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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 $
40 * $DragonFly: src/sys/sys/buf.h,v 1.11 2004/07/17 01:45:37 hmp Exp $
47 #include <sys/queue.h>
52 #ifndef _SYS_DEVICE_H_
53 #include <sys/device.h>
66 * To avoid including <ufs/ffs/softdep.h>
68 LIST_HEAD(workhead, worklist);
70 * These are currently used only by the soft dependency code, hence
71 * are stored once in a global variable. If other subsystems wanted
72 * to use these hooks, a pointer to a set of bio_ops could be added
75 extern struct bio_ops {
76 void (*io_start) (struct buf *);
77 void (*io_complete) (struct buf *);
78 void (*io_deallocate) (struct buf *);
79 int (*io_fsync) (struct vnode *);
80 int (*io_sync) (struct mount *);
81 void (*io_movedeps) (struct buf *, struct buf *);
82 int (*io_countdeps) (struct buf *, int);
87 void (*ic_prev_iodone) (struct buf *);
88 void *ic_prev_iodone_chain;
96 * The buffer header describes an I/O operation in the kernel.
99 * b_bufsize, b_bcount. b_bufsize is the allocation size of the
100 * buffer, either DEV_BSIZE or PAGE_SIZE aligned. b_bcount is the
101 * originally requested buffer size and can serve as a bounds check
102 * against EOF. For most, but not all uses, b_bcount == b_bufsize.
104 * b_dirtyoff, b_dirtyend. Buffers support piecemeal, unaligned
105 * ranges of dirty data that need to be written to backing store.
106 * The range is typically clipped at b_bcount ( not b_bufsize ).
108 * b_resid. Number of bytes remaining in I/O. After an I/O operation
109 * completes, b_resid is usually 0 indicating 100% success.
112 LIST_ENTRY(buf) b_hash; /* Hash chain. */
113 TAILQ_ENTRY(buf) b_vnbufs; /* Buffer's associated vnode. */
114 TAILQ_ENTRY(buf) b_freelist; /* Free list position if not active. */
115 TAILQ_ENTRY(buf) b_act; /* Device driver queue when active. *new* */
116 long b_flags; /* B_* flags. */
117 unsigned short b_qindex; /* buffer queue index */
118 unsigned char b_xflags; /* extra flags */
119 struct lock b_lock; /* Buffer lock */
120 int b_error; /* Errno value. */
121 long b_bufsize; /* Allocated buffer size. */
122 long b_runningbufspace; /* when I/O is running, pipelining */
123 long b_bcount; /* Valid bytes in buffer. */
124 long b_resid; /* Remaining I/O. */
125 dev_t b_dev; /* Device associated with buffer. */
126 caddr_t b_data; /* Memory, superblocks, indirect etc. */
127 caddr_t b_kvabase; /* base kva for buffer */
128 int b_kvasize; /* size of kva for buffer */
129 daddr_t b_lblkno; /* Logical block number. */
130 daddr_t b_blkno; /* Underlying physical block number. */
131 off_t b_offset; /* Offset into file */
132 /* Function to call upon completion. */
133 void (*b_iodone) (struct buf *);
134 /* For nested b_iodone's. */
135 struct iodone_chain *b_iodone_chain;
136 struct vnode *b_vp; /* Device vnode. */
137 int b_dirtyoff; /* Offset in buffer of dirty region. */
138 int b_dirtyend; /* Offset of end of dirty region. */
139 daddr_t b_pblkno; /* physical block number */
140 void *b_saveaddr; /* Original b_addr for physio. */
141 void *b_driver1; /* for private use by the driver */
142 void *b_caller1; /* for private use by the caller */
148 TAILQ_HEAD(cluster_list_head, buf) cluster_head;
149 TAILQ_ENTRY(buf) cluster_entry;
151 struct xio b_xio; /* page list management for buffer head. */
152 struct workhead b_dep; /* List of filesystem dependencies. */
153 struct chain_info { /* buffer chaining */
159 #define b_spc b_pager.pg_spc
162 * These flags are kept in b_flags.
166 * B_ASYNC VOP calls on bp's are usually async whether or not
167 * B_ASYNC is set, but some subsystems, such as NFS, like
168 * to know what is best for the caller so they can
171 * B_PAGING Indicates that bp is being used by the paging system or
172 * some paging system and that the bp is not linked into
173 * the b_vp's clean/dirty linked lists or ref counts.
174 * Buffer vp reassignments are illegal in this case.
176 * B_CACHE This may only be set if the buffer is entirely valid.
177 * The situation where B_DELWRI is set and B_CACHE is
178 * clear MUST be committed to disk by getblk() so
179 * B_DELWRI can also be cleared. See the comments for
180 * getblk() in kern/vfs_bio.c. If B_CACHE is clear,
181 * the caller is expected to clear B_ERROR|B_INVAL,
182 * set B_READ, and initiate an I/O.
184 * The 'entire buffer' is defined to be the range from
185 * 0 through b_bcount.
187 * B_MALLOC Request that the buffer be allocated from the malloc
188 * pool, DEV_BSIZE aligned instead of PAGE_SIZE aligned.
