sys/vm/vm_page.h

   1 /*
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * The Mach Operating System project at Carnegie-Mellon University.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  *      from: @(#)vm_page.h     8.2 (Berkeley) 12/13/93
  37  *
  38  *
  39  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
  40  * All rights reserved.
  41  *
  42  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
  43  *
  44  * Permission to use, copy, modify and distribute this software and
  45  * its documentation is hereby granted, provided that both the copyright
  46  * notice and this permission notice appear in all copies of the
  47  * software, derivative works or modified versions, and any portions
  48  * thereof, and that both notices appear in supporting documentation.
  49  *
  50  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  51  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
  52  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  53  *
  54  * Carnegie Mellon requests users of this software to return to
  55  *
  56  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  57  *  School of Computer Science
  58  *  Carnegie Mellon University
  59  *  Pittsburgh PA 15213-3890
  60  *
  61  * any improvements or extensions that they make and grant Carnegie the
  62  * rights to redistribute these changes.
  63  *
  64  * $FreeBSD: src/sys/vm/vm_page.h,v 1.75.2.8 2002/03/06 01:07:09 dillon Exp $
  65  */
  66
  67 /*
  68  *      Resident memory system definitions.
  69  */
  70
  71 #ifndef _VM_VM_PAGE_H_
  72 #define _VM_VM_PAGE_H_
  73
  74 #ifndef _SYS_TYPES_H_
  75 #include <sys/types.h>
  76 #endif
  77 #ifndef _SYS_TREE_H_
  78 #include <sys/tree.h>
  79 #endif
  80 #ifndef _MACHINE_PMAP_H_
  81 #include <machine/pmap.h>
  82 #endif
  83 #ifndef _VM_PMAP_H_
  84 #include <vm/pmap.h>
  85 #endif
  86 #include <machine/atomic.h>
  87
  88 #ifdef _KERNEL
  89
  90 #ifndef _SYS_SYSTM_H_
  91 #include <sys/systm.h>
  92 #endif
  93 #ifndef _SYS_THREAD2_H_
  94 #include <sys/thread2.h>
  95 #endif
  96
  97 #ifdef __x86_64__
  98 #include <machine/vmparam.h>
  99 #endif
 100
 101 #endif
 102
 103 typedef enum vm_page_event { VMEVENT_NONE, VMEVENT_COW } vm_page_event_t;
 104
 105 struct vm_page_action {
 106         LIST_ENTRY(vm_page_action) entry;
 107         struct vm_page          *m;
 108         vm_page_event_t         event;
 109         void                    (*func)(struct vm_page *,
 110                                         struct vm_page_action *);
 111         void                    *data;
 112 };
 113
 114 typedef struct vm_page_action *vm_page_action_t;
 115
 116 /*
 117  *      Management of resident (logical) pages.
 118  *
 119  *      A small structure is kept for each resident
 120  *      page, indexed by page number.  Each structure
 121  *      is an element of several lists:
 122  *
 123  *              A hash table bucket used to quickly
 124  *              perform object/offset lookups
 125  *
 126  *              A list of all pages for a given object,
 127  *              so they can be quickly deactivated at
 128  *              time of deallocation.
 129  *
 130  *              An ordered list of pages due for pageout.
 131  *
 132  *      In addition, the structure contains the object
 133  *      and offset to which this page belongs (for pageout),
 134  *      and sundry status bits.
 135  *
 136  *      Fields in this structure are locked either by the lock on the
 137  *      object that the page belongs to (O) or by the lock on the page
 138  *      queues (P).
 139  *
 140  *      The 'valid' and 'dirty' fields are distinct.  A page may have dirty
 141  *      bits set without having associated valid bits set.  This is used by
 142  *      NFS to implement piecemeal writes.
 143  */
 144
 145 TAILQ_HEAD(pglist, vm_page);
 146
 147 struct vm_object;
 148
 149 int rb_vm_page_compare(struct vm_page *, struct vm_page *);
 150
 151 struct vm_page_rb_tree;
 152 RB_PROTOTYPE2(vm_page_rb_tree, vm_page, rb_entry, rb_vm_page_compare, vm_pindex_t);
 153
 154 struct vm_page {
 155         TAILQ_ENTRY(vm_page) pageq;     /* vm_page_queues[] list (P)    */
 156         RB_ENTRY(vm_page) rb_entry;     /* Red-Black tree based at object */
 157
 158         struct vm_object *object;       /* which object am I in (O,P)*/
 159         vm_pindex_t pindex;             /* offset into object (O,P) */
 160         vm_paddr_t phys_addr;           /* physical address of page */
 161         struct md_page md;              /* machine dependant stuff */
 162         u_short queue;                  /* page queue index */
 163         u_short pc;                     /* page color */
 164         u_char  act_count;              /* page usage count */
 165         u_char  busy;                   /* page busy count */
 166         u_char  unused01;
 167         u_char  unused02;
 168         u_int32_t flags;                /* see below */
 169         u_int   wire_count;             /* wired down maps refs (P) */
 170         int     hold_count;             /* page hold count */
 171
 172         /*
 173          * NOTE that these must support one bit per DEV_BSIZE in a page!!!
