The zcrx path can encounter various conditions that lead to internal
fallbacks or errors. These errors can have a large impact on performance
and functionality but are not yet not being reported to the user which
is then unable to take action.

This series addresses this problem by adding a new notification system
paired with a statistics structure. The notification system currently
report out of buffer and packets that fallback to copy. The statistics
structure report the number and total size of packets that were copied
rather than received via the zero-copy path.

The out of buffer notification allows the user to actually adjust the
buffer sizing when registering zcrx support for the ifq. Some future
work could allow the user to add more memory on the fly to the pool so
the page allocator doesn't run out of memory.

This series can be tested using the include kselftest modification and
using the liburing series that updates headers and tests/examples so
that it uses notifications and statistics.

Changes in v2:
- Rebase on top of Pavel's branch that now uses a single CQE per notif
- Change notification mask to type (ie one CQE per event)
- Use a type rather than a mask for rearm as well
- Update tests to use single typei
- Update documentatiopn to state that notif CQEs are sent for a single
  event
- Fix zero init of zcrx_query_notif __resv field
- Rename resv1 to __resv1
- Reduce __resv2 size to match io_uring_query_opcode size
- Verifies that stats_offset is 0 if FLAG_STATS is zero
- Added zcrx notif query sequence to documentation
- Add _copy_fallback to test name

---

Clément Léger (4):
  io_uring/zcrx: notify user on frag copy fallback
  io_uring/zcrx: add shared-memory notification statistics
  Documentation: networking: document zcrx notifications and statistics
  selftests: iou-zcrx: add notification and stats test for zcrx

Pavel Begunkov (2):
  io_uring/zcrx: add ctx pointer to zcrx
  io_uring/zcrx: notify user when out of buffers

 Documentation/networking/iou-zcrx.rst         | 121 ++++++++++++
 include/uapi/linux/io_uring/query.h           |  12 ++
 include/uapi/linux/io_uring/zcrx.h            |  36 +++-
 io_uring/io_uring.c                           |   2 +-
 io_uring/io_uring.h                           |   1 +
 io_uring/query.c                              |  16 ++
 io_uring/zcrx.c                               | 180 +++++++++++++++++-
 io_uring/zcrx.h                               |  11 +-
 .../selftests/drivers/net/hw/iou-zcrx.c       | 114 ++++++++++-
 .../selftests/drivers/net/hw/iou-zcrx.py      |  49 ++++-
 10 files changed, 517 insertions(+), 25 deletions(-)

-- 
Clément Léger

On 5/18/26 16:35, Clément Léger wrote:
> The zcrx path can encounter various conditions that lead to internal
> fallbacks or errors. These errors can have a large impact on performance
> and functionality but are not yet not being reported to the user which
> is then unable to take action.> 
> This series addresses this problem by adding a new notification system
> paired with a statistics structure. The notification system currently
> report out of buffer and packets that fallback to copy. The statistics
> structure report the number and total size of packets that were copied
> rather than received via the zero-copy path.
> 
> The out of buffer notification allows the user to actually adjust the
> buffer sizing when registering zcrx support for the ifq. Some future
> work could allow the user to add more memory on the fly to the pool so
> the page allocator doesn't run out of memory.

Looks good, I'm going to take the first 4 and send out with other
zcrx patches.

-- 
Pavel Begunkov