Re: [FYI] tux3: Core changes

[Boaz Harrosh]

On 05/14/2015 03:59 PM, Rik van Riel wrote:
> On 05/14/2015 04:26 AM, Daniel Phillips wrote:
>> Hi Rik,
<>
> 
> The issue is that things like ptrace, AIO, infiniband
> RDMA, and other direct memory access subsystems can take
> a reference to page A, which Tux3 clones into a new page B
> when the process writes it.
> 
> However, while the process now points at page B, ptrace,
> AIO, infiniband, etc will still be pointing at page A.
> 

All these problems can also happen with truncate+new-extending-write

It is the responsibility of the application to take file/range locks
to prevent these page-pinned problems.

> This causes the process and the other subsystem to each
> look at a different page, instead of at shared state,
> causing ptrace to do nothing, AIO and RDMA data to be
> invisible (or corrupted), etc...
> 

Again these problems already exist. Consider each in-place-write
being a truncate (punch hole) + new-write is that not the same?

Cheers
Boaz

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