Merge "libsnapshot: Move snapshot metadata to super partition." into main
diff --git a/fastboot/Android.bp b/fastboot/Android.bp
index 774af28..bfe0768 100644
--- a/fastboot/Android.bp
+++ b/fastboot/Android.bp
@@ -186,6 +186,7 @@
         "libprotobuf-cpp-lite",
         "libsparse",
         "libutils",
+        "libselinux",
     ],
 
     static_libs: [
diff --git a/fs_mgr/fs_mgr_priv.h b/fs_mgr/fs_mgr_priv.h
index 7e4d5e5..84e4924 100644
--- a/fs_mgr/fs_mgr_priv.h
+++ b/fs_mgr/fs_mgr_priv.h
@@ -80,10 +80,8 @@
 
 using namespace std::chrono_literals;
 
-bool fs_mgr_set_blk_ro(const std::string& blockdev, bool readonly = true);
 bool fs_mgr_is_device_unlocked();
 
-bool fs_mgr_is_ext4(const std::string& blk_device);
 bool fs_mgr_is_f2fs(const std::string& blk_device);
 
 bool fs_mgr_filesystem_available(const std::string& filesystem);
diff --git a/fs_mgr/include/fs_mgr.h b/fs_mgr/include/fs_mgr.h
index af5ae2d..9cfa93f 100644
--- a/fs_mgr/include/fs_mgr.h
+++ b/fs_mgr/include/fs_mgr.h
@@ -104,6 +104,12 @@
 // returned. Otherwise, it will use the current slot.
 std::string fs_mgr_get_super_partition_name(int slot = -1);
 
+// Set readonly for the block device
+bool fs_mgr_set_blk_ro(const std::string& blockdev, bool readonly = true);
+
+// Check if the block device has ext4 filesystem
+bool fs_mgr_is_ext4(const std::string& blk_device);
+
 enum FsMgrUmountStatus : int {
     SUCCESS = 0,
     ERROR_UNKNOWN = 1 << 0,
diff --git a/fs_mgr/libsnapshot/Android.bp b/fs_mgr/libsnapshot/Android.bp
index f297125..4828c4c 100644
--- a/fs_mgr/libsnapshot/Android.bp
+++ b/fs_mgr/libsnapshot/Android.bp
@@ -46,6 +46,7 @@
         "libfstab",
         "libsnapuserd_client",
         "libz",
+        "libselinux",
     ],
     header_libs: [
         "libfiemap_headers",
@@ -91,6 +92,7 @@
         "partition_cow_creator.cpp",
         "return.cpp",
         "utility.cpp",
+        "scratch_super.cpp",
     ],
 }
 
@@ -351,6 +353,7 @@
     ],
     srcs: [
         "snapshotctl.cpp",
+        "scratch_super.cpp",
     ],
     static_libs: [
         "libbrotli",
diff --git a/fs_mgr/libsnapshot/device_info.cpp b/fs_mgr/libsnapshot/device_info.cpp
index e0969f4..19f3e02 100644
--- a/fs_mgr/libsnapshot/device_info.cpp
+++ b/fs_mgr/libsnapshot/device_info.cpp
@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "device_info.h"
+#include "scratch_super.h"
 
 #include <android-base/logging.h>
 #include <fs_mgr.h>
@@ -37,8 +38,24 @@
 constexpr bool kIsRecovery = false;
 #endif
 
+DeviceInfo::DeviceInfo() {
+    std::string scratch_device = android::snapshot::GetScratchOtaMetadataPartition();
+    if (!scratch_device.empty()) {
+        std::string scratch_metadata =
+                android::snapshot::MapScratchOtaMetadataPartition(scratch_device);
+        if (!scratch_metadata.empty()) {
+            SetMetadataDir(scratch_metadata);
+            SetTempMetadata();
+        }
+    }
+}
+
 std::string DeviceInfo::GetMetadataDir() const {
-    return "/metadata/ota"s;
+    return metadata_dir_;
+}
+
+void DeviceInfo::SetMetadataDir(const std::string& value) {
+    metadata_dir_ = value;
 }
 
 std::string DeviceInfo::GetSlotSuffix() const {
diff --git a/fs_mgr/libsnapshot/device_info.h b/fs_mgr/libsnapshot/device_info.h
index 9153abb..e93ec49 100644
--- a/fs_mgr/libsnapshot/device_info.h
+++ b/fs_mgr/libsnapshot/device_info.h
@@ -29,6 +29,7 @@
     using MergeStatus = ::aidl::android::hardware::boot::MergeStatus;
 
