Code documentation only: Describe B_NOCACHE
[dragonfly.git] / sys / sys / buf.h
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1/*
2 * Copyright (c) 1982, 1986, 1989, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the University of
21 * California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
24 * without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 *
38 * @(#)buf.h 8.9 (Berkeley) 3/30/95
39 * $FreeBSD: src/sys/sys/buf.h,v 1.88.2.10 2003/01/25 19:02:23 dillon Exp $
e409de84 40 * $DragonFly: src/sys/sys/buf.h,v 1.52 2008/07/17 23:55:24 dillon Exp $
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41 */
42
43#ifndef _SYS_BUF_H_
44#define _SYS_BUF_H_
45
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46#if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
47
335dda38 48#ifndef _SYS_QUEUE_H_
984263bc 49#include <sys/queue.h>
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50#endif
51#ifndef _SYS_LOCK_H_
984263bc 52#include <sys/lock.h>
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53#endif
54#ifndef _SYS_DEVICE_H_
55#include <sys/device.h>
56#endif
984263bc 57
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58#ifndef _SYS_XIO_H_
59#include <sys/xio.h>
60#endif
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61#ifndef _SYS_TREE_H_
62#include <sys/tree.h>
63#endif
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64#ifndef _SYS_BIO_H_
65#include <sys/bio.h>
66#endif
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67#ifndef _SYS_SPINLOCK_H_
68#include <sys/spinlock.h>
69#endif
1eabbf32 70
984263bc 71struct buf;
81b5c339 72struct bio;
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73struct mount;
74struct vnode;
54f51aeb 75struct xio;
984263bc 76
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77#define NBUF_BIO 4
78
6bae6177 79struct buf_rb_tree;
1f1ea522 80struct buf_rb_hash;
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81RB_PROTOTYPE2(buf_rb_tree, buf, b_rbnode, rb_buf_compare, off_t);
82RB_PROTOTYPE2(buf_rb_hash, buf, b_rbhash, rb_buf_compare, off_t);
6bae6177 83
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84/*
85 * To avoid including <ufs/ffs/softdep.h>
86 */
87LIST_HEAD(workhead, worklist);
984263bc 88
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89#endif
90
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91typedef enum buf_cmd {
92 BUF_CMD_DONE = 0,
93 BUF_CMD_READ,
94 BUF_CMD_WRITE,
95 BUF_CMD_FREEBLKS,
96 BUF_CMD_FORMAT
97} buf_cmd_t;
98
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99#if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
100
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101/*
102 * The buffer header describes an I/O operation in the kernel.
103 *
104 * NOTES:
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105 * b_bufsize represents the filesystem block size (for this particular
106 * block) and/or the allocation size or original request size. This
107 * field is NOT USED by lower device layers. VNode and device
108 * strategy routines WILL NEVER ACCESS THIS FIELD.
984263bc 109 *
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110 * b_bcount represents the I/O request size. Unless B_NOBCLIP is set,
111 * the device chain is allowed to clip b_bcount to accomodate the device
112 * EOF. Note that this is different from the byte oriented file EOF.
113 * If B_NOBCLIP is set, the device chain is required to generate an
114 * error if it would othrewise have to clip the request. Buffers
115 * obtained via getblk() automatically set B_NOBCLIP. It is important
116 * to note that EOF clipping via b_bcount is different from EOF clipping
117 * via returning a b_actual < b_bcount. B_NOBCLIP only effects block
118 * oriented EOF clipping (b_bcount modifications).
984263bc 119 *
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120 * b_actual represents the number of bytes of I/O that actually occured,
121 * whether an error occured or not. b_actual must be initialized to 0
122 * prior to initiating I/O as the device drivers will assume it to
123 * start at 0.
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124 *
125 * b_dirtyoff, b_dirtyend. Buffers support piecemeal, unaligned
126 * ranges of dirty data that need to be written to backing store.
127 * The range is typically clipped at b_bcount (not b_bufsize).
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128 *
129 * b_bio1 and b_bio2 represent the two primary I/O layers. Additional
130 * I/O layers are allocated out of the object cache and may also exist.
