linux-kernel - RE: [PATCH v6 06/25] iommufd/access: Allow access->ops to be NULL for internal use

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Message-ID: <BN9PR11MB52766D0C0B12F1F10A6BE7548C7BA@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Wed, 25 Jun 2025 03:38:19 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Nicolin Chen <nicolinc@...dia.com>, "jgg@...dia.com" <jgg@...dia.com>,
	"corbet@....net" <corbet@....net>, "will@...nel.org" <will@...nel.org>
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Subject: RE: [PATCH v6 06/25] iommufd/access: Allow access->ops to be NULL for
 internal use

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Saturday, June 14, 2025 3:15 PM
> 
> +int iommufd_access_notify_unmap(struct io_pagetable *iopt, unsigned long
> iova,
> +				unsigned long length)
>  {
>  	struct iommufd_ioas *ioas =
>  		container_of(iopt, struct iommufd_ioas, iopt);
>  	struct iommufd_access *access;
>  	unsigned long index;
> +	int ret = 0;
> 
>  	xa_lock(&ioas->iopt.access_list);
>  	xa_for_each(&ioas->iopt.access_list, index, access) {
> +		if (!access->ops || !access->ops->unmap) {
> +			ret = -EBUSY;
> +			goto unlock;
> +		}

then accesses before this one have been notified to unpin the area
while accesses afterwards are left unnotified.

in the end the unmap fails but with some side-effect incurred.

I'm not sure whether this intermediate state may lead to any undesired
effect later. Just raise it in case you or Jason already thought about it.


>  			/* Something is not responding to unmap requests.
> */
>  			tries++;
> -			if (WARN_ON(tries > 100))
> -				return -EDEADLOCK;
> +			if (WARN_ON(tries > 100)) {
> +				rc = -EDEADLOCK;
> +				goto out_unmapped;
> +			}

this looks an unrelated fix?