[PATCH] ext3: zero freed blocks

[Ron Yorston]

Theodore Tso <tytso at mit.edu> wrote:
>1) File gets deleted; the file contents get zero'ed out via the the
>buffer cache.  Since process of zeroing the files happen in the
>background, for a large file, this could continue for a long time...
>
>2) In the meantime, one or more of the disk blocks that was used by
>the old file are reallocated for a new file.  The application writes
>data to the new file, which is stored in the page cache.
>
>3) The application calls fsync() and the contents of the new file are
>flushed from the page cache and written to disk.
>
>4) The dirty buffers containing the zero'ed out contents of the block
>are written to disk, overwriting the contents of the new file.
>
>5) Data is lost.

I'm having no luck in generating any data loss with this sequence of
events.  Any suggestions as to how it might be possible to force it
to happen?

Ron