1 // Copyright (c) 2011 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 <set>
16 #include <utility>
17 #include <vector>
18
19 #include "base/eintr_wrapper.h"
20 #include "base/file_path.h"
21 #include "base/file_util.h"
22 #include "base/hash_tables.h"
23 #include "base/lazy_instance.h"
24 #include "base/logging.h"
25 #include "base/memory/scoped_ptr.h"
26 #include "base/message_loop.h"
27 #include "base/message_loop_proxy.h"
28 #include "base/synchronization/lock.h"
29 #include "base/task.h"
30 #include "base/threading/thread.h"
31
32 namespace base {
33 namespace files {
34
35 namespace {
36
37 class FilePathWatcherImpl;
38
39 // Singleton to manage all inotify watches.
40 // TODO(tony): It would be nice if this wasn't a singleton.
41 // http://crbug.com/38174
42 class InotifyReader {
43 public:
44 typedef int Watch; // Watch descriptor used by AddWatch and RemoveWatch.
45 static const Watch kInvalidWatch = -1;
46
47 // Watch directory |path| for changes. |watcher| will be notified on each
48 // change. Returns kInvalidWatch on failure.
49 Watch AddWatch(const FilePath& path, FilePathWatcherImpl* watcher);
50
51 // Remove |watch|. Returns true on success.
52 bool RemoveWatch(Watch watch, FilePathWatcherImpl* watcher);
53
54 // Callback for InotifyReaderTask.
55 void OnInotifyEvent(const inotify_event* event);
56
57 private:
58 friend struct ::base::DefaultLazyInstanceTraits<InotifyReader>;
59
60 typedef std::set<FilePathWatcherImpl*> WatcherSet;
61
62 InotifyReader();
63 ~InotifyReader();
64
65 // We keep track of which delegates want to be notified on which watches.
66 base::hash_map<Watch, WatcherSet> watchers_;
67
68 // Lock to protect watchers_.
69 base::Lock lock_;
70
71 // Separate thread on which we run blocking read for inotify events.
72 base::Thread thread_;
73
74 // File descriptor returned by inotify_init.
75 const int inotify_fd_;
76
77 // Use self-pipe trick to unblock select during shutdown.
78 int shutdown_pipe_[2];
79
80 // Flag set to true when startup was successful.
81 bool valid_;
82
83 DISALLOW_COPY_AND_ASSIGN(InotifyReader);
84 };
85
86 class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate,
87 public MessageLoop::DestructionObserver {
88 public:
89 FilePathWatcherImpl();
90
91 // Called for each event coming from the watch. |fired_watch| identifies the
92 // watch that fired, |child| indicates what has changed, and is relative to
93 // the currently watched path for |fired_watch|. The flag |created| is true if
94 // the object appears, and |is_directory| is set when the event refers to a
95 // directory.
96 void OnFilePathChanged(InotifyReader::Watch fired_watch,
97 const FilePath::StringType& child,
98 bool created,
99 bool is_directory);
100
101 // Start watching |path| for changes and notify |delegate| on each change.
102 // Returns true if watch for |path| has been added successfully.
103 virtual bool Watch(const FilePath& path,
104 FilePathWatcher::Delegate* delegate) OVERRIDE;
105
106 // Cancel the watch. This unregisters the instance with InotifyReader.
107 virtual void Cancel() OVERRIDE;
108
109 // Deletion of the FilePathWatcher will call Cancel() to dispose of this
110 // object in the right thread. This also observes destruction of the required
111 // cleanup thread, in case it quits before Cancel() is called.
112 virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
113
114 private:
~FilePathWatcherImpl()115 virtual ~FilePathWatcherImpl() {}
116
117 // Cleans up and stops observing the |message_loop_| thread.
118 void CancelOnMessageLoopThread() OVERRIDE;
119
120 // Inotify watches are installed for all directory components of |target_|. A
121 // WatchEntry instance holds the watch descriptor for a component and the
122 // subdirectory for that identifies the next component.
123 struct WatchEntry {
WatchEntrybase::files::__anon483d23560111::FilePathWatcherImpl::WatchEntry124 WatchEntry(InotifyReader::Watch watch, const FilePath::StringType& subdir)
125 : watch_(watch),
126 subdir_(subdir) {}
127
128 InotifyReader::Watch watch_;
129 FilePath::StringType subdir_;
130 };
131 typedef std::vector<WatchEntry> WatchVector;
132
133 // Reconfigure to watch for the most specific parent directory of |target_|
134 // that exists. Updates |watched_path_|. Returns true on success.
