Currently we allocate rx buffers in a single contiguous buffers
for headers (iser and iscsi) and data trailer. This means
that most likely the data starting offset is aligned to 76
bytes (size of both headers).
This worked fine for years, but at some point this broke.
To fix this, we should avoid passing unaligned buffers for
I/O.
That is a bit vauge - what suddenly broke it?
Somewhere around the multipage bvec work that Ming did. The issue was
that brd assumed a 512 aligned page vector. IIRC the discussion settled
that the block layer expects a 512B aligned buffer(s).
Adding Ming to the thread.
