[PULL 06/18] blockdev: qmp_transaction: drop extra generic layer

[Kevin Wolf <kwolf@redhat.com>]

From: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

Let's simplify things:

First, actions generally don't need access to common BlkActionState
structure. The only exclusion are backup actions that need
block_job_txn.

Next, for transaction actions of Transaction API is more native to
allocated state structure in the action itself.

So, do the following transformation:

1. Let all actions be represented by a function with corresponding
   structure as arguments.

2. Instead of array-map marshaller, let's make a function, that calls
   corresponding action directly.

3. BlkActionOps and BlkActionState structures become unused

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-Id: <20230510150624.310640-7-vsementsov@yandex-team.ru>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 blockdev.c | 265 +++++++++++++++++------------------------------------
 1 file changed, 85 insertions(+), 180 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 4bf15566b2..5d56b79df4 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1188,54 +1188,8 @@ out_aio_context:
     return NULL;
 }
 
-/* New and old BlockDriverState structs for atomic group operations */
-
-typedef struct BlkActionState BlkActionState;
-
-/**
- * BlkActionOps:
- * Table of operations that define an Action.
- *
- * @instance_size: Size of state struct, in bytes.
- * @prepare: Prepare the work, must NOT be NULL.
- * @commit: Commit the changes, can be NULL.
- * @abort: Abort the changes on fail, can be NULL.
- * @clean: Clean up resources after all transaction actions have called
- *         commit() or abort(). Can be NULL.
- *
- * Only prepare() may fail. In a single transaction, only one of commit() or
- * abort() will be called. clean() will always be called if it is present.
- *
- * Always run under BQL.
- */
-typedef struct BlkActionOps {
-    size_t instance_size;
-    void (*action)(BlkActionState *common, Transaction *tran, Error **errp);
-} BlkActionOps;
-
-/**
- * BlkActionState:
- * Describes one Action's state within a Transaction.
- *
- * @action: QAPI-defined enum identifying which Action to perform.
- * @ops: Table of ActionOps this Action can perform.
- * @block_job_txn: Transaction which this action belongs to.
- * @entry: List membership for all Actions in this Transaction.
- *
- * This structure must be arranged as first member in a subclassed type,
- * assuming that the compiler will also arrange it to the same offsets as the
- * base class.
- */
-struct BlkActionState {
-    TransactionAction *action;
-    const BlkActionOps *ops;
-    JobTxn *block_job_txn;
-    QTAILQ_ENTRY(BlkActionState) entry;
-};
-
 /* internal snapshot private data */
 typedef struct InternalSnapshotState {
-    BlkActionState common;
     BlockDriverState *bs;
     QEMUSnapshotInfo sn;
     bool created;
@@ -1248,7 +1202,7 @@ TransactionActionDrv internal_snapshot_drv = {
     .clean = internal_snapshot_clean,
 };
 
-static void internal_snapshot_action(BlkActionState *common,
+static void internal_snapshot_action(BlockdevSnapshotInternal *internal,
                                      Transaction *tran, Error **errp)
 {
     Error *local_err = NULL;
@@ -1258,16 +1212,10 @@ static void internal_snapshot_action(BlkActionState *common,
     QEMUSnapshotInfo old_sn, *sn;
     bool ret;
     int64_t rt;
-    BlockdevSnapshotInternal *internal;
-    InternalSnapshotState *state;
+    InternalSnapshotState *state = g_new0(InternalSnapshotState, 1);
     AioContext *aio_context;
     int ret1;
 
-    g_assert(common->action->type ==
-             TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_INTERNAL_SYNC);
-    internal = common->action->u.blockdev_snapshot_internal_sync.data;
-    state = DO_UPCAST(InternalSnapshotState, common, common);
-
     tran_add(tran, &internal_snapshot_drv, state);
 
     device = internal->device;
@@ -1393,7 +1341,6 @@ static void internal_snapshot_clean(void *opaque)
 
