block: add bdrv_measure() API
bdrv_measure() provides a conservative maximum for the size of a new
image. This information is handy if storage needs to be allocated (e.g.
a SAN or an LVM volume) ahead of time.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20170705125738.8777-2-stefanha@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 4bf11e8..c437aa5 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -488,6 +488,31 @@
'*dirty-bitmaps': ['BlockDirtyInfo'] } }
##
+# @BlockMeasureInfo:
+#
+# Image file size calculation information. This structure describes the size
+# requirements for creating a new image file.
+#
+# The size requirements depend on the new image file format. File size always
+# equals virtual disk size for the 'raw' format, even for sparse POSIX files.
+# Compact formats such as 'qcow2' represent unallocated and zero regions
+# efficiently so file size may be smaller than virtual disk size.
+#
+# The values are upper bounds that are guaranteed to fit the new image file.
+# Subsequent modification, such as internal snapshot or bitmap creation, may
+# require additional space and is not covered here.
+#
+# @required: Size required for a new image file, in bytes.
+#
+# @fully-allocated: Image file size, in bytes, once data has been written
+# to all sectors.
+#
+# Since: 2.10
+##
+{ 'struct': 'BlockMeasureInfo',
+ 'data': {'required': 'int', 'fully-allocated': 'int'} }
+
+##
# @query-block:
#
# Get a list of BlockInfo for all virtual block devices.
