linux-kernel - Re: [PATCH] VFS: Pagecache usage optimization on pagesize !=blocksize environment

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Date:	Mon, 26 May 2008 16:20:10 +0900
From:	Hisashi Hifumi <hifumi.hisashi@....ntt.co.jp>
To:	Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] VFS: Pagecache usage optimization on pagesize
  !=blocksize environment


>  But I'm slightly confused that the patch helps because I've always
>thought that mpage_readpage() (which is what we end up calling from
>do_generic_mapping_read()) always reads the whole page. Thus either all
>buffers in the page or none of them are uptodate... So what do I miss
>here?
>
>								Honza

On ext3/4, a file is written through buffer/block. So if a page has multiple 
buffers, buffers can be uptodate partially especially under random write workloads.
See __block_prepare_write and __block_commit_write.

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