Merge "remount: prefer 'cache' backing storage for non-A/B devices"

namespace {

constexpr char kDataScratchSizeMbProp[] = "fs_mgr.overlayfs.data_scratch_size_mb";

constexpr char kPreferCacheBackingStorageProp[] = "fs_mgr.overlayfs.prefer_cache_backing_storage";

bool fs_mgr_access(const std::string& path) {

    return access(path.c_str(), F_OK) == 0;

const auto kScratchMountPoint = "/mnt/scratch"s;

const auto kCacheMountPoint = "/cache"s;

bool IsABDevice() {

    return !android::base::GetProperty("ro.boot.slot_suffix", "").empty();

}

std::vector<const std::string> OverlayMountPoints() {

    // Never fallback to legacy cache mount point if within a DSU system,

    // because running a DSU system implies the device supports dynamic

    if (fs_mgr_is_dsu_running()) {

        return {kScratchMountPoint};

    }

    // For non-A/B devices prefer cache backing storage if

    // kPreferCacheBackingStorageProp property set.

    if (!IsABDevice() &&

        android::base::GetBoolProperty(kPreferCacheBackingStorageProp, false) &&

        android::base::GetIntProperty("ro.vendor.api_level", -1) < __ANDROID_API_T__) {

        return {kCacheMountPoint, kScratchMountPoint};

    }

    return {kScratchMountPoint, kCacheMountPoint};

}