+/*
+ * Copyright (c) 1982, 1986, 1989 Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by the University of
+ * California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * @(#)buf.h 7.11 (Berkeley) 5/9/90
+ */
+
+/*
+ * The header for buffers in the buffer pool and otherwise used
+ * to describe a block i/o request is given here.
+ *
+ * Each buffer in the pool is usually doubly linked into 2 lists:
+ * hashed into a chain by <dev,blkno> so it can be located in the cache,
+ * and (usually) on (one of several) queues. These lists are circular and
+ * doubly linked for easy removal.
+ *
+ * There are currently three queues for buffers:
+ * one for buffers which must be kept permanently (super blocks)
+ * one for buffers containing ``useful'' information (the cache)
+ * one for buffers containing ``non-useful'' information
+ * (and empty buffers, pushed onto the front)
+ * The latter two queues contain the buffers which are available for
+ * reallocation, are kept in lru order. When not on one of these queues,
+ * the buffers are ``checked out'' to drivers which use the available list
+ * pointers to keep track of them in their i/o active queues.
+ */
+
+/*
+ * Bufhd structures used at the head of the hashed buffer queues.
+ * We only need three words for these, so this abbreviated
+ * definition saves some space.
+ */
+struct bufhd
+{
+ long b_flags; /* see defines below */
+ struct buf *b_forw, *b_back; /* fwd/bkwd pointer in chain */
+};
+struct buf
+{
+ long b_flags; /* too much goes here to describe */
+ struct buf *b_forw, *b_back; /* hash chain (2 way street) */
+ struct buf *av_forw, *av_back; /* position on free list if not BUSY */
+ struct buf *b_blockf, **b_blockb;/* associated vnode */
+#define b_actf av_forw /* alternate names for driver queue */
+#define b_actl av_back /* head - isn't history wonderful */
+ long b_bcount; /* transfer count */
+ long b_bufsize; /* size of allocated buffer */
+#define b_active b_bcount /* driver queue head: drive active */
+ short b_error; /* returned after I/O */
+ dev_t b_dev; /* major+minor device name */
+ union {
+ caddr_t b_addr; /* low order core address */
+ int *b_words; /* words for clearing */
+ struct fs *b_fs; /* superblocks */
+ struct csum *b_cs; /* superblock summary information */
+ struct cg *b_cg; /* cylinder group block */
+ struct dinode *b_dino; /* ilist */
+ daddr_t *b_daddr; /* indirect block */
+ } b_un;
+ daddr_t b_lblkno; /* logical block number */
+ daddr_t b_blkno; /* block # on device */
+ long b_resid; /* words not transferred after error */
+#define b_errcnt b_resid /* while i/o in progress: # retries */
+ struct proc *b_proc; /* proc doing physical or swap I/O */
+ int (*b_iodone)(); /* function called by iodone */
+ struct vnode *b_vp; /* vnode for dev */
+ int b_pfcent; /* center page when swapping cluster */
+ struct ucred *b_rcred; /* ref to read credentials */
+ struct ucred *b_wcred; /* ref to write credendtials */
+ int b_dirtyoff; /* offset in buffer of dirty region */
+ int b_dirtyend; /* offset of end of dirty region */
+ caddr_t b_saveaddr; /* original b_addr for PHYSIO */
+};
+
+#define BQUEUES 4 /* number of free buffer queues */
+
+#define BQ_LOCKED 0 /* super-blocks &c */
+#define BQ_LRU 1 /* lru, useful buffers */
+#define BQ_AGE 2 /* rubbish */
+#define BQ_EMPTY 3 /* buffer headers with no memory */
+
+#ifdef KERNEL
+#define BUFHSZ 512
+#define RND (MAXBSIZE/DEV_BSIZE)
+#if ((BUFHSZ&(BUFHSZ-1)) == 0)
+#define BUFHASH(dvp, dblkno) \
+ ((struct buf *)&bufhash[((int)(dvp)+(((int)(dblkno))/RND))&(BUFHSZ-1)])
+#else
+#define BUFHASH(dvp, dblkno) \
+ ((struct buf *)&bufhash[((int)(dvp)+(((int)(dblkno))/RND)) % BUFHSZ])
+#endif
+
+struct buf *buf; /* the buffer pool itself */
+char *buffers;
+int nbuf; /* number of buffer headers */
+int bufpages; /* number of memory pages in the buffer pool */
+struct buf *swbuf; /* swap I/O headers */
+int nswbuf;
+struct bufhd bufhash[BUFHSZ]; /* heads of hash lists */
+struct buf bfreelist[BQUEUES]; /* heads of available lists */
+struct buf bswlist; /* head of free swap header list */
+struct buf *bclnlist; /* head of cleaned page list */
+
+void bufinit();
+int bread(struct vnode *, daddr_t, int, struct ucred *, struct buf **);
+int breada(struct vnode *, daddr_t, int, daddr_t, int, struct ucred *,
+ struct buf **);
+int bwrite(struct buf *);
+void bawrite(struct buf *);
+void bdwrite(struct buf *);
+void brelse(struct buf *);
+struct buf *incore(struct vnode *, daddr_t);
+struct buf *getblk(struct vnode *, daddr_t, int);
+struct buf *geteblk(int);
+int biowait(struct buf *);
+int biodone(struct buf *);
+void allocbuf(struct buf *, int);
+
+#endif
+
+/*
+ * These flags are kept in b_flags.