   public:
+    DeviceInfo();
     std::string GetMetadataDir() const override;
     std::string GetSlotSuffix() const override;
     std::string GetOtherSlotSuffix() const override;
@@ -42,14 +43,19 @@
     std::unique_ptr<IImageManager> OpenImageManager() const override;
     bool IsFirstStageInit() const override;
     android::dm::IDeviceMapper& GetDeviceMapper() override;
-
+    void SetMetadataDir(const std::string& value);
     void set_first_stage_init(bool value) { first_stage_init_ = value; }
+    bool IsTempMetadata() const override { return temp_metadata_; }
+    void SetTempMetadata() { temp_metadata_ = true; }
 
   private:
     bool EnsureBootHal();
 
     android::fs_mgr::PartitionOpener opener_;
     bool first_stage_init_ = false;
+    // Default value
+    std::string metadata_dir_ = "/metadata/ota";
+    bool temp_metadata_ = false;
 #ifdef LIBSNAPSHOT_USE_HAL
     std::unique_ptr<::android::hal::BootControlClient> boot_control_;
 #endif
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
index deb2d6e..7ae55db 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
@@ -111,6 +111,7 @@
         virtual bool IsFirstStageInit() const = 0;
         virtual std::unique_ptr<IImageManager> OpenImageManager() const = 0;
         virtual android::dm::IDeviceMapper& GetDeviceMapper() = 0;
+        virtual bool IsTempMetadata() const = 0;
 
         // Helper method for implementing OpenImageManager.
         std::unique_ptr<IImageManager> OpenImageManager(const std::string& gsid_dir) const;
@@ -329,6 +330,10 @@
     // might be needed to perform first-stage mounts.
     static bool IsSnapshotManagerNeeded();
 
+    // Map the temp OTA metadata partition from super
+    static bool MapTempOtaMetadataPartitionIfNeeded(
+            const std::function<bool(const std::string&)>& init);
+
     // Helper function for second stage init to restorecon on the rollback indicator.
     static std::string GetGlobalRollbackIndicatorPath();
 
diff --git a/fs_mgr/libsnapshot/include_test/libsnapshot/test_helpers.h b/fs_mgr/libsnapshot/include_test/libsnapshot/test_helpers.h
index 620b03c..1cd6651 100644
--- a/fs_mgr/libsnapshot/include_test/libsnapshot/test_helpers.h
+++ b/fs_mgr/libsnapshot/include_test/libsnapshot/test_helpers.h
@@ -79,7 +79,7 @@
         : TestDeviceInfo(fake_super) {
         set_slot_suffix(slot_suffix);
     }
-    std::string GetMetadataDir() const override { return "/metadata/ota/test"s; }
+    std::string GetMetadataDir() const override { return metadata_dir_; }
     std::string GetSlotSuffix() const override { return slot_suffix_; }
     std::string GetOtherSlotSuffix() const override { return slot_suffix_ == "_a" ? "_b" : "_a"; }
     std::string GetSuperDevice([[maybe_unused]] uint32_t slot) const override { return "super"; }
@@ -120,6 +120,7 @@
     void set_dm(android::dm::IDeviceMapper* dm) { dm_ = dm; }
 
     MergeStatus merge_status() const { return merge_status_; }
+    bool IsTempMetadata() const override { return temp_metadata_; }
 
   private:
     std::string slot_suffix_ = "_a";
@@ -129,6 +130,8 @@
     bool first_stage_init_ = false;
     std::unordered_set<uint32_t> unbootable_slots_;
     android::dm::IDeviceMapper* dm_ = nullptr;
+    std::string metadata_dir_ = "/metadata/ota/test";
+    bool temp_metadata_ = false;
 };
 
