[Qemu-devel] [RFC 3/9] block: rename BlkTransactionState and BdrvActionOps

[Stefan Hajnoczi <stefanha@redhat.com>]

From: John Snow <jsnow@redhat.com>

These structures are misnomers, somewhat.

(1) BlockTransactionState is not state for a transaction,
    but is rather state for a single transaction action.
    Rename it "BlkActionState" to be more accurate.

(2) The BdrvActionOps describes operations for the BlkActionState,
    above. This name might imply a 'BdrvAction' or a 'BdrvActionState',
    which there isn't.
    Rename this to 'BlkActionOps' to match 'BlkActionState'.

Lastly, update the surrounding in-line documentation and comments
to reflect the current nature of how Transactions operate.

This patch changes only comments and names, and should not affect
behavior in any way.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 blockdev.c | 116 ++++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 65 insertions(+), 51 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index cc91270..e30e986 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1228,43 +1228,57 @@ static BdrvDirtyBitmap *block_dirty_bitmap_lookup(const char *node,
 
 /* New and old BlockDriverState structs for atomic group operations */
 
-typedef struct BlkTransactionState BlkTransactionState;
+typedef struct BlkActionState BlkActionState;
 
-/* Only prepare() may fail. In a single transaction, only one of commit() or
-   abort() will be called, clean() will always be called if it present. */
-typedef struct BdrvActionOps {
-    /* Size of state struct, in bytes. */
+/**
+ * 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.
+ */
+typedef struct BlkActionOps {
     size_t instance_size;
-    /* Prepare the work, must NOT be NULL. */
-    void (*prepare)(BlkTransactionState *common, Error **errp);
-    /* Commit the changes, can be NULL. */
-    void (*commit)(BlkTransactionState *common);
-    /* Abort the changes on fail, can be NULL. */
-    void (*abort)(BlkTransactionState *common);
-    /* Clean up resource in the end, can be NULL. */
-    void (*clean)(BlkTransactionState *common);
-} BdrvActionOps;
+    void (*prepare)(BlkActionState *common, Error **errp);
+    void (*commit)(BlkActionState *common);
+    void (*abort)(BlkActionState *common);
+    void (*clean)(BlkActionState *common);
+} BlkActionOps;
 
-/*
- * This structure must be arranged as first member in child type, assuming
- * that compiler will also arrange it to the same address with parent instance.
- * Later it will be used in free().
+/**
+ * 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.
+ * @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 BlkTransactionState {
+struct BlkActionState {
     TransactionAction *action;
-    const BdrvActionOps *ops;
-    QSIMPLEQ_ENTRY(BlkTransactionState) entry;
+    const BlkActionOps *ops;
+    QSIMPLEQ_ENTRY(BlkActionState) entry;
 };
 
 /* internal snapshot private data */
 typedef struct InternalSnapshotState {
-    BlkTransactionState common;
+    BlkActionState common;
     BlockDriverState *bs;
     AioContext *aio_context;
     QEMUSnapshotInfo sn;
 } InternalSnapshotState;
 
-static void internal_snapshot_prepare(BlkTransactionState *common,
+static void internal_snapshot_prepare(BlkActionState *common,
                                       Error **errp)
 {
     Error *local_err = NULL;
@@ -1359,7 +1373,7 @@ static void internal_snapshot_prepare(BlkTransactionState *common,
     state->bs = bs;
 }
 
-static void internal_snapshot_abort(BlkTransactionState *common)
+static void internal_snapshot_abort(BlkActionState *common)
 {
     InternalSnapshotState *state =
                              DO_UPCAST(InternalSnapshotState, common, common);
@@ -1382,7 +1396,7 @@ static void internal_snapshot_abort(BlkTransactionState *common)
     }
 }
 
-static void internal_snapshot_clean(BlkTransactionState *common)
+static void internal_snapshot_clean(BlkActionState *common)
 {
     InternalSnapshotState *state = DO_UPCAST(InternalSnapshotState,
                                              common, common);
@@ -1394,13 +1408,13 @@ static void internal_snapshot_clean(BlkTransactionState *common)
 
 /* external snapshot private data */
 typedef struct ExternalSnapshotState {
-    BlkTransactionState common;
+    BlkActionState common;
     BlockDriverState *old_bs;
     BlockDriverState *new_bs;
     AioContext *aio_context;
 } ExternalSnapshotState;
 
