linux-kernel - Re: [patch 12/23] invalidate

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Date:	Fri, 04 Aug 2006 15:08:49 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	Andrew Morton <akpm@...l.org>
Cc:	Christoph Hellwig <hch@...radead.org>, gregkh@...e.de,
	linux-kernel@...r.kernel.org, stable@...nel.org, torvalds@...l.org,
	jmforbes@...uxtx.org, zwane@....linux.org.uk, tytso@....edu,
	rdunlap@...otime.net, davej@...hat.com, chuckw@...ntumlinux.com,
	reviews@...cw.f00f.org, alan@...rguk.ukuu.org.uk,
	jes@...ined-monkey.org, jes@....com
Subject: Re: [patch 12/23] invalidate_bdev() speedup

On Fri, 2006-08-04 at 02:04 -0700, Andrew Morton wrote:
> On Fri, 4 Aug 2006 09:50:13 +0100
> Christoph Hellwig <hch@...radead.org> wrote:
> 
> > On Thu, Aug 03, 2006 at 10:39:42PM -0700, Greg KH wrote:
> > > -stable review patch.  If anyone has any objections, please let us know.
> > 
> > This is a feature.  Definitly not -stable material.
> 
> Apparently that regular IPI storm is causing the SGI machines some
> significant problems. 

a tiny performance drop :) If that meets the stable policy.. open
question :)

> It's not the biggest problem we've ever had, but if this patch is wrong,
> the pagecache/buffer_head layer is utterly busted.  And it isn't.


are you sure?

+       struct address_space *mapping = bdev->bd_inode->i_mapping;
+
+       if (mapping->nrpages == 0)
+               return;
+
        invalidate_bh_lrus();

what happens if a bdev used to have pagecache and at some point stops
having that due to page reclaim... will that page reclaim call
invalidate_bh_lrus() ? If not, who will ? If the answer is "nobody", is
that really the right answer?



-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com

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