 174          * so, on normal X86 kernels, they must be at least 8 bits wide.
 175          */
 176         u_char  valid;                  /* map of valid DEV_BSIZE chunks */
 177         u_char  dirty;                  /* map of dirty DEV_BSIZE chunks */
 178
 179         int     ku_pagecnt;             /* kmalloc helper */
 180 #ifdef VM_PAGE_DEBUG
 181         const char *busy_func;
 182         int     busy_line;
 183 #endif
 184 };
 185
 186 #ifdef VM_PAGE_DEBUG
 187 #define VM_PAGE_DEBUG_EXT(name) name ## _debug
 188 #define VM_PAGE_DEBUG_ARGS      , const char *func, int lineno
 189 #else
 190 #define VM_PAGE_DEBUG_EXT(name) name
 191 #define VM_PAGE_DEBUG_ARGS
 192 #endif
 193
 194 #ifndef __VM_PAGE_T_DEFINED__
 195 #define __VM_PAGE_T_DEFINED__
 196 typedef struct vm_page *vm_page_t;
 197 #endif
 198
 199 /*
 200  * Page coloring parameters.  We use generous parameters designed to
 201  * statistically spread pages over available cpu cache space.  This has
 202  * become less important over time as cache associativity is higher
 203  * in modern times but we still use the core algorithm to help reduce
 204  * lock contention between cpus.
 205  *
 206  * Page coloring cannot be disabled.
 207  */
 208
 209 #define PQ_PRIME1 31    /* Prime number somewhat less than PQ_HASH_SIZE */
 210 #define PQ_PRIME2 23    /* Prime number somewhat less than PQ_HASH_SIZE */
 211 #define PQ_L2_SIZE 256  /* A number of colors opt for 1M cache */
 212
 213 #if 0
 214 #define PQ_PRIME1 31    /* Prime number somewhat less than PQ_HASH_SIZE */
 215 #define PQ_PRIME2 23    /* Prime number somewhat less than PQ_HASH_SIZE */
 216 #define PQ_L2_SIZE 128  /* A number of colors opt for 512K cache */
 217
 218 #define PQ_PRIME1 13    /* Prime number somewhat less than PQ_HASH_SIZE */
 219 #define PQ_PRIME2 7     /* Prime number somewhat less than PQ_HASH_SIZE */
 220 #define PQ_L2_SIZE 64   /* A number of colors opt for 256K cache */
 221
 222 #define PQ_PRIME1 9     /* Produces a good PQ_L2_SIZE/3 + PQ_PRIME1 */
 223 #define PQ_PRIME2 5     /* Prime number somewhat less than PQ_HASH_SIZE */
 224 #define PQ_L2_SIZE 32   /* A number of colors opt for 128k cache */
 225
 226 #define PQ_PRIME1 5     /* Prime number somewhat less than PQ_HASH_SIZE */
 227 #define PQ_PRIME2 3     /* Prime number somewhat less than PQ_HASH_SIZE */
 228 #define PQ_L2_SIZE 16   /* A reasonable number of colors (opt for 64K cache) */
 229 #endif
 230
 231 #define PQ_L2_MASK      (PQ_L2_SIZE - 1)
 232
 233 #define PQ_NONE         0
 234 #define PQ_FREE         (1 + 0*PQ_L2_SIZE)
 235 #define PQ_INACTIVE     (1 + 1*PQ_L2_SIZE)
 236 #define PQ_ACTIVE       (1 + 2*PQ_L2_SIZE)
 237 #define PQ_CACHE        (1 + 3*PQ_L2_SIZE)
 238 #define PQ_HOLD         (1 + 4*PQ_L2_SIZE)
 239 #define PQ_COUNT        (1 + 5*PQ_L2_SIZE)
 240
 241 /*
 242  * Scan support
 243  */
 244 struct vm_map;
 245
 246 struct rb_vm_page_scan_info {
 247         vm_pindex_t     start_pindex;
 248         vm_pindex_t     end_pindex;
 249         int             limit;
 250         int             desired;
 251         int             error;
 252         int             pagerflags;
 253         vm_offset_t     addr;
 254         vm_pindex_t     backing_offset_index;
 255         struct vm_object *object;
 256         struct vm_object *backing_object;
 257         struct vm_page  *mpte;
 258         struct pmap     *pmap;
 259         struct vm_map   *map;
 260 };
 261
 262 int rb_vm_page_scancmp(struct vm_page *, void *);
 263
 264 struct vpgqueues {
 265         struct pglist pl;
 266         int     *cnt;
 267         int     lcnt;
 268         int     flipflop;       /* probably not the best place */
 269         struct spinlock spin;
 270         char    unused[64 - sizeof(struct pglist) -
 271                         sizeof(int *) - sizeof(int) * 2];
 272 };
 273
 274 extern struct vpgqueues vm_page_queues[PQ_COUNT];
 275
 276 /*
 277  * These are the flags defined for vm_page.
