Expose the two new options for controlling the memory usage of the
overlap check implementation via QAPI.
Signed-off-by: Max Reitz <mre...@redhat.com>
---
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
