From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9D2E3C282E1 for ; Fri, 24 May 2019 13:57:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7643520863 for ; Fri, 24 May 2019 13:57:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404070AbfEXN5u (ORCPT ); Fri, 24 May 2019 09:57:50 -0400 Received: from mail-il-dmz.mellanox.com ([193.47.165.129]:60664 "EHLO mellanox.co.il" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2404043AbfEXN5s (ORCPT ); Fri, 24 May 2019 09:57:48 -0400 Received: from Internal Mail-Server by MTLPINE2 (envelope-from parav@mellanox.com) with ESMTPS (AES256-SHA encrypted); 24 May 2019 16:57:45 +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 x4ODvdQt019054; Fri, 24 May 2019 16:57:43 +0300 From: Parav Pandit To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, cohuck@redhat.com, kwankhede@nvidia.com, alex.williamson@redhat.com Cc: cjia@nvidia.com, parav@mellanox.com Subject: [PATCHv4 2/3] vfio/mdev: Avoid creating sysfs remove file on stale device removal Date: Fri, 24 May 2019 08:57:37 -0500 Message-Id: <20190524135738.54862-3-parav@mellanox.com> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20190524135738.54862-1-parav@mellanox.com> References: <20190524135738.54862-1-parav@mellanox.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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; -- 2.19.2