 278  *
 279  *  PG_UNMANAGED (used by OBJT_PHYS) indicates that the page is
 280  *  not under PV management but otherwise should be treated as a
 281  *  normal page.  Pages not under PV management cannot be paged out
 282  *  via the object/vm_page_t because there is no knowledge of their
 283  *  pte mappings, nor can they be removed from their objects via
 284  *  the object, and such pages are also not on any PQ queue.  The
 285  *  PG_MAPPED and PG_WRITEABLE flags are not applicable.
 286  *
 287  *  PG_MAPPED only applies to managed pages, indicating whether the page
 288  *  is mapped onto one or more pmaps.  A page might still be mapped to
 289  *  special pmaps in an unmanaged fashion, for example when mapped into a
 290  *  buffer cache buffer, without setting PG_MAPPED.
 291  *
 292  *  PG_WRITEABLE indicates that there may be a writeable managed pmap entry
 293  *  somewhere, and that the page can be dirtied by hardware at any time
 294  *  and may have to be tested for that.  The modified bit in unmanaged
 295  *  mappings or in the special clean map is not tested.
 296  *
 297  *  PG_SWAPPED indicates that the page is backed by a swap block.  Any
 298  *  VM object type other than OBJT_DEFAULT can have swap-backed pages now.
 299  *
 300  *  PG_SBUSY is set when m->busy != 0.  PG_SBUSY and m->busy are only modified
 301  *  when the page is PG_BUSY.
 302  */
 303 #define PG_BUSY         0x00000001      /* page is in transit (O) */
 304 #define PG_WANTED       0x00000002      /* someone is waiting for page (O) */
 305 #define PG_WINATCFLS    0x00000004      /* flush dirty page on inactive q */
 306 #define PG_FICTITIOUS   0x00000008      /* physical page doesn't exist (O) */
 307 #define PG_WRITEABLE    0x00000010      /* page is writeable */
 308 #define PG_MAPPED       0x00000020      /* page is mapped (managed) */
 309 #define PG_ZERO         0x00000040      /* page is zeroed */
 310 #define PG_REFERENCED   0x00000080      /* page has been referenced */
 311 #define PG_CLEANCHK     0x00000100      /* page will be checked for cleaning */
 312 #define PG_SWAPINPROG   0x00000200      /* swap I/O in progress on page      */
 313 #define PG_NOSYNC       0x00000400      /* do not collect for syncer */
 314 #define PG_UNMANAGED    0x00000800      /* No PV management for page */
 315 #define PG_MARKER       0x00001000      /* special queue marker page */
 316 #define PG_RAM          0x00002000      /* read ahead mark */
 317 #define PG_SWAPPED      0x00004000      /* backed by swap */
 318 #define PG_NOTMETA      0x00008000      /* do not back with swap */
 319 #define PG_ACTIONLIST   0x00010000      /* lookaside action list present */
 320 #define PG_SBUSY        0x00020000      /* soft-busy also set */
 321 #define PG_NEED_COMMIT  0x00040000      /* clean page requires commit */
 322
 323 /*
 324  * Misc constants.
 325  */
 326
 327 #define ACT_DECLINE             1
 328 #define ACT_ADVANCE             3
 329 #define ACT_INIT                5
 330 #define ACT_MAX                 64
 331
 332 #ifdef _KERNEL
 333 /*
 334  * Each pageable resident page falls into one of four lists:
 335  *
 336  *      free
 337  *              Available for allocation now.
