io_uring/net: add IORING_ACCEPT_POLL_FIRST flag

Similarly to how polling first is supported for receive, it makes sense to provide the same for accept. An accept operation does a lot of expensive setup, like allocating an fd, a socket/inode, etc. If no connection request is already pending, this is wasted and will just be cleaned up and freed, only to retry via the usual poll trigger. Add IORING_ACCEPT_POLL_FIRST, which tells accept to only initiate the accept request if poll says we have something to accept. Signed-off-by: Jens Axboe <[email protected]>
torvalds · May 9, 2024 · d3da8e9 · d3da8e9
1 parent 7dcc758
commit d3da8e9
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Showing 2 changed files with 9 additions and 1 deletion.
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
@@ -380,6 +380,7 @@ enum io_uring_op {
  */
 #define IORING_ACCEPT_MULTISHOT (1U << 0)
 #define IORING_ACCEPT_DONTWAIT (1U << 1)
+#define IORING_ACCEPT_POLL_FIRST (1U << 2)
 
 /*
  * IORING_OP_MSG_RING command types, stored in sqe->addr

diff --git a/io_uring/net.c b/io_uring/net.c
@@ -1487,6 +1487,9 @@ void io_sendrecv_fail(struct io_kiocb *req)
  req->cqe.flags |= IORING_CQE_F_MORE;
 }
 
+#define ACCEPT_FLAGS (IORING_ACCEPT_MULTISHOT | IORING_ACCEPT_DONTWAIT | \
+ IORING_ACCEPT_POLL_FIRST)
+
 int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
  struct io_accept *accept = io_kiocb_to_cmd(req, struct io_accept);
@@ -1499,7 +1502,7 @@ int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
  accept->flags = READ_ONCE(sqe->accept_flags);
  accept->nofile = rlimit(RLIMIT_NOFILE);
  accept->iou_flags = READ_ONCE(sqe->ioprio);
- if (accept->iou_flags & ~(IORING_ACCEPT_MULTISHOT | IORING_ACCEPT_DONTWAIT))
+ if (accept->iou_flags & ~ACCEPT_FLAGS)
  return -EINVAL;
 
  accept->file_slot = READ_ONCE(sqe->file_index);
@@ -1530,6 +1533,10 @@ int io_accept(struct io_kiocb *req, unsigned int issue_flags)
  struct file *file;
  int ret, fd;
 
+ if (!(req->flags & REQ_F_POLLED) &&
+ accept->iou_flags & IORING_ACCEPT_POLL_FIRST)
+ return -EAGAIN;
+
 retry:
  if (!fixed) {
  fd = __get_unused_fd_flags(accept->flags, accept->nofile);