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Re: IDE write cache and journaling file systems

To: Steve Lord <lord@xxxxxxx>
Subject: Re: IDE write cache and journaling file systems
From: Andi Kleen <ak@xxxxxxx>
Date: Thu, 18 Apr 2002 17:53:14 +0200
Cc: Jim Buzbee <James.Buzbee@xxxxxxxxxxxx>, ak@xxxxxxx, XFS List <linux-xfs@xxxxxxxxxxx>
In-reply-to: <1019144692.10200.8.camel@jen.americas.sgi.com>
References: <3CBEE618.B220A393@echostar.com> <1019144692.10200.8.camel@jen.americas.sgi.com>
Sender: owner-linux-xfs@xxxxxxxxxxx
User-agent: Mutt/
> Andi Kleen was experimenting with the ide cache flushing code in the
> Suse kernel and adding some flushing calls to XFS. We talked about
> the right place to add them, I am not sure if he has tried it yet.

I've tried it and also got it to work in an experimental state, but decided
to rewrite it to use barriers instead. I didn't yet get around to do this 
rewrite. The reason for the rewrite is that just doing the flush slows
it down a lot.

It requires considerable infrastructure not in the standard kernel.

> The simplistic approach is to isolate log writes from other writes
> and ensure they can never share the cache. This is not the optimal
> approach, but should allow filesystem consistency to be maintained
> while keeping the cache on.

I've just defined a new flag for page buf writes and taught the pagebuf
layer how to set queue barriers for that new flag. 


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