Date: Wed, 1 Nov 2006 15:10:00 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Ulrich Spoerlein <uspoerlein@gmail.com> Cc: stable@freebsd.org, Kris Kennaway <kris@obsecurity.org> Subject: Re: panic: vfs_getopt: caller passed 'opts' as NULL Message-ID: <20061101131000.GT1627@deviant.kiev.zoral.com.ua> In-Reply-To: <7ad7ddd90611010257o75546455p7da194b17037f8ed@mail.gmail.com> References: <7ad7ddd90610300741k5789f64j8f410b6e866b99ee@mail.gmail.com> <20061030224935.GA95120@xor.obsecurity.org> <7ad7ddd90610302348j6b7aabc7vc0a89e1e95d8fd27@mail.gmail.com> <20061031184150.GA27161@xor.obsecurity.org> <7ad7ddd90611010257o75546455p7da194b17037f8ed@mail.gmail.com>
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On Wed, Nov 01, 2006 at 11:57:48AM +0100, Ulrich Spoerlein wrote:
> On 10/31/06, Kris Kennaway <kris@obsecurity.org> wrote:
> >Note that they'll be demand-loaded if requested (e.g. if you try to
> >mount_nullfs). Maybe you or something else tried to mount such a
> >filesystem by accident?
> >
> >> But the point is mood anyway, since I could not reproduce the problem.
> >> I tried again after rebooting the machine and everything went just
> >> fine ...
> >>
> >> I have to use the nullfs mounts on another machine shortly, let's see
> >> what happens there.
>=20
> It reliably paniced in single user mode, with no other modules loaded
> at the time. But, I see now that nullfs.ko is loaded as a module,
> which might explain everything. I assumed it was built in.
>=20
> I rebooted to a kernel without DEBUG_VFS_LOCKS and it's happily using
> nullfs. I'll try once more with a debugging kernel, that has nullfs
> built in, but I'll guess the panic vanishes.
>=20
>=20
> Ok, with the attached kernel config, which includes nullfs, I get a
> duplicate lock, instead of a panic
> Trying to mount root from ufs:/dev/da0s1a
> acquiring duplicate lock of same type: "vnode interlock"
> 1st vnode interlock @ /usr/src/sys/kern/vfs_vnops.c:806
> 2nd vnode interlock @ /usr/src/sys/kern/vfs_subr.c:2036
> KDB: stack backtrace:
> kdb_backtrace(3,c894fa80,c0a47110,c0a47110,c09cb524,...) at=20
> kdb_backtrace+0x29
> witness_checkorder(c8622d04,9,c0951b38,7f4) at witness_checkorder+0x578
> _mtx_lock_flags(c8622d04,0,c0951b38,7f4,c840b590,...) at=20
> _mtx_lock_flags+0x78
> vrefcnt(c8622c3c) at vrefcnt+0x20
> null_checkvp(c8a7ed98,c093f5ae,215) at null_checkvp+0x56
> null_lock(eb0bba80) at null_lock+0x66
> VOP_LOCK_APV(c09c40a0,eb0bba80) at VOP_LOCK_APV+0x87
> vn_lock(c8a7ed98,1002,c894fa80,c8a7ed98,c8a89224,...) at vn_lock+0xac
> nullfs_root(c88052e4,2,eb0bbaf8,c894fa80,0,8,0,c0a84040,0,c09513da,3dd)
> at nullfs_root+0x26
> vfs_domount(c894fa80,c83e64c0,c8493490,0,c83fdad0,c0a38380,0,c09513da,2a3)
> at vfs_domount+0x975
> vfs_donmount(c894fa80,0,c87f4e00,c87f4e00,0,...) at vfs_donmount+0x2ef
> nmount(c894fa80,eb0bbd04) at nmount+0x8b
> syscall(3b,3b,3b,bfbfe435,bfbfecc8,...) at syscall+0x25b
> Xint0x80_syscall() at Xint0x80_syscall+0x1f
> --- syscall (378, FreeBSD ELF32, nmount), eip =3D 0x280ba4d7, esp =3D
> 0xbfbfe3fc, ebp =3D 0xbfbfec78 ---
>=20
This is purely cosmetic, and shall make no harm. It is caused by
debugging check. Just ignore it, or use the following to silence
WITNESS:
Index: sys/fs/nullfs/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: /usr/local/arch/ncvs/src/sys/fs/nullfs/null_subr.c,v
retrieving revision 1.50
diff -u -r1.50 null_subr.c
--- sys/fs/nullfs/null_subr.c 22 Feb 2006 06:15:12 -0000 1.50
+++ sys/fs/nullfs/null_subr.c 1 Nov 2006 11:32:48 -0000
@@ -284,6 +284,8 @@
int lno;
{
struct null_node *a =3D VTONULL(vp);
+ struct vnode *lvp;
+ int refcnt;
#ifdef notyet
/*
* Can't do this check because vop_reclaim runs
@@ -295,7 +297,8 @@
panic("null_checkvp");
};
#endif
- if (a->null_lowervp =3D=3D NULLVP) {
+ lvp =3D a->null_lowervp;
+ if (lvp =3D=3D NULLVP) {
/* Should never happen */
int i; u_long *p;
printf("vp =3D %p, ZERO ptr\n", (void *)vp);
@@ -306,7 +309,10 @@
while (null_checkvp_barrier) /*WAIT*/ ;
panic("null_checkvp");
}
- if (vrefcnt(a->null_lowervp) < 1) {
+ VI_LOCK_FLAGS(lvp, MTX_DUPOK);
+ refcnt =3D lvp->v_usecount;
+ VI_UNLOCK(lvp);
+ if (refcnt < 1) {
int i; u_long *p;
printf("vp =3D %p, unref'ed lowervp\n", (void *)vp);
for (p =3D (u_long *) a, i =3D 0; i < 8; i++)
@@ -322,6 +328,6 @@
a->null_lowervp, vrefcnt(a->null_lowervp),
fil, lno);
#endif
- return a->null_lowervp;
+ return lvp;
}
#endif
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