 338  *
 339  * The following are all LRU sorted:
 340  *
 341  *      cache
 342  *              Almost available for allocation. Still in an
 343  *              object, but clean and immediately freeable at
 344  *              non-interrupt times.
 345  *
 346  *      inactive
 347  *              Low activity, candidates for reclamation.
 348  *              This is the list of pages that should be
 349  *              paged out next.
 350  *
 351  *      active
 352  *              Pages that are "active" i.e. they have been
 353  *              recently referenced.
 354  *
 355  *      zero
 356  *              Pages that are really free and have been pre-zeroed
 357  *
 358  */
 359
 360 extern int vm_page_zero_count;
 361 extern struct vm_page *vm_page_array;   /* First resident page in table */
 362 extern int vm_page_array_size;          /* number of vm_page_t's */
 363 extern long first_page;                 /* first physical page number */
 364
 365 #define VM_PAGE_TO_PHYS(entry)  \
 366                 ((entry)->phys_addr)
 367
 368 #define PHYS_TO_VM_PAGE(pa)     \
 369                 (&vm_page_array[atop(pa) - first_page])
 370
 371 /*
 372  *      Functions implemented as macros
 373  */
 374
 375 static __inline void
 376 vm_page_flag_set(vm_page_t m, unsigned int bits)
 377 {
 378         atomic_set_int(&(m)->flags, bits);
 379 }
 380
 381 static __inline void
 382 vm_page_flag_clear(vm_page_t m, unsigned int bits)
 383 {
 384         atomic_clear_int(&(m)->flags, bits);
 385 }
 386
 387 /*
 388  * Wakeup anyone waiting for the page after potentially unbusying
 389  * (hard or soft) or doing other work on a page that might make a
 390  * waiter ready.  The setting of PG_WANTED is integrated into the
 391  * related flags and it can't be set once the flags are already
 392  * clear, so there should be no races here.
 393  */
 394
 395 static __inline void
 396 vm_page_flash(vm_page_t m)
 397 {
 398         if (m->flags & PG_WANTED) {
 399                 vm_page_flag_clear(m, PG_WANTED);
 400                 wakeup(m);
 401         }
 402 }
 403
 404 #if PAGE_SIZE == 4096
 405 #define VM_PAGE_BITS_ALL 0xff
 406 #endif
 407
 408 /*
 409  * Note: the code will always use nominally free pages from the free list
 410  * before trying other flag-specified sources.
 411  *
 412  * At least one of VM_ALLOC_NORMAL|VM_ALLOC_SYSTEM|VM_ALLOC_INTERRUPT
 413  * must be specified.  VM_ALLOC_RETRY may only be specified if VM_ALLOC_NORMAL
 414  * is also specified.
 415  */
 416 #define VM_ALLOC_NORMAL         0x0001  /* ok to use cache pages */
 417 #define VM_ALLOC_SYSTEM         0x0002  /* ok to exhaust most of free list */
 418 #define VM_ALLOC_INTERRUPT      0x0004  /* ok to exhaust entire free list */
 419 #define VM_ALLOC_ZERO           0x0008  /* req pre-zero'd memory if avail */
 420 #define VM_ALLOC_QUICK          0x0010  /* like NORMAL but do not use cache */
 421 #define VM_ALLOC_FORCE_ZERO     0x0020  /* zero page even if already valid */
 422 #define VM_ALLOC_NULL_OK        0x0040  /* ok to return NULL on collision */
 423 #define VM_ALLOC_RETRY          0x0080  /* indefinite block (vm_page_grab()) */
 424 #define VM_ALLOC_USE_GD         0x0100  /* use per-gd cache */
 425
 426 void vm_page_queue_spin_lock(vm_page_t);
 427 void vm_page_queues_spin_lock(u_short);
 428 void vm_page_and_queue_spin_lock(vm_page_t);
 429
 430 void vm_page_queue_spin_unlock(vm_page_t);
 431 void vm_page_queues_spin_unlock(u_short);
 432 void vm_page_and_queue_spin_unlock(vm_page_t m);
 433
 434 void vm_page_io_finish(vm_page_t m);
 435 void vm_page_io_start(vm_page_t m);
 436 void vm_page_need_commit(vm_page_t m);
 437 void vm_page_clear_commit(vm_page_t m);
 438 void vm_page_wakeup(vm_page_t m);
 439 void vm_page_hold(vm_page_t);
 440 void vm_page_unhold(vm_page_t);
