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[Qemu-devel] [PATCH V2 5/5] block: make all steps in qmp_transaction() a
From: |
Wenchao Xia |
Subject: |
[Qemu-devel] [PATCH V2 5/5] block: make all steps in qmp_transaction() as callback |
Date: |
Sat, 13 Apr 2013 19:11:41 +0800 |
Now qmp_transaction() can be extended with other operation,
external snapshot or backing chain creation, is just one case it.
Signed-off-by: Wenchao Xia <address@hidden>
---
blockdev.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++--------
1 files changed, 58 insertions(+), 10 deletions(-)
diff --git a/blockdev.c b/blockdev.c
index 3e69569..9f0acfb 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -779,14 +779,35 @@ void qmp_blockdev_snapshot_sync(const char *device, const
char *snapshot_file,
/* New and old BlockDriverState structs for group snapshots */
+
+/* Only in prepare() it may fail, so roll back just need to take care
+ what is done in prepare(). */
+typedef struct BdrvActionOps {
+ /* Prepare the work, must NOT be NULL. */
+ int (*prepare)(BlockdevAction *action, void **p_opaque, Error **errp);
+ /* Commit the changes, can be NULL. */
+ void (*commit)(BlockdevAction *action, void *opaque);
+ /* Rollback the changes on fail, mut NOT be NULL. */
+ void (*rollback)(BlockdevAction *action, void *opaque);
+ /* Clean up resource in the end, can be NULL. */
+ void (*clean)(BlockdevAction *action, void *opaque);
+} BdrvActionOps;
+
typedef struct BlkTransactionStates {
- BlockDriverState *old_bs;
- BlockDriverState *new_bs;
+ BlockdevAction *action;
+ void *opaque;
+ const BdrvActionOps *ops;
QSIMPLEQ_ENTRY(BlkTransactionStates) entry;
} BlkTransactionStates;
+/* external snapshot private data */
+typedef struct ExternalSnapshotState {
+ BlockDriverState *old_bs;
+ BlockDriverState *new_bs;
+} ExternalSnapshotState;
+
static int external_snapshot_prepare(BlockdevAction *action,
- BlkTransactionStates *states,
+ void **p_opaque,
Error **errp)
{
BlockDriver *proto_drv;
@@ -797,6 +818,7 @@ static int external_snapshot_prepare(BlockdevAction *action,
const char *new_image_file;
const char *format = "qcow2";
enum NewImageMode mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
+ ExternalSnapshotState *states;
/* get parameters */
g_assert(action->kind == BLOCKDEV_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC);
@@ -817,6 +839,9 @@ static int external_snapshot_prepare(BlockdevAction *action,
goto fail;
}
+ *p_opaque = g_malloc0(sizeof(ExternalSnapshotState));
+ states = *p_opaque;
+
states->old_bs = bdrv_find(device);
if (!states->old_bs) {
error_set(errp, QERR_DEVICE_NOT_FOUND, device);
@@ -878,8 +903,10 @@ static int external_snapshot_prepare(BlockdevAction
*action,
}
static void external_snapshot_commit(BlockdevAction *action,
- BlkTransactionStates *states)
+ void *opaque)
{
+ ExternalSnapshotState *states = opaque;
+
/* This removes our old bs from the bdrv_states, and adds the new bs */
bdrv_append(states->new_bs, states->old_bs);
/* We don't need (or want) to use the transactional
@@ -890,13 +917,27 @@ static void external_snapshot_commit(BlockdevAction
*action,
}
static void external_snapshot_rollback(BlockdevAction *action,
- BlkTransactionStates *states)
+ void *opaque)
{
+ ExternalSnapshotState *states = opaque;
if (states->new_bs) {
bdrv_delete(states->new_bs);
}
}
+static void external_snapshot_clean(BlockdevAction *action,
+ void *opaque)
+{
+ g_free(opaque);
+}
+
+const BdrvActionOps external_snapshot_ops = {
+ .prepare = external_snapshot_prepare,
+ .commit = external_snapshot_commit,
+ .rollback = external_snapshot_rollback,
+ .clean = external_snapshot_clean,
+};
+
/*
* 'Atomic' group snapshots. The snapshots are taken as a set, and if any fail
* then we do not pivot any of the devices in the group, and abandon the
@@ -923,23 +964,27 @@ void qmp_transaction(BlockdevActionList *dev_list, Error
**errp)
states = g_malloc0(sizeof(BlkTransactionStates));
QSIMPLEQ_INSERT_TAIL(&snap_bdrv_states, states, entry);
+ states->action = dev_info;
switch (dev_info->kind) {
case BLOCKDEV_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC:
- if (external_snapshot_prepare(dev_info, states, errp)) {
- goto delete_and_fail;
- }
+ states->ops = &external_snapshot_ops;
break;
default:
abort();
}
+ if (states->ops->prepare(states->action, &states->opaque, errp)) {
+ goto delete_and_fail;
+ }
}
/* Now we are going to do the actual pivot. Everything up to this point
* is reversible, but we are committed at this point */
QSIMPLEQ_FOREACH(states, &snap_bdrv_states, entry) {
- external_snapshot_commit(NULL, states);
+ if (states->ops->commit) {
+ states->ops->commit(states->action, states->opaque);
+ }
}
/* success */
@@ -951,10 +996,13 @@ delete_and_fail:
* the original bs for all images
*/
QSIMPLEQ_FOREACH(states, &snap_bdrv_states, entry) {
- external_snapshot_rollback(NULL, states);
+ states->ops->rollback(states->action, states->opaque);
}
exit:
QSIMPLEQ_FOREACH_SAFE(states, &snap_bdrv_states, entry, next) {
+ if (states->ops->clean) {
+ states->ops->clean(states->action, states->opaque);
+ }
g_free(states);
}
}
--
1.7.1