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From 4ae2c1a9deaea0ed095bd960da92d87eda2eb70a Mon Sep 17 00:00:00 2001
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From: John Snow <jsnow@redhat.com>
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Date: Wed, 18 Jul 2018 22:55:05 +0200
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Subject: [PATCH 247/268] docs/interop: add nbd.txt
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RH-Author: John Snow <jsnow@redhat.com>
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Message-id: <20180718225511.14878-30-jsnow@redhat.com>
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Patchwork-id: 81416
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O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH 29/35] docs/interop: add nbd.txt
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Bugzilla: 1207657
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RH-Acked-by: Eric Blake <eblake@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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Describe new metadata namespace: "qemu".
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Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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Message-Id: <20180609151758.17343-7-vsementsov@virtuozzo.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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[eblake: grammar tweaks]
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Signed-off-by: Eric Blake <eblake@redhat.com>
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(cherry picked from commit 3229a835a3c574a8ebc605e007785c4e01c61623)
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Signed-off-by: John Snow <jsnow@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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MAINTAINERS | 1 +
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docs/interop/nbd.txt | 38 ++++++++++++++++++++++++++++++++++++++
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2 files changed, 39 insertions(+)
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create mode 100644 docs/interop/nbd.txt
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diff --git a/MAINTAINERS b/MAINTAINERS
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index a783c92..53d5216 100644
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--- a/MAINTAINERS
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+++ b/MAINTAINERS
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@@ -1927,6 +1927,7 @@ F: nbd/
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F: include/block/nbd*
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F: qemu-nbd.*
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F: blockdev-nbd.c
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+F: docs/interop/nbd.txt
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T: git git://repo.or.cz/qemu/ericb.git nbd
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NFS
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diff --git a/docs/interop/nbd.txt b/docs/interop/nbd.txt
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new file mode 100644
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index 0000000..77b5f45
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--- /dev/null
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+++ b/docs/interop/nbd.txt
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@@ -0,0 +1,38 @@
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+Qemu supports the NBD protocol, and has an internal NBD client (see
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+block/nbd.c), an internal NBD server (see blockdev-nbd.c), and an
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+external NBD server tool (see qemu-nbd.c). The common code is placed
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+in nbd/*.
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+
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+The NBD protocol is specified here:
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+https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md
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+
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+The following paragraphs describe some specific properties of NBD
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+protocol realization in Qemu.
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+
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+= Metadata namespaces =
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+
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+Qemu supports the "base:allocation" metadata context as defined in the
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+NBD protocol specification, and also defines an additional metadata
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+namespace "qemu".
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+
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+
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+== "qemu" namespace ==
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+
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+The "qemu" namespace currently contains only one type of context,
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+related to exposing the contents of a dirty bitmap alongside the
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+associated disk contents. That context has the following form:
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+
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+ qemu:dirty-bitmap:<dirty-bitmap-export-name>
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+
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+Each dirty-bitmap metadata context defines only one flag for extents
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+in reply for NBD_CMD_BLOCK_STATUS:
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+
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+ bit 0: NBD_STATE_DIRTY, means that the extent is "dirty"
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+
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+For NBD_OPT_LIST_META_CONTEXT the following queries are supported
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+in addition to "qemu:dirty-bitmap:<dirty-bitmap-export-name>":
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+
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+* "qemu:" - returns list of all available metadata contexts in the
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+ namespace.
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+* "qemu:dirty-bitmap:" - returns list of all available dirty-bitmap
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+ metadata contexts.
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--
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1.8.3.1
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