.

bigfile/virtmem.c

@@ -474,7 +474,6 @@ void fileh_dirty_discard(BigFileH *fileh)
         pagemap_del(&fileh->pagemap, page->f_pgoffset);
         page_drop_memory(page);
         page_del(page);
-        // XXX wcfs: remmap page(s) to base file
     }
 
     BUG_ON(!list_empty(&fileh->dirty_pages));
@@ -1063,9 +1062,19 @@ static void vma_page_ensure_unmapped(VMA *vma, Page *page)
     if (!vma_page_ismapped(vma, page))
         return;
 
-    /* mmap empty PROT_NONE address space instead of page memory */
-    // XXX overlay: remmap to base image
-    mem_xvalloc(vma_page_addr(vma, page), page_size(page));
+    if (vma->mmap_overlay) {
+        /* wcfs: remmap readonly to base image */
+        BigFile *file = vma->fileh->file;
+        int err;
+
+        TODO (file->blksize != page_size(page));
+        err = file->file_ops->remmap_blk_read(file, page->f_pgoffset /* =blk */, vma);
+        BUG_ON(err); /* must not fail */
+    }
+    else {
+        /* !wcfs: mmap empty PROT_NONE address space instead of page memory */
+        mem_xvalloc(vma_page_addr(vma, page), page_size(page));
+    }
 
     bitmap_clear_bit(vma->page_ismappedv, page->f_pgoffset - vma->f_pgoffset);
     page_decref(page);

include/wendelin/bigfile/file.h

@@ -72,6 +72,11 @@ struct bigfile_ops {
     int  (*storeblk) (BigFile *file, blk_t blk, const void *buf);
 
 
+    // - mmap_setup_read(file[blk +blklen), vma)    setup initial read-only mmap to serve vma
+    // - remmap_blk_read(file[blk], vma)            remmap blk into vma again, after e.g.
+    //                                              RW dirty page was discarded
+    // - munmap(vma)                before VMA is unmapped
+
     /* mmap_setup_read is called to setup new read-only mapping of file[blk +blklen).
      *
      * The mapping will be used as the base read-only layer for vma.
@@ -82,12 +87,14 @@ struct bigfile_ops {
      * @addr    NULL - mmap at anywhere,    !NULL - mmap exactly at addr.
      * @return  !NULL - mapped there,       NULL - error.
      */
-//    void* (*mmap_read) (BigFile *file, void *addr, blk_t blk, size_t blklen);
     void* (*mmap_setup_read) (BigFile *file, blk_t blk, size_t blklen, VMA *vma);
 
-    // - mmap_setup_read(vma)       setup initial read-only mmap
-    // - mresync(vma, was_dirtyv)   forget RW dirty pages -> mmap them back read-only to file data
-    // - munmap(vma)                before VMA is unmapped
+
+    // XXX
+    // XXX error -> bug (must not fail)
+    int (*remmap_blk_read) (BigFile *file, blk_t, VMA *vma);
+
+
 
 
     /* release is called to release resources associated with file.

include/wendelin/bigfile/ram.h

@@ -30,7 +30,7 @@
  * - need to "unload" non-dirty pages to free place for requested new data (reclaim)
  *
  * - need to be able to map a page into several places (to support
- *   overlapping-in-file mappings done not neccessarily adjacent-in-time to
+ *   overlapping-in-file mappings done not necessarily adjacent-in-time to
  *   each other - there is no guarantee mapping them adjacent in address space
  *   is possible)
  *