Date: Tue, 27 Sep 2011 09:49:08 +0300 From: Mikolaj Golub <trociny@freebsd.org> To: Robert Millan <rmh@freebsd.org> Cc: Josef Karthauser <joe@freebsd.org>, freebsd-fs@freebsd.org, freebsd-bugs@freebsd.org, Adrian Chadd <adrian@freebsd.org>, Mikolaj Golub <trociny@freebsd.org>, FreeBSD-gnats-submit@freebsd.org Subject: Re: kern/159663: sockets don't work though nullfs mounts Message-ID: <86litajx97.fsf@in138.ua3> In-Reply-To: <CAOfDtXPjC2n4sKA%2BEHQV-V1QqgqGeShQQJ8Ertw5eP-pb2APLQ@mail.gmail.com> (Robert Millan's message of "Tue, 27 Sep 2011 07:36:28 %2B0200") References: <201108102152.p7ALqUl4075207@red.freebsd.org> <201108102200.p7AM0Nu9026320@freefall.freebsd.org> <CAOfDtXMa6r%2BK5ZmTfuKV5qXNOoqS7kJvRhy4W%2B0jwBhFqfk1PQ@mail.gmail.com> <CAOfDtXM45OT-aZ71-=JE7ZaG4%2B4Db1y4poO9L%2BePZW2%2BAMFXXg@mail.gmail.com> <CAOfDtXMtqd8WonbdwBWL1vaFNte47G-Qo4JAskgM0Y99Ru6U2g@mail.gmail.com> <86k48wz3mc.fsf@kopusha.home.net> <CAOfDtXPjC2n4sKA%2BEHQV-V1QqgqGeShQQJ8Ertw5eP-pb2APLQ@mail.gmail.com>
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[-- Attachment #1 --]
RM> 2011/9/25 Mikolaj Golub <trociny@freebsd.org>:
>> As a proof of concept below is a patch that implements it.
RM> This works very well, I'm currently using your patch to run X11 over a
RM> nullfs-mounted /tmp.
>> The issues with this approach I see so far:
>>
>> - we need an additional flag for namei;
RM> What does this involve?
Well, adding yet another flag just to handle this one case might be not very
good idea :-)
But actually it is possible to do without the additional flag, with the only
hack in nullfs code: in lookup and create return lower vnode if it is a
socket, like in the patch below. It works for me but I have not tested much
and not checked yet if use cases are possible when this makes undesirable
effect.
--
Mikolaj Golub
[-- Attachment #2 --]
Index: sys/fs/nullfs/null_vnops.c
===================================================================
--- sys/fs/nullfs/null_vnops.c (revision 225757)
+++ sys/fs/nullfs/null_vnops.c (working copy)
@@ -365,16 +365,38 @@ null_lookup(struct vop_lookup_args *ap)
vrele(lvp);
} else {
error = null_nodeget(dvp->v_mount, lvp, &vp);
- if (error)
+ if (error) {
vput(lvp);
- else
+ } else if (vp->v_type == VSOCK) {
+ vref(lvp);
+ vrele(vp);
+ *ap->a_vpp = lvp;
+ } else {
*ap->a_vpp = vp;
+ }
}
}
return (error);
}
static int
+null_create(struct vop_create_args *ap)
+{
+ struct vnode *vp, *lvp;
+ int retval;
+
+ retval = null_bypass(&ap->a_gen);
+ vp = *ap->a_vpp;
+ if (retval == 0 && vp->v_type == VSOCK) {
+ lvp = NULLVPTOLOWERVP(vp);
+ vref(lvp);
+ vrele(vp);
+ *ap->a_vpp = lvp;
+ }
+ return (retval);
+}
+
+static int
null_open(struct vop_open_args *ap)
{
int retval;
@@ -826,6 +848,7 @@ struct vop_vector null_vnodeops = {
.vop_accessx = null_accessx,
.vop_advlockpurge = vop_stdadvlockpurge,
.vop_bmap = VOP_EOPNOTSUPP,
+ .vop_create = null_create,
.vop_getattr = null_getattr,
.vop_getwritemount = null_getwritemount,
.vop_inactive = null_inactive,
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