() - 1].subdir.empty(); } } // namespace FilePathWatcher::FilePathWatcher() { impl_ = new FilePathWatcherImpl(); } } // namespace base