Re: [Qemu-devel] [2.4 PATCH v3 11/19] qmp: add block-dirty-bitmap-clear

[Max Reitz]

On 2015-03-16 at 17:03, John Snow wrote:

On 03/16/2015 04:57 PM, Max Reitz wrote:

On 2015-03-13 at 14:30, John Snow wrote:

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 <js...@redhat.com>
---
  block.c               |  8 ++++++++
  blockdev.c            | 34 ++++++++++++++++++++++++++++++++++
  include/block/block.h |  1 +
  qapi/block-core.json  | 14 ++++++++++++++
  qmp-commands.hx       | 29 +++++++++++++++++++++++++++++
  5 files changed, 86 insertions(+)

diff --git a/block.c b/block.c
index d276fdc..a98ff49 100644
--- a/block.c
+++ b/block.c
@@ -62,6 +62,7 @@
  struct BdrvDirtyBitmap {
      HBitmap *bitmap;
      BdrvDirtyBitmap *successor;
+    int64_t size;
      char *name;
      bool disabled;
      QLIST_ENTRY(BdrvDirtyBitmap) list;
@@ -5460,6 +5461,7 @@ BdrvDirtyBitmap
*bdrv_create_dirty_bitmap(BlockDriverState *bs,
      }
      bitmap = g_new0(BdrvDirtyBitmap, 1);
      bitmap->bitmap = hbitmap_alloc(bitmap_size,
ffs(sector_granularity) - 1);
+    bitmap->size = bitmap_size;
      bitmap->name = g_strdup(name);
      bitmap->disabled = false;
      QLIST_INSERT_HEAD(&bs->dirty_bitmaps, bitmap, list);
@@ -5662,6 +5664,12 @@ 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 361c7a4..cba9f2c 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2051,6 +2051,40 @@ 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) {

Again, you need to release the AIO context here if you're not doing that
in block_dirty_bitmap_lookup() already.

Max

OK. Inclined to fix that in lookup() as I should've to begin with and leave this patch as-is.

With that:

Reviewed-by: Max Reitz <mre...@redhat.com>

--js

+        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 3084b53..10442e0 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 f012de2..50970c4 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1023,6 +1023,20 @@
    '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 72ac72f..db95e89 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1301,6 +1301,35 @@ 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,