vfs: expose files creation (birth) time

Motivation:
the new developments on the client side start to proper
handle files creation time, thus this is a good time for
nfs4j to support it as well.

Modification:
Introduce Stat#set/getBTime. Update NFS code to use btime if provided.

Result:
first steps to support of file creation time.

Acked-by: Paul Millar
Target: master

core/src/main/java/org/dcache/nfs/v4/OperationGETATTR.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009 - 2020 Deutsches Elektronen-Synchroton,
+ * Copyright (c) 2009 - 2022 Deutsches Elektronen-Synchroton,
  * Member of the Helmholtz Association, (DESY), HAMBURG, GERMANY
  *
  * This library is free software; you can redistribute it and/or modify
@@ -87,6 +87,7 @@
 import org.dcache.nfs.v4.xdr.GETATTR4resok;
 import org.dcache.nfs.v4.xdr.GETATTR4res;
 
+import org.dcache.nfs.vfs.Stat.StatAttribute;
 import org.dcache.oncrpc4j.xdr.XdrAble;
 import org.dcache.oncrpc4j.xdr.Xdr;
 import org.dcache.nfs.status.InvalException;
@@ -333,8 +334,9 @@ static Optional<? extends XdrAble> fattr2xdr(int fattr, VirtualFileSystem fs, In
             case nfs4_prot.FATTR4_TIME_BACKUP:
                 return Optional.empty();
             case nfs4_prot.FATTR4_TIME_CREATE:
-                fattr4_time_create ctime = new fattr4_time_create(stat.getCTime());
-                return Optional.of(ctime);
+                long btimeMillis = stat.isDefined(StatAttribute.BTIME) ? stat.getBTime() : stat.getCTime();
+                fattr4_time_create btime = new fattr4_time_create(btimeMillis);
+                return Optional.of(btime);
             case nfs4_prot.FATTR4_TIME_DELTA:
                 // one (1) second is a common value for time delta across nfs4 servers
                 return Optional.of(new fattr4_time_delta( new nfstime4(TimeUnit.SECONDS.toMillis(1))));

core/src/main/java/org/dcache/nfs/vfs/Stat.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009 - 2018 Deutsches Elektronen-Synchroton,
+ * Copyright (c) 2009 - 2022 Deutsches Elektronen-Synchroton,
  * Member of the Helmholtz Association, (DESY), HAMBURG, GERMANY
  *
  * This library is free software; you can redistribute it and/or modify
@@ -42,7 +42,8 @@ public enum StatAttribute {
         GENERATION,
         ATIME,
         MTIME,
-        CTIME
+        CTIME,
+        BTIME
     };
 
     private static final long serialVersionUID = 1L;
@@ -155,6 +156,7 @@ public static Type fromMode(int mode) {
     private long _atime;
     private long _mtime;
     private long _ctime;
+    private long _btime;
 
     public int getDev() {
         guard(StatAttribute.DEV);
@@ -266,6 +268,16 @@ public void setCTime(long ctime) {
         _ctime = ctime;
     }
 
+    public long getBTime() {
+        guard(StatAttribute.BTIME);
+        return _btime;
+    }
+
+    public void setBTime(long btime) {
+        define(StatAttribute.BTIME);
+        _ctime = btime;
+    }
+
     public long getFileId() {
         guard(StatAttribute.FILEID);
         return _fileid;