135 bool UpdateWatches() WARN_UNUSED_RESULT;
136
137 // Delegate to notify upon changes.
138 scoped_refptr<FilePathWatcher::Delegate> delegate_;
139
140 // The file or directory we're supposed to watch.
141 FilePath target_;
142
143 // The vector of watches and next component names for all path components,
144 // starting at the root directory. The last entry corresponds to the watch for
145 // |target_| and always stores an empty next component name in |subdir_|.
146 WatchVector watches_;
147
148 DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl);
149 };
150
151 class InotifyReaderTask : public Task {
152 public:
InotifyReaderTask(InotifyReader * reader,int inotify_fd,int shutdown_fd)153 InotifyReaderTask(InotifyReader* reader, int inotify_fd, int shutdown_fd)
154 : reader_(reader),
155 inotify_fd_(inotify_fd),
156 shutdown_fd_(shutdown_fd) {
157 }
158
Run()159 virtual void Run() {
160 while (true) {
161 fd_set rfds;
162 FD_ZERO(&rfds);
163 FD_SET(inotify_fd_, &rfds);
164 FD_SET(shutdown_fd_, &rfds);
165
166 // Wait until some inotify events are available.
167 int select_result =
168 HANDLE_EINTR(select(std::max(inotify_fd_, shutdown_fd_) + 1,
169 &rfds, NULL, NULL, NULL));
170 if (select_result < 0) {
171 DPLOG(WARNING) << "select failed";
172 return;
173 }
174
175 if (FD_ISSET(shutdown_fd_, &rfds))
176 return;
177
178 // Adjust buffer size to current event queue size.
179 int buffer_size;
180 int ioctl_result = HANDLE_EINTR(ioctl(inotify_fd_, FIONREAD,
181 &buffer_size));
182
183 if (ioctl_result != 0) {
184 DPLOG(WARNING) << "ioctl failed";
185 return;
186 }
187
188 std::vector<char> buffer(buffer_size);
189
190 ssize_t bytes_read = HANDLE_EINTR(read(inotify_fd_, &buffer[0],
191 buffer_size));
192
193 if (bytes_read < 0) {
194 DPLOG(WARNING) << "read from inotify fd failed";
195 return;
196 }
197
198 ssize_t i = 0;
199 while (i < bytes_read) {
200 inotify_event* event = reinterpret_cast<inotify_event*>(&buffer[i]);
201 size_t event_size = sizeof(inotify_event) + event->len;
202 DCHECK(i + event_size <= static_cast<size_t>(bytes_read));
203 reader_->OnInotifyEvent(event);
204 i += event_size;
205 }
206 }
207 }
208
209 private:
210 InotifyReader* reader_;
211 int inotify_fd_;
212 int shutdown_fd_;
213
214 DISALLOW_COPY_AND_ASSIGN(InotifyReaderTask);
215 };
216
217 static base::LazyInstance<InotifyReader> g_inotify_reader(
218 base::LINKER_INITIALIZED);
219
InotifyReader()220 InotifyReader::InotifyReader()
221 : thread_("inotify_reader"),
222 inotify_fd_(inotify_init()),
223 valid_(false) {
224 shutdown_pipe_[0] = -1;
225 shutdown_pipe_[1] = -1;
226 if (inotify_fd_ >= 0 && pipe(shutdown_pipe_) == 0 && thread_.Start()) {
227 thread_.message_loop()->PostTask(
228 FROM_HERE, new InotifyReaderTask(this, inotify_fd_, shutdown_pipe_[0]));
229 valid_ = true;
230 }
231 }
232
~InotifyReader()233 InotifyReader::~InotifyReader() {
234 if (valid_) {
235 // Write to the self-pipe so that the select call in InotifyReaderTask
236 // returns.
