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// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/40285824): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#include "chrome/browser/ash/fileapi/fallback_copy_in_foreign_file.h"
#include <tuple>
#include "base/files/file_error_or.h"
#include "base/files/safe_base_name.h"
#include "base/memory/raw_ref.h"
#include "base/numerics/safe_conversions.h"
#include "base/strings/strcat.h"
#include "base/unguessable_token.h"
#include "net/base/io_buffer.h"
#include "net/base/net_errors.h"
#include "storage/browser/file_system/file_stream_writer.h"
#include "storage/browser/file_system/file_system_context.h"
#include "storage/browser/file_system/file_system_operation_runner.h"
#include "storage/browser/file_system/file_system_url.h"
#include "storage/common/file_system/file_system_util.h"
namespace ash {
namespace {
constexpr size_t kBufferSize = 65536; // 64 KiB.
storage::FileSystemURL CreateTempURL(const storage::FileSystemURL& dest_url) {
static const char kTempPrefix[] = ".chromium_temp_";
std::string token = base::UnguessableToken::Create().ToString();
return dest_url.CreateSibling(*base::SafeBaseName::Create(
base::FilePath::FromASCII(base::StrCat({kTempPrefix, token}))));
}
// Duplicates a FileSystemOperationContext, returning something (a unique_ptr)
// with independent ownership.
std::unique_ptr<storage::FileSystemOperationContext>
DuplicateFileSystemOperationContext(
storage::FileSystemOperationContext& original) {
return std::make_unique<storage::FileSystemOperationContext>(
original.file_system_context(), original.task_runner());
}
struct FileAndInt {
base::File file;
int n;
FileAndInt(base::File file_arg, int n_arg)
: file(std::move(file_arg)), n(n_arg) {}
};
// Helps implement FallbackCopyInForeignFile.
//
// It holds the state as the original FallbackCopyInForeignFile call is
// implemented by hopping between TaskRunners as part of Chrome storage's async
// C++ API.
//
// Those callbacks also hop between the original TaskRunner (typically "the IO
// thread" which, despite its name, doesn't allow blocking I/O) and the
// FileSystemOperationContext::task_runner(), which may block.
//
// ----
//
// "Copy in a foreign file (a 'real' kernel-visible file, identified by a
// base::FilePath named src_file_path) to a virtual-file-location (identified
// by a storage::FileSystemURL named dest_url)" is implemented in stages,
// writing the bytes to a temp_url before moving temp_url over dest_url.
//
// temp_url is a sibling (in the FileSystemURL::CreateSibling sense) of the
// dest_url. Its base name joins kTempPrefix and a base::UnguessableToken (a
// 128 bit randomly generated number) in string form.
//
// The stages are:
//
// 1. A new, temporary, virtual file is created at temp_url.
// 2. The src_file_path is opened for reading (as a base::File) and the
// temp_url is opened for writing (as a storage::FileStreamWriter).
// 3. Repeatedly Read from the source and Write to the temp_url. The loop
// ends when Read hits EOF (End Of File).
// 4. Flush (if necessary) the FileStreamWriter.
// 5. Rename temp_url to dest_url.
//
// If a stage encounters an error then the remaining stages are not performed.
// Nonetheless, Copier::Finish will be called regardless of failure (early
// exit) or success. Copier::Finish will remove the temp_url virtual file if
// necessary and then run the original callback that was passed to
// FallbackCopyInForeignFile.
//
// ----
//
// The FileStreamWriter is created for temp_url instead of dest_url. The
// indirection minimizes the amount of time that the dest_url virtual file is
// in a partially-written state. Step 3 (the read-write copy loop) can be
// time-consuming and relatively unreliable, if the virtual file system is
// backed by the cloud instead of local disk.
class Copier {
public:
Copier(storage::AsyncFileUtil& async_file_util,
std::unique_ptr<storage::FileSystemOperationContext> context,
const base::FilePath& src_file_path,
const storage::FileSystemURL& dest_url);
~Copier() = default;
Copier(const Copier&) = delete;
Copier& operator=(const Copier&) = delete;
void Start(storage::AsyncFileUtil::StatusCallback callback);
private:
void OnEnsureFileExists(base::File::Error result, bool created);
void OnOpen(base::File file);
void CallRead();
void OnRead(base::FileErrorOr<FileAndInt> result);
void CallWrite(scoped_refptr<net::DrainableIOBuffer> drainable_buffer);
void OnWrite(scoped_refptr<net::DrainableIOBuffer> drainable_buffer,
int result);
void CallFlushIfNecesssary();
void OnFlush(int result);
void OnGetFileInfo(base::File::Error result,
const base::File::Info& file_info);
void OnMoveTempToDest(base::File::Error result);
void Finish(base::File::Error result);
// Per the async_file_util.h comments, the async_file_util_ reference stays
// alive as long as the context_ is alive.
