[PATCH v5 0/9] fs: interface for directly reading/writing compressed data

[Omar Sandoval <osandov@osandov.com>]

This series adds an API for reading compressed data on a filesystem
without decompressing it as well as support for writing compressed data
directly to the filesystem. As with the previous submissions, I've
included a man page patch describing the API. I have test cases
(including fsstress support) and example programs which I'll send up
soon [1].

The main use-case is Btrfs send/receive: currently, when sending data
from one compressed filesystem to another, the sending side decompresses
the data and the receiving side recompresses it before writing it out.
This is wasteful and can be avoided if we can just send and write
compressed extents. Since the last posting of this series, I've
implemented the send support and Boris Burkov has implemented the
receive support using this interface; the speedup is significant. Those
patches will be sent shortly.

Patches 1-3 add the VFS support and UAPI. Patches 4-7 are Btrfs prep
patches. Patch 8 adds Btrfs encoded read support and patch 9 adds Btrfs
encoded write support.

These patches are based on Dave Sterba's Btrfs misc-next branch [2],
which is in turn based on v5.9-rc1.

Changes since v4 [3]:

- Rebased on kdave/misc-next.
- Clarified the man pages in several places.

1: https://github.com/osandov/xfstests/tree/rwf-encoded
2: https://github.com/kdave/btrfs-devel/tree/misc-next
3: https://lore.kernel.org/linux-fsdevel/cover.1582930832.git.osandov@fb.com/

Omar Sandoval (9):
  iov_iter: add copy_struct_from_iter()
  fs: add O_ALLOW_ENCODED open flag
  fs: add RWF_ENCODED for reading/writing compressed data
  btrfs: don't advance offset for compressed bios in
    btrfs_csum_one_bio()
  btrfs: add ram_bytes and offset to btrfs_ordered_extent
  btrfs: support different disk extent size for delalloc
  btrfs: optionally extend i_size in cow_file_range_inline()
  btrfs: implement RWF_ENCODED reads
  btrfs: implement RWF_ENCODED writes

 Documentation/filesystems/encoded_io.rst |  74 ++
 Documentation/filesystems/index.rst      |   1 +
 arch/alpha/include/uapi/asm/fcntl.h      |   1 +
 arch/parisc/include/uapi/asm/fcntl.h     |   1 +
 arch/sparc/include/uapi/asm/fcntl.h      |   1 +
 fs/btrfs/compression.c                   |  12 +-
 fs/btrfs/compression.h                   |   6 +-
 fs/btrfs/ctree.h                         |   9 +-
 fs/btrfs/delalloc-space.c                |  18 +-
 fs/btrfs/file-item.c                     |  35 +-
 fs/btrfs/file.c                          |  55 +-
 fs/btrfs/inode.c                         | 904 ++++++++++++++++++++---
 fs/btrfs/ordered-data.c                  |  80 +-
 fs/btrfs/ordered-data.h                  |  18 +-
 fs/btrfs/relocation.c                    |   4 +-
 fs/fcntl.c                               |  10 +-
 fs/namei.c                               |   4 +
 include/linux/fcntl.h                    |   2 +-
 include/linux/fs.h                       |  16 +
 include/linux/uio.h                      |   2 +
 include/uapi/asm-generic/fcntl.h         |   4 +
 include/uapi/linux/fs.h                  |  33 +-
 lib/iov_iter.c                           |  82 ++
 mm/filemap.c                             | 166 ++++-
 24 files changed, 1336 insertions(+), 202 deletions(-)
 create mode 100644 Documentation/filesystems/encoded_io.rst

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2.28.0