I see the following challenges with bio-chained approach.
1. partitioned device:
We need to add the code which iterates over all bios and adjusts
the sectors offsets.
2. dm/stacked device:
We need to make major changes in dm, such as allocating cloned
bios, IO splits, IO offset mappings. All of which need to
iterate over chained BIOs.
Overall with chained BIOs we need to add a special handling only for copy
to iterate over chained BIOs and do the same thing which is being done
for single BIO at present.
Or am I missing something here ?