Date: Fri, 16 Feb 2007 16:36:56 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Robert Watson <rwatson@freebsd.org> 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: <20070216143656.GM39168@deviant.kiev.zoral.com.ua> In-Reply-To: <20070216125007.D38234@fledge.watson.org> 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> <20070216125007.D38234@fledge.watson.org>
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--NZtAI5QFBF0GmLcW Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Feb 16, 2007 at 12:54:39PM +0000, Robert Watson wrote: >=20 > On Thu, 15 Feb 2007, Kostik Belousov wrote: >=20 > >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= =20 > >>>from another jail or host as if they were on different machines. This= =20 > >>>means they can communicate through PF_INET for instance but not PF_LOC= AL. > >> > >>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 tha= t=20 > >>nullfs is broken with respect to named pipes as I've previously reporte= d.=20 > >>However with this patch: > >> > >> cvs diff: Diffing . > >> Index: null_subr.c > >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > >> 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 =3D vp; > >> xp->null_lowervp =3D lowervp; > >> vp->v_type =3D lowervp->v_type; > >> + if (vp->v_type =3D=3D VSOCK || vp->v_type =3D=3D VFIFO) > >> + vp->v_un =3D lowervp->v_un; > > > >I'm wondering is some reference counting needed there ? >=20 > Yes, I find this a bit worrying also, but I don't know enough about how= =20 > nullfs works to reason about it. What happens when a vnode in the bottom= =20 > layer has its on-disk reference count drop to zero -- is the vnode in the= =20 > top layer invalidated somehow? Vnode reclamation from lower layer cannot do anithing for corresponding nul= lfs vnode, but that vnode has reference from nullfs vnode. On the other hand, can forced unmount proceed for lower layer ? --NZtAI5QFBF0GmLcW Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (FreeBSD) iD8DBQFF1cGHC3+MBN1Mb4gRAmbnAJ4rZL3YjmoJjaBDku4KTaq8fBPSbQCcDAsr S6l/UoJLOLDXyGST6j7MVjM= =1gZf -----END PGP SIGNATURE----- --NZtAI5QFBF0GmLcW--
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