Merge "dexopt: Restore old files when cancelled" (4b7d8858) · Commits · e / os / android_frameworks_native

cmds/installd/Android.bp

+12 −7

Original line number	Diff line number	Diff line
		@@ -28,6 +28,7 @@ cc_defaults {
		"dexopt.cpp",
		"execv_helper.cpp",
		"globals.cpp",
		"restorable_file.cpp",
		"run_dex2oat.cpp",
		"unique_file.cpp",
		"utils.cpp",
		@@ -80,7 +81,7 @@ cc_defaults {
		"-cert-err58-cpp",
		],
		tidy_flags: [
		"-warnings-as-errors=clang-analyzer-security,cert-"
		"-warnings-as-errors=clang-analyzer-security,cert-",
		],
		}

		@@ -132,7 +133,10 @@ cc_test_host {
		"unique_file.cpp",
		"execv_helper.cpp",
		],
		cflags: ["-Wall", "-Werror"],
		cflags: [
		"-Wall",
		"-Werror",
		],
		shared_libs: [
		"libbase",
		"server_configurable_flags",
		@@ -194,7 +198,7 @@ cc_binary {
		"libutils",
		],
		required: [
		"apexd"
		"apexd",
		],
		}

		@@ -213,7 +217,7 @@ cc_library_static {
		name: "libotapreoptparameters",
		cflags: [
		"-Wall",
		"-Werror"
		"-Werror",
		],

		srcs: ["otapreopt_parameters.cpp"],
		@@ -237,7 +241,7 @@ cc_binary {
		name: "otapreopt",
		cflags: [
		"-Wall",
		"-Werror"
		"-Werror",
		],

		srcs: [
		@@ -246,6 +250,7 @@ cc_binary {
		"globals.cpp",
		"otapreopt.cpp",
		"otapreopt_utils.cpp",
		"restorable_file.cpp",
		"run_dex2oat.cpp",
		"unique_file.cpp",
		"utils.cpp",
		@@ -296,5 +301,5 @@ sh_binary {
		// Script to migrate legacy obb data.
		sh_binary {
		name: "migrate_legacy_obb_data.sh",
		src: "migrate_legacy_obb_data.sh"
		src: "migrate_legacy_obb_data.sh",
		}

cmds/installd/dexopt.cpp

+84 −95

Original line number	Diff line number	Diff line
		@@ -58,9 +58,10 @@
		#include "dexopt_return_codes.h"
		#include "execv_helper.h"
		#include "globals.h"
		#include "installd_deps.h"
		#include "installd_constants.h"
		#include "installd_deps.h"
		#include "otapreopt_utils.h"
		#include "restorable_file.h"
		#include "run_dex2oat.h"
		#include "unique_file.h"
		#include "utils.h"
		@@ -309,12 +310,6 @@ static bool IsBootClassPathProfilingEnable() {
		return profile_boot_class_path == "true";
		}

		static void UnlinkIgnoreResult(const std::string& path) {
		if (unlink(path.c_str()) < 0) {
		PLOG(ERROR) << "Failed to unlink " << path;
		}
		}

		/*
		* Whether dexopt should use a swap file when compiling an APK.
		*
		@@ -988,42 +983,34 @@ static bool create_oat_out_path(const char* apk_path, const char* instruction_se
		}

		// (re)Creates the app image if needed.
		UniqueFile maybe_open_app_image(const std::string& out_oat_path,
		bool generate_app_image, bool is_public, int uid, bool is_secondary_dex) {

		RestorableFile maybe_open_app_image(const std::string& out_oat_path, bool generate_app_image,
		bool is_public, int uid, bool is_secondary_dex) {
		const std::string image_path = create_image_filename(out_oat_path);
		if (image_path.empty()) {
		// Happens when the out_oat_path has an unknown extension.
		return UniqueFile();
		return RestorableFile();
		}

		// In case there is a stale image, remove it now. Ignore any error.
		unlink(image_path.c_str());

