400 lines
14 KiB
C++
400 lines
14 KiB
C++
/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specic language governing permissions and
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* limitations under the License.
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*/
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#include "libappfuse/FuseBridgeLoop.h"
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#include <sys/epoll.h>
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#include <sys/socket.h>
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#include <unordered_map>
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#include <android-base/logging.h>
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#include <android-base/unique_fd.h>
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#include "libappfuse/EpollController.h"
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namespace android {
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namespace fuse {
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namespace {
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enum class FuseBridgeState { kWaitToReadEither, kWaitToReadProxy, kWaitToWriteProxy, kClosing };
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struct FuseBridgeEntryEvent {
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FuseBridgeEntry* entry;
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int events;
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};
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void GetObservedEvents(FuseBridgeState state, int* device_events, int* proxy_events) {
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switch (state) {
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case FuseBridgeState::kWaitToReadEither:
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*device_events = EPOLLIN;
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*proxy_events = EPOLLIN;
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return;
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case FuseBridgeState::kWaitToReadProxy:
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*device_events = 0;
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*proxy_events = EPOLLIN;
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return;
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case FuseBridgeState::kWaitToWriteProxy:
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*device_events = 0;
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*proxy_events = EPOLLOUT;
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return;
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case FuseBridgeState::kClosing:
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*device_events = 0;
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*proxy_events = 0;
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return;
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}
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}
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void LogResponseError(const std::string& message, const FuseResponse& response) {
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LOG(ERROR) << message << ": header.len=" << response.header.len
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<< " header.error=" << response.header.error
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<< " header.unique=" << response.header.unique;
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}
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}
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class FuseBridgeEntry {
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public:
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FuseBridgeEntry(int mount_id, base::unique_fd&& dev_fd, base::unique_fd&& proxy_fd)
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: mount_id_(mount_id),
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device_fd_(std::move(dev_fd)),
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proxy_fd_(std::move(proxy_fd)),
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state_(FuseBridgeState::kWaitToReadEither),
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last_state_(FuseBridgeState::kWaitToReadEither),
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last_device_events_({this, 0}),
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last_proxy_events_({this, 0}),
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open_count_(0) {}
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// Transfer bytes depends on availability of FDs and the internal |state_|.
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void Transfer(FuseBridgeLoopCallback* callback) {
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constexpr int kUnexpectedEventMask = ~(EPOLLIN | EPOLLOUT);
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const bool unexpected_event = (last_device_events_.events & kUnexpectedEventMask) ||
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(last_proxy_events_.events & kUnexpectedEventMask);
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const bool device_read_ready = last_device_events_.events & EPOLLIN;
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const bool proxy_read_ready = last_proxy_events_.events & EPOLLIN;
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const bool proxy_write_ready = last_proxy_events_.events & EPOLLOUT;
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last_state_ = state_;
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last_device_events_.events = 0;
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last_proxy_events_.events = 0;
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LOG(VERBOSE) << "Transfer device_read_ready=" << device_read_ready
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<< " proxy_read_ready=" << proxy_read_ready
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<< " proxy_write_ready=" << proxy_write_ready;
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if (unexpected_event) {
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LOG(ERROR) << "Invalid epoll event is observed";
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state_ = FuseBridgeState::kClosing;
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return;
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}
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switch (state_) {
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case FuseBridgeState::kWaitToReadEither:
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if (proxy_read_ready) {
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state_ = ReadFromProxy();
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} else if (device_read_ready) {
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state_ = ReadFromDevice(callback);
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}
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return;
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case FuseBridgeState::kWaitToReadProxy:
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CHECK(proxy_read_ready);
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state_ = ReadFromProxy();
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return;
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case FuseBridgeState::kWaitToWriteProxy:
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CHECK(proxy_write_ready);
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state_ = WriteToProxy();
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return;
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case FuseBridgeState::kClosing:
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return;
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}
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}
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bool IsClosing() const { return state_ == FuseBridgeState::kClosing; }
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int mount_id() const { return mount_id_; }
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private:
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friend class BridgeEpollController;
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FuseBridgeState ReadFromProxy() {
