FreeBSD/Linux Kernel Cross Reference
sys/vm/swap_pager.c
1 /*-
2 * Copyright (c) 1998 Matthew Dillon,
3 * Copyright (c) 1994 John S. Dyson
4 * Copyright (c) 1990 University of Utah.
5 * Copyright (c) 1982, 1986, 1989, 1993
6 * The Regents of the University of California. All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * the Systems Programming Group of the University of Utah Computer
10 * Science Department.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Berkeley and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
39 *
40 * New Swap System
41 * Matthew Dillon
42 *
43 * Radix Bitmap 'blists'.
44 *
45 * - The new swapper uses the new radix bitmap code. This should scale
46 * to arbitrarily small or arbitrarily large swap spaces and an almost
47 * arbitrary degree of fragmentation.
48 *
49 * Features:
50 *
51 * - on the fly reallocation of swap during putpages. The new system
52 * does not try to keep previously allocated swap blocks for dirty
53 * pages.
54 *
55 * - on the fly deallocation of swap
56 *
57 * - No more garbage collection required. Unnecessarily allocated swap
58 * blocks only exist for dirty vm_page_t's now and these are already
59 * cycled (in a high-load system) by the pager. We also do on-the-fly
60 * removal of invalidated swap blocks when a page is destroyed
61 * or renamed.
62 *
63 * from: Utah $Hdr: swap_pager.c 1.4 91/04/30$
64 *
65 * @(#)swap_pager.c 8.9 (Berkeley) 3/21/94
66 * @(#)vm_swap.c 8.5 (Berkeley) 2/17/94
67 */
68
69 #include <sys/cdefs.h>
70 __FBSDID("$FreeBSD: releng/11.1/sys/vm/swap_pager.c 320693 2017-07-05 19:24:53Z markj $");
71
72 #include "opt_swap.h"
73