		// Not enabled, exit.
		if (!generate_app_image) {
		return UniqueFile();
		RestorableFile::RemoveAllFiles(image_path);
		return RestorableFile();
		}
		std::string app_image_format = GetProperty("dalvik.vm.appimageformat", "");
		if (app_image_format.empty()) {
		return UniqueFile();
		RestorableFile::RemoveAllFiles(image_path);
		return RestorableFile();
		}
		// Recreate is true since we do not want to modify a mapped image. If the app is
		// already running and we modify the image file, it can cause crashes (b/27493510).
		UniqueFile image_file(
		open_output_file(image_path.c_str(), true /recreate/, 0600 /permissions/),
		image_path,
		UnlinkIgnoreResult);
		// If the app is already running and we modify the image file, it can cause crashes
		// (b/27493510).
		RestorableFile image_file = RestorableFile::CreateWritableFile(image_path,
		/permissions/ 0600);
		if (image_file.fd() < 0) {
		// Could not create application image file. Go on since we can compile without it.
		LOG(ERROR) << "installd could not create '" << image_path
		<< "' for image file during dexopt";
		// If we have a valid image file path but no image fd, explicitly erase the image file.
		if (unlink(image_path.c_str()) < 0) {
		if (errno != ENOENT) {
		PLOG(ERROR) << "Couldn't unlink image file " << image_path;
		}
		}
		// If we have a valid image file path but cannot create tmp file, reset it.
		image_file.reset();
		} else if (!set_permissions_and_ownership(
		image_file.fd(), is_public, uid, image_path.c_str(), is_secondary_dex)) {
		ALOGE("installd cannot set owner '%s' for image during dexopt\n", image_path.c_str());
		@@ -1097,9 +1084,9 @@ UniqueFile maybe_open_reference_profile(const std::string& pkgname,
		// Opens the vdex files and assigns the input fd to in_vdex_wrapper and the output fd to
		// out_vdex_wrapper. Returns true for success or false in case of errors.
		bool open_vdex_files_for_dex2oat(const char* apk_path, const char* out_oat_path, int dexopt_needed,
		const char* instruction_set, bool is_public, int uid, bool is_secondary_dex,
		bool profile_guided, UniqueFile* in_vdex_wrapper,
		UniqueFile* out_vdex_wrapper) {
		const char* instruction_set, bool is_public, int uid,
		bool is_secondary_dex, bool profile_guided,
		UniqueFile* in_vdex_wrapper, RestorableFile* out_vdex_wrapper) {
		CHECK(in_vdex_wrapper != nullptr);
		CHECK(out_vdex_wrapper != nullptr);
		// Open the existing VDEX. We do this before creating the new output VDEX, which will
		@@ -1114,6 +1101,14 @@ bool open_vdex_files_for_dex2oat(const char* apk_path, const char* out_oat_path,
		return false;
		}

		// Create work file first. All files will be deleted when it fails.
		*out_vdex_wrapper = RestorableFile::CreateWritableFile(out_vdex_path_str,
		/permissions/ 0644);
		if (out_vdex_wrapper->fd() < 0) {
		ALOGE("installd cannot open vdex '%s' during dexopt\n", out_vdex_path_str.c_str());
		return false;
		}

		bool update_vdex_in_place = false;
		if (dexopt_action != DEX2OAT_FROM_SCRATCH) {
		// Open the possibly existing vdex. If none exist, we pass -1 to dex2oat for input-vdex-fd.
		@@ -1145,41 +1140,19 @@ bool open_vdex_files_for_dex2oat(const char* apk_path, const char* out_oat_path,
		(dexopt_action == DEX2OAT_FOR_BOOT_IMAGE) &&
		!profile_guided;
		if (update_vdex_in_place) {
		// dex2oat marks it invalid anyway. So delete it and set work file fd.
		unlink(in_vdex_path_str.c_str());
		// Open the file read-write to be able to update it.
		in_vdex_wrapper->reset(open(in_vdex_path_str.c_str(), O_RDWR, 0),
		in_vdex_path_str);
		if (in_vdex_wrapper->fd() == -1) {
		// If we failed to open the file, we cannot update it in place.
		update_vdex_in_place = false;
		}
		} else {
		in_vdex_wrapper->reset(open(in_vdex_path_str.c_str(), O_RDONLY, 0),
		in_vdex_path_str);
		}
		}

		// If we are updating the vdex in place, we do not need to recreate a vdex,
		// and can use the same existing one.
		if (update_vdex_in_place) {
		// We unlink the file in case the invocation of dex2oat fails, to ensure we don't
		// have bogus stale vdex files.
		out_vdex_wrapper->reset(
		in_vdex_wrapper->fd(),
		out_vdex_path_str,
		UnlinkIgnoreResult);
		in_vdex_wrapper->reset(out_vdex_wrapper->fd(), in_vdex_path_str);
		// Disable auto close for the in wrapper fd (it will be done when destructing the out
		// wrapper).
		in_vdex_wrapper->DisableAutoClose();
		} else {
		out_vdex_wrapper->reset(
		open_output_file(out_vdex_path_str.c_str(), /recreate/true, /permissions/0644),
		out_vdex_path_str,
		UnlinkIgnoreResult);
		if (out_vdex_wrapper->fd() < 0) {
		ALOGE("installd cannot open vdex'%s' during dexopt\n", out_vdex_path_str.c_str());
		return false;
		in_vdex_wrapper->reset(open(in_vdex_path_str.c_str(), O_RDONLY, 0),
		in_vdex_path_str);
		}
		}

		if (!set_permissions_and_ownership(out_vdex_wrapper->fd(), is_public, uid,
		out_vdex_path_str.c_str(), is_secondary_dex)) {
		ALOGE("installd cannot set owner '%s' for vdex during dexopt\n", out_vdex_path_str.c_str());
		@@ -1191,16 +1164,13 @@ bool open_vdex_files_for_dex2oat(const char* apk_path, const char* out_oat_path,
		}

		// Opens the output oat file for the given apk.
		UniqueFile open_oat_out_file(const char* apk_path, const char* oat_dir,
		bool is_public, int uid, const char* instruction_set, bool is_secondary_dex) {
		RestorableFile open_oat_out_file(const char* apk_path, const char* oat_dir, bool is_public, int uid,
		const char* instruction_set, bool is_secondary_dex) {
		char out_oat_path[PKG_PATH_MAX];
		if (!create_oat_out_path(apk_path, instruction_set, oat_dir, is_secondary_dex, out_oat_path)) {
		return UniqueFile();
		return RestorableFile();
		}
		UniqueFile oat(
		open_output_file(out_oat_path, /recreate/true, /permissions/0644),
		out_oat_path,
		UnlinkIgnoreResult);
		RestorableFile oat = RestorableFile::CreateWritableFile(out_oat_path, /permissions/ 0644);
		if (oat.fd() < 0) {
		PLOG(ERROR) << "installd cannot open output during dexopt" << out_oat_path;
		} else if (!set_permissions_and_ownership(
		@@ -1839,6 +1809,7 @@ int dexopt(const char* dex_path, uid_t uid, const char* pkgname, const char* ins
		if (sec_dex_result == kSecondaryDexOptProcessOk) {
		oat_dir = oat_dir_str.c_str();
		if (dexopt_needed == NO_DEXOPT_NEEDED) {
		*completed = true;
		return 0; // Nothing to do, report success.
		}
		} else if (sec_dex_result == kSecondaryDexOptProcessCancelled) {
		@@ -1874,8 +1845,8 @@ int dexopt(const char* dex_path, uid_t uid, const char* pkgname, const char* ins
		}

		// Create the output OAT file.
		UniqueFile out_oat = open_oat_out_file(dex_path, oat_dir, is_public, uid,
		instruction_set, is_secondary_dex);
		RestorableFile out_oat =
		open_oat_out_file(dex_path, oat_dir, is_public, uid, instruction_set, is_secondary_dex);
		if (out_oat.fd() < 0) {
		*error_msg = "Could not open out oat file.";
		return -1;
		@@ -1883,7 +1854,7 @@ int dexopt(const char* dex_path, uid_t uid, const char* pkgname, const char* ins

		// Open vdex files.
		UniqueFile in_vdex;
		UniqueFile out_vdex;
		RestorableFile out_vdex;
		if (!open_vdex_files_for_dex2oat(dex_path, out_oat.path().c_str(), dexopt_needed,
		instruction_set, is_public, uid, is_secondary_dex, profile_guided, &in_vdex,
		&out_vdex)) {
		@@ -1919,8 +1890,8 @@ int dexopt(const char* dex_path, uid_t uid, const char* pkgname, const char* ins
		}

		// Create the app image file if needed.
		UniqueFile out_image = maybe_open_app_image(
		out_oat.path(), generate_app_image, is_public, uid, is_secondary_dex);
		RestorableFile out_image = maybe_open_app_image(out_oat.path(), generate_app_image, is_public,
		uid, is_secondary_dex);

