Re: [PATCH 0/6] RFC v2: mm: gup/dma tracking

From: Christopher Lameter
Date: Mon Feb 04 2019 - 11:59:20 EST


On Mon, 4 Feb 2019, Christoph Hellwig wrote:

> On Mon, Feb 04, 2019 at 04:08:02PM +0000, Christopher Lameter wrote:
> > It may be worth noting a couple of times in this text that this was
> > designed for anonymous memory and that such use is/was ok. We are talking
> > about a use case here using mmapped access with a regular filesystem that
> > was not initially intended. The mmapping of from the hugepages filesystem
> > is special in that it is not a device that is actually writing things
> > back.
> >
> > Any use with a filesystem that actually writes data back to a medium
> > is something that is broken.
>
> Saying it was not intended seems rather odd, as it was supported
> since day 0 and people made use of it.

Well until last year I never thought there was a problem because I
considered it separate from regular filesystem I/O.