131 *
132 * b_bio1 is the logical layer and contains offset or block number
133 * data for the primary vnode, b_vp. I/O operations are almost
134 * universally initiated from the logical layer, so you will often
135 * see things like: vn_strategy(bp->b_vp, &bp->b_bio1).
136 *
137 * b_bio2 is the first physical layer (typically the slice-relative
138 * layer) and contains the translated offset or block number for
139 * the block device underlying a filesystem. Filesystems such as UFS
140 * will maintain cached translations and you may see them initiate
141 * a 'physical' I/O using vn_strategy(devvp, &bp->b_bio2). BUT,
142 * remember that the layering is relative to bp->b_vp, so the
143 * device-relative block numbers for buffer cache operations that occur
144 * directly on a block device will be in the first BIO layer.
145 *
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146 * b_ops - initialized if a buffer has a bio_ops
147 *
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148 * NOTE!!! Only the BIO subsystem accesses b_bio1 and b_bio2 directly.
149 * ALL STRATEGY LAYERS FOR BOTH VNODES AND DEVICES ONLY ACCESS THE BIO
150 * PASSED TO THEM, AND WILL PUSH ANOTHER BIO LAYER IF FORWARDING THE
151 * I/O DEEPER. In particular, a vn_strategy() or dev_dstrategy()
152 * call should not ever access buf->b_vp as this vnode may be totally
153 * unrelated to the vnode/device whos strategy routine was called.
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154 */
155struct buf {
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156 RB_ENTRY(buf) b_rbnode; /* RB node in vnode clean/dirty tree */
157 RB_ENTRY(buf) b_rbhash; /* RB node in vnode hash tree */
984263bc 158 TAILQ_ENTRY(buf) b_freelist; /* Free list position if not active. */
81b5c339 159 struct buf *b_cluster_next; /* Next buffer (cluster code) */
54078292 160 struct vnode *b_vp; /* (vp, loffset) index */
81b5c339 161 struct bio b_bio_array[NBUF_BIO]; /* BIO translation layers */
54078292 162 u_int32_t b_flags; /* B_* flags. */
984263bc 163 unsigned short b_qindex; /* buffer queue index */
9e45bec7 164 unsigned short b_unused01;
984263bc 165 struct lock b_lock; /* Buffer lock */
10f3fee5 166 buf_cmd_t b_cmd; /* I/O command */
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167 int b_bufsize; /* Allocated buffer size. */
168 int b_runningbufspace; /* when I/O is running, pipelining */
169 int b_bcount; /* Valid bytes in buffer. */
170 int b_resid; /* Remaining I/O */
81b5c339 171 int b_error; /* Error return */
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172 caddr_t b_data; /* Memory, superblocks, indirect etc. */
173 caddr_t b_kvabase; /* base kva for buffer */
174 int b_kvasize; /* size of kva for buffer */
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175 int b_dirtyoff; /* Offset in buffer of dirty region. */
176 int b_dirtyend; /* Offset of end of dirty region. */
81b5c339 177 struct xio b_xio; /* data buffer page list management */
408357d8 178 struct bio_ops *b_ops; /* bio_ops used w/ b_dep */
984263bc 179 struct workhead b_dep; /* List of filesystem dependencies. */
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180};
181
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182/*
183 * XXX temporary
184 */
185#define b_bio1 b_bio_array[0] /* logical layer */
186#define b_bio2 b_bio_array[1] /* (typically) the disk layer */
187#define b_loffset b_bio1.bio_offset
984263bc 188
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189
190/*
191 * Flags passed to getblk()
192 *
193 * GETBLK_PCATCH - Allow signals to be caught. getblk() is allowed to return
194 * NULL if this flag is passed.
195 *
196 * GETBLK_BHEAVY - This is a heavy weight buffer, meaning that resolving
197 * writes can require additional buffers.
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198 *
199 * GETBLK_SZMATCH- blksize must match pre-existing b_bcount. getblk() can
200 * return NULL.
201 *
202 * GETBLK_NOWAIT - Do not use a blocking lock. getblk() can return NULL.
