[LU-15092] Fix logic for unaligned transfer with o2iblnd

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.15.0
• Severity: 3
• Assignee: Chris Horn
• Reporter: Chris Horn

Description

It's possible for there to be an offset for the first page of a
transfer. However, there are two bugs with this code in o2iblnd.

The first is that this use-case will require LNET_MAX_IOV + 1 local
RDMA fragments, but we do not specify the correct corresponding values
for the max page list to ib_alloc_fast_reg_page_list(),
ib_alloc_fast_reg_mr(), etc.

The second issue is that the logic in kiblnd_setup_rd_iov() and
kiblnd_setup_rd_kiov() attempts to obtain one more scatterlist entry
than is actually needed. This causes the transfer to fail with -EFAULT.

Issue Links

• is related to: LU-13802 New i/o path: Buffered i/o as DIO