// 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 <string.h>
#include <sys/inotify.h>
#include <sys/ioctl.h>
#include <sys/select.h>
#include <unistd.h>
#include <algorithm>
#include <set>
#include <utility>
#include <vector>
#include "base/bind.h"
#include "base/containers/hash_tables.h"
#include "base/debug/trace_event.h"
#include "base/file_util.h"
#include "base/files/file_path.h"
#include "base/lazy_instance.h"
#include "base/location.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/message_loop/message_loop.h"
#include "base/message_loop/message_loop_proxy.h"
#include "base/posix/eintr_wrapper.h"
#include "base/synchronization/lock.h"
#include "base/threading/thread.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|. Returns true on success.
bool 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|. The flag |created| is true if
// the object appears.
void OnFilePathChanged(InotifyReader::Watch fired_watch,
const FilePath::StringType& child,
bool created);
// Start watching |path| for changes and notify |delegate| on each change.
// Returns true if watch for |path| has been added successfully.
virtual bool Watch(const FilePath& path,
bool recursive,
const FilePathWatcher::Callback& callback) OVERRIDE;
// Cancel the watch. This unregisters the instance with InotifyReader.
virtual void Cancel() 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.
virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
protected:
virtual ~FilePathWatcherImpl() {}
private:
// Cleans up and stops observing the |message_loop_| thread.
virtual void CancelOnMessageLoopThread() OVERRIDE;
// Inotify watches are installed for all directory components of |target_|. A
// WatchEntry instance holds the watch descriptor for a component and the
// subdirectory for that identifies the next component. If a symbolic link
// is being watched, the target of the link is also kept.
struct WatchEntry {
WatchEntry(InotifyReader::Watch watch, const FilePath::StringType& subdir)
: watch_(watch),
subdir_(subdir) {}
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. Updates |watched_path_|. Returns true on success.
bool UpdateWatches() WARN_UNUSED_RESULT;
// Callback to notify upon changes.
FilePathWatcher::Callback callback_;
// The file or directory we're supposed to watch.
FilePath target_;
// 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_;
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);
debug::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_.message_loop()->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_CREATE | IN_DELETE |
IN_CLOSE_WRITE | IN_MOVE |
IN_ONLYDIR);
if (watch == kInvalidWatch)
return kInvalidWatch;
watchers_[watch].insert(watcher);
return watch;
}
bool InotifyReader::RemoveWatch(Watch watch,
FilePathWatcherImpl* watcher) {
if (!valid_)
return false;
AutoLock auto_lock(lock_);
watchers_[watch].erase(watcher);
if (watchers_[watch].empty()) {
watchers_.erase(watch);
return (inotify_rm_watch(inotify_fd_, watch) == 0);
}
return true;
}
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));
}
}
FilePathWatcherImpl::FilePathWatcherImpl() {
}
void FilePathWatcherImpl::OnFilePathChanged(InotifyReader::Watch fired_watch,
const FilePath::StringType& child,
bool created) {
if (!message_loop()->BelongsToCurrentThread()) {
// Switch to message_loop_ to access watches_ safely.
message_loop()->PostTask(FROM_HERE,
Bind(&FilePathWatcherImpl::OnFilePathChanged,
this,
fired_watch,
child,
created));
return;
}
DCHECK(MessageLoopForIO::current());
// Find the entry in |watches_| that corresponds to |fired_watch|.
WatchVector::const_iterator watch_entry(watches_.begin());
for ( ; watch_entry != watches_.end(); ++watch_entry) {
if (fired_watch == watch_entry->watch_) {
// Check whether a path component of |target_| changed.
bool change_on_target_path = child.empty() ||
((child == watch_entry->subdir_) && watch_entry->linkname_.empty()) ||
(child == watch_entry->linkname_);
// Check whether the change references |target_| or a direct child.
