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

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Message-ID: <013a07f4-140f-4cfe-9315-f3a77e081c8a@linux.intel.com>
Date: Thu, 24 Apr 2025 22:47:52 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: baolu.lu@...ux.intel.com, "Tian, Kevin" <kevin.tian@...el.com>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>,
 "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()

On 4/24/2025 9:37 PM, Jason Gunthorpe wrote:
> On Thu, Apr 24, 2025 at 05:22:48PM +0800, Baolu Lu wrote:
> 
>>>> -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.
>> Hmm, I've considered this. My thought was that xa_store() failure only
>> occurs due to the system running out of memory, and the Linux kernel
>> can't recover from it. In that case, the system is already broken;
>> hence, handling the failure case here doesn't make things better.
> That's not the kernel pattern, you are supposed to unwind correctly in
> those failures
> 
> I think you should not use cleanup.h for something complicated like
> this..

Okay, so let me drop this patch.

Thanks,
baolu