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SubjectRe: [PATCH v2] z3fold: fix the potential encode bug in encod_handle
On 2016/10/17 20:03, Vitaly Wool wrote:
> Hi Zhong Jiang,
>
> On Mon, Oct 17, 2016 at 3:58 AM, zhong jiang <zhongjiang@huawei.com> wrote:
>> Hi, Vitaly
>>
>> About the following patch, is it right?
>>
>> Thanks
>> zhongjiang
>> On 2016/10/13 12:02, zhongjiang wrote:
>>> From: zhong jiang <zhongjiang@huawei.com>
>>>
>>> At present, zhdr->first_num plus bud can exceed the BUDDY_MASK
>>> in encode_handle, it will lead to the the caller handle_to_buddy
>>> return the error value.
>>>
>>> The patch fix the issue by changing the BUDDY_MASK to PAGE_MASK,
>>> it will be consistent with handle_to_z3fold_header. At the same time,
>>> change the BUDDY_MASK to PAGE_MASK in handle_to_buddy is better.
> are you seeing problems with the existing code? first_num should wrap around
> BUDDY_MASK and this should be ok because it is way bigger than the number
> of buddies.
>
> ~vitaly
>
> .
>
first_num plus buddies can exceed the BUDDY_MASK. is it right?
(first_num + buddies) & BUDDY_MASK may be a smaller value than first_num.

but (handle - zhdr->first_num) & BUDDY_MASK will return incorrect value
in handle_to_buddy.

Thanks
zhongjiang


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