BW_CLEAN
KASSERT(flags & BW_CLEAN || !LFS_IS_MALLOC_BUF(bp));
KASSERT(!(flags & BW_CLEAN) || lfs_cleanerlock_held(fs));
if (flags & BW_CLEAN) {
error = lfs_bwrite_ext(bp, BW_CLEAN);
if ((error = lfs_bwrite_ext(bp, BW_CLEAN)) != 0)