 /* external snapshot private data */
 typedef struct ExternalSnapshotState {
-    BlkActionState common;
     BlockDriverState *old_bs;
     BlockDriverState *new_bs;
     bool overlay_appended;
@@ -1408,8 +1355,8 @@ TransactionActionDrv external_snapshot_drv = {
     .clean = external_snapshot_clean,
 };
 
-static void external_snapshot_action(BlkActionState *common, Transaction *tran,
-                                     Error **errp)
+static void external_snapshot_action(TransactionAction *action,
+                                     Transaction *tran, Error **errp)
 {
     int ret;
     int flags = 0;
@@ -1422,9 +1369,7 @@ static void external_snapshot_action(BlkActionState *common, Transaction *tran,
     const char *snapshot_ref;
     /* File name of the new image (for 'blockdev-snapshot-sync') */
     const char *new_image_file;
-    ExternalSnapshotState *state =
-                             DO_UPCAST(ExternalSnapshotState, common, common);
-    TransactionAction *action = common->action;
+    ExternalSnapshotState *state = g_new0(ExternalSnapshotState, 1);
     AioContext *aio_context;
     uint64_t perm, shared;
 
@@ -1658,7 +1603,6 @@ static void external_snapshot_clean(void *opaque)
 }
 
 typedef struct DriveBackupState {
-    BlkActionState common;
     BlockDriverState *bs;
     BlockJob *job;
 } DriveBackupState;
@@ -1678,11 +1622,11 @@ TransactionActionDrv drive_backup_drv = {
     .clean = drive_backup_clean,
 };
 
-static void drive_backup_action(BlkActionState *common, Transaction *tran,
-                                Error **errp)
+static void drive_backup_action(DriveBackup *backup,
+                                JobTxn *block_job_txn,
+                                Transaction *tran, Error **errp)
 {
-    DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
-    DriveBackup *backup;
+    DriveBackupState *state = g_new0(DriveBackupState, 1);
     BlockDriverState *bs;
     BlockDriverState *target_bs;
     BlockDriverState *source = NULL;
@@ -1698,9 +1642,6 @@ static void drive_backup_action(BlkActionState *common, Transaction *tran,
 
     tran_add(tran, &drive_backup_drv, state);
 
-    assert(common->action->type == TRANSACTION_ACTION_KIND_DRIVE_BACKUP);
-    backup = common->action->u.drive_backup.data;
-
     if (!backup->has_mode) {
         backup->mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
     }
@@ -1820,7 +1761,7 @@ static void drive_backup_action(BlkActionState *common, Transaction *tran,
 
     state->job = do_backup_common(qapi_DriveBackup_base(backup),
                                   bs, target_bs, aio_context,
-                                  common->block_job_txn, errp);
+                                  block_job_txn, errp);
 
 unref:
     bdrv_unref(target_bs);
@@ -1869,7 +1810,6 @@ static void drive_backup_clean(void *opaque)
 }
 
 typedef struct BlockdevBackupState {
-    BlkActionState common;
     BlockDriverState *bs;
     BlockJob *job;
 } BlockdevBackupState;
@@ -1883,11 +1823,11 @@ TransactionActionDrv blockdev_backup_drv = {
     .clean = blockdev_backup_clean,
 };
 
-static void blockdev_backup_action(BlkActionState *common, Transaction *tran,
-                                   Error **errp)
+static void blockdev_backup_action(BlockdevBackup *backup,
+                                   JobTxn *block_job_txn,
+                                   Transaction *tran, Error **errp)
 {
-    BlockdevBackupState *state = DO_UPCAST(BlockdevBackupState, common, common);
-    BlockdevBackup *backup;
+    BlockdevBackupState *state = g_new0(BlockdevBackupState, 1);
     BlockDriverState *bs;
     BlockDriverState *target_bs;
     AioContext *aio_context;
@@ -1896,9 +1836,6 @@ static void blockdev_backup_action(BlkActionState *common, Transaction *tran,
 
     tran_add(tran, &blockdev_backup_drv, state);
 
