NUM_SNAPSHOT_HDR_CHUNKS
return NUM_SNAPSHOT_HDR_CHUNKS + ((ps->exceptions_per_area + 1) * area);
if (sector_div(next_free, stride) == NUM_SNAPSHOT_HDR_CHUNKS)
*metadata_sectors = (ps->current_area + 1 + NUM_SNAPSHOT_HDR_CHUNKS) *
ps->next_free = NUM_SNAPSHOT_HDR_CHUNKS + 1; /* header and 1st area */