From: Chuck Lever <cel@citi.umich.edu>
Subject: Re: NFS directio
Date: Mon, 10 Apr 2006 13:36:10 -0400
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Cc: Olaf Kirch <okir@suse.de>,
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To: Neil Brown <neilb@suse.de>
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Neil Brown wrote:
> I think the case in point was a DVD burner trying to burn an image
> that lived on a NFS filesystem.  It tried to direct-read a reasonable
> fraction of the whole dvd (100Meg?) and had problems.

wow.  first i've heard of this.  was it ever reported to nfs@sf.net?

if you are sure that the problems were directly related to the pagevec 
size logic, then i will get this fixed asap in mainline.

>> the structure of this code was adapted (ie stolen) from other parts of 
>> the kernel that also employ get_user_pages.  you can probably take a 
>> look at other places that employ get_user_pages(), and see how they've 
>> since tackled the issue.
> 
> Looking at fs/direct-io.c, it called get_user_pages is blocks of
> at-most 64 pages.  I suspect a similar thing would be possible for
> nfs.

yep.

we get only a single iocb from the caller.  that may complicate things a 
little, especially in the aio case.

-- 
corporate:	<cel at netapp dot com>
personal:	<chucklever at bigfoot dot com>


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