Merge "Add CreateEmptyDevice and WaitForDevice APIs" (c037bdbc) · Commits · e / os / android_system_core

fs_mgr/libdm/dm.cpp

+25 −7

Original line number	Diff line number	Diff line
		@@ -170,19 +170,18 @@ static bool IsRecovery() {
		return access("/system/bin/recovery", F_OK) == 0;
		}

		bool DeviceMapper::CreateDevice(const std::string& name, const DmTable& table, std::string* path,
		const std::chrono::milliseconds& timeout_ms) {
		bool DeviceMapper::CreateEmptyDevice(const std::string& name) {
		std::string uuid = GenerateUuid();
		if (!CreateDevice(name, uuid)) {
		return false;
		return CreateDevice(name, uuid);
		}

		bool DeviceMapper::WaitForDevice(const std::string& name,
		const std::chrono::milliseconds& timeout_ms, std::string* path) {
		// We use the unique path for testing whether the device is ready. After
		// that, it's safe to use the dm-N path which is compatible with callers
		// that expect it to be formatted as such.
		std::string unique_path;
		if (!LoadTableAndActivate(name, table) \|\| !GetDeviceUniquePath(name, &unique_path) \|\|
		!GetDmDevicePathByName(name, path)) {
		if (!GetDeviceUniquePath(name, &unique_path) \|\| !GetDmDevicePathByName(name, path)) {
		DeleteDevice(name);
		return false;
		}
		@@ -208,6 +207,25 @@ bool DeviceMapper::CreateDevice(const std::string& name, const DmTable& table, s
		return true;
		}

		bool DeviceMapper::CreateDevice(const std::string& name, const DmTable& table, std::string* path,
		const std::chrono::milliseconds& timeout_ms) {
		if (!CreateEmptyDevice(name)) {
		return false;
		}

		if (!LoadTableAndActivate(name, table)) {
		DeleteDevice(name);
		return false;
		}

		if (!WaitForDevice(name, timeout_ms, path)) {
		DeleteDevice(name);
		return false;
		}

		return true;
		}

		bool DeviceMapper::GetDeviceUniquePath(const std::string& name, std::string* path) {
		struct dm_ioctl io;
		InitIo(&io, name);

fs_mgr/libdm/dm_test.cpp

+15 −0

Original line number	Diff line number	Diff line
		@@ -29,6 +29,7 @@
		#include <thread>

		#include <android-base/file.h>
		#include <android-base/scopeguard.h>
		#include <android-base/strings.h>
		#include <android-base/unique_fd.h>
		#include <gtest/gtest.h>
		@@ -679,3 +680,17 @@ TEST(libdm, DeleteDeviceDeferredWaitsForLastReference) {
		ASSERT_NE(0, access(path.c_str(), F_OK));
		ASSERT_EQ(ENOENT, errno);
		}

		TEST(libdm, CreateEmptyDevice) {
		DeviceMapper& dm = DeviceMapper::Instance();
		ASSERT_TRUE(dm.CreateEmptyDevice("empty-device"));
		auto guard = android::base::make_scope_guard([&]() { dm.DeleteDevice("empty-device", 5s); });

		// Empty device should be in suspended state.
		ASSERT_EQ(DmDeviceState::SUSPENDED, dm.GetState("empty-device"));

		std::string path;
		ASSERT_TRUE(dm.WaitForDevice("empty-device", 5s, &path));
		// Path should exist.
		ASSERT_EQ(0, access(path.c_str(), F_OK));
		}

fs_mgr/libdm/include/libdm/dm.h

+13 −0

Original line number	Diff line number	Diff line
		@@ -115,6 +115,19 @@ class DeviceMapper final {
		// - ACTIVE: resumes the device.
		bool ChangeState(const std::string& name, DmDeviceState state);

		// Creates empty device.
		// This supports a use case when a caller doesn't need a device straight away, but instead
		// asks kernel to create it beforehand, thus avoiding blocking itself from waiting for ueventd
		// to create user space paths.
		// Callers are expected to then activate their device by calling LoadTableAndActivate function.
		// To avoid race conditions, callers must still synchronize with ueventd by calling
		// WaitForDevice function.
		bool CreateEmptyDevice(const std::string& name);

		// Waits for device paths to be created in the user space.
		bool WaitForDevice(const std::string& name, const std::chrono::milliseconds& timeout_ms,
		std::string* path);

		// Creates a device, loads the given table, and activates it. If the device
		// is not able to be activated, it is destroyed, and false is returned.
		// After creation, \|path\| contains the result of calling