[RFC 0/2] block: Introduce a BPF-based I/O scheduler

[Chengkaitao]

From: Kaitao Cheng <chengkaitao at kylinos.cn>

I have been working on adding a new BPF-based I/O scheduler. It has both
kernel and user-space parts. In kernel space, using per-ctx, I implemented
a simple elevator that exposes a set of BPF hooks. The goal is to move the
policy side of I/O scheduling out of the kernel and into user space, which
should greatly increase flexibility and applicability. To verify that the
whole stack works end to end, I wrote a simple BPF example program. I am
calling this feature the UFQ (User-programmable Flexible Queueing) I/O
scheduler.

This patch depends on new BPF functionality that I have already posted to
the BPF community but that is not yet in mainline. Details are in these
two threads:

https://lore.kernel.org/all/20260214124042.62229-1-pilgrimtao@gmail.com/
https://lore.kernel.org/all/20260316112843.78657-1-pilgrimtao@gmail.com/

To try it, you need to apply the patches from those series first.

Note: This is still somewhat experimental. I have only done basic testing,
there may be bugs or security issues, which I plan to address in follow-up
work. I am also looking for community feedback on whether this direction
and the implementation approach make sense, and what else we should
consider.

Kaitao Cheng (2):
  block: Introduce the UFQ I/O scheduler
  tools/ufq_iosched: add BPF example scheduler and build scaffolding

 block/Kconfig.iosched                         |   8 +
 block/Makefile                                |   1 +
 block/blk-merge.c                             |  49 +-
 block/blk-mq-sched.h                          |   4 +
 block/blk-mq.c                                |   8 +-
 block/blk-mq.h                                |   2 +-
 block/blk.h                                   |   2 +
 block/ufq-bpfops.c                            | 213 +++++++
 block/ufq-iosched.c                           | 526 ++++++++++++++++++
 block/ufq-iosched.h                           |  38 ++
 block/ufq-kfunc.c                             |  91 +++
 tools/ufq_iosched/.gitignore                  |   2 +
 tools/ufq_iosched/Makefile                    | 262 +++++++++
 tools/ufq_iosched/README.md                   | 136 +++++
 .../include/bpf-compat/gnu/stubs.h            |  12 +
 tools/ufq_iosched/include/ufq/common.bpf.h    |  73 +++
 tools/ufq_iosched/include/ufq/common.h        |  91 +++
 tools/ufq_iosched/include/ufq/simple_stat.h   |  21 +
 tools/ufq_iosched/ufq_simple.bpf.c            | 445 +++++++++++++++
 tools/ufq_iosched/ufq_simple.c                | 118 ++++
 20 files changed, 2094 insertions(+), 8 deletions(-)
 create mode 100644 block/ufq-bpfops.c
 create mode 100644 block/ufq-iosched.c
 create mode 100644 block/ufq-iosched.h
 create mode 100644 block/ufq-kfunc.c
 create mode 100644 tools/ufq_iosched/.gitignore
 create mode 100644 tools/ufq_iosched/Makefile
 create mode 100644 tools/ufq_iosched/README.md
 create mode 100644 tools/ufq_iosched/include/bpf-compat/gnu/stubs.h
 create mode 100644 tools/ufq_iosched/include/ufq/common.bpf.h
 create mode 100644 tools/ufq_iosched/include/ufq/common.h
 create mode 100644 tools/ufq_iosched/include/ufq/simple_stat.h
 create mode 100644 tools/ufq_iosched/ufq_simple.bpf.c
 create mode 100644 tools/ufq_iosched/ufq_simple.c

-- 
2.43.0