When running task_work for an exiting task, rather than perform the
issue retry attempt, the task_work is canceled. However, this isn't
done for a ring that has been closed. This can lead to requests being
successfully completed post the ring being closed, which is somewhat
confusing and surprising to an application.

Rather than just check the task exit state, also include the ring
ref state in deciding whether or not to terminate a given request when
run from task_work.

Cc: stable@vger.kernel.org # 6.1+
Link: https://github.com/axboe/liburing/discussions/1459
Reported-by: Benedek Thaler <thaler@thaler.hu>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Both io_poll_wq_wake() and io_cqring_wake() contain the exact same code,
and most of the comment in the latter applies equally to both.

Move the test and wakeup handling into a basic helper that they can both
use, and move part of the comment that applies generically to this new
helper.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Add a helper for posting 32 byte CQEs in a multishot mode and add a cmd
helper on top. As it specifically works with requests, the helper ignore
the passed in cqe->user_data and sets it to the one stored in the
request.

The command helper is only valid with multishot requests.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/c29d7720c16e1f981cfaa903df187138baa3946b.1750065793.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This function exists in both tctx.h (where it belongs) and in io_uring.h
as a remnant of before the tctx handling code got split out. Remove the
io_uring.h definition and ensure that sqpoll.c includes the tctx.h
header to get the definition.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Inflight marking is used so that do_exit() -> io_uring_files_cancel()
will find requests with files that reference an io_uring instance,
so they can get appropriately canceled before the files go away.
However, it's also called before the mm goes away.

Mark futex/futexv wait requests as being inflight, so that
io_uring_files_cancel() will prune them. This ensures that the mm stays
alive, which is important as an exiting mm will also free the futex
private hash buckets. An io_uring futex request with FUTEX2_PRIVATE
set relies on those being alive until the request has completed. A
recent commit added these futex private hashes, which get killed when
the mm goes away.

Fixes: 80367ad01d93 ("futex: Add basic infrastructure for local task local hash")
Link: https://lore.kernel.org/io-uring/38053.1749045482@localhost/
Reported-by: Robert Morris <rtm@csail.mit.edu>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

IOU_COMPLETE is more descriptive, in that it explicitly says that the
return value means "please post a completion for this request". This
patch completes the transition from IOU_OK to IOU_COMPLETE, replacing
existing IOU_OK users.

This is a purely mechanical change.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Don't rely on CQ sequence numbers for draining, as it has become messy
and needs cq_extra adjustments. Instead, base it on the number of
allocated requests and only allow flushing when all requests are in the
drain list.

As a result, cq_extra is gone, no overhead for its accounting in aux cqe
posting, less bloating as it was inlined before, and it's in general
simpler than trying to track where we should bump it and where it should
be put back like in cases of overflow. Also, it'll likely help with
cleaning and unifying some of the CQ posting helpers.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/46ece1e34320b046c06fee2498d6b4cd12a700f2.1746788718.git.asml.silence@gmail.com
Link: https://lore.kernel.org/r/24497b04b004bceada496033d3c9d09ff8e81ae9.1746944903.git.asml.silence@gmail.com
[axboe: fold in fix from link2]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Unlike earlier versions, io_msg_remote_post() creates a valid request
with a proper context, so don't pass a context to
io_req_task_work_add_remote() explicitly but derive it from the request.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/721f51cf34996d98b48f0bfd24ad40aa2730167e.1743190078.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull more io_uring updates from Jens Axboe:
 "Final separate updates for io_uring.

  This started out as a series of cleanups improvements and improvements
  for registered buffers, but as the last series of the io_uring changes
  for 6.15, it also collected a few fixes for the other branches on top:

   - Add support for vectored fixed/registered buffers.

     Previously only single segments have been supported for commands,
     now vectored variants are supported as well. This series includes
     networking and file read/write support.

   - Small series unifying return codes across multi and single shot.

   - Small series cleaning up registerd buffer importing.

   - Adding support for vectored registered buffers for uring_cmd.

   - Fix for io-wq handling of command reissue.