-    assert(common->action->type == TRANSACTION_ACTION_KIND_BLOCKDEV_BACKUP);
-    backup = common->action->u.blockdev_backup.data;
-
     bs = bdrv_lookup_bs(backup->device, backup->device, errp);
     if (!bs) {
         return;
@@ -1929,7 +1866,7 @@ static void blockdev_backup_action(BlkActionState *common, Transaction *tran,
 
     state->job = do_backup_common(qapi_BlockdevBackup_base(backup),
                                   bs, target_bs, aio_context,
-                                  common->block_job_txn, errp);
+                                  block_job_txn, errp);
 
     aio_context_release(aio_context);
 }
@@ -1975,7 +1912,6 @@ static void blockdev_backup_clean(void *opaque)
 }
 
 typedef struct BlockDirtyBitmapState {
-    BlkActionState common;
     BdrvDirtyBitmap *bitmap;
     BlockDriverState *bs;
     HBitmap *backup;
@@ -1988,17 +1924,14 @@ TransactionActionDrv block_dirty_bitmap_add_drv = {
     .clean = g_free,
 };
 
-static void block_dirty_bitmap_add_action(BlkActionState *common,
+static void block_dirty_bitmap_add_action(BlockDirtyBitmapAdd *action,
                                           Transaction *tran, Error **errp)
 {
     Error *local_err = NULL;
-    BlockDirtyBitmapAdd *action;
-    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
-                                             common, common);
+    BlockDirtyBitmapState *state = g_new0(BlockDirtyBitmapState, 1);
 
     tran_add(tran, &block_dirty_bitmap_add_drv, state);
 
-    action = common->action->u.block_dirty_bitmap_add.data;
     /* 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,
@@ -2031,16 +1964,13 @@ TransactionActionDrv block_dirty_bitmap_clear_drv = {
     .clean = g_free,
 };
 
-static void block_dirty_bitmap_clear_action(BlkActionState *common,
+static void block_dirty_bitmap_clear_action(BlockDirtyBitmap *action,
                                             Transaction *tran, Error **errp)
 {
-    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
-                                             common, common);
-    BlockDirtyBitmap *action;
+    BlockDirtyBitmapState *state = g_new0(BlockDirtyBitmapState, 1);
 
     tran_add(tran, &block_dirty_bitmap_clear_drv, state);
 
-    action = common->action->u.block_dirty_bitmap_clear.data;
     state->bitmap = block_dirty_bitmap_lookup(action->node,
                                               action->name,
                                               &state->bs,
@@ -2078,16 +2008,13 @@ TransactionActionDrv block_dirty_bitmap_enable_drv = {
     .clean = g_free,
 };
 
-static void block_dirty_bitmap_enable_action(BlkActionState *common,
+static void block_dirty_bitmap_enable_action(BlockDirtyBitmap *action,
                                              Transaction *tran, Error **errp)
 {
-    BlockDirtyBitmap *action;
-    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
-                                             common, common);
+    BlockDirtyBitmapState *state = g_new0(BlockDirtyBitmapState, 1);
 
     tran_add(tran, &block_dirty_bitmap_enable_drv, state);
 
-    action = common->action->u.block_dirty_bitmap_enable.data;
     state->bitmap = block_dirty_bitmap_lookup(action->node,
                                               action->name,
                                               NULL,
@@ -2119,16 +2046,13 @@ TransactionActionDrv block_dirty_bitmap_disable_drv = {
     .clean = g_free,
 };
 
-static void block_dirty_bitmap_disable_action(BlkActionState *common,
+static void block_dirty_bitmap_disable_action(BlockDirtyBitmap *action,
                                               Transaction *tran, Error **errp)
 {
-    BlockDirtyBitmap *action;
-    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
-                                             common, common);
+    BlockDirtyBitmapState *state = g_new0(BlockDirtyBitmapState, 1);
 
     tran_add(tran, &block_dirty_bitmap_disable_drv, state);
 
