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qemu: snapshot: Propagate active bitmaps through external snapshots

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Re-create any active persistent bitmap in the snapshot overlay image so
that tracking for a checkpoint is persisted. While this basically
duplicates data in the allocation map it's currently the only possible
way as qemu can't mirror the allocation map into a dirty bitmap if we'd
ever want to do a backup.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Peter Krempa 2019-11-28 16:06:31 +01:00
parent f1bc1f0fe5
commit 3283445212
1 changed files with 41 additions and 0 deletions
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41
src/qemu/qemu_driver.c
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@ -15282,6 +15282,44 @@ qemuDomainSnapshotDiskCleanup(qemuDomainSnapshotDiskDataPtr data,
}
/**
* qemuDomainSnapshotDiskBitmapsPropagate:
*
* This function propagates any active persistent bitmap present in the original
* image into the new snapshot. This is necessary to keep tracking the changed
* blocks in the active bitmaps as the backing file will become read-only.
* We leave the original bitmap active as in cases when the overlay is
* discarded (snapshot revert with abandoning the history) everything works as
* expected.
*/
static int
qemuDomainSnapshotDiskBitmapsPropagate(qemuDomainSnapshotDiskDataPtr dd,
virJSONValuePtr actions,
virHashTablePtr blockNamedNodeData)
{
qemuBlockNamedNodeDataPtr entry;
size_t i;
if (!(entry = virHashLookup(blockNamedNodeData, dd->disk->src->nodeformat)))
return 0;
for (i = 0; i < entry->nbitmaps; i++) {
qemuBlockNamedNodeDataBitmapPtr bitmap = entry->bitmaps[i];
/* we don't care about temporary, inconsistent, or disabled bitmaps */
if (!bitmap->persistent || !bitmap->recording || bitmap->inconsistent)
continue;
if (qemuMonitorTransactionBitmapAdd(actions, dd->src->nodeformat,
bitmap->name, true, false,
bitmap->granularity) < 0)
return -1;
}
return 0;
}
static int
qemuDomainSnapshotDiskPrepareOneBlockdev(virQEMUDriverPtr driver,
virDomainObjPtr vm,
@ -15423,6 +15461,9 @@ qemuDomainSnapshotDiskPrepareOne(virQEMUDriverPtr driver,
blockNamedNodeData, asyncJob) < 0)
return -1;
if (qemuDomainSnapshotDiskBitmapsPropagate(dd, actions, blockNamedNodeData) < 0)
return -1;
if (qemuBlockSnapshotAddBlockdev(actions, dd->disk, dd->src) < 0)
return -1;
} else {