From patchwork Tue Apr 30 22:49:36 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Parav Pandit X-Patchwork-Id: 10924263 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 05DB017DF for ; Tue, 30 Apr 2019 22:50:21 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EBA1428A6B for ; Tue, 30 Apr 2019 22:50:20 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DFDA728A75; Tue, 30 Apr 2019 22:50:20 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,UNPARSEABLE_RELAY autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8952528AA1 for ; Tue, 30 Apr 2019 22:50:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727694AbfD3WuT (ORCPT ); Tue, 30 Apr 2019 18:50:19 -0400 Received: from mail-il-dmz.mellanox.com ([193.47.165.129]:45945 "EHLO mellanox.co.il" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727636AbfD3Wt6 (ORCPT ); Tue, 30 Apr 2019 18:49:58 -0400 Received: from Internal Mail-Server by MTLPINE2 (envelope-from parav@mellanox.com) with ESMTPS (AES256-SHA encrypted); 1 May 2019 01:49:55 +0300 Received: from sw-mtx-036.mtx.labs.mlnx (sw-mtx-036.mtx.labs.mlnx [10.12.150.149]) by labmailer.mlnx (8.13.8/8.13.8) with ESMTP id x3UMncnd009688; Wed, 1 May 2019 01:49:53 +0300 From: Parav Pandit To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, kwankhede@nvidia.com, alex.williamson@redhat.com Cc: cjia@nvidia.com, parav@mellanox.com Subject: [PATCHv2 09/10] vfio/mdev: Avoid creating sysfs remove file on stale device removal Date: Tue, 30 Apr 2019 17:49:36 -0500 Message-Id: <20190430224937.57156-10-parav@mellanox.com> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20190430224937.57156-1-parav@mellanox.com> References: <20190430224937.57156-1-parav@mellanox.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP If device is removal is initiated by two threads as below, mdev core attempts to create a syfs remove file on stale device. During this flow, below [1] call trace is observed. cpu-0 cpu-1 ----- ----- mdev_unregister_device() device_for_each_child mdev_device_remove_cb mdev_device_remove user_syscall remove_store() mdev_device_remove() [..] unregister device(); /* not found in list or * active=false. */ sysfs_create_file() ..Call trace Now that mdev core follows correct device removal system of the linux bus model, remove shouldn't fail in normal cases. If it fails, there is no point of creating a stale file or checking for specific error status. kernel: WARNING: CPU: 2 PID: 9348 at fs/sysfs/file.c:327 sysfs_create_file_ns+0x7f/0x90 kernel: CPU: 2 PID: 9348 Comm: bash Kdump: loaded Not tainted 5.1.0-rc6-vdevbus+ #6 kernel: Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b 08/09/2016 kernel: RIP: 0010:sysfs_create_file_ns+0x7f/0x90 kernel: Call Trace: kernel: remove_store+0xdc/0x100 [mdev] kernel: kernfs_fop_write+0x113/0x1a0 kernel: vfs_write+0xad/0x1b0 kernel: ksys_write+0x5a/0xe0 kernel: do_syscall_64+0x5a/0x210 kernel: entry_SYSCALL_64_after_hwframe+0x49/0xbe Signed-off-by: Parav Pandit --- drivers/vfio/mdev/mdev_sysfs.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c index 9f774b91d275..ffa3dcebf201 100644 --- a/drivers/vfio/mdev/mdev_sysfs.c +++ b/drivers/vfio/mdev/mdev_sysfs.c @@ -237,10 +237,8 @@ static ssize_t remove_store(struct device *dev, struct device_attribute *attr, int ret; ret = mdev_device_remove(dev); - if (ret) { - device_create_file(dev, attr); + if (ret) return ret; - } } return count;