[Qemu-devel] [PATCH v5 13/17] qcow2/overlaps: Add "memory limit reached" event

[Max Reitz <mreitz@redhat.com>]

Later, a mechanism to set a limit on how much memory may be used for the
overlap prevention structures will be introduced. If that limit is about
to be exceeded, a QMP event should be emitted. This very event is
specified by this patch.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 docs/qmp/qmp-events.txt | 27 +++++++++++++++++++++++++++
 qapi/event.json         | 27 +++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/docs/qmp/qmp-events.txt b/docs/qmp/qmp-events.txt
index d92cc48..00c70d1 100644
--- a/docs/qmp/qmp-events.txt
+++ b/docs/qmp/qmp-events.txt
@@ -279,6 +279,33 @@ Example:
 { "event": "POWERDOWN",
     "timestamp": { "seconds": 1267040730, "microseconds": 682951 } }
 
+QCOW2_OVERLAP_CHECK_MEMORY_LIMIT_REACHED
+----------------------------------------
+
+Emitted by the qcow2 block driver if the preset size limit for the in-memory
+structures for metadata overlap prevention has been reached and an allocation
+of further resources has been denied. This means that it cannot be guaranteed
+that overlap checks will be performed for the specified range; if no range is
+given, no checks can be expected to be performed whatsoever.
+
+Note that this event does not guarantee that no check will be performed in the
+given range (or on the whole image, if no range is given), but only signals the
+possibility that this might be the case. The ability to check the full range or
+a part of it may be restored at any point in time.
+
+Data:
+- "reference": Device name if set; node name otherwise. (json-string)
+- "start":     Offset of the range of clusters (possibly) no longer being
+               checked for writes overlapping with existing metadata.
+               (json-int, optional)
+- "length":    Length of that range in bytes. (json-int, optional)
+
+Example:
+
+{ "event": "QCOW2_OVERLAP_CHECK_MEMORY_LIMIT_REACHED",
+    "data": { "reference": "virtio0", "start": 805306368, "length": 268435456 },
+    "timestamp": { "seconds": 1429331400, "microseconds": 519454 } }
+
 QUORUM_FAILURE
 --------------
 
diff --git a/qapi/event.json b/qapi/event.json
index f0cef01..996cd3d 100644
--- a/qapi/event.json
+++ b/qapi/event.json
@@ -356,3 +356,30 @@
 ##
 { 'event': 'MEM_UNPLUG_ERROR',
   'data': { 'device': 'str', 'msg': 'str' } }
+
+##
+# @QCOW2_OVERLAP_CHECK_MEMORY_LIMIT_REACHED
+#
+# Emitted by the qcow2 block driver if the preset size limit for the in-memory
+# structures for metadata overlap prevention has been reached and an allocation
+# of further resources has been denied. This means that no overlap checks will
+# be performed for the specified range.
+#
+# Note that this event does not guarantee that no check will be performed in the
+# given range (or on the whole image, if no range is given), but only signals
+# the possibility that this might be the case. The ability to check the full
+# range or a part of it may be restored at any point in time.
+#
+# @reference: device name if set; node name otherwise
+#
+# @start:     #optional offset of the range of clusters (possibly) no longer
+#             being checked for writes overlapping with existing metadata
+#
+# @length:    #optional length of that range in bytes
+#
+# Since: 2.5
+##
+{ 'event': 'QCOW2_OVERLAP_CHECK_MEMORY_LIMIT_REACHED',
+  'data': { 'reference': 'str',
+            '*start':    'int',
+            '*length':   'int' } }
-- 
2.4.6