linux-kernel - Re: [RFC] View-Based File System Model with Program-Scoped Isolation

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Message-ID: <nPMV5WRZT62Eq5Cu84Q0NMH2CgxAuisCAMQ4XfuG7kb6OdEOgY9UMi5sVx3CV0kSVcEBoDDz1w5btWaT1CfOCC_4jkCDrIoYk866FO9bZVo=@mcbridemail.com>
Date: Thu, 04 Sep 2025 23:41:12 +0000
From: Blake McBride <blake@...ridemail.com>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "brauner@...nel.org" <brauner@...nel.org>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, Colby Wes McBride <colbym84@...il.com>
Subject: Re: [RFC] View-Based File System Model with Program-Scoped Isolation

On Thursday, September 4th, 2025 at 6:09 PM, Al Viro <viro@...iv.linux.org.uk> wrote:

> 
> 
> On Thu, Sep 04, 2025 at 10:58:12PM +0000, Blake McBride wrote:
> 
> > Off the cuff, I'd say it is an mv option. It defaults to changing all occurrences, with an option to change it only in the current view.
> 
> 
> Huh? mv(1) is userland; whatever it does, by definition it boils down
> to a sequence of system calls.


Yes.  This is what is intended.  All of userland would just operate on the view the same as if that was your real hierarchy.


> 
> If those "views" of yours are pasted together subtrees of the global
> forest, you already can do all of that with namespaces; if they are not,
> you get all kinds of interesting questions about coherency.


These views are not pasted together subtrees.  Each view can have utterly different layouts of the same set of files.





> 
> Which one it is? Before anyone can discuss possible implementations
> and relative merits thereof, you need to define the semantics of
> what you want to implement...
> 
> And frankly, if you are thinking in terms of userland programs (file
> manglers, etc.) you are going the wrong way - description will have
> to be on the syscall level.

I did not specify the implementation, just the user experience.  All of userland would "appear" to function as it does now.  The same with the syscalls that are made by the application code.  They all effect the current view as if it was the real hierarchy.

--blake