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. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)buf.h 8.9 (Berkeley) 3/30/95 35 * $FreeBSD: src/sys/sys/buf.h,v 1.88.2.10 2003/01/25 19:02:23 dillon Exp $ 36 * $DragonFly: src/sys/sys/buf.h,v 1.54 2008/08/29 20:08:37 dillon Exp $ 37 */ 38 39 #ifndef _SYS_BUF_H_ 40 #define _SYS_BUF_H_ 41 42 #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES) 43 44 #ifndef _SYS_QUEUE_H_ 45 #include <sys/queue.h> 46 #endif 47 #ifndef _SYS_LOCK_H_ 48 #include <sys/lock.h> 49 #endif 50 #ifndef _SYS_DEVICE_H_ 51 #include <sys/device.h> 52 #endif 53 54 #ifndef _SYS_XIO_H_ 55 #include <sys/xio.h> 56 #endif 57 #ifndef _SYS_TREE_H_ 58 #include <sys/tree.h> 59 #endif 60 #ifndef _SYS_BIO_H_ 61 #include <sys/bio.h> 62 #endif 63 #ifndef _SYS_SPINLOCK_H_ 64 #include <sys/spinlock.h> 65 #endif 66 67 struct buf; 68 struct bio; 69 struct mount; 70 struct vnode; 71 struct xio; 72 73 #define NBUF_BIO 6 74 75 struct buf_rb_tree; 76 struct buf_rb_hash; 77 RB_PROTOTYPE2(buf_rb_tree, buf, b_rbnode, rb_buf_compare, off_t); 78 RB_PROTOTYPE2(buf_rb_hash, buf, b_rbhash, rb_buf_compare, off_t); 79 80 /* 81 * To avoid including <ufs/ffs/softdep.h> 82 */ 83 LIST_HEAD(workhead, worklist); 84 85 #endif 86 87 typedef enum buf_cmd { 88 BUF_CMD_DONE = 0, 89 BUF_CMD_READ, 90 BUF_CMD_WRITE, 91 BUF_CMD_FREEBLKS, 92 BUF_CMD_FORMAT, 93 BUF_CMD_FLUSH 94 } buf_cmd_t; 95 96 #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES) 97 98 /* 99 * The buffer header describes an I/O operation in the kernel. 100 * 101 * NOTES: 102 * b_bufsize represents the filesystem block size (for this particular 103 * block) and/or the allocation size or original request size. This 104 * field is NOT USED by lower device layers. VNode and device 105 * strategy routines WILL NEVER ACCESS THIS FIELD. 106 * 107 * b_bcount represents the I/O request size. Unless B_NOBCLIP is set, 108 * the device chain is allowed to clip b_bcount to accomodate the device 109 * EOF. Note that this is different from the byte oriented file EOF. 110 * If B_NOBCLIP is set, the device chain is required to generate an 111 * error if it would othrewise have to clip the request. Buffers 112 * obtained via getblk() automatically set B_NOBCLIP. It is important 113 * to note that EOF clipping via b_bcount is different from EOF clipping 114 * via returning a b_actual < b_bcount. B_NOBCLIP only effects block 115 * oriented EOF clipping (b_bcount modifications). 116 * 117 * b_actual represents the number of bytes of I/O that actually occured, 118 * whether an error occured or not. b_actual must be initialized to 0 119 * prior to initiating I/O as the device drivers will assume it to 120 * start at 0. 121 * 122 * b_dirtyoff, b_dirtyend. Buffers support piecemeal, unaligned 123 * ranges of dirty data that need to be written to backing store. 124 * The range is typically clipped at b_bcount (not b_bufsize). 125 * 126 * b_bio1 and b_bio2 represent the two primary I/O layers. Additional 127 * I/O layers are allocated out of the object cache and may also exist. 128 * 129 * b_bio1 is the logical layer and contains offset or block number 130 * data for the primary vnode, b_vp. I/O operations are almost 131 * universally initiated from the logical layer, so you will often 132 * see things like: vn_strategy(bp->b_vp, &bp->b_bio1). 133 * 134 * b_bio2 is the first physical layer (typically the slice-relative 135 * layer) and contains the translated offset or block number for 136 * the block device underlying a filesystem. Filesystems such as UFS 137 * will maintain cached translations and you may see them initiate 138 * a 'physical' I/O using vn_strategy(devvp, &bp->b_bio2). BUT, 139 * remember that the layering is relative to bp->b_vp, so the 140 * device-relative block numbers for buffer cache operations that occur 141 * directly on a block device will be in the first BIO layer. 