[Qemu-devel] [2.3 PATCH v7 08/10] qapi: Add transaction support to block-dirty-bitmap-{add, enable, disable}

[John Snow <jsnow@redhat.com>]

From: Fam Zheng <famz@redhat.com>

This adds three qmp commands to transactions.

Users can stop a dirty bitmap, start backup of it, and start another
dirty bitmap atomically, so that the dirty bitmap is tracked
incrementally and we don't miss any write.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
---
 blockdev.c       | 147 +++++++++++++++++++++++++++++++++++++++++++------------
 qapi-schema.json |   5 +-
 2 files changed, 119 insertions(+), 33 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index adf841a..b98249b 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1497,6 +1497,106 @@ static void drive_backup_abort(BlkTransactionState *common)
     }
 }
 
+static void block_dirty_bitmap_add_prepare(BlkTransactionState *common,
+                                           Error **errp)
+{
+    BlockDirtyBitmapAdd *action;
+
+    action = common->action->block_dirty_bitmap_add;
+    qmp_block_dirty_bitmap_add(action->device, action->name,
+                               action->has_granularity, action->granularity,
+                               errp);
+}
+
+static void block_dirty_bitmap_add_abort(BlkTransactionState *common)
+{
+    BlockDirtyBitmapAdd *action;
+    BdrvDirtyBitmap *bm;
+    BlockDriverState *bs;
+
+    action = common->action->block_dirty_bitmap_add;
+    bs = bdrv_lookup_bs(action->device, NULL, NULL);
+    if (bs) {
+        bm = bdrv_find_dirty_bitmap(bs, action->name);
+        if (bm) {
+            bdrv_release_dirty_bitmap(bs, bm);
+        }
+    }
+}
+
+typedef struct BlockDirtyBitmapState {
+    BlkTransactionState common;
+    BdrvDirtyBitmap *bitmap;
+} BlockDirtyBitmapState;
+
+static BdrvDirtyBitmap *block_dirty_bitmap_lookup(const char *device,
+                                                  const char *name,
+                                                  Error **errp)
+{
+    BlockDriverState *bs;
+    BdrvDirtyBitmap *bitmap;
+    Error *local_err = NULL;
+
+    if (!device) {
+        error_setg(errp, "Device cannot be NULL");
+        return NULL;
+    }
+    if (!name) {
+        error_setg(errp, "Bitmap name cannot be NULL");
+        return NULL;
+    }
+
+    bs = bdrv_lookup_bs(device, NULL, &local_err);
+    if (!bs) {
+        error_propagate(errp, local_err);
+        return NULL;
+    }
+
+    bitmap = bdrv_find_dirty_bitmap(bs, name);
+    if (!bitmap) {
+        error_setg(errp, "Dirty bitmap not found: %s", name);
+        return NULL;
+    }
+
+    return bitmap;
+}
+
+/**
+ * Enable and Disable re-uses the same preparation.
+ */
+static void block_dirty_bitmap_en_toggle_prepare(BlkTransactionState *common,
+                                                 Error **errp)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+    BlockDirtyBitmap *action;
+    Error *local_err = NULL;
+
+    action = common->action->block_dirty_bitmap_enable;
+
+    state->bitmap = block_dirty_bitmap_lookup(action->device,
+                                              action->name,
+                                              &local_err);
+    if (!state->bitmap) {
+        error_propagate(errp, local_err);
+        return;
+    }
+}
+
+static void block_dirty_bitmap_enable_commit(BlkTransactionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+    bdrv_enable_dirty_bitmap(NULL, state->bitmap);
+}
+
+static void block_dirty_bitmap_disable_commit(BlkTransactionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+    bdrv_disable_dirty_bitmap(NULL, state->bitmap);
+}
+
 static void abort_prepare(BlkTransactionState *common, Error **errp)
 {
     error_setg(errp, "Transaction aborted using Abort action");
@@ -1529,6 +1629,21 @@ static const BdrvActionOps actions[] = {
         .prepare  = internal_snapshot_prepare,
         .abort = internal_snapshot_abort,
     },
+    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_ADD] = {
+        .instance_size = sizeof(BlkTransactionState),
+        .prepare = block_dirty_bitmap_add_prepare,
+        .abort = block_dirty_bitmap_add_abort,
+    },
+    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_ENABLE] = {
+        .instance_size = sizeof(BlockDirtyBitmapState),
+        .prepare = block_dirty_bitmap_en_toggle_prepare,
+        .commit = block_dirty_bitmap_enable_commit,
+    },
+    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_DISABLE] = {
+        .instance_size = sizeof(BlockDirtyBitmapState),
+        .prepare = block_dirty_bitmap_en_toggle_prepare,
+        .commit = block_dirty_bitmap_disable_commit,
+    },
 };
 
 /*
@@ -1875,38 +1990,6 @@ void qmp_block_dirty_bitmap_remove(const char *device, const char *name,
     bdrv_release_dirty_bitmap(bs, bitmap);
 }
 
-static BdrvDirtyBitmap *block_dirty_bitmap_lookup(const char *device,
-                                                  const char *name,
-                                                  Error **errp)
-{
-    BlockDriverState *bs;
-    BdrvDirtyBitmap *bitmap;
-    Error *local_err = NULL;
-
-    if (!device) {
-        error_setg(errp, "Device cannot be NULL");
-        return NULL;
-    }
-    if (!name) {
-        error_setg(errp, "Bitmap name cannot be NULL");
-        return NULL;
-    }
-
-    bs = bdrv_lookup_bs(device, NULL, &local_err);
-    if (!bs) {
-        error_propagate(errp, local_err);
-        return NULL;
-    }
-
-    bitmap = bdrv_find_dirty_bitmap(bs, name);
-    if (!bitmap) {
-        error_setg(errp, "Dirty bitmap not found: %s", name);
-        return NULL;
-    }
-
-    return bitmap;
-}
-
 void qmp_block_dirty_bitmap_enable(const char *device, const char *name,
                                    Error **errp)
 {
diff --git a/qapi-schema.json b/qapi-schema.json
index d0926d9..958be35 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1260,7 +1260,10 @@
        'blockdev-snapshot-sync': 'BlockdevSnapshot',
        'drive-backup': 'DriveBackup',
        'abort': 'Abort',
-       'blockdev-snapshot-internal-sync': 'BlockdevSnapshotInternal'
+       'blockdev-snapshot-internal-sync': 'BlockdevSnapshotInternal',
+       'block-dirty-bitmap-add': 'BlockDirtyBitmapAdd',
+       'block-dirty-bitmap-enable': 'BlockDirtyBitmap',
+       'block-dirty-bitmap-disable': 'BlockDirtyBitmap'
    } }
 
 ##
-- 
1.9.3