DCHECK(watch_entry->subdir_.empty() ||
(watch_entry + 1) != watches_.end());
bool target_changed =
(watch_entry->subdir_.empty() && (child == watch_entry->linkname_)) ||
(watch_entry->subdir_.empty() && watch_entry->linkname_.empty()) ||
(watch_entry->subdir_ == child && (watch_entry + 1)->subdir_.empty());
// 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 && !UpdateWatches()) {
callback_.Run(target_, true /* error */);
return;
}
// 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 && !created) ||
(change_on_target_path && PathExists(target_))) {
callback_.Run(target_, false);
return;
}
}
}
}
bool FilePathWatcherImpl::Watch(const FilePath& path,
bool recursive,
const FilePathWatcher::Callback& callback) {
DCHECK(target_.empty());
DCHECK(MessageLoopForIO::current());
if (recursive) {
// Recursive watch is not supported on this platform.
NOTIMPLEMENTED();
return false;
}
set_message_loop(MessageLoopProxy::current().get());
callback_ = callback;
target_ = path;
MessageLoop::current()->AddDestructionObserver(this);
std::vector<FilePath::StringType> comps;
target_.GetComponents(&comps);
DCHECK(!comps.empty());
std::vector<FilePath::StringType>::const_iterator comp = comps.begin();
for (++comp; comp != comps.end(); ++comp)
watches_.push_back(WatchEntry(InotifyReader::kInvalidWatch, *comp));
watches_.push_back(WatchEntry(InotifyReader::kInvalidWatch,
FilePath::StringType()));
return UpdateWatches();
}
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 (!message_loop()->BelongsToCurrentThread()) {
message_loop()->PostTask(FROM_HERE,
Bind(&FilePathWatcher::CancelWatch,
make_scoped_refptr(this)));
} else {
CancelOnMessageLoopThread();
}
}
void FilePathWatcherImpl::CancelOnMessageLoopThread() {
if (!is_cancelled())
set_cancelled();
if (!callback_.is_null()) {
MessageLoop::current()->RemoveDestructionObserver(this);
callback_.Reset();
}
for (WatchVector::iterator watch_entry(watches_.begin());
watch_entry != watches_.end(); ++watch_entry) {
if (watch_entry->watch_ != InotifyReader::kInvalidWatch)
g_inotify_reader.Get().RemoveWatch(watch_entry->watch_, this);
}
watches_.clear();
target_.clear();
}
void FilePathWatcherImpl::WillDestroyCurrentMessageLoop() {
CancelOnMessageLoopThread();
}
bool FilePathWatcherImpl::UpdateWatches() {
// Ensure this runs on the |message_loop_| exclusively in order to avoid
// concurrency issues.
DCHECK(message_loop()->BelongsToCurrentThread());
// Walk the list of watches and update them as we go.
FilePath path(FILE_PATH_LITERAL("/"));
bool path_valid = true;
for (WatchVector::iterator watch_entry(watches_.begin());
watch_entry != watches_.end(); ++watch_entry) {
InotifyReader::Watch old_watch = watch_entry->watch_;
if (path_valid) {
watch_entry->watch_ = g_inotify_reader.Get().AddWatch(path, this);
if ((watch_entry->watch_ == InotifyReader::kInvalidWatch) &&
base::IsLink(path)) {
FilePath link;
if (ReadSymbolicLink(path, &link)) {
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.
watch_entry->watch_ =
g_inotify_reader.Get().AddWatch(link.DirName(), this);
if (watch_entry->watch_ != InotifyReader::kInvalidWatch) {
watch_entry->linkname_ = link.BaseName().value();
} else {
DPLOG(WARNING) << "Watch failed for " << link.DirName().value();
// 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.
}
}
}
if (watch_entry->watch_ == InotifyReader::kInvalidWatch) {
path_valid = false;
}
} else {
watch_entry->watch_ = InotifyReader::kInvalidWatch;
}
if (old_watch != InotifyReader::kInvalidWatch &&
old_watch != watch_entry->watch_) {
g_inotify_reader.Get().RemoveWatch(old_watch, this);
}
path = path.Append(watch_entry->subdir_);
}
return true;
}
} // namespace
FilePathWatcher::FilePathWatcher() {
impl_ = new FilePathWatcherImpl();
}
} // namespace base