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Date:      Sun, 19 Sep 1999 10:10:50 +0200
From:      Poul-Henning Kamp <phk@critter.freebsd.dk>
To:        dg@root.com
Cc:        Greg Lehey <grog@lemis.com>, Matt Dillon <dillon@FreeBSD.org>, 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:  <15064.937728650@critter.freebsd.dk>
In-Reply-To: Your message of "Sun, 19 Sep 1999 00:48:41 PDT." <199909190748.AAA20860@implode.root.com> 

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In message <199909190748.AAA20860@implode.root.com>, David Greenman writes:

>   The general feeling of both myself and Kirk McKusick is that the blocking/
>buffering should be done at the application level and not by the kernel and
>that the block/buffered device should go away.

My position is a little bit more flexible:  I don't care which of
the two interfaces we retain, as long as we only have one and as
long as it isn't buggy (ie: it should return write errors).

The argument for the block device is that it *is* more "unix feel" to
be able to read and write at any byte and with any length.

IFF we want to maintain the block interface, we need to fix the error
return for the write case, but we also need to do a significant amount
of work speeding it up.  It currently is an order of magnitude slower
than the char interface (remember to measure consumed CPU time, not
wall-clock time).

For anyone with a second disk or floppy drive in their system, attempting
to fix the block dev interface is not a very hard problem.

--
Poul-Henning Kamp             FreeBSD coreteam member
phk@FreeBSD.ORG               "Real hackers run -current on their laptop."
FreeBSD -- It will take a long time before progress goes too far!


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