linux-kernel - [bug?] can't unmount filesystem after running "exportfs -u" -- dangling refcount?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Date:	Fri, 21 Mar 2014 10:37:44 -0600
From:	Chris Friesen <chris.friesen@...driver.com>
To:	<linux-kernel@...r.kernel.org>
Subject: [bug?] can't unmount filesystem after running "exportfs -u" -- dangling
 refcount?

I'm seeing some odd behaviour on an NFS server.

We're running 3.4.82 and have a drbd-replicated filesystem 
(active/standby) that is exported via NFS (explicitly v3, and 
/proc/fs/nfsd is mounted).

On a server switchover we take down the NFS server IP address, run 
"exportfs -u" on the exports, unmount the drbd filesystem, and then 
demote drbd from primary to secondary.

The problem we're seeing is that sometimes "exportfs -u" completes 
successfully but "umount" fails with an error that the filesystem is 
busy.  When this happens, "fuser" doesn't see any userspace users, which 
points at the kernel thinking it has a reference open.

When it's in the stuck state, manually running "exportfs -f" seems to 
resolve the issue so that "unmount" can run.

Are there any known issue in this area?

I'm not currently subscribed to the list, so please CC me on replies.

Thanks,
Chris
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/