Merge "libsnapshot: Add an open /dev/null mode for CowWriter." (56850e12) · Commits · e / os / android_system_core

fs_mgr/libsnapshot/cow_writer.cpp

+30 −8

Original line number	Diff line number	Diff line
		@@ -110,15 +110,28 @@ bool CowWriter::ParseOptions() {
		return true;
		}

		bool CowWriter::SetFd(android::base::borrowed_fd fd) {
		if (fd.get() < 0) {
		owned_fd_.reset(open("/dev/null", O_RDWR \| O_CLOEXEC));
		if (owned_fd_ < 0) {
		PLOG(ERROR) << "open /dev/null failed";
		return false;
		}
		fd_ = owned_fd_;
		is_dev_null_ = true;
		} else {
		fd_ = fd;
		}
		return true;
		}

		bool CowWriter::Initialize(unique_fd&& fd, OpenMode mode) {
		owned_fd_ = std::move(fd);
		return Initialize(borrowed_fd{owned_fd_}, mode);
		}

		bool CowWriter::Initialize(borrowed_fd fd, OpenMode mode) {
		fd_ = fd;

		if (!ParseOptions()) {
		if (!SetFd(fd) \|\| !ParseOptions()) {
		return false;
		}

		@@ -139,9 +152,7 @@ bool CowWriter::InitializeAppend(android::base::unique_fd&& fd, uint64_t label)
		}

		bool CowWriter::InitializeAppend(android::base::borrowed_fd fd, uint64_t label) {
		fd_ = fd;

		if (!ParseOptions()) {
		if (!SetFd(fd) \|\| !ParseOptions()) {
		return false;
		}

		@@ -304,7 +315,7 @@ bool CowWriter::EmitLabel(uint64_t label) {
		CowOperation op = {};
		op.type = kCowLabelOp;
		op.source = label;
		return WriteOperation(op) && !fsync(fd_.get());
		return WriteOperation(op) && Sync();
		}

		std::basic_string<uint8_t> CowWriter::Compress(const void* data, size_t length) {
		@@ -383,7 +394,7 @@ bool CowWriter::Finalize() {
		PLOG(ERROR) << "lseek ops failed";
		return false;
		}
		return !fsync(fd_.get());
		return Sync();
		}

		uint64_t CowWriter::GetCowSize() {
		@@ -424,5 +435,16 @@ bool CowWriter::WriteRawData(const void* data, size_t size) {
		return true;
		}

		bool CowWriter::Sync() {
		if (is_dev_null_) {
		return true;
		}
		if (fsync(fd_.get()) < 0) {
		PLOG(ERROR) << "fsync failed";
		return false;
		}
		return true;
		}

		} // namespace snapshot
		} // namespace android

fs_mgr/libsnapshot/include/libsnapshot/cow_writer.h

+7 −0

Original line number	Diff line number	Diff line
		@@ -90,6 +90,9 @@ class CowWriter : public ICowWriter {
		// If opening for write, the file starts from the beginning.
		// If opening for append, if the file has a footer, we start appending to the last op.
		// If the footer isn't found, the last label is considered corrupt, and dropped.
		//
		// If fd is < 0, the CowWriter will be opened against /dev/null. This is for
		// computing COW sizes without using storage space.
		bool Initialize(android::base::unique_fd&& fd, OpenMode mode = OpenMode::WRITE);
		bool Initialize(android::base::borrowed_fd fd, OpenMode mode = OpenMode::WRITE);
		// Set up a writer, assuming that the given label is the last valid label.
		@@ -119,6 +122,9 @@ class CowWriter : public ICowWriter {
		void AddOperation(const CowOperation& op);
		std::basic_string<uint8_t> Compress(const void* data, size_t length);

		bool SetFd(android::base::borrowed_fd fd);
		bool Sync();

		private:
		android::base::unique_fd owned_fd_;
		android::base::borrowed_fd fd_;
		@@ -126,6 +132,7 @@ class CowWriter : public ICowWriter {
		CowFooter footer_{};
		int compression_ = 0;
		uint64_t next_op_pos_ = 0;
		bool is_dev_null_ = false;

		// :TODO: this is not efficient, but stringstream ubsan aborts because some
		// bytes overflow a signed char.