io_uring: don't use complete_post in kbuf

Now we're handling IOPOLL completions more generically, get rid uses of
_post() and send requests through the normal path. It may have some
extra mertis performance wise, but we don't care much as there is a
better interface for selected buffers.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/4deded706587f55b006dc33adf0c13cfc3b2319f.1669310258.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/kbuf.c

@@ -306,14 +306,11 @@ int io_remove_buffers(struct io_kiocb *req, unsigned int issue_flags)
 		if (!bl->buf_nr_pages)
 			ret = __io_remove_buffers(ctx, bl, p->nbufs);
 	}
+	io_ring_submit_unlock(ctx, issue_flags);
 	if (ret < 0)
 		req_set_fail(req);
-
-	/* complete before unlock, IOPOLL may need the lock */
 	io_req_set_res(req, ret, 0);
-	io_req_complete_post(req, 0);
-	io_ring_submit_unlock(ctx, issue_flags);
-	return IOU_ISSUE_SKIP_COMPLETE;
+	return IOU_OK;
 }
 
 int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
@@ -458,13 +455,12 @@ int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
 
 	ret = io_add_buffers(ctx, p, bl);
 err:
+	io_ring_submit_unlock(ctx, issue_flags);
+
 	if (ret < 0)
 		req_set_fail(req);
-	/* complete before unlock, IOPOLL may need the lock */
 	io_req_set_res(req, ret, 0);
-	io_req_complete_post(req, 0);
-	io_ring_submit_unlock(ctx, issue_flags);
-	return IOU_ISSUE_SKIP_COMPLETE;
+	return IOU_OK;
 }
 
 int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)