fs_mgr/libsnapshot/snapshot_writer.cpp

//
// Copyright (C) 2020 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#include <libsnapshot/snapshot_writer.h>

#include <android-base/file.h>
#include <android-base/logging.h>
#include <payload_consumer/file_descriptor.h>
#include "snapshot_reader.h"

namespace android {
namespace snapshot {

using android::base::borrowed_fd;
using android::base::unique_fd;
using chromeos_update_engine::FileDescriptor;

ISnapshotWriter::ISnapshotWriter(const CowOptions& options) : ICowWriter(options) {}

void ISnapshotWriter::SetSourceDevice(const std::string& source_device) {
    source_device_ = {source_device};
}

borrowed_fd ISnapshotWriter::GetSourceFd() {
    if (!source_device_) {
        LOG(ERROR) << "Attempted to read from source device but none was set";
        return borrowed_fd{-1};
    }

    if (source_fd_ < 0) {
        source_fd_.reset(open(source_device_->c_str(), O_RDONLY | O_CLOEXEC));
        if (source_fd_ < 0) {
            PLOG(ERROR) << "open " << *source_device_;
            return borrowed_fd{-1};
        }
    }
    return source_fd_;
}

CompressedSnapshotWriter::CompressedSnapshotWriter(const CowOptions& options)
    : ISnapshotWriter(options) {}

bool CompressedSnapshotWriter::SetCowDevice(android::base::unique_fd&& cow_device) {
    cow_device_ = std::move(cow_device);
    cow_ = std::make_unique<CowWriter>(options_);
    return true;
}

bool CompressedSnapshotWriter::Finalize() {
    return cow_->Finalize();
}

uint64_t CompressedSnapshotWriter::GetCowSize() {
    return cow_->GetCowSize();
}

std::unique_ptr<FileDescriptor> CompressedSnapshotWriter::OpenReader() {
    unique_fd cow_fd(dup(cow_device_.get()));
    if (cow_fd < 0) {
        PLOG(ERROR) << "dup COW device";
        return nullptr;
    }

    auto cow = std::make_unique<CowReader>();
    if (!cow->Parse(std::move(cow_fd))) {
        LOG(ERROR) << "Unable to read COW";
        return nullptr;
    }

    auto reader = std::make_unique<CompressedSnapshotReader>();
    if (!reader->SetCow(std::move(cow))) {
        LOG(ERROR) << "Unable to initialize COW reader";
        return nullptr;
    }
    if (source_device_) {
        reader->SetSourceDevice(*source_device_);
    }

    const auto& cow_options = options();
    reader->SetBlockDeviceSize(*cow_options.max_blocks * cow_options.block_size);

    return reader;
}

bool CompressedSnapshotWriter::EmitCopy(uint64_t new_block, uint64_t old_block) {
    return cow_->AddCopy(new_block, old_block);
}

bool CompressedSnapshotWriter::EmitRawBlocks(uint64_t new_block_start, const void* data,
                                             size_t size) {
    return cow_->AddRawBlocks(new_block_start, data, size);
}

bool CompressedSnapshotWriter::EmitZeroBlocks(uint64_t new_block_start, uint64_t num_blocks) {
    return cow_->AddZeroBlocks(new_block_start, num_blocks);
}

bool CompressedSnapshotWriter::EmitLabel(uint64_t label) {
    return cow_->AddLabel(label);
}

bool CompressedSnapshotWriter::Initialize() {
    return cow_->Initialize(cow_device_);
}

bool CompressedSnapshotWriter::InitializeAppend(uint64_t label) {
    return cow_->InitializeAppend(cow_device_, label);
}

OnlineKernelSnapshotWriter::OnlineKernelSnapshotWriter(const CowOptions& options)
    : ISnapshotWriter(options) {}

void OnlineKernelSnapshotWriter::SetSnapshotDevice(android::base::unique_fd&& snapshot_fd,
                                                   uint64_t cow_size) {
    snapshot_fd_ = std::move(snapshot_fd);
    cow_size_ = cow_size;
}

bool OnlineKernelSnapshotWriter::Finalize() {
    if (fsync(snapshot_fd_.get()) < 0) {
        PLOG(ERROR) << "fsync";
        return false;
    }
    return true;
}

bool OnlineKernelSnapshotWriter::EmitRawBlocks(uint64_t new_block_start, const void* data,
                                               size_t size) {
    uint64_t offset = new_block_start * options_.block_size;
    if (lseek(snapshot_fd_.get(), offset, SEEK_SET) < 0) {
        PLOG(ERROR) << "EmitRawBlocks lseek to offset " << offset;
        return false;
    }
    if (!android::base::WriteFully(snapshot_fd_, data, size)) {
        PLOG(ERROR) << "EmitRawBlocks write";
        return false;
    }
    return true;
}

bool OnlineKernelSnapshotWriter::EmitZeroBlocks(uint64_t new_block_start, uint64_t num_blocks) {
    std::string zeroes(options_.block_size, 0);
    for (uint64_t i = 0; i < num_blocks; i++) {
        if (!EmitRawBlocks(new_block_start + i, zeroes.data(), zeroes.size())) {
            return false;
        }
    }
    return true;
}

bool OnlineKernelSnapshotWriter::EmitCopy(uint64_t new_block, uint64_t old_block) {
    auto source_fd = GetSourceFd();
    if (source_fd < 0) {
        return false;
    }

    std::string buffer(options_.block_size, 0);
    uint64_t offset = old_block * options_.block_size;
    if (!android::base::ReadFullyAtOffset(source_fd, buffer.data(), buffer.size(), offset)) {
        PLOG(ERROR) << "EmitCopy read";
        return false;
    }
    return EmitRawBlocks(new_block, buffer.data(), buffer.size());
}

bool OnlineKernelSnapshotWriter::EmitLabel(uint64_t) {
    // Not Needed
    return true;
}

std::unique_ptr<FileDescriptor> OnlineKernelSnapshotWriter::OpenReader() {
    unique_fd fd(dup(snapshot_fd_.get()));
    if (fd < 0) {
        PLOG(ERROR) << "dup2 failed in OpenReader";
        return nullptr;
    }
    return std::make_unique<ReadFdFileDescriptor>(std::move(fd));
}

}  // namespace snapshot
}  // namespace android