(in)consistency of page/folio function naming

[Matthew Wilcox <willy@infradead.org>]

I'm going through my patch queue implementing peterz's request to rename
FolioUptodate() as folio_uptodate().  It's going pretty well, but it
throws into relief all the places where we're not consistent naming
existing functions which operate on pages as page_foo().  The folio
conversion is a great opportunity to sort that out.  Mostly so far, I've
just done s/page/folio/ on function names, but there's the opportunity to
regularise a lot of them, eg:

	put_page		folio_put
	lock_page		folio_lock
	lock_page_or_retry	folio_lock_or_retry
	rotate_reclaimable_page	folio_rotate_reclaimable
	end_page_writeback	folio_end_writeback
	clear_page_dirty_for_io	folio_clear_dirty_for_io

Some of these make a lot of sense -- eg when ClearPageDirty has turned
into folio_clear_dirty(), having folio_clear_dirty_for_io() looks regular.
I'm not entirely convinced about folio_lock(), but folio_lock_or_retry()
makes more sense than lock_page_or_retry().  Ditto _killable() or
_async().

Thoughts?