[PATCH 0/7] btrfs: per-fs compression workspace manager

[Qu Wenruo <wqu@suse.com>]

Currently btrfs utilizes the following components at a per-module basis:

- Folios pool
  A per-module pool for compressed data.
  All folios in the pool are page sized.

- Workspace
  A workspace is a compression algorithm specific structure, providing
  things like extra memory buffer and compression level handling.

- Workspace manager
  The workspace manager is managing the above workspaces for each
  algorithm.

All the folio pool/workspaces are using the fixed PAGE_SIZE buffer size,
this is fine for now as even for block size (bs) < page size (ps) cases,
a larger buffer size won't cause huge problems except wasting memories.

However if we're going to support bs > ps, this fixed PAGE_SIZE buffer
and per-module shared folios pool/workspaces will not work at all.

To address this problem, this series will move the workspace and
workspace manager into a per-fs basis, so that different fses (with
different block size) can have their own workspaces.

This brings a small memory usage reduce for bs < ps cases.
Now zlib/lzo/zstd will only allocate buffer using block size.

This is especially useful for lzo compression algorithm, as lzo is an
one-short compression algorithm, it doesn't support multi-shot (aka,
swapping input/output buffer halfway) compress/decompress.

Thus btrfs goes per-block compression for LZO, and compressed result
will never go larger than a block (or btrfs will just give up).
In that case, a 64K page sized buffer will waste 7/8th of the buffer.

This is part 1 of the preparation for btrfs bs > ps support.

Qu Wenruo (7):
  btrfs: add an fs_info parameter for compression workspace manager
  btrfs: add workspace manager initialization for zstd
  btrfs: add generic workspace manager initialization
  btrfs: migrate to use per-fs workspace manager
  btrfs: cleanup the per-module workspace managers
  btrfs: rename btrfs_compress_op to btrfs_compress_levels
  btrfs: reduce workspace buffer space to block size

 fs/btrfs/compression.c | 186 ++++++++++++++++++++++++-----------------
 fs/btrfs/compression.h |  49 +++++------
 fs/btrfs/disk-io.c     |   4 +
 fs/btrfs/fs.h          |  13 +++
 fs/btrfs/lzo.c         |  25 +++---
 fs/btrfs/zlib.c        |  16 ++--
 fs/btrfs/zstd.c        | 143 ++++++++++++++++---------------
 7 files changed, 248 insertions(+), 188 deletions(-)

-- 
2.50.1