[PATCH 3/3] io_uring: use REQ_F_MULTI_CQES for multipoll IORING_OP_ADD

[Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>]

leverage REQ_F_MULTI_CQES to suppoort IORING_OP_ADD multishot.

Signed-off-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>
---
 fs/io_uring.c                 | 13 ++++++++++---
 include/uapi/linux/io_uring.h |  5 -----
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a7bd223ce2cc..952ad0ddb2db 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5361,20 +5361,27 @@ static int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
 {
 	struct io_poll_iocb *poll = &req->poll;
 	u32 events, flags;
+	bool multishot = req->flags & REQ_F_MULTI_CQES;
+	u32 update_bits = IORING_POLL_UPDATE_EVENTS |
+		IORING_POLL_UPDATE_USER_DATA;
 
 	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
 		return -EINVAL;
 	if (sqe->ioprio || sqe->buf_index)
 		return -EINVAL;
 	flags = READ_ONCE(sqe->len);
-	if (flags & ~(IORING_POLL_ADD_MULTI | IORING_POLL_UPDATE_EVENTS |
-			IORING_POLL_UPDATE_USER_DATA))
+	/*
+	 * can't set REQ_F_MULTI_CQES with UPDATE flags, otherwise we count
+	 * IO_POLL_ADD(IORING_POLL_UPDATE_*)'s cqe to ctx->cq_extra, which
+	 * we shouldn't
+	 */
+	if ((flags & ~update_bits) || (multishot && (flags & update_bits)))
 		return -EINVAL;
 	events = READ_ONCE(sqe->poll32_events);
 #ifdef __BIG_ENDIAN
 	events = swahw32(events);
 #endif
-	if (!(flags & IORING_POLL_ADD_MULTI))
+	if (!multishot)
 		events |= EPOLLONESHOT;
 	poll->update_events = poll->update_user_data = false;
 	if (flags & IORING_POLL_UPDATE_EVENTS) {
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 303ac8005572..a3cd943b228e 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -166,14 +166,9 @@ enum {
  * POLL_ADD flags. Note that since sqe->poll_events is the flag space, the
  * command flags for POLL_ADD are stored in sqe->len.
  *
- * IORING_POLL_ADD_MULTI	Multishot poll. Sets IORING_CQE_F_MORE if
- *				the poll handler will continue to report
- *				CQEs on behalf of the same SQE.
- *
  * IORING_POLL_UPDATE		Update existing poll request, matching
  *				sqe->addr as the old user_data field.
  */
-#define IORING_POLL_ADD_MULTI	(1U << 0)
 #define IORING_POLL_UPDATE_EVENTS	(1U << 1)
 #define IORING_POLL_UPDATE_USER_DATA	(1U << 2)
 
-- 
1.8.3.1