142 * 143 * b_ops - initialized if a buffer has a bio_ops 144 * 145 * NOTE!!! Only the BIO subsystem accesses b_bio1 and b_bio2 directly. 146 * ALL STRATEGY LAYERS FOR BOTH VNODES AND DEVICES ONLY ACCESS THE BIO 147 * PASSED TO THEM, AND WILL PUSH ANOTHER BIO LAYER IF FORWARDING THE 148 * I/O DEEPER. In particular, a vn_strategy() or dev_dstrategy() 149 * call should not ever access buf->b_vp as this vnode may be totally 150 * unrelated to the vnode/device whos strategy routine was called. 151 */ 152 struct buf { 153 RB_ENTRY(buf) b_rbnode; /* RB node in vnode clean/dirty tree */ 154 RB_ENTRY(buf) b_rbhash; /* RB node in vnode hash tree */ 155 TAILQ_ENTRY(buf) b_freelist; /* Free list position if not active. */ 156 struct buf *b_cluster_next; /* Next buffer (cluster code) */ 157 struct vnode *b_vp; /* (vp, loffset) index */ 158 struct bio b_bio_array[NBUF_BIO]; /* BIO translation layers */ 159 u_int32_t b_flags; /* B_* flags. */ 160 unsigned int b_qindex; /* buffer queue index */ 161 unsigned int b_qcpu; /* buffer queue cpu */ 162 unsigned char b_act_count; /* similar to vm_page act_count */ 163 unsigned char b_swindex; 164 cpumask_t b_cpumask; /* KVABIO API */ 165 struct lock b_lock; /* Buffer lock */ 166 buf_cmd_t b_cmd; /* I/O command */ 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 */ 171 int b_error; /* Error return */ 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 */ 175 int b_dirtyoff; /* Offset in buffer of dirty region. */ 176 int b_dirtyend; /* Offset of end of dirty region. */ 177 int b_refs; /* FINDBLK_REF/bqhold()/bqdrop() */ 178 struct xio b_xio; /* data buffer page list management */ 179 struct bio_ops *b_ops; /* bio_ops used w/ b_dep */ 180 union { 181 struct workhead b_dep; /* List of filesystem dependencies. */ 182 void *b_priv; /* Filesystem private data */ 183 }; 184 }; 185 186 /* 187 * XXX temporary 188 */ 189 #define b_bio1 b_bio_array[0] /* logical layer */ 190 #define b_bio2 b_bio_array[1] /* (typically) the disk layer */ 191 #define b_loffset b_bio1.bio_offset 192 193 194 /* 195 * Flags passed to getblk() 196 * 197 * GETBLK_PCATCH - Allow signals to be caught. getblk() is allowed to return 198 * NULL if this flag is passed. 199 * 200 * GETBLK_BHEAVY - This is a heavy weight buffer, meaning that resolving 201 * writes can require additional buffers. 202 * 203 * GETBLK_SZMATCH- blksize must match pre-existing b_bcount. getblk() can 204 * return NULL. 205 * 206 * GETBLK_NOWAIT - Do not use a blocking lock. getblk() can return NULL. 207 */ 208 #define GETBLK_PCATCH 0x0001 /* catch signals */ 209 #define GETBLK_BHEAVY 0x0002 /* heavy weight buffer */ 210 #define GETBLK_SZMATCH 0x0004 /* pre-existing buffer must match */ 211 #define GETBLK_NOWAIT 0x0008 /* non-blocking */ 212 #define GETBLK_KVABIO 0x0010 /* request a B_KVABIO buffer */ 213 214 #define FINDBLK_TEST 0x0020 /* test only, do not lock */ 215 #define FINDBLK_NBLOCK 0x0040 /* use non-blocking lock, can return NULL */ 216 #define FINDBLK_REF 0x0080 /* ref the buf to prevent reuse */ 217 #define FINDBLK_KVABIO 0x0100 /* (if locking only) request B_KVABIO buffer */ 218 219 /* 220 * These flags are kept in b_flags. 221 * 222 * Notes: 223 * 224 * B_PAGING Indicates that bp is being used by the paging system or 225 * some paging system and that the bp is not linked into 226 * the b_vp's clean/dirty linked lists or ref counts. 227 * Buffer vp reassignments are illegal in this case. 228 * 229 * B_CACHE This may only be set if the buffer is entirely valid. 230 * The situation where B_DELWRI is set and B_CACHE is 231 * clear MUST be committed to disk by getblk() so 232 * B_DELWRI can also be cleared. See the comments for 233 * getblk() in kern/vfs_bio.c. If B_CACHE is clear, 234 * the caller is expected to clear B_ERROR|B_INVAL, 235 * set BUF_CMD_READ, and initiate an I/O. 236 * 237 * The 'entire buffer' is defined to be the range from 238 * 0 through b_bcount. 