Re: Fallthrus as full-length symlinks?

[hooanon05@yahoo.co.jp]

Valerie Aurora:
> Fallthrus were invented as a placeholders for readdir() on a
> union-mounted directory - basically, to use the top-level file
> system's readdir() cookie mechanism.  Fallthrus are persistent
> directory entries and are implemented by the underlying file system -
> such as ext2 or tmpfs - in whatever way it sees fit.  We've
> implemented them for ext2 in two ways: as a regular directory entry
> with a magic inode number, and as a regular directory entry with a
> special file type.
> 
> Recently, David Woodhouse suggested implementing fallthrus as
> full-length symlinks with a special flag.  The interesting thing about
> this idea is that it could theoretically let us rename a file from the
> low level file system to another place in the low-level file system
> without copying the contents of the file up.  Basically, we can
> arbitrarily swizzle the namespace of the low-level by maintaining a
> set of symlinks above.
> 
> Is this useful?  Is it implementable?

I think the idea of fallthru entry is good, even if it is implemented as
a special symlink.
How do you think about the file paths in /proc/pid/maps and
/proc/pid/fd?
They refer the file paths, and some apps depend upon these path. I
remember that the package manager in debian didn't work when the path is
wrong. (But I don't know whether it is true still).

Will FS have to support such case?


J. R. Okajima