Re: [PATCH 03/16] mm: add PG_uncached page flag

Kirill A. Shutemov
2024-11-12T09:12:23Z

On Mon, Nov 11, 2024 at 04:37:30PM -0700, Jens Axboe wrote:
> Add a page flag that file IO can use to indicate that the IO being done
> is uncached, as in it should not persist in the page cache after the IO
> has been completed.

I have not found a way to avoid using a new bit. I am unsure if we have
enough bits on 32-bit systems with all possible features enabled.

In the worst-case scenario, we may need to make the feature 64-bit only.
I believe it should be acceptable as long as userspace is prepared for the
possibility that RWF_UNCACHED may fail. It is not going to be supported by
all filesystems anyway.

--
Kiryl Shutsemau / Kirill A. Shutemov