239 * 240 * B_CLUSTEROK This flag is typically set for B_DELWRI buffers 241 * by filesystems that allow clustering when the buffer 242 * is fully dirty and indicates that it may be clustered 243 * with other adjacent dirty buffers. Note the clustering 244 * may not be used with the stage 1 data write under NFS 245 * but may be used for the commit rpc portion. 246 * 247 * B_VMIO Indicates that the buffer is tied into an VM object. 248 * The buffer's data is always PAGE_SIZE aligned even 249 * if b_bufsize and b_bcount are not. ( b_bufsize is 250 * always at least DEV_BSIZE aligned, though ). 251 * 252 * B_DIRECT Hint that we should attempt to completely free 253 * the pages underlying the buffer. B_DIRECT is 254 * sticky until the buffer is released and typically 255 * only has an effect when B_RELBUF is also set. 256 * 257 * B_LOCKED The buffer will be released to the locked queue 258 * regardless of its current state. Note that 259 * if B_DELWRI is set, no I/O occurs until the caller 260 * acquires the buffer, clears B_LOCKED, then releases 261 * it again. 262 * 263 * B_AGE When allocating a new buffer any buffer encountered 264 * with B_AGE set will be reallocated more quickly then 265 * buffers encountered without it set. B_AGE is set 266 * as part of the loop so idle buffers should eventually 267 * wind up with B_AGE set. B_AGE explicitly does NOT 268 * cause the buffer to be instantly reallocated for 269 * other purposes. 270 * 271 * Standard buffer flushing routines leave B_AGE intact 272 * through the DIRTY queue and into the CLEAN queue. 273 * Setting B_AGE on a dirty buffer will not cause it 274 * to be flushed more quickly but will cause it to be 275 * reallocated more quickly after having been flushed. 276 * 277 * B_NOCACHE Request that the buffer and backing store be 278 * destroyed on completion. If B_DELWRI is set and the 279 * write fails, the buffer remains intact. 280 * 281 * B_NOTMETA May be set on block device buffers representing 282 * file data (i.e. which aren't really meta-data), 283 * which will cause the buffer cache to set PG_NOTMETA 284 * in the VM pages when releasing them and the 285 * swapcache to not try to cache them. 286 * 287 * B_MARKER Special marker buf, always skip. 288 * 289 * B_KVABIO Owner of buffer (but not necessarily the underlying 290 * vnode or device) supports the KVABIO API. The owner 291 * of the buffer will only operate on the buffer's 292 * b_data via the API. Locked buffers only. This 293 * flag is cleared on brelse/bqrelse 294 * 295 * WARNING! bp->b_data is not necessarily synchronized to the current cpu 296 * when B_KVABIO operations is specified. Callers using bp->b_data 297 * who specify B_KVABIO operation must call bkvasync() if they use 298 * bp->b_data directly, or whenever they pass a buffer between cpus 299 * (between threads, e.g. from helper threads) if the target thread 300 * intends to access bp->b_data. 301 */ 302 303 #define B_AGE 0x00000001 /* Reuse more quickly */ 304 #define B_NEEDCOMMIT 0x00000002 /* Append-write in progress. */ 305 #define B_NOTMETA 0x00000004 /* This really isn't metadata */ 306 #define B_DIRECT 0x00000008 /* direct I/O flag (pls free vmio) */ 307 #define B_DEFERRED 0x00000010 /* vfs-controlled deferment */ 308 #define B_CACHE 0x00000020 /* Bread found us in the cache. */ 309 #define B_HASHED 0x00000040 /* Indexed via v_rbhash_tree */ 310 #define B_DELWRI 0x00000080 /* Delay I/O until buffer reused. */ 311 #define B_BNOCLIP 0x00000100 /* EOF clipping b_bcount not allowed */ 312 #define B_HASBOGUS 0x00000200 /* Contains bogus pages */ 313 #define B_EINTR 0x00000400 /* I/O was interrupted */ 314 #define B_ERROR 0x00000800 /* I/O