lib/VolumeManager/LVM/thin/superblock.rb in manageiq-smartstate-0.1.4 vs lib/VolumeManager/LVM/thin/superblock.rb in manageiq-smartstate-0.1.5

@@ -77,38 +77,55 @@
 
     def device_block_offset(device_address)
       device_address % data_block_size
     end
 
-    # return array of tuples containing data volume addresses and lengths to
-    # read from them to read the specified device offset & length
+    # Return array of tuples device block ids, data block ids, addresses, and lengths to
+    # read from them to read the specified device offset & length.
+    #
+    # Note: data blocks may not amount to total requested length (if requesting
+    # data from unallocated space).
+    #
+    # @see DataMap#block?
     def device_to_data(device_id, pos, len)
-      dev_blk = device_block(pos)
-      dev_off = device_block_offset(pos)
+      dev_blk  = device_block(pos)
+      dev_off  = device_block_offset(pos)
+      data_map = data_mapping.map_for(device_id)
 
       total_len = 0
       data_blks = []
 
       num_data_blks = (len / data_block_size).to_i + 1
       0.upto(num_data_blks - 1) do |i|
-        data_blk = data_mapping.map_for(device_id).data_block(dev_blk + i)
+        current_blk = dev_blk + i
+        blk_len = 0
 
-        blk_start = data_blk * data_block_size
-        blk_len   = 0
+        if data_map.block?(current_blk)
+          data_blk = data_map.data_block(current_blk)
+          blk_start = data_blk * data_block_size
 
-        if i == 0
-          blk_start += dev_off
-          blk_len    = data_block_size - dev_off - 1
+          if i.zero?
+            blk_start += dev_off
+            blk_len    = data_block_size - dev_off - 1
 
-        elsif i == num_data_blks - 1
-          blk_len = len - total_len
+          elsif i == num_data_blks - 1
+            blk_len = len - total_len
 
+          else
+            blk_len = data_block_size
+          end
+
+          data_blks << [current_blk, data_blk, blk_start, blk_len]
+
+        # Missing block may be caused by trying to read beyond end of
+        # LVM device (too large pos or len):
         else
-          blk_len    = data_block_size
+          remaining  = (len - total_len)
+          blk_len    = remaining > data_block_size ? data_block_size : remaining
+          data_blks << [current_blk, nil, nil, blk_len]
         end
 
         total_len += blk_len
-        data_blks << [blk_start, blk_len]
       end
 
       data_blks
     end