Hi Ted and the list,
     Here are 4 patches for trim support in ext4.
     Patch 1/4 is a fix for the 'len' overflow. As we have decided that 
we don't adjust start to s_first_data_block, this patch is still needed.
     Patch 2/4 is a speedup for trim in one group.
     Patch 3/4 adds trace points for the functions used in FITRIM.
     Patch 4/4 is a speedup for trim in the whole volume. For more 
details, please check the commit log.

Regards,
Tao