 class DeviceMapperWrapper : public android::dm::IDeviceMapper {
diff --git a/fs_mgr/libsnapshot/scratch_super.cpp b/fs_mgr/libsnapshot/scratch_super.cpp
new file mode 100644
index 0000000..805abf3
--- /dev/null
+++ b/fs_mgr/libsnapshot/scratch_super.cpp
@@ -0,0 +1,417 @@
+// Copyright (C) 2024 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/fs.h>
+#include <selinux/selinux.h>
+#include <stdlib.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <sys/types.h>
+#include <sys/vfs.h>
+#include <unistd.h>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/macros.h>
+#include <android-base/properties.h>
+#include <android-base/scopeguard.h>
+#include <android-base/strings.h>
+#include <android-base/unique_fd.h>
+#include <ext4_utils/ext4_utils.h>
+
+#include <libsnapshot/snapshot.h>
+
+#include <fs_mgr.h>
+#include <fs_mgr_dm_linear.h>
+#include <fstab/fstab.h>
+#include <liblp/builder.h>
+#include <storage_literals/storage_literals.h>
+#include <algorithm>
+#include <filesystem>
+#include <memory>
+#include <optional>
+#include <string>
+#include <vector>
+
+#include "device_info.h"
+#include "scratch_super.h"
+
+using namespace std::literals;
+using namespace android::dm;
+using namespace android::fs_mgr;
+using namespace android::storage_literals;
+
+namespace android {
+namespace snapshot {
+
+static bool UmountScratch() {
+    auto ota_dir = std::string(kOtaMetadataMount) + "/" + "ota";
+    std::error_code ec;
+
+    if (std::filesystem::remove_all(ota_dir, ec) == static_cast<std::uintmax_t>(-1)) {
+        LOG(ERROR) << "Failed to remove OTA directory: " << ec.message();
+        return false;
+    }
+
+    if (umount(kOtaMetadataMount) != 0) {
+        PLOG(ERROR) << "UmountScratch failed";
+        return false;
+    }
+
+    LOG(INFO) << "umount scratch_super success";
+    return true;
+}
+
+bool CleanupScratchOtaMetadataIfPresent(const ISnapshotManager::IDeviceInfo* info) {
+    if (!UmountScratch()) {
+        return false;
+    }
+
+    std::unique_ptr<MetadataBuilder> builder;
+    const auto partition_name = android::base::Basename(kOtaMetadataMount);
+    const std::vector<int> slots = {0, 1};
+
+    if (info == nullptr) {
+        info = new android::snapshot::DeviceInfo();
+    }
+
+    std::string super_device;
+    if (info->IsTestDevice()) {
+        super_device = "super";
+    } else {
+        super_device = kPhysicalDevice + fs_mgr_get_super_partition_name();
+    }
+    const auto& opener = info->GetPartitionOpener();
+    std::string slot_suffix = info->GetSlotSuffix();
+    int slot = SlotNumberForSlotSuffix(slot_suffix);
+    // Walk both the slots and clean up metadata related to scratch space from
+    // both the slots.
+    for (auto slot : slots) {
+        std::unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(opener, super_device, slot);
+        if (!builder) {
+            return false;
+        }
+
+        if (builder->FindPartition(partition_name) != nullptr) {
+            builder->RemovePartition(partition_name);
+            auto metadata = builder->Export();
+            if (!metadata) {
+                return false;
+            }
+            if (!UpdatePartitionTable(info->GetPartitionOpener(), super_device, *metadata.get(),
+                                      slot)) {
+                LOG(ERROR) << "UpdatePartitionTable failed for slot: " << slot;
+                return false;
+            }
+            if (DestroyLogicalPartition(partition_name)) {
+                LOG(INFO) << "CleanupScratchOtaMetadata success for slot: " << slot;
+            }
+        }
+    }
+
+    return true;
+}
+
+static bool SetupOTADirs() {
+    if (setfscreatecon(android::snapshot::kOtaMetadataFileContext)) {
+        PLOG(ERROR) << "setfscreatecon failed: " << android::snapshot::kOtaMetadataFileContext;
+        return false;
+    }
+    const auto ota_dir = std::string(kOtaMetadataMount) + "/" + "ota";
+    if (mkdir(ota_dir.c_str(), 0755) != 0 && errno != EEXIST) {
+        PLOG(ERROR) << "mkdir " << ota_dir;
+        return false;
+    }
+
+    const auto snapshot_dir = ota_dir + "/" + "snapshots";
+    if (mkdir(snapshot_dir.c_str(), 0755) != 0 && errno != EEXIST) {
+        PLOG(ERROR) << "mkdir " << snapshot_dir;
+        return false;
+    }
+    if (setfscreatecon(nullptr)) {
+        PLOG(ERROR) << "setfscreatecon null";
+        return false;
+    }
+    return true;
+}
+
+static bool MountScratch(const std::string& device_path) {
+    if (access(device_path.c_str(), R_OK | W_OK)) {
+        LOG(ERROR) << "Path does not exist or is not readwrite: " << device_path;
+        return false;
+    }
+
+    std::string filesystem_candidate;
+    if (fs_mgr_is_ext4(device_path)) {
+        filesystem_candidate = "ext4";
+    } else {
+        LOG(ERROR) << "Scratch partition is not ext4";
+        return false;
+    }
+    if (setfscreatecon(android::snapshot::kOtaMetadataFileContext)) {
