FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_pager.c
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 * 4. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * from: @(#)vm_pager.c 8.6 (Berkeley) 1/12/94
33 *
34 *
35 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
36 * All rights reserved.
37 *
38 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
39 *
40 * Permission to use, copy, modify and distribute this software and
41 * its documentation is hereby granted, provided that both the copyright
42 * notice and this permission notice appear in all copies of the
43 * software, derivative works or modified versions, and any portions
44 * thereof, and that both notices appear in supporting documentation.
45 *
46 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
47 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
48 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
49 *
50 * Carnegie Mellon requests users of this software to return to
51 *
52 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
53 * School of Computer Science
54 * Carnegie Mellon University
55 * Pittsburgh PA 15213-3890
56 *
57 * any improvements or extensions that they make and grant Carnegie the
58 * rights to redistribute these changes.
59 */
60
61 /*
62 * Paging space routine stubs. Emulates a matchmaker-like interface
63 * for builtin pagers.
64 */
65
66 #include <sys/cdefs.h>
67 __FBSDID("$FreeBSD: releng/8.4/sys/vm/vm_pager.c 236485 2012-06-02 19:21:34Z avg $");
68
69 #include <sys/param.h>
70 #include <sys/systm.h>
71 #include <sys/kernel.h>
72 #include <sys/vnode.h>
73 #include <sys/bio.h>
74 #include <sys/buf.h>
75 #include <sys/ucred.h>
76 #include <sys/malloc.h>
77
78 #include <vm/vm.h>
79 #include <vm/vm_param.h>
80 #include <vm/vm_object.h>
81 #include <vm/vm_page.h>
82 #include <vm/vm_pager.h>
83 #include <vm/vm_extern.h>
84
85 MALLOC_DEFINE(M_VMPGDATA, "vm_pgdata", "XXX: VM pager private data");
86
87 int cluster_pbuf_freecnt = -1; /* unlimited to begin with */
88
89 static int dead_pager_getpages(vm_object_t, vm_page_t *, int, int);
90 static vm_object_t dead_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
91 vm_ooffset_t, struct ucred *);
92 static void dead_pager_putpages(vm_object_t, vm_page_t *, int, int, int *);
93 static boolean_t dead_pager_haspage(vm_object_t, vm_pindex_t, int *, int *);
94 static void dead_pager_dealloc(vm_object_t);
95
96 static int
97 dead_pager_getpages(obj, ma, count, req)
98 vm_object_t obj;
99 vm_page_t *ma;
100 int count;
101 int req;
102 {
103 return VM_PAGER_FAIL;
104 }
105
106 static vm_object_t
107 dead_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
108 vm_ooffset_t off, struct ucred *cred)
109 {
110 return NULL;
111 }
112
113 static void
114 dead_pager_putpages(object, m, count, flags, rtvals)
115 vm_object_t object;
116 vm_page_t *m;
117 int count;
118 int flags;
119 int *rtvals;
120 {
121 int i;
122
123 for (i = 0; i < count; i++) {
124 rtvals[i] = VM_PAGER_AGAIN;
125 }
126 }
127
128 static int
129 dead_pager_haspage(object, pindex, prev, next)
130 vm_object_t object;
131 vm_pindex_t pindex;
132 int *prev;
133 int *next;
134 {
135 if (prev)
136 *prev = 0;
137 if (next)
138 *next = 0;
139 return FALSE;
140 }
141
142 static void
143 dead_pager_dealloc(object)
144 vm_object_t object;
145 {
146 return;
147 }
148
149 static struct pagerops deadpagerops = {
150 .pgo_alloc = dead_pager_alloc,
151 .pgo_dealloc = dead_pager_dealloc,
152 .pgo_getpages = dead_pager_getpages,
153 .pgo_putpages = dead_pager_putpages,
154 .pgo_haspage = dead_pager_haspage,
155 };
156
157 struct pagerops *pagertab[] = {
158 &defaultpagerops, /* OBJT_DEFAULT */
159 &swappagerops, /* OBJT_SWAP */
160 &vnodepagerops, /* OBJT_VNODE */
161 &devicepagerops, /* OBJT_DEVICE */
162 &physpagerops, /* OBJT_PHYS */
163 &deadpagerops, /* OBJT_DEAD */
164 &sgpagerops /* OBJT_SG */
165 };
166
167 static const int npagers = sizeof(pagertab) / sizeof(pagertab[0]);
168
169 /*
170 * Kernel address space for mapping pages.
