E2fsck fixes files that are found to be sharing blocks by cloning
the shared blocks and giving each file a private copy in pass 1D.

Allowing all files claiming the shared blocks to have copies can
inadvertantly bypass access restrictions.  Deleting all the files,
zeroing the cloned blocks, or placing the files in the /lost+found
directory after cloning may be preferable in some secure environments.

The following patches implement config file and command line options in
e2fsck that allow pass 1D behavior to be tuned according to site policy.
It adds two extended options and config file counterparts.  On the
command line:

-E clone=dup|zero

    Select the block cloning method.  "dup" is old behavior which
remains
    the default.  "zero" is a new method that substitutes zero-filled
    blocks for the shared blocks in all the files that claim them.

-E shared=preserve|lost+found|delete

    Select the disposition of files containing shared blocks.
"preserve"
    is the old behavior which remains the default.  "lost+found" causes
    files to be unlinked after cloning so they will be reconnected to
    /lost+found in pass 3.   "delete" skips cloning entirely and simply
    deletes the files.

In the config file:
  [options]
      clone=dup|zero
      shared=preserve|lost+found|delete

Signed-off-by: Jim Garlick <garlick@llnl.gov>
Signed-off-by: Kalpak Shah <kalpak.shah@sun.com>