folio-5.18

Folio changes for 5.18

Several of us had overlapping, conflicting changes to the MM this
round, and I volunteered to send the pull request.

 - Hugh rewrote how munlock works to massively reduce the contention
   on i_mmap_rwsem:
   https://lore.kernel.org/linux-mm/8e4356d-9622-a7f0-b2c-f116b5f2efea@google.com/
 - Christoph sorted out the page refcount mess for ZONE_DEVICE pages:
   https://lore.kernel.org/linux-mm/20220210072828.2930359-1-hch@lst.de/
 - I converted GUP to use folios and make pincount available for order-1
   pages.
 - I converted a few more truncation functions to use folios
 - I converted page_vma_mapped_walk to use PFNs instead of pages
 - I converted rmap_walk to use folios
 - I converted most of shrink_page_list() to use a folio
 - I added support for creating large folios in readahead
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