   - Various little fixes and tweaks"

* tag 'for-6.15/io_uring-reg-vec-20250327' of git://git.kernel.dk/linux: (25 commits)
  io_uring/net: fix io_req_post_cqe abuse by send bundle
  io_uring/net: use REQ_F_IMPORT_BUFFER for send_zc
  io_uring: move min_events sanitisation
  io_uring: rename "min" arg in io_iopoll_check()
  io_uring: open code __io_post_aux_cqe()
  io_uring: defer iowq cqe overflow via task_work
  io_uring: fix retry handling off iowq
  io_uring/net: only import send_zc buffer once
  io_uring/cmd: introduce io_uring_cmd_import_fixed_vec
  io_uring/cmd: add iovec cache for commands
  io_uring/cmd: don't expose entire cmd async data
  io_uring: rename the data cmd cache
  io_uring: rely on io_prep_reg_vec for iovec placement
  io_uring: introduce io_prep_reg_iovec()
  io_uring: unify STOP_MULTISHOT with IOU_OK
  io_uring: return -EAGAIN to continue multishot
  io_uring: cap cached iovec/bvec size
  io_uring/net: implement vectored reg bufs for zctx
  io_uring/net: convert to struct iou_vec
  io_uring/net: pull vec alloc out of msghdr import
  ...

Pull io_uring zero-copy receive support from Jens Axboe:
 "This adds support for zero-copy receive with io_uring, enabling fast
  bulk receive of data directly into application memory, rather than
  needing to copy the data out of kernel memory.

  While this version only supports host memory as that was the initial
  target, other memory types are planned as well, with notably GPU
  memory coming next.

  This work depends on some networking components which were queued up
  on the networking side, but have now landed in your tree.

  This is the work of Pavel Begunkov and David Wei. From the v14 posting:

    'We configure a page pool that a driver uses to fill a hw rx queue
     to hand out user pages instead of kernel pages. Any data that ends
     up hitting this hw rx queue will thus be dma'd into userspace
     memory directly, without needing to be bounced through kernel
     memory. 'Reading' data out of a socket instead becomes a
     _notification_ mechanism, where the kernel tells userspace where
     the data is. The overall approach is similar to the devmem TCP
     proposal

     This relies on hw header/data split, flow steering and RSS to
     ensure packet headers remain in kernel memory and only desired
     flows hit a hw rx queue configured for zero copy. Configuring this
     is outside of the scope of this patchset.

     We share netdev core infra with devmem TCP. The main difference is
     that io_uring is used for the uAPI and the lifetime of all objects
     are bound to an io_uring instance. Data is 'read' using a new
     io_uring request type. When done, data is returned via a new shared
     refill queue. A zero copy page pool refills a hw rx queue from this
     refill queue directly. Of course, the lifetime of these data
     buffers are managed by io_uring rather than the networking stack,
     with different refcounting rules.

     This patchset is the first step adding basic zero copy support. We
     will extend this iteratively with new features e.g. dynamically
     allocated zero copy areas, THP support, dmabuf support, improved
     copy fallback, general optimisations and more'

  In a local setup, I was able to saturate a 200G link with a single CPU
  core, and at netdev conf 0x19 earlier this month, Jamal reported
  188Gbit of bandwidth using a single core (no HT, including soft-irq).

  Safe to say the efficiency is there, as bigger links would be needed
  to find the per-core limit, and it's considerably more efficient and
  faster than the existing devmem solution"

* tag 'for-6.15/io_uring-rx-zc-20250325' of git://git.kernel.dk/linux:
  io_uring/zcrx: add selftest case for recvzc with read limit
  io_uring/zcrx: add a read limit to recvzc requests
  io_uring: add missing IORING_MAP_OFF_ZCRX_REGION in io_uring_mmap
  io_uring: Rename KConfig to Kconfig
  io_uring/zcrx: fix leaks on failed registration
  io_uring/zcrx: recheck ifq on shutdown
  io_uring/zcrx: add selftest
  net: add documentation for io_uring zcrx
  io_uring/zcrx: add copy fallback
  io_uring/zcrx: throttle receive requests
  io_uring/zcrx: set pp memory provider for an rx queue
  io_uring/zcrx: add io_recvzc request
  io_uring/zcrx: dma-map area for the device
  io_uring/zcrx: implement zerocopy receive pp memory provider
  io_uring/zcrx: grab a net device
  io_uring/zcrx: add io_zcrx_area
  io_uring/zcrx: add interface queue and refill queue