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must still have a lock owner active which the client thinks is no longer
active.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, 2 insertions, 4 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 8286edd6062d..3fea7aa1366f 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -997,8 +997,8 @@ struct nfs_server *nfs_alloc_server(void)
 	init_waitqueue_head(&server->write_congestion_wait);
 	atomic_long_set(&server->writeback, 0);
 
-	ida_init(&server->openowner_id);
-	ida_init(&server->lockowner_id);
+	atomic64_set(&server->owner_ctr, 0);
+
 	pnfs_init_server(server);
 	rpc_init_wait_queue(&server->uoc_rpcwaitq, "NFS UOC");
 
@@ -1037,8 +1037,6 @@ void nfs_free_server(struct nfs_server *server)
 	}
 	ida_free(&s_sysfs_ids, server->s_sysfs_id);
 
-	ida_destroy(&server->lockowner_id);
-	ida_destroy(&server->openowner_id);
 	put_cred(server->cred);
 	nfs_release_automount_timer();
 	call_rcu(&server->rcu, delayed_free);