To: viro@ftp.linux.org.uk
CC: akpm@osdl.org, trond.myklebust@fys.uio.no, linux-kernel@vger.kernel.org
In-reply-to: <20051007144147.GE7992@ftp.linux.org.uk> (message from Al Viro on
	Fri, 7 Oct 2005 15:41:47 +0100)
Subject: Re: [PATCH] don't invalidate non-directory mountpoints
References: <E1ENqAg-0004bJ-00@dorka.pomaz.szeredi.hu> <20051007143012.GC7992@ftp.linux.org.uk> <E1ENtKD-0005Dw-00@dorka.pomaz.szeredi.hu> <20051007144147.GE7992@ftp.linux.org.uk>
Message-Id: <E1ENtTy-0005G8-00@dorka.pomaz.szeredi.hu>
From: Miklos Szeredi <miklos@szeredi.hu>
Date: Fri, 07 Oct 2005 16:45:58 +0200
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1248
Lines: 31

> > > > d_invalidate allowed a non-directory mountpoint to be invalidated,
> > > > which is bad, since the mountpoint becomes unreachable.
> > > > 
> > > > I know it's racy wrt attaching/detaching mount, but AFAICS so is
> > > > everything else that unhashes the dentry.  This seems to be an
> > > > oversight when splitting out vfsmount_lock from dcache_lock.  To be
> > > > fixed.
> > > 
> > > NAK.  That's a wrong way to deal with the problem and it's much older
> > > than vfsmount_lock or dcache_lock (and affects directories too).
> > 
> > Sorry?
> > 
> > Directories are not invalidated if they have any other reference (like
> > a mount, or any subdirectories which may have mounts).
> > 
> > So how does it affect directories?
> 
> The underlying problem is still there - parts of mount tree _can_ go
> unreachable when remote object dies; trying to pin them down is hopeless
> and the only sane way to deal with that is to dissolve the subtrees
> of mount when that happens.

I get it.

Miklos
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