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Date: Thu, 6 Dec 2001 14:32:18 -0800
From: Larry McVoy <lm@bitmover.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Larry McVoy <lm@bitmover.com>, Daniel Phillips <phillips@bonn-fries.net>,
        "David S. Miller" <davem@redhat.com>, davidel@xmailserver.org,
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Subject: Re: SMP/cc Cluster description
Message-ID: <20011206143218.O27589@work.bitmover.com>
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In-Reply-To: <E16C79j-0003LO-00@the-village.bc.nu>; from alan@lxorguk.ukuu.org.uk on Thu, Dec 06, 2001 at 10:38:14PM +0000
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On Thu, Dec 06, 2001 at 10:38:14PM +0000, Alan Cox wrote:
> > the hardware's coherency.  No locks in the vfs or fs, that's all done
> > in the mmap/page fault path for sure, but once the data is mapped you
> > aren't dealing with the file system at all.
> 
> ftruncate

I'm not sure what the point is.  We've already agreed that the multiple OS
instances will have synchonization to do for file operations, ftruncate
being one of them.

I thought the question was how N user processes do locking and my answer
stands: exactly like they'd do it on an SMP, with mutex_enter()/exit() on
some portion of the mapped file.  The mapped file is just a chunk of cache
coherent memory.
-- 
---
Larry McVoy            	 lm at bitmover.com           http://www.bitmover.com/lm 
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