qmp: add internal snapshot support in qmp_transaction

Unlike savevm, the qmp_transaction interface will not generate
snapshot name automatically, saving trouble to return information
of the new created snapshot.

Although qcow2 support storing multiple snapshots with same name
but different ID, here it will fail when an snapshot with that name
already exist before the operation. Format such as rbd do not support
ID at all, and in most case, it means trouble to user when he faces
multiple snapshots with same name, so ban that case. Request with
empty name will be rejected.

Snapshot ID can't be specified in this interface.

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/blockdev.c b/blockdev.c
index 07dac05a2c..0fd30e2d8d 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -889,6 +889,117 @@ struct BlkTransactionState {
     QSIMPLEQ_ENTRY(BlkTransactionState) entry;
 };
 
+/* internal snapshot private data */
+typedef struct InternalSnapshotState {
+    BlkTransactionState common;
+    BlockDriverState *bs;
+    QEMUSnapshotInfo sn;
+} InternalSnapshotState;
+
+static void internal_snapshot_prepare(BlkTransactionState *common,
+                                      Error **errp)
+{
+    const char *device;
+    const char *name;
+    BlockDriverState *bs;
+    QEMUSnapshotInfo old_sn, *sn;
+    bool ret;
+    qemu_timeval tv;
+    BlockdevSnapshotInternal *internal;
+    InternalSnapshotState *state;
+    int ret1;
+
+    g_assert(common->action->kind ==
+             TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_INTERNAL_SYNC);
+    internal = common->action->blockdev_snapshot_internal_sync;
+    state = DO_UPCAST(InternalSnapshotState, common, common);
+
+    /* 1. parse input */
+    device = internal->device;
+    name = internal->name;
+
+    /* 2. check for validation */
+    bs = bdrv_find(device);
+    if (!bs) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
+        return;
+    }
+
+    if (!bdrv_is_inserted(bs)) {
+        error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
+        return;
+    }
+
+    if (bdrv_is_read_only(bs)) {
+        error_set(errp, QERR_DEVICE_IS_READ_ONLY, device);
+        return;
+    }
+
+    if (!bdrv_can_snapshot(bs)) {
+        error_set(errp, QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
+                  bs->drv->format_name, device, "internal snapshot");
+        return;
+    }
+
+    if (!strlen(name)) {
+        error_setg(errp, "Name is empty");
+        return;
+    }
+
+    /* check whether a snapshot with name exist */
+    ret = bdrv_snapshot_find_by_id_and_name(bs, NULL, name, &old_sn, errp);
+    if (error_is_set(errp)) {
+        return;
+    } else if (ret) {
+        error_setg(errp,
+                   "Snapshot with name '%s' already exists on device '%s'",
+                   name, device);
+        return;
+    }
+
+    /* 3. take the snapshot */
+    sn = &state->sn;
+    pstrcpy(sn->name, sizeof(sn->name), name);
+    qemu_gettimeofday(&tv);
+    sn->date_sec = tv.tv_sec;
+    sn->date_nsec = tv.tv_usec * 1000;
+    sn->vm_clock_nsec = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+
+    ret1 = bdrv_snapshot_create(bs, sn);
+    if (ret1 < 0) {
+        error_setg_errno(errp, -ret1,
+                         "Failed to create snapshot '%s' on device '%s'",
+                         name, device);
+        return;
+    }
+
+    /* 4. succeed, mark a snapshot is created */
+    state->bs = bs;
+}
+
+static void internal_snapshot_abort(BlkTransactionState *common)
+{
+    InternalSnapshotState *state =
+                             DO_UPCAST(InternalSnapshotState, common, common);
+    BlockDriverState *bs = state->bs;
+    QEMUSnapshotInfo *sn = &state->sn;
+    Error *local_error = NULL;
+
+    if (!bs) {
+        return;
+    }
+
+    if (bdrv_snapshot_delete(bs, sn->id_str, sn->name, &local_error) < 0) {
+        error_report("Failed to delete snapshot with id '%s' and name '%s' on "
+                     "device '%s' in abort: %s",
+                     sn->id_str,
+                     sn->name,
+                     bdrv_get_device_name(bs),
+                     error_get_pretty(local_error));
+        error_free(local_error);
+    }
+}
+
 /* external snapshot private data */
 typedef struct ExternalSnapshotState {
     BlkTransactionState common;
@@ -1072,6 +1183,11 @@ static const BdrvActionOps actions[] = {
         .prepare = abort_prepare,
         .commit = abort_commit,
     },
+    [TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_INTERNAL_SYNC] = {
+        .instance_size = sizeof(InternalSnapshotState),
+        .prepare  = internal_snapshot_prepare,
+        .abort = internal_snapshot_abort,
+    },
 };
 
 /*