Re: data corruption: revalidating a (removable) hdd/flash on re-insert

Pavel Machek
2008-11-04T21:26:39Z

On Wed 2008-11-05 00:22:51, Michael Tokarev wrote:
> Pavel Machek wrote:
>>>>> Every access to removable media is guarded by this revalidation check.
>>>>> If you don't see these events, you should not trust this reader, and
>>>>> at least never change the media while it is connected.
>>>> This is rather nasty data-corrupter.
>>> Sure, it is.
>>>
>>>> Could we at least blacklist
>>>> broken device, and force revalidation on each close or something like
>>>> that?
>>> What's your idea of revalidation if the hardware does not tell you?
>>> Get an md5 of the disk content? :)
>>
>> Well... you should not eject media while fs is mounted or blockdev is
>> open, correct?
>>
>> So can we simply claim 'media changed' on last close/unmount? Sure,
>> sometimes media was not changed, but that only hurts performance, not
>> correctness... ?
>
> Well, that's what my tiny proggy, which I used here to work around the
> problem, does. It constantly opens/closes the /dev/sdFOO, every 0.5s
> currently (I don't think I will be able to replace a media faster than
> half a second :), in order to catch REMOVALs of media -- because when
> the drive does not see the media anymore, it correctly reports that
> the media has changed...

Ok, so we you need to do is to put it into kernel and activate it
via blacklist...?
Pavel
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