buf.h

   1 struct buf {
   2   int flags;
   3   uint dev;
   4   uint sector;
   5   struct buf *prev; // LRU cache list
   6   struct buf *next;
   7   struct buf *qnext; // disk queue
   8   uchar data[512];
   9 };
  10 #define B_BUSY  0x1  // buffer is locked by some process
  11 #define B_VALID 0x2  // buffer has been read from disk
  12 #define B_DIRTY 0x4  // buffer needs to be written to disk
  13