FreeBSD/Linux Kernel Cross Reference
sys/sys/buf.h
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 * 4. 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 1.207 2008/03/28 12:30:12 attilio Exp $
36 */
37
38 #ifndef _SYS_BUF_H_
39 #define _SYS_BUF_H_
40
41 #include <sys/bufobj.h>
42 #include <sys/queue.h>
43 #include <sys/lock.h>
44 #include <sys/lockmgr.h>
45
46 struct bio;
47 struct buf;
48 struct bufobj;
49 struct mount;
50 struct vnode;
51 struct uio;
52
53 /*
54 * To avoid including <ufs/ffs/softdep.h>
55 */
56 LIST_HEAD(workhead, worklist);
57 /*
58 * These are currently used only by the soft dependency code, hence
59 * are stored once in a global variable. If other subsystems wanted
60 * to use these hooks, a pointer to a set of bio_ops could be added
61 * to each buffer.
62 */
63 extern struct bio_ops {
64 void (*io_start)(struct buf *);
65 void (*io_complete)(struct buf *);
66 void (*io_deallocate)(struct buf *);
67 int (*io_countdeps)(struct buf *, int);
68 } bioops;
69
70 struct vm_object;
71
72 typedef unsigned char b_xflags_t;
73
74 /*
75 * The buffer header describes an I/O operation in the kernel.
76 *
77 * NOTES:
78 * b_bufsize, b_bcount. b_bufsize is the allocation size of the
79 * buffer, either DEV_BSIZE or PAGE_SIZE aligned. b_bcount is the
80 * originally requested buffer size and can serve as a bounds check
81 * against EOF. For most, but not all uses, b_bcount == b_bufsize.
82 *
83 * b_dirtyoff, b_dirtyend. Buffers support piecemeal, unaligned
84 * ranges of dirty data that need to be written to backing store.
85 * The range is typically clipped at b_bcount ( not b_bufsize ).
86 *
87 * b_resid. Number of bytes remaining in I/O. After an I/O operation
88 * completes, b_resid is usually 0 indicating 100% success.
89 *
90 * All fields are protected by the buffer lock except those marked:
91 * V - Protected by owning bufobj lock
92 * Q - Protected by the buf queue lock
93 * D - Protected by an dependency implementation specific lock
94 */
95 struct buf {
96 struct bufobj *b_bufobj;
97 long b_bcount;
98 void *b_caller1;
99 caddr_t b_data;
100 int b_error;
101 uint8_t b_iocmd;
102 uint8_t b_ioflags;
103 off_t b_iooffset;
104 long b_resid;
105 void (*b_iodone)(struct buf *);
106 daddr_t b_blkno; /* Underlying physical block number. */
107 off_t b_offset; /* Offset into file. */
108 TAILQ_ENTRY(buf) b_bobufs; /* (V) Buffer's associated vnode. */
109 struct buf *b_left; /* (V) splay tree link */
110 struct buf *b_right; /* (V) splay tree link */
111 uint32_t b_vflags; /* (V) BV_* flags */
112 TAILQ_ENTRY(buf) b_freelist; /* (Q) Free list position inactive. */
113 unsigned short b_qindex; /* (Q) buffer queue index */
114 uint32_t b_flags; /* B_* flags. */
115 b_xflags_t b_xflags; /* extra flags */
116 struct lock b_lock; /* Buffer lock */
117 long b_bufsize; /* Allocated buffer size. */
118 long b_runningbufspace; /* when I/O is running, pipelining */
119 caddr_t b_kvabase; /* base kva for buffer */
120 int b_kvasize; /* size of kva for buffer */
121 daddr_t b_lblkno; /* Logical block number. */
122 struct vnode *b_vp; /* Device vnode. */
123 int b_dirtyoff; /* Offset in buffer of dirty region. */
124 int b_dirtyend; /* Offset of end of dirty region. */
125 struct ucred *b_rcred; /* Read credentials reference. */
126 struct ucred *b_wcred; /* Write credentials reference. */
127 void *b_saveaddr; /* Original b_addr for physio. */
128 union pager_info {
129 int pg_reqpage;
130 } b_pager;
131 union cluster_info {
132 TAILQ_HEAD(cluster_list_head, buf) cluster_head;
133 TAILQ_ENTRY(buf) cluster_entry;
134 } b_cluster;
135 struct vm_page *b_pages[btoc(MAXPHYS)];
136 int b_npages;
137 struct workhead b_dep; /* (D) List of filesystem dependencies. */
138 void *b_fsprivate1;
139 void *b_fsprivate2;
140 void *b_fsprivate3;
141 int b_pin_count;
142 };
143
144 #define b_object b_bufobj->bo_object
145
146 /*
147 * These flags are kept in b_flags.