237 ssize_t ret = HANDLE_EINTR(write(shutdown_pipe_[1], "", 1));
238 DPCHECK(ret > 0);
239 DCHECK_EQ(ret, 1);
240 thread_.Stop();
241 }
242 if (inotify_fd_ >= 0)
243 close(inotify_fd_);
244 if (shutdown_pipe_[0] >= 0)
245 close(shutdown_pipe_[0]);
246 if (shutdown_pipe_[1] >= 0)
247 close(shutdown_pipe_[1]);
248 }
249
AddWatch(const FilePath & path,FilePathWatcherImpl * watcher)250 InotifyReader::Watch InotifyReader::AddWatch(
251 const FilePath& path, FilePathWatcherImpl* watcher) {
252 if (!valid_)
253 return kInvalidWatch;
254
255 base::AutoLock auto_lock(lock_);
256
257 Watch watch = inotify_add_watch(inotify_fd_, path.value().c_str(),
258 IN_CREATE | IN_DELETE |
259 IN_CLOSE_WRITE | IN_MOVE |
260 IN_ONLYDIR);
261
262 if (watch == kInvalidWatch)
263 return kInvalidWatch;
264
265 watchers_[watch].insert(watcher);
266
267 return watch;
268 }
269
RemoveWatch(Watch watch,FilePathWatcherImpl * watcher)270 bool InotifyReader::RemoveWatch(Watch watch,
271 FilePathWatcherImpl* watcher) {
272 if (!valid_)
273 return false;
274
275 base::AutoLock auto_lock(lock_);
276
277 watchers_[watch].erase(watcher);
278
279 if (watchers_[watch].empty()) {
280 watchers_.erase(watch);
281 return (inotify_rm_watch(inotify_fd_, watch) == 0);
282 }
283
284 return true;
285 }
286
OnInotifyEvent(const inotify_event * event)287 void InotifyReader::OnInotifyEvent(const inotify_event* event) {
288 if (event->mask & IN_IGNORED)
289 return;
290
291 FilePath::StringType child(event->len ? event->name : FILE_PATH_LITERAL(""));
292 base::AutoLock auto_lock(lock_);
293
294 for (WatcherSet::iterator watcher = watchers_[event->wd].begin();
295 watcher != watchers_[event->wd].end();
296 ++watcher) {
297 (*watcher)->OnFilePathChanged(event->wd,
298 child,
299 event->mask & (IN_CREATE | IN_MOVED_TO),
300 event->mask & IN_ISDIR);
301 }
302 }
303
FilePathWatcherImpl()304 FilePathWatcherImpl::FilePathWatcherImpl()
305 : delegate_(NULL) {
306 }
307
OnFilePathChanged(InotifyReader::Watch fired_watch,const FilePath::StringType & child,bool created,bool is_directory)308 void FilePathWatcherImpl::OnFilePathChanged(
309 InotifyReader::Watch fired_watch,
310 const FilePath::StringType& child,
311 bool created,
312 bool is_directory) {
313
314 if (!message_loop()->BelongsToCurrentThread()) {
315 // Switch to message_loop_ to access watches_ safely.
316 message_loop()->PostTask(FROM_HERE,
317 NewRunnableMethod(this,
318 &FilePathWatcherImpl::OnFilePathChanged,
319 fired_watch,
320 child,
321 created,
322 is_directory));
323 return;
324 }
325
326 DCHECK(MessageLoopForIO::current());
327
328 // Find the entry in |watches_| that corresponds to |fired_watch|.
329 WatchVector::const_iterator watch_entry(watches_.begin());
330 for ( ; watch_entry != watches_.end(); ++watch_entry) {
331 if (fired_watch == watch_entry->watch_)
332 break;
333 }
334
335 // If this notification is from a previous generation of watches or the watch
336 // has been cancelled (|watches_| is empty then), bail out.
337 if (watch_entry == watches_.end())
338 return;
339
340 // Check whether a path component of |target_| changed.
341 bool change_on_target_path = child.empty() || child == watch_entry->subdir_;
342
343 // Check whether the change references |target_| or a direct child.
344 DCHECK(watch_entry->subdir_.empty() || (watch_entry + 1) != watches_.end());
345 bool target_changed = watch_entry->subdir_.empty() ||
346 (watch_entry->subdir_ == child && (++watch_entry)->subdir_.empty());
347
348 // Update watches if a directory component of the |target_| path (dis)appears.
349 if (is_directory && change_on_target_path && !UpdateWatches()) {
350 delegate_->OnFilePathError(target_);
351 return;
352 }
353
354 // Report the following events:
355 // - The target or a direct child of the target got changed (in case the
356 // watched path refers to a directory).
