Re: [PATCH] fs/writeback: convert wbc_account_cgroup_owner to take a folio

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 09/26, Matthew Wilcox wrote:
> On Thu, Sep 26, 2024 at 04:01:21PM +0200, Pankaj Raghav (Samsung) wrote:
> > Convert wbc_account_cgroup_owner() to take a folio instead of a page,
> > and convert all callers to pass a folio directly except f2fs.
> > 
> > Convert the page to folio for all the callers from f2fs as they were the
> > only callers calling wbc_account_cgroup_owner() with a page. As f2fs is
> > already in the process of converting to folios, these call sites might
> > also soon be calling wbc_account_cgroup_owner() with a folio directly in
> > the future.
> 
> I was hoping for more from f2fs.  I still don't have an answer from them
> whether they're going to support large folios.  There's all kinds of
> crud already in these functions like:
> 
>         f2fs_set_bio_crypt_ctx(bio, fio->page->mapping->host,
>                         page_folio(fio->page)->index, fio, GFP_NOIO);
> 
> and this patch is making it worse, not better.  A series of patches
> which at least started to spread folios throughout f2fs would be better.
> I think that struct f2fs_io_info should have its page converted to
> a folio, for example.  Although maybe not; perhaps this structure can
> carry data which doesn't belong to a folio that came from the page cache.
> It's very hard to tell because f2fs is so mind-numbingly complex and
> riddled with stupid abstraction layers.

Hah, I don't think it's too complex at all tho, there's a somewhat complexity to
support file-based encryption, compression, and fsverity, which are useful
for Android users. Well, I don't see any strong needs to support large folio,
but some requests exist which was why we had to do some conversion.

> 
> But I don't know what the f2fs maintainers have planned.  And they won't
> tell me despite many times of asking.