From: Matthew Wilcox <matthew@wil.cx>
To: Francis Moreau <francis.moro@gmail.com>
Cc: Andreas Dilger <adilger@sun.com>, linux-fsdevel@vger.kernel.org
Subject: Re: PG_updatodate vs BH_updatodate
Date: Sun, 23 Nov 2008 05:21:24 -0700 [thread overview]
Message-ID: <20081123122124.GH5707@parisc-linux.org> (raw)
In-Reply-To: <m2r652y6yr.fsf@gmail.com>
On Sun, Nov 23, 2008 at 01:14:52PM +0100, Francis Moreau wrote:
> Hello,
>
> Thanks for your answer.
>
> Andreas Dilger <adilger@sun.com> writes:
>
> > There may be multiple buffers on a single page, and in some cases
> > one buffer on a page can be uptodate while another buffer on the
> > same page is not.
>
> Can this really happen ?
Yes.
> Are there any cases where a page can be partially uptodate ?
Consider a filesystem with 1k blocks and a system with a page size of 4k.
You have a buffer_head for each of the four blocks that are being kept
in the page, and you want to track their dirty state independently.
For file data, no this doesn't happen. But for metadata, it happens
quite easily.
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
next prev parent reply other threads:[~2008-11-23 12:21 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-21 22:03 PG_updatodate vs BH_updatodate Francis Moreau
2008-11-23 4:19 ` Andreas Dilger
2008-11-23 12:14 ` Francis Moreau
2008-11-23 12:21 ` Matthew Wilcox [this message]
2008-11-23 20:14 ` Francis Moreau
2008-11-24 15:56 ` Jörn Engel
2008-11-24 16:42 ` Francis Moreau
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