		UniqueFile dex_metadata;
		if (dex_metadata_path != nullptr) {
		@@ -1953,30 +1924,18 @@ int dexopt(const char* dex_path, uid_t uid, const char* pkgname, const char* ins
		LOG(VERBOSE) << "DexInv: --- BEGIN '" << dex_path << "' ---";

		RunDex2Oat runner(dex2oat_bin, execv_helper.get());
		runner.Initialize(out_oat,
		out_vdex,
		out_image,
		in_dex,
		in_vdex,
		dex_metadata,
		reference_profile,
		class_loader_context,
		join_fds(context_input_fds),
		swap_fd.get(),
		instruction_set,
		compiler_filter,
		debuggable,
		boot_complete,
		for_restore,
		target_sdk_version,
		enable_hidden_api_checks,
		generate_compact_dex,
		use_jitzygote_image,
		runner.Initialize(out_oat.GetUniqueFile(), out_vdex.GetUniqueFile(), out_image.GetUniqueFile(),
		in_dex, in_vdex, dex_metadata, reference_profile, class_loader_context,
		join_fds(context_input_fds), swap_fd.get(), instruction_set, compiler_filter,
		debuggable, boot_complete, for_restore, target_sdk_version,
		enable_hidden_api_checks, generate_compact_dex, use_jitzygote_image,
		compilation_reason);

		bool cancelled = false;
		pid_t pid = dexopt_status_->check_cancellation_and_fork(&cancelled);
		if (cancelled) {
		*completed = false;
		reference_profile.DisableCleanup();
		return 0;
		}
		if (pid == 0) {
		@@ -2004,6 +1963,7 @@ int dexopt(const char* dex_path, uid_t uid, const char* pkgname, const char* ins
		LOG(VERBOSE) << "DexInv: --- END '" << dex_path << "' --- cancelled";
		// cancelled, not an error
		*completed = false;
		reference_profile.DisableCleanup();
		return 0;
		}
		LOG(VERBOSE) << "DexInv: --- END '" << dex_path << "' --- status=0x"
		@@ -2013,13 +1973,42 @@ int dexopt(const char* dex_path, uid_t uid, const char* pkgname, const char* ins
		}
		}

		// TODO(b/156537504) Implement SWAP of completed files
		// We've been successful, don't delete output.
		out_oat.DisableCleanup();
		out_vdex.DisableCleanup();
		out_image.DisableCleanup();
		// dex2oat ran successfully, so profile is safe to keep.
		reference_profile.DisableCleanup();

		// We've been successful, commit work files.
		// If committing (=renaming tmp to regular) fails, try to restore backup files.
		// If restoring fails as well, as a last resort, remove all files.
		if (!out_oat.CreateBackupFile() \|\| !out_vdex.CreateBackupFile() \|\|
		!out_image.CreateBackupFile()) {
		// Renaming failure can mean that the original file may not be accessible from installd.
		LOG(ERROR) << "Cannot create backup file from existing file, file in wrong state?"
		<< ", out_oat:" << out_oat.path() << " ,out_vdex:" << out_vdex.path()
		<< " ,out_image:" << out_image.path();
		out_oat.ResetAndRemoveAllFiles();
		out_vdex.ResetAndRemoveAllFiles();
		out_image.ResetAndRemoveAllFiles();
		return -1;
		}
		if (!out_oat.CommitWorkFile() \|\| !out_vdex.CommitWorkFile() \|\| !out_image.CommitWorkFile()) {
		LOG(ERROR) << "Cannot commit, out_oat:" << out_oat.path()
		<< " ,out_vdex:" << out_vdex.path() << " ,out_image:" << out_image.path();
		if (!out_oat.RestoreBackupFile() \|\| !out_vdex.RestoreBackupFile() \|\|
		!out_image.RestoreBackupFile()) {
		LOG(ERROR) << "Cannot cancel commit, out_oat:" << out_oat.path()
		<< " ,out_vdex:" << out_vdex.path() << " ,out_image:" << out_image.path();
		// Restoring failed.
		out_oat.ResetAndRemoveAllFiles();
		out_vdex.ResetAndRemoveAllFiles();
		out_image.ResetAndRemoveAllFiles();
		}
		return -1;
		}
		// Now remove remaining backup files.
		out_oat.RemoveBackupFile();
		out_vdex.RemoveBackupFile();
		out_image.RemoveBackupFile();

		*completed = true;
		return 0;
		}

cmds/installd/restorable_file.cpp

0 → 100644

+161 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2021 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 "restorable_file.h"

