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Subject: Re: [PATCH 1/5] hisi_acc_vfio_pci: Fixes a memory leak bug
To:     Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>,
        "Jason Gunthorpe" <jgg@nvidia.com>,
        Alex Williamson <alex.williamson@redhat.com>
CC:     "cohuck@redhat.com" <cohuck@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linuxarm@openeuler.org" <linuxarm@openeuler.org>
References: <20220915013157.60771-1-liulongfang@huawei.com>
 <20220915013157.60771-2-liulongfang@huawei.com>
 <20220920103443.72654dd7.alex.williamson@redhat.com>
 <YynsesGyvJl26jDI@nvidia.com> <04a17bfa71c440e8a38cba2337a8c6ac@huawei.com>
From:   liulongfang <liulongfang@huawei.com>
Message-ID: <ad6cd915-89c4-299e-03d2-8caab500809a@huawei.com>
Date:   Wed, 21 Sep 2022 11:13:26 +0800
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On 2022/9/21 1:03, Shameerali Kolothum Thodi wrote:
> 
> 
>> -----Original Message-----
>> From: Jason Gunthorpe [mailto:jgg@nvidia.com]
>> Sent: 20 September 2022 17:38
>> To: Alex Williamson <alex.williamson@redhat.com>
>> Cc: liulongfang <liulongfang@huawei.com>; Shameerali Kolothum Thodi
>> <shameerali.kolothum.thodi@huawei.com>; cohuck@redhat.com;
>> linux-kernel@vger.kernel.org; linuxarm@openeuler.org
>> Subject: Re: [PATCH 1/5] hisi_acc_vfio_pci: Fixes a memory leak bug
>>
>> On Tue, Sep 20, 2022 at 10:34:43AM -0600, Alex Williamson wrote:
>>> On Thu, 15 Sep 2022 09:31:53 +0800
>>> Longfang Liu <liulongfang@huawei.com> wrote:
>>>
>>>> During the stop copy phase of live migration, the driver allocates a
>>>> memory for the migrated data to save the data.
>>>>
>>>> When an exception occurs when the driver reads device data, the
>>>> driver will report an error to qemu and exit the current migration state.
>>>> But this memory is not released, which will lead to a memory leak
>>>> problem.
>>
>> Why isn't it released? The fput() releases it:
>>
>> static int hisi_acc_vf_release_file(struct inode *inode, struct file *filp) {
>> 	struct hisi_acc_vf_migration_file *migf = filp->private_data;
>>
>> 	hisi_acc_vf_disable_fd(migf);
>> 	mutex_destroy(&migf->lock);
>> 	kfree(migf);
>>         ^^^^^^^^^^
>>
>> This patch looks wrong to me.
> 
> That's right. Missed that. Sorry of the oversight.
> 
Yes, fput will call release in ops of file, here will call hisi_acc_vf_release_file
to complete the release operation of migf, so this patch is unnecessary.

But there is another place that needs to be modified:
hisi_acc_vf_disable_fd in hisi_acc_vf_disable_fds is not needed,
because it will have an fput next. Is this correct?

> Thanks,
> Shameer
> 
> .
Thanks,
Longfang.
>