Re: [PATCH] f2fs: do not support mmap write for large folio

Jaegeuk Kim
2026-04-08T18:09:00Z

On 04/08, David Hildenbrand (Arm) wrote:
> On 4/8/26 07:03, Christoph Hellwig wrote:
> > On Tue, Apr 07, 2026 at 10:58:11PM +0000, Jaegeuk Kim wrote:
> >> On 04/06, Christoph Hellwig wrote:
> >>>
> >>> Why? And how is this not breaking applications?
> >>
> >> Since we only support the large folio on the read case.
> >
> > In general spelling such basic out in the commit log, and even comments
> > is really helpful. I'm curious how this works, though - by the time
> > you read a large folio you don't know if it will ever be written to.
>
> Why are only large folios supported for read?
>
> Where is that allocation logic and how can that path even be triggered?
>
> Also, usually we check for large folios by testing the actual folio, not
> whether the mapping supports them?

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v7.0-rc7&id=05e65c14ea59a401cec4284e9d612f9d5dc1b3f8

Currently I think it's simple to check the mapping in our case.

>
> --
> Cheers,
>
> David