 441 void vm_page_activate (vm_page_t);
 442 void vm_page_pcpu_cache(void);
 443 vm_page_t vm_page_alloc (struct vm_object *, vm_pindex_t, int);
 444 vm_page_t vm_page_alloc_contig(vm_paddr_t low, vm_paddr_t high,
 445                      unsigned long alignment, unsigned long boundary,
 446                      unsigned long size);
 447 vm_page_t vm_page_grab (struct vm_object *, vm_pindex_t, int);
 448 void vm_page_cache (vm_page_t);
 449 int vm_page_try_to_cache (vm_page_t);
 450 int vm_page_try_to_free (vm_page_t);
 451 void vm_page_dontneed (vm_page_t);
 452 void vm_page_deactivate (vm_page_t);
 453 void vm_page_deactivate_locked (vm_page_t);
 454 int vm_page_insert (vm_page_t, struct vm_object *, vm_pindex_t);
 455 vm_page_t vm_page_lookup (struct vm_object *, vm_pindex_t);
 456 vm_page_t VM_PAGE_DEBUG_EXT(vm_page_lookup_busy_wait)(
 457                 struct vm_object *, vm_pindex_t, int, const char *
 458                 VM_PAGE_DEBUG_ARGS);
 459 vm_page_t VM_PAGE_DEBUG_EXT(vm_page_lookup_busy_try)(
 460                 struct vm_object *, vm_pindex_t, int, int *
 461                 VM_PAGE_DEBUG_ARGS);
 462 void vm_page_remove (vm_page_t);
 463 void vm_page_rename (vm_page_t, struct vm_object *, vm_pindex_t);
 464 void vm_page_startup (void);
 465 void vm_page_unmanage (vm_page_t);
 466 void vm_page_unwire (vm_page_t, int);
 467 void vm_page_wire (vm_page_t);
 468 void vm_page_unqueue (vm_page_t);
 469 void vm_page_unqueue_nowakeup (vm_page_t);
 470 vm_page_t vm_page_next (vm_page_t);
 471 void vm_page_set_validclean (vm_page_t, int, int);
 472 void vm_page_set_validdirty (vm_page_t, int, int);
 473 void vm_page_set_valid (vm_page_t, int, int);
 474 void vm_page_set_dirty (vm_page_t, int, int);
 475 void vm_page_clear_dirty (vm_page_t, int, int);
 476 void vm_page_set_invalid (vm_page_t, int, int);
 477 int vm_page_is_valid (vm_page_t, int, int);
 478 void vm_page_test_dirty (vm_page_t);
 479 int vm_page_bits (int, int);
 480 vm_page_t vm_page_list_find(int basequeue, int index, boolean_t prefer_zero);
 481 void vm_page_zero_invalid(vm_page_t m, boolean_t setvalid);
 482 void vm_page_free_toq(vm_page_t m);
 483 void vm_page_free_contig(vm_page_t m, unsigned long size);
 484 vm_page_t vm_page_free_fromq_fast(void);
 485 void vm_page_event_internal(vm_page_t, vm_page_event_t);
 486 void vm_page_dirty(vm_page_t m);
 487 void vm_page_register_action(vm_page_action_t action, vm_page_event_t event);
 488 void vm_page_unregister_action(vm_page_action_t action);
 489 void vm_page_sleep_busy(vm_page_t m, int also_m_busy, const char *msg);
 490 void VM_PAGE_DEBUG_EXT(vm_page_busy_wait)(vm_page_t m, int also_m_busy, const char *wmsg VM_PAGE_DEBUG_ARGS);
 491 int VM_PAGE_DEBUG_EXT(vm_page_busy_try)(vm_page_t m, int also_m_busy VM_PAGE_DEBUG_ARGS);
 492
 493 #ifdef VM_PAGE_DEBUG
 494
 495 #define vm_page_lookup_busy_wait(object, pindex, alsob, msg)            \
 496         vm_page_lookup_busy_wait_debug(object, pindex, alsob, msg,      \
 497                                         __func__, __LINE__)
 498
 499 #define vm_page_lookup_busy_try(object, pindex, alsob, errorp)          \
 500         vm_page_lookup_busy_try_debug(object, pindex, alsob, errorp,    \
 501                                         __func__, __LINE__)
 502
 503 #define vm_page_busy_wait(m, alsob, msg)                                \
 504         vm_page_busy_wait_debug(m, alsob, msg, __func__, __LINE__)
 505
 506 #define vm_page_busy_try(m, alsob)                                      \
 507         vm_page_busy_try_debug(m, alsob, __func__, __LINE__)
 508
 509 #endif
 510
 511 /*
 512  * Reduce the protection of a page.  This routine never raises the
 513  * protection and therefore can be safely called if the page is already
 514  * at VM_PROT_NONE (it will be a NOP effectively ).