148 *
149 * Notes:
150 *
151 * B_ASYNC VOP calls on bp's are usually async whether or not
152 * B_ASYNC is set, but some subsystems, such as NFS, like
153 * to know what is best for the caller so they can
154 * optimize the I/O.
155 *
156 * B_PAGING Indicates that bp is being used by the paging system or
157 * some paging system and that the bp is not linked into
158 * the b_vp's clean/dirty linked lists or ref counts.
159 * Buffer vp reassignments are illegal in this case.
160 *
161 * B_CACHE This may only be set if the buffer is entirely valid.
162 * The situation where B_DELWRI is set and B_CACHE is
163 * clear MUST be committed to disk by getblk() so
164 * B_DELWRI can also be cleared. See the comments for
165 * getblk() in kern/vfs_bio.c. If B_CACHE is clear,
166 * the caller is expected to clear BIO_ERROR and B_INVAL,
167 * set BIO_READ, and initiate an I/O.
168 *
169 * The 'entire buffer' is defined to be the range from
170 * 0 through b_bcount.
171 *
172 * B_MALLOC Request that the buffer be allocated from the malloc
173 * pool, DEV_BSIZE aligned instead of PAGE_SIZE aligned.
174 *
175 * B_CLUSTEROK This flag is typically set for B_DELWRI buffers
176 * by filesystems that allow clustering when the buffer
177 * is fully dirty and indicates that it may be clustered
178 * with other adjacent dirty buffers. Note the clustering
179 * may not be used with the stage 1 data write under NFS
180 * but may be used for the commit rpc portion.
181 *
182 * B_VMIO Indicates that the buffer is tied into an VM object.
183 * The buffer's data is always PAGE_SIZE aligned even
184 * if b_bufsize and b_bcount are not. ( b_bufsize is
185 * always at least DEV_BSIZE aligned, though ).
186 *
187 * B_DIRECT Hint that we should attempt to completely free
188 * the pages underlying the buffer. B_DIRECT is
189 * sticky until the buffer is released and typically
190 * only has an effect when B_RELBUF is also set.
191 *
192 */
193
194 #define B_AGE 0x00000001 /* Move to age queue when I/O done. */
195 #define B_NEEDCOMMIT 0x00000002 /* Append-write in progress. */
196 #define B_ASYNC 0x00000004 /* Start I/O, do not wait. */
197 #define B_DIRECT 0x00000008 /* direct I/O flag (pls free vmio) */
198 #define B_DEFERRED 0x00000010 /* Skipped over for cleaning */
199 #define B_CACHE 0x00000020 /* Bread found us in the cache. */
200 #define B_VALIDSUSPWRT 0x00000040 /* Valid write during suspension. */
201 #define B_DELWRI 0x00000080 /* Delay I/O until buffer reused. */
202 #define B_PERSISTENT 0x00000100 /* Perm. ref'ed while EXT2FS mounted. */
203 #define B_DONE 0x00000200 /* I/O completed. */
204 #define B_EINTR 0x00000400 /* I/O was interrupted */
205 #define B_00000800 0x00000800 /* Available flag. */
206 #define B_00001000 0x00001000 /* Available flag. */
207 #define B_INVAL 0x00002000 /* Does not contain valid info. */
208 #define B_00004000 0x00004000 /* Available flag. */
209 #define B_NOCACHE 0x00008000 /* Do not cache block after use. */
210 #define B_MALLOC 0x00010000 /* malloced b_data */
211 #define B_CLUSTEROK 0x00020000 /* Pagein op, so swap() can count it. */
212 #define B_000400000 0x00040000 /* Available flag. */
213 #define B_000800000 0x00080000 /* Available flag. */
214 #define B_00100000 0x00100000 /* Available flag. */
215 #define B_DIRTY 0x00200000 /* Needs writing later (in EXT2FS). */
216 #define B_RELBUF 0x00400000 /* Release VMIO buffer. */
217 #define B_00800000 0x00800000 /* Available flag. */
218 #define B_01000000 0x01000000 /* Available flag. */
219 #define B_NEEDSGIANT 0x02000000 /* Buffer's vnode needs giant. */
220 #define B_PAGING 0x04000000 /* volatile paging I/O -- bypass VMIO */
221 #define B_MANAGED 0x08000000 /* Managed by FS. */
222 #define B_RAM 0x10000000 /* Read ahead mark (flag) */
223 #define B_VMIO 0x20000000 /* VMIO flag */
224 #define B_CLUSTER 0x40000000 /* pagein op, so swap() can count it */
225 #define B_REMFREE 0x80000000 /* Delayed bremfree */
226
227 #define PRINT_BUF_FLAGS "\2\40remfree\37cluster\36vmio\35ram\34b27" \
228 "\33paging\32b25\31b24\30b23\27relbuf\26dirty\25b20" \
229 "\24b19\23b18\22clusterok\21malloc\20nocache\17b14\16inval" \
230 "\15b12\14b11\13eintr\12done\11persist\10delwri\7validsuspwrt" \
231 "\6cache\5deferred\4direct\3async\2needcommit\1age"
232
233 /*
234 * These flags are kept in b_xflags.
