Re: [PATCH 0/8] FUSE improvements + VFS changes

[Jamie Lokier <jamie@shareable.org>]

Bryan Henderson wrote:
> Besides the scope of statfs, I know another thing that defines the 
> separation between two filesystems:  you can't link or relink across 
> filesystems.  In sshfs, you probably get a failure if you try to move a 
> file from a directory in one remote filesystem to one in another remote 
> filesystem, even though according to the Linux view, they're both in the 
> same filesystem.  (And even if it doesn't fail, it certainly doesn't do 
> what you expect from rename()).

Other things that various software depends on:

   st_dev changes across a mount point (inode number space), so that
   (st_dev, st_ino) uniquely identifies each file (as long as they are
   open, on some filesystems that don't have real inode numbers).  In
   particular, identical (st_dev, st_ino) for two paths imply the
   paths are hard links.

   After finding st_nlink different paths referring to the same
   (st_dev, st_ino) pair, one may assume that's all the links to a
   file.  (That's broken by bind mounts, unfortunately).

-- Jamie