[PATCH 0/2] btrfs: introduce a new experimental feature, RAID56_VSL

[Qu Wenruo <wqu@suse.com>]

The new feature stands for RAID56 Variable Stripe Length, however the
VSL part is not implemented yet, thus the whole feature is still hidden
behind experimental, and there are definitely works left to properly
split the 1st patch.

But for now, this series can pass most fstests cases.
The failing ones are all related to mixed block groups, which can not be
created nor mounted with this new feature.

The roadmap for the full RAID56 VSL implementation is split into two
parts:

- Introduce a new datasize member
  This series.

  An fs with data_size 8K and sectorsize 4K will act like a fs with
  sectorsize 8K.
  Meaning the minimal write size is 8K for data.

  However the checksum is still calculated based sectorsize, meanwhile
  we can still recover each corrupted 4K sector inside a 8K data block.

  The idea and implementation is not that complex, we're just reusing
  the existing bs > ps support to handle it (on 4K page sized systems).

  But the challenge is the details where some part of the code still
  requires sectorsize (checksum related), meanwhile every other location
  goes datasize for data.

- Introduce a new RAID56_VSL chunk type
  It will have the following requirements:

  * Can have up to (datasize / sectorsize) data stripes

  * The number of data stripes are always power of 2
    This is only for every RAID56_VSL chunk, users can still have
    whatever number of devices in the fs.

  * The full stripe length is always datasize

  This allows every data write to be full stripe aligned.
  And for read repair/scrub, we can still locate and recover a single
  sector inside a RAID56 stripe.

  This is less flex than the traditional RAID56, which has no limit on
  the number of data stripes, but has the write-hole problem.
  And will require users to determine the maximum device numbers at mkfs
  time, without any way to change to another datasize.

  But the second part is pretty easy to implement.

As the digest shows, the biggest problem is the first patch, which is
touching over 200 sectorsize users, and is definitely the source of all
bugs I hit and fixed so far.

If anyone has a better way to address the rename, I'm all ears.

Qu Wenruo (2):
  btrfs: split sectorsize into datasize and sectorsize
  btrfs: implement a new incompat feature, raid56_vsl

 fs/btrfs/accessors.h                   |   2 +
 fs/btrfs/bio.c                         |  16 +++-
 fs/btrfs/block-group.c                 |   2 +-
 fs/btrfs/btrfs_inode.h                 |  10 +++
 fs/btrfs/compression.c                 |  12 +--
 fs/btrfs/defrag.c                      |  14 +--
 fs/btrfs/delalloc-space.c              |  22 ++---
 fs/btrfs/direct-io.c                   |   6 +-
 fs/btrfs/disk-io.c                     |  43 +++++++---
 fs/btrfs/extent-io-tree.c              |   2 +-
 fs/btrfs/extent-tree.c                 |   4 +-
 fs/btrfs/extent_io.c                   |  62 +++++++-------
 fs/btrfs/extent_map.c                  |   2 +-
 fs/btrfs/fiemap.c                      |   2 +-
 fs/btrfs/file-item.c                   |  22 +++--
 fs/btrfs/file.c                        |  72 ++++++++--------
 fs/btrfs/fs.h                          |  27 ++++--
 fs/btrfs/inode-item.c                  |   6 +-
 fs/btrfs/inode.c                       | 113 +++++++++++++------------
 fs/btrfs/ioctl.c                       |  12 +--
 fs/btrfs/lzo.c                         |  14 +--
 fs/btrfs/reflink.c                     |  16 ++--
 fs/btrfs/relocation.c                  |  16 ++--
 fs/btrfs/send.c                        |   4 +-
 fs/btrfs/subpage.c                     |  96 +++++++++++++++------
 fs/btrfs/subpage.h                     |   2 +-
 fs/btrfs/super.c                       |   8 +-
 fs/btrfs/sysfs.c                       |   8 +-
 fs/btrfs/tests/btrfs-tests.c           |   6 +-
 fs/btrfs/tests/free-space-tree-tests.c |   2 +-
 fs/btrfs/tree-checker.c                |   2 +-
 fs/btrfs/tree-log.c                    |   6 +-
 fs/btrfs/volumes.c                     |   2 +-
 fs/btrfs/zlib.c                        |   6 +-
 fs/btrfs/zoned.c                       |   4 +-
 fs/btrfs/zstd.c                        |   8 +-
 include/uapi/linux/btrfs.h             |  22 +++++
 include/uapi/linux/btrfs_tree.h        |   3 +-
 38 files changed, 403 insertions(+), 273 deletions(-)

-- 
2.55.0