190 * B_CLUSTEROK This flag is typically set for B_DELWRI buffers
191 * by filesystems that allow clustering when the buffer
192 * is fully dirty and indicates that it may be clustered
193 * with other adjacent dirty buffers. Note the clustering
194 * may not be used with the stage 1 data write under NFS
195 * but may be used for the commit rpc portion.
197 * B_VMIO Indicates that the buffer is tied into an VM object.
198 * The buffer's data is always PAGE_SIZE aligned even
199 * if b_bufsize and b_bcount are not. ( b_bufsize is
200 * always at least DEV_BSIZE aligned, though ).
202 * B_DIRECT Hint that we should attempt to completely free
203 * the pages underlying the buffer. B_DIRECT is
204 * sticky until the buffer is released and typically
205 * only has an effect when B_RELBUF is also set.
207 * B_NOWDRAIN This flag should be set when a device (like VN)
208 * does a turn-around VOP_WRITE from its strategy
209 * routine. This flag prevents bwrite() from blocking
210 * in wdrain, avoiding a deadlock situation.
213 #define B_AGE 0x00000001 /* Move to age queue when I/O done. */
214 #define B_NEEDCOMMIT 0x00000002 /* Append-write in progress. */
215 #define B_ASYNC 0x00000004 /* Start I/O, do not wait. */
216 #define B_DIRECT 0x00000008 /* direct I/O flag (pls free vmio) */
217 #define B_DEFERRED 0x00000010 /* Skipped over for cleaning */
218 #define B_CACHE 0x00000020 /* Bread found us in the cache. */
219 #define B_CALL 0x00000040 /* Call b_iodone from biodone. */
220 #define B_DELWRI 0x00000080 /* Delay I/O until buffer reused. */
221 #define B_FREEBUF 0x00000100 /* Instruct driver: free blocks */
222 #define B_DONE 0x00000200 /* I/O completed. */
223 #define B_EINTR 0x00000400 /* I/O was interrupted */
224 #define B_ERROR 0x00000800 /* I/O error occurred. */
225 #define B_SCANNED 0x00001000 /* VOP_FSYNC funcs mark written bufs */
226 #define B_INVAL 0x00002000 /* Does not contain valid info. */
227 #define B_LOCKED 0x00004000 /* Locked in core (not reusable). */
228 #define B_NOCACHE 0x00008000 /* Do not cache block after use. */
229 #define B_MALLOC 0x00010000 /* malloced b_data */
230 #define B_CLUSTEROK 0x00020000 /* Pagein op, so swap() can count it. */
231 #define B_PHYS 0x00040000 /* I/O to user memory. */
232 #define B_RAW 0x00080000 /* Set by physio for raw transfers. */
233 #define B_READ 0x00100000 /* Read buffer. */
234 #define B_DIRTY 0x00200000 /* Needs writing later. */
235 #define B_RELBUF 0x00400000 /* Release VMIO buffer. */
236 #define B_WANT 0x00800000 /* Used by vm_pager.c */
237 #define B_WRITE 0x00000000 /* Write buffer (pseudo flag). */
238 #define B_WRITEINPROG 0x01000000 /* Write in progress. */
239 #define B_XXX 0x02000000 /* Debugging flag. */
240 #define B_PAGING 0x04000000 /* volatile paging I/O -- bypass VMIO */
241 #define B_ORDERED 0x08000000 /* Must guarantee I/O ordering */
242 #define B_RAM 0x10000000 /* Read ahead mark (flag) */
243 #define B_VMIO 0x20000000 /* VMIO flag */
244 #define B_CLUSTER 0x40000000 /* pagein op, so swap() can count it */
245 #define B_NOWDRAIN 0x80000000 /* Avoid wdrain deadlock */
247 #define PRINT_BUF_FLAGS "\20\40nowdrain\37cluster\36vmio\35ram\34ordered" \
248 "\33paging\32xxx\31writeinprog\30want\27relbuf\26dirty" \
249 "\25read\24raw\23phys\22clusterok\21malloc\20nocache" \
250 "\17locked\16inval\15scanned\14error\13eintr\12done\11freebuf" \
251 "\10delwri\7call\6cache\4direct\3async\2needcommit\1age"
254 * These flags are kept in b_xflags.
256 #define BX_VNDIRTY 0x00000001 /* On vnode dirty list */
257 #define BX_VNCLEAN 0x00000002 /* On vnode clean list */
258 #define BX_BKGRDWRITE 0x00000004 /* Do writes in background */
259 #define BX_BKGRDINPROG 0x00000008 /* Background write in progress */
260 #define BX_BKGRDWAIT 0x00000010 /* Background write waiting */
261 #define BX_AUTOCHAINDONE 0x00000020 /* pager I/O chain auto mode */
263 #define NOOFFSET (-1LL) /* No buffer offset calculated yet */
267 * Buffer locking. See sys/buf2.h for inline functions.