-    action = common->action->u.block_dirty_bitmap_disable.data;
     state->bitmap = block_dirty_bitmap_lookup(action->node,
                                               action->name,
                                               NULL,
@@ -2160,17 +2084,13 @@ TransactionActionDrv block_dirty_bitmap_merge_drv = {
     .clean = g_free,
 };
 
-static void block_dirty_bitmap_merge_action(BlkActionState *common,
+static void block_dirty_bitmap_merge_action(BlockDirtyBitmapMerge *action,
                                             Transaction *tran, Error **errp)
 {
-    BlockDirtyBitmapMerge *action;
-    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
-                                             common, common);
+    BlockDirtyBitmapState *state = g_new0(BlockDirtyBitmapState, 1);
 
     tran_add(tran, &block_dirty_bitmap_merge_drv, state);
 
-    action = common->action->u.block_dirty_bitmap_merge.data;
-
     state->bitmap = block_dirty_bitmap_merge(action->node, action->target,
                                              action->bitmaps, &state->backup,
                                              errp);
@@ -2184,16 +2104,13 @@ TransactionActionDrv block_dirty_bitmap_remove_drv = {
     .clean = g_free,
 };
 
-static void block_dirty_bitmap_remove_action(BlkActionState *common,
+static void block_dirty_bitmap_remove_action(BlockDirtyBitmap *action,
                                              Transaction *tran, Error **errp)
 {
-    BlockDirtyBitmap *action;
-    BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
-                                             common, common);
+    BlockDirtyBitmapState *state = g_new0(BlockDirtyBitmapState, 1);
 
     tran_add(tran, &block_dirty_bitmap_remove_drv, state);
 
-    action = common->action->u.block_dirty_bitmap_remove.data;
 
     state->bitmap = block_dirty_bitmap_remove(action->node, action->name,
                                               false, &state->bs, errp);
@@ -2224,13 +2141,11 @@ static void block_dirty_bitmap_remove_commit(void *opaque)
 static void abort_commit(void *opaque);
 TransactionActionDrv abort_drv = {
     .commit = abort_commit,
-    .clean = g_free,
 };
 
-static void abort_action(BlkActionState *common, Transaction *tran,
-                         Error **errp)
+static void abort_action(Transaction *tran, Error **errp)
 {
-    tran_add(tran, &abort_drv, common);
+    tran_add(tran, &abort_drv, NULL);
     error_setg(errp, "Transaction aborted using Abort action");
 }
 
@@ -2239,62 +2154,66 @@ static void abort_commit(void *opaque)
     g_assert_not_reached(); /* this action never succeeds */
 }
 
