how to retrun different size to different process when I use ecryptfs

[zhangzhilei <sdhzdmzzl@sina.com>]

Hi

    a file named 1.txt ,and the content is 1234,when mounted ecryptfs, size
is 4,after umounted ecryptfs, size is 12288.
    I have  implemented a feature like this by modify ecryptfs source code:
    1:when gedit read this file, return size is 4,and the content  is 1234;
    2:when some other process read this file, the content is like what
umounted read;

    when file is close, I use i_size_write to write back the size of file;
    after gedit close the file ,use stat ,size is 4;
    after any other process close the file,use stat ,size is 12288;

    what I want to ask is how can different size return when different
process read size by stat。 
     i.e：the file size is 100;when process a stats it, return size 1000,and
when process stats it, return size 100;
     but when I use stat, it appears that stat direct read cache ,not goes
into ecryptfs's procedure;

     thank you!