From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Daniel Stodden <daniel.stodden@citrix.com>
Cc: "Xen-devel@lists.xensource.com" <Xen-devel@lists.xensource.com>,
Jake Wires <Jake.Wires@citrix.com>
Subject: What are the semantics of BLKIF_OP_WRITE_BARRIER?
Date: Thu, 22 Jul 2010 13:41:25 -0700 [thread overview]
Message-ID: <4C48ACF5.209@goop.org> (raw)
What does BLKIF_OP_WRITE_BARRIER mean precisely? Presumably it prevents
writes from being reordered past it. But does it also imply a flush, in
that all previous writes are on stable storage? If not, is there
another operation which does guarantee that? If the backend doesn't
support barriers, is there any other way for a guest to force writes to
stable storage?
How does blktap(2) deal with devices with volatile write caches? Does
it generate its own barriers/flushes/FUA requests to push things out to
stable storage?
Thanks,
J
reply other threads:[~2010-07-22 20:41 UTC|newest]
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