ext3-get-blocks support caused ~20% degrade in Sequential read
performance (tiobench). Problem is with marking the buffer boundary
so IO can be submitted right away. Here is the patch to fix it.

  2.6.18-rc6:
  -----------
  # ./iotest
  1048576+0 records in
  1048576+0 records out
  4294967296 bytes (4.3 GB) copied, 75.2726 seconds, 57.1 MB/s

  real    1m15.285s
  user    0m0.276s
  sys     0m3.884s

  2.6.18-rc6 + fix:
  -----------------
  [root@elm3a241 ~]# ./iotest
  1048576+0 records in
  1048576+0 records out
  4294967296 bytes (4.3 GB) copied, 62.9356 seconds, 68.2 MB/s

The boundary block check in ext3_get_blocks_handle needs to be adjusted
against the count of blocks mapped in this call, now that it can map
more than one block.

Signed-off-by: Suparna Bhattacharya <suparna@in.ibm.com>
Tested-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>