dbuf               77 kernel/log.c       struct buf *dbuf = bread(log.dev, log.lh.block[tail]);   // read dst
dbuf               78 kernel/log.c       memmove(dbuf->data, lbuf->data, BSIZE); // copy block to dst
dbuf               79 kernel/log.c       bwrite(dbuf);                           // write dst to disk
dbuf               81 kernel/log.c         bunpin(dbuf);
dbuf               83 kernel/log.c       brelse(dbuf);