Re: remove iomap_writepage v2

[Christoph Hellwig <hch@lst.de>]

On Wed, Aug 10, 2022 at 09:43:58PM +0100, Matthew Wilcox wrote:
> To avoid duplicating work with you or Christoph ... it seems like the
> plan is to kill ->writepage entirely soon, so there's no point in me
> doing a sweep of all the filesystems to convert ->writepage to
> ->write_folio, correct?

While I won't commit to concrete definition of "soon" I think that is
the general plan, and I don't think converting ->writepage to
->write_folio is needed.

> I assume the plan for filesystems which have a writepage but don't have
> a ->writepages (9p, adfs, affs, bfs, ecryptfs, gfs2, hostfs, jfs, minix,
> nilfs2, ntfs, ocfs2, reiserfs, sysv, ubifs, udf, ufs, vboxsf) is to give
> them a writepages,

and  ->migrate_folio if missing, yes.

> modelled on iomap_writepages().  Seems that adding
> a block_writepages() might be a useful thing for me to do?

We have mpage_writepages which basically is the ->writepages counterpart
to block_write_full_page.  The only caveat is of course that it can
use multi-block mappings from the get_bock callback, so we need to make
sure the file systems don't do anything stupid there.