Re: [PATCH] pnfs: do not reset to mds if wb_offset != wb_pgbase

[Benny Halevy <bhalevy@tonian.com>]

On 2013-03-27 14:19, Benny Halevy wrote:
> On 2013-03-19 22:28, Fred Isaman wrote:
>> On Tue, Mar 19, 2013 at 3:35 PM, Benny Halevy <bhalevy@tonian.com> wrote:
>>> On 2013-03-18 19:04, Fred Isaman wrote:
>>>> A problem case is if the layout ends within the page request, which
>>>> can happen due to the misalignment.
>>>
>>> First, the file layout currently supports only whole file layouts so I don't see
>>> how that's a problem.
>>> Regardless, I'd rather trim the layout segment to PAGE_SIZE boundaries
>>> and get a new layout from the page aligned offset and on with minlength = PAGE_SIZE
>>> (as we do today).
>>>
>>> Benny
>>>
>>
>> Yes, but consider....
>>
>> let P = PAGE_SIZE
>>
>> assume you have a layout from 0 to 4P, and you try to do a WRITE from
>> 2P to 6P.  Now if the buffer is not page aligned, one of the nfs_page
>> requests will contain the file's logical 4P offset at a random
>> location within the nfs_page.  What happens then?
> 
> Fred,  Can you please provide a test that reproduces this concern
> so we can verify the system behavior with and without my patch?

Ping...

> 
> Benny
> 
>>
>> Fred
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