235 */
236 #define BX_VNDIRTY 0x00000001 /* On vnode dirty list */
237 #define BX_VNCLEAN 0x00000002 /* On vnode clean list */
238 #define BX_BKGRDWRITE 0x00000010 /* Do writes in background */
239 #define BX_BKGRDMARKER 0x00000020 /* Mark buffer for splay tree */
240 #define BX_ALTDATA 0x00000040 /* Holds extended data */
241
242 #define NOOFFSET (-1LL) /* No buffer offset calculated yet */
243
244 /*
245 * These flags are kept in b_vflags.
246 */
247 #define BV_SCANNED 0x00000001 /* VOP_FSYNC funcs mark written bufs */
248 #define BV_BKGRDINPROG 0x00000002 /* Background write in progress */
249 #define BV_BKGRDWAIT 0x00000004 /* Background write waiting */
250
251 #ifdef _KERNEL
252 /*
253 * Buffer locking
254 */
255 extern const char *buf_wmesg; /* Default buffer lock message */
256 #define BUF_WMESG "bufwait"
257 #include <sys/proc.h> /* XXX for curthread */
258 #include <sys/mutex.h>
259
260 /*
261 * Initialize a lock.
262 */
263 #define BUF_LOCKINIT(bp) \
264 lockinit(&(bp)->b_lock, PRIBIO + 4, buf_wmesg, 0, 0)
265 /*
266 *
267 * Get a lock sleeping non-interruptably until it becomes available.
268 */
269 #define BUF_LOCK(bp, locktype, interlock) \
270 _lockmgr_args(&(bp)->b_lock, (locktype), (interlock), \
271 LK_WMESG_DEFAULT, LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, \
272 LOCK_FILE, LOCK_LINE)
273
274 /*
275 * Get a lock sleeping with specified interruptably and timeout.
276 */
277 #define BUF_TIMELOCK(bp, locktype, interlock, wmesg, catch, timo) \
278 _lockmgr_args(&(bp)->b_lock, (locktype) | LK_TIMELOCK, \
279 (interlock), (wmesg), (PRIBIO + 4) | (catch), (timo), \
280 LOCK_FILE, LOCK_LINE)
281
282 /*
283 * Release a lock. Only the acquiring process may free the lock unless
284 * it has been handed off to biodone.
285 */
286 #define BUF_UNLOCK(bp) do { \
287 KASSERT(((bp)->b_flags & B_REMFREE) == 0, \
288 ("BUF_UNLOCK %p while B_REMFREE is still set.", (bp))); \
289 \
290 (void)_lockmgr_args(&(bp)->b_lock, LK_RELEASE, NULL, \
291 LK_WMESG_DEFAULT, LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, \
292 LOCK_FILE, LOCK_LINE); \
293 } while (0)
294
295 /*
296 * Check if a buffer lock is recursed.
297 */
298 #define BUF_LOCKRECURSED(bp) \
299 lockmgr_recursed(&(bp)->b_lock)
300
301 /*
302 * Check if a buffer lock is currently held.
303 */
304 #define BUF_ISLOCKED(bp) \
305 lockstatus(&(bp)->b_lock)
306 /*
307 * Free a buffer lock.
308 */
309 #define BUF_LOCKFREE(bp) \
310 lockdestroy(&(bp)->b_lock)
311
312 /*
313 * Buffer lock assertions.
