EXFAT_B_TO_BLK
*sector = EXFAT_B_TO_BLK(off, sb);
struct buffer_head *bh = es->bh[EXFAT_B_TO_BLK(off, es->sb)];
bh = es->bh[EXFAT_B_TO_BLK(off, es->sb)];
valid_blks = EXFAT_B_TO_BLK(ei->valid_size, sb);