171 * Used by pagers where KVAs are needed for IO.
172 *
173 * XXX needs to be large enough to support the number of pending async
174 * cleaning requests (NPENDINGIO == 64) * the maximum swap cluster size
175 * (MAXPHYS == 64k) if you want to get the most efficiency.
176 */
177 vm_map_t pager_map;
178 static int bswneeded;
179 static vm_offset_t swapbkva; /* swap buffers kva */
180 struct mtx pbuf_mtx;
181 static TAILQ_HEAD(swqueue, buf) bswlist;
182
183 void
184 vm_pager_init()
185 {
186 struct pagerops **pgops;
187
188 TAILQ_INIT(&bswlist);
189 /*
190 * Initialize known pagers
191 */
192 for (pgops = pagertab; pgops < &pagertab[npagers]; pgops++)
193 if ((*pgops)->pgo_init != NULL)
194 (*(*pgops)->pgo_init) ();
195 }
196
197 void
198 vm_pager_bufferinit()
199 {
200 struct buf *bp;
201 int i;
202
203 mtx_init(&pbuf_mtx, "pbuf mutex", NULL, MTX_DEF);
204 bp = swbuf;
205 /*
206 * Now set up swap and physical I/O buffer headers.
207 */
208 for (i = 0; i < nswbuf; i++, bp++) {
209 TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
210 BUF_LOCKINIT(bp);
211 LIST_INIT(&bp->b_dep);
212 bp->b_rcred = bp->b_wcred = NOCRED;
213 bp->b_xflags = 0;
214 }
215
216 cluster_pbuf_freecnt = nswbuf / 2;
217 vnode_pbuf_freecnt = nswbuf / 2 + 1;
218
219 swapbkva = kmem_alloc_nofault(pager_map, nswbuf * MAXPHYS);
220 if (!swapbkva)
221 panic("Not enough pager_map VM space for physical buffers");
222 }
223
224 /*
225 * Allocate an instance of a pager of the given type.
226 * Size, protection and offset parameters are passed in for pagers that
227 * need to perform page-level validation (e.g. the device pager).
228 */
229 vm_object_t
230 vm_pager_allocate(objtype_t type, void *handle, vm_ooffset_t size,
231 vm_prot_t prot, vm_ooffset_t off, struct ucred *cred)
232 {
233 vm_object_t ret;
234 struct pagerops *ops;
235
236 ops = pagertab[type];
237 if (ops)
238 ret = (*ops->pgo_alloc) (handle, size, prot, off, cred);
239 else
240 ret = NULL;
241 return (ret);
242 }
243
244 /*
245 * The object must be locked.
246 */
247 void
248 vm_pager_deallocate(object)
249 vm_object_t object;
250 {
251
252 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
253 (*pagertab[object->type]->pgo_dealloc) (object);
254 }
255
256 /*
257 * vm_pager_get_pages() - inline, see vm/vm_pager.h
258 * vm_pager_put_pages() - inline, see vm/vm_pager.h
259 * vm_pager_has_page() - inline, see vm/vm_pager.h
260 */
261
262 /*
263 * Search the specified pager object list for an object with the
264 * specified handle. If an object with the specified handle is found,
265 * increase its reference count and return it. Otherwise, return NULL.
266 *
267 * The pager object list must be locked.
