nfsd4: cleanup handling of nfsv4.0 closed stateid's

Closed stateid's are kept around a little while to handle close replays
in the 4.0 case.  So we stash them in the last-used stateid in the
oo_last_closed_stateid field of the open owner.  We can free that in
encode_seqid_op_tail once the seqid on the open owner is next
incremented.  But we don't want to do that on the close itself; so we
set NFS4_OO_PURGE_CLOSE flag set on the open owner, skip freeing it the
first time through encode_seqid_op_tail, then when we see that flag set
next time we free it.

This is unnecessarily baroque.

Instead, just move the logic that increments the seqid out of the xdr
code and into the operation code itself.

The justification given for the current placement is that we need to
wait till the last minute to be sure we know whether the status is a
sequence-id-mutating error or not, but examination of the code shows
that can't actually happen.

Reported-by: Yanchuan Nian <ycnian@gmail.com>
Tested-by: Yanchuan Nian <ycnian@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 40e05e6..3b271d2 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -623,6 +623,7 @@
 		struct nfsd4_compound_state *, struct nfsd4_test_stateid *test_stateid);
 extern __be32 nfsd4_free_stateid(struct svc_rqst *rqstp,
 		struct nfsd4_compound_state *, struct nfsd4_free_stateid *free_stateid);
+extern void nfsd4_bump_seqid(struct nfsd4_compound_state *, __be32 nfserr);
 #endif
 
 /*