314 */
315 #if defined(INVARIANTS) && defined(INVARIANT_SUPPORT)
316 #define BUF_ASSERT_LOCKED(bp) \
317 _lockmgr_assert(&(bp)->b_lock, KA_LOCKED, LOCK_FILE, LOCK_LINE)
318 #define BUF_ASSERT_SLOCKED(bp) \
319 _lockmgr_assert(&(bp)->b_lock, KA_SLOCKED, LOCK_FILE, LOCK_LINE)
320 #define BUF_ASSERT_XLOCKED(bp) \
321 _lockmgr_assert(&(bp)->b_lock, KA_XLOCKED, LOCK_FILE, LOCK_LINE)
322 #define BUF_ASSERT_UNLOCKED(bp) \
323 _lockmgr_assert(&(bp)->b_lock, KA_UNLOCKED, LOCK_FILE, LOCK_LINE)
324 #define BUF_ASSERT_HELD(bp)
325 #define BUF_ASSERT_UNHELD(bp)
326 #else
327 #define BUF_ASSERT_LOCKED(bp)
328 #define BUF_ASSERT_SLOCKED(bp)
329 #define BUF_ASSERT_XLOCKED(bp)
330 #define BUF_ASSERT_UNLOCKED(bp)
331 #define BUF_ASSERT_HELD(bp)
332 #define BUF_ASSERT_UNHELD(bp)
333 #endif
334
335 #ifdef _SYS_PROC_H_ /* Avoid #include <sys/proc.h> pollution */
336 /*
337 * When initiating asynchronous I/O, change ownership of the lock to the
338 * kernel. Once done, the lock may legally released by biodone. The
339 * original owning process can no longer acquire it recursively, but must
340 * wait until the I/O is completed and the lock has been freed by biodone.
341 */
342 #define BUF_KERNPROC(bp) \
343 _lockmgr_disown(&(bp)->b_lock, LOCK_FILE, LOCK_LINE)
344 #endif
345
346 /*
347 * Find out if the lock has waiters or not.
348 */
349 #define BUF_LOCKWAITERS(bp) \
350 lockmgr_waiters(&(bp)->b_lock)
351
352 #endif /* _KERNEL */
353
354 struct buf_queue_head {
355 TAILQ_HEAD(buf_queue, buf) queue;
356 daddr_t last_pblkno;
357 struct buf *insert_point;
358 struct buf *switch_point;
359 };
360
361 /*
362 * This structure describes a clustered I/O. It is stored in the b_saveaddr
363 * field of the buffer on which I/O is done. At I/O completion, cluster
364 * callback uses the structure to parcel I/O's to individual buffers, and
365 * then free's this structure.
366 */
367 struct cluster_save {
368 long bs_bcount; /* Saved b_bcount. */
369 long bs_bufsize; /* Saved b_bufsize. */
370 void *bs_saveaddr; /* Saved b_addr. */
371 int bs_nchildren; /* Number of associated buffers. */
372 struct buf **bs_children; /* List of associated buffers. */
373 };
374
375 #ifdef _KERNEL
376
377 static __inline int
378 bwrite(struct buf *bp)
379 {
380
381 KASSERT(bp->b_bufobj != NULL, ("bwrite: no bufobj bp=%p", bp));
382 KASSERT(bp->b_bufobj->bo_ops != NULL, ("bwrite: no bo_ops bp=%p", bp));
383 KASSERT(bp->b_bufobj->bo_ops->bop_write != NULL,
384 ("bwrite: no bop_write bp=%p", bp));
385 return (BO_WRITE(bp->b_bufobj, bp));
386 }
387
388 static __inline void
389 bstrategy(struct buf *bp)
390 {
391
392 KASSERT(bp->b_bufobj != NULL, ("bstrategy: no bufobj bp=%p", bp));
393 KASSERT(bp->b_bufobj->bo_ops != NULL,
394 ("bstrategy: no bo_ops bp=%p", bp));
395 KASSERT(bp->b_bufobj->bo_ops->bop_strategy != NULL,
396 ("bstrategy: no bop_strategy bp=%p", bp));
397 BO_STRATEGY(bp->b_bufobj, bp);
398 }
399
400 static __inline void
401 buf_start(struct buf *bp)
402 {
403 if (bioops.io_start)
404 (*bioops.io_start)(bp);
405 }
406
407 static __inline void
408 buf_complete(struct buf *bp)
409 {
410 if (bioops.io_complete)
411 (*bioops.io_complete)(bp);
412 }
413
414 static __inline void
415 buf_deallocate(struct buf *bp)
416 {
417 if (bioops.io_deallocate)
418 (*bioops.io_deallocate)(bp);
419 BUF_LOCKFREE(bp);
420 }
421
422 static __inline int
423 buf_countdeps(struct buf *bp, int i)
424 {
425 if (bioops.io_countdeps)
426 return ((*bioops.io_countdeps)(bp, i));
427 else
428 return (0);
429 }
430
431 #endif /* _KERNEL */
432
433 /*
434 * Zero out the buffer's data area.
