Date: Mon, 9 Mar 2009 22:42:06 +0000 From: "Paul B. Mahol" <onemda@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: nullfs: panic: vrele: negative ref cnt Message-ID: <3a142e750903091542x7514f74eod294cb15f4ddf1b8@mail.gmail.com> In-Reply-To: <200903091642.25311.jhb@freebsd.org> References: <3a142e750903090615t63a594e8rbadd7f7231049180@mail.gmail.com> <200903091642.25311.jhb@freebsd.org>
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On 3/9/09, John Baldwin <jhb@freebsd.org> wrote:
> On Monday 09 March 2009 9:15:22 am Paul B. Mahol wrote:
>> Hi,
>> here is part of textdump:
>>
>> panic(c061db9e,0,c061cee6,88e,4,...) at panic+0x136
>> vrele(c4326d9c,0,c433fb5f,82,c060f3c7,...) at vrele+0x111
>> null_nodeget(c3fd4780,c4326d9c,c3ba8bf4,0,c3ba8be4,...) at
>> null_nodeget+0xa0
>> null_bypass(c3ba8be0,c3f35a78,c3ba8c28) at null_bypass+0x141
>> VOP_VPTOCNP_APV(c4340240,c3ba8be0,c061bf01,387,c3cecc00,...) at
>> VOP_VPTOCNP_APV+0xb3
>
> Try this. null_bypass() can't handle VOP_VPTOCNP because VPTOCNP doesn't
> return a vnode that is locked and VREF'd, but just a vnode that is
> vhold()'d.
> This patch attempts to give nullfs a VOP_VPTONCP() method which remaps the
> directory vnode properly on return by locking the directory vnode while
> invoking null_nodeget().
It livelocks active vty into [ufs] state. Will try with WITNESS kernel soon.
load: 0.01 cmd: sh 1058 [ufs] 0.00u 0.02s 0% 1672k
> --- //depot/user/jhb/lock/fs/nullfs/null_vnops.c
> +++ /home/jhb/work/p4/lock/fs/nullfs/null_vnops.c
> @@ -722,6 +722,34 @@
> return VOP_VPTOFH(lvp, ap->a_fhp);
> }
>
> +static int
> +null_vptocnp(struct vop_vptocnp_args *ap)
> +{
> + struct vnode *lvp, *dvp;
> + int error;
> +
> + /*
> + * We can't use null_bypass() because 'dvp' is not returned
> + * locked. It is merely 'vhold()'ed.
> + */
> + lvp = NULLVPTOLOWERVP(ap->a_vp);
> + error = VOP_VPTOCNP(lvp, &dvp, ap->a_buf, ap->a_buflen);
> + if (error)
> + return (error);
> +
> + /*
> + * Map 'dvp' to the corresponding null node. We have to lock
> + * it before calling null_nodeget().
> + */
> + vn_lock(dvp, LK_SHARED | LK_RETRY);
> + error = null_nodeget(ap->a_vp->v_mount, dvp, ap->a_vpp);
> + if (error) {
> + vrele(dvp);
> + vdrop(dvp);
> + }
> + return (error);
> +}
> +
> /*
> * Global vfs data structures
> */
> @@ -743,4 +771,5 @@
> .vop_strategy = VOP_EOPNOTSUPP,
> .vop_unlock = null_unlock,
> .vop_vptofh = null_vptofh,
> + .vop_vptocnp = null_vptocnp,
> };
>
>
> --
> John Baldwin
>
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