[PATCH 2/2] io_uring: unionise ->apoll and ->work

[Pavel Begunkov <asml.silence@gmail.com>]

Save a bit of space by placing ->apoll and ->work ptrs into a union,
making io_kiocb to take 192B (3 cachelines)

note: this patch is just for reference, there are other probably better
ways to save 8B.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index ef4c6e50aa4f..6894a9a5db30 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -597,6 +597,7 @@ enum {
 struct async_poll {
 	struct io_poll_iocb	poll;
 	struct io_poll_iocb	*double_poll;
+	struct io_wq_work	*work;
 };
 
 /*
@@ -658,8 +659,10 @@ struct io_kiocb {
 	 * async armed poll handlers for regular commands.
 	 */
 	struct hlist_node	hash_node;
-	struct async_poll	*apoll;
-	struct io_wq_work	*work;
+	union {
+		struct async_poll	*apoll;
+		struct io_wq_work	*work;
+	};
 	struct callback_head	task_work;
 };
 
@@ -4676,6 +4679,8 @@ static void io_async_task_func(struct callback_head *cb)
 	io_poll_remove_double(req, apoll->double_poll);
 	spin_unlock_irq(&ctx->completion_lock);
 
+	req->work = apoll->work;
+
 	if (!READ_ONCE(apoll->poll.canceled))
 		__io_req_task_submit(req);
 	else
@@ -4765,6 +4770,7 @@ static bool io_arm_poll_handler(struct io_kiocb *req)
 	if (unlikely(!apoll))
 		return false;
 	apoll->double_poll = NULL;
+	apoll->work = req->work;
 
 	req->flags |= REQ_F_POLLED;
 	io_get_req_task(req);
@@ -4785,6 +4791,7 @@ static bool io_arm_poll_handler(struct io_kiocb *req)
 	if (ret) {
 		io_poll_remove_double(req, apoll->double_poll);
 		spin_unlock_irq(&ctx->completion_lock);
+		req->work = apoll->work;
 		kfree(apoll->double_poll);
 		kfree(apoll);
 		return false;
@@ -4826,6 +4833,7 @@ static bool io_poll_remove_one(struct io_kiocb *req)
 		/* non-poll requests have submit ref still */
 		do_complete = __io_poll_remove_one(req, &apoll->poll);
 		if (do_complete) {
+			req->work = apoll->work;
 			io_put_req(req);
 			kfree(apoll->double_poll);
 			kfree(apoll);
@@ -4962,7 +4970,7 @@ static int io_poll_add(struct io_kiocb *req)
 
 	/* ->work is in union with hash_node and others */
 	io_req_clean_work(req);
-	req->flags &= ~REQ_F_WORK_INITIALIZED;
+	req->work = NULL;
 
 	INIT_HLIST_NODE(&req->hash_node);
 	ipt.pt._qproc = io_poll_queue_proc;
-- 
2.24.0