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203 */
204#define GETBLK_PCATCH 0x0001 /* catch signals */
205#define GETBLK_BHEAVY 0x0002 /* heavy weight buffer */
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206#define GETBLK_SZMATCH 0x0004 /* pre-existing buffer must match */
207#define GETBLK_NOWAIT 0x0008 /* non-blocking */
4b958e7b 208
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209/*
210 * These flags are kept in b_flags.
211 *
212 * Notes:
213 *
214 * B_ASYNC VOP calls on bp's are usually async whether or not
215 * B_ASYNC is set, but some subsystems, such as NFS, like
216 * to know what is best for the caller so they can
217 * optimize the I/O.
218 *
219 * B_PAGING Indicates that bp is being used by the paging system or
220 * some paging system and that the bp is not linked into
221 * the b_vp's clean/dirty linked lists or ref counts.
222 * Buffer vp reassignments are illegal in this case.
223 *
224 * B_CACHE This may only be set if the buffer is entirely valid.
225 * The situation where B_DELWRI is set and B_CACHE is
226 * clear MUST be committed to disk by getblk() so
227 * B_DELWRI can also be cleared. See the comments for
228 * getblk() in kern/vfs_bio.c. If B_CACHE is clear,
229 * the caller is expected to clear B_ERROR|B_INVAL,
10f3fee5 230 * set BUF_CMD_READ, and initiate an I/O.
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231 *
232 * The 'entire buffer' is defined to be the range from
233 * 0 through b_bcount.
234 *
235 * B_MALLOC Request that the buffer be allocated from the malloc
236 * pool, DEV_BSIZE aligned instead of PAGE_SIZE aligned.
237 *
238 * B_CLUSTEROK This flag is typically set for B_DELWRI buffers
239 * by filesystems that allow clustering when the buffer
240 * is fully dirty and indicates that it may be clustered
241 * with other adjacent dirty buffers. Note the clustering
242 * may not be used with the stage 1 data write under NFS
243 * but may be used for the commit rpc portion.
244 *
245 * B_VMIO Indicates that the buffer is tied into an VM object.
246 * The buffer's data is always PAGE_SIZE aligned even
247 * if b_bufsize and b_bcount are not. ( b_bufsize is
248 * always at least DEV_BSIZE aligned, though ).
249 *
250 * B_DIRECT Hint that we should attempt to completely free
251 * the pages underlying the buffer. B_DIRECT is
252 * sticky until the buffer is released and typically
253 * only has an effect when B_RELBUF is also set.
254 *
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255 * B_LOCKED The buffer will be released to the locked queue
256 * regardless of its current state. Note that
257 * if B_DELWRI is set, no I/O occurs until the caller
258 * acquires the buffer, clears B_LOCKED, then releases
259 * it again.
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260 *
261 * B_AGE When allocating a new buffer any buffer encountered
262 * with B_AGE set will be reallocated more quickly then
263 * buffers encountered without it set. B_AGE is set
264 * as part of the loop so idle buffers should eventually
265 * wind up with B_AGE set. B_AGE explicitly does NOT
266 * cause the buffer to be instantly reallocated for
267 * other purposes.
268 *
269 * Standard buffer flushing routines leave B_AGE intact
270 * through the DIRTY queue and into the CLEAN queue.
271 * Setting B_AGE on a dirty buffer will not cause it
272 * to be flushed more quickly but will cause it to be
273 * reallocated more quickly after having been flushed.
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274 *
275 * B_NOCACHE Request that the buffer and backing store be
276 * destroyed on completion. If B_DELWRI is set and the
277 * write fails, the buffer remains intact.
