[PATCH 0/4] btrfs: enable encoded read/write/send for bs > ps cases

[Qu Wenruo <wqu@suse.com>]

Previously encoded read/write/send is disabled for bs > ps cases,
because they are either using regular pages or kvmallocated memories as
buffer.

This means their buffers do not meet the folio size requirement (each 
folio much contain at least one fs block, no block can cross large folio
boundries).


This series address the limits by allowing the following functionalities
to support regular pages, without relying on large folios:

- Checksum calculation
  Now instead of passing a single @paddr which is ensured to be inside a
  large folio, an array, paddrs[], is passed in.

  For bs <= ps cases, it's still a single paddr.

  For bs > ps cases, we can accept an array of multiple paddrs, that
  represents a single fs block.

- Read repair
  Allow btrfs_repair_io_failure() to submit a bio with multiple
  incontiguous pages.

  The same paddrs[] array building scheme.

  But this time since we need to submit a bio with multiple bvecs, we
  can no longer use the current on-stack bio.

  This also brings a small improvement for metadata read-repair, we can
  submit the whole metadata block in one go.

- Read verification
  Just build the paddrs[] array for bs > ps cases and pass the array
  into btrfs_calculate_block_csum_folio().

Unfortunately since there is no reliable on-stack VLA support, we have
to pay the extra on-stack memory (128 bytes for x86_64, or 8 bytes for
64K page sized systems) everywhere, even if 99% of the cases our block
size is no larger than page size.

Another thing is, even with all those support, direct IO is still not
supported.
The problem is iomap can still split the bio between pages, breaking our
bio size requirement (still have to be block aligned).

Qu Wenruo (4):
  btrfs: make btrfs_csum_one_bio() handle bs > ps without large folios
  btrfs: make btrfs_repair_io_failure() handle bs > ps cases without
    large folios
  btrfs: make read verification handle bs > ps cases without large
    folios
  btrfs: enable encoded read/write/send for bs > ps cases

 fs/btrfs/bio.c         | 140 +++++++++++++++++++++++++++++------------
 fs/btrfs/bio.h         |   2 +-
 fs/btrfs/btrfs_inode.h |   8 ++-
 fs/btrfs/disk-io.c     |  29 +++++----
 fs/btrfs/file-item.c   |  15 ++++-
 fs/btrfs/inode.c       |  91 ++++++++++++++++++---------
 fs/btrfs/ioctl.c       |  21 -------
 fs/btrfs/send.c        |   9 +--
 8 files changed, 200 insertions(+), 115 deletions(-)

-- 
2.50.1