From: Chuck Lever <chuck.lever@oracle.com>
To: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: global openowner_id and lockowner_id
Date: Thu, 12 Apr 2012 11:42:13 -0400 [thread overview]
Message-ID: <58E57AF8-1636-4017-93C0-8520488ED866@oracle.com> (raw)
Hi-
Changing the SETCLIENTID boot verifier so it is global for the whole client exposes a problem with how we allocate state owners.
A quick umount / mount sequence destroys all state on the client. But since the client now always uses the same boot verifier and nfs_client_id4 string, the server no longer recognizes a client reboot. FOr a fresh mount, the client may perform a SETCLIENTID, but it is treated as a callback update (state is not purged) if the client's lease has not yet expired.
Our state owners are generated from a pair of ida structures in the nfs_server for that mount. They always start from zero after a mount operation. Likewise, the sequence IDs for these state owners are also reset by umount / mount. Note that each mount point gets a fresh nfs_server, so these structures are not retained across umount / mount.
This means umount / mount with no lease expiry starts to re-play state owners with reset sequence IDs. Servers don't really care for that behavior. I have a test case that reliably gets a BAD_SEQID error from a server after a quick umount / mount followed by a single file creation.
Now that we are about to switch to using more-or-less global SETCLIENTID boot verifiers, it seems to me that we really want a global openowner_id and lockowner_id as well.
The performance impact of such a change might be acceptable because we cache and reuse state owners now.
Thoughts?
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
next reply other threads:[~2012-04-12 15:42 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-12 15:42 Chuck Lever [this message]
2012-04-12 15:50 ` global openowner_id and lockowner_id Myklebust, Trond
2012-04-12 15:54 ` Chuck Lever
2012-04-12 15:58 ` Myklebust, Trond
2012-04-12 16:05 ` Chuck Lever
2012-04-12 17:32 ` Myklebust, Trond
2012-04-12 17:07 ` J. Bruce Fields
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