Fix issue #232: Handle size mismatch after file copy

data/contents/1/ls/$.

@@ -0,0 +1 @@
+�(�Wg5�	O����UM挃QF�u�}�i4���(�O*��

data/inodes/1

@@ -0,0 +1,3 @@
+��B
3��Wh+2��Pf7|>
+L𨑆J���x�h� ������O������Y/x׾ʚ�ҋ�R�
+�Z5�rA���P���ǘ�n�仢8���4�j�/Z����S=! ����ҁtSv��W?��

data/security/key.enc

@@ -0,0 +1 @@
+s^�t��G�|�wON��f�g&�Nb�{=ɱ�����5���Xe}
�m�2U���x��^��~��>�&

final/a/DATA_DIR/contents/1/hash/$.

@@ -0,0 +1 @@
+x�Q=]9"���6�����_���V9�^+��g��1�wGA�����ҟ�U-o

final/a/DATA_DIR/contents/1/ls/$.

@@ -0,0 +1 @@
+Uϳ�0k�Ũ����c����VR��Q����^[)���

final/a/DATA_DIR/inodes/1

@@ -0,0 +1 @@
+J�wX�I���6�qk�`e㍝Z}i�G�ė5���i۟aS��.TC���_�\�^�:�V��o�,$ɐ�
�����^]�U�i�x��P<D���LǪ��8u#�FF1��̜S�ZJ�n���v

final/a/DATA_DIR/security/key.enc

@@ -0,0 +1 @@
+ ��4�|���Y\���WDF���4����X�a���W5�{�VG�L�U4���7�t�S�I-_�1�*�

final/a/test.txt

@@ -0,0 +1 @@
+test

src/encryptedfs.rs

@@ -1659,11 +1659,25 @@ impl EncryptedFs {
             } else {
                 buf
             };
-            let len = writer.write(buf).map_err(|err| {
-                error!(err = %err, "writing");
-                err
-            })?;
-            (writer.stream_position()?, len)
+            // let len = writer.write(buf).map_err(|err| {
+            //     error!(err = %err, "writing");
+            //     err
+            // })?;
+            // (writer.stream_position()?, len)
+            let mut total_written = 0;
+            while total_written < buf.len() {
+                let slice = &buf[total_written..];
+                let written = writer.write(slice).map_err(|err| {
+                    error!(err = %err, "writing");
+                    err
+                })?;
+                if written == 0 {
+                    return Err(FsError::Other("Write returned 0 before buffer fully written"));
+                }
+                total_written += written;
+            }
+            let pos = writer.stream_position()?;
+            (pos, total_written)
         };
 
         // let size = ctx.attr.size;