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From f7c79aada82c99552499bc075021128f4a8653a6 Mon Sep 17 00:00:00 2001
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Fri, 18 Oct 2013 08:14:43 +0200
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Subject: [PATCH 18/81] docs, qapi: document qemu-img map
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RH-Author: Paolo Bonzini <pbonzini@redhat.com>
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Message-id: <1382084091-16636-19-git-send-email-pbonzini@redhat.com>
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Patchwork-id: 55001
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O-Subject: [RHEL 7.0 qemu-kvm PATCH 18/26] docs, qapi: document qemu-img map
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Bugzilla: 989646
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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Eric Blake also requested including the output in qapi-schema.json,
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so that it is published through the introspection mechanism.
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit facd6e2b5c0217f9d9eeb2ee497dda28009518bd)
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---
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 qapi-schema.json | 29 +++++++++++++++++++++++++++++
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 qemu-img.texi    | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
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 2 files changed, 84 insertions(+)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 qapi-schema.json |   29 ++++++++++++++++++++++++++++
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 qemu-img.texi    |   55 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
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 2 files changed, 84 insertions(+), 0 deletions(-)
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diff --git a/qapi-schema.json b/qapi-schema.json
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index 780c6fe..b779458 100644
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--- a/qapi-schema.json
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+++ b/qapi-schema.json
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@@ -795,6 +795,35 @@
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 { 'enum': 'BlockDeviceIoStatus', 'data': [ 'ok', 'failed', 'nospace' ] }
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 ##
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+# @BlockDeviceMapEntry:
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+#
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+# Entry in the metadata map of the device (returned by "qemu-img map")
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+#
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+# @start: Offset in the image of the first byte described by this entry
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+#         (in bytes)
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+#
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+# @length: Length of the range described by this entry (in bytes)
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+#
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+# @depth: Number of layers (0 = top image, 1 = top image's backing file, etc.)
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+#         before reaching one for which the range is allocated.  The value is
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+#         in the range 0 to the depth of the image chain - 1.
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+#
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+# @zero: the sectors in this range read as zeros
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+#
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+# @data: reading the image will actually read data from a file (in particular,
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+#        if @offset is present this means that the sectors are not simply
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+#        preallocated, but contain actual data in raw format)
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+#
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+# @offset: if present, the image file stores the data for this range in
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+#          raw format at the given offset.
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+#
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+# Since 1.7
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+##
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+{ 'type': 'BlockDeviceMapEntry',
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+  'data': { 'start': 'int', 'length': 'int', 'depth': 'int', 'zero': 'bool',
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+            'data': 'bool', '*offset': 'int' } }
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+
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+##
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 # @BlockDirtyInfo:
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 #
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 # Block dirty bitmap information.
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diff --git a/qemu-img.texi b/qemu-img.texi
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index 69f1bda..8364fa1 100644
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--- a/qemu-img.texi
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+++ b/qemu-img.texi
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@@ -213,6 +213,61 @@ To enumerate information about each disk image in the above chain, starting from
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 qemu-img info --backing-chain snap2.qcow2
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 @end example
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+@item map [-f @var{fmt}] [--output=@var{ofmt}] @var{filename}
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+
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+Dump the metadata of image @var{filename} and its backing file chain.
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+In particular, this commands dumps the allocation state of every sector
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+of @var{filename}, together with the topmost file that allocates it in
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+the backing file chain.
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+
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+Two option formats are possible.  The default format (@code{human})
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+only dumps known-nonzero areas of the file.  Known-zero parts of the
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+file are omitted altogether, and likewise for parts that are not allocated
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+throughout the chain.  @command{qemu-img} output will identify a file
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+from where the data can be read, and the offset in the file.  Each line
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+will include four fields, the first three of which are hexadecimal
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+numbers.  For example the first line of:
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+@example
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+Offset          Length          Mapped to       File
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+0               0x20000         0x50000         /tmp/overlay.qcow2
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+0x100000        0x10000         0x95380000      /tmp/backing.qcow2
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+@end example
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+@noindent
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+means that 0x20000 (131072) bytes starting at offset 0 in the image are
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+available in /tmp/overlay.qcow2 (opened in @code{raw} format) starting
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+at offset 0x50000 (327680).  Data that is compressed, encrypted, or
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+otherwise not available in raw format will cause an error if @code{human}
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+format is in use.  Note that file names can include newlines, thus it is
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+not safe to parse this output format in scripts.
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+
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+The alternative format @code{json} will return an array of dictionaries
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+in JSON format.  It will include similar information in
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+the @code{start}, @code{length}, @code{offset} fields;
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+it will also include other more specific information:
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+@itemize @minus
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+@item
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+whether the sectors contain actual data or not (boolean field @code{data};
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+if false, the sectors are either unallocated or stored as optimized
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+all-zero clusters);
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+
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+@item
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+whether the data is known to read as zero (boolean field @code{zero});
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+
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+@item
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+in order to make the output shorter, the target file is expressed as
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+a @code{depth}; for example, a depth of 2 refers to the backing file
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+of the backing file of @var{filename}.
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+@end itemize
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+
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+In JSON format, the @code{offset} field is optional; it is absent in
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+cases where @code{human} format would omit the entry or exit with an error.
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+If @code{data} is false and the @code{offset} field is present, the
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+corresponding sectors in the file are not yet in use, but they are
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+preallocated.
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+
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+For more information, consult @file{include/block/block.h} in QEMU's
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+source code.
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+
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 @item snapshot [-l | -a @var{snapshot} | -c @var{snapshot} | -d @var{snapshot} ] @var{filename}
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 List, apply, create or delete snapshots in image @var{filename}.
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-- 
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1.7.1
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