+        PLOG(ERROR) << "setfscreatecon failed: " << android::snapshot::kOtaMetadataFileContext;
+        return false;
+    }
+    if (mkdir(kOtaMetadataMount, 0755) && (errno != EEXIST)) {
+        PLOG(ERROR) << "create " << kOtaMetadataMount;
+        return false;
+    }
+
+    android::fs_mgr::FstabEntry entry;
+    entry.blk_device = device_path;
+    entry.mount_point = kOtaMetadataMount;
+    entry.flags = MS_NOATIME;
+    entry.flags |= MS_SYNCHRONOUS;
+    entry.fs_options = "nodiscard";
+    fs_mgr_set_blk_ro(device_path, false);
+    entry.fs_mgr_flags.check = true;
+
+    bool mounted = false;
+    entry.fs_type = filesystem_candidate.c_str();
+    if (fs_mgr_do_mount_one(entry) == 0) {
+        mounted = true;
+    }
+
+    if (setfscreatecon(nullptr)) {
+        PLOG(ERROR) << "setfscreatecon null";
+        return false;
+    }
+    if (!mounted) {
+        rmdir(kOtaMetadataMount);
+        return false;
+    }
+
+    return true;
+}
+
+static bool MakeScratchFilesystem(const std::string& scratch_device) {
+    std::string fs_type;
+    std::string command;
+    if (!access(kMkExt4, X_OK)) {
+        fs_type = "ext4";
+        command = kMkExt4 + " -F -b 4096 -t ext4 -m 0 -O has_journal -M "s + kOtaMetadataMount;
+    } else {
+        LOG(ERROR) << "No supported mkfs command or filesystem driver available, supported "
+                      "filesystems "
+                      "are: f2fs, ext4";
+        return false;
+    }
+    command += " " + scratch_device + " >/dev/null 2>/dev/null </dev/null";
+    fs_mgr_set_blk_ro(scratch_device, false);
+    auto ret = system(command.c_str());
+    if (ret) {
+        LOG(ERROR) << "make " << fs_type << " filesystem on " << scratch_device
+                   << " return=" << ret;
+        return false;
+    }
+    return true;
+}
+
+static bool CreateDynamicScratch(const ISnapshotManager::IDeviceInfo* info,
+                                 std::string* scratch_device) {
+    const auto partition_name = android::base::Basename(kOtaMetadataMount);
+    auto& dm = DeviceMapper::Instance();
+    if (info == nullptr) {
+        info = new android::snapshot::DeviceInfo();
+    }
+
+    std::string super_device;
+    if (info->IsTestDevice()) {
+        super_device = "super";
+    } else {
+        super_device = kPhysicalDevice + fs_mgr_get_super_partition_name();
+    }
+
+    bool partition_exists = dm.GetState(partition_name) != DmDeviceState::INVALID;
+    if (partition_exists) {
+        LOG(ERROR) << "Partition already exists: " << partition_name;
+        return false;
+    }
+
+    const auto& opener = info->GetPartitionOpener();
+    std::string slot_suffix = info->GetSlotSuffix();
+    int slot = SlotNumberForSlotSuffix(slot_suffix);
+    std::unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(opener, super_device, slot);
+
+    if (!builder) {
+        LOG(ERROR) << "open " << super_device << " failed";
+        return false;
+    }
+
+    auto partition = builder->FindPartition(partition_name);
+    partition_exists = partition != nullptr;
+    if (partition_exists) {
+        LOG(ERROR) << "Partition exists in super metadata";
+        return false;
+    }
+
+    partition = builder->AddPartition(partition_name, LP_PARTITION_ATTR_NONE);
+    if (!partition) {
+        LOG(ERROR) << "AddPartition failed " << partition_name;
+        return false;
+    }
+
+    auto free_space = builder->AllocatableSpace() - builder->UsedSpace();
+    if (free_space < kOtaMetadataPartitionSize) {
+        LOG(ERROR) << "No space in super partition. Free space: " << free_space
+                   << " Requested space: " << kOtaMetadataPartitionSize;
+        return false;
+    }
+
+    LOG(INFO) << "CreateDynamicScratch: free_space: " << free_space
+              << " scratch_size: " << kOtaMetadataPartitionSize << " slot_number: " << slot;
+
+    if (!builder->ResizePartition(partition, kOtaMetadataPartitionSize)) {
+        LOG(ERROR) << "ResizePartition failed: " << partition_name << " free_space: " << free_space
+                   << " scratch_size: " << kOtaMetadataPartitionSize;
+        return false;
+    }
+
+    auto metadata = builder->Export();
+    CreateLogicalPartitionParams params;
+
+    if (!metadata ||
+        !UpdatePartitionTable(info->GetPartitionOpener(), super_device, *metadata.get(), slot)) {
+        LOG(ERROR) << "UpdatePartitionTable failed: " << partition_name;
+        return false;
+    }
+    params = {
+            .block_device = super_device,
+            .metadata_slot = slot,
+            .partition_name = partition_name,
+            .force_writable = true,
+            .timeout_ms = 10s,
+            .partition_opener = &info->GetPartitionOpener(),
+    };
+
+    if (!CreateLogicalPartition(params, scratch_device)) {
+        LOG(ERROR) << "CreateLogicalPartition failed";
+        return false;
