Merge tag 'io_uring-5.8-2020-06-26' of git://git.kernel.dk/linux-block

Pull io_uring fixes from Jens Axboe:
 "Three small fixes:

   - Close a corner case for polled IO resubmission (Pavel)

   - Toss commands when exiting (Pavel)

   - Fix SQPOLL conditional reschedule on perpetually busy submit
     (Xuan)"

* tag 'io_uring-5.8-2020-06-26' of git://git.kernel.dk/linux-block:
  io_uring: fix current->mm NULL dereference on exit
  io_uring: fix hanging iopoll in case of -EAGAIN
  io_uring: fix io_sq_thread no schedule when busy

Author: torvalds

fs/io_uring.c

@@ -890,6 +890,7 @@ static int __io_sqe_files_update(struct io_ring_ctx *ctx,
 				 struct io_uring_files_update *ip,
 				 unsigned nr_args);
 static int io_grab_files(struct io_kiocb *req);
+static void io_complete_rw_common(struct kiocb *kiocb, long res);
 static void io_cleanup_req(struct io_kiocb *req);
 static int io_file_get(struct io_submit_state *state, struct io_kiocb *req,
 		       int fd, struct file **out_file, bool fixed);
@@ -1749,6 +1750,14 @@ static void io_iopoll_queue(struct list_head *again)
 	do {
 		req = list_first_entry(again, struct io_kiocb, list);
 		list_del(&req->list);
+
+		/* shouldn't happen unless io_uring is dying, cancel reqs */
+		if (unlikely(!current->mm)) {
+			io_complete_rw_common(&req->rw.kiocb, -EAGAIN);
+			io_put_req(req);
+			continue;
+		}
+
 		refcount_inc(&req->refs);
 		io_queue_async_work(req);
 	} while (!list_empty(again));
@@ -1994,10 +2003,8 @@ static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2)
 
 	WRITE_ONCE(req->result, res);
 	/* order with io_poll_complete() checking ->result */
-	if (res != -EAGAIN) {
-		smp_wmb();
-		WRITE_ONCE(req->iopoll_completed, 1);
-	}
+	smp_wmb();
+	WRITE_ONCE(req->iopoll_completed, 1);
 }
 
 /*
@@ -5353,9 +5360,6 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 	if ((ctx->flags & IORING_SETUP_IOPOLL) && req->file) {
 		const bool in_async = io_wq_current_is_worker();
 
-		if (req->result == -EAGAIN)
-			return -EAGAIN;
-
 		/* workqueue context doesn't hold uring_lock, grab it now */
 		if (in_async)
 			mutex_lock(&ctx->uring_lock);
@@ -6011,7 +6015,7 @@ static int io_sq_thread(void *data)
 		 * If submit got -EBUSY, flag us as needing the application
 		 * to enter the kernel to reap and flush events.
 		 */
-		if (!to_submit || ret == -EBUSY) {
+		if (!to_submit || ret == -EBUSY || need_resched()) {
 			/*
 			 * Drop cur_mm before scheduling, we can't hold it for
 			 * long periods (or over schedule()). Do this before
@@ -6027,7 +6031,7 @@ static int io_sq_thread(void *data)
 			 * more IO, we should wait for the application to
 			 * reap events and wake us up.
 			 */
-			if (!list_empty(&ctx->poll_list) ||
+			if (!list_empty(&ctx->poll_list) || need_resched() ||
 			    (!time_after(jiffies, timeout) && ret != -EBUSY &&
 			    !percpu_ref_is_dying(&ctx->refs))) {
 				if (current->task_works)