.

wcfs/internal/wcfs_virtmem.cpp

@@ -239,7 +239,7 @@ void Conn::_pin1(SrvReq *req) {
 // at=None means unpin to head/ .   XXX -> C
 // NOTE this does not check wrt virtmem already mapped blk as RW.
 error _Mapping::_remmapblk(int64_t blk, Tid at) {
-    // XXX err context?
+    // XXX err context? blk #<blk> @<at>
     _Mapping *mmap = this;
 
     ASSERT(mmap->blk_start <= blk && blk < mmap->blk_stop());
@@ -271,16 +271,22 @@ error _Mapping::_remmapblk(int64_t blk, Tid at) {
         return err;
     ASSERT(st.st_blksize == f->blksize);  // FIXME assert
 
-#if 0
-    // block is beyond file size - mmap with zeros   (assumes head/f size ↑=)
+    // block is beyond file size - mmap with zeros - else access to memory
+    // after file.size will raise SIGBUS. (assumes head/f size ↑=)
     if ((blk+1)*f->blksize > st.st_size) {
         mm.map_zero_into_ro(blkmem);    // XXX err
     }
     // block is inside file - mmap file data
     else {
-        mm.map_into_ro(blkmem, fsfile.fd, blk*f->blksize);  // XXX err
+        mm.map_into_ro(blkmem, fsfile.fd(), blk*f->blksize);  // XXX err
+
+        err = mmap_into_ro(blkmem, f->blksize, fsfile, blk*f->blksize);
+
+        err = fsfile.mmapfix(blkmem, f->blksize, PROT_READ, MAP_SHARED, blk*f->blksize);
+
+        mmap(blkmem, f->blksize, PROT_READ, MAP_FIXED | MAP_SHARED,
+                fsfile.fd(), blk*f->blksize);
     }
-#endif
 
     return nil;
 }
@@ -308,3 +314,14 @@ tuple<os::File, error> WCFS::_open(const string &path, int flags) {
 string h(uint64_t v) {
     return fmt::sprintf("%016x", v);
 }
+
+// map_into_ro memory-maps f.fd[offset +size) as read-only into [addr +size).
+// The mapping is created with MAP_SHARED.
+error mmap_into_ro(void *addr, size_t size, const File &f. off_t offset) {
+    void *addr2;
+
+    addr2 = mmap(blkmem, size, PROT_READ, MAP_FIXED | MAP_SHARED, f.fd(), offset);
+    // XXX -> err
+
+    // XXX assert addr2 == addr
+}