BLOCKNUM
for (i = 0; i < BLOCKNUM(df->df_datalen, DTFS_BLOCKSHIFT); i++)
newblocks = BLOCKNUM(newsize, DTFS_BLOCKSHIFT) + 1;
pn->pn_va.va_bytes = BLOCKNUM(newsize,DTFS_BLOCKSHIFT)>>DTFS_BLOCKSHIFT;
src = df->df_blocks[BLOCKNUM(offset, DTFS_BLOCKSHIFT)]
i = BLOCKNUM(offset, DTFS_BLOCKSHIFT);