6253 F_GETLK doesn't always return lock owner
The F_GETLK fcntl doesn't return the offending lock if there is a read lock
on the file, a waiting write lock, and a read lock is requested.
The write lock blocks the locking request, but without this patch isn't
returned by GETLK.

*** 2097,2106 ****
--- 2097,2125 ----
                          }
                          lock = lock->l_next;
                  } while (lock->l_vnode == vp);
          }
  
+         if (blocker == NULL && request->l_flock.l_type == F_RDLCK) {
+                 /*
+                  * No active lock is blocking this request, but if a read
+                  * lock is requested, it may also get blocked by a waiting
+                  * writer. So search all sleeping locks and see if there is
+                  * a writer waiting.
+                  */
+                 SET_LOCK_TO_FIRST_SLEEP_VP(gp, lock, vp);
+                 if (lock) {
+                         do {
+                                 if (BLOCKS(lock, request)) {
+                                         blocker = lock;
+                                         break;
+                                 }
+                                 lock = lock->l_next;
+                         } while (lock->l_vnode == vp);
+                 }
+         }
+ 
          if (blocker) {
                  report_blocker(blocker, request);
          } else
                  request->l_flock.l_type = F_UNLCK;
  }