const raw_ref<storage::AsyncFileUtil> async_file_util_;
// This is the FileSystemOperationContext originally passed to
// FallbackCopyInForeignFile.
std::unique_ptr<storage::FileSystemOperationContext> context_;
const base::FilePath src_file_path_;
const storage::FileSystemURL dest_url_;
const storage::FileSystemURL temp_url_;
storage::AsyncFileUtil::StatusCallback callback_;
bool temp_url_needs_deleting_;
scoped_refptr<net::IOBuffer> io_buffer_ GUARDED_BY_CONTEXT(sequence_checker_);
std::unique_ptr<storage::FileStreamWriter> fs_writer_
GUARDED_BY_CONTEXT(sequence_checker_);
base::File file_ GUARDED_BY_CONTEXT(sequence_checker_);
SEQUENCE_CHECKER(sequence_checker_);
};
Copier::Copier(storage::AsyncFileUtil& async_file_util,
std::unique_ptr<storage::FileSystemOperationContext> context,
const base::FilePath& src_file_path,
const storage::FileSystemURL& dest_url)
: async_file_util_(async_file_util),
context_(std::move(context)),
src_file_path_(src_file_path),
dest_url_(dest_url),
temp_url_(CreateTempURL(dest_url)),
temp_url_needs_deleting_(false),
io_buffer_(base::MakeRefCounted<net::IOBufferWithSize>(kBufferSize)),
fs_writer_(nullptr),
file_(base::File::FILE_ERROR_FAILED) {}
void Copier::Start(storage::AsyncFileUtil::StatusCallback callback) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (src_file_path_.empty() || !dest_url_.is_valid() ||
!temp_url_.is_valid()) {
std::move(callback).Run(base::File::Error::FILE_ERROR_FAILED);
return;
}
callback_ = std::move(callback);
async_file_util_->EnsureFileExists(
DuplicateFileSystemOperationContext(*context_), temp_url_,
base::BindOnce(&Copier::OnEnsureFileExists,
// base::Unretained is safe as callback_ owns this.
base::Unretained(this)));
}
void Copier::OnEnsureFileExists(base::File::Error result, bool created) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (result != base::File::Error::FILE_OK) {
Finish(result);
return;
}
temp_url_needs_deleting_ = true;
fs_writer_ =
context_->file_system_context()->CreateFileStreamWriter(temp_url_, 0);
static constexpr auto open_file_off_the_io_thread =
[](const base::FilePath src_file_path) {
return base::File(src_file_path,
base::File::FLAG_OPEN | base::File::FLAG_READ);
};
context_->task_runner()->PostTaskAndReplyWithResult(
FROM_HERE, base::BindOnce(open_file_off_the_io_thread, src_file_path_),
base::BindOnce(&Copier::OnOpen,
// base::Unretained is safe as callback_ owns this.
base::Unretained(this)));
}
void Copier::OnOpen(base::File file) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (!file.IsValid()) {
Finish(base::File::Error::FILE_ERROR_NOT_FOUND);
return;
}
file_ = std::move(file);
CallRead();
}
void Copier::CallRead() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
static constexpr auto read_file_off_the_io_thread =
[](scoped_refptr<net::IOBuffer> buffer,
base::File file) -> base::FileErrorOr<FileAndInt> {
std::optional<size_t> num_bytes_read =
file.ReadAtCurrentPosNoBestEffort(buffer->first(kBufferSize));
if (!num_bytes_read.has_value()) {
return base::unexpected(base::File::GetLastFileError());
}
return FileAndInt(std::move(file),
base::checked_cast<int>(num_bytes_read.value()));
};
scoped_refptr<net::IOBuffer> buffer = io_buffer_;
base::File file = std::move(file_);
context_->task_runner()->PostTaskAndReplyWithResult(
FROM_HERE,
base::BindOnce(read_file_off_the_io_thread, std::move(buffer),
std::move(file)),
base::BindOnce(&Copier::OnRead,
// base::Unretained is safe as callback_ owns this.
base::Unretained(this)));
}
void Copier::OnRead(base::FileErrorOr<FileAndInt> result) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (!result.has_value()) {
Finish(result.error());
return;
}
file_ = std::move(result->file);
if (int num_bytes_read = result->n; num_bytes_read > 0) {
scoped_refptr<net::DrainableIOBuffer> drainable_buffer =
base::MakeRefCounted<net::DrainableIOBuffer>(io_buffer_.get(),
num_bytes_read);
CallWrite(std::move(drainable_buffer));
} else {
CallFlushIfNecesssary();
}
}
void Copier::CallWrite(scoped_refptr<net::DrainableIOBuffer> drainable_buffer) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
auto pair = base::SplitOnceCallback(
base::BindOnce(&Copier::OnWrite,
// base::Unretained is safe as callback_ owns this.
base::Unretained(this), drainable_buffer));
int write_result = fs_writer_->Write(drainable_buffer.get(),
drainable_buffer->BytesRemaining(),
std::move(pair.first));
if (write_result != net::ERR_IO_PENDING) { // The write was synchronous.