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switch (buffer_.response.ReadOrAgain(proxy_fd_)) {
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case ResultOrAgain::kSuccess:
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break;
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case ResultOrAgain::kFailure:
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return FuseBridgeState::kClosing;
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case ResultOrAgain::kAgain:
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return FuseBridgeState::kWaitToReadProxy;
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}
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if (!buffer_.response.Write(device_fd_)) {
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LogResponseError("Failed to write a reply from proxy to device", buffer_.response);
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return FuseBridgeState::kClosing;
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}
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auto it = opcode_map_.find(buffer_.response.header.unique);
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if (it != opcode_map_.end()) {
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switch (it->second) {
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case FUSE_OPEN:
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if (buffer_.response.header.error == fuse::kFuseSuccess) {
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open_count_++;
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}
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break;
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case FUSE_RELEASE:
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if (open_count_ > 0) {
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open_count_--;
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} else {
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LOG(WARNING) << "Unexpected FUSE_RELEASE before opening a file.";
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break;
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}
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if (open_count_ == 0) {
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return FuseBridgeState::kClosing;
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}
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break;
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}
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opcode_map_.erase(it);
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}
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return FuseBridgeState::kWaitToReadEither;
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}
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FuseBridgeState ReadFromDevice(FuseBridgeLoopCallback* callback) {
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LOG(VERBOSE) << "ReadFromDevice";
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if (!buffer_.request.Read(device_fd_)) {
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return FuseBridgeState::kClosing;
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}
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const uint32_t opcode = buffer_.request.header.opcode;
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const uint64_t unique = buffer_.request.header.unique;
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LOG(VERBOSE) << "Read a fuse packet, opcode=" << opcode << " unique=" << unique;
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if (unique == 0) {
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return FuseBridgeState::kWaitToReadEither;
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}
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switch (opcode) {
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case FUSE_FORGET:
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// Do not reply to FUSE_FORGET.
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return FuseBridgeState::kWaitToReadEither;
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case FUSE_LOOKUP:
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case FUSE_GETATTR:
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case FUSE_OPEN:
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case FUSE_READ:
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case FUSE_WRITE:
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case FUSE_RELEASE:
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case FUSE_FSYNC:
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if (opcode == FUSE_OPEN || opcode == FUSE_RELEASE) {
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opcode_map_.emplace(buffer_.request.header.unique, opcode);
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}
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return WriteToProxy();
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case FUSE_INIT:
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buffer_.HandleInit();
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break;
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default:
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buffer_.HandleNotImpl();
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break;
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}
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if (!buffer_.response.Write(device_fd_)) {
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LogResponseError("Failed to write a response to device", buffer_.response);
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return FuseBridgeState::kClosing;
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}
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if (opcode == FUSE_INIT) {
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callback->OnMount(mount_id_);
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}
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return FuseBridgeState::kWaitToReadEither;
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}
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FuseBridgeState WriteToProxy() {
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switch (buffer_.request.WriteOrAgain(proxy_fd_)) {
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case ResultOrAgain::kSuccess:
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return FuseBridgeState::kWaitToReadEither;
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case ResultOrAgain::kFailure:
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LOG(ERROR) << "Failed to write a request to proxy:"
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<< " header.len=" << buffer_.request.header.len
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<< " header.opcode=" << buffer_.request.header.opcode
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<< " header.unique=" << buffer_.request.header.unique
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<< " header.nodeid=" << buffer_.request.header.nodeid;
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return FuseBridgeState::kClosing;
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case ResultOrAgain::kAgain:
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return FuseBridgeState::kWaitToWriteProxy;
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}
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}
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const int mount_id_;
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base::unique_fd device_fd_;
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base::unique_fd proxy_fd_;
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FuseBuffer buffer_;
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FuseBridgeState state_;
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FuseBridgeState last_state_;
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FuseBridgeEntryEvent last_device_events_;
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FuseBridgeEntryEvent last_proxy_events_;
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// Remember map between unique and opcode in fuse_in_header so that we can
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// refer the opcode later.