+    }
+
+    LOG(INFO) << "Scratch device created successfully: " << *scratch_device << " slot: " << slot;
+    return true;
+}
+
+bool IsScratchOtaMetadataOnSuper() {
+    auto partition_name = android::base::Basename(kOtaMetadataMount);
+    auto source_slot = fs_mgr_get_slot_suffix();
+    auto source_slot_number = SlotNumberForSlotSuffix(source_slot);
+
+    const auto super_device =
+            kPhysicalDevice + fs_mgr_get_super_partition_name(!source_slot_number);
+
+    auto metadata = android::fs_mgr::ReadMetadata(super_device, !source_slot_number);
+    if (!metadata) {
+        return false;
+    }
+    auto partition = android::fs_mgr::FindPartition(*metadata.get(), partition_name);
+    if (!partition) {
+        return false;
+    }
+
+    auto& dm = DeviceMapper::Instance();
+    if (dm.GetState(partition_name) == DmDeviceState::ACTIVE) {
+        LOG(INFO) << "Partition: " << partition_name << " is active";
+        return true;
+    }
+
+    CreateLogicalPartitionParams params = {
+            .block_device = super_device,
+            .metadata = metadata.get(),
+            .partition = partition,
+    };
+
+    std::string scratch_path;
+    if (!CreateLogicalPartition(params, &scratch_path)) {
+        LOG(ERROR) << "Could not create logical partition: " << partition_name;
+        return false;
+    }
+    LOG(INFO) << "Scratch device: " << scratch_path << " created successfully";
+
+    return true;
+}
+
+std::string GetScratchOtaMetadataPartition() {
+    std::string device;
+    auto& dm = DeviceMapper::Instance();
+    auto partition_name = android::base::Basename(kOtaMetadataMount);
+
+    bool invalid_partition = (dm.GetState(partition_name) == DmDeviceState::INVALID);
+    if (!invalid_partition && dm.GetDmDevicePathByName(partition_name, &device)) {
+        return device;
+    }
+    return "";
+}
+
+static bool ScratchAlreadyMounted(const std::string& mount_point) {
+    android::fs_mgr::Fstab fstab;
+    if (!ReadFstabFromProcMounts(&fstab)) {
+        return false;
+    }
+    for (const auto& entry : GetEntriesForMountPoint(&fstab, mount_point)) {
+        if (entry->fs_type == "ext4") {
+            return true;
+        }
+    }
+    return false;
+}
+
+std::string MapScratchOtaMetadataPartition(const std::string& scratch_device) {
+    if (!ScratchAlreadyMounted(kOtaMetadataMount)) {
+        if (!MountScratch(scratch_device)) {
+            return "";
+        }
+    }
+
+    auto ota_dir = std::string(kOtaMetadataMount) + "/" + "ota";
+    if (access(ota_dir.c_str(), F_OK) != 0) {
+        return "";
+    }
+    return ota_dir;
+}
+
+// Entry point to create a scratch device on super partition
+// This will create a 1MB space in super. The space will be
+// from the current active slot. Ext4 filesystem will be created
+// on this scratch device and all the OTA related directories
+// will be created.
+bool CreateScratchOtaMetadataOnSuper(const ISnapshotManager::IDeviceInfo* info) {
+    std::string scratch_device;
+
+    if (!CreateDynamicScratch(info, &scratch_device)) {
+        LOG(ERROR) << "CreateDynamicScratch failed";
+        return false;
+    }
+    if (!MakeScratchFilesystem(scratch_device)) {
+        LOG(ERROR) << "MakeScratchFilesystem failed";
+        return false;
+    }
+    if (!MountScratch(scratch_device)) {
+        LOG(ERROR) << "MountScratch failed";
+        return false;
+    }
+    if (!SetupOTADirs()) {
+        LOG(ERROR) << "SetupOTADirs failed";
+        return false;
+    }
+    return true;
+}
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/scratch_super.h b/fs_mgr/libsnapshot/scratch_super.h
new file mode 100644
index 0000000..3e6fe70
--- /dev/null
+++ b/fs_mgr/libsnapshot/scratch_super.h
@@ -0,0 +1,33 @@
+// Copyright (C) 2024 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+namespace android {
+namespace snapshot {
+
+constexpr char kMkExt4[] = "/system/bin/mke2fs";
+constexpr char kOtaMetadataFileContext[] = "u:object_r:ota_metadata_file:s0";
+constexpr char kOtaMetadataMount[] = "/mnt/scratch_ota_metadata_super";
+const size_t kOtaMetadataPartitionSize = uint64_t(1 * 1024 * 1024);
+constexpr char kPhysicalDevice[] = "/dev/block/by-name/";
+
+bool IsScratchOtaMetadataOnSuper();
+std::string GetScratchOtaMetadataPartition();
+std::string MapScratchOtaMetadataPartition(const std::string& device);
+bool CreateScratchOtaMetadataOnSuper(const ISnapshotManager::IDeviceInfo* info = nullptr);
+bool CleanupScratchOtaMetadataIfPresent(const ISnapshotManager::IDeviceInfo* info = nullptr);
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index 108fd90..6c3bedd 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -48,6 +48,7 @@
 #include <libsnapshot/snapshot_stats.h>
 #include "device_info.h"
 #include "partition_cow_creator.h"
+#include "scratch_super.h"
 #include "snapshot_metadata_updater.h"
 #include "utility.h"
 
