FreeBSD: don't verify recycled vnode for zfs control directory

Under certain loads, the following panic is hit:

    panic: VERIFY3(vrecycle(vp) == 1) failed (0 == 1)
    cpuid = 17
    KDB: stack backtrace:
    #0 0xffffffff805e29c5 at kdb_backtrace+0x65
    #1 0xffffffff8059620f at vpanic+0x17f
    #2 0xffffffff81a27f4a at spl_panic+0x3a
    #3 0xffffffff81a3a4d0 at zfsctl_snapshot_inactive+0x40
    openzfs#4 0xffffffff8066fdee at vinactivef+0xde
    openzfs#5 0xffffffff80670b8a at vgonel+0x1ea
    openzfs#6 0xffffffff806711e1 at vgone+0x31
    openzfs#7 0xffffffff8065fa0d at vfs_hash_insert+0x26d
    openzfs#8 0xffffffff81a39069 at sfs_vgetx+0x149
    openzfs#9 0xffffffff81a39c54 at zfsctl_snapdir_lookup+0x1e4
    openzfs#10 0xffffffff80661c2c at lookup+0x45c
    openzfs#11 0xffffffff80660e59 at namei+0x259
    openzfs#12 0xffffffff8067e3d3 at kern_statat+0xf3
    openzfs#13 0xffffffff8067eacf at sys_fstatat+0x2f
    openzfs#14 0xffffffff808b5ecc at amd64_syscall+0x10c
    openzfs#15 0xffffffff8088f07b at fast_syscall_common+0xf8

A race condition can occur when allocating a new vnode and adding that
vnode to the vfs hash. If the newly created vnode loses the race when
being inserted into the vfs hash, it will not be recycled as its
usecount is greater than zero, hitting the above assertion.

Fix this by dropping the assertion.

FreeBSD-issue: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=252700

Signed-off-by:  Rob Wing <[email protected]>
Sponsored-by:   rsync.net
Sponsored-by:   Klara, Inc.

module/os/freebsd/zfs/zfs_ctldir.c

@@ -1153,7 +1153,7 @@ zfsctl_snapshot_inactive(struct vop_inactive_args *ap)
 {
 	vnode_t *vp = ap->a_vp;
 
-	VERIFY3S(vrecycle(vp), ==, 1);
+	vrecycle(vp);
 	return (0);
 }
 
@@ -1237,6 +1237,8 @@ static struct vop_vector zfsctl_ops_snapshot = {
 #if __FreeBSD_version >= 1300121
 	.vop_fplookup_vexec =	VOP_EAGAIN,
 #endif
+	.vop_open =		zfsctl_common_open,
+	.vop_close =		zfsctl_common_close,
 	.vop_inactive =		zfsctl_snapshot_inactive,
 #if __FreeBSD_version >= 1300045
 	.vop_need_inactive = vop_stdneed_inactive,