RE: Questin about swap_slot free and invalidate page
From: Dan Magenheimer
Date: Thu Feb 21 2013 - 16:42:52 EST
> From: Ric Mason [mailto:ric.masonn@xxxxxxxxx]
> Subject: Re: Questin about swap_slot free and invalidate page
> On 02/19/2013 11:27 PM, Dan Magenheimer wrote:
> >> From: Ric Mason [mailto:ric.masonn@xxxxxxxxx]
> >>> Hugh is right that handling the possibility of duplicates is
> >>> part of the tmem ABI. If there is any possibility of duplicates,
> >>> the ABI defines how a backend must handle them to avoid data
> >>> coherency issues.
> >>> The kernel implements an in-kernel API which implements the tmem
> >>> ABI. If the frontend and backend can always agree that duplicate
> >> Which ABI in zcache implement that?
> > https://oss.oracle.com/projects/tmem/dist/documentation/api/tmemspec-v001.pdf
> > The in-kernel APIs are frontswap and cleancache. For more information about
> > tmem, see http://lwn.net/Articles/454795/
> But you mentioned that you have in-kernel API which can handle
> duplicate. Do you mean zcache_cleancache/frontswap_put_page? I think
> they just overwrite instead of optional flush the page on the
> second(duplicate) put as mentioned in your tmemspec.
Maybe I am misunderstanding your question... The spec allows
overwrite (and return success) OR flush the page (and return
failure). Zcache does the latter (flush). The code that implements
it is in tmem_put.
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