		#include <string>

		#include <fcntl.h>
		#include <sys/stat.h>
		#include <sys/types.h>
		#include <unistd.h>

		#include <android-base/logging.h>
		#include <android-base/stringprintf.h>

		namespace {

		constexpr char kTmpFileSuffix[] = ".tmp";
		constexpr char kBackupFileSuffix[] = ".backup";

		std::string GetTmpFilePath(const std::string& path) {
		return android::base::StringPrintf("%s%s", path.c_str(), kTmpFileSuffix);
		}

		std::string GetBackupFilePath(const std::string& path) {
		return android::base::StringPrintf("%s%s", path.c_str(), kBackupFileSuffix);
		}

		void UnlinkPossiblyNonExistingFile(const std::string& path) {
		if (unlink(path.c_str()) < 0) {
		if (errno != ENOENT && errno != EROFS) { // EROFS reported even if it does not exist.
		PLOG(ERROR) << "Cannot unlink: " << path;
		}
		}
		}

		// Check if file for the given path exists
		bool FileExists(const std::string& path) {
		struct stat st;
		return ::stat(path.c_str(), &st) == 0;
		}

		} // namespace

		namespace android {
		namespace installd {

		RestorableFile::RestorableFile() : RestorableFile(-1, "") {}

		RestorableFile::RestorableFile(int value, const std::string& path) : unique_file_(value, path) {
		// As cleanup is null, this does not make much difference but use unique_file_ only for closing
		// tmp file.
		unique_file_.DisableCleanup();
		}

		RestorableFile::~RestorableFile() {
		reset();
		}

		void RestorableFile::reset() {
		// need to copy before reset clears it.
		std::string path(unique_file_.path());
		unique_file_.reset();
		if (!path.empty()) {
		UnlinkPossiblyNonExistingFile(GetTmpFilePath(path));
		}
		}

		bool RestorableFile::CreateBackupFile() {
		if (path().empty() \|\| !FileExists(path())) {
		return true;
		}
		std::string backup = GetBackupFilePath(path());
		UnlinkPossiblyNonExistingFile(backup);
		if (rename(path().c_str(), backup.c_str()) < 0) {
		PLOG(ERROR) << "Cannot rename " << path() << " to " << backup;
		return false;
		}
		return true;
		}

		bool RestorableFile::CommitWorkFile() {
		std::string path(unique_file_.path());
		// Keep the path with Commit for debugging purpose.
		unique_file_.reset(-1, path);
		if (!path.empty()) {
		if (rename(GetTmpFilePath(path).c_str(), path.c_str()) < 0) {
		PLOG(ERROR) << "Cannot rename " << GetTmpFilePath(path) << " to " << path;
		// Remove both files as renaming can fail due to the original file as well.
		UnlinkPossiblyNonExistingFile(path);
		UnlinkPossiblyNonExistingFile(GetTmpFilePath(path));
		return false;
		}
		}

		return true;
		}

		bool RestorableFile::RestoreBackupFile() {
		std::string backup = GetBackupFilePath(path());
		if (path().empty() \|\| !FileExists(backup)) {
		return true;
		}
		UnlinkPossiblyNonExistingFile(path());
		if (rename(backup.c_str(), path().c_str()) < 0) {
		PLOG(ERROR) << "Cannot rename " << backup << " to " << path();
		return false;
		}
		return true;
		}

		void RestorableFile::RemoveBackupFile() {
		UnlinkPossiblyNonExistingFile(GetBackupFilePath(path()));
		}

		const UniqueFile& RestorableFile::GetUniqueFile() const {
		return unique_file_;
		}

		void RestorableFile::ResetAndRemoveAllFiles() {
		std::string path(unique_file_.path());
		reset();
		RemoveAllFiles(path);
		}

		RestorableFile RestorableFile::CreateWritableFile(const std::string& path, int permissions) {
		std::string tmp_file_path = GetTmpFilePath(path);
		// If old tmp file exists, delete it.
		UnlinkPossiblyNonExistingFile(tmp_file_path);
		int fd = -1;
		if (!path.empty()) {
		fd = open(tmp_file_path.c_str(), O_RDWR \| O_CREAT, permissions);
		if (fd < 0) {
		PLOG(ERROR) << "Cannot create file: " << tmp_file_path;
		}
		}
		RestorableFile rf(fd, path);
		return rf;
		}

		void RestorableFile::RemoveAllFiles(const std::string& path) {
		UnlinkPossiblyNonExistingFile(GetTmpFilePath(path));
		UnlinkPossiblyNonExistingFile(GetBackupFilePath(path));
		UnlinkPossiblyNonExistingFile(path);
		}