269 extern struct lwkt_token buftimetoken; /* Interlock on setting prio and timo */
270 extern char *buf_wmesg; /* Default buffer lock message */
271 #define BUF_WMESG "bufwait"
275 struct buf_queue_head {
276 TAILQ_HEAD(buf_queue, buf) queue;
278 struct buf *insert_point;
279 struct buf *switch_point;
283 * This structure describes a clustered I/O. It is stored in the b_saveaddr
284 * field of the buffer on which I/O is done. At I/O completion, cluster
285 * callback uses the structure to parcel I/O's to individual buffers, and
286 * then free's this structure.
288 struct cluster_save {
289 long bs_bcount; /* Saved b_bcount. */
290 long bs_bufsize; /* Saved b_bufsize. */
291 void *bs_saveaddr; /* Saved b_addr. */
292 int bs_nchildren; /* Number of associated buffers. */
293 struct buf **bs_children; /* List of associated buffers. */
297 * Definitions for the buffer free lists.
299 #define BUFFER_QUEUES 6 /* number of free buffer queues */
301 #define QUEUE_NONE 0 /* on no queue */
302 #define QUEUE_LOCKED 1 /* locked buffers */
303 #define QUEUE_CLEAN 2 /* non-B_DELWRI buffers */
304 #define QUEUE_DIRTY 3 /* B_DELWRI buffers */
305 #define QUEUE_EMPTYKVA 4 /* empty buffer headers w/KVA assignment */
306 #define QUEUE_EMPTY 5 /* empty buffer headers */
309 * Zero out the buffer's data area.
311 #define clrbuf(bp) { \
312 bzero((bp)->b_data, (u_int)(bp)->b_bcount); \
317 * Flags to low-level bitmap allocation routines (balloc).
319 * Note: sequential_heuristic() in kern/vfs_vnops.c limits the count
322 #define B_SEQMASK 0x7F000000 /* Sequential heuristic mask. */
323 #define B_SEQSHIFT 24 /* Sequential heuristic shift. */
324 #define B_SEQMAX 0x7F
325 #define B_CLRBUF 0x01 /* Cleared invalid areas of buffer. */
326 #define B_SYNC 0x02 /* Do all allocations synchronously. */
329 extern int nbuf; /* The number of buffer headers */
330 extern int maxswzone; /* Max KVA for swap structures */
331 extern int maxbcache; /* Max KVA for buffer cache */
332 extern int runningbufspace;
333 extern int buf_maxio; /* nominal maximum I/O for buffer */
334 extern struct buf *buf; /* The buffer headers. */
335 extern char *buffers; /* The buffer contents. */
336 extern int bufpages; /* Number of memory pages in the buffer pool. */
337 extern struct buf *swbuf; /* Swap I/O buffer headers. */
338 extern int nswbuf; /* Number of swap I/O buffer headers. */
339 extern TAILQ_HEAD(swqueue, buf) bswlist;
340 extern TAILQ_HEAD(bqueues, buf) bufqueues[BUFFER_QUEUES];
344 caddr_t bufhashinit (caddr_t);
346 void bwillwrite (void);
347 int buf_dirty_count_severe (void);
348 void bremfree (struct buf *);
349 int bread (struct vnode *, daddr_t, int, struct buf **);
350 int breadn (struct vnode *, daddr_t, int, daddr_t *, int *, int,
352 int bwrite (struct buf *);
353 void bdwrite (struct buf *);
354 void bawrite (struct buf *);
355 void bdirty (struct buf *);
356 void bundirty (struct buf *);
357 int bowrite (struct buf *);
358 void brelse (struct buf *);
359 void bqrelse (struct buf *);
360 int vfs_bio_awrite (struct buf *);
361 struct buf * getpbuf (int *);
362 struct buf *incore (struct vnode *, daddr_t);
363 struct buf *gbincore (struct vnode *, daddr_t);
364 int inmem (struct vnode *, daddr_t);
365 struct buf *getblk (struct vnode *, daddr_t, int, int, int);
366 struct buf *geteblk (int);
367 int biowait (struct buf *);
368 void biodone (struct buf *);
370 void cluster_callback (struct buf *);
371 int cluster_read (struct vnode *, u_quad_t, daddr_t, long,
372 long, int, struct buf **);
373 int cluster_wbuild (struct vnode *, long, daddr_t, int);
374 void cluster_write (struct buf *, u_quad_t, int);
375 int physio (dev_t dev, struct uio *uio, int ioflag);
376 #define physread physio
377 #define physwrite physio
378 void vfs_bio_set_validclean (struct buf *, int base, int size);
379 void vfs_bio_clrbuf (struct buf *);
380 void vfs_busy_pages (struct buf *, int clear_modify);
381 void vfs_unbusy_pages (struct buf *);
382 void vwakeup (struct buf *);
383 int vmapbuf (struct buf *);
384 void vunmapbuf (struct buf *);
385 void relpbuf (struct buf *, int *);
386 void brelvp (struct buf *);
387 void bgetvp (struct vnode *, struct buf *);
388 void pbgetvp (struct vnode *, struct buf *);
389 void pbrelvp (struct buf *);
390 int allocbuf (struct buf *bp, int size);
391 void reassignbuf (struct buf *, struct vnode *);
392 void pbreassignbuf (struct buf *, struct vnode *);
393 struct buf *trypbuf (int *);
397 #endif /* !_SYS_BUF_H_ */