Merge tag 'io_uring-5.13-2021-05-14' of git://git.kernel.dk/linux-block

Pull io_uring fixes from Jens Axboe:
 "Just a few minor fixes/changes:

   - Fix issue with double free race for linked timeout completions

   - Fix reference issue with timeouts

   - Remove last few places that make SQPOLL special, since it's just an
     io thread now.

   - Bump maximum allowed registered buffers, as we don't allocate as
     much anymore"

* tag 'io_uring-5.13-2021-05-14' of git://git.kernel.dk/linux-block:
  io_uring: increase max number of reg buffers
  io_uring: further remove sqpoll limits on opcodes
  io_uring: fix ltout double free on completion race
  io_uring: fix link timeout refs

fs/io_uring.c

@@ -100,6 +100,8 @@
 #define IORING_MAX_RESTRICTIONS	(IORING_RESTRICTION_LAST + \
 				 IORING_REGISTER_LAST + IORING_OP_LAST)
 
+#define IORING_MAX_REG_BUFFERS	(1U << 14)
+
 #define SQE_VALID_FLAGS	(IOSQE_FIXED_FILE|IOSQE_IO_DRAIN|IOSQE_IO_LINK|	\
 				IOSQE_IO_HARDLINK | IOSQE_ASYNC | \
 				IOSQE_BUFFER_SELECT)
@@ -4035,7 +4037,7 @@ static int io_epoll_ctl_prep(struct io_kiocb *req,
 #if defined(CONFIG_EPOLL)
 	if (sqe->ioprio || sqe->buf_index)
 		return -EINVAL;
-	if (unlikely(req->ctx->flags & (IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL)))
+	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
 		return -EINVAL;
 
 	req->epoll.epfd = READ_ONCE(sqe->fd);
@@ -4150,7 +4152,7 @@ static int io_fadvise(struct io_kiocb *req, unsigned int issue_flags)
 
 static int io_statx_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
-	if (unlikely(req->ctx->flags & (IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL)))
+	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
 		return -EINVAL;
 	if (sqe->ioprio || sqe->buf_index)
 		return -EINVAL;
@@ -5827,8 +5829,6 @@ static int io_async_cancel(struct io_kiocb *req, unsigned int issue_flags)
 static int io_rsrc_update_prep(struct io_kiocb *req,
 				const struct io_uring_sqe *sqe)
 {
-	if (unlikely(req->ctx->flags & IORING_SETUP_SQPOLL))
-		return -EINVAL;
 	if (unlikely(req->flags & (REQ_F_FIXED_FILE | REQ_F_BUFFER_SELECT)))
 		return -EINVAL;
 	if (sqe->ioprio || sqe->rw_flags)
@@ -6354,19 +6354,20 @@ static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer)
 	 * We don't expect the list to be empty, that will only happen if we
 	 * race with the completion of the linked work.
 	 */
-	if (prev && req_ref_inc_not_zero(prev))
+	if (prev) {
 		io_remove_next_linked(prev);
-	else
-		prev = NULL;
+		if (!req_ref_inc_not_zero(prev))
+			prev = NULL;
+	}
 	spin_unlock_irqrestore(&ctx->completion_lock, flags);
 
 	if (prev) {
 		io_async_find_and_cancel(ctx, req, prev->user_data, -ETIME);
 		io_put_req_deferred(prev, 1);
+		io_put_req_deferred(req, 1);
 	} else {
 		io_req_complete_post(req, -ETIME, 0);
 	}
-	io_put_req_deferred(req, 1);
 	return HRTIMER_NORESTART;
 }
 
@@ -8390,7 +8391,7 @@ static int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
 
 	if (ctx->user_bufs)
 		return -EBUSY;
-	if (!nr_args || nr_args > UIO_MAXIOV)
+	if (!nr_args || nr_args > IORING_MAX_REG_BUFFERS)
 		return -EINVAL;
 	ret = io_rsrc_node_switch_start(ctx);
 	if (ret)