QCowSnapshot *sn;
QCowSnapshotHeader h;
int i, name_size, id_str_size, snapshots_size;
- uint64_t data64;
- uint32_t data32;
+ struct {
+ uint32_t nb_snapshots;
+ uint64_t snapshots_offset;
+ } QEMU_PACKED header_data;
int64_t offset, snapshots_offset;
int ret;
/*
* Update the header to point to the new snapshot table. This requires the
* new table and its refcounts to be stable on disk.
- *
- * FIXME This should be done with a single write
*/
ret = bdrv_flush(bs);
if (ret < 0) {
goto fail;
}
- data64 = cpu_to_be64(snapshots_offset);
- ret = bdrv_pwrite(bs->file, offsetof(QCowHeader, snapshots_offset),
- &data64, sizeof(data64));
- if (ret < 0) {
- goto fail;
- }
+ QEMU_BUILD_BUG_ON(offsetof(QCowHeader, snapshots_offset) !=
+ offsetof(QCowHeader, nb_snapshots) + sizeof(header_data.nb_snapshots));
+
+ header_data.nb_snapshots = cpu_to_be32(s->nb_snapshots);
+ header_data.snapshots_offset = cpu_to_be64(snapshots_offset);
- data32 = cpu_to_be32(s->nb_snapshots);
ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, nb_snapshots),
- &data32, sizeof(data32));
+ &header_data, sizeof(header_data));
if (ret < 0) {
goto fail;
}