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Subject: Re: [cygwin] Re: DD bug fails to wipe last 48 sectors of a disk
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From: Thomas Wolff <towo@towo.net>
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Date: Mon, 14 Sep 2020 19:58:51 +0200
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Am 14.09.2020 um 19:09 schrieb Jason Pyeron:
>> From: Hamish McIntyre-Bhatty
>> Sent: Monday, September 14, 2020 12:34 PM
>>
>> On 14/09/2020 17:32, Jason Pyeron wrote:
>>>> -----Original Message-----
>>>> From: Erik Soderquist
>>>> Sent: Monday, September 14, 2020 11:55 AM
>>>>
>>>> On Mon, Sep 14, 2020 at 11:45 AM Hamish McIntyre-Bhatty via Cygwin wrote:
>>>>> Was this ever resolved? I could have sworn I saw some discussion about
>>>>> this but I can't find it in the archives.
>>>> I still have the thread in my local email; a couple viable work
>>>> arounds were provided, but the issue's root cause is on the Windows
>>>> side, so I believe the only real route to a true fix would be via
>>>> Microsoft altering their code.
>>> When accessing with proper (aligned) block size and count I do not encounter the problem - happy to
>> test again.
>>>>> It might also affect ddrescue, I feel.
>>>> I believe you are accurate in this feeling.
> (next time, please attempt to bottom post on this mailing list, moved it where it belongs)
>
>> Could you perhaps try with ddrescue for me please (also has a block size
>> option)? I could try and reproduce myself but without the email thread
>> that will be a challenge.
> Yes, I observed the same result with ddrescue before (bad input = bad behavior, good input = good behavior). The issue, as I have observed it, is if Windows is asked to write a string of blocks, past the end of the drive it will silently fail and not write some of those block BEFORE the end of the drive.
>
> If block size (bs) is a multiple of 4096 (or 512 for most drives) and the count * bs = drive size exactly (as reported by windows) no error.
Where in the code is that handled? Wouldn't it be easy to limit the 
count according to the disk size as a workaround?
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