Ensure disk is a minimum size for a valid f2fs filesystem

Signed-off-by: Michael Halcrow <mhalcrow@google.com>
diff --git a/full-run-fsverity.sh b/full-run-fsverity.sh
index c98da92..33d286e 100755
--- a/full-run-fsverity.sh
+++ b/full-run-fsverity.sh
@@ -2,7 +2,7 @@
 
 umount /mnt/f2fs
 rm -f /root/f2fs.img
-dd if=/dev/zero of=/root/f2fs.img seek=$(($1/128)) bs=512 count=1
+dd if=/dev/zero of=/root/f2fs.img seek=$(($1<16384000?128000:$1/128)) bs=512 count=1
 /root/f2fs-tools/mkfs/mkfs.f2fs -O verity /root/f2fs.img
 mount -o loop /root/f2fs.img /mnt/f2fs
 cp /root/output-$1.apk /mnt/f2fs/output-$1.apk