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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7334DC28B2B for ; Fri, 19 Aug 2022 16:34:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353289AbiHSQet (ORCPT ); Fri, 19 Aug 2022 12:34:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353417AbiHSQbh (ORCPT ); Fri, 19 Aug 2022 12:31:37 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 74E0F10C83E; Fri, 19 Aug 2022 09:05:57 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 39CC3B82819; Fri, 19 Aug 2022 16:05:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7438DC433C1; Fri, 19 Aug 2022 16:05:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660925115; bh=/ivNho2yQj5sfZqsb19e7z0EQqZ3kGjam/nOnHZWUhU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OpFi3QsAx2ZSErZ3vZsjoEKSLb3c2Og2cks5V8LmdSou9cLvYdeORxpEXZOT1Pe+D dUp8e6iwkA3uexO5wBfo3MI1XYDIq1lNpJuDWuGLXNIqtq5FfdROprKty55QwpWUSy gO2LeusPOxCoHeZPU8ZCwZ37CyGFCFQdki5boxmA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Christoph Hellwig , Kevin Tian , Max Gurtovoy , Cornelia Huck , Eric Auger , Jason Gunthorpe , Alex Williamson , Sasha Levin Subject: [PATCH 5.10 389/545] vfio: Remove extra put/gets around vfio_device->group Date: Fri, 19 Aug 2022 17:42:39 +0200 Message-Id: <20220819153846.822131744@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220819153829.135562864@linuxfoundation.org> References: <20220819153829.135562864@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jason Gunthorpe [ Upstream commit e572bfb2b6a83b05acd30c03010e661b1967960f ] The vfio_device->group value has a get obtained during vfio_add_group_dev() which gets moved from the stack to vfio_device->group in vfio_group_create_device(). The reference remains until we reach the end of vfio_del_group_dev() when it is put back. Thus anything that already has a kref on the vfio_device is guaranteed a valid group pointer. Remove all the extra reference traffic. It is tricky to see, but the get at the start of vfio_del_group_dev() is actually pairing with the put hidden inside vfio_device_put() a few lines below. A later patch merges vfio_group_create_device() into vfio_add_group_dev() which makes the ownership and error flow on the create side easier to follow. Reviewed-by: Christoph Hellwig Reviewed-by: Kevin Tian Reviewed-by: Max Gurtovoy Reviewed-by: Cornelia Huck Reviewed-by: Eric Auger Signed-off-by: Jason Gunthorpe Message-Id: <1-v3-225de1400dfc+4e074-vfio1_jgg@nvidia.com> Signed-off-by: Alex Williamson Signed-off-by: Sasha Levin --- drivers/vfio/vfio.c | 21 ++------------------- 1 file changed, 2 insertions(+), 19 deletions(-) diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index 2151bc7f87ab..e1b6e1b51d41 100644 --- a/drivers/vfio/vfio.c +++ b/drivers/vfio/vfio.c @@ -546,14 +546,12 @@ struct vfio_device *vfio_group_create_device(struct vfio_group *group, kref_init(&device->kref); device->dev = dev; + /* Our reference on group is moved to the device */ device->group = group; device->ops = ops; device->device_data = device_data; dev_set_drvdata(dev, device); - /* No need to get group_lock, caller has group reference */ - vfio_group_get(group); - mutex_lock(&group->device_lock); list_add(&device->group_next, &group->device_list); group->dev_counter++; @@ -585,13 +583,11 @@ void vfio_device_put(struct vfio_device *device) { struct vfio_group *group = device->group; kref_put_mutex(&device->kref, vfio_device_release, &group->device_lock); - vfio_group_put(group); } EXPORT_SYMBOL_GPL(vfio_device_put); static void vfio_device_get(struct vfio_device *device) { - vfio_group_get(device->group); kref_get(&device->kref); } @@ -841,14 +837,6 @@ int vfio_add_group_dev(struct device *dev, vfio_group_put(group); return PTR_ERR(device); } - - /* - * Drop all but the vfio_device reference. The vfio_device holds - * a reference to the vfio_group, which holds a reference to the - * iommu_group. - */ - vfio_group_put(group); - return 0; } EXPORT_SYMBOL_GPL(vfio_add_group_dev); @@ -928,12 +916,6 @@ void *vfio_del_group_dev(struct device *dev) unsigned int i = 0; bool interrupted = false; - /* - * The group exists so long as we have a device reference. Get - * a group reference and use it to scan for the device going away. - */ - vfio_group_get(group); - /* * When the device is removed from the group, the group suddenly * becomes non-viable; the device has a driver (until the unbind @@ -1008,6 +990,7 @@ void *vfio_del_group_dev(struct device *dev) if (list_empty(&group->device_list)) wait_event(group->container_q, !group->container); + /* Matches the get in vfio_group_create_device() */ vfio_group_put(group); return device_data; -- 2.35.1