357 // - One of the parent directories got moved or deleted, since the target
358 // disappears in this case.
359 // - One of the parent directories appears. The event corresponding to the
360 // target appearing might have been missed in this case, so recheck.
361 if (target_changed ||
362 (change_on_target_path && !created) ||
363 (change_on_target_path && file_util::PathExists(target_))) {
364 delegate_->OnFilePathChanged(target_);
365 }
366 }
367
Watch(const FilePath & path,FilePathWatcher::Delegate * delegate)368 bool FilePathWatcherImpl::Watch(const FilePath& path,
369 FilePathWatcher::Delegate* delegate) {
370 DCHECK(target_.empty());
371 DCHECK(MessageLoopForIO::current());
372
373 set_message_loop(base::MessageLoopProxy::CreateForCurrentThread());
374 delegate_ = delegate;
375 target_ = path;
376 MessageLoop::current()->AddDestructionObserver(this);
377
378 std::vector<FilePath::StringType> comps;
379 target_.GetComponents(&comps);
380 DCHECK(!comps.empty());
381 for (std::vector<FilePath::StringType>::const_iterator comp(++comps.begin());
382 comp != comps.end(); ++comp) {
383 watches_.push_back(WatchEntry(InotifyReader::kInvalidWatch, *comp));
384 }
385 watches_.push_back(WatchEntry(InotifyReader::kInvalidWatch,
386 FilePath::StringType()));
387 return UpdateWatches();
388 }
389
Cancel()390 void FilePathWatcherImpl::Cancel() {
391 if (!delegate_) {
392 // Watch was never called, or the |message_loop_| thread is already gone.
393 set_cancelled();
394 return;
395 }
396
397 // Switch to the message_loop_ if necessary so we can access |watches_|.
398 if (!message_loop()->BelongsToCurrentThread()) {
399 message_loop()->PostTask(FROM_HERE,
400 new FilePathWatcher::CancelTask(this));
401 } else {
402 CancelOnMessageLoopThread();
403 }
404 }
405
CancelOnMessageLoopThread()406 void FilePathWatcherImpl::CancelOnMessageLoopThread() {
407 if (!is_cancelled()) {
408 set_cancelled();
409 MessageLoop::current()->RemoveDestructionObserver(this);
410
411 for (WatchVector::iterator watch_entry(watches_.begin());
412 watch_entry != watches_.end(); ++watch_entry) {
413 if (watch_entry->watch_ != InotifyReader::kInvalidWatch)
414 g_inotify_reader.Get().RemoveWatch(watch_entry->watch_, this);
415 }
416 watches_.clear();
417 delegate_ = NULL;
418 target_.clear();
419 }
420 }
421
WillDestroyCurrentMessageLoop()422 void FilePathWatcherImpl::WillDestroyCurrentMessageLoop() {
423 CancelOnMessageLoopThread();
424 }
425
UpdateWatches()426 bool FilePathWatcherImpl::UpdateWatches() {
427 // Ensure this runs on the message_loop_ exclusively in order to avoid
428 // concurrency issues.
429 DCHECK(message_loop()->BelongsToCurrentThread());
430
431 // Walk the list of watches and update them as we go.
432 FilePath path(FILE_PATH_LITERAL("/"));
433 bool path_valid = true;
434 for (WatchVector::iterator watch_entry(watches_.begin());
435 watch_entry != watches_.end(); ++watch_entry) {
436 InotifyReader::Watch old_watch = watch_entry->watch_;
437 if (path_valid) {
438 watch_entry->watch_ = g_inotify_reader.Get().AddWatch(path, this);
439 if (watch_entry->watch_ == InotifyReader::kInvalidWatch) {
440 path_valid = false;
441 }
442 } else {
443 watch_entry->watch_ = InotifyReader::kInvalidWatch;
444 }
445 if (old_watch != InotifyReader::kInvalidWatch &&
446 old_watch != watch_entry->watch_) {
447 g_inotify_reader.Get().RemoveWatch(old_watch, this);
448 }
449 path = path.Append(watch_entry->subdir_);
450 }
451
452 return true;
453 }
454
455 } // namespace
456
FilePathWatcher()457 FilePathWatcher::FilePathWatcher() {
458 impl_ = new FilePathWatcherImpl();
459 }
460
461 } // namespace files
462 } // namespace base
463