268 */
269 vm_object_t
270 vm_pager_object_lookup(struct pagerlst *pg_list, void *handle)
271 {
272 vm_object_t object;
273
274 TAILQ_FOREACH(object, pg_list, pager_object_list) {
275 if (object->handle == handle) {
276 VM_OBJECT_LOCK(object);
277 if ((object->flags & OBJ_DEAD) == 0) {
278 vm_object_reference_locked(object);
279 VM_OBJECT_UNLOCK(object);
280 break;
281 }
282 VM_OBJECT_UNLOCK(object);
283 }
284 }
285 return (object);
286 }
287
288 /*
289 * initialize a physical buffer
290 */
291
292 /*
293 * XXX This probably belongs in vfs_bio.c
294 */
295 static void
296 initpbuf(struct buf *bp)
297 {
298 KASSERT(bp->b_bufobj == NULL, ("initpbuf with bufobj"));
299 KASSERT(bp->b_vp == NULL, ("initpbuf with vp"));
300 bp->b_rcred = NOCRED;
301 bp->b_wcred = NOCRED;
302 bp->b_qindex = 0; /* On no queue (QUEUE_NONE) */
303 bp->b_saveaddr = (caddr_t) (MAXPHYS * (bp - swbuf)) + swapbkva;
304 bp->b_data = bp->b_saveaddr;
305 bp->b_kvabase = bp->b_saveaddr;
306 bp->b_kvasize = MAXPHYS;
307 bp->b_xflags = 0;
308 bp->b_flags = 0;
309 bp->b_ioflags = 0;
310 bp->b_iodone = NULL;
311 bp->b_error = 0;
312 BUF_LOCK(bp, LK_EXCLUSIVE, NULL);
313 }
314
315 /*
316 * allocate a physical buffer
317 *
318 * There are a limited number (nswbuf) of physical buffers. We need
319 * to make sure that no single subsystem is able to hog all of them,
320 * so each subsystem implements a counter which is typically initialized
321 * to 1/2 nswbuf. getpbuf() decrements this counter in allocation and
322 * increments it on release, and blocks if the counter hits zero. A
323 * subsystem may initialize the counter to -1 to disable the feature,
324 * but it must still be sure to match up all uses of getpbuf() with
325 * relpbuf() using the same variable.
326 *
327 * NOTE: pfreecnt can be NULL, but this 'feature' will be removed
328 * relatively soon when the rest of the subsystems get smart about it. XXX
329 */
330 struct buf *
331 getpbuf(int *pfreecnt)
332 {
333 struct buf *bp;
334
335 mtx_lock(&pbuf_mtx);
336
337 for (;;) {
338 if (pfreecnt) {
339 while (*pfreecnt == 0) {
340 msleep(pfreecnt, &pbuf_mtx, PVM, "wswbuf0", 0);
341 }
342 }
343
344 /* get a bp from the swap buffer header pool */
345 if ((bp = TAILQ_FIRST(&bswlist)) != NULL)
346 break;
347
348 bswneeded = 1;
349 msleep(&bswneeded, &pbuf_mtx, PVM, "wswbuf1", 0);
350 /* loop in case someone else grabbed one */
351 }
352 TAILQ_REMOVE(&bswlist, bp, b_freelist);
353 if (pfreecnt)
354 --*pfreecnt;
355 mtx_unlock(&pbuf_mtx);
356
357 initpbuf(bp);
358 return bp;
359 }
360
361 /*
362 * allocate a physical buffer, if one is available.
363 *
364 * Note that there is no NULL hack here - all subsystems using this
365 * call understand how to use pfreecnt.
