fixing an unsafe usage of integer disps[] (romio321 gpfs)

[markalle]

There are a couple MPI_Alltoallv calls in ad_gpfs_aggrs.c where the
send/recv data comes from places like req[r].lens, and the send
buffer and send displacements for example were being calculated as
sbuf = pick one of the reqs: req[bottom].lens
sdisps[r] = req[r].lens - req[bottom].lens
which might be okay if the .lens was data inside of req[] so they'd
all be close to each other. But each .lens field is just a pointer
that's malloced, so those addresses can be all over the place, so the
integer-sized sdisps[] isn't safe.

I changed it to have a new extra array sbuf and rbuf for those two
Alltoallv calls, and copied the data into the sbuf from the same
locations it used to be setting up the sdisps[] at, and after the
Alltoallv I copy the data out of the new rbuf into the same
locations it used to be setting up the rdisps[] at.

For what it's worth I was able to get this to fail -np 2 on a GPFS
filesystem with hints romio_cb_write enable. I didn't whittle the
test down to something small, but it was failing in an
MPI_File_write_all call.

Signed-off-by: Mark Allen markalle@us.ibm.com
(cherry picked from commit d85cac8)