iotests: Test preallocated truncate of 2G image

Signed-off-by: NMax Reitz <mreitz@redhat.com>
Message-id: 20180228131315.30194-3-mreitz@redhat.com
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

tests/qemu-iotests/106

@@ -86,6 +86,30 @@ for growth_mode in falloc full off; do
     $QEMU_IMG resize -f "$IMGFMT" --shrink --preallocation=$growth_mode "$TEST_IMG" -${GROWTH_SIZE}K
 done
 
+echo
+echo '=== Testing image growth on 2G empty image ==='
+
+for growth_mode in falloc full; do
+    echo
+    echo "--- growth_mode=$growth_mode ---"
+
+    # Maybe we want to do an lseek() to the end of the file before the
+    # preallocation; if the file has a length of 2 GB, that would
+    # return an integer that overflows to negative when put into a
+    # plain int.  We should use the correct type for the result, and
+    # this tests we do.
+
+    _make_test_img 2G
+    $QEMU_IMG resize -f "$IMGFMT" --preallocation=$growth_mode "$TEST_IMG" +${GROWTH_SIZE}K
+
+    actual_size=$($QEMU_IMG info -f "$IMGFMT" "$TEST_IMG" | grep 'disk size')
+    actual_size=$(echo "$actual_size" | sed -e 's/^[^0-9]*\([0-9]\+\).*$/\1/')
+
+    if [ $actual_size -lt $GROWTH_SIZE ]; then
+        echo "ERROR: Image should have at least ${GROWTH_SIZE}K, but has ${actual_size}K"
+    fi
+done
+
 # success, all done
 echo '*** done'
 rm -f $seq.full

tests/qemu-iotests/106.out

@@ -47,4 +47,14 @@ qemu-img: Preallocation can only be used for growing images
 
 --- growth_mode=off ---
 Image resized.
+
+=== Testing image growth on 2G empty image ===
+
+--- growth_mode=falloc ---
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2147483648
+Image resized.
+
+--- growth_mode=full ---
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2147483648
+Image resized.
 *** done