[PATCH v2 0/4] btrfs: prepare and move async csum generation out of experimental feautres

[Qu Wenruo <wqu@suse.com>]

[CHANGELOG]
v2:
- Introduce a patch to fix a potential data loss with async direct
  writes
  This is an existing bug, not only affecting the async data csum
  generation. Introduce a dedicated fix for it.

- Introduce a patch to fixx an ASSERT() false alert race
  Again an existing bug.

Sashiko exposed several problems related to previous default async csum
generation, one fix related to encoded writes is already merged.

The remaining problems are:

- Possible data loss due to fast fsync with async direct writes
  Fixed by the first patch, not only affecting async csum generation.
  Although async csum generation will make it more obvious.

- A possible ASSERT() race which can trigger false alert
  Fixed by the second patch, by moving the ASSERT() out of the workqueue
  workload.

- Potential workqueue flush problems related to endio_workers
  Fixed by the 3rd patch, also as a preparation for the incoming default
  async data csum generation.

Then we can finally enable async data csum generation by default to
improve the data write performance, and completely get rid of the old
csum offloading behavior.

Qu Wenruo (4):
  btrfs: do not allow fast fsync if there is any async dio write
  btrfs: fix an ASSERT() race with async csum generation
  btrfs: make btrfs_fs_info::workers to be a regular workqueue
  btrfs: move async data csum generation out of experimental features

 fs/btrfs/Kconfig     |   2 -
 fs/btrfs/bio.c       | 139 +------------------------------------------
 fs/btrfs/direct-io.c |  11 ++++
 fs/btrfs/disk-io.c   |  47 ++++++---------
 fs/btrfs/file-item.c |  15 ++---
 fs/btrfs/file-item.h |   2 +-
 fs/btrfs/fs.h        |  17 +-----
 fs/btrfs/super.c     |   2 +-
 8 files changed, 43 insertions(+), 192 deletions(-)

-- 
2.56.0