On 12/10/2016 09:54, Gonglei (Arei) wrote:
> 
>> -----Original Message-----
>> From: Paolo Bonzini [mailto:paolo.bonz...@gmail.com] On Behalf Of Paolo
>> Bonzini
>> Sent: Wednesday, October 12, 2016 3:41 PM
>> To: Gonglei (Arei); Michael Tokarev; qemu-devel@nongnu.org
>> Cc: qemu-triv...@nongnu.org; Herongguang (Stephen)
>> Subject: Re: [PATCH] mmap-alloc: check before use for ptr pointer
>>
>>
>>
>> On 12/10/2016 09:37, Gonglei (Arei) wrote:
>>>> -----Original Message-----
>>>> From: Michael Tokarev [mailto:m...@tls.msk.ru]
>>>> Sent: Wednesday, October 12, 2016 2:46 PM
>>>> Subject: Re: [PATCH] mmap-alloc: check before use for ptr pointer
>>>>
>>>> 12.10.2016 05:05, Gonglei wrote:
>>>>> If ptr mmap failed, we don't need to do a superfluous
>>>>> calculation for offset variable by ptr (MAP_FAILED).
>>>>
>>>> What's the point?  There's no problem in extra calculation
>>>> if mmap failed, yes, but do we really care?  As of it is now,
>>>> it is more compact and readable, and works.  I think.
>>>>
>>>
>>> I just think it's more reasonable because the ptr is checked after
>>> used. Why do we need a extra calculation?
>>
>> Another reasonable objection (that however your patch doesn't fix) is
>> that align is being used before the assertion:
>>
>>      assert(!(align & (align - 1)));
>>
> 
> Eh, align is used at the beginning of the qemu_ram_mmap()  ;)

Yes, but the assertion is there because align is passed to QEMU_ALIGN_UP.

Paolo

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