io_uring: fix OP_ASYNC_CANCEL across tasks

IORING_OP_ASYNC_CANCEL tries io-wq cancellation only for current task.
If it fails go over tctx_list and try it out for every single tctx.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -5667,8 +5667,47 @@ static int io_async_cancel_prep(struct io_kiocb *req,
 static int io_async_cancel(struct io_kiocb *req, unsigned int issue_flags)
 {
 	struct io_ring_ctx *ctx = req->ctx;
+	u64 sqe_addr = req->cancel.addr;
+	struct io_tctx_node *node;
+	int ret;
+
+	/* tasks should wait for their io-wq threads, so safe w/o sync */
+	ret = io_async_cancel_one(req->task->io_uring, sqe_addr, ctx);
+	spin_lock_irq(&ctx->completion_lock);
+	if (ret != -ENOENT)
+		goto done;
+	ret = io_timeout_cancel(ctx, sqe_addr);
+	if (ret != -ENOENT)
+		goto done;
+	ret = io_poll_cancel(ctx, sqe_addr);
+	if (ret != -ENOENT)
+		goto done;
+	spin_unlock_irq(&ctx->completion_lock);
+
+	/* slow path, try all io-wq's */
+	io_ring_submit_lock(ctx, !(issue_flags & IO_URING_F_NONBLOCK));
+	ret = -ENOENT;
+	list_for_each_entry(node, &ctx->tctx_list, ctx_node) {
+		struct io_uring_task *tctx = node->task->io_uring;
 
-	io_async_find_and_cancel(ctx, req, req->cancel.addr, 0);
+		if (!tctx || !tctx->io_wq)
+			continue;
+		ret = io_async_cancel_one(tctx, req->cancel.addr, ctx);
+		if (ret != -ENOENT)
+			break;
+	}
+	io_ring_submit_unlock(ctx, !(issue_flags & IO_URING_F_NONBLOCK));
+
+	spin_lock_irq(&ctx->completion_lock);
+done:
+	io_cqring_fill_event(req, ret);
+	io_commit_cqring(ctx);
+	spin_unlock_irq(&ctx->completion_lock);
+	io_cqring_ev_posted(ctx);
+
+	if (ret < 0)
+		req_set_fail_links(req);
+	io_put_req(req);
 	return 0;
 }