-static void external_snapshot_prepare(BlkTransactionState *common,
+static void external_snapshot_prepare(BlkActionState *common,
                                       Error **errp)
 {
     BlockDriver *drv;
@@ -1521,7 +1535,7 @@ static void external_snapshot_prepare(BlkTransactionState *common,
     }
 }
 
-static void external_snapshot_commit(BlkTransactionState *common)
+static void external_snapshot_commit(BlkActionState *common)
 {
     ExternalSnapshotState *state =
                              DO_UPCAST(ExternalSnapshotState, common, common);
@@ -1539,7 +1553,7 @@ static void external_snapshot_commit(BlkTransactionState *common)
     aio_context_release(state->aio_context);
 }
 
-static void external_snapshot_abort(BlkTransactionState *common)
+static void external_snapshot_abort(BlkActionState *common)
 {
     ExternalSnapshotState *state =
                              DO_UPCAST(ExternalSnapshotState, common, common);
@@ -1552,13 +1566,13 @@ static void external_snapshot_abort(BlkTransactionState *common)
 }
 
 typedef struct DriveBackupState {
-    BlkTransactionState common;
+    BlkActionState common;
     BlockDriverState *bs;
     AioContext *aio_context;
     BlockJob *job;
 } DriveBackupState;
 
-static void drive_backup_prepare(BlkTransactionState *common, Error **errp)
+static void drive_backup_prepare(BlkActionState *common, Error **errp)
 {
     DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
     BlockDriverState *bs;
@@ -1598,7 +1612,7 @@ static void drive_backup_prepare(BlkTransactionState *common, Error **errp)
     state->job = state->bs->job;
 }
 
-static void drive_backup_abort(BlkTransactionState *common)
+static void drive_backup_abort(BlkActionState *common)
 {
     DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
     BlockDriverState *bs = state->bs;
@@ -1609,7 +1623,7 @@ static void drive_backup_abort(BlkTransactionState *common)
     }
 }
 
-static void drive_backup_clean(BlkTransactionState *common)
+static void drive_backup_clean(BlkActionState *common)
 {
     DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
 
@@ -1619,13 +1633,13 @@ static void drive_backup_clean(BlkTransactionState *common)
 }
 
 typedef struct BlockdevBackupState {
-    BlkTransactionState common;
+    BlkActionState common;
     BlockDriverState *bs;
     BlockJob *job;
     AioContext *aio_context;
 } BlockdevBackupState;
 
-static void blockdev_backup_prepare(BlkTransactionState *common, Error **errp)
+static void blockdev_backup_prepare(BlkActionState *common, Error **errp)
 {
     BlockdevBackupState *state = DO_UPCAST(BlockdevBackupState, common, common);
     BlockdevBackup *backup;
@@ -1674,7 +1688,7 @@ static void blockdev_backup_prepare(BlkTransactionState *common, Error **errp)
     state->job = state->bs->job;
 }
 
-static void blockdev_backup_abort(BlkTransactionState *common)
+static void blockdev_backup_abort(BlkActionState *common)
 {
     BlockdevBackupState *state = DO_UPCAST(BlockdevBackupState, common, common);
     BlockDriverState *bs = state->bs;
@@ -1685,7 +1699,7 @@ static void blockdev_backup_abort(BlkTransactionState *common)
     }
 }
 
-static void blockdev_backup_clean(BlkTransactionState *common)
+static void blockdev_backup_clean(BlkActionState *common)
 {
     BlockdevBackupState *state = DO_UPCAST(BlockdevBackupState, common, common);
 
@@ -1695,7 +1709,7 @@ static void blockdev_backup_clean(BlkTransactionState *common)
 }
 
 typedef struct BlockDirtyBitmapState {
-    BlkTransactionState common;
+    BlkActionState common;
     BdrvDirtyBitmap *bitmap;
     BlockDriverState *bs;
     AioContext *aio_context;
@@ -1703,7 +1717,7 @@ typedef struct BlockDirtyBitmapState {
     bool prepared;
 } BlockDirtyBitmapState;
 
