From f7c79aada82c99552499bc075021128f4a8653a6 Mon Sep 17 00:00:00 2001

From: Paolo Bonzini <pbonzini@redhat.com>

Date: Fri, 18 Oct 2013 08:14:43 +0200

Subject: [PATCH 18/81] docs, qapi: document qemu-img map

RH-Author: Paolo Bonzini <pbonzini@redhat.com>

Message-id: <1382084091-16636-19-git-send-email-pbonzini@redhat.com>

Patchwork-id: 55001

O-Subject: [RHEL 7.0 qemu-kvm PATCH 18/26] docs, qapi: document qemu-img map

Bugzilla: 989646

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

RH-Acked-by: Max Reitz <mreitz@redhat.com>

RH-Acked-by: Kevin Wolf <kwolf@redhat.com>

Eric Blake also requested including the output in qapi-schema.json,

so that it is published through the introspection mechanism.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

(cherry picked from commit facd6e2b5c0217f9d9eeb2ee497dda28009518bd)

---

 qapi-schema.json | 29 +++++++++++++++++++++++++++++

 qemu-img.texi    | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++

 2 files changed, 84 insertions(+)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 qapi-schema.json |   29 ++++++++++++++++++++++++++++

 qemu-img.texi    |   55 ++++++++++++++++++++++++++++++++++++++++++++++++++++++

 2 files changed, 84 insertions(+), 0 deletions(-)

diff --git a/qapi-schema.json b/qapi-schema.json

index 780c6fe..b779458 100644

--- a/qapi-schema.json

+++ b/qapi-schema.json

@@ -795,6 +795,35 @@

 { 'enum': 'BlockDeviceIoStatus', 'data': [ 'ok', 'failed', 'nospace' ] }

 ##

+# @BlockDeviceMapEntry:

+#

+# Entry in the metadata map of the device (returned by "qemu-img map")

+#

+# @start: Offset in the image of the first byte described by this entry

+#         (in bytes)

+#

+# @length: Length of the range described by this entry (in bytes)

+#

+# @depth: Number of layers (0 = top image, 1 = top image's backing file, etc.)

+#         before reaching one for which the range is allocated.  The value is

+#         in the range 0 to the depth of the image chain - 1.

+#

+# @zero: the sectors in this range read as zeros

+#

+# @data: reading the image will actually read data from a file (in particular,

+#        if @offset is present this means that the sectors are not simply

+#        preallocated, but contain actual data in raw format)

+#

+# @offset: if present, the image file stores the data for this range in

+#          raw format at the given offset.

+#

+# Since 1.7

+##

+{ 'type': 'BlockDeviceMapEntry',

+  'data': { 'start': 'int', 'length': 'int', 'depth': 'int', 'zero': 'bool',

+            'data': 'bool', '*offset': 'int' } }

+

+##

 # @BlockDirtyInfo:

 #

 # Block dirty bitmap information.

diff --git a/qemu-img.texi b/qemu-img.texi

index 69f1bda..8364fa1 100644

--- a/qemu-img.texi

+++ b/qemu-img.texi

@@ -213,6 +213,61 @@ To enumerate information about each disk image in the above chain, starting from

 qemu-img info --backing-chain snap2.qcow2

 @end example

+@item map [-f @var{fmt}] [--output=@var{ofmt}] @var{filename}

+

+Dump the metadata of image @var{filename} and its backing file chain.

+In particular, this commands dumps the allocation state of every sector

+of @var{filename}, together with the topmost file that allocates it in

+the backing file chain.

+

+Two option formats are possible.  The default format (@code{human})

+only dumps known-nonzero areas of the file.  Known-zero parts of the

+file are omitted altogether, and likewise for parts that are not allocated

+throughout the chain.  @command{qemu-img} output will identify a file

+from where the data can be read, and the offset in the file.  Each line

+will include four fields, the first three of which are hexadecimal

+numbers.  For example the first line of:

+@example

+Offset          Length          Mapped to       File

+0               0x20000         0x50000         /tmp/overlay.qcow2

+0x100000        0x10000         0x95380000      /tmp/backing.qcow2

+@end example

+@noindent

+means that 0x20000 (131072) bytes starting at offset 0 in the image are

+available in /tmp/overlay.qcow2 (opened in @code{raw} format) starting

+at offset 0x50000 (327680).  Data that is compressed, encrypted, or

+otherwise not available in raw format will cause an error if @code{human}

+format is in use.  Note that file names can include newlines, thus it is

+not safe to parse this output format in scripts.

+

+The alternative format @code{json} will return an array of dictionaries

+in JSON format.  It will include similar information in

+the @code{start}, @code{length}, @code{offset} fields;

+it will also include other more specific information:

+@itemize @minus

+@item

+whether the sectors contain actual data or not (boolean field @code{data};

+if false, the sectors are either unallocated or stored as optimized

+all-zero clusters);

+

+@item

+whether the data is known to read as zero (boolean field @code{zero});

+

+@item

+in order to make the output shorter, the target file is expressed as

+a @code{depth}; for example, a depth of 2 refers to the backing file

+of the backing file of @var{filename}.

+@end itemize

+

+In JSON format, the @code{offset} field is optional; it is absent in

+cases where @code{human} format would omit the entry or exit with an error.

+If @code{data} is false and the @code{offset} field is present, the

+corresponding sectors in the file are not yet in use, but they are

+preallocated.

+

+For more information, consult @file{include/block/block.h} in QEMU's

+source code.

+

 @item snapshot [-l | -a @var{snapshot} | -c @var{snapshot} | -d @var{snapshot} ] @var{filename}

 List, apply, create or delete snapshots in image @var{filename}.

-- 

1.7.1