Re: Adding subroot information to /proc/mounts, or obtaining that through other means

H. Peter Anvin
2007-06-22T07:56:33Z

Ram Pai wrote:
>
> Ok. so you think /proc/mounts can be extended easily without breaking
> any userspace commands?
>
> well lets see..
> 1. to disambiguate bind mounts, we have to add a field that displays the
> path to the mount's root dentry from the filesystem's root
> dentry. Agree?
>
> 2. For filesystems that do not have a backing store, it becomes hard
> to disambiguate bind mounts in (1). So we need to add a
> filesystem-id field.
>
> 3. if we need to add the propagation status of the mount we need a
> propagation flag added in the output.
>
> 4. To be able to construct the propagation tree, we need a way to refer
> to the other mounts, since some mounts are peers and some other
> mounts are master. Which means we need a mount-id field.
> Agree?
>
> If you agree to the above 4 new fields, it becomes challenging to
> extend /proc/mounts to incorporate these new fields without
> breaking any existing applications.
>

No, I don't think so. I suspect, in fact, that as long as we add the
new fields to the right (obviously) we should be fine. There aren't all
that many users of /proc/mounts, and even fewer that don't use the
library functions (getmntent et al.)

-hpa