Re: [PATCH 1/4] mm: Trial do_wp_page() simplification

Jason Gunthorpe
2020-09-14T14:39:32Z

On Fri, Aug 21, 2020 at 07:49:55PM -0400, Peter Xu wrote:
> From: Linus Torvalds <torvalds@linux-foundation.org>
>
> How about we just make sure we're the only possible valid user fo the
> page before we bother to reuse it?
>
> Simplify, simplify, simplify.
>
> And get rid of the nasty serialization on the page lock at the same time.
>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> [peterx: add subject prefix]
> Signed-off-by: Peter Xu <peterx@redhat.com>
> mm/memory.c | 59 +++++++++++++++--------------------------------------
> 1 file changed, 17 insertions(+), 42 deletions(-)

I don't have a detailed explanation right now, but this patch appears
to be causing a regression where RDMA subsystem tests fail. Tests
return to normal when this patch is reverted.

It kind of looks like the process is not seeing DMA'd data to a
pin_user_pages()?

Thanks,
Jason