[RESEND,x3,v9,0/9] fs: interface for directly reading/writing compressed data

Message

Omar Sandoval June 17, 2021, 11:51 p.m. UTC

From: Omar Sandoval <[e-mail]>

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. I have test cases (including fsstress
support) and example programs which I'll send up once the dust settles
[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. The patches implementing the send/receive support
were sent with the last submission of this series [2].

Patches 1-3 add the VFS support, UAPI, and documentation. 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 [3],
which is in turn currently based on v5.13-rc6.

This is a _resend of a resend of a resend_ of v9 [4], rebased on the
latest kdave/misc-next branch.

In the last resend, there was some good discussion around how to support
encryption with this interface in the future. The conclusion was that
this interface should suffice for file data, and we would need separate
interface(s) for working with encrypted file names. So, this really just
needs review on the VFS side.

1: https://github.com/osandov/xfstests/tree/rwf-encoded
2: https://lore.kernel.org/linux-btrfs/[e-mail]/
3: https://github.com/kdave/btrfs-devel/tree/misc-next
4: https://lore.kernel.org/linux-fsdevel/[e-mail]/

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 | 240 ++++++
 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                          |  46 +-
 fs/btrfs/inode.c                         | 925 +++++++++++++++++++++--
 fs/btrfs/ordered-data.c                  | 124 +--
 fs/btrfs/ordered-data.h                  |  25 +-
 fs/btrfs/relocation.c                    |   4 +-
 fs/fcntl.c                               |  10 +-
 fs/namei.c                               |   4 +
 fs/read_write.c                          | 168 +++-
 include/linux/encoded_io.h               |  17 +
 include/linux/fcntl.h                    |   2 +-
 include/linux/fs.h                       |  13 +
 include/linux/uio.h                      |   1 +
 include/uapi/asm-generic/fcntl.h         |   4 +
 include/uapi/linux/encoded_io.h          |  30 +
 include/uapi/linux/fs.h                  |   5 +-
 lib/iov_iter.c                           |  91 +++
 26 files changed, 1559 insertions(+), 234 deletions(-)
 create mode 100644 Documentation/filesystems/encoded_io.rst
 create mode 100644 include/linux/encoded_io.h
 create mode 100644 include/uapi/linux/encoded_io.h