linux-kernel - Re: [PATCH 2/4] x86/Hyper-V: Free hv_panic

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Message-ID: <0105c10b-b546-6d93-bb49-e9a4ce4589f6@gmail.com>
Date:   Thu, 19 Mar 2020 16:12:54 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Wei Liu <wei.liu@...nel.org>
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        liuwe@...rosoft.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, x86@...nel.org,
        michael.h.kelley@...rosoft.com,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        vkuznets@...hat.com
Subject: Re: [PATCH 2/4] x86/Hyper-V: Free hv_panic_page when fail to register
 kmsg dump

Hi Wei:
	Thanks for your review.

On 3/18/2020 1:36 AM, Wei Liu wrote:
> On Tue, Mar 17, 2020 at 06:25:21AM -0700, ltykernel@...il.com wrote:
>> From: Tianyu Lan <Tianyu.Lan@...rosoft.com>
>>
>> If fail to register kmsg dump on Hyper-V platform, hv_panic_page
>> will not be used anywhere. So free and reset it.
>>
>> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
>> ---
>>   drivers/hv/vmbus_drv.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
>> index b56b9fb9bd90..b043efea092a 100644
>> --- a/drivers/hv/vmbus_drv.c
>> +++ b/drivers/hv/vmbus_drv.c
>> @@ -1385,9 +1385,13 @@ static int vmbus_bus_init(void)
>>   			hv_panic_page = (void *)hv_alloc_hyperv_zeroed_page();
>>   			if (hv_panic_page) {
>>   				ret = kmsg_dump_register(&hv_kmsg_dumper);
>> -				if (ret)
>> +				if (ret) {
>>   					pr_err("Hyper-V: kmsg dump register "
>>   						"error 0x%x\n", ret);
>> +					hv_free_hyperv_page(
>> +					    (unsigned long)hv_panic_page);
>> +					hv_panic_page = NULL;
>> +				}
> 
> While this modification looks correct to me, there is a call to free
> hv_panic_page in the err_alloc path. That makes the error handling a bit
> confusing here.
> 
> I think you can just remove that function call in err_alloc path.

OK. Will update in the next version.

> 
> Wei.
> 
>>   			} else
>>   				pr_err("Hyper-V: panic message page memory "
>>   					"allocation failed");
>> -- 
>> 2.14.5
>>