From: Jamie Lokier <jamie@shareable.org>
To: Markus Armbruster <armbru@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
Christoph Hellwig <chellwig@redhat.com>,
qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>,
Gerd Hoffmann <kraxel@redhat.com>, Avi Kivity <avi@redhat.com>
Subject: Re: [Qemu-devel] Re: block: format vs. protocol, and how they stack
Date: Tue, 22 Jun 2010 17:46:06 +0100 [thread overview]
Message-ID: <20100622164606.GE4371@shareable.org> (raw)
In-Reply-To: <m3k4psg99a.fsf@blackfin.pond.sub.org>
Markus Armbruster wrote:
> A possible reason why we currently expose format and protocol at the
> user interface is to avoid stacking there.
Pragmatic solution?: A few generic flags in each stacking module
("format/protocol/transport"), which govern which other modules are
allowed to stack on top or underneath.
For example, vvfat may provide a blockdev-like abstraction, along with
flags STACK_ABOVE_ONLY_RAW | STACK_BELOW_ONLY_DIRECTORY, which means
"raw" and "blkdebug" are allowed above (of course ;-) but other things
like the image formats shouldn't be. And below, it can't stack on a
blockdev-like abstraction, but needs a directory and uses filesystem
operations on it - the thing that Plan9fs needs.
Btw, I think we expose "format" because "virtual disk image file
format" is a useful and meaningful concept to users. When someone
needs to use a .VMDK file, they know it as a "VMDK format file", not
"I must use the VMDK protocol with this file".
-- Jamie
next prev parent reply other threads:[~2010-06-22 16:46 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-18 12:59 [Qemu-devel] block: format vs. protocol, and how they stack Markus Armbruster
2010-06-20 10:51 ` [Qemu-devel] " Avi Kivity
2010-06-21 7:00 ` Markus Armbruster
2010-06-22 16:46 ` Jamie Lokier [this message]
2010-06-21 8:19 ` Kevin Wolf
2010-06-21 13:09 ` Anthony Liguori
2010-06-21 13:30 ` Kevin Wolf
2010-06-21 13:37 ` Anthony Liguori
2010-06-21 14:01 ` Kevin Wolf
2010-06-21 14:51 ` Anthony Liguori
2010-06-21 14:52 ` Anthony Liguori
2010-06-21 15:00 ` Christoph Hellwig
2010-06-21 15:22 ` Paul Brook
2010-06-21 15:37 ` Anthony Liguori
2010-06-21 16:01 ` Christoph Hellwig
2010-06-21 16:09 ` Anthony Liguori
2010-06-21 16:36 ` Markus Armbruster
2010-06-21 16:21 ` Markus Armbruster
2010-06-22 8:32 ` Kevin Wolf
2010-06-22 14:24 ` Markus Armbruster
2010-06-28 10:28 ` Christoph Hellwig
2010-06-22 16:30 ` Jamie Lokier
2010-06-21 15:34 ` Anthony Liguori
2010-06-22 8:10 ` Kevin Wolf
2010-06-22 12:39 ` Anthony Liguori
2010-06-22 12:57 ` Kevin Wolf
2010-06-22 13:07 ` Anthony Liguori
2010-06-21 15:56 ` Markus Armbruster
2010-06-22 8:22 ` Kevin Wolf
2010-06-22 16:40 ` Jamie Lokier
2010-06-22 16:56 ` Daniel P. Berrange
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