Date: Fri, 16 Feb 2007 12:54:39 +0000 (GMT) From: Robert Watson <rwatson@FreeBSD.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: Josef Karthauser <joe@freebsd.org>, hackers@freebsd.org, Jeremie Le Hen <jeremie@le-hen.org>, fs@freebsd.org Subject: Re: nullfs and named pipes. Message-ID: <20070216125007.D38234@fledge.watson.org> In-Reply-To: <20070215153135.GI39168@deviant.kiev.zoral.com.ua> References: <20070204023711.GA3393@genius.tao.org.uk> <20070215135750.GR64768@obiwan.tataz.chchile.org> <20070215152259.GA2950@genius.tao.org.uk> <20070215153135.GI39168@deviant.kiev.zoral.com.ua>
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On Thu, 15 Feb 2007, Kostik Belousov wrote: > On Thu, Feb 15, 2007 at 03:22:59PM +0000, Josef Karthauser wrote: >> On Thu, Feb 15, 2007 at 02:57:50PM +0100, Jeremie Le Hen wrote: >>> >>> Note that all processes within a jail can only intefere with processes >>> from another jail or host as if they were on different machines. This >>> means they can communicate through PF_INET for instance but not PF_LOCAL. >> >> You might think so! However that's not what's going on here. >> >> The named pipe/nullfs issue is nothing to do with jails. It's just that >> nullfs is broken with respect to named pipes as I've previously reported. >> However with this patch: >> >> cvs diff: Diffing . >> Index: null_subr.c >> =================================================================== >> RCS file: /home/ncvs/src/sys/fs/nullfs/null_subr.c,v >> retrieving revision 1.48.2.1 >> diff -u -r1.48.2.1 null_subr.c >> --- null_subr.c 13 Mar 2006 03:05:17 -0000 1.48.2.1 >> +++ null_subr.c 14 Feb 2007 00:02:28 -0000 >> @@ -235,6 +235,8 @@ >> xp->null_vnode = vp; >> xp->null_lowervp = lowervp; >> vp->v_type = lowervp->v_type; >> + if (vp->v_type == VSOCK || vp->v_type == VFIFO) >> + vp->v_un = lowervp->v_un; > > I'm wondering is some reference counting needed there ? Yes, I find this a bit worrying also, but I don't know enough about how nullfs works to reason about it. What happens when a vnode in the bottom layer has its on-disk reference count drop to zero -- is the vnode in the top layer invalidated somehow? Robert N M Watson Computer Laboratory University of Cambridge
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