linux-kernel - Re: [PATCH 30/38] vfs: syscall: Add fsmount() to create a mount for a superblock [ver #10]

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Message-ID: <8835.1532729179@warthog.procyon.org.uk>
Date:   Fri, 27 Jul 2018 23:06:19 +0100
From:   David Howells <dhowells@...hat.com>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     dhowells@...hat.com, viro@...iv.linux.org.uk,
        linux-api@...r.kernel.org, torvalds@...ux-foundation.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 30/38] vfs: syscall: Add fsmount() to create a mount for a superblock [ver #10]

Andy Lutomirski <luto@...capital.net> wrote:

> I have a potentially silly objection. For the old timers, "mount" means to
> stick a reel of tape or some similar object onto a reader, which seems to
> imply that "mount" means to start up the filesystem. For younguns, this
> meaning is probably lost, and the more obvious meaning is to "mount" it into
> some location in the VFS hierarchy a la vfsmount. The patch description
> doesn't disambiguate it, and obviously people used to mount(2)/mount(8) are
> just likely to be confused.

The problem is that inside the kernel it *is* a "mount".

How about I change the first paragraph to:

	Provide a system call by which a filesystem opened with fsopen() and
	configured by a series of fsconfig() calls can have a detached mount
	object created for it.  This mount object can then be attached to the
	VFS mount hierarchy using move_mount() by passing the returned file
	descriptor as the from directory fd.

> At the very least, your description should make it absolutely clear what you
> mean. Even better IMO would be to drop the use of the word "mount" entirely

I'm not sure that's a reasonable idea, given the "mounting" is how this is
done.

Can you suggest a word that encapsulates what it is that fsmount() returns?
It's almost, but not quite identical with what open(O_PATH) returns, since it
has to be torn down if not actually mounted somewhere when the fd is closed.

> and maybe rename the syscall.
> 
> From a very brief reading, I think you are giving it the meaning that would
> be implied by fsstart(2).

Do you have a reference for the manpage for that?  Google doesn't seem to find
it.

David