Conceptual questions about device driver

[Rajat Sharma]

On Fri, Aug 2, 2013 at 2:25 AM, neha naik <nehanaik27 at gmail.com> wrote:
> Hi,
>  I have some conceptual questions about device driver :
>
> 1. Write order fidelity should be maintained when submitting requests from
> device driver to disk below.
>     However, acknowledging these requests it is okay if we don't necessarily
> maintain that order, right?
>

Yes it should not matter as long as application can rely on data being
written is in order of submission.

> 2.  Also i want to understand what the device driver does say if in a
> multiple paged bio, some of the pages get written
>     and some don't, we send the error in the bio. But what about the pages
> it has already written??? It can't possibly
>     do anything about it, right?
>

Applications generally do not make any assumption about data state for
a failed IO, They might retry again, and blocks might get overwritten
again with same data. So it is perfectly fine.

>
> Regards,
> Neha
>
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Rajat