On Thu, Jan 31, 2019 at 9:06 AM Jarkko Sakkinen
[off-list ref] wrote:

Found something that *does* fix the issue. If I replace memcpy_*io()
calls with regular memcpy(), the driver works and all my tests pass.

That's not surprising, since that's what we used to do. And it's
horribly wrong because "memcpy()" can do things that are horribly
wrong on IO accesses. Like doing them twice, but alternatively also
"copy one byte at a time" which generally works, but is horrendously
slow for IO.

Can you check *which* memcpy_*io() triggers the issue? Maybe by
"bisecting" them (first perhaps on a file-by-file basis, and then
within a file).

                 Linus