Re: [PATCH 01/24] Unionfs: Documentation

[Andrew Morton <akpm@osdl.org>]

On Mon, 8 Jan 2007 14:43:39 -0500 (EST)
Shaya Potter <spotter@cs.columbia.edu> wrote:

> On Mon, 8 Jan 2007, Andrew Morton wrote:
> 
> > On Sun,  7 Jan 2007 23:12:53 -0500
> > "Josef 'Jeff' Sipek" <jsipek@cs.sunysb.edu> wrote:
> >
> >> +Modifying a Unionfs branch directly, while the union is mounted, is
> >> +currently unsupported.
> >
> > Does this mean that if I have /a/b/ and /c/d/ unionised under /mnt/union, I
> > am not allowed to alter anything under /a/b/ and /c/d/?  That I may only
> > alter stuff under /mnt/union?
> >
> > If so, that sounds like a significant limitation.
> 
> haven't we been through this?

If it's not in the changelog or the documentation, it doesn't exist.  It's
useful for the developers to keep track of obvious and frequently-asked
questions such as this and to address them completely in the changelog
and/or documentation.  Otherwise things just come around again and again,
as we see here.

>  It's the same thing as modifying a block 
> device while a file system is using it.  Now, when unionfs gets confused, 
> it shouldn't oops, but would one expect ext3 to allow one to modify its 
> backing store while its using it?

There's no such problem with bind mounts.  It's surprising to see such a
restriction with union mounts.