27 lines
957 B
C
27 lines
957 B
C
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/* Buffer (block) cache.
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*/
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struct buf {
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/* Data portion of the buffer. */
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char b_data[PIPE_BUF]; /* ordinary user data */
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/* Header portion of the buffer. */
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struct buf *b_next; /* used to link all free bufs in a chain */
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struct buf *b_prev; /* used to link all free bufs the other way */
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ino_t b_num; /* inode number on minor device */
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dev_t b_dev; /* major | minor device where block resides */
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int b_bytes; /* Number of bytes allocated in bp */
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int b_count; /* Number of users of this buffer */
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};
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/* A block is free if b_dev == NO_DEV. */
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#define NIL_BUF ((struct buf *) 0) /* indicates absence of a buffer */
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#define BUFHASH(b) ((b) % NR_BUFS)
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EXTERN struct buf *front; /* points to least recently used free block */
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EXTERN struct buf *rear; /* points to most recently used free block */
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EXTERN int bufs_in_use; /* # bufs currently in use (not on free list)*/
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