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278 */
279
b86460bf 280#define B_AGE 0x00000001 /* Reuse more quickly */
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281#define B_NEEDCOMMIT 0x00000002 /* Append-write in progress. */
282#define B_ASYNC 0x00000004 /* Start I/O, do not wait. */
283#define B_DIRECT 0x00000008 /* direct I/O flag (pls free vmio) */
b86460bf 284#define B_DEFERRED 0x00000010 /* vfs-controlled deferment */
984263bc 285#define B_CACHE 0x00000020 /* Bread found us in the cache. */
1f1ea522 286#define B_HASHED 0x00000040 /* Indexed via v_rbhash_tree */
984263bc 287#define B_DELWRI 0x00000080 /* Delay I/O until buffer reused. */
4414f2c9 288#define B_BNOCLIP 0x00000100 /* EOF clipping b_bcount not allowed */
10f3fee5 289#define B_UNUSED0200 0x00000200
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290#define B_EINTR 0x00000400 /* I/O was interrupted */
291#define B_ERROR 0x00000800 /* I/O error occurred. */
71bc1d95 292#define B_UNUSED1000 0x00001000 /* Unused */
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293#define B_INVAL 0x00002000 /* Does not contain valid info. */
294#define B_LOCKED 0x00004000 /* Locked in core (not reusable). */
135bd6a8 295#define B_NOCACHE 0x00008000 /* Destroy buffer AND backing store */
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296#define B_MALLOC 0x00010000 /* malloced b_data */
297#define B_CLUSTEROK 0x00020000 /* Pagein op, so swap() can count it. */
9fd739f4 298#define B_UNUSED40000 0x00040000
984263bc 299#define B_RAW 0x00080000 /* Set by physio for raw transfers. */
4b958e7b 300#define B_HEAVY 0x00100000 /* Heavy-weight buffer */
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301#define B_DIRTY 0x00200000 /* Needs writing later. */
302#define B_RELBUF 0x00400000 /* Release VMIO buffer. */
303#define B_WANT 0x00800000 /* Used by vm_pager.c */
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304#define B_VNCLEAN 0x01000000 /* On vnode clean list */
305#define B_VNDIRTY 0x02000000 /* On vnode dirty list */
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306#define B_PAGING 0x04000000 /* volatile paging I/O -- bypass VMIO */
307#define B_ORDERED 0x08000000 /* Must guarantee I/O ordering */
308#define B_RAM 0x10000000 /* Read ahead mark (flag) */
309#define B_VMIO 0x20000000 /* VMIO flag */
310#define B_CLUSTER 0x40000000 /* pagein op, so swap() can count it */
f2d7fcf0 311#define B_UNUSED80000000 0x80000000
984263bc 312
9e45bec7 313#define PRINT_BUF_FLAGS "\20" \
f2d7fcf0 314 "\40unused31\37cluster\36vmio\35ram\34ordered" \
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315 "\33paging\32vndirty\31vnclean\30want\27relbuf\26dirty" \
316 "\25unused20\24raw\23unused18\22clusterok\21malloc\20nocache" \
1b30fbcc 317 "\17locked\16inval\15unused12\14error\13eintr\12unused9\11bnoclip" \
9e45bec7 318 "\10delwri\7hashed\6cache\5deferred\4direct\3async\2needcommit\1age"
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319
320#define NOOFFSET (-1LL) /* No buffer offset calculated yet */
321
322#ifdef _KERNEL
323/*
3020e3be 324 * Buffer locking. See sys/buf2.h for inline functions.
984263bc 325 */
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326extern char *buf_wmesg; /* Default buffer lock message */
327#define BUF_WMESG "bufwait"
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328
329#endif /* _KERNEL */
330
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331struct bio_queue_head {
332 TAILQ_HEAD(bio_queue, bio) queue;
54078292 333 off_t last_offset;
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334 struct bio *insert_point;
335 struct bio *switch_point;
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336};
337
338/*
54078292 339 * This structure describes a clustered I/O.
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340 */
341struct cluster_save {
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342 int bs_nchildren; /* Number of associated buffers. */
343 struct buf **bs_children; /* List of associated buffers. */
344};
345
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346/*
347 * Zero out the buffer's data area.
348 */
349#define clrbuf(bp) { \
350 bzero((bp)->b_data, (u_int)(bp)->b_bcount); \
351 (bp)->b_resid = 0; \
352}
353
354/*
355 * Flags to low-level bitmap allocation routines (balloc).
356 *
357 * Note: sequential_heuristic() in kern/vfs_vnops.c limits the count
358 * to 127.
