panic: vfs_getopt: caller passed 'opts' as NULL

[Kostik Belousov]

On Wed, Nov 01, 2006 at 11:57:48AM +0100, Ulrich Spoerlein wrote:
> On 10/31/06, Kris Kennaway <kris at 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.
> 
> 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.
> 
> 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.
> 
> 
> 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 
> kdb_backtrace+0x29
> witness_checkorder(c8622d04,9,c0951b38,7f4) at witness_checkorder+0x578
> _mtx_lock_flags(c8622d04,0,c0951b38,7f4,c840b590,...) at 
> _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 = 0x280ba4d7, esp =
> 0xbfbfe3fc, ebp = 0xbfbfec78 ---
> 
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
===================================================================
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 = 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 == NULLVP) {
+	lvp = a->null_lowervp;
+	if (lvp == NULLVP) {
 		/* Should never happen */
 		int i; u_long *p;
 		printf("vp = %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 = lvp->v_usecount;
+	VI_UNLOCK(lvp);
+	if (refcnt < 1) {
 		int i; u_long *p;
 		printf("vp = %p, unref'ed lowervp\n", (void *)vp);
 		for (p = (u_long *) a, i = 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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