kern/124899: [patch] Reboot hangs after ZFS snapshot directory lookup

[Masakazu Asama]

>Number:         124899
>Category:       kern
>Synopsis:       [patch] Reboot hangs after ZFS snapshot directory lookup
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Jun 23 06:20:01 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator:     Masakazu Asama
>Release:        FreeBSD 7.0-STABLE (GENERIC)
>Organization:
Ginzado Co., Ltd.
>Environment:
FreeBSD xxx 7.0-STABLE FreeBSD 7.0-STABLE #1: Sat Jun 21 17:27:55 JST 2008     root at xxx:/usr/obj/usr/src/sys/GENERIC  amd64
>Description:
Reboot hangs after ZFS snapshot directory lookup.

In zfsctl_snapdir_lookup(zfs_ctldir.c) line at 681, macro ZFS_ENTER called, but ZFS_EXIT missing case exists.

When unmounting ZFS snapshot directory, zfs_umount(zfs_vfsops.c) line at 737 going infinit loop, because zfsvfs_t->z_op_cnt never to zero.

>How-To-Repeat:
[root at srv2 ~]# zpool create tank da0s1d
[root at srv2 ~]# zfs create tank/vol01
[root at srv2 ~]# zfs snapshot tank/vol01 at snap01
[root at srv2 ~]# df
Filesystem  1K-blocks    Used   Avail Capacity  Mounted on
/dev/da0s1a   5077038 3983846  687030    85%    /
devfs               1       1       0   100%    /dev
tank          2047872     128 2047744     0%    /tank
tank/vol01    2047872     128 2047744     0%    /tank/vol01
[root at srv2 ~]# ls /tank/vol01/.zfs/snapshot/snap01
[root at srv2 ~]# df
Filesystem        1K-blocks    Used   Avail Capacity  Mounted on
/dev/da0s1a         5077038 3983846  687030    85%    /
devfs                     1       1       0   100%    /dev
tank                2047872     128 2047744     0%    /tank
tank/vol01          2047872     128 2047744     0%    /tank/vol01
tank/vol01 at snap01   2047872     128 2047744     0%    /tank/vol01/.zfs/snapshot/snap01
[root at srv2 ~]# cd /
[root at srv2 /]# shutdown -r now
hangs...

>Fix:
Apply the patch.


Patch attached with submission follows:

--- /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c.orig	2008-04-17 10:23:33.000000000 +0900
+++ /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c	2008-06-24 23:06:00.000000000 +0900
@@ -734,6 +734,7 @@
 	if (err == 0)
 		vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY, curthread);
 	mutex_exit(&sdp->sd_lock);
+	ZFS_EXIT(zfsvfs);
 
 	/*
 	 * If we had an error, drop our hold on the vnode and


>Release-Note:
>Audit-Trail:
>Unformatted: