linux-kernel - Re: [PATCH -next] scsi: storvsc: Fix unsigned comparison to zero

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Message-ID: <eae60bf8-98b0-254c-8191-553f68850f2f@huawei.com>
Date:   Mon, 27 Dec 2021 12:04:30 +0800
From:   YueHaibing <yuehaibing@...wei.com>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        Long Li <longli@...rosoft.com>
CC:     "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] scsi: storvsc: Fix unsigned comparison to zero

On 2021/12/27 3:49, Michael Kelley (LINUX) wrote:
> From: YueHaibing <yuehaibing@...wei.com> Sent: Friday, December 24, 2021 4:02 AM
>>
>> The unsigned variable sg_count is being assigned a return value
>> from the call to scsi_dma_map() that can return -ENOMEM.
>>
>> Fixes: 743b237c3a7b ("scsi: storvsc: Add Isolation VM support for storvsc driver")
>> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> 
> Good catch!  But I wonder if a simpler fix is to just remove the "unsigned"
> from the declaration of sg_count.  Then we don't need to add the
> sg_cnt local variable.  A little less complexity is almost always better. :-)

Ok， will respine
> 
> Michael
> 
>> ---
>>  drivers/scsi/storvsc_drv.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
>> index ae293600d799..072c752a8c36 100644
>> --- a/drivers/scsi/storvsc_drv.c
>> +++ b/drivers/scsi/storvsc_drv.c
>> @@ -1837,7 +1837,7 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
>>  		unsigned int hvpg_count = HVPFN_UP(offset_in_hvpg + length);
>>  		struct scatterlist *sg;
>>  		unsigned long hvpfn, hvpfns_to_add;
>> -		int j, i = 0;
>> +		int sg_cnt, j, i = 0;
>>
>>  		if (hvpg_count > MAX_PAGE_BUFFER_COUNT) {
>>
>> @@ -1851,11 +1851,11 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
>>  		payload->range.len = length;
>>  		payload->range.offset = offset_in_hvpg;
>>
>> -		sg_count = scsi_dma_map(scmnd);
>> -		if (sg_count < 0)
>> +		sg_cnt = scsi_dma_map(scmnd);
>> +		if (sg_cnt < 0)
>>  			return SCSI_MLQUEUE_DEVICE_BUSY;
>>
>> -		for_each_sg(sgl, sg, sg_count, j) {
>> +		for_each_sg(sgl, sg, sg_cnt, j) {
>>  			/*
>>  			 * Init values for the current sgl entry. hvpfns_to_add
>>  			 * is in units of Hyper-V size pages. Handling the
>> --
>> 2.17.1
> 
> .
>