linux-kernel - Re: [00/17] Large Blocksize Support V3

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Message-ID: <4630AEBC.4000002@argo.co.il>
Date:	Thu, 26 Apr 2007 16:53:00 +0300
From:	Avi Kivity <avi@...o.co.il>
To:	David Chinner <dgc@....com>
CC:	Nick Piggin <nickpiggin@...oo.com.au>,
	Christoph Lameter <clameter@....com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, Mel Gorman <mel@...net.ie>,
	William Lee Irwin III <wli@...omorphy.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Badari Pulavarty <pbadari@...il.com>,
	Maxim Levitsky <maximlevitsky@...il.com>
Subject: Re: [00/17] Large Blocksize Support V3

David Chinner wrote:
> On Thu, Apr 26, 2007 at 05:48:12PM +1000, Nick Piggin wrote:
>   
>> Christoph Lameter wrote:
>>     
>>> On Thu, 26 Apr 2007, Nick Piggin wrote:
>>>
>>>
>>>       
>>>> No I don't want to add another fs layer.
>>>>         
>>> Well maybe you could explain what you want. Preferably without redefining 
>>> the established terms?
>>>       
>> Support for larger buffers than page cache pages.
>>     
>
> The problem with this approach is that it turns around the whole
> way we look at bufferheads. Right now we have well defined 1:n
> mapping of page to bufferheads and so we tpyically lock the
> page first them iterate all the bufferheads on the page.
>
> Going the other way, we need to support m:n which we means
> the buffer has to become the primary interface for the filesystem
> to the page cache. i.e. we need to lock the bufferhead first, then
> iterate all the pages on it. This is messy because the cache indexes
> via pages, not bufferheads. hence a buffer needs to point to all the
> pages in it explicitly, and this leads to interesting issues with
> locking.
>   

Why is it necessary to assume that one filesystem block == one buffer?  
Is it for atomicity, efficiency, or something else?


-- 
error compiling committee.c: too many arguments to function

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