RFR: 8254972: Fix pretouch chunk calculations [v2]

[Thomas Schatzl]

On Thu, 29 Oct 2020 14:18:54 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   sjohanss review
>
> Looks good.

Thanks @kimbarrett @kstefanj for your reviews.

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PR: https://git.openjdk.java.net/jdk/pull/884