-static void block_dirty_bitmap_add_prepare(BlkTransactionState *common,
+static void block_dirty_bitmap_add_prepare(BlkActionState *common,
                                            Error **errp)
 {
     Error *local_err = NULL;
@@ -1724,7 +1738,7 @@ static void block_dirty_bitmap_add_prepare(BlkTransactionState *common,
     }
 }
 
-static void block_dirty_bitmap_add_abort(BlkTransactionState *common)
+static void block_dirty_bitmap_add_abort(BlkActionState *common)
 {
     BlockDirtyBitmapAdd *action;
     BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
@@ -1739,7 +1753,7 @@ static void block_dirty_bitmap_add_abort(BlkTransactionState *common)
     }
 }
 
-static void block_dirty_bitmap_clear_prepare(BlkTransactionState *common,
+static void block_dirty_bitmap_clear_prepare(BlkActionState *common,
                                              Error **errp)
 {
     BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
@@ -1768,7 +1782,7 @@ static void block_dirty_bitmap_clear_prepare(BlkTransactionState *common,
     /* AioContext is released in .clean() */
 }
 
-static void block_dirty_bitmap_clear_abort(BlkTransactionState *common)
+static void block_dirty_bitmap_clear_abort(BlkActionState *common)
 {
     BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
                                              common, common);
@@ -1776,7 +1790,7 @@ static void block_dirty_bitmap_clear_abort(BlkTransactionState *common)
     bdrv_undo_clear_dirty_bitmap(state->bitmap, state->backup);
 }
 
-static void block_dirty_bitmap_clear_commit(BlkTransactionState *common)
+static void block_dirty_bitmap_clear_commit(BlkActionState *common)
 {
     BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
                                              common, common);
@@ -1784,7 +1798,7 @@ static void block_dirty_bitmap_clear_commit(BlkTransactionState *common)
     hbitmap_free(state->backup);
 }
 
-static void block_dirty_bitmap_clear_clean(BlkTransactionState *common)
+static void block_dirty_bitmap_clear_clean(BlkActionState *common)
 {
     BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
                                              common, common);
@@ -1794,17 +1808,17 @@ static void block_dirty_bitmap_clear_clean(BlkTransactionState *common)
     }
 }
 
-static void abort_prepare(BlkTransactionState *common, Error **errp)
+static void abort_prepare(BlkActionState *common, Error **errp)
 {
     error_setg(errp, "Transaction aborted using Abort action");
 }
 
-static void abort_commit(BlkTransactionState *common)
+static void abort_commit(BlkActionState *common)
 {
     g_assert_not_reached(); /* this action never succeeds */
 }
 
-static const BdrvActionOps actions[] = {
+static const BlkActionOps actions[] = {
     [TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC] = {
         .instance_size = sizeof(ExternalSnapshotState),
         .prepare  = external_snapshot_prepare,
@@ -1824,7 +1838,7 @@ static const BdrvActionOps actions[] = {
         .clean = blockdev_backup_clean,
     },
     [TRANSACTION_ACTION_KIND_ABORT] = {
-        .instance_size = sizeof(BlkTransactionState),
+        .instance_size = sizeof(BlkActionState),
         .prepare = abort_prepare,
         .commit = abort_commit,
     },
@@ -1855,10 +1869,10 @@ static const BdrvActionOps actions[] = {
 void qmp_transaction(TransactionActionList *dev_list, Error **errp)
 {
     TransactionActionList *dev_entry = dev_list;
-    BlkTransactionState *state, *next;
+    BlkActionState *state, *next;
     Error *local_err = NULL;
 
-    QSIMPLEQ_HEAD(snap_bdrv_states, BlkTransactionState) snap_bdrv_states;
+    QSIMPLEQ_HEAD(snap_bdrv_states, BlkActionState) snap_bdrv_states;
     QSIMPLEQ_INIT(&snap_bdrv_states);
 
     /* drain all i/o before any operations */
@@ -1867,7 +1881,7 @@ void qmp_transaction(TransactionActionList *dev_list, Error **errp)
     /* We don't do anything in this loop that commits us to the operations */
     while (NULL != dev_entry) {
         TransactionAction *dev_info = NULL;
-        const BdrvActionOps *ops;
+        const BlkActionOps *ops;
 
         dev_info = dev_entry->value;
         dev_entry = dev_entry->next;
-- 
2.4.2