 515  *
 516  * VM_PROT_NONE will remove all user mappings of a page.  This is often
 517  * necessary when a page changes state (for example, turns into a copy-on-write
 518  * page or needs to be frozen for write I/O) in order to force a fault, or
 519  * to force a page's dirty bits to be synchronized and avoid hardware
 520  * (modified/accessed) bit update races with pmap changes.
 521  *
 522  * Since 'prot' is usually a constant, this inline usually winds up optimizing
 523  * out the primary conditional.
 524  *
 525  * WARNING: VM_PROT_NONE can block, but will loop until all mappings have
 526  * been cleared.  Callers should be aware that other page related elements
 527  * might have changed, however.
 528  */
 529 static __inline void
 530 vm_page_protect(vm_page_t m, int prot)
 531 {
 532         KKASSERT(m->flags & PG_BUSY);
 533         if (prot == VM_PROT_NONE) {
 534                 if (m->flags & (PG_WRITEABLE|PG_MAPPED)) {
 535                         pmap_page_protect(m, VM_PROT_NONE);
 536                         /* PG_WRITEABLE & PG_MAPPED cleared by call */
 537                 }
 538         } else if ((prot == VM_PROT_READ) && (m->flags & PG_WRITEABLE)) {
 539                 pmap_page_protect(m, VM_PROT_READ);
 540                 /* PG_WRITEABLE cleared by call */
 541         }
 542 }
 543
 544 /*
 545  * Zero-fill the specified page.  The entire contents of the page will be
 546  * zero'd out.
 547  */
 548 static __inline boolean_t
 549 vm_page_zero_fill(vm_page_t m)
 550 {
 551         pmap_zero_page(VM_PAGE_TO_PHYS(m));
 552         return (TRUE);
 553 }
 554
 555 /*
 556  * Copy the contents of src_m to dest_m.  The pages must be stable but spl
 557  * and other protections depend on context.
 558  */
 559 static __inline void
 560 vm_page_copy(vm_page_t src_m, vm_page_t dest_m)
 561 {
 562         pmap_copy_page(VM_PAGE_TO_PHYS(src_m), VM_PAGE_TO_PHYS(dest_m));
 563         dest_m->valid = VM_PAGE_BITS_ALL;
 564         dest_m->dirty = VM_PAGE_BITS_ALL;
 565 }
 566
 567 /*
 568  * Free a page.  The page must be marked BUSY.
 569  *
 570  * Always clear PG_ZERO when freeing a page, which ensures the flag is not
 571  * set unless we are absolutely certain the page is zerod.  This is
 572  * particularly important when the vm_page_alloc*() code moves pages from
 573  * PQ_CACHE to PQ_FREE.
 574  */
 575 static __inline void
 576 vm_page_free(vm_page_t m)
 577 {
 578         vm_page_flag_clear(m, PG_ZERO);
 579         vm_page_free_toq(m);
 580 }
 581
 582 /*
 583  * Free a page to the zerod-pages queue.  The caller must ensure that the
 584  * page has been zerod.
 585  */
 586 static __inline void
 587 vm_page_free_zero(vm_page_t m)
 588 {
 589 #ifdef PMAP_DEBUG
 590 #ifdef PHYS_TO_DMAP
 591         char *p = (char *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));
 592         int i;
 593
 594         for (i = 0; i < PAGE_SIZE; i++) {
 595                 if (p[i] != 0) {
 596                         panic("non-zero page in vm_page_free_zero()");
 597                 }
 598         }
 599 #endif
 600 #endif
 601         vm_page_flag_set(m, PG_ZERO);
 602         vm_page_free_toq(m);
 603 }
 604
 605 /*
 606  * Set page to not be dirty.  Note: does not clear pmap modify bits .
 607  */
 608 static __inline void
 609 vm_page_undirty(vm_page_t m)
 610 {
 611         m->dirty = 0;
 612 }
 613
 614 #endif                          /* _KERNEL */
 615 #endif                          /* !_VM_VM_PAGE_H_ */