error occurred. */ 315 #define B_IOISSUED 0x00001000 /* Flag when I/O issued (vfs can clr) */ 316 #define B_INVAL 0x00002000 /* Does not contain valid info. */ 317 #define B_LOCKED 0x00004000 /* Locked in core (not reusable). */ 318 #define B_NOCACHE 0x00008000 /* Destroy buffer AND backing store */ 319 #define B_KVABIO 0x00010000 /* Lockholder uses the KVABIO API */ 320 #define B_CLUSTEROK 0x00020000 /* Pagein op, so swap() can count it. */ 321 #define B_MARKER 0x00040000 /* Special marker buf in queue */ 322 #define B_RAW 0x00080000 /* Set by physio for raw transfers. */ 323 #define B_HEAVY 0x00100000 /* Heavy-weight buffer */ 324 #define B_DIRTY 0x00200000 /* Needs writing later. */ 325 #define B_RELBUF 0x00400000 /* Release VMIO buffer. */ 326 #define B_FAILONDIS 0x00800000 /* Fail on disconnect */ 327 #define B_VNCLEAN 0x01000000 /* On vnode clean list */ 328 #define B_VNDIRTY 0x02000000 /* On vnode dirty list */ 329 #define B_PAGING 0x04000000 /* volatile paging I/O -- bypass VMIO */ 330 #define B_TTC 0x08000000 /* Try to recycle pages to PQ_CACHE */ 331 #define B_RAM 0x10000000 /* Read ahead mark (flag) */ 332 #define B_VMIO 0x20000000 /* VMIO flag */ 333 #define B_CLUSTER 0x40000000 /* pagein op, so swap() can count it */ 334 #define B_VFSFLAG1 0x80000000 /* VFSs can set this flag */ 335 336 #define PRINT_BUF_FLAGS "\20" \ 337 "\40unused31\37cluster\36vmio\35ram\34ordered" \ 338 "\33paging\32vndirty\31vnclean\30unused23\27relbuf\26dirty" \ 339 "\25unused20\24raw\23unused18\22clusterok\21malloc\20nocache" \ 340 "\17locked\16inval\15unused12\14error\13eintr\12unused9\11bnoclip" \ 341 "\10delwri\7hashed\6cache\5deferred\4direct\3unused2\2needcommit\1age" 342 343 #define NOOFFSET (-1LL) /* No buffer offset calculated yet */ 344 345 #ifdef _KERNEL 346 /* 347 * Buffer locking. See sys/buf2.h for inline functions. 348 */ 349 extern char *buf_wmesg; /* Default buffer lock message */ 350 #define BUF_WMESG "bufwait" 351 352 #endif /* _KERNEL */ 353 354 struct bio_queue_head { 355 TAILQ_HEAD(bio_queue, bio) queue; 356 off_t off_unused; 357 int reorder; 358 struct bio *transition; 359 struct bio *bio_unused; 360 }; 361 362 /* 363 * This structure describes a clustered I/O. 364 */ 365 struct cluster_save { 366 int bs_nchildren; /* Number of associated buffers. */ 367 struct buf **bs_children; /* List of associated buffers. */ 368 }; 369 370 /* 371 * Zero out the buffer's data area. 372 */ 373 #define clrbuf(bp) do { \ 374 bkvasync((bp)); \ 375 bzero((bp)->b_data, (u_int)(bp)->b_bcount); \ 376 (bp)->b_resid = 0; \ 377 } while(0) 378 379 /* 380 * Flags to low-level bitmap allocation routines (balloc). 381 * 382 * Note: sequential_heuristic() in kern/vfs_vnops.c limits the count 383 * to 127. 384 */ 385 #define B_SEQMASK 0x7F000000 /* Sequential heuristic mask. */ 386 #define B_SEQSHIFT 24 /* Sequential heuristic shift. */ 387 #define B_SEQMAX 0x7F 388 #define B_CLRBUF 0x01 /* Cleared invalid areas of buffer. */ 389 #define B_SYNC 0x02 /* Do all allocations synchronously. */ 390 391 /* 392 * Split nswbuf_kva by N, allowing each block device or mounted filesystem 393 * to use up to (nswbuf_kva / N) pbufs. 394 */ 395 #define NSWBUF_SPLIT 10 /* split nswbuf_kva by N */ 396 397 #ifdef _KERNEL 398 extern long nbuf; /* The number of buffer headers */ 399 extern long maxswzone; /* Max KVA for swap structures */ 400 extern long maxbcache; /* Max KVA for buffer cache */ 401 extern long hidirtybufspace; 402 extern int buf_maxio; /* nominal maximum I/O for buffer */ 403 extern struct buf *buf; /* The buffer headers. */ 404 extern char *buffers; /* The buffer contents. */ 405 extern int bufpages; /* Number of memory pages in the buffer pool. */ 406 extern struct buf *swbuf_mem; /* Swap I/O buffer headers. */ 407 extern struct buf *swbuf_kva; /* Swap I/O buffer headers. */ 408 