Rename fd_reference to more suggestive fd_incref.
(Fd_reference sounds like it might just return the ref count.)

defs.h

@@ -84,7 +84,7 @@ struct fd * fd_alloc();
 void fd_close(struct fd *);
 int fd_read(struct fd *fd, char *addr, int n);
 int fd_write(struct fd *fd, char *addr, int n);
-void fd_reference(struct fd *fd);
+void fd_incref(struct fd *fd);
 
 // ide.c
 void ide_init(void);

fd.c

@@ -99,7 +99,7 @@ fd_close(struct fd *fd)
 }
 
 void
-fd_reference(struct fd *fd)
+fd_incref(struct fd *fd)
 {
   acquire(&fd_table_lock);
   if(fd->count < 1 || fd->type == FD_CLOSED)

proc.c

@@ -118,7 +118,7 @@ copyproc(struct proc* p)
   for(i = 0; i < NOFILE; i++){
     np->fds[i] = p->fds[i];
     if(np->fds[i])
-      fd_reference(np->fds[i]);
+      fd_incref(np->fds[i]);
   }
 
   return np;