std::move(pair.second).Run(write_result);
}
}
void Copier::OnWrite(scoped_refptr<net::DrainableIOBuffer> drainable_buffer,
int result) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (result < 0) {
Finish(storage::NetErrorToFileError(result));
return;
} else if (result > drainable_buffer->BytesRemaining()) {
NOTREACHED();
}
drainable_buffer->DidConsume(result);
if (drainable_buffer->BytesRemaining() > 0) {
CallWrite(std::move(drainable_buffer));
return;
}
CallRead();
}
void Copier::CallFlushIfNecesssary() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (temp_url_.mount_option().flush_policy() ==
storage::FlushPolicy::NO_FLUSH_ON_COMPLETION) {
OnFlush(net::OK);
return;
}
auto pair = base::SplitOnceCallback(
base::BindOnce(&Copier::OnFlush,
// base::Unretained is safe as callback_ owns this.
base::Unretained(this)));
int flush_result =
fs_writer_->Flush(storage::FlushMode::kEndOfFile, std::move(pair.first));
if (flush_result != net::ERR_IO_PENDING) { // The flush was synchronous.
std::move(pair.second).Run(flush_result);
}
}
void Copier::OnFlush(int result) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (result < 0) {
Finish(storage::NetErrorToFileError(result));
return;
}
// Destroying this storage::FileStreamWriter closes the temp_url file. We're
// about to rename (or delete, on failure) that file, having finished writing
// and flushing its contents, but some AsyncFileUtil implementations disallow
// that on files that are still open.
fs_writer_.reset();
async_file_util_->GetFileInfo(
DuplicateFileSystemOperationContext(*context_), dest_url_,
{storage::FileSystemOperation::GetMetadataField::kIsDirectory},
base::BindOnce(&Copier::OnGetFileInfo,
// base::Unretained is safe as callback_ owns this.
base::Unretained(this)));
}
void Copier::OnGetFileInfo(base::File::Error result,
const base::File::Info& file_info) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (result == base::File::FILE_ERROR_NOT_FOUND) {
// No-op. It's OK if the dest_url_ didn't already exist.
} else if (result != base::File::FILE_OK) {
Finish(result);
return;
} else if (file_info.is_directory) {
Finish(base::File::FILE_ERROR_NOT_A_FILE);
return;
}
async_file_util_->MoveFileLocal(
DuplicateFileSystemOperationContext(*context_), temp_url_, dest_url_,
storage::FileSystemOperation::CopyOrMoveOptionSet(),
base::BindOnce(&Copier::OnMoveTempToDest,
// base::Unretained is safe as callback_ owns this.
base::Unretained(this)));
}
void Copier::OnMoveTempToDest(base::File::Error result) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
temp_url_needs_deleting_ = (result != base::File::Error::FILE_OK);
Finish(result);
}
void Copier::Finish(base::File::Error result) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (!temp_url_needs_deleting_) {
std::move(callback_).Run(result);
return;
}
// Normally, the storage::FileStreamWriter is created in OnEnsureFileExists
// and destroyed in OnFlush. However, Finish is still called if an error
// occurs in between. Just like the fs_writer_.reset() call in OnFlush, we
// have to call the storage::FileStreamWriter destructor to close the
// temp_url file before we try to delete that file.
//
// If we failed before OnEnsureFileExists or after OnFlush, reset is
// idempotent. A second reset is harmless.
fs_writer_.reset();
async_file_util_->DeleteFile(
DuplicateFileSystemOperationContext(*context_), temp_url_,
base::BindOnce(
[](storage::AsyncFileUtil::StatusCallback callback,
base::File::Error finish_result,
base::File::Error delete_file_result) {
// Ignore delete_file_result. It's like the "-f" in "rm -f". Just
// run the callback originally passed to FallbackCopyInForeignFile.
std::move(callback).Run(finish_result);
},
std::move(callback_), result));
}
} // namespace
void FallbackCopyInForeignFile(
storage::AsyncFileUtil& async_file_util,
std::unique_ptr<storage::FileSystemOperationContext> context,
const base::FilePath& src_file_path,
const storage::FileSystemURL& dest_url,
storage::AsyncFileUtil::StatusCallback callback) {
CHECK(context);
CHECK(callback);
std::unique_ptr<Copier> copier = std::make_unique<Copier>(
async_file_util, std::move(context), src_file_path, dest_url);
// Allows the unique pointer to be bound to the lambda below so the Copier
// stays alive until the operation completes.
Copier* raw_copier = copier.get();
raw_copier->Start(base::BindOnce(
[](std::unique_ptr<Copier> copier,
storage::AsyncFileUtil::StatusCallback callback,
base::File::Error result) { std::move(callback).Run(result); },
std::move(copier), std::move(callback)));
}
} // namespace ash
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