Re: [PATCH v1 12/15] fs/direct-io: keep track of wether a page is coming from GUP or not

Dave Chinner
2019-04-11T23:14:55Z

On Thu, Apr 11, 2019 at 05:08:31PM -0400, jglisse@redhat.com wrote:
> From: Jérôme Glisse <jglisse@redhat.com>
>
> We want to keep track of how we got a reference on page when doing DIO,
> ie wether the page was reference through GUP (get_user_page*) or not.
> For that this patch rework the way page reference is taken and handed
> over between DIO code and BIO. Instead of taking a reference for page
> that have been successfuly added to a BIO we just steal the reference
> we have when we lookup the page (either through GUP or for ZERO_PAGE).
>
> So this patch keep track of wether the reference has been stolen by the
> BIO or not. This avoids a bunch of get_page()/put_page() so this limit
> the number of atomic operations.

Is the asme set of changes appropriate for the fs/iomap.c direct IO
path (i.e. XFS)?

-Dave.
--
Dave Chinner
david@fromorbit.com