Re: [RFC PATCH] block, fs: use FOLL_LONGTERM as gup_flags for direct IO

Jaewon Kim
2025-03-06T23:28:53Z

On Fri, Mar 7, 2025 at 12:26 AM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Thu, Mar 06, 2025 at 04:40:56PM +0900, Sooyong Suk wrote:
> > There are GUP references to pages that are serving as direct IO buffers.
> > Those pages can be allocated from CMA pageblocks despite they can be
> > pinned until the DIO is completed.
>
> direct I/O is eactly the case that is not FOLL_LONGTERM and one of
> the reasons to even have the flag. So big fat no to this.
>

Hello, thank you for your comment.
We, Sooyong and I, wanted to get some opinions about this
FOLL_LONGTERM for direct I/O as CMA memory got pinned pages which had
been pinned from direct io.

> You also completely failed to address the relevant mailinglist and
> maintainers.

I added block maintainer Jens Axboe and the block layer maillinst
here, and added Suren and Sandeep, too.