@@ -117,7 +118,11 @@
         info = new DeviceInfo();
     }
 
-    return std::unique_ptr<SnapshotManager>(new SnapshotManager(info));
+    auto sm = std::unique_ptr<SnapshotManager>(new SnapshotManager(info));
+    if (info->IsTempMetadata()) {
+        LOG(INFO) << "Using temp metadata from super";
+    }
+    return sm;
 }
 
 std::unique_ptr<SnapshotManager> SnapshotManager::NewForFirstStageMount(IDeviceInfo* info) {
@@ -1110,6 +1115,13 @@
         if (result.state == UpdateState::MergeFailed) {
             AcknowledgeMergeFailure(result.failure_code);
         }
+
+        if (result.state == UpdateState::MergeCompleted) {
+            if (device_->IsTempMetadata()) {
+                CleanupScratchOtaMetadataIfPresent();
+            }
+        }
+
         if (result.state != UpdateState::Merging) {
             // Either there is no merge, or the merge was finished, so no need
             // to keep waiting.
@@ -2310,7 +2322,27 @@
 }
 
 bool SnapshotManager::IsSnapshotManagerNeeded() {
-    return access(kBootIndicatorPath, F_OK) == 0;
+    if (access(kBootIndicatorPath, F_OK) == 0) {
+        return true;
+    }
+
+    if (IsScratchOtaMetadataOnSuper()) {
+        return true;
+    }
+
+    return false;
+}
+
+bool SnapshotManager::MapTempOtaMetadataPartitionIfNeeded(
+        const std::function<bool(const std::string&)>& init) {
+    auto device = android::snapshot::GetScratchOtaMetadataPartition();
+    if (!device.empty()) {
+        init(device);
+        if (android::snapshot::MapScratchOtaMetadataPartition(device).empty()) {
+            return false;
+        }
+    }
+    return true;
 }
 
 std::string SnapshotManager::GetGlobalRollbackIndicatorPath() {
@@ -2397,6 +2429,12 @@
             continue;
         }
 
+        if (GetPartitionName(partition) ==
+            android::base::Basename(android::snapshot::kOtaMetadataMount)) {
+            LOG(INFO) << "Partition: " << GetPartitionName(partition) << " skipping";
+            continue;
+        }
+
         CreateLogicalPartitionParams params = {
                 .block_device = super_device,
                 .metadata = metadata.get(),
diff --git a/fs_mgr/libsnapshot/snapshot_test.cpp b/fs_mgr/libsnapshot/snapshot_test.cpp
index 16c247f..46c3a35 100644
--- a/fs_mgr/libsnapshot/snapshot_test.cpp
+++ b/fs_mgr/libsnapshot/snapshot_test.cpp
@@ -47,6 +47,7 @@
 #include <android/snapshot/snapshot.pb.h>
 #include <libsnapshot/test_helpers.h>
 #include "partition_cow_creator.h"
+#include "scratch_super.h"
 #include "utility.h"
 
 // Mock classes are not used. Header included to ensure mocked class definition aligns with the
@@ -1342,6 +1343,15 @@
     DynamicPartitionGroup* group_ = nullptr;
 };
 
+TEST_F(SnapshotUpdateTest, SuperOtaMetadataTest) {
+    auto info = new TestDeviceInfo(fake_super);
+    ASSERT_TRUE(CreateScratchOtaMetadataOnSuper(info));
+    std::string scratch_device = GetScratchOtaMetadataPartition();
+    ASSERT_NE(scratch_device, "");
+    ASSERT_NE(MapScratchOtaMetadataPartition(scratch_device), "");
+    ASSERT_TRUE(CleanupScratchOtaMetadataIfPresent(info));
+}
+
 // Test full update flow executed by update_engine. Some partitions uses super empty space,
 // some uses images, and some uses both.
 // Also test UnmapUpdateSnapshot unmaps everything.
diff --git a/fs_mgr/libsnapshot/snapshotctl.cpp b/fs_mgr/libsnapshot/snapshotctl.cpp
index 0158d4d..23c3ccf 100644
--- a/fs_mgr/libsnapshot/snapshotctl.cpp
+++ b/fs_mgr/libsnapshot/snapshotctl.cpp
@@ -16,7 +16,6 @@
 
