linux-kernel - RE: [PATCH 3/3] iommu/vt-d: Simplify domain_attach

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Message-ID: <BN9PR11MB527619613B8615A94A01FF598C852@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Thu, 24 Apr 2025 07:46:20 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Lu Baolu <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>, "Will
 Deacon" <will@...nel.org>, Robin Murphy <robin.murphy@....com>, "Jason
 Gunthorpe" <jgg@...pe.ca>
CC: "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 3/3] iommu/vt-d: Simplify domain_attach_iommu()

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Wednesday, April 23, 2025 11:10 AM
> 
>  	num = ida_alloc_range(&iommu->domain_ida, FLPT_DEFAULT_DID +
> 1,
>  			      cap_ndoms(iommu->cap) - 1, GFP_KERNEL);
> -	if (num < 0) {
> -		pr_err("%s: No free domain ids\n", iommu->name);

this error message could be kept.

> -		goto err_unlock;
> -	}
> +	if (num < 0)
> +		return num;
> 
>  	info->refcnt	= 1;
>  	info->did	= num;
>  	info->iommu	= iommu;
> -	curr = xa_cmpxchg(&domain->iommu_array, iommu->seq_id,
> -			  NULL, info, GFP_KERNEL);
> -	if (curr) {
> -		ret = xa_err(curr) ? : -EBUSY;
> -		goto err_clear;
> -	}
> 
> -	return 0;
> -
> -err_clear:
> -	ida_free(&iommu->domain_ida, info->did);
> -err_unlock:
> -	kfree(info);
> -	return ret;
> +	return xa_err(xa_store(&domain->iommu_array, iommu->seq_id,
> +			       no_free_ptr(info), GFP_KERNEL));
>  }

no_free_ptr() should be used before successful return. Here xa_store()
could return error but at that point no auto free as no_free_ptr() already
changes 'info' to NULL. then memory leak.