Perform a consistency check before deleting snapshots. am: 91b351ea7b (31c26b69) · Commits · e / os / android_system_core

fs_mgr/libsnapshot/android/snapshot/snapshot.proto

+7 −0

Original line number	Diff line number	Diff line
		@@ -158,6 +158,13 @@ enum MergeFailureCode {
		ExpectedMergeTarget = 11;
		UnmergedSectorsAfterCompletion = 12;
		UnexpectedMergeState = 13;
		GetCowPathConsistencyCheck = 14;
		OpenCowConsistencyCheck = 15;
		ParseCowConsistencyCheck = 16;
		OpenCowDirectConsistencyCheck = 17;
		MemAlignConsistencyCheck = 18;
		DirectReadConsistencyCheck = 19;
		WrongMergeCountConsistencyCheck = 20;
		};

		// Next: 8

fs_mgr/libsnapshot/include/libsnapshot/cow_reader.h

+2 −3

Original line number	Diff line number	Diff line
		@@ -143,12 +143,11 @@ class CowReader : public ICowReader {

		void InitializeMerge();

		// Number of copy, replace, and zero ops. Set if InitializeMerge is called.
		void set_total_data_ops(uint64_t size) { total_data_ops_ = size; }

		uint64_t total_data_ops() { return total_data_ops_; }

		// Number of copy ops. Set if InitializeMerge is called.
		void set_copy_ops(uint64_t size) { copy_ops_ = size; }

		uint64_t total_copy_ops() { return copy_ops_; }

		void CloseCowFd() { owned_fd_ = {}; }

fs_mgr/libsnapshot/include/libsnapshot/snapshot.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -603,6 +603,8 @@ class SnapshotManager final : public ISnapshotManager {
		MergeResult CheckMergeState(LockedFile* lock, const std::function<bool()>& before_cancel);
		MergeResult CheckTargetMergeState(LockedFile* lock, const std::string& name,
		const SnapshotUpdateStatus& update_status);
		MergeFailureCode CheckMergeConsistency(LockedFile* lock, const std::string& name,
		const SnapshotStatus& update_status);

		// Interact with status files under /metadata/ota/snapshots.
		bool WriteSnapshotStatus(LockedFile* lock, const SnapshotStatus& status);

fs_mgr/libsnapshot/snapshot.cpp

+91 −8

Original line number	Diff line number	Diff line
		@@ -1126,6 +1126,11 @@ auto SnapshotManager::CheckTargetMergeState(LockedFile* lock, const std::string&
		return MergeResult(UpdateState::Merging);
		}

		auto code = CheckMergeConsistency(lock, name, snapshot_status);
		if (code != MergeFailureCode::Ok) {
		return MergeResult(UpdateState::MergeFailed, code);
		}

		// Merging is done. First, update the status file to indicate the merge
		// is complete. We do this before calling OnSnapshotMergeComplete, even
		// though this means the write is potentially wasted work (since in the
		@@ -1144,6 +1149,91 @@ auto SnapshotManager::CheckTargetMergeState(LockedFile* lock, const std::string&
		return MergeResult(UpdateState::MergeCompleted, MergeFailureCode::Ok);
		}

		// This returns the backing device, not the dm-user layer.
		static std::string GetMappedCowDeviceName(const std::string& snapshot,
		const SnapshotStatus& status) {
		// If no partition was created (the COW exists entirely on /data), the
		// device-mapper layering is different than if we had a partition.
		if (status.cow_partition_size() == 0) {
		return GetCowImageDeviceName(snapshot);
		}
		return GetCowName(snapshot);
		}

		MergeFailureCode SnapshotManager::CheckMergeConsistency(LockedFile* lock, const std::string& name,
		const SnapshotStatus& status) {
		CHECK(lock);

		if (!status.compression_enabled()) {
		// Do not try to verify old-style COWs yet.
		return MergeFailureCode::Ok;
		}

		auto& dm = DeviceMapper::Instance();

		std::string cow_image_name = GetMappedCowDeviceName(name, status);
		std::string cow_image_path;
		if (!dm.GetDmDevicePathByName(cow_image_name, &cow_image_path)) {
		LOG(ERROR) << "Failed to get path for cow device: " << cow_image_name;
		return MergeFailureCode::GetCowPathConsistencyCheck;
		}

		// First pass, count # of ops.
		size_t num_ops = 0;
		{
		unique_fd fd(open(cow_image_path.c_str(), O_RDONLY \| O_CLOEXEC));
		if (fd < 0) {
		PLOG(ERROR) << "Failed to open " << cow_image_name;
		return MergeFailureCode::OpenCowConsistencyCheck;
		}

		CowReader reader;
		if (!reader.Parse(std::move(fd))) {
		LOG(ERROR) << "Failed to parse cow " << cow_image_path;
		return MergeFailureCode::ParseCowConsistencyCheck;
		}

		for (auto iter = reader.GetOpIter(); !iter->Done(); iter->Next()) {
		if (!IsMetadataOp(iter->Get())) {
		num_ops++;
		}
		}
		}

		// Second pass, try as hard as we can to get the actual number of blocks
		// the system thinks is merged.
		unique_fd fd(open(cow_image_path.c_str(), O_RDONLY \| O_DIRECT \| O_SYNC \| O_CLOEXEC));
		if (fd < 0) {
		PLOG(ERROR) << "Failed to open direct " << cow_image_name;
		return MergeFailureCode::OpenCowDirectConsistencyCheck;
		}

		void* addr;
		size_t page_size = getpagesize();
		if (posix_memalign(&addr, page_size, page_size) < 0) {
		PLOG(ERROR) << "posix_memalign with page size " << page_size;
		return MergeFailureCode::MemAlignConsistencyCheck;
		}

		// COWs are always at least 2MB, this is guaranteed in snapshot creation.
		std::unique_ptr<void, decltype(&::free)> buffer(addr, ::free);
		if (!android::base::ReadFully(fd, buffer.get(), page_size)) {
		PLOG(ERROR) << "Direct read failed " << cow_image_name;
		return MergeFailureCode::DirectReadConsistencyCheck;
		}

		auto header = reinterpret_cast<CowHeader*>(buffer.get());
		if (header->num_merge_ops != num_ops) {
		LOG(ERROR) << "COW consistency check failed, expected " << num_ops << " to be merged, "
		<< "but " << header->num_merge_ops << " were actually recorded.";
		LOG(ERROR) << "Aborting merge progress for snapshot " << name
		<< ", will try again next boot";
		return MergeFailureCode::WrongMergeCountConsistencyCheck;
		}

		return MergeFailureCode::Ok;
		}

		MergeFailureCode SnapshotManager::MergeSecondPhaseSnapshots(LockedFile* lock) {
		std::vector<std::string> snapshots;
		if (!ListSnapshots(lock, &snapshots)) {
		@@ -1429,14 +1519,7 @@ bool SnapshotManager::PerformInitTransition(InitTransition transition,
		continue;
		}

		// If no partition was created (the COW exists entirely on /data), the
		// device-mapper layering is different than if we had a partition.
		std::string cow_image_name;
		if (snapshot_status.cow_partition_size() == 0) {
		cow_image_name = GetCowImageDeviceName(snapshot);
		} else {
		cow_image_name = GetCowName(snapshot);
		}
		std::string cow_image_name = GetMappedCowDeviceName(snapshot, snapshot_status);

		std::string cow_image_device;
		if (!dm.GetDmDevicePathByName(cow_image_name, &cow_image_device)) {