 #include <sysexits.h>
 #include <unistd.h>
-
 #include <chrono>
 #include <filesystem>
 #include <fstream>
@@ -46,6 +45,7 @@
 #include <storage_literals/storage_literals.h>
 
 #include "partition_cow_creator.h"
+#include "scratch_super.h"
 
 #ifdef SNAPSHOTCTL_USERDEBUG_OR_ENG
 #include <BootControlClient.h>
@@ -57,6 +57,8 @@
 using android::base::LogdLogger;
 using android::base::StderrLogger;
 using android::base::TeeLogger;
+using namespace android::dm;
+using namespace android::fs_mgr;
 using android::fs_mgr::CreateLogicalPartitionParams;
 using android::fs_mgr::FindPartition;
 using android::fs_mgr::GetPartitionSize;
@@ -97,7 +99,7 @@
 #ifdef SNAPSHOTCTL_USERDEBUG_OR_ENG
 class MapSnapshots {
   public:
-    MapSnapshots(std::string path = "");
+    MapSnapshots(std::string path = "", bool metadata_super = false);
     bool CreateSnapshotDevice(std::string& partition_name, std::string& patch);
     bool InitiateThreadedSnapshotWrite(std::string& pname, std::string& snapshot_patch);
     bool FinishSnapshotWrites();
@@ -122,15 +124,12 @@
 
     std::vector<std::string> patchfiles_;
     chromeos_update_engine::DeltaArchiveManifest manifest_;
+    bool metadata_super_ = false;
 };
 
-MapSnapshots::MapSnapshots(std::string path) {
-    sm_ = SnapshotManager::New();
-    if (!sm_) {
-        std::cout << "Failed to create snapshotmanager";
-        exit(1);
-    }
+MapSnapshots::MapSnapshots(std::string path, bool metadata_super) {
     snapshot_dir_path_ = path + "/";
+    metadata_super_ = metadata_super;
 }
 
 std::string MapSnapshots::GetGroupName(const android::fs_mgr::LpMetadata& pt,
@@ -150,6 +149,12 @@
 }
 
 bool MapSnapshots::PrepareUpdate() {
+    if (metadata_super_ && !CreateScratchOtaMetadataOnSuper()) {
+        LOG(ERROR) << "Failed to create OTA metadata on super";
+        return false;
+    }
+    sm_ = SnapshotManager::New();
+
     auto source_slot = fs_mgr_get_slot_suffix();
     auto source_slot_number = SlotNumberForSlotSuffix(source_slot);
     auto super_source = fs_mgr_get_super_partition_name(source_slot_number);
@@ -234,14 +239,22 @@
 
 bool MapSnapshots::GetCowDevicePath(std::string partition_name, std::string* cow_path) {
     auto& dm = android::dm::DeviceMapper::Instance();
-    std::string cow_device = partition_name + "-cow";
+
+    std::string cow_device = partition_name + "-cow-img";
+    if (metadata_super_) {
+        // If COW device exists on /data, then data wipe cannot be done.
+        if (dm.GetDmDevicePathByName(cow_device, cow_path)) {
+            LOG(ERROR) << "COW device exists on /data: " << *cow_path;
+            return false;
+        }
+    }
+
+    cow_device = partition_name + "-cow";
     if (dm.GetDmDevicePathByName(cow_device, cow_path)) {
         return true;
     }
 
     LOG(INFO) << "Failed to find cow path: " << cow_device << " Checking the device for -img path";
-    // If the COW device exists only on /data
-    cow_device = partition_name + "-cow-img";
     if (!dm.GetDmDevicePathByName(cow_device, cow_path)) {
         LOG(ERROR) << "Failed to cow path: " << cow_device;
         return false;
@@ -321,6 +334,12 @@
 }
 
 bool MapSnapshots::BeginUpdate() {
+    if (metadata_super_ && !CreateScratchOtaMetadataOnSuper()) {
+        LOG(ERROR) << "Failed to create OTA metadata on super";
+        return false;
+    }
+    sm_ = SnapshotManager::New();
+
     lock_ = sm_->LockExclusive();
     std::vector<std::string> snapshots;
     sm_->ListSnapshots(lock_.get(), &snapshots);
@@ -470,10 +489,12 @@
 }
 
