nfs: remove transfer from the door list if pool selection failed

Motivation:
As pNFS layouts are independent of file open, they are invalidated only
when layout return is issued. The door logic creates a transfer, adds
transfer into transfers list and then performs namespace lookup, pool
selection and starting a mover. In cases, when pool selection fails due
to stage protection or an attempt to overwrite, the layout get will
return "permission deny", thus layout return will never be issued and
transfer will stay in the door forever.

Modification:
Update layoutGet error handling such that on permission deny error pool
less transfers will be removed. An unexpected conditions are logged.

Result:
orphan transfers like "WriteTransfer null@N/A," are removed when it's
safe.

Acked-by: Marina Sahakyan
Target: master, 12.0, 11.2
Require-book: no
Require-notes: yes

Author: kofemann

modules/dcache-nfs/src/main/java/org/dcache/chimera/nfsv41/door/NFSv41Door.java

@@ -802,6 +802,7 @@ public Layout layoutGet(CompoundContext context, LAYOUTGET4args args)
         final stateid4 stateid = Stateids.getCurrentStateidIfNeeded(context, args.loga_stateid);
 
         LayoutDriver layoutDriver = getLayoutDriver(layoutType);
+        NfsTransfer transfer = null;
 
         final NFS4Client client;
         if (context.getMinorversion() == 0) {
@@ -835,7 +836,7 @@ public Layout layoutGet(CompoundContext context, LAYOUTGET4args args)
                     throw new LayoutUnavailableException("special DOT file");
                 }
 
-                NfsTransfer transfer = layoutStateid != null ? _transfers.get(layoutStateid) : null;
+                transfer = layoutStateid != null ? _transfers.get(layoutStateid) : null;
                 if (transfer == null) {
                     Transfer.initSession(false, false);
                     NDC.push(pnfsId.toString());
@@ -911,6 +912,20 @@ public Layout layoutGet(CompoundContext context, LAYOUTGET4args args)
              */
             client.releaseState(stateid);
             throw new StaleException("File is removed", e);
+        } catch (PermissionDeniedCacheException e) {
+            // pool selection due to stage protection or an overwrite attempt of an existing file.
+            if (transfer.getPool() == null) {
+                // safe to forget
+                _log.error("Removing pool-less transfer for client {} for file {}: {}",
+                      toAddrString(context.getRemoteSocketAddress().getAddress()),
+                      transfer.getPnfsId(), e.getMessage());
+                _transfers.remove(transfer.getStateid().stateid());
+            } else {
+                // should never happen
+                _log.error("Report to support@dcache.org: Unexpected permission denied for transfer {} with assigned pool: {}", transfer, e.toString());
+            }
+
+            throw new PermException(e.getMessage(), e);
         } catch (CacheException | ChimeraFsException | TimeoutException | ExecutionException e) {
             throw asNfsException(e, LayoutTryLaterException.class);
         } catch (InterruptedException e) {
@@ -1526,7 +1541,7 @@ deviceid4[] selectDataServers(long timeout) throws
                  * allow writes only into new files
                  */
                 if (!attr.getStorageInfo().isCreatedOnly()) {
-                    throw new PermException("Can't modify existing file");
+                    throw new PermissionDeniedCacheException("Can't modify existing file");
                 }
 
                 // REVISIT: this have to go into Transfer class.