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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , tariqt@nvidia.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260810175446.3945358-2-dtatulea@nvidia.com> Content-Language: en-US From: Dragos Tatulea In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: FR4P281CA0277.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:e6::9) To CH3PR12MB8728.namprd12.prod.outlook.com (2603:10b6:610:171::12) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PR12MB8728:EE_|SN7PR12MB7785:EE_ X-MS-Office365-Filtering-Correlation-Id: 8399f05f-cc98-4940-b83c-08def7d8d0cd X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|366016|23010399003|18002099003|22082099003|11063799006|56012099006|4143699003|10067099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH3PR12MB8728.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(376014)(7416014)(1800799024)(366016)(23010399003)(18002099003)(22082099003)(11063799006)(56012099006)(4143699003)(10067099003);DIR:OUT;SFP:1101; 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>>>>> + unsigned long id; >>>>> + bool found = false; >>>>> + >>>>> + rcu_read_lock(); >>>>> + xa_for_each(&net_devmem_dmabuf_bindings, id, binding) { >>>>> + if (READ_ONCE(binding->dev) == dev && >>>>> + (!dma_dev || binding->attachment->dev == dma_dev)) { >>>>> + found = true; >>>>> + break; >>>>> + } >>>>> + } >>>>> + rcu_read_unlock(); >>>>> + >>>>> + return found; >>>>> +} >>>>> +EXPORT_SYMBOL_GPL(netdev_has_dmabuf_binding); >>>>> + >>>>> void net_devmem_get_net_iov(struct net_iov *niov) >>>>> { >>>>> net_devmem_dmabuf_binding_get(net_devmem_iov_binding(niov)); >>>>> -- >>>>> 2.54.0 >>>>> >>>> >>>> I think netdev_has_dmabuf_binding() can return false even when there >>>> exists one or more in-flight skbs (e.g., in sk_write_queue) backed by >>>> the txq binding (won't technically be inactive until the final reference >>>> is dropped and the binding is freed)? If so, can this still detect when >>>> it is safe to swap the underlying dma dev? >>>> >>> Oh, good point! I didn't realize that the binding is refcounted and can >>> outlive its xarray slot. >>> >> I can only think of adding another list that tracks bindings for their >> lifetime or between xarray erasure and deletion. Not too happy about it >> though. >> >> There's also the possibility of iterating over dmabufs and their attachment. >> But this requires a function in dmabuf to scan the dmabufs and attachments >> under the internal lock similar to dma_buf_debug_show(). But I don't think >> that will be accepted. So this is even worse. >> >> Thanks, >> Dragos > > I agree, those options aren't great. > > Would it be possible to drop these skbs (based on some comparison with > binding->attachment->dev) in validate_xmit_unreadable_skb()? Not sure if > we have enough context at that point in the TX path? > Even if we would, I wouldn't do it... > tbh I'd lean towards your idea of adding a new lifetime list, if there > isn't a better way. > Ok. Will implement the lifetime list (or xarray) if I can't come up with something better until then. Thanks, Dragos