Merge "[Bugfix]Fix userspace-reboot failure when backing_dev exists but zram not swapped on"

#define ZRAM_DEVICE       "/dev/block/zram0"

#define ZRAM_RESET        "/sys/block/zram0/reset"

#define ZRAM_BACK_DEV     "/sys/block/zram0/backing_dev"

#define ZRAM_INITSTATE    "/sys/block/zram0/initstate"

static Result<void> KillZramBackingDevice() {

    std::string zram_initstate;

    if (!android::base::ReadFileToString(ZRAM_INITSTATE, &zram_initstate)) {

        return ErrnoError() << "Failed to read " << ZRAM_INITSTATE;

    }

    zram_initstate.erase(zram_initstate.length() - 1);

    if (zram_initstate == "0") {

        LOG(INFO) << "Zram has not been swapped on";

        return {};

    }

    if (access(ZRAM_BACK_DEV, F_OK) != 0 && errno == ENOENT) {

        LOG(INFO) << "No zram backing device configured";

        return {};