.

wcfs/__init__.py

@@ -260,6 +260,7 @@ def resync(wconn, at):
         assert f.headfsize <= headfsize     # head/file size ↑=
         assert headfsize % f.blksize == 0
         for mmap in f.mmaps:
+            print('  resync -> %s: unzero [%d:%d)' % (at, f.headfsize//f.blksize, headfsize//f.blksize))
             memunzero = mmap.mem[f.headfsize - mmap.blk_start*f.blksize :
                                  headfsize   - mmap.blk_start*f.blksize]
             if len(memunzero) > 0:
@@ -340,18 +341,20 @@ def _remmapblk(mmap, blk, at):
     f = mmap.file
     blkmem = mmap.mem[(blk-mmap.blk_start)*f.blksize:][:f.blksize]
     if at is None:
-        # head/file[blk >= size] -> Z
-        if blk*f.blksize >= f.headfsize:
-            mm.map_zero_into(blkmem)
-            return
-        # head/file[blk < size]  -> use the file
         fsfile = f.headf
     else:
         # TODO share @rev fd until wconn is resynced?
         fsfile = f.wconn._wc._open("@%s/bigfile/%s" % (h(at), h(f.foid)), "rb")
         defer(fsfile.close)
-        assert os.fstat(fsfile.fileno()).st_blksize == f.blksize  # FIXME assert
 
+    _ = os.fstat(fsfile.fileno())
+    assert _.st_blksize == f.blksize  # FIXME assert
+
+    # block is beyond file size - mmap with zeros   (assumes head/f size ↑=)
+    if (blk+1)*f.blksize > _.st_size:
+        mm.map_zero_into_ro(blkmem)
+    # block is inside file - mmap file data
+    else:
         mm.map_into_ro(blkmem, fsfile.fileno(), blk*f.blksize)
 
 

wcfs/wcfs_test.py

@@ -1765,12 +1765,12 @@ def test_wcfspy_virtmem():
     tm1.assertBlk(4, '')
     assert f.pinned == {2:at1, 3:at1}
 
-    # resync at1 -> at2:    #2 must unpin to @head
+    # resync at1 -> at2:    #2 must unpin to @head; #4 must stay as zero
     wconn.resync(at2)
     assert f.pinned == {3:at1}
     tm1.assertBlk(2, 'c2')
     tm1.assertBlk(3, 'd1')
-    tm1.assertBlk(3, '')
+    tm1.assertBlk(4, '')
 
     # resync at2 -> at3:    #3 must unpin to @head; #4 - start to read with data
     wconn.resync(at3)