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Date: Fri, 27 Aug 2004 00:40:48 +0100
From: viro@parcelfarce.linux.theplanet.co.uk
To: Linus Torvalds <torvalds@osdl.org>
Cc: Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua>,
       Rik van Riel <riel@redhat.com>, Diego Calleja <diegocg@teleline.es>,
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Subject: Re: [some sanity for a change] possible design issues for hybrids
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References: <Pine.LNX.4.58.0408261132150.2304@ppc970.osdl.org> <20040826191323.GY21964@parcelfarce.linux.theplanet.co.uk> <20040826203228.GZ21964@parcelfarce.linux.theplanet.co.uk> <Pine.LNX.4.58.0408261344150.2304@ppc970.osdl.org> <20040826212853.GA21964@parcelfarce.linux.theplanet.co.uk> <Pine.LNX.4.58.0408261436480.2304@ppc970.osdl.org> <20040826223625.GB21964@parcelfarce.linux.theplanet.co.uk> <Pine.LNX.4.58.0408261538030.2304@ppc970.osdl.org> <20040826225308.GC21964@parcelfarce.linux.theplanet.co.uk> <Pine.LNX.4.58.0408261619230.2304@ppc970.osdl.org>
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On Thu, Aug 26, 2004 at 04:24:51PM -0700, Linus Torvalds wrote:
> So basically: the "d_mounted++" just makes sure we get into
> "lookup_mnt()". That's where we will usually find the actual mount thing.
> 
> And that's also where the special case comes in: if we _don't_ find the 
> mount thing there, that's where we need to create it. That will only 
> happen if somebody looks it up using another namespace, though, so it 
> should be rare.

No.  Trivial example:

mount --bind /foo /bar
mount /dev/sda1 /bar/baz

do lookup for /foo/baz.  No namespaces involved, no vfsmounts found, d_mounted
positive and we certainly do *not* want anything to be created at that point.