linux-kernel - Re: [RFC PATCH] file as directory

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Message-Id: <E1HqnrQ-0001eH-00@dorka.pomaz.szeredi.hu>
Date:	Wed, 23 May 2007 12:14:28 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	viro@....linux.org.uk
CC:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org
Subject: Re: [RFC PATCH] file as directory

> On Wed, May 23, 2007 at 11:03:08AM +0200, Miklos Szeredi wrote:
> > I still don't get it where the superblock comes in.  The locking is
> > "interesting" in there, yes.  And I haven't completely convinced
> > myself it's right, let alone something that won't easily be screwed up
> > in the future.  So there's definitely room for thought there.
> > 
> > But how does it matter if two different paths have the same sb or a
> > different sb mounted over them?
>  
> Because then you get a slew of fun issues with dropping the final reference
> to vfsmount vs. lookup on another place.  What hold do you have on that
> superblock and when do you switch from "oh, called ->enter() on the same
> inode again, return vfsmount over the same superblock" to "need to
> initialize that damn superblock, all mounts are gone"?
> 
> > The same dentry is mounted over each one.  The contents of the
> > directory should only depend on the contents of the underlying inode.
> > The path leading up to it is completely irrelevant.
> 
> So what kind of exclusion do you have for ->enter()?  None?
> 

So really these issues, are about how do we get hold of the superblock
to mount.

I think that should be a filesystem internal problem, and I suspect
the easiest solution is to just have a permanent meta superblock for
these dir-on-file mounts.

Miklos
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