qmp: Add block-dirty-bitmap-add and block-dirty-bitmap-remove

The new command pair is added to manage a user created dirty bitmap. The
dirty bitmap's name is mandatory and must be unique for the same device,
but different devices can have bitmaps with the same names.

The granularity is an optional field. If it is not specified, we will
choose a default granularity based on the cluster size if available,
clamped to between 4K and 64K to mirror how the 'mirror' code was
already choosing granularity. If we do not have cluster size info
available, we choose 64K. This code has been factored out into a helper
shared with block/mirror.

This patch also introduces the 'block_dirty_bitmap_lookup' helper,
which takes a device name and a dirty bitmap name and validates the
lookup, returning NULL and setting errp if there is a problem with
either field. This helper will be re-used in future patches in this
series.

The types added to block-core.json will be re-used in future patches
in this series, see:
'qapi: Add transaction support to block-dirty-bitmap-{add, enable, disable}'

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 1429314609-29776-5-git-send-email-jsnow@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

qmp-commands.hx

@@ -1303,6 +1303,62 @@ Example:
                                          "name": "snapshot0" } } ] } }
 <- { "return": {} }
 
+EQMP
+
+    {
+        .name       = "block-dirty-bitmap-add",
+        .args_type  = "node:B,name:s,granularity:i?",
+        .mhandler.cmd_new = qmp_marshal_input_block_dirty_bitmap_add,
+    },
+
+SQMP
+
+block-dirty-bitmap-add
+----------------------
+Since 2.4
+
+Create a dirty bitmap with a name on the device, and start tracking the writes.
+
+Arguments:
+
+- "node": device/node on which to create dirty bitmap (json-string)
+- "name": name of the new dirty bitmap (json-string)
+- "granularity": granularity to track writes with (int, optional)
+
+Example:
+
+-> { "execute": "block-dirty-bitmap-add", "arguments": { "node": "drive0",
+                                                   "name": "bitmap0" } }
+<- { "return": {} }
+
+EQMP
+
+    {
+        .name       = "block-dirty-bitmap-remove",
+        .args_type  = "node:B,name:s",
+        .mhandler.cmd_new = qmp_marshal_input_block_dirty_bitmap_remove,
+    },
+
+SQMP
+
+block-dirty-bitmap-remove
+-------------------------
+Since 2.4
+
+Stop write tracking and remove the dirty bitmap that was created with
+block-dirty-bitmap-add.
+
+Arguments:
+
+- "node": device/node on which to remove dirty bitmap (json-string)
+- "name": name of the dirty bitmap to remove (json-string)
+
+Example:
+
+-> { "execute": "block-dirty-bitmap-remove", "arguments": { "node": "drive0",
+                                                      "name": "bitmap0" } }
+<- { "return": {} }
+
 EQMP
 
     {