Hi-
I have a report that net/sunrpc/xprtrdma/frwr_ops.c::frwr_map()
is attempting to register a mix of GPU and CPU pages with a
single MR during an NFSv4 READ.
We think we understand where both pages are coming from, and
why frwr_map() is attempting to coalesce them (the verbs
provider happens to support IB_DEVICE_SG_GAPS_REG).
frwr_map() does this:
305 for (i = 0; i < nsegs;) {
306 sg_set_page(&mr->mr_sg[i], seg->mr_page,
307 seg->mr_len, seg->mr_offset);
308
309 ++seg;
310 ++i;
311 if (ep->re_mrtype == IB_MR_TYPE_SG_GAPS)
312 continue;
313 if ((i < nsegs && seg->mr_offset) ||
314 offset_in_page((seg-1)->mr_offset + (seg-1)->mr_len))
315 break;
316 }
If GPU and CPU pages are not considered contiguous, then some
additional loop termination logic is needed here so that at
a boundary between page types, xprtrdma will simply move
into a fresh MR instead of coalescing.
Does anyone have suggestions of where to look for an
appropriate check?
TIA
--
Chuck Lever
