File: 99plan.txt

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# Copyright (C) 2005-2014 Junjiro R. Okajima
# 
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

Plan

Restoring some features which was implemented in aufs1.
They were dropped in aufs2 in order to make source files simpler and
easier to be reviewed.


Being Another Aufs's Readonly Branch (robr)
----------------------------------------------------------------------
Aufs1 allows aufs to be another aufs's readonly branch.
This feature was developed by a user's request. But it may not be used
currecnly.


Refresh the Opened File (refrof)
----------------------------------------------------------------------
This option is implemented in aufs1 but incomplete.

When user reads from a file, he expects to get its latest filedata
generally. If the file is removed and a new same named file is created,
the content he gets is unchanged, ie. the unlinked filedata.

Let's try case study again.
- aufs has two branches.
  /au = /rw + /ro
- "fileA" exists under /ro, but /rw.
- user opened "/au/fileA".
- he or someone else inserts a branch (/new) between /rw and /ro.
  /au = /rw + /new + /ro
- the new branch has "fileA".
- user reads from the opened "fileA"
- which filedata should aufs return, from /ro or /new?

Some people says it has to be "from /ro" and it is a semantics of Unix.
The others say it should be "from /new" because the file is not removed
and it is equivalent to the case of someone else modifies the file.

Here again I don't have a best and final answer. I got an idea to
implement 'refrof' and 'norefrof' option. When 'refrof' (REFResh the
Opened File) is specified (by default), aufs returns the filedata from
/new.
Otherwise from /new.