blkdebug: Add ability to override unmap geometries

Make it easier to simulate various unusual hardware setups (for
example, recent commits 3482b9b and b8d0a98 affect the Dell
Equallogic iSCSI with its 15M preferred and maximum unmap and
write zero sizing, or b2f95fe deals with the Linux loopback
block device having a max_transfer of 64k), by allowing blkdebug
to wrap any other device with further restrictions on various
alignments.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20170429191419.30051-9-eblake@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

qapi/block-core.json

@@ -2434,8 +2434,33 @@
 #
 # @config:          filename of the configuration file
 #
-# @align:           required alignment for requests in bytes,
-#                   must be power of 2, or 0 for default
+# @align:           required alignment for requests in bytes, must be
+#                   positive power of 2, or 0 for default
+#
+# @max-transfer:    maximum size for I/O transfers in bytes, must be
+#                   positive multiple of @align and of the underlying
+#                   file's request alignment (but need not be a power of
+#                   2), or 0 for default (since 2.10)
+#
+# @opt-write-zero:  preferred alignment for write zero requests in bytes,
+#                   must be positive multiple of @align and of the
+#                   underlying file's request alignment (but need not be a
+#                   power of 2), or 0 for default (since 2.10)
+#
+# @max-write-zero:  maximum size for write zero requests in bytes, must be
+#                   positive multiple of @align, of @opt-write-zero, and of
+#                   the underlying file's request alignment (but need not
+#                   be a power of 2), or 0 for default (since 2.10)
+#
+# @opt-discard:     preferred alignment for discard requests in bytes, must
+#                   be positive multiple of @align and of the underlying
+#                   file's request alignment (but need not be a power of
+#                   2), or 0 for default (since 2.10)
+#
+# @max-discard:     maximum size for discard requests in bytes, must be
+#                   positive multiple of @align, of @opt-discard, and of
+#                   the underlying file's request alignment (but need not
+#                   be a power of 2), or 0 for default (since 2.10)
 #
 # @inject-error:    array of error injection descriptions
 #
@@ -2446,7 +2471,9 @@
 { 'struct': 'BlockdevOptionsBlkdebug',
   'data': { 'image': 'BlockdevRef',
             '*config': 'str',
-            '*align': 'int',
+            '*align': 'int', '*max-transfer': 'int32',
+            '*opt-write-zero': 'int32', '*max-write-zero': 'int32',
+            '*opt-discard': 'int32', '*max-discard': 'int32',
             '*inject-error': ['BlkdebugInjectErrorOptions'],
             '*set-state': ['BlkdebugSetStateOptions'] } }