extern struct buf *swbuf_raw; /* Swap I/O buffer headers. */ 409 extern long nswbuf_mem; /* Number of swap I/O buffer headers. */ 410 extern long nswbuf_kva; /* Number of swap I/O buffer headers. */ 411 extern long nswbuf_raw; /* Number of swap I/O buffer headers. */ 412 extern int bioq_reorder_burst_interval; 413 extern int bioq_reorder_burst_bytes; 414 extern int bioq_reorder_minor_interval; 415 extern int bioq_reorder_minor_bytes; 416 417 struct uio; 418 struct devstat; 419 420 long bd_heatup (void); 421 void bd_wait (long count); 422 void waitrunningbufspace(void); 423 int buf_dirty_count_severe (void); 424 int buf_runningbufspace_severe (void); 425 void initbufbio(struct buf *); 426 void uninitbufbio(struct buf *); 427 void reinitbufbio(struct buf *); 428 void clearbiocache(struct bio *); 429 void bremfree (struct buf *); 430 int breadx (struct vnode *, off_t, int, int, struct buf **); 431 int breadnx (struct vnode *, off_t, int, int, off_t *, int *, int, 432 struct buf **); 433 void breadcb(struct vnode *, off_t, int, int, 434 void (*)(struct bio *), void *); 435 int bwrite (struct buf *); 436 void bdwrite (struct buf *); 437 void buwrite (struct buf *); 438 void bawrite (struct buf *); 439 void bdirty (struct buf *); 440 void bheavy (struct buf *); 441 void bundirty (struct buf *); 442 void brelse (struct buf *); 443 void bqrelse (struct buf *); 444 int cluster_awrite (struct buf *); 445 446 void bkvareset(struct buf *bp); 447 void bkvasync(struct buf *bp); 448 void bkvasync_all(struct buf *bp); 449 450 struct buf *getpbuf (int *); 451 struct buf *getpbuf_mem (int *); 452 struct buf *getpbuf_kva (int *); 453 454 int inmem (struct vnode *, off_t); 455 struct buf *findblk (struct vnode *, off_t, int); 456 struct buf *getblk (struct vnode *, off_t, int, int, int); 457 struct buf *getcacheblk (struct vnode *, off_t, int, int); 458 struct buf *getnewbuf(int, int, int, int); 459 void bqhold(struct buf *bp); 460 void bqdrop(struct buf *bp); 461 void regetblk(struct buf *bp); 462 struct bio *push_bio(struct bio *); 463 struct bio *pop_bio(struct bio *); 464 int biowait (struct bio *, const char *); 465 int biowait_timeout (struct bio *, const char *, int); 466 void bpdone (struct buf *, int); 467 void biodone (struct bio *); 468 void biodone_sync (struct bio *); 469 void pbuf_adjcount(int *pfreecnt, int n); 470 471 void cluster_append(struct bio *, struct buf *); 472 int cluster_readx (struct vnode *, off_t, off_t, int, int, 473 size_t, size_t, struct buf **); 474 void cluster_readcb (struct vnode *, off_t, off_t, int, int, 475 size_t, size_t, void (*func)(struct bio *), void *arg); 476 void cluster_write (struct buf *, off_t, int, int); 477 int physread (struct dev_read_args *); 478 int physwrite (struct dev_write_args *); 479 void vfs_bio_clrbuf (struct buf *); 480 void vfs_busy_pages (struct vnode *, struct buf *); 481 void vfs_unbusy_pages (struct buf *); 482 void relpbuf (struct buf *, int *); 483 void brelvp (struct buf *); 484 int bgetvp (struct vnode *, struct buf *, int); 485 void bsetrunningbufspace(struct buf *, int); 486 void allocbuf (struct buf *bp, int size); 487 int scan_all_buffers (int (*)(struct buf *, void *), void *); 488 void reassignbuf (struct buf *); 489 struct buf *trypbuf (int *); 490 struct buf *trypbuf_kva (int *); 491 void bio_ops_sync(struct mount *mp); 492 void nestiobuf_done(struct bio *mbio, int donebytes, int error, struct devstat *stats); 493 void nestiobuf_init(struct bio *mbio); 494 void nestiobuf_add(struct bio *mbio, struct buf *bp, int off, size_t size, struct devstat *stats); 495 void nestiobuf_start(struct bio *mbio); 496 void nestiobuf_error(struct bio *mbio, int error); 497 const char *buf_cmd_name(struct buf *bp); 498 #endif /* _KERNEL */ 499 #endif /* _KERNEL || _KERNEL_STRUCTURES */ 500 #endif /* !_SYS_BUF_H_ */ 501