Merge "COW partition creator uses DmSnapshotCowSizeCalculator" (ff60db1b) · Commits · e / os / android_system_core

fs_mgr/libsnapshot/partition_cow_creator.cpp

+45 −25

Original line number	Diff line number	Diff line
		@@ -17,8 +17,9 @@
		#include <math.h>

		#include <android-base/logging.h>

		#include <android/snapshot/snapshot.pb.h>

		#include "dm_snapshot_internals.h"
		#include "utility.h"

		using android::dm::kSectorSize;
		@@ -33,13 +34,6 @@ using RepeatedPtrField = google::protobuf::RepeatedPtrField<T>;
		namespace android {
		namespace snapshot {

		// Round \|d\| up to a multiple of \|block_size\|.
		static uint64_t RoundUp(double d, uint64_t block_size) {
		uint64_t ret = ((uint64_t)ceil(d) + block_size - 1) / block_size * block_size;
		CHECK(ret >= d) << "Can't round " << d << " up to a multiple of " << block_size;
		return ret;
		}

		// Intersect two linear extents. If no intersection, return an extent with length 0.
		static std::unique_ptr<Extent> Intersect(Extent* target_extent, Extent* existing_extent) {
		// Convert target_extent and existing_extent to linear extents. Zero extents
		@@ -68,33 +62,58 @@ bool PartitionCowCreator::HasExtent(Partition* p, Extent* e) {
		return false;
		}

		std::optional<uint64_t> PartitionCowCreator::GetCowSize(uint64_t snapshot_size) {
		// TODO: Use \|operations\|. to determine a minimum COW size.
		// kCowEstimateFactor is good for prototyping but we can't use that in production.
		static constexpr double kCowEstimateFactor = 1.05;
		auto cow_size = RoundUp(snapshot_size * kCowEstimateFactor, kDefaultBlockSize);
		return cow_size;
		uint64_t PartitionCowCreator::GetCowSize() {
		// WARNING: The origin partition should be READ-ONLY
		const uint64_t logical_block_size = current_metadata->logical_block_size();
		const unsigned int sectors_per_block = logical_block_size / kSectorSize;
		DmSnapCowSizeCalculator sc(kSectorSize, kSnapshotChunkSize);

		if (operations == nullptr) return sc.cow_size_bytes();

		for (const auto& iop : *operations) {
		for (const auto& de : iop.dst_extents()) {
		// Skip if no blocks are written
		if (de.num_blocks() == 0) continue;

		// Flag all the blocks that were written
		const auto block_boundary = de.start_block() + de.num_blocks();
		for (auto b = de.start_block(); b < block_boundary; ++b) {
		for (unsigned int s = 0; s < sectors_per_block; ++s) {
		const auto sector_id = b * sectors_per_block + s;
		sc.WriteSector(sector_id);
		}
		}
		}
		}

		return sc.cow_size_bytes();
		}

		std::optional<PartitionCowCreator::Return> PartitionCowCreator::Run() {
		CHECK(current_metadata->GetBlockDevicePartitionName(0) == LP_METADATA_DEFAULT_PARTITION_NAME &&
		target_metadata->GetBlockDevicePartitionName(0) == LP_METADATA_DEFAULT_PARTITION_NAME);

		uint64_t logical_block_size = current_metadata->logical_block_size();
		const uint64_t logical_block_size = current_metadata->logical_block_size();
		CHECK(logical_block_size != 0 && !(logical_block_size & (logical_block_size - 1)))
		<< "logical_block_size is not power of 2";

		Return ret;
		ret.snapshot_status.set_name(target_partition->name());
		ret.snapshot_status.set_device_size(target_partition->size());

		// TODO(b/141889746): Optimize by using a smaller snapshot. Some ranges in target_partition
		// may be written directly.
		ret.snapshot_status.set_snapshot_size(target_partition->size());

		auto cow_size = GetCowSize(ret.snapshot_status.snapshot_size());
		if (!cow_size.has_value()) return std::nullopt;

