stop passing a writeback_control to swap/shmem writeout

[Christoph Hellwig <hch@lst.de>]

Hi all,

this series was intended to remove the last remaining users of
AOP_WRITEPAGE_ACTIVATE after my other pending patches removed the
rest, but spectacularly failed at that.

But instead it nicely improves the code, and removes two pointers
and a flag from struct writeback_control.

Note that the last patch needs this f2fs series to compile, so
it should probably be delayed until after -rc1:

https://lore.kernel.org/lkml/20250508051520.4169795-1-hch@lst.de/

Diffstat:
 drivers/gpu/drm/i915/gem/i915_gem_shmem.c |    3 -
 drivers/gpu/drm/ttm/ttm_backup.c          |    9 ---
 fs/fuse/file.c                            |   11 ---
 fs/nfs/write.c                            |    2 
 fs/nilfs2/mdt.c                           |    2 
 fs/nilfs2/segment.c                       |   16 -----
 fs/nilfs2/segment.h                       |    1 
 include/linux/shmem_fs.h                  |    5 +
 include/linux/writeback.h                 |   11 ---
 include/trace/events/btrfs.h              |    7 --
 include/trace/events/writeback.h          |    8 --
 mm/page_io.c                              |   71 +++++++++++--------------
 mm/shmem.c                                |   17 ++----
 mm/swap.h                                 |    6 +-
 mm/vmscan.c                               |   84 +++++++++++++-----------------
 mm/zswap.c                                |    5 -
 16 files changed, 94 insertions(+), 164 deletions(-)