Date: Mon, 21 Nov 2005 15:34:54 -0800
From: Andrew Morton <akpm@osdl.org>
To: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: theonetruekenny@yahoo.com, cel@citi.umich.edu,
       linux-kernel@vger.kernel.org
Subject: Re: infinite loop? with mmap, nfs, pwrite, O_DIRECT
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	<1132612974.8011.12.camel@lade.trondhjem.org>
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Trond Myklebust <trond.myklebust@fys.uio.no> wrote:
>
>  Anything that calls lock_page() should be avoided in O_DIRECT,

Why?

And it's still doing lock_page():

	nfs_file_direct_write()
	->filemap_fdatawrite()
	  ->do_writepages()
	    ->nfs_writepages()
	      ->generic_writepages()
	        ->mpage_writepages()
	          ->lock_page()

> however
>   we should be able to call invalidate_inode_pages() since that doesn't
>   wait on the page lock.

invalidate_inode_pages2() is better.  And using generic_file_direct_IO() is
better still, since it handles mmap coherency and only work upon that part
of the file which is actually undergoing IO.

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