btrfs: remove folio parameter from ordered io related functions

btrfs: remove folio parameter from ordered io related functions

Both functions btrfs_finish_ordered_extent() and
btrfs_mark_ordered_io_finished() are accepting an optional folio
parameter.

That @folio is passed into can_finish_ordered_extent(), which later will
test and clear the ordered flag for the involved range.

However I do not think there is any other call site that can clear
ordered flags of an page cache folio and can affect
can_finish_ordered_extent().

There are limited *_clear_ordered() callers out of
can_finish_ordered_extent() function:

- btrfs_migrate_folio()
  This is completely unrelated, it's just migrating the ordered flag to
  the new folio.

- btrfs_cleanup_ordered_extents()
  We manually clean the ordered flags of all involved folios, then call
  btrfs_mark_ordered_io_finished() without a @folio parameter.
  So it doesn't need and didn't pass a @folio parameter in the first
  place.

- btrfs_writepage_fixup_worker()
  This function is going to be removed soon, and we should not hit that
  function anymore.

- btrfs_invalidate_folio()
  This is the real call site we need to bother with.

  If we already have a bio running, btrfs_finish_ordered_extent() in
  end_bbio_data_write() will be executed first, as
  btrfs_invalidate_folio() will wait for the writeback to finish.

  Thus if there is a running bio, it will not see the range has
  ordered flags, and just skip to the next range.

  If there is no bio running, meaning the ordered extent is created but
  the folio is not yet submitted.

  In that case btrfs_invalidate_folio() will manually clear the folio
  ordered range, but then manually finish the ordered extent with
  btrfs_dec_test_ordered_pending() without bothering the folio ordered
  flags.

  Meaning if the OE range with folio ordered flags will be finished
  manually without the need to call can_finish_ordered_extent().

This means all can_finish_ordered_extent() call sites should get a range
that has folio ordered flag set, thus the old "return false" branch
should never be triggered.

Now we can:

- Remove the @folio parameter from involved functions
  * btrfs_mark_ordered_io_finished()
  * btrfs_finish_ordered_extent()

  For call sites passing a @folio into those functions, let them
  manually clear the ordered flag of involved folios.

- Move btrfs_finish_ordered_extent() out of the loop in
  end_bbio_data_write()

  We only need to call btrfs_finish_ordered_extent() once per bbio,
  not per folio.

- Add an ASSERT() to make sure all folio ranges have ordered flags
  It's only for end_bbio_data_write().

  And we already have enough safe nets to catch over-accounting of ordered
  extents.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>