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must still have a lock owner active which the client thinks is no longer
active.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, 13 deletions

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 30aba1dedaba..2ef656ca6371 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -501,11 +501,7 @@ nfs4_alloc_state_owner(struct nfs_server *server,
 	sp = kzalloc(sizeof(*sp), gfp_flags);
 	if (!sp)
 		return NULL;
-	sp->so_seqid.owner_id = ida_alloc(&server->openowner_id, gfp_flags);
-	if (sp->so_seqid.owner_id < 0) {
-		kfree(sp);
-		return NULL;
-	}
+	sp->so_seqid.owner_id = atomic64_inc_return(&server->owner_ctr);
 	sp->so_server = server;
 	sp->so_cred = get_cred(cred);
 	spin_lock_init(&sp->so_lock);
@@ -536,7 +532,6 @@ static void nfs4_free_state_owner(struct nfs4_state_owner *sp)
 {
 	nfs4_destroy_seqid_counter(&sp->so_seqid);
 	put_cred(sp->so_cred);
-	ida_free(&sp->so_server->openowner_id, sp->so_seqid.owner_id);
 	kfree(sp);
 }
 
@@ -879,19 +874,13 @@ static struct nfs4_lock_state *nfs4_alloc_lock_state(struct nfs4_state *state, f
 	refcount_set(&lsp->ls_count, 1);
 	lsp->ls_state = state;
 	lsp->ls_owner = owner;
-	lsp->ls_seqid.owner_id = ida_alloc(&server->lockowner_id, GFP_KERNEL_ACCOUNT);
-	if (lsp->ls_seqid.owner_id < 0)
-		goto out_free;
+	lsp->ls_seqid.owner_id = atomic64_inc_return(&server->owner_ctr);
 	INIT_LIST_HEAD(&lsp->ls_locks);
 	return lsp;
-out_free:
-	kfree(lsp);
-	return NULL;
 }
 
 void nfs4_free_lock_state(struct nfs_server *server, struct nfs4_lock_state *lsp)
 {
-	ida_free(&server->lockowner_id, lsp->ls_seqid.owner_id);
 	nfs4_destroy_seqid_counter(&lsp->ls_seqid);
 	kfree(lsp);
 }