+ */
+#define B_WRITE 0x000000 /* non-read pseudo-flag */
+#define B_READ 0x000001 /* read when I/O occurs */
+#define B_DONE 0x000002 /* transaction finished */
+#define B_ERROR 0x000004 /* transaction aborted */
+#define B_BUSY 0x000008 /* not on av_forw/back list */
+#define B_PHYS 0x000010 /* physical IO */
+#define B_XXX 0x000020 /* was B_MAP, alloc UNIBUS on pdp-11 */
+#define B_WANTED 0x000040 /* issue wakeup when BUSY goes off */
+#define B_AGE 0x000080 /* delayed write for correct aging */
+#define B_ASYNC 0x000100 /* don't wait for I/O completion */
+#define B_DELWRI 0x000200 /* write at exit of avail list */
+#define B_TAPE 0x000400 /* this is a magtape (no bdwrite) */
+#define B_VMPAGE 0x000800 /* buffer from virtual memory */
+#define B_MALLOC 0x001000 /* buffer from malloc space */
+#define B_DIRTY 0x002000 /* dirty page to be pushed out async */
+#define B_PGIN 0x004000 /* pagein op, so swap() can count it */
+#define B_CACHE 0x008000 /* did bread find us in the cache ? */
+#define B_INVAL 0x010000 /* does not contain valid info */
+#define B_LOCKED 0x020000 /* locked in core (not reusable) */
+#define B_HEAD 0x040000 /* a buffer header, not a buffer */
+#define B_BAD 0x100000 /* bad block revectoring in progress */
+#define B_CALL 0x200000 /* call b_iodone from iodone */
+#define B_RAW 0x400000 /* set by physio for raw transfers */
+#define B_NOCACHE 0x800000 /* do not cache block after use */
+
+/*
+ * Insq/Remq for the buffer hash lists.
+ */
+#define bremhash(bp) { \
+ (bp)->b_back->b_forw = (bp)->b_forw; \
+ (bp)->b_forw->b_back = (bp)->b_back; \
+}
+#define binshash(bp, dp) { \
+ (bp)->b_forw = (dp)->b_forw; \
+ (bp)->b_back = (dp); \
+ (dp)->b_forw->b_back = (bp); \
+ (dp)->b_forw = (bp); \
+}
+
+/*
+ * Insq/Remq for the buffer free lists.
+ */
+#define bremfree(bp) { \
+ (bp)->av_back->av_forw = (bp)->av_forw; \
+ (bp)->av_forw->av_back = (bp)->av_back; \
+}
+#define binsheadfree(bp, dp) { \
+ (dp)->av_forw->av_back = (bp); \
+ (bp)->av_forw = (dp)->av_forw; \
+ (dp)->av_forw = (bp); \
+ (bp)->av_back = (dp); \
+}
+#define binstailfree(bp, dp) { \
+ (dp)->av_back->av_forw = (bp); \
+ (bp)->av_back = (dp)->av_back; \
+ (dp)->av_back = (bp); \
+ (bp)->av_forw = (dp); \
+}
+
+#define iodone biodone
+#define iowait biowait
+
+/*
+ * Zero out a buffer's data portion.
+ */
+#define clrbuf(bp) { \
+ bzero((bp)->b_un.b_addr, (unsigned)(bp)->b_bcount); \
+ (bp)->b_resid = 0; \
+}
+#define B_CLRBUF 0x1 /* request allocated buffer be cleared */
+#define B_SYNC 0x2 /* do all allocations synchronously */
projects / unix-history / commitdiff