Breaking up a bvec in a bio for reading more than 512

Hi All,
   I am getting a request with bvec->bv_len > 512. Now, the
information to be read is scattered across the entire disk in 512
chunks. So that, information on disk can be : sector 8, sector 100,
sector 9.
 Now if i get a request to read with the bvec->bv_len > 512 i need to
pull in the information from
multiple places on disk since the data is not sequentially located.
 I tried to look at the linux source code because i think raid must be
doing it all the time. (eg : on disk 1 we may be storing sector 6 and
on disk 2 we may be storing sector 7 and so on).
  However, i have not really got any useful information from it. Also
scouring through articles on
google has not helped much.
   I am hoping somebody points me in the right direction.

Thanks in advance,
Neha