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Date:      Mon, 20 Sep 1999 09:12:31 +0800
From:      Peter Wemm <peter@netplex.com.au>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        Poul-Henning Kamp <phk@critter.freebsd.dk>, dg@root.com, Greg Lehey <grog@lemis.com>, cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG
Subject:   Re: User block device access (was: cvs commit: src/sys/miscfs/specfs spec_vnops.c src/sys/sys vnode.h src/sys/kern vfs_subr.c) 
Message-ID:  <19990920011231.91F4F1CA7@overcee.netplex.com.au>
In-Reply-To: Your message of "Sun, 19 Sep 1999 12:20:06 MST." <199909191920.MAA73966@apollo.backplane.com> 

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Matthew Dillon wrote:
> :Matt, remember the discussion here is about "If we only retain
> :one of the interfaces, which should it be then ?"
> :
> :If we retain bdevs, Oracle and similar apps, which are much more
> :common than the potential but practically non-existent apps which
> :rely on bdev caching, would be hit hard by this overhead.
> :
> :--
> :Poul-Henning Kamp             FreeBSD coreteam member
> :phk@FreeBSD.ORG               "Real hackers run -current on their laptop."
> 
>     You are the one arguing to have just one interface, Poul, not me.  I
>     think both are useful.

Yes, but IMHO, at the bio level is the wrong place to do it considering how
much the interface is used and how much complexity it adds. There's also
issues like the fs and vfs code that uses bread*()/ b*write*() etc.
Disabling/crippling block device access for users achieves nothing for the
FS code that uses the same system for metadata and directories (without vmio
enable) and old FS's.

Cheers,
-Peter



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