From eac05c1b5d8d698ef9945c018eb9cb89ee236c29 Mon Sep 17 00:00:00 2001
From: Thanos Makatos <thanos.makatos@onapp.com>
Date: Fri, 4 Mar 2016 18:18:29 +0300
Subject: [PATCH 1/2] document how to extract thin pool metadata

---
 README.md | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/README.md b/README.md
index d23dae5..ce83bd7 100644
--- a/README.md
+++ b/README.md
@@ -130,3 +130,35 @@ Once you've done this you can run the tests with a simple:
 Or specific tests with:
 
     cucumber features/thin_restore -n 'print help'
+
+
+Dump Metadata
+=============
+
+To dump the metadata of a live thin pool, you must first create a snapshot of
+the metadata:
+
+	$ dmsetup message vg001-mythinpool-tpool 0 reserve_metadata_snap
+
+Then, extract the held root from the device mapper's status of the thin pool
+(7th field). This value must be passed to ```thin_dump```.
+
+	$ sudo dmsetup status vg001-mythinpool-tpool
+	0 8192 thin-pool 2 11/1024 1/64 10 rw discard_passdown
+	                                ^
+
+Extract the metadata:
+
+	$ sudo bin/thin_dump -m10 /dev/mapper/vg001-mythinpool_tmeta
+	<superblock uuid="" time="1" transaction="2" data_block_size="128"nr_data_blocks="0">
+	    <device dev_id="1" mapped_blocks="1" transaction="0" creation_time="0" snap_time="1">
+	        <single_mapping origin_block="0" data_block="0" time="0"/>
+	    </device>
+	    <device dev_id="2" mapped_blocks="1" transaction="1" creation_time="1" snap_time="1">
+	        <single_mapping origin_block="0" data_block="0" time="0"/>
+	    </device>
+	</superblock>
+
+Finally, release the root:
+
+	$ dmsetup message vg001-mythinpool-tpool 0 release_metadata_snap

From f162d59bf6da9a3e930f8498e6b41c6029be1920 Mon Sep 17 00:00:00 2001
From: Thanos Makatos <thanos.makatos@onapp.com>
Date: Fri, 4 Mar 2016 18:30:02 +0300
Subject: [PATCH 2/2] no need to supply held root, thin_dump -m will look it up

---
 README.md | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/README.md b/README.md
index ce83bd7..005ae50 100644
--- a/README.md
+++ b/README.md
@@ -140,16 +140,9 @@ the metadata:
 
 	$ dmsetup message vg001-mythinpool-tpool 0 reserve_metadata_snap
 
-Then, extract the held root from the device mapper's status of the thin pool
-(7th field). This value must be passed to ```thin_dump```.
-
-	$ sudo dmsetup status vg001-mythinpool-tpool
-	0 8192 thin-pool 2 11/1024 1/64 10 rw discard_passdown
-	                                ^
-
 Extract the metadata:
 
-	$ sudo bin/thin_dump -m10 /dev/mapper/vg001-mythinpool_tmeta
+	$ sudo bin/thin_dump -m /dev/mapper/vg001-mythinpool_tmeta
 	<superblock uuid="" time="1" transaction="2" data_block_size="128"nr_data_blocks="0">
 	    <device dev_id="1" mapped_blocks="1" transaction="0" creation_time="0" snap_time="1">
 	        <single_mapping origin_block="0" data_block="0" time="0"/>