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Subject: Re: [RFC][PATCH] rbind across namespaces

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From: Miklos Szeredi <miklos@szeredi.hu>
Date:	Tue, 24 May 2005 07:43:41 +0200

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> FWIW, all this stuff has already been done and posted here.
> 
> Detachable chunks of vfsmounts:
> http://marc.theaimsgroup.com/?l=linux-fsdevel&m=109872862003192&w=2
> 
> 'Soft' reference counts for manipulating vfsmounts without pinning them 
> down:
> http://marc.theaimsgroup.com/?l=linux-kernel&m=109872797030644&w=2

I think this might just interest Jamie Lokier.  He had a very similar
poposal recently, but without reference to this patch, so I guess he
wasn't aware of it.

> Referencing vfsmounts in userspace using a file descriptor:
> http://marc.theaimsgroup.com/?l=linux-kernel&m=109871948812782&w=2

Why not just use /proc/PID/fd/FD?

> walking mountpoints in userspace: 
> http://marc.theaimsgroup.com/?l=linux-kernel&m=109875012510262&w=2

Is this needed?  Userspace can find out mountpoints from /proc/mounts
(or something similar for detached trees).

> attaching mountpoints in userspace:
> http://marc.theaimsgroup.com/?l=linux-fsdevel&m=109875063100111&w=2

Again, bind from/to /proc/PID/fd/FD should work without any new
interfaces.

> detaching mountpoints in userspace:
> http://marc.theaimsgroup.com/?l=linux-kernel&m=109880051800963&w=2

What's wrong with sys_umount()?

> getting info from a vfsmount:
> http://marc.theaimsgroup.com/?l=linux-kernel&m=109875135030473&w=2

/proc or /sys should do fine for this purpose I think.

I agree, that having "floating trees" could be useful, but I don't see
the point of adding new interfaces to support it.

Miklos
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