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From 4ae2c1a9deaea0ed095bd960da92d87eda2eb70a Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Wed, 18 Jul 2018 22:55:05 +0200
Subject: [PATCH 247/268] docs/interop: add nbd.txt

RH-Author: John Snow <jsnow@redhat.com>
Message-id: <20180718225511.14878-30-jsnow@redhat.com>
Patchwork-id: 81416
O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH 29/35] docs/interop: add nbd.txt
Bugzilla: 1207657
RH-Acked-by: Eric Blake <eblake@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Fam Zheng <famz@redhat.com>

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Describe new metadata namespace: "qemu".

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180609151758.17343-7-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: grammar tweaks]
Signed-off-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 3229a835a3c574a8ebc605e007785c4e01c61623)
Signed-off-by: John Snow <jsnow@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 MAINTAINERS          |  1 +
 docs/interop/nbd.txt | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+)
 create mode 100644 docs/interop/nbd.txt

diff --git a/MAINTAINERS b/MAINTAINERS
index a783c92..53d5216 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1927,6 +1927,7 @@ F: nbd/
 F: include/block/nbd*
 F: qemu-nbd.*
 F: blockdev-nbd.c
+F: docs/interop/nbd.txt
 T: git git://repo.or.cz/qemu/ericb.git nbd
 
 NFS
diff --git a/docs/interop/nbd.txt b/docs/interop/nbd.txt
new file mode 100644
index 0000000..77b5f45
--- /dev/null
+++ b/docs/interop/nbd.txt
@@ -0,0 +1,38 @@
+Qemu supports the NBD protocol, and has an internal NBD client (see
+block/nbd.c), an internal NBD server (see blockdev-nbd.c), and an
+external NBD server tool (see qemu-nbd.c). The common code is placed
+in nbd/*.
+
+The NBD protocol is specified here:
+https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md
+
+The following paragraphs describe some specific properties of NBD
+protocol realization in Qemu.
+
+= Metadata namespaces =
+
+Qemu supports the "base:allocation" metadata context as defined in the
+NBD protocol specification, and also defines an additional metadata
+namespace "qemu".
+
+
+== "qemu" namespace ==
+
+The "qemu" namespace currently contains only one type of context,
+related to exposing the contents of a dirty bitmap alongside the
+associated disk contents.  That context has the following form:
+
+    qemu:dirty-bitmap:<dirty-bitmap-export-name>
+
+Each dirty-bitmap metadata context defines only one flag for extents
+in reply for NBD_CMD_BLOCK_STATUS:
+
+    bit 0: NBD_STATE_DIRTY, means that the extent is "dirty"
+
+For NBD_OPT_LIST_META_CONTEXT the following queries are supported
+in addition to "qemu:dirty-bitmap:<dirty-bitmap-export-name>":
+
+* "qemu:" - returns list of all available metadata contexts in the
+            namespace.
+* "qemu:dirty-bitmap:" - returns list of all available dirty-bitmap
+                         metadata contexts.
-- 
1.8.3.1