[Qemu-block] [PATCH 3/4] qapi: implement block-dirty-bitmap-remove transaction action

[Vladimir Sementsov-Ogievskiy]

It is used to do transactional movement of the bitmap (which is
possible in conjunction with merge command). Transactional bitmap
movement is needed in scenarios with external snapshot, when we don't
want to leave copy of the bitmap in the base image.

Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
 qapi/transaction.json |  2 ++
 blockdev.c            | 74 +++++++++++++++++++++++++++++++++++++++----
 2 files changed, 70 insertions(+), 6 deletions(-)

diff --git a/qapi/transaction.json b/qapi/transaction.json
index 95edb78227..da95b804aa 100644
--- a/qapi/transaction.json
+++ b/qapi/transaction.json
@@ -45,6 +45,7 @@
 #
 # - @abort: since 1.6
 # - @block-dirty-bitmap-add: since 2.5
+# - @block-dirty-bitmap-remove: since 4.1
 # - @block-dirty-bitmap-clear: since 2.5
 # - @block-dirty-bitmap-enable: since 4.0
 # - @block-dirty-bitmap-disable: since 4.0
@@ -61,6 +62,7 @@
   'data': {
        'abort': 'Abort',
        'block-dirty-bitmap-add': 'BlockDirtyBitmapAdd',
+       'block-dirty-bitmap-remove': 'BlockDirtyBitmap',
        'block-dirty-bitmap-clear': 'BlockDirtyBitmap',
        'block-dirty-bitmap-enable': 'BlockDirtyBitmap',
        'block-dirty-bitmap-disable': 'BlockDirtyBitmap',
diff --git a/blockdev.c b/blockdev.c
index 5b3eef0d3e..0d9aa7f0a1 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2135,6 +2135,46 @@ static void 
block_dirty_bitmap_merge_prepare(BlkActionState *common,
                                                 errp);
 }
 
+static BdrvDirtyBitmap *do_block_dirty_bitmap_remove(
+        const char *node, const char *name, bool release,
+        BlockDriverState **bitmap_bs, Error **errp);
+
+static void block_dirty_bitmap_remove_prepare(BlkActionState *common,
+                                              Error **errp)
+{
+    BlockDirtyBitmap *action;
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    if (action_check_completion_mode(common, errp) < 0) {
+        return;
+    }
+
+    action = common->action->u.block_dirty_bitmap_remove.data;
+
+    state->bitmap = do_block_dirty_bitmap_remove(action->node, action->name,
+                                                 false, &state->bs, errp);
+    if (state->bitmap) {
+        bdrv_dirty_bitmap_hide(state->bitmap);
+    }
+}
+
+static void block_dirty_bitmap_remove_abort(BlkActionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    bdrv_dirty_bitmap_unhide(state->bitmap);
+}
+
+static void block_dirty_bitmap_remove_commit(BlkActionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    bdrv_release_dirty_bitmap(state->bs, state->bitmap);
+}
+
 static void abort_prepare(BlkActionState *common, Error **errp)
 {
     error_setg(errp, "Transaction aborted using Abort action");
@@ -2212,6 +2252,12 @@ static const BlkActionOps actions[] = {
         .commit = block_dirty_bitmap_free_backup,
         .abort = block_dirty_bitmap_restore,
     },
+    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_REMOVE] = {
+        .instance_size = sizeof(BlockDirtyBitmapState),
+        .prepare = block_dirty_bitmap_remove_prepare,
+        .commit = block_dirty_bitmap_remove_commit,
+        .abort = block_dirty_bitmap_remove_abort,
+    },
     /* Where are transactions for MIRROR, COMMIT and STREAM?
      * Although these blockjobs use transaction callbacks like the backup job,
      * these jobs do not necessarily adhere to transaction semantics.
@@ -2870,20 +2916,21 @@ void qmp_block_dirty_bitmap_add(const char *node, const 
char *name,
     bdrv_dirty_bitmap_set_persistence(bitmap, persistent);
 }
 
-void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
-                                   Error **errp)
+static BdrvDirtyBitmap *do_block_dirty_bitmap_remove(
+        const char *node, const char *name, bool release,
+        BlockDriverState **bitmap_bs, Error **errp)
 {
     BlockDriverState *bs;
     BdrvDirtyBitmap *bitmap;
 
     bitmap = block_dirty_bitmap_lookup(node, name, &bs, errp);
     if (!bitmap || !bs) {
-        return;
+        return NULL;
     }
 
     if (bdrv_dirty_bitmap_check(bitmap, BDRV_BITMAP_BUSY | BDRV_BITMAP_RO,
                                 errp)) {
-        return;
+        return NULL;
     }
 
     if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
@@ -2893,13 +2940,28 @@ void qmp_block_dirty_bitmap_remove(const char *node, 
const char *name,
         aio_context_acquire(aio_context);
         bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err);
         aio_context_release(aio_context);
+
         if (local_err != NULL) {
             error_propagate(errp, local_err);
-            return;
+            return NULL;
         }
     }
 
-    bdrv_release_dirty_bitmap(bs, bitmap);
+    if (release) {
+        bdrv_release_dirty_bitmap(bs, bitmap);
+    }
+
+    if (bitmap_bs) {
+        *bitmap_bs = bs;
+    }
+
+    return bitmap;
+}
+
+void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
+                                   Error **errp)
+{
+    do_block_dirty_bitmap_remove(node, name, true, NULL, errp);
 }
 
 /**
-- 
2.18.0