[PATCH 00/12] btrfs reads through iomap

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

These patches incorporate btrfs buffered reads using iomap code.
The final goal here is to give all folio handling to iomap. This is the
first installment to be followed by writes, writebacks and eventually
subpage support.

The crux of the changes are:
 * Since btrfs uses it's own bio handling structure, the btrfs bioset is
passed to iomap code in order to create a bio with the folios.
 * For compressed extents:
   - IOMAP_ENCODED which behaves like IOMAP_MAPPED, except, we supply
     the iomap back to submit_io() to identify if it is encoded.
   - The iomap code needs to keep a track of the previous iomap struct
     in order to pass it to submit_io with the corresponding iomap
   - A change in iomap struct should create a new bio

I have tested this patchset against a full run of xfstests for btrfs.

The current code does not support subpage access of iomap. Subpage
will be hopefully incorporated once the write and the writeback goes
through.

Code is available at https://github.com/goldwynr/linux/tree/buffered-iomap

Goldwyn Rodrigues (12):
  iomap: check if folio size is equal to FS block size
  iomap: Introduce iomap_read_folio_ops
  iomap: add bioset in iomap_read_folio_ops for filesystems to use own
    bioset
  iomap: include iomap_read_end_io() in header
  iomap: Introduce IOMAP_ENCODED
  iomap: Introduce read_inline() function hook
  btrfs: btrfs_em_to_iomap() to convert em to iomap
  btrfs: iomap_begin() for buffered reads
  btrfs: define btrfs_iomap_read_folio_ops
  btrfs: define btrfs_iomap_folio_ops
  btrfs: add read_inline for folio operations for read() calls
  btrfs: switch to iomap for buffered reads

 block/fops.c           |   4 +-
 fs/btrfs/bio.c         |   2 +-
 fs/btrfs/bio.h         |   1 +
 fs/btrfs/extent_io.c   | 131 +++++++++++++++++++++++++++++++++++++++++
 fs/erofs/data.c        |   4 +-
 fs/gfs2/aops.c         |   4 +-
 fs/iomap/buffered-io.c | 117 +++++++++++++++++++++++++-----------
 fs/xfs/xfs_aops.c      |   4 +-
 fs/zonefs/file.c       |   4 +-
 include/linux/iomap.h  |  37 +++++++++++-
 10 files changed, 260 insertions(+), 48 deletions(-)

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2.46.1