 bool MapSnapshots::UnmapCowImagePath(std::string& name) {
+    sm_ = SnapshotManager::New();
     return sm_->UnmapCowImage(name);
 }
 
 bool MapSnapshots::DeleteSnapshots() {
+    sm_ = SnapshotManager::New();
     lock_ = sm_->LockExclusive();
     if (!sm_->RemoveAllUpdateState(lock_.get())) {
         LOG(ERROR) << "Remove All Update State failed";
@@ -583,13 +604,19 @@
     }
 
     if (argc < 3) {
-        std::cerr << " apply-update <directory location where snapshot patches are present>"
+        std::cerr << " apply-update <directory location where snapshot patches are present> {-w}"
                      "    Apply the snapshots to the COW block device\n";
         return false;
     }
 
     std::string path = std::string(argv[2]);
-    MapSnapshots cow(path);
+    bool metadata_on_super = false;
+    if (argc == 4) {
+        if (std::string(argv[3]) == "-w") {
+            metadata_on_super = true;
+        }
+    }
+    MapSnapshots cow(path, metadata_on_super);
     if (!cow.ApplyUpdate()) {
         return false;
     }
@@ -607,7 +634,7 @@
     }
 
     if (argc < 3) {
-        std::cerr << " map-snapshots <directory location where snapshot patches are present>"
+        std::cerr << " map-snapshots <directory location where snapshot patches are present> {-w}"
                      "    Map all snapshots based on patches present in the directory\n";
         return false;
     }
@@ -638,7 +665,14 @@
         }
     }
 
-    MapSnapshots cow(path);
+    bool metadata_on_super = false;
+    if (argc == 4) {
+        if (std::string(argv[3]) == "-w") {
+            metadata_on_super = true;
+        }
+    }
+
+    MapSnapshots cow(path, metadata_on_super);
     if (!cow.BeginUpdate()) {
         LOG(ERROR) << "BeginUpdate failed";
         return false;
diff --git a/fs_mgr/libsnapshot/snapuserd/Android.bp b/fs_mgr/libsnapshot/snapuserd/Android.bp
index 9e14156..734066b 100644
--- a/fs_mgr/libsnapshot/snapuserd/Android.bp
+++ b/fs_mgr/libsnapshot/snapuserd/Android.bp
@@ -42,6 +42,7 @@
     static_libs: [
         "libcutils_sockets",
         "libfs_mgr_file_wait",
+        "libdm",
     ],
     shared_libs: [
         "libbase",
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp b/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp
index 789c980..ddefb9f 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp
@@ -35,6 +35,7 @@
 #include <android-base/properties.h>
 #include <android-base/strings.h>
 #include <fs_mgr/file_wait.h>
+#include <libdm/dm.h>
 #include <snapuserd/snapuserd_client.h>
 
 namespace android {
@@ -333,7 +334,21 @@
 }
 
 std::string SnapuserdClient::GetDaemonAliveIndicatorPath() {
-    return "/metadata/ota/" + std::string(kDaemonAliveIndicator);
+    std::string metadata_dir;
+    std::string temp_metadata_mnt = "/mnt/scratch_ota_metadata_super";
+
+    auto& dm = ::android::dm::DeviceMapper::Instance();
+    auto partition_name = android::base::Basename(temp_metadata_mnt);
+
+    bool invalid_partition = (dm.GetState(partition_name) == dm::DmDeviceState::INVALID);
+    std::string temp_device;
+    if (!invalid_partition && dm.GetDmDevicePathByName(partition_name, &temp_device)) {
+        metadata_dir = temp_metadata_mnt + "/" + "ota/";
+    } else {
+        metadata_dir = "/metadata/ota/";
+    }
+
+    return metadata_dir + std::string(kDaemonAliveIndicator);
 }
 
 bool SnapuserdClient::IsTransitionedDaemonReady() {
diff --git a/init/first_stage_mount.cpp b/init/first_stage_mount.cpp
index 927b45f..ece430b 100644
--- a/init/first_stage_mount.cpp
+++ b/init/first_stage_mount.cpp
@@ -371,6 +371,14 @@
     }
 
     if (SnapshotManager::IsSnapshotManagerNeeded()) {
+        auto init_devices = [this](const std::string& device) -> bool {
+            if (android::base::StartsWith(device, "/dev/block/dm-")) {
+                return block_dev_init_.InitDmDevice(device);
+            }
+            return block_dev_init_.InitDevices({device});
+        };
+
+        SnapshotManager::MapTempOtaMetadataPartitionIfNeeded(init_devices);
         auto sm = SnapshotManager::NewForFirstStageMount();
         if (!sm) {
             return false;