// 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