qed: Implement .bdrv_drain

The "need_check_timer" is used to clear the "NEED_CHECK" flag in the
image header after a grace period once metadata update has finished. In
compliance to the bdrv_drain semantics we should make sure it remains
deleted once .bdrv_drain is called.

We cannot reuse qed_need_check_timer_cb because here it doesn't satisfy
the assertion.  Do the "plug" and "flush" calls manually.

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 1447064214-29930-10-git-send-email-famz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

blockdev.c

@@ -1874,6 +1874,106 @@ static void blockdev_backup_clean(BlkTransactionState *common)
     }
 }
 
+typedef struct BlockDirtyBitmapState {
+    BlkTransactionState common;
+    BdrvDirtyBitmap *bitmap;
+    BlockDriverState *bs;
+    AioContext *aio_context;
+    HBitmap *backup;
+    bool prepared;
+} BlockDirtyBitmapState;
+
+static void block_dirty_bitmap_add_prepare(BlkTransactionState *common,
+                                           Error **errp)
+{
+    Error *local_err = NULL;
+    BlockDirtyBitmapAdd *action;
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    action = common->action->block_dirty_bitmap_add;
+    /* AIO context taken and released within qmp_block_dirty_bitmap_add */
+    qmp_block_dirty_bitmap_add(action->node, action->name,
+                               action->has_granularity, action->granularity,
+                               &local_err);
+
+    if (!local_err) {
+        state->prepared = true;
+    } else {
+        error_propagate(errp, local_err);
+    }
+}
+
+static void block_dirty_bitmap_add_abort(BlkTransactionState *common)
+{
+    BlockDirtyBitmapAdd *action;
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    action = common->action->block_dirty_bitmap_add;
+    /* Should not be able to fail: IF the bitmap was added via .prepare(),
+     * then the node reference and bitmap name must have been valid.
+     */
+    if (state->prepared) {
+        qmp_block_dirty_bitmap_remove(action->node, action->name, &error_abort);
+    }
+}
+
+static void block_dirty_bitmap_clear_prepare(BlkTransactionState *common,
+                                             Error **errp)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+    BlockDirtyBitmap *action;
+
+    action = common->action->block_dirty_bitmap_clear;
+    state->bitmap = block_dirty_bitmap_lookup(action->node,
+                                              action->name,
+                                              &state->bs,
+                                              &state->aio_context,
+                                              errp);
+    if (!state->bitmap) {
+        return;
+    }
+
+    if (bdrv_dirty_bitmap_frozen(state->bitmap)) {
+        error_setg(errp, "Cannot modify a frozen bitmap");
+        return;
+    } else if (!bdrv_dirty_bitmap_enabled(state->bitmap)) {
+        error_setg(errp, "Cannot clear a disabled bitmap");
+        return;
+    }
+
+    bdrv_clear_dirty_bitmap(state->bitmap, &state->backup);
+    /* AioContext is released in .clean() */
+}
+
+static void block_dirty_bitmap_clear_abort(BlkTransactionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    bdrv_undo_clear_dirty_bitmap(state->bitmap, state->backup);
+}
+
+static void block_dirty_bitmap_clear_commit(BlkTransactionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    hbitmap_free(state->backup);
+}
+
+static void block_dirty_bitmap_clear_clean(BlkTransactionState *common)
+{
+    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
+                                             common, common);
+
+    if (state->aio_context) {
+        aio_context_release(state->aio_context);
+    }
+}
+
 static void abort_prepare(BlkTransactionState *common, Error **errp)
 {
     error_setg(errp, "Transaction aborted using Abort action");
@@ -1921,6 +2021,18 @@ static const BdrvActionOps actions[] = {
         .abort = internal_snapshot_abort,
         .clean = internal_snapshot_clean,
     },
+    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_ADD] = {
+        .instance_size = sizeof(BlockDirtyBitmapState),
+        .prepare = block_dirty_bitmap_add_prepare,
+        .abort = block_dirty_bitmap_add_abort,
+    },
+    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_CLEAR] = {
+        .instance_size = sizeof(BlockDirtyBitmapState),
+        .prepare = block_dirty_bitmap_clear_prepare,
+        .commit = block_dirty_bitmap_clear_commit,
+        .abort = block_dirty_bitmap_clear_abort,
+        .clean = block_dirty_bitmap_clear_clean,
+    }
 };
 
 /*
@@ -2472,7 +2584,7 @@ void qmp_block_dirty_bitmap_clear(const char *node, const char *name,
         goto out;
     }
 
-    bdrv_clear_dirty_bitmap(bitmap);
+    bdrv_clear_dirty_bitmap(bitmap, NULL);
 
  out:
     aio_context_release(aio_context);