Block storage copy offloading

Hi Jens,

This patch series implements a new approach for copy offloading. Compared to
Nitesh' approach, the differences are as follows:
 - Two new limits have been introduced representing the maximum number of source
   and destination ranges. Support for multiple source ranges for the NVMe Copy
   command has been added.
 - The blkdev_copy_offload() function can now submit multiple copy offload
   commands instead of only one.
 - The implementation no longer depends on block layer plugging.

This patch series includes copy offloading support for the Linux kernel block
layer core, the device mapper core, the null_blk and the NVMe and nvmet drivers.
Support for the scsi_debug and SCSI core will follow later.

Test scripts are available here:
https://github.com/bvanassche/blktests/tree/copy-offloading

See also Bart Van Assche, [LSF/MM/BPF TOPIC] Block storage copy offloading,
January 2026
(https://lore.kernel.org/all/0cfe6fe2-3865-4dc2-92a7-74b12...).

See also Nitesh Shetty, Implement copy offload support, May 2024
(https://lore.kernel.org/linux-block/20240520102033.9361-1...).

Anuj Gupta (1):
  fs/read_write: Generalize generic_copy_file_checks()

Bart Van Assche (4):
  block: Introduce blkdev_copy_offload()
  block: Introduce accessor functions for copy offload bios
  dm: Add support for copy offloading
  dm-linear: Enable copy offloading

Nitesh Shetty (7):
  block: Introduce queue limits for copy offloading
  block: Add the REQ_OP_COPY_{SRC,DST} operations
  block: Add an onloaded copy implementation
  fs, block: Add copy_file_range() support for block devices
  nvme: Add copy offloading support
  nvmet: Support the Copy command
  null_blk: Add support for REQ_OP_COPY_*

 Documentation/ABI/stable/sysfs-block |  24 +
 Documentation/block/null_blk.rst     |   4 +
 block/Makefile                       |   2 +-
 block/bio.c                          |   1 +
 block/blk-copy.c                     | 631 +++++++++++++++++++++++++++
 block/blk-core.c                     |  38 ++
 block/blk-merge.c                    |  13 +
 block/blk-settings.c                 |  36 ++
 block/blk-sysfs.c                    |  35 ++
 block/blk.h                          |   5 +
 block/fops.c                         |  54 +++
 drivers/block/null_blk/main.c        | 113 +++++
 drivers/block/null_blk/null_blk.h    |   1 +
 drivers/md/dm-linear.c               |   6 +
 drivers/md/dm-table.c                |   8 +
 drivers/nvme/host/constants.c        |   1 +
 drivers/nvme/host/core.c             | 106 +++++
 drivers/nvme/host/trace.c            |  21 +-
 drivers/nvme/target/admin-cmd.c      |  26 +-
 drivers/nvme/target/io-cmd-bdev.c    |  80 ++++
 drivers/nvme/target/io-cmd-file.c    |  59 ++-
 drivers/nvme/target/trace.c          |  19 +
 fs/read_write.c                      |   8 +-
 include/linux/blk-copy.h             |  50 +++
 include/linux/blk_types.h            |  57 +++
 include/linux/blkdev.h               |  20 +-
 include/linux/nvme.h                 |  47 +-
 27 files changed, 1449 insertions(+), 16 deletions(-)
 create mode 100644 block/blk-copy.c
 create mode 100644 include/linux/blk-copy.h