Re: [PATCH v3 12/13] dax: handle truncate of dma-busy pages

[Christoph Hellwig]

On Fri, Oct 20, 2017 at 10:27:22AM -0700, Dan Williams wrote:
> I'll take a look at hooking this up through a page-idle callback. Can
> I get some breadcrumbs to grep for from XFS folks on how to set/clear
> the busy state of extents?

As Brian pointed out it's the xfs_extent_busy.c file (and I pointed
out the same in a reply to the previous series).  Be careful because
you'll need a refcount or flags now that there are different busy
reasons.

I still think we'd be better off just blocking on an elevated page
count directly in truncate as that will avoid all the busy list
manipulations.