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std::unordered_map<uint64_t, uint32_t> opcode_map_;
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int open_count_;
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DISALLOW_COPY_AND_ASSIGN(FuseBridgeEntry);
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};
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class BridgeEpollController : private EpollController {
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public:
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BridgeEpollController(base::unique_fd&& poll_fd) : EpollController(std::move(poll_fd)) {}
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bool AddBridgePoll(FuseBridgeEntry* bridge) const {
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return InvokeControl(EPOLL_CTL_ADD, bridge);
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}
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bool UpdateOrDeleteBridgePoll(FuseBridgeEntry* bridge) const {
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return InvokeControl(
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bridge->state_ != FuseBridgeState::kClosing ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, bridge);
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}
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bool Wait(size_t bridge_count, std::unordered_set<FuseBridgeEntry*>* entries_out) {
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CHECK(entries_out);
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const size_t event_count = std::max<size_t>(bridge_count * 2, 1);
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if (!EpollController::Wait(event_count)) {
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return false;
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}
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entries_out->clear();
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for (const auto& event : events()) {
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FuseBridgeEntryEvent* const entry_event =
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reinterpret_cast<FuseBridgeEntryEvent*>(event.data.ptr);
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entry_event->events = event.events;
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entries_out->insert(entry_event->entry);
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}
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return true;
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}
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private:
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bool InvokeControl(int op, FuseBridgeEntry* bridge) const {
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LOG(VERBOSE) << "InvokeControl op=" << op << " bridge=" << bridge->mount_id_
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<< " state=" << static_cast<int>(bridge->state_)
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<< " last_state=" << static_cast<int>(bridge->last_state_);
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int last_device_events;
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int last_proxy_events;
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int device_events;
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int proxy_events;
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GetObservedEvents(bridge->last_state_, &last_device_events, &last_proxy_events);
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GetObservedEvents(bridge->state_, &device_events, &proxy_events);
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bool result = true;
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if (op != EPOLL_CTL_MOD || last_device_events != device_events) {
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result &= EpollController::InvokeControl(op, bridge->device_fd_, device_events,
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&bridge->last_device_events_);
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}
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if (op != EPOLL_CTL_MOD || last_proxy_events != proxy_events) {
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result &= EpollController::InvokeControl(op, bridge->proxy_fd_, proxy_events,
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&bridge->last_proxy_events_);
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}
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return result;
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}
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};
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std::recursive_mutex FuseBridgeLoop::mutex_;
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FuseBridgeLoop::FuseBridgeLoop() : opened_(true) {
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base::unique_fd epoll_fd(epoll_create1(EPOLL_CLOEXEC));
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if (epoll_fd.get() == -1) {
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PLOG(ERROR) << "Failed to open FD for epoll";
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opened_ = false;
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return;
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}
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epoll_controller_.reset(new BridgeEpollController(std::move(epoll_fd)));
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}
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FuseBridgeLoop::~FuseBridgeLoop() { CHECK(bridges_.empty()); }
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bool FuseBridgeLoop::AddBridge(int mount_id, base::unique_fd dev_fd, base::unique_fd proxy_fd) {
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LOG(VERBOSE) << "Adding bridge " << mount_id;
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std::unique_ptr<FuseBridgeEntry> bridge(
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new FuseBridgeEntry(mount_id, std::move(dev_fd), std::move(proxy_fd)));
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std::lock_guard<std::recursive_mutex> lock(mutex_);
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if (!opened_) {
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LOG(ERROR) << "Tried to add a mount to a closed bridge";
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return false;
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}
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if (bridges_.count(mount_id)) {
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LOG(ERROR) << "Tried to add a mount point that has already been added";
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return false;
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}
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if (!epoll_controller_->AddBridgePoll(bridge.get())) {
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return false;
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}
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bridges_.emplace(mount_id, std::move(bridge));
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return true;
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}
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bool FuseBridgeLoop::ProcessEventLocked(const std::unordered_set<FuseBridgeEntry*>& entries,
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FuseBridgeLoopCallback* callback) {
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for (auto entry : entries) {
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entry->Transfer(callback);
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if (!epoll_controller_->UpdateOrDeleteBridgePoll(entry)) {
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return false;
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}
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if (entry->IsClosing()) {
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const int mount_id = entry->mount_id();
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bridges_.erase(mount_id);
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callback->OnClosed(mount_id);
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if (bridges_.size() == 0) {
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// All bridges are now closed.
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return false;
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}
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}
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}
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return true;
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}
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void FuseBridgeLoop::Start(FuseBridgeLoopCallback* callback) {
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LOG(DEBUG) << "Start fuse bridge loop";
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std::unordered_set<FuseBridgeEntry*> entries;
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while (true) {
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const bool wait_result = epoll_controller_->Wait(bridges_.size(), &entries);
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LOG(VERBOSE) << "Receive epoll events";
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{
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std::lock_guard<std::recursive_mutex> lock(mutex_);
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if (!(wait_result && ProcessEventLocked(entries, callback))) {
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for (auto it = bridges_.begin(); it != bridges_.end();) {
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callback->OnClosed(it->second->mount_id());
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it = bridges_.erase(it);
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}
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opened_ = false;
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return;
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}
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}
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}
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}
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void FuseBridgeLoop::Lock() {
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mutex_.lock();
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}
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void FuseBridgeLoop::Unlock() {
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mutex_.unlock();
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}
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} // namespace fuse
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} // namespace android
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