Merge "libsnapshot: Remove all image data and metadata when cancelling an update."

    auto file = LockExclusive();

    if (!file) return false;

    // Purge the ImageManager just in case there is a corrupt lp_metadata file

    // lying around. (NB: no need to return false on an error, we can let the

    // update try to progress.)

    images_->RemoveAllImages();

    auto state = ReadUpdateState(file.get());

    if (state != UpdateState::None) {

        LOG(ERROR) << "An update is already in progress, cannot begin a new update";

    }

    bool ok = true;

    bool has_mapped_cow_images = false;

    for (const auto& name : snapshots) {

        ok &= (UnmapPartitionWithSnapshot(lock, name) && DeleteSnapshot(lock, name));

        if (!UnmapPartitionWithSnapshot(lock, name) || !DeleteSnapshot(lock, name)) {

            // Remember whether or not we were able to unmap the cow image.

            auto cow_image_device = GetCowImageDeviceName(name);

            has_mapped_cow_images |= images_->IsImageMapped(cow_image_device);

            ok = false;

        }

    }

    if (ok || !has_mapped_cow_images) {

        // Delete any image artifacts as a precaution, in case an update is

        // being cancelled due to some corrupted state in an lp_metadata file.

        // Note that we do not do this if some cow images are still mapped,

        // since we must not remove backing storage if it's in use.

        if (!images_->RemoveAllImages()) {

            LOG(ERROR) << "Could not remove all snapshot artifacts";

            return false;

        }

    }

    return ok;

}