.

include/wendelin/bigfile/file.h

@@ -99,6 +99,7 @@ struct bigfile_ops {
      *      }
      *      virt_unlock()
      *
+     * XXX mention VMA.mmap_overlay_server?
      * XXX called under virtmem lock?
      *
      * NOTE blk and blklen are in blocks, not pages.

include/wendelin/bigfile/virtmem.h

@@ -169,6 +169,16 @@ struct VMA {
 
     /* whether corresponding to pgoffset-f_offset page is mapped in this VMA */
     bitmap      *page_ismappedv;    /* len ~ Δaddr / pagesize */
+
+    /* BigFile-specific field used when VMA was created from fileh opened with
+     * MMAP_OVERLAY flag. bigfile_ops.mmap_setup_read initializes this to
+     * object pointer specific to serving created base overlay mapping.
+     *
+     * For example WCFS uses this to link VMA -> wcfs.Mapping to know which
+     * wcfs-specific mapping is serving particular virtmem VMA.
+     *
+     * NULL for VMAs created from under DONT_MMAP_OVERLAY fileh. */
+    void        *mmap_overlay_server;
 };