435 */
436 #define clrbuf(bp) { \
437 bzero((bp)->b_data, (u_int)(bp)->b_bcount); \
438 (bp)->b_resid = 0; \
439 }
440
441 /*
442 * Flags for getblk's last parameter.
443 */
444 #define GB_LOCK_NOWAIT 0x0001 /* Fail if we block on a buf lock. */
445 #define GB_NOCREAT 0x0002 /* Don't create a buf if not found. */
446
447 #ifdef _KERNEL
448 extern int nbuf; /* The number of buffer headers */
449 extern int maxswzone; /* Max KVA for swap structures */
450 extern int maxbcache; /* Max KVA for buffer cache */
451 extern int runningbufspace;
452 extern int hibufspace;
453 extern int dirtybufthresh;
454 extern int bdwriteskip;
455 extern int dirtybufferflushes;
456 extern int altbufferflushes;
457 extern int buf_maxio; /* nominal maximum I/O for buffer */
458 extern struct buf *buf; /* The buffer headers. */
459 extern char *buffers; /* The buffer contents. */
460 extern int bufpages; /* Number of memory pages in the buffer pool. */
461 extern struct buf *swbuf; /* Swap I/O buffer headers. */
462 extern int nswbuf; /* Number of swap I/O buffer headers. */
463 extern int cluster_pbuf_freecnt; /* Number of pbufs for clusters */
464 extern int vnode_pbuf_freecnt; /* Number of pbufs for vnode pager */
465
466 void runningbufwakeup(struct buf *);
467 void waitrunningbufspace(void);
468 caddr_t kern_vfs_bio_buffer_alloc(caddr_t v, long physmem_est);
469 void bufinit(void);
470 void bwillwrite(void);
471 int buf_dirty_count_severe(void);
472 void bremfree(struct buf *);
473 void bremfreef(struct buf *); /* XXX Force bremfree, only for nfs. */
474 int bread(struct vnode *, daddr_t, int, struct ucred *, struct buf **);
475 void breada(struct vnode *, daddr_t *, int *, int, struct ucred *);
476 int breadn(struct vnode *, daddr_t, int, daddr_t *, int *, int,
477 struct ucred *, struct buf **);
478 void bdwrite(struct buf *);
479 void bawrite(struct buf *);
480 void bdirty(struct buf *);
481 void bundirty(struct buf *);
482 void bufstrategy(struct bufobj *, struct buf *);
483 void brelse(struct buf *);
484 void bqrelse(struct buf *);
485 int vfs_bio_awrite(struct buf *);
486 struct buf * getpbuf(int *);
487 struct buf *incore(struct bufobj *, daddr_t);
488 struct buf *gbincore(struct bufobj *, daddr_t);
489 struct buf *getblk(struct vnode *, daddr_t, int, int, int, int);
490 struct buf *geteblk(int);
491 int bufwait(struct buf *);
492 int bufwrite(struct buf *);
493 void bufdone(struct buf *);
494 void bufdone_finish(struct buf *);
495
496 int cluster_read(struct vnode *, u_quad_t, daddr_t, long,
497 struct ucred *, long, int, struct buf **);
498 int cluster_wbuild(struct vnode *, long, daddr_t, int);
499 void cluster_write(struct vnode *, struct buf *, u_quad_t, int);
500 void vfs_bio_set_validclean(struct buf *, int base, int size);
501 void vfs_bio_clrbuf(struct buf *);
502 void vfs_busy_pages(struct buf *, int clear_modify);
503 void vfs_unbusy_pages(struct buf *);
504 int vmapbuf(struct buf *);
505 void vunmapbuf(struct buf *);
506 void relpbuf(struct buf *, int *);
507 void brelvp(struct buf *);
508 void bgetvp(struct vnode *, struct buf *);
509 void pbgetbo(struct bufobj *bo, struct buf *bp);
510 void pbgetvp(struct vnode *, struct buf *);
511 void pbrelbo(struct buf *);
512 void pbrelvp(struct buf *);
513 int allocbuf(struct buf *bp, int size);
514 void reassignbuf(struct buf *);
515 struct buf *trypbuf(int *);
516 void bwait(struct buf *, u_char, const char *);
517 void bdone(struct buf *);
518 void bpin(struct buf *);
519 void bunpin(struct buf *);
520 void bunpin_wait(struct buf *);
521
522 #endif /* _KERNEL */
523
524 #endif /* !_SYS_BUF_H_ */
525
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