		// Being the COW partition virtual, its size doesn't affect the storage
		// memory that will be occupied by the target.
		// The actual storage space is affected by the COW file, whose size depends
		// on the chunks that diverged between \|current\| and \|target\|.
		// If the \|target\| partition is bigger than \|current\|, the data that is
		// modified outside of \|current\| can be written directly to \|current\|.
		// This because the data that will be written outside of \|current\| would
		// not invalidate any useful information of \|current\|, thus:
		// - if the snapshot is accepted for merge, this data would be already at
		// the right place and should not be copied;
		// - in the unfortunate case of the snapshot to be discarded, the regions
		// modified by this data can be set as free regions and reused.
		// Compute regions that are free in both current and target metadata. These are the regions
		// we can use for COW partition.
		auto target_free_regions = target_metadata->GetFreeRegions();
		@@ -102,13 +121,15 @@ std::optional<PartitionCowCreator::Return> PartitionCowCreator::Run() {
		auto free_regions = Interval::Intersect(target_free_regions, current_free_regions);
		uint64_t free_region_length = 0;
		for (const auto& interval : free_regions) {
		free_region_length += interval.length() * kSectorSize;
		free_region_length += interval.length();
		}
		free_region_length *= kSectorSize;

		LOG(INFO) << "Remaining free space for COW: " << free_region_length << " bytes";
		auto cow_size = GetCowSize();

		// Compute the COW partition size.
		uint64_t cow_partition_size = std::min(*cow_size, free_region_length);
		uint64_t cow_partition_size = std::min(cow_size, free_region_length);
		// Round it down to the nearest logical block. Logical partitions must be a multiple
		// of logical blocks.
		cow_partition_size &= ~(logical_block_size - 1);
		@@ -116,8 +137,7 @@ std::optional<PartitionCowCreator::Return> PartitionCowCreator::Run() {
		// Assign cow_partition_usable_regions to indicate what regions should the COW partition uses.
		ret.cow_partition_usable_regions = std::move(free_regions);

		// The rest of the COW space is allocated on ImageManager.
		uint64_t cow_file_size = (*cow_size) - ret.snapshot_status.cow_partition_size();
		auto cow_file_size = cow_size - cow_partition_size;
		// Round it up to the nearest sector.
		cow_file_size += kSectorSize - 1;
		cow_file_size &= ~(kSectorSize - 1);

fs_mgr/libsnapshot/partition_cow_creator.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -60,7 +60,7 @@ struct PartitionCowCreator {

		private:
		bool HasExtent(Partition* p, Extent* e);
		std::optional<uint64_t> GetCowSize(uint64_t snapshot_size);
		uint64_t GetCowSize();
		};

		} // namespace snapshot

fs_mgr/libsnapshot/partition_cow_creator_test.cpp

+86 −0

Original line number	Diff line number	Diff line
		@@ -14,12 +14,14 @@

		#include <gmock/gmock.h>
		#include <gtest/gtest.h>
		#include <libdm/dm.h>
		#include <liblp/builder.h>
		#include <liblp/property_fetcher.h>

		#include "dm_snapshot_internals.h"
		#include "partition_cow_creator.h"
		#include "test_helpers.h"
		#include "utility.h"

		using namespace android::fs_mgr;

		@@ -100,6 +102,90 @@ TEST_F(PartitionCowCreatorTest, Holes) {
		ASSERT_TRUE(ret.has_value());
		}

		TEST_F(PartitionCowCreatorTest, CowSize) {
		using InstallOperation = chromeos_update_engine::InstallOperation;
		using RepeatedInstallOperationPtr = google::protobuf::RepeatedPtrField<InstallOperation>;
		using Extent = chromeos_update_engine::Extent;

		constexpr uint64_t initial_size = 50_MiB;
		constexpr uint64_t final_size = 40_MiB;

		auto builder_a = MetadataBuilder::New(initial_size, 1_KiB, 2);
		ASSERT_NE(builder_a, nullptr);
		auto system_a = builder_a->AddPartition("system_a", LP_PARTITION_ATTR_READONLY);
		ASSERT_NE(system_a, nullptr);
		ASSERT_TRUE(builder_a->ResizePartition(system_a, final_size));

		auto builder_b = MetadataBuilder::New(initial_size, 1_KiB, 2);
		ASSERT_NE(builder_b, nullptr);
		auto system_b = builder_b->AddPartition("system_b", LP_PARTITION_ATTR_READONLY);
		ASSERT_NE(system_b, nullptr);
		ASSERT_TRUE(builder_b->ResizePartition(system_b, final_size));

		const uint64_t block_size = builder_b->logical_block_size();
		const uint64_t chunk_size = kSnapshotChunkSize * dm::kSectorSize;
		ASSERT_EQ(chunk_size, block_size);

		auto cow_device_size = [](const std::vector<InstallOperation>& iopv, MetadataBuilder* builder_a,
		MetadataBuilder* builder_b, Partition* system_b) {
		RepeatedInstallOperationPtr riop(iopv.begin(), iopv.end());
		PartitionCowCreator creator{.target_metadata = builder_b,
		.target_suffix = "_b",
		.target_partition = system_b,
		.current_metadata = builder_a,
		.current_suffix = "_a",
		.operations = &riop};

		auto ret = creator.Run();

		if (ret.has_value()) {
		return ret->snapshot_status.cow_file_size() + ret->snapshot_status.cow_partition_size();
		}
		return std::numeric_limits<uint64_t>::max();
		};

		std::vector<InstallOperation> iopv;
		InstallOperation iop;
		Extent* e;

