Re: nullfs and named pipes.


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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Relevant Pages

  • Re: nullfs and named pipes.
    ... Note that all processes within a jail can only intefere with processes ... nullfs is broken with respect to named pipes as I've previously reported. ... What happens when a vnode in the bottom ... Vnode reclamation from lower layer cannot do anithing for corresponding nullfs ...
    (freebsd-hackers)
  • Re: nullfs and named pipes.
    ... Note that all processes within a jail can only intefere with processes ... from another jail or host as if they were on different machines. ... The named pipe/nullfs issue is nothing to do with jails. ... cvs diff: Diffing. ...
    (freebsd-hackers)