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Commit 2f11ec6a authored by David Anderson's avatar David Anderson
Browse files

libsnapshot: Prototype the new API for mapping writable snapshots. 

Since we can't provide a single device or fd anymore, we need to expose
a CowWriter directly. Additionally, we expose an API for reading
snapshots through the FileDescriptor abstraction.

Bug: 168554689
Test: builds
Change-Id: If7e8adbfe69c2a84d34c63d4b0adff2b3365fd82
parent 0407302a

fs_mgr/libsnapshot/Android.bp

+5 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ cc_defaults { 
    static_libs: [

        "libdm",

        "libfstab",

        "libsnapshot_cow",

        "update_metadata-protos",

    ],

    whole_static_libs: [
@@ -38,7 +39,9 @@ cc_defaults { 
        "libfstab",

    ],

    header_libs: [

        "libchrome",

        "libfiemap_headers",

        "libupdate_engine_headers",

    ],

    export_static_lib_headers: [

        "update_metadata-protos",
@@ -313,8 +316,10 @@ cc_defaults { 
        "libprotobuf-mutator",

    ],

    header_libs: [

        "libchrome",

        "libfiemap_headers",

        "libstorage_literals_headers",

        "libupdate_engine_headers",

    ],

    proto: {

        type: "full",

fs_mgr/libsnapshot/include/libsnapshot/mock_snapshot.h

+7 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#pragma once



#include <libsnapshot/snapshot.h>

#include <payload_consumer/file_descriptor.h>



#include <gmock/gmock.h>
@@ -37,6 +38,12 @@ class MockSnapshotManager : public ISnapshotManager { 
                (const android::fs_mgr::CreateLogicalPartitionParams& params,

                 std::string* snapshot_path),

                (override));

    MOCK_METHOD(std::unique_ptr<ICowWriter>, OpenSnapshotWriter,

                (const std::string& partition_name, std::chrono::milliseconds timeout_ms),

                (override));

    MOCK_METHOD(std::unique_ptr<FileDescriptor>, OpenSnapshotReader,

                (const std::string& partition_name, std::chrono::milliseconds timeout_ms),

                (override));

    MOCK_METHOD(bool, UnmapUpdateSnapshot, (const std::string& target_partition_name), (override));

    MOCK_METHOD(bool, NeedSnapshotsInFirstStageMount, (), (override));

    MOCK_METHOD(bool, CreateLogicalAndSnapshotPartitions,

fs_mgr/libsnapshot/include/libsnapshot/snapshot.h

+26 −1
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ 
#include <update_engine/update_metadata.pb.h>



#include <libsnapshot/auto_device.h>

#include <libsnapshot/cow_writer.h>

#include <libsnapshot/return.h>



#ifndef FRIEND_TEST
@@ -43,6 +44,10 @@ 
#define DEFINED_FRIEND_TEST

#endif



namespace chromeos_update_engine {

class FileDescriptor;

}  // namespace chromeos_update_engine



namespace android {



namespace fiemap {
@@ -105,6 +110,8 @@ class ISnapshotManager { 
    };

    virtual ~ISnapshotManager() = default;



    using FileDescriptor = chromeos_update_engine::FileDescriptor;



    // Begin an update. This must be called before creating any snapshots. It

    // will fail if GetUpdateState() != None.

    virtual bool BeginUpdate() = 0;
@@ -173,11 +180,25 @@ class ISnapshotManager { 


    // Map a snapshotted partition for OTA clients to write to. Write-protected regions are

    // determined previously in CreateSnapshots.

    //

    // |snapshot_path| must not be nullptr.

    //

    // This method will return false if ro.virtual_ab.compression.enabled is true.

    virtual bool MapUpdateSnapshot(const android::fs_mgr::CreateLogicalPartitionParams& params,

                                   std::string* snapshot_path) = 0;



    // Unmap a snapshot device that's previously mapped with MapUpdateSnapshot.

    // Create an ICowWriter to build a snapshot against a target partition.

    virtual std::unique_ptr<ICowWriter> OpenSnapshotWriter(

            const std::string& partition_name, std::chrono::milliseconds timeout_ms = {}) = 0;



    // Open a snapshot for reading. A file-like interface is provided through the FileDescriptor.

