.

bigfile/virtmem.c

@@ -226,6 +226,7 @@ int fileh_mmap(VMA *vma, BigFileH *fileh, pgoff_t pgoffset, pgoff_t pglen)
         goto fail;
 
     /* allocate address space somewhere */
+    // XXX overlay: -> mmap(base, READ)
     addr = mem_valloc(NULL, len);
     if (!addr)
         goto fail;
@@ -382,6 +383,8 @@ int fileh_dirty_writeout(BigFileH *fileh, enum WriteoutFlags flags)
         }
 
         /* page.state -> PAGE_LOADED and correct mappings RW -> R */
+        // XXX adjust(wcfs): just remmap base file? (but it does not yet have stored changes)
+        // XXX -> vma_remove_readonly_overlay()?
         if (flags & WRITEOUT_MARKSTORED) {
             page->state = PAGE_LOADED;
             list_del_init(&page->in_dirty);
@@ -588,6 +591,8 @@ VMFaultResult vma_on_pagefault(VMA *vma, uintptr_t addr, int write)
 
     /* continuing on_pagefault() - see (1) there ... */
 
+    // XXX overlay: assert write
+
     /* (2) vma, addr -> fileh, pagen    ;idx of fileh page covering addr */
     fileh = vma->fileh;
     pagen = vma_addr_fpgoffset(vma, addr);
@@ -595,6 +600,8 @@ VMFaultResult vma_on_pagefault(VMA *vma, uintptr_t addr, int write)
     /* (3) fileh, pagen -> page  (via pagemap) */
     page = pagemap_get(&fileh->pagemap, pagen);
 
+    // XXX overlay: assert !page
+
     /* (4) no page found - allocate new from ram */
     while (!page) {
         page = ramh_alloc_page(fileh->ramh, pagen);
@@ -663,6 +670,9 @@ VMFaultResult vma_on_pagefault(VMA *vma, uintptr_t addr, int write)
         pageram = page_mmap(page, NULL, PROT_READ | PROT_WRITE);
         TODO(!pageram); // XXX err
 
+        // XXX overlay: copy data from base image, page.state=DIRTY
+        // XXX overlay: goto inject_page
+
         /* loadblk() -> pageram memory */
         blk = page->f_pgoffset;     // NOTE because blksize = pagesize
 
@@ -732,6 +742,7 @@ VMFaultResult vma_on_pagefault(VMA *vma, uintptr_t addr, int write)
         return VM_RETRY;
     }
 
+inject_page:
     /* (6) page data ready. Mmap it atomically into vma address space, or mprotect
      * appropriately if it was already mmaped. */
     int prot = PROT_READ;
@@ -741,6 +752,9 @@ VMFaultResult vma_on_pagefault(VMA *vma, uintptr_t addr, int write)
         newstate = PAGE_DIRTY;
     }
 
+    // XXX overlay: assert !vma->page_ismappedv[blk]
+    // XXX overlay: mmap page to all vma of this fileh.
+
     if (!bitmap_test_bit(vma->page_ismappedv, page->f_pgoffset - vma->f_pgoffset)) {
         // XXX err
         page_mmap(page, vma_page_addr(vma, page), prot);
@@ -939,6 +953,7 @@ static void vma_page_ensure_unmapped(VMA *vma, Page *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));
 
     bitmap_clear_bit(vma->page_ismappedv, page->f_pgoffset - vma->f_pgoffset);

include/wendelin/bigfile/virtmem.h

@@ -154,6 +154,10 @@ struct VMA {
  */
 int fileh_open(BigFileH *fileh, BigFile *file, RAM *ram);
 
+// XXX + fileh_open_overlay(fileh, file, base, ram) ?
+// here base is glued data from head/bigfile/file + revX/bigfile/file overwrites.
+// file will be used only to storeblk (loadblk=BUG).
+
 
 /* close fileh
  *

wcfs/wcfs.go

@@ -1621,6 +1621,8 @@ func main() {
 	go root.zwatcher(ctx)
 
 	// TODO handle autoexit
+	// (exit when kernel forgets all our inodes - wcfs.py keeps .wcfs/zurl
+	//  opened, so when all inodes has been forgotten - we know all wcfs.py clients exited)
 	_ = autoexit
 
 	// serve client requests