Re: [PATCH 2/2] mm: set PG_dma_pinned on get_user_pages*()

[Christoph Hellwig]

On Sun, Jun 17, 2018 at 01:10:04PM -0700, Dan Williams wrote:
> I believe kernel behavior regression is a primary concern as now
> fallocate() and truncate() can randomly fail where they didn't before.

Fail or block forever due to actions of other unprivileged users.

That is a complete no-go.