-static const BlkActionOps actions_map[] = {
-    [TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT] = {
-        .instance_size = sizeof(ExternalSnapshotState),
-        .action  = external_snapshot_action,
-    },
-    [TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC] = {
-        .instance_size = sizeof(ExternalSnapshotState),
-        .action  = external_snapshot_action,
-    },
-    [TRANSACTION_ACTION_KIND_DRIVE_BACKUP] = {
-        .instance_size = sizeof(DriveBackupState),
-        .action = drive_backup_action,
-    },
-    [TRANSACTION_ACTION_KIND_BLOCKDEV_BACKUP] = {
-        .instance_size = sizeof(BlockdevBackupState),
-        .action = blockdev_backup_action,
-    },
-    [TRANSACTION_ACTION_KIND_ABORT] = {
-        .instance_size = sizeof(BlkActionState),
-        .action = abort_action,
-    },
-    [TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_INTERNAL_SYNC] = {
-        .instance_size = sizeof(InternalSnapshotState),
-        .action  = internal_snapshot_action,
-    },
-    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_ADD] = {
-        .instance_size = sizeof(BlockDirtyBitmapState),
-        .action = block_dirty_bitmap_add_action,
-    },
-    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_CLEAR] = {
-        .instance_size = sizeof(BlockDirtyBitmapState),
-        .action = block_dirty_bitmap_clear_action,
-    },
-    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_ENABLE] = {
-        .instance_size = sizeof(BlockDirtyBitmapState),
-        .action = block_dirty_bitmap_enable_action,
-    },
-    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_DISABLE] = {
-        .instance_size = sizeof(BlockDirtyBitmapState),
-        .action = block_dirty_bitmap_disable_action,
-    },
-    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_MERGE] = {
-        .instance_size = sizeof(BlockDirtyBitmapState),
-        .action = block_dirty_bitmap_merge_action,
-    },
-    [TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_REMOVE] = {
-        .instance_size = sizeof(BlockDirtyBitmapState),
-        .action = block_dirty_bitmap_remove_action,
-    },
-    /* Where are transactions for MIRROR, COMMIT and STREAM?
+static void transaction_action(TransactionAction *act, JobTxn *block_job_txn,
+                               Transaction *tran, Error **errp)
+{
+    switch (act->type) {
+    case TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT:
+    case TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC:
+        external_snapshot_action(act, tran, errp);
+        return;
+    case TRANSACTION_ACTION_KIND_DRIVE_BACKUP:
+        drive_backup_action(act->u.drive_backup.data,
+                            block_job_txn, tran, errp);
+        return;
+    case TRANSACTION_ACTION_KIND_BLOCKDEV_BACKUP:
+        blockdev_backup_action(act->u.blockdev_backup.data,
+                               block_job_txn, tran, errp);
+        return;
+    case TRANSACTION_ACTION_KIND_ABORT:
+        abort_action(tran, errp);
+        return;
+    case TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_INTERNAL_SYNC:
+        internal_snapshot_action(act->u.blockdev_snapshot_internal_sync.data,
+                                 tran, errp);
+        return;
+    case TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_ADD:
+        block_dirty_bitmap_add_action(act->u.block_dirty_bitmap_add.data,
+                                      tran, errp);
+        return;
+    case TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_CLEAR:
+        block_dirty_bitmap_clear_action(act->u.block_dirty_bitmap_clear.data,
+                                        tran, errp);
+        return;
+    case TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_ENABLE:
+        block_dirty_bitmap_enable_action(act->u.block_dirty_bitmap_enable.data,
+                                         tran, errp);
+        return;
+    case TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_DISABLE:
+        block_dirty_bitmap_disable_action(
+                act->u.block_dirty_bitmap_disable.data, tran, errp);
+        return;
+    case TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_MERGE:
+        block_dirty_bitmap_merge_action(act->u.block_dirty_bitmap_merge.data,
+                                        tran, errp);
+        return;
+    case TRANSACTION_ACTION_KIND_BLOCK_DIRTY_BITMAP_REMOVE:
+        block_dirty_bitmap_remove_action(act->u.block_dirty_bitmap_remove.data,
+                                         tran, errp);
+        return;
+    /*
+     * 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.
      * These jobs may not fully undo all of their actions on abort, nor do they
      * necessarily work in transactions with more than one job in them.
      */
-};
+    case TRANSACTION_ACTION_KIND__MAX:
+    default:
+        g_assert_not_reached();
+    };
+}
+
 
 /*
  * 'Atomic' group operations.  The operations are performed as a set, and if
@@ -2345,21 +2264,7 @@ void qmp_transaction(TransactionActionList *actions,
 
     /* We don't do anything in this loop that commits us to the operations */
     for (act = actions; act; act = act->next) {
-        TransactionAction *dev_info = act->value;
-        const BlkActionOps *ops;
-        BlkActionState *state;
-
-        assert(dev_info->type < ARRAY_SIZE(actions_map));
-
-        ops = &actions_map[dev_info->type];
-        assert(ops->instance_size > 0);
-
-        state = g_malloc0(ops->instance_size);
-        state->ops = ops;
-        state->action = dev_info;
-        state->block_job_txn = block_job_txn;
-
-        state->ops->action(state, tran, &local_err);
+        transaction_action(act->value, block_job_txn, tran, &local_err);
         if (local_err) {
             error_propagate(errp, local_err);
             goto delete_and_fail;
-- 
2.40.1