.

include/wendelin/bigfile/file.h

@@ -129,7 +129,7 @@ struct bigfile_ops {
      *      virt_unlock()
      *
      * XXX mention VMA.mmap_overlay_server?
-     * XXX called under virtmem lock?
+     * called under virtmem lock
      *
      * NOTE blk and blklen are in blocks, not pages.
      *
@@ -142,14 +142,14 @@ struct bigfile_ops {
     // remmap_blk_read is called to remmap a block into vma again, after e.g.
     // RW dirty page was discarded.
     //
-    // XXX called under virtmem lock?
+    // called under virtmem lock.
     //
     // XXX error -> bug (must not fail)
     int (*remmap_blk_read) (VMA *vma, BigFile *file, blk_t blk);
 
     /* munmap is called when vma set up via mmap_setup_read is going to be unmapped.
      *
-     * XXX called under virtmem lock?
+     * called under virtmem lock.
      * Must not fail.
      */
     void (*munmap) (VMA *vma, BigFile *file);

wcfs/client/wcfs.cpp

@@ -259,6 +259,7 @@ error _Conn::__pin1(PinReq *req) {
         bool do_pin= true;
         error err;
         if (mmap->vma != nil) {
+            mmap->assertVMAOk();
             virt_lock();
             BigFileH *virt_fileh = mmap->vma->fileh;
             TODO (mmap->fileh->blksize != virt_fileh->ramh->ram->pagesize);
@@ -459,6 +460,7 @@ pair<Mapping, error> _FileH::mmap(int64_t blk_start, int64_t blk_len, VMA *vma)
         vma->mmap_overlay_server = mmap._ptr();
         vma->addr_start = (uintptr_t)mmap->mem_start;
         vma->addr_stop  = (uintptr_t)mmap->mem_stop;
+        mmap.assertVMAOk(); // just in case
     }
 
     f._mmaps.push_back(mmap);   // TODO keep f._mmaps ↑blk_start
@@ -481,6 +483,12 @@ error _Mapping::unmap() {
     // XXX make sure mmap cannot be XXX
 
     if (mmap->vma != nil) {
+        // must be called under virtmem lock fo virtmem-intergrated case (?)
+        mmap->assertVMAOk();
+        VMA *vma = mmap->vma;
+        vma->mmap_overlay_server = NULL;
+        vma->addr_start = 0;
+        vma->addr_stop  = 0;
     }
 
     error err = mm::unmap(mmap->mem_start, mmap->mem_stop - mmap->mem_start);
@@ -728,6 +736,22 @@ void _Mapping::decref() {
         delete this;
 }
 
+// assertVMAOk() verifies that mmap and vma are related to each other and cover
+// exactly the same virtual memory rane.
+//
+// It panics if mmap and vma do not exactly relate to each other or cover
+// different virtual memory range.
+void _Mapping::assertVMAOk() {
+    _Mapping* mmap = this;
+    VMA *vma = mmap.vma;
+
+    if (!(vma->mmap_overlay_server == mmap._ptr()))
+        panic("BUG: mmap and vma do not link to each other");
+    if (!(vma->addr_start == mmap->mem_start && vma->addr_stop == mmap->mem_stop))
+        panic("BUG: mmap and vma cover different virtual memory ranges");
+
+    // verified ok
+}
 
 dict<int64_t, zodb::Tid> _tfileh_pinned(FileH fileh) {
     return fileh->_pinned;