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block: make all steps in qmp_transaction() as callback 

Make it easier to add other operations to qmp_transaction() by using
callbacks, with external snapshots serving as an example implementation
of the callbacks.

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Wenchao Xia 2013-05-08 18:25:16 +08:00 committed by Stefan Hajnoczi
parent 96b86bf72d
commit ba0c86a34e
1 changed files with 71 additions and 24 deletions
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95
blockdev.c
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@ -779,14 +779,43 @@ void qmp_blockdev_snapshot_sync(const char *device, const char *snapshot_file,
/* New and old BlockDriverState structs for group snapshots */
typedef struct BlkTransactionStates {
typedef struct BlkTransactionStates BlkTransactionStates;
/* 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. */
size_t instance_size;
/* Prepare the work, must NOT be NULL. */
void (*prepare)(BlkTransactionStates *common, Error **errp);
/* Commit the changes, must NOT be NULL. */
void (*commit)(BlkTransactionStates *common);
/* Abort the changes on fail, can be NULL. */
void (*abort)(BlkTransactionStates *common);
/* Clean up resource in the end, can be NULL. */
void (*clean)(BlkTransactionStates *common);
} BdrvActionOps;
/*
* 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().
*/
struct BlkTransactionStates {
BlockdevAction *action;
const BdrvActionOps *ops;
QSIMPLEQ_ENTRY(BlkTransactionStates) entry;
};
/* external snapshot private data */
typedef struct ExternalSnapshotStates {
BlkTransactionStates common;
BlockDriverState *old_bs;
BlockDriverState *new_bs;
QSIMPLEQ_ENTRY(BlkTransactionStates) entry;
} BlkTransactionStates;
} ExternalSnapshotStates;
static void external_snapshot_prepare(BlockdevAction *action,
BlkTransactionStates *states,
static void external_snapshot_prepare(BlkTransactionStates *common,
Error **errp)
{
BlockDriver *proto_drv;
@ -797,6 +826,9 @@ static void external_snapshot_prepare(BlockdevAction *action,
const char *new_image_file;
const char *format = "qcow2";
enum NewImageMode mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
ExternalSnapshotStates *states =
DO_UPCAST(ExternalSnapshotStates, common, common);
BlockdevAction *action = common->action;
/* get parameters */
g_assert(action->kind == BLOCKDEV_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC);
@ -871,8 +903,11 @@ static void external_snapshot_prepare(BlockdevAction *action,
}
}
static void external_snapshot_commit(BlkTransactionStates *states)
static void external_snapshot_commit(BlkTransactionStates *common)
{
ExternalSnapshotStates *states =
DO_UPCAST(ExternalSnapshotStates, common, common);
/* 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
@ -882,13 +917,24 @@ static void external_snapshot_commit(BlkTransactionStates *states)
NULL);
}
static void external_snapshot_abort(BlkTransactionStates *states)
static void external_snapshot_abort(BlkTransactionStates *common)
{
ExternalSnapshotStates *states =
DO_UPCAST(ExternalSnapshotStates, common, common);
if (states->new_bs) {
bdrv_delete(states->new_bs);
}
}
static const BdrvActionOps actions[] = {
[BLOCKDEV_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC] = {
.instance_size = sizeof(ExternalSnapshotStates),
.prepare = external_snapshot_prepare,
.commit = external_snapshot_commit,
.abort = external_snapshot_abort,
},
};
/*
* '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
@ -909,32 +955,28 @@ void qmp_transaction(BlockdevActionList *dev_list, Error **errp)
/* We don't do anything in this loop that commits us to the snapshot */
while (NULL != dev_entry) {
BlockdevAction *dev_info = NULL;
const BdrvActionOps *ops;
dev_info = dev_entry->value;
dev_entry = dev_entry->next;
states = g_malloc0(sizeof(BlkTransactionStates));
assert(dev_info->kind < ARRAY_SIZE(actions));
ops = &actions[dev_info->kind];
states = g_malloc0(ops->instance_size);
states->ops = ops;
states->action = dev_info;
QSIMPLEQ_INSERT_TAIL(&snap_bdrv_states, states, entry);
switch (dev_info->kind) {
case BLOCKDEV_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC:
external_snapshot_prepare(dev_info, states, errp);
if (error_is_set(&local_err)) {
error_propagate(errp, local_err);
goto delete_and_fail;
}
break;
default:
abort();
states->ops->prepare(states, &local_err);
if (error_is_set(&local_err)) {
error_propagate(errp, local_err);
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(states);
states->ops->commit(states);
}
/* success */
@ -946,10 +988,15 @@ delete_and_fail:
* the original bs for all images
*/
QSIMPLEQ_FOREACH(states, &snap_bdrv_states, entry) {
external_snapshot_abort(states);
if (states->ops->abort) {
states->ops->abort(states);
}
}
exit:
QSIMPLEQ_FOREACH_SAFE(states, &snap_bdrv_states, entry, next) {
if (states->ops->clean) {
states->ops->clean(states);
}
g_free(states);
}
}