359 */
360#define B_SEQMASK 0x7F000000 /* Sequential heuristic mask. */
361#define B_SEQSHIFT 24 /* Sequential heuristic shift. */
362#define B_SEQMAX 0x7F
363#define B_CLRBUF 0x01 /* Cleared invalid areas of buffer. */
364#define B_SYNC 0x02 /* Do all allocations synchronously. */
365
366#ifdef _KERNEL
367extern int nbuf; /* The number of buffer headers */
368extern int maxswzone; /* Max KVA for swap structures */
369extern int maxbcache; /* Max KVA for buffer cache */
370extern int runningbufspace;
1b30fbcc 371extern int runningbufcount;
868d24af 372extern int hidirtybufspace;
984263bc 373extern int buf_maxio; /* nominal maximum I/O for buffer */
41cbf46c 374extern struct buf *buf; /* The buffer headers. */
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375extern char *buffers; /* The buffer contents. */
376extern int bufpages; /* Number of memory pages in the buffer pool. */
377extern struct buf *swbuf; /* Swap I/O buffer headers. */
378extern int nswbuf; /* Number of swap I/O buffer headers. */
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379
380struct uio;
381
b153f746 382void bufinit (void);
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383int bd_heatup (void);
384void bd_wait (int count);
b153f746 385int buf_dirty_count_severe (void);
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386void initbufbio(struct buf *);
387void reinitbufbio(struct buf *);
388void clearbiocache(struct bio *);
b153f746 389void bremfree (struct buf *);
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390int bread (struct vnode *, off_t, int, struct buf **);
391int breadn (struct vnode *, off_t, int, off_t *, int *, int,
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392 struct buf **);
393int bwrite (struct buf *);
394void bdwrite (struct buf *);
395void bawrite (struct buf *);
396void bdirty (struct buf *);
4b958e7b 397void bheavy (struct buf *);
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398void bundirty (struct buf *);
399int bowrite (struct buf *);
400void brelse (struct buf *);
401void bqrelse (struct buf *);
402int vfs_bio_awrite (struct buf *);
81b5c339 403struct buf *getpbuf (int *);
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404int inmem (struct vnode *, off_t);
405struct buf *findblk (struct vnode *, off_t);
406struct buf *getblk (struct vnode *, off_t, int, int, int);
b153f746 407struct buf *geteblk (int);
5e23ca53 408void regetblk(struct buf *bp);
81b5c339 409struct bio *push_bio(struct bio *);
b77cfc40 410struct bio *pop_bio(struct bio *);
b153f746 411int biowait (struct buf *);
81b5c339 412void biodone (struct bio *);
984263bc 413
81b5c339 414void cluster_append(struct bio *, struct buf *);
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415int cluster_read (struct vnode *, off_t, off_t, int,
416 int, int, struct buf **);
417int cluster_wbuild (struct vnode *, int, off_t, int);
e92ca23a 418void cluster_write (struct buf *, off_t, int, int);
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419int physread (struct dev_read_args *);
420int physwrite (struct dev_write_args *);
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421void vfs_bio_set_validclean (struct buf *, int base, int size);
422void vfs_bio_clrbuf (struct buf *);
10f3fee5 423void vfs_busy_pages (struct vnode *, struct buf *);
b153f746 424void vfs_unbusy_pages (struct buf *);
3591bbc6 425int vmapbuf (struct buf *, caddr_t, int);
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426void vunmapbuf (struct buf *);
427void relpbuf (struct buf *, int *);
428void brelvp (struct buf *);
429void bgetvp (struct vnode *, struct buf *);
b153f746 430int allocbuf (struct buf *bp, int size);
41cbf46c 431int scan_all_buffers (int (*)(struct buf *, void *), void *);
1f1ea522 432void reassignbuf (struct buf *);
b153f746 433struct buf *trypbuf (int *);
408357d8 434void bio_ops_sync(struct mount *mp);
984263bc 435
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436#endif /* _KERNEL */
437#endif /* _KERNEL || _KERNEL_STRUCTURES */
438#endif /* !_SYS_BUF_H_ */