[RFC PATCH v2 0/3] io_uring: Add sendto(2) and recvfrom(2) support

[Ammar Faizi <ammarfaizi2@gmail.com>]

Hello,

This RFC patchset adds sendto(2) and recvfrom(2) support for io_uring.
It also addresses an issue in the liburing GitHub repository [1].


## Motivations:
1) By using `sendto()` and `recvfrom()` we can make the submission
   simpler compared to always using `sendmsg()` and `recvmsg()` from
   the userspace.

2) There is a historical patch that tried to add the same
   functionality, but did not end up being applied. [2]

On Tue, 7 Jul 2020 12:29:18 -0600, Jens Axboe <axboe@kernel.dk> wrote:
> In a private conversation with the author, a good point was brought
> up that the sendto/recvfrom do not require an allocation of an async
> context, if we need to defer or go async with the request. I think
> that's a major win, to be honest. There are other benefits as well
> (like shorter path), but to me, the async less part is nice and will
> reduce overhead


## Changes summary
There are 3 patches in this series.

PATCH 1/3 renames io_recv to io_recvfrom and io_send to io_sendto.
Note that

    send(sockfd, buf, len, flags);

  is equivalent to

    sendto(sockfd, buf, len, flags, NULL, 0);

and
    recv(sockfd, buf, len, flags);

  is equivalent to

    recvfrom(sockfd, buf, len, flags, NULL, NULL);

So it is saner to have `send` and `recv` directed to `sendto` and
`recvfrom` instead of the opposite with respect to the name.


PATCH 2/3 makes `move_addr_to_user()` be a non static function. This
function lives in net/socket.c, we need to call this from io_uring
to add `recvfrom()` support for liburing. Added net files maintainers
to the CC list.

PATCH 3/3 adds `sendto(2)` and `recvfrom(2)` support for io_uring.
Added two new opcodes: IORING_OP_SENDTO and IORING_OP_RECVFROM.


## How to test

This patchset is based on "for-next" branch commit:

  bb3294e22482db4b7ec7cfbb2d0f5b53c1adcf86 ("Merge branch 'for-5.17/drivers' into for-next")

It is also available in the Git repository at:

  https://github.com/ammarfaizi2/linux-block ammarfaizi2/linux-block/io_uring-recvfrom-sendto


I also added the liburing support and test. The liburing support is
based on "xattr-getdents64" branch commit:

  55a9bf979f27f3a5c9f456f26dcfe16c4791667b ("src/include/liburing.h: style cleanups")

It is available in the Git repository at:

  https://github.com/ammarfaizi2/liburing sendto-recvfrom

---
v2:
  - Rebased the work, now this patchset is based on commit
    bb3294e22482db4b7ec ("Merge branch 'for-5.17/drivers' into
    for-next").

  - In `io_recvfrom()`, mark the error check of `move_addr_to_user()`
    call as unlikely.

  - Fix build error when CONFIG_NET is undefined.

  - Update liburing test (the branch is still the same, just force
    pushed).

  - Added Nugra to CC list (tester).

---
RFC v1: https://lore.kernel.org/io-uring/20211230013154.102910-1-ammar.faizi@intel.com/
Link: https://github.com/axboe/liburing/issues/397 [1]
Link: https://lore.kernel.org/io-uring/a2399c89-2c45-375c-7395-b5caf556ec3d@kernel.dk/ [2]
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Cc: Nugra <richiisei@gmail.com>
Signed-off-by: Ammar Faizi <ammarfaizi2@gmail.com>
---
Ammar Faizi (3):
  io_uring: Rename `io_{send,recv}` to `io_{sendto,recvfrom}`
  net: Make `move_addr_to_user()` be a non static function
  io_uring: Add `sendto(2)` and `recvfrom(2)` support

 fs/io_uring.c                 | 92 +++++++++++++++++++++++++++++++----
 include/linux/socket.h        |  2 +
 include/uapi/linux/io_uring.h |  2 +
 net/socket.c                  |  4 +-
 4 files changed, 88 insertions(+), 12 deletions(-)


base-commit: bb3294e22482db4b7ec7cfbb2d0f5b53c1adcf86
-- 
2.32.0