		// No data written, no operations performed
		ASSERT_EQ(2 * chunk_size, cow_device_size(iopv, builder_a.get(), builder_b.get(), system_b));

		// No data written
		e = iop.add_dst_extents();
		e->set_start_block(0);
		e->set_num_blocks(0);
		iopv.push_back(iop);
		ASSERT_EQ(2 * chunk_size, cow_device_size(iopv, builder_a.get(), builder_b.get(), system_b));

		e = iop.add_dst_extents();
		e->set_start_block(1);
		e->set_num_blocks(0);
		iopv.push_back(iop);
		ASSERT_EQ(2 * chunk_size, cow_device_size(iopv, builder_a.get(), builder_b.get(), system_b));

		// Fill the first block
		e = iop.add_dst_extents();
		e->set_start_block(0);
		e->set_num_blocks(1);
		iopv.push_back(iop);
		ASSERT_EQ(3 * chunk_size, cow_device_size(iopv, builder_a.get(), builder_b.get(), system_b));

		// Fill the second block
		e = iop.add_dst_extents();
		e->set_start_block(1);
		e->set_num_blocks(1);
		iopv.push_back(iop);
		ASSERT_EQ(4 * chunk_size, cow_device_size(iopv, builder_a.get(), builder_b.get(), system_b));

		// Jump to 5th block and write 2
		e = iop.add_dst_extents();
		e->set_start_block(5);
		e->set_num_blocks(2);
		iopv.push_back(iop);
		ASSERT_EQ(6 * chunk_size, cow_device_size(iopv, builder_a.get(), builder_b.get(), system_b));
		}

		TEST(DmSnapshotInternals, CowSizeCalculator) {
		DmSnapCowSizeCalculator cc(512, 8);
		unsigned long int b;

fs_mgr/libsnapshot/snapshot_test.cpp

+18 −3

Original line number	Diff line number	Diff line
		@@ -784,9 +784,17 @@ TEST_F(SnapshotUpdateTest, FullUpdateFlow) {
		}

		// Grow all partitions.
		SetSize(sys_, 3788_KiB);
		SetSize(vnd_, 3788_KiB);
		SetSize(prd_, 3788_KiB);
		constexpr uint64_t partition_size = 3788_KiB;
		SetSize(sys_, partition_size);
		SetSize(vnd_, partition_size);
		SetSize(prd_, partition_size);

		// Create fake install operations to grow the COW device size.
		for (auto& partition : {sys_, vnd_, prd_}) {
		auto e = partition->add_operations()->add_dst_extents();
		e->set_start_block(0);
		e->set_num_blocks(GetSize(partition) / manifest_.block_size());
		}

		// Execute the update.
		ASSERT_TRUE(sm->BeginUpdate());
		@@ -949,6 +957,13 @@ TEST_F(SnapshotUpdateTest, TestRollback) {
		ASSERT_TRUE(sm->BeginUpdate());
		ASSERT_TRUE(sm->UnmapUpdateSnapshot("sys_b"));

		// Create fake install operations to grow the COW device size.
		for (auto& partition : {sys_, vnd_, prd_}) {
		auto e = partition->add_operations()->add_dst_extents();
		e->set_start_block(0);
		e->set_num_blocks(GetSize(partition) / manifest_.block_size());
		}

		ASSERT_TRUE(sm->CreateUpdateSnapshots(manifest_));

		// Write some data to target partitions.

fs_mgr/libsnapshot/test_helpers.cpp

+4 −0

Original line number	Diff line number	Diff line
		@@ -140,5 +140,9 @@ void SetSize(PartitionUpdate* partition_update, uint64_t size) {
		partition_update->mutable_new_partition_info()->set_size(size);
		}

		uint64_t GetSize(PartitionUpdate* partition_update) {
		return partition_update->mutable_new_partition_info()->size();
		}

		} // namespace snapshot
		} // namespace android