    // In this mode, writes are not supported.

    virtual std::unique_ptr<FileDescriptor> OpenSnapshotReader(

            const std::string& partition_name, std::chrono::milliseconds timeout_ms = {}) = 0;



    // Unmap a snapshot device or CowWriter that was previously opened with MapUpdateSnapshot,

    // OpenSnapshotWriter, or OpenSnapshotReader. All outstanding open descriptors, writers,

    // or readers must be deleted before this is called.

    virtual bool UnmapUpdateSnapshot(const std::string& target_partition_name) = 0;



    // If this returns true, first-stage mount must call
@@ -288,6 +309,10 @@ class SnapshotManager final : public ISnapshotManager { 
    Return CreateUpdateSnapshots(const DeltaArchiveManifest& manifest) override;

    bool MapUpdateSnapshot(const CreateLogicalPartitionParams& params,

                           std::string* snapshot_path) override;

    std::unique_ptr<ICowWriter> OpenSnapshotWriter(

            const std::string& partition_name, std::chrono::milliseconds timeout_ms = {}) override;

    std::unique_ptr<FileDescriptor> OpenSnapshotReader(

            const std::string& partition_name, std::chrono::milliseconds timeout_ms = {}) override;

    bool UnmapUpdateSnapshot(const std::string& target_partition_name) override;

    bool NeedSnapshotsInFirstStageMount() override;

    bool CreateLogicalAndSnapshotPartitions(

fs_mgr/libsnapshot/include/libsnapshot/snapshot_stub.h

+5 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#pragma once



#include <libsnapshot/snapshot.h>

#include <payload_consumer/file_descriptor.h>



namespace android::snapshot {
@@ -35,6 +36,10 @@ class SnapshotManagerStub : public ISnapshotManager { 
            const chromeos_update_engine::DeltaArchiveManifest& manifest) override;

    bool MapUpdateSnapshot(const android::fs_mgr::CreateLogicalPartitionParams& params,

                           std::string* snapshot_path) override;

    std::unique_ptr<ICowWriter> OpenSnapshotWriter(const std::string& partition_name,

                                                   std::chrono::milliseconds timeout_ms) override;

    std::unique_ptr<FileDescriptor> OpenSnapshotReader(

            const std::string& partition_name, std::chrono::milliseconds timeout_ms = {}) override;

    bool UnmapUpdateSnapshot(const std::string& target_partition_name) override;

    bool NeedSnapshotsInFirstStageMount() override;

    bool CreateLogicalAndSnapshotPartitions(

fs_mgr/libsnapshot/snapshot.cpp

+34 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ 
#include <android-base/file.h>

#include <android-base/logging.h>

#include <android-base/parseint.h>

#include <android-base/properties.h>

#include <android-base/strings.h>

#include <android-base/unique_fd.h>

#include <ext4_utils/ext4_utils.h>
@@ -68,6 +69,7 @@ using android::fs_mgr::SlotNumberForSlotSuffix; 
using android::hardware::boot::V1_1::MergeStatus;

using chromeos_update_engine::DeltaArchiveManifest;

using chromeos_update_engine::Extent;

using chromeos_update_engine::FileDescriptor;

using chromeos_update_engine::InstallOperation;

template <typename T>

using RepeatedPtrField = google::protobuf::RepeatedPtrField<T>;
@@ -103,6 +105,10 @@ SnapshotManager::SnapshotManager(IDeviceInfo* device) : device_(device) { 
    metadata_dir_ = device_->GetMetadataDir();

}



static inline bool IsCompressionEnabled() {

    return android::base::GetBoolProperty("ro.virtual_ab.compression.enabled", false);

}



static std::string GetCowName(const std::string& snapshot_name) {

    return snapshot_name + "-cow";

}
@@ -2420,6 +2426,11 @@ Return SnapshotManager::InitializeUpdateSnapshots( 


bool SnapshotManager::MapUpdateSnapshot(const CreateLogicalPartitionParams& params,

                                        std::string* snapshot_path) {

    if (IsCompressionEnabled()) {

        LOG(ERROR) << "MapUpdateSnapshot cannot be used in compression mode.";

        return false;

    }



    auto lock = LockShared();

    if (!lock) return false;

    if (!UnmapPartitionWithSnapshot(lock.get(), params.GetPartitionName())) {
@@ -2430,6 +2441,29 @@ bool SnapshotManager::MapUpdateSnapshot(const CreateLogicalPartitionParams& para 
    return MapPartitionWithSnapshot(lock.get(), params, snapshot_path);

}



std::unique_ptr<ICowWriter> SnapshotManager::OpenSnapshotWriter(

        const std::string& partition_name, std::chrono::milliseconds timeout_ms) {

    if (!IsCompressionEnabled()) {

        LOG(ERROR) << "OpenSnapshotWriter can only be called in compression mode.";

        return nullptr;

    }



    (void)partition_name;

    (void)timeout_ms;



    // Not yet implemented.

    return nullptr;

}



std::unique_ptr<FileDescriptor> SnapshotManager::OpenSnapshotReader(

        const std::string& partition_name, std::chrono::milliseconds timeout_ms) {

    (void)partition_name;

    (void)timeout_ms;



    // Not yet implemented.

    return nullptr;

}



bool SnapshotManager::UnmapUpdateSnapshot(const std::string& target_partition_name) {

    auto lock = LockShared();

    if (!lock) return false;