[PATCH 1/2] io_uring/waitid: have io_waitid_complete() remove wait queue entry

[Jens Axboe <axboe@kernel.dk>]

Both callers of this need the entry potentially removed, so shift the
removal into the completion side and kill it from the two callers.

While at it, add a helper for removing the wait_queue_entry based
on the passed in io_kiocb.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 io_uring/waitid.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/io_uring/waitid.c b/io_uring/waitid.c
index f25110fb1b12..ebe3769c54dc 100644
--- a/io_uring/waitid.c
+++ b/io_uring/waitid.c
@@ -109,6 +109,22 @@ static int io_waitid_finish(struct io_kiocb *req, int ret)
 	return ret;
 }
 
+static void io_waitid_remove_wq(struct io_kiocb *req)
+{
+	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+	struct wait_queue_head *head;
+
+	head = READ_ONCE(iw->head);
+	if (head) {
+		struct io_waitid_async *iwa = req->async_data;
+
+		iw->head = NULL;
+		spin_lock_irq(&head->lock);
+		list_del_init(&iwa->wo.child_wait.entry);
+		spin_unlock_irq(&head->lock);
+	}
+}
+
 static void io_waitid_complete(struct io_kiocb *req, int ret)
 {
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
@@ -119,6 +135,7 @@ static void io_waitid_complete(struct io_kiocb *req, int ret)
 	lockdep_assert_held(&req->ctx->uring_lock);
 
 	hlist_del_init(&req->hash_node);
+	io_waitid_remove_wq(req);
 
 	ret = io_waitid_finish(req, ret);
 	if (ret < 0)
@@ -129,7 +146,8 @@ static void io_waitid_complete(struct io_kiocb *req, int ret)
 static bool __io_waitid_cancel(struct io_kiocb *req)
 {
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
-	struct io_waitid_async *iwa = req->async_data;
+
+	lockdep_assert_held(&req->ctx->uring_lock);
 
 	/*
 	 * Mark us canceled regardless of ownership. This will prevent a
@@ -141,9 +159,6 @@ static bool __io_waitid_cancel(struct io_kiocb *req)
 	if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
 		return false;
 
-	spin_lock_irq(&iw->head->lock);
-	list_del_init(&iwa->wo.child_wait.entry);
-	spin_unlock_irq(&iw->head->lock);
 	io_waitid_complete(req, -ECANCELED);
 	io_req_queue_tw_complete(req, -ECANCELED);
 	return true;
@@ -209,8 +224,7 @@ static void io_waitid_cb(struct io_kiocb *req, io_tw_token_t tw)
 				io_waitid_drop_issue_ref(req);
 				return;
 			}
-
-			remove_wait_queue(iw->head, &iwa->wo.child_wait);
+			/* fall through to complete, will kill waitqueue */
 		}
 	}
 
-- 
2.51.0