pnfs: Don't release the sequence slot until we've processed layoutget on open

If the server recalls the layout that was just handed out, we risk hitting
a race as described in RFC5661 Section 2.10.6.3 unless we ensure that we
release the sequence slot after processing the LAYOUTGET operation that
was sent as part of the OPEN compound.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/nfs4proc.c

@@ -2789,7 +2789,7 @@ static int _nfs4_open_and_get_state(struct nfs4_opendata *opendata,
 	if (ret != 0)
 		goto out;
 
-	state = nfs4_opendata_to_nfs4_state(opendata);
+	state = _nfs4_opendata_to_nfs4_state(opendata);
 	ret = PTR_ERR(state);
 	if (IS_ERR(state))
 		goto out;
@@ -2828,6 +2828,7 @@ static int _nfs4_open_and_get_state(struct nfs4_opendata *opendata,
 	}
 
 out:
+	nfs4_sequence_free_slot(&opendata->o_res.seq_res);
 	return ret;
 }