[Qemu-block] [PATCH v4 16/17] qapi: Expose new qcow2 overlap check options

[Max Reitz]

Expose the two new options for controlling the memory usage of the
overlap check implementation via QAPI.

Signed-off-by: Max Reitz <address@hidden>
---
 qapi/block-core.json | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 1c17224..99456e6 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1509,6 +1509,39 @@
             'mode':  'Qcow2OverlapCheckMode' } }
 
 ##
+# @Qcow2OverlapStructures
+#
+# Contains options for controlling the behavior of the metadata overlap
+# prevention structures.
+#
+# The primary structure used for overlap check and prevention is a bitmap
+# (actually a bytemap) which has one entry per cluster designating the type(s)
+# of metadata it contains. In order to save memory, there is an RLE-like
+# representation of this bitmap, too.
+#
+# The whole array of clusters is chunked. The RLE representation of one chunk
+# is converted to the equivalent bitmap whenever a cluster in the chunk is
+# accessed. The bitmaps are kept for a limited number of chunks (as a cache). 
On
+# cache eviction, the bitmap is converted back to RLE again.
+#
+# @bitmap-size:      #optional size (in bytes) of the bitmap cache, defaults to
+#                    64 kB
+#
+# @total-size-limit: #optional maximum total size (in bytes) of all the 
metadata
+#                    overlap prevention data structures combined; if this limit
+#                    is exceeded, a QCOW2_OVERLAP_CHECK_MEMORY_LIMIT_REACHED
+#                    event will be emitted and some parts of the image may no
+#                    longer be protected against erroneous overwriting of
+#                    metadata by (meta)data of a different kind. Defaults to
+#                    SIZE_MAX.
+#
+# Since: 2.4
+##
+{ 'type': 'Qcow2OverlapStructures',
+  'data': { '*bitmap-size':      'int',
+            '*total-size-limit': 'int' } }
+
+##
 # @BlockdevOptionsQcow2
 #
 # Driver specific block device options for qcow2.
@@ -1530,6 +1563,9 @@
 # @overlap-check:         #optional which overlap checks to perform for writes
 #                         to the image, defaults to 'cached' (since 2.2)
 #
+# @overlap-structures:    #optional options for controlling the behavior of the
+#                         metadata overlap prevention structures (since 2.4)
+#
 # @cache-size:            #optional the maximum total size of the L2 table and
 #                         refcount block caches in bytes (since 2.2)
 #
@@ -1548,6 +1584,7 @@
             '*pass-discard-snapshot': 'bool',
             '*pass-discard-other': 'bool',
             '*overlap-check': 'Qcow2OverlapChecks',
+            '*overlap-structures': 'Qcow2OverlapStructures',
             '*cache-size': 'int',
             '*l2-cache-size': 'int',
             '*refcount-cache-size': 'int' } }
-- 
2.3.7