366 */
367 struct buf *
368 trypbuf(int *pfreecnt)
369 {
370 struct buf *bp;
371
372 mtx_lock(&pbuf_mtx);
373 if (*pfreecnt == 0 || (bp = TAILQ_FIRST(&bswlist)) == NULL) {
374 mtx_unlock(&pbuf_mtx);
375 return NULL;
376 }
377 TAILQ_REMOVE(&bswlist, bp, b_freelist);
378
379 --*pfreecnt;
380
381 mtx_unlock(&pbuf_mtx);
382
383 initpbuf(bp);
384
385 return bp;
386 }
387
388 /*
389 * release a physical buffer
390 *
391 * NOTE: pfreecnt can be NULL, but this 'feature' will be removed
392 * relatively soon when the rest of the subsystems get smart about it. XXX
393 */
394 void
395 relpbuf(struct buf *bp, int *pfreecnt)
396 {
397
398 if (bp->b_rcred != NOCRED) {
399 crfree(bp->b_rcred);
400 bp->b_rcred = NOCRED;
401 }
402 if (bp->b_wcred != NOCRED) {
403 crfree(bp->b_wcred);
404 bp->b_wcred = NOCRED;
405 }
406
407 KASSERT(bp->b_vp == NULL, ("relpbuf with vp"));
408 KASSERT(bp->b_bufobj == NULL, ("relpbuf with bufobj"));
409
410 BUF_UNLOCK(bp);
411
412 mtx_lock(&pbuf_mtx);
413 TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
414
415 if (bswneeded) {
416 bswneeded = 0;
417 wakeup(&bswneeded);
418 }
419 if (pfreecnt) {
420 if (++*pfreecnt == 1)
421 wakeup(pfreecnt);
422 }
423 mtx_unlock(&pbuf_mtx);
424 }
425
426 /*
427 * Associate a p-buffer with a vnode.
428 *
429 * Also sets B_PAGING flag to indicate that vnode is not fully associated
430 * with the buffer. i.e. the bp has not been linked into the vnode or
431 * ref-counted.
432 */
433 void
434 pbgetvp(struct vnode *vp, struct buf *bp)
435 {
436
437 KASSERT(bp->b_vp == NULL, ("pbgetvp: not free"));
438 KASSERT(bp->b_bufobj == NULL, ("pbgetvp: not free (bufobj)"));
439
440 bp->b_vp = vp;
441 bp->b_flags |= B_PAGING;
442 bp->b_bufobj = &vp->v_bufobj;
443 }
444
445 /*
446 * Associate a p-buffer with a vnode.
447 *
448 * Also sets B_PAGING flag to indicate that vnode is not fully associated
449 * with the buffer. i.e. the bp has not been linked into the vnode or
450 * ref-counted.
451 */
452 void
453 pbgetbo(struct bufobj *bo, struct buf *bp)
454 {
455
456 KASSERT(bp->b_vp == NULL, ("pbgetbo: not free (vnode)"));
457 KASSERT(bp->b_bufobj == NULL, ("pbgetbo: not free (bufobj)"));
458
459 bp->b_flags |= B_PAGING;
460 bp->b_bufobj = bo;
461 }
462
463 /*
464 * Disassociate a p-buffer from a vnode.
465 */
466 void
467 pbrelvp(struct buf *bp)
468 {
469
470 KASSERT(bp->b_vp != NULL, ("pbrelvp: NULL"));
471 KASSERT(bp->b_bufobj != NULL, ("pbrelvp: NULL bufobj"));
472
473 /* XXX REMOVE ME */
474 BO_LOCK(bp->b_bufobj);
475 if (TAILQ_NEXT(bp, b_bobufs) != NULL) {
476 panic(
477 "relpbuf(): b_vp was probably reassignbuf()d %p %x",
478 bp,
479 (int)bp->b_flags
480 );
481 }
482 BO_UNLOCK(bp->b_bufobj);
483 bp->b_vp = NULL;
484 bp->b_bufobj = NULL;
485 bp->b_flags &= ~B_PAGING;
486 }
487
488 /*
489 * Disassociate a p-buffer from a bufobj.
490 */
491 void
492 pbrelbo(struct buf *bp)
493 {
494
495 KASSERT(bp->b_vp == NULL, ("pbrelbo: vnode"));
496 KASSERT(bp->b_bufobj != NULL, ("pbrelbo: NULL bufobj"));
497
498 /* XXX REMOVE ME */
499 BO_LOCK(bp->b_bufobj);
500 if (TAILQ_NEXT(bp, b_bobufs) != NULL) {
501 panic(
502 "relpbuf(): b_vp was probably reassignbuf()d %p %x",
503 bp,
504 (int)bp->b_flags
505 );
506 }
507 BO_UNLOCK(bp->b_bufobj);
508 bp->b_bufobj = NULL;
509 bp->b_flags &= ~B_PAGING;
510 }
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