nfs: simplify and guarantee owner uniqueness.

I have evidence of an Linux NFS client getting NFS4ERR_BAD_SEQID to a
v4.0 LOCK request to a Linux server (which had fixed the problem with
RELEASE_LOCKOWNER bug fixed).
The LOCK request presented a "new" lock owner so there are two seq ids
in the request: that for the open file, and that for the new lock.
Given the context I am confident that the new lock owner was reported to
have the wrong seqid.  As lock owner identifiers are reused, the server
must still have a lock owner active which the client thinks is no longer
active.

I wasn't able to determine a root-cause but the simplest fix seems to be
to ensure lock owners are always unique much as open owners are (thanks
to a time stamp).  The easiest way to ensure uniqueness is with a 64bit
counter for each server.  That will never cycle (if updated once a
nanosecond the last 584 years.  A single NFS server would not handle
open/lock requests nearly that fast, and a Linux node is unlikely to
have an uptime approaching that).

This patch removes the 2 ida and instead uses a per-server
atomic64_t to provide uniqueness.

Note that the lock owner already encodes the id as 64 bits even though
it is a 32bit value.  So changing to a 64bit value does not change the
encoding of the lock owner.  The open owner encoding is now 4 bytes
larger.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 7704a4509676..88bcbcba1381 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -1424,12 +1424,12 @@ static inline void encode_openhdr(struct xdr_stream *xdr, const struct nfs_opena
  */
 	encode_nfs4_seqid(xdr, arg->seqid);
 	encode_share_access(xdr, arg->share_access);
-	p = reserve_space(xdr, 36);
+	p = reserve_space(xdr, 40);
 	p = xdr_encode_hyper(p, arg->clientid);
-	*p++ = cpu_to_be32(24);
+	*p++ = cpu_to_be32(28);
 	p = xdr_encode_opaque_fixed(p, "open id:", 8);
 	*p++ = cpu_to_be32(arg->server->s_dev);
-	*p++ = cpu_to_be32(arg->id.uniquifier);
+	p = xdr_encode_hyper(p, arg->id.uniquifier);
 	xdr_encode_hyper(p, arg->id.create_time);
 }