support file system generated / verified integrity information

[Christoph Hellwig <hch@lst.de>]

Hi all,

this series adds support to generate and verify integrity information
(aka T10 PI) in the file system, instead of the automatic below the
covers support that is currently used.

There two reasons for this:

  a) to increase the protection enveloped.  Right now this is just a
     minor step from the bottom of the block layer to the file system,
     but it is required to support io_uring integrity data passthrough in
     the file system similar to the currently existing support for block
     devices, which will follow next.  It also allows the file system to
     directly see the integrity error and act upon in, e.g. when using
     RAID either integrated (as in btrfs) or by supporting reading
     redundant copies through the block layer.
  b) to make the PI processing more efficient.  This is primarily a
     concern for reads, where the block layer auto PI has to schedule a
     work item for each bio, and the file system them has to do it again
     for bounce buffering.  Additionally the current iomap post-I/O
     workqueue handling is a lot more efficient by supporting merging and
     avoiding workqueue scheduling storms.

The implementation is based on refactoring the existing block layer PI
code to be reusable for this use case, and then adding relatively small
wrappers for the file system use case.  These are then used in iomap
to implement the semantics, and wired up in XFS with a small amount of
glue code.

Compared to the baseline (iomap-bounce branch), this does not change
performance for writes, but increases read performance up to 15% for 4k
I/O, with the benefit decreasing with larger I/O sizes as even the
baseline maxes out the device quickly.  But even for larger I/O sizes,
the number of context switches decreases and cpu usage sees a minor
decrease.

The patches both require the recent integrity changes in the block tree
and the direct I/O bounce buffering series I previously sent out, so
you're probably better off just using the git tree instead of applying
the patches.

Git tree:

    git://git.infradead.org/users/hch/misc.git iomap-pi

Gitweb:

    https://git.infradead.org/?p=users/hch/misc.git;a=shortlog;h=refs/heads/iomap-pi

Diffstat:
 block/Makefile                |    2 
 block/bio-integrity-auto.c    |   80 +++---------------------
 block/bio-integrity-fs.c      |   81 +++++++++++++++++++++++++
 block/bio-integrity.c         |   64 +++++++++++++++++++
 block/bio.c                   |   17 +++--
 block/blk-mq.c                |    6 +
 block/blk-settings.c          |   13 ----
 block/blk.h                   |    6 +
 block/t10-pi.c                |   12 +--
 drivers/nvdimm/btt.c          |    6 +
 fs/fuse/file.c                |    5 -
 fs/iomap/bio.c                |  135 ++++++++++++++++++++++++++++--------------
 fs/iomap/buffered-io.c        |    8 +-
 fs/iomap/direct-io.c          |   15 ++++
 fs/iomap/internal.h           |   14 ++++
 fs/iomap/ioend.c              |   28 +++++++-
 fs/xfs/xfs_aops.c             |   47 +++++++++++++-
 fs/xfs/xfs_iomap.c            |    9 +-
 include/linux/bio-integrity.h |   12 ++-
 include/linux/bio.h           |    2 
 include/linux/blk-integrity.h |   21 ++++--
 include/linux/blkdev.h        |   34 ++++++++--
 include/linux/iomap.h         |   20 +++++-
 23 files changed, 456 insertions(+), 181 deletions(-)