qmp: add block-dirty-bitmap-clear

Add bdrv_clear_dirty_bitmap and a matching QMP command,
qmp_block_dirty_bitmap_clear that enables a user to reset
the bitmap attached to a drive.

This allows us to reset a bitmap in the event of a full
drive backup.

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: 1429314609-29776-12-git-send-email-jsnow@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

5 files changed, 86 insertions, 0 deletions

diff --git a/block.c b/block.c
index 9dc5c8cb1a..b7f1f002f3 100644
--- a/block.c
+++ b/block.c
@@ -63,6 +63,7 @@
 struct BdrvDirtyBitmap {
     HBitmap *bitmap;
     BdrvDirtyBitmap *successor;
+    int64_t size;
     char *name;
     bool disabled;
     QLIST_ENTRY(BdrvDirtyBitmap) list;
@@ -5557,6 +5558,7 @@ BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs,
     }
     bitmap = g_new0(BdrvDirtyBitmap, 1);
     bitmap->bitmap = hbitmap_alloc(bitmap_size, ctz32(sector_granularity));
+    bitmap->size = bitmap_size;
     bitmap->name = g_strdup(name);
     bitmap->disabled = false;
     QLIST_INSERT_HEAD(&bs->dirty_bitmaps, bitmap, list);
@@ -5759,6 +5761,12 @@ void bdrv_reset_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap,
     hbitmap_reset(bitmap->bitmap, cur_sector, nr_sectors);
 }
 
+void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap)
+{
+    assert(bdrv_dirty_bitmap_enabled(bitmap));
+    hbitmap_reset(bitmap->bitmap, 0, bitmap->size);
+}
+
 static void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector,
                            int nr_sectors)
 {
diff --git a/blockdev.c b/blockdev.c
index 62d862cf01..5905946f0b 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2079,6 +2079,40 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
     aio_context_release(aio_context);
 }
 
+/**
+ * Completely clear a bitmap, for the purposes of synchronizing a bitmap
+ * immediately after a full backup operation.
+ */
+void qmp_block_dirty_bitmap_clear(const char *node, const char *name,
+                                  Error **errp)
+{
+    AioContext *aio_context;
+    BdrvDirtyBitmap *bitmap;
+    BlockDriverState *bs;
+
+    bitmap = block_dirty_bitmap_lookup(node, name, &bs, &aio_context, errp);
+    if (!bitmap || !bs) {
+        return;
+    }
+
+    if (bdrv_dirty_bitmap_frozen(bitmap)) {
+        error_setg(errp,
+                   "Bitmap '%s' is currently frozen and cannot be modified",
+                   name);
+        goto out;
+    } else if (!bdrv_dirty_bitmap_enabled(bitmap)) {
+        error_setg(errp,
+                   "Bitmap '%s' is currently disabled and cannot be cleared",
+                   name);
+        goto out;
+    }
+
+    bdrv_clear_dirty_bitmap(bitmap);
+
+ out:
+    aio_context_release(aio_context);
+}
+
 int hmp_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
 {
     const char *id = qdict_get_str(qdict, "id");
diff --git a/include/block/block.h b/include/block/block.h
index 035cf7bb4c..12bf145b02 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -479,6 +479,7 @@ void bdrv_set_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap,
                            int64_t cur_sector, int nr_sectors);
 void bdrv_reset_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap,
                              int64_t cur_sector, int nr_sectors);
+void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap);
 void bdrv_dirty_iter_init(BlockDriverState *bs,
                           BdrvDirtyBitmap *bitmap, struct HBitmapIter *hbi);
 void bdrv_set_dirty_iter(struct HBitmapIter *hbi, int64_t offset);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 8a4c7f21fc..e275dc2c94 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1022,6 +1022,20 @@
   'data': 'BlockDirtyBitmap' }
 
 ##
+# @block-dirty-bitmap-clear
+#
+# Clear (reset) a dirty bitmap on the device
+#
+# Returns: nothing on success
+#          If @node is not a valid block device, DeviceNotFound
+#          If @name is not found, GenericError with an explanation
+#
+# Since 2.4
+##
+{ 'command': 'block-dirty-bitmap-clear',
+  'data': 'BlockDirtyBitmap' }
+
+##
 # @block_set_io_throttle:
 #
 # Change I/O throttle limits for a block drive.
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 9b10d3d2e8..213508fe5d 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1364,6 +1364,35 @@ Example:
 EQMP
 
     {
+        .name       = "block-dirty-bitmap-clear",
+        .args_type  = "node:B,name:s",
+        .mhandler.cmd_new = qmp_marshal_input_block_dirty_bitmap_clear,
+    },
+
+SQMP
+
+block-dirty-bitmap-clear
+------------------------
+Since 2.4
+
+Reset the dirty bitmap associated with a node so that an incremental backup
+from this point in time forward will only backup clusters modified after this
+clear operation.
+
+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-clear", "arguments": { "node": "drive0",
+                                                           "name": "bitmap0" } }
+<- { "return": {} }
+
+EQMP
+
+    {
         .name       = "blockdev-snapshot-sync",
         .args_type  = "device:s?,node-name:s?,snapshot-file:s,snapshot-node-name:s?,format:s?,mode:s?",
         .mhandler.cmd_new = qmp_marshal_input_blockdev_snapshot_sync,