[LSF/MM/BPF TOPIC] Folios

[Matthew Wilcox <willy@infradead.org>]

You might think that with a fortnightly meeting, presentations on the
subject of folios at several conferences and hundreds of patches merged,
I'd be short of things to discuss at LSFMM.  Hah.

From a filesystem point of view,

 - Converting APIs that filesystems implement to use folios (aops, primarily)
   to be folio based instead of page based
 - What it takes to support large (ie multi-page) folios in your
   filesystem
 - Removing old page-based APIs used by filesystems (eg everything in
   mm/folio-compat.c)
 - Converting your filesystem to use iomap.

For the MM crowd:
 - Continued conversion of the MM from pages to folios
   - GUP is done
   - page_vma_mapped is done, not yet posted for review
   - rmap in progress
   - mlock in progress
   - vmscan in progress
   (this list will have changed by May)
 - Splitting out other page types from struct page
 - Dynamically allocating struct folio & shrinking struct page

I'm going to throw a discussion of mapcount into this as well; getting
mapcount right on a multi-page folio is expensive.  I intend to send a full
proposal for making mapcount less accurate by default soon; just haven't
found time to do it yet.