		} // namespace installd
		} // namespace android

cmds/installd/restorable_file.h

0 → 100644

+107 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2021 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.
		*/

		#ifndef ANDROID_INSTALLD_RESTORABLE_FILE_H
		#define ANDROID_INSTALLD_RESTORABLE_FILE_H

		#include <functional>
		#include <string>

		#include "unique_file.h"

		namespace android {
		namespace installd {

		// This is a file abstraction which allows restoring to the original file while temporary work
		// file is updated.
		//
		// Typical flow for this API will be:
		// RestorableFile rf = RestorableFile::CreateWritableFile(...)
		// write to file using file descriptor acquired from: rf.fd()
		// Make work file into a regular file with: rf.CommitWorkFile()
		// Or throw away the work file by destroying the instance without calling CommitWorkFile().
		// The temporary work file is closed / removed when an instance is destroyed without calling
		// CommitWorkFile(). The original file, if CommitWorkFile() is not called, will be kept.
		//
		// For safer restoration of original file when commit fails, following 3 steps can be taken:
		// 1. CreateBackupFile(): This renames an existing regular file into a separate backup file.
		// 2. CommitWorkFile(): Rename the work file into the regular file.
		// 3. RemoveBackupFile(): Removes the backup file
		// If CommitWorkFile fails, client can call RestoreBackupFile() which will restore regular file from
		// the backup.
		class RestorableFile {
		public:
		// Creates invalid instance with no fd (=-1) and empty path.
		RestorableFile();
		RestorableFile(RestorableFile&& other) = default;
		~RestorableFile();

		// Passes all contents of other file into the current file.
		// Files kept for the current file will be either deleted or committed depending on
		// CommitWorkFile() and DisableCleanUp() calls made before this.
		RestorableFile& operator=(RestorableFile&& other) = default;

		// Gets file descriptor for backing work (=temporary) file. If work file does not exist, it will
		// return -1.
		int fd() const { return unique_file_.fd(); }

		// Gets the path name for the regular file (not temporary file).
		const std::string& path() const { return unique_file_.path(); }

		// Closes work file, deletes it and resets all internal states into default states.
		void reset();

		// Closes work file and closes all files including work file, backup file and regular file.
		void ResetAndRemoveAllFiles();

		// Creates a backup file by renaming existing regular file. This will return false if renaming
		// fails. If regular file for renaming does not exist, it will return true.
		bool CreateBackupFile();

		// Closes existing work file and makes it a regular file.
		// Note that the work file is closed and fd() will return -1 after this. path() will still
		// return the original path.
		// This will return false when committing fails (=cannot rename). Both the regular file and tmp
		// file will be deleted when it fails.
		bool CommitWorkFile();

		// Cancels the commit and restores the backup file into the regular one. If renaming fails,
		// it will return false. This returns true if the backup file does not exist.
		bool RestoreBackupFile();

		// Removes the backup file.
		void RemoveBackupFile();

		// Gets UniqueFile with the same path and fd() pointing to the work file.
		const UniqueFile& GetUniqueFile() const;

		// Creates writable RestorableFile. This involves creating tmp file for writing.
		static RestorableFile CreateWritableFile(const std::string& path, int permissions);

		// Removes the specified file together with tmp file generated as RestorableFile.
		static void RemoveAllFiles(const std::string& path);

		private:
		RestorableFile(int value, const std::string& path);

		// Used as a storage for work file fd and path string.
		UniqueFile unique_file_;
		};

		} // namespace installd
		} // namespace android

		#endif // ANDROID_INSTALLD_RESTORABLE_FILE_H

cmds/installd/tests/Android.bp

+20 −0

Original line number	Diff line number	Diff line
		@@ -188,3 +188,23 @@ cc_test {
		"libotapreoptparameters",
		],
		}

		cc_test {
		name: "installd_file_test",
		test_suites: ["device-tests"],
		clang: true,
		srcs: ["installd_file_test.cpp"],
		cflags: [
		"-Wall",
		"-Werror",
		],
		shared_libs: [
		"libbase",
		"libcutils",
		"libutils",
		],
		static_libs: [
		"libinstalld",
		"liblog",
		],
		}