On Wed, Jun 23, 2021 at 01:55:21PM +0800, Qu Wenruo wrote:

Qu Wenruo (8):
  btrfs: don't pass compressed pages to
    btrfs_writepage_endio_finish_ordered()
  btrfs: make btrfs_subpage_end_and_test_writer() to handle pages not
    locked by btrfs_page_start_writer_lock()
  btrfs: make compress_file_range() to be subpage compatible
  btrfs: make btrfs_submit_compressed_write() to be subpage compatible
  btrfs: use async_chunk::async_cow to replace the confusing pending
    pointer
  btrfs: make end_compressed_bio_writeback() to be subpage compatble
  btrfs: make extent_write_locked_range() to be subpage compatible
  btrfs: only allow subpage compression if the range fully covers the
    first page

Some of the patches seem independent and potentially could be taken into
5.14 now but I guess the whole subpage could go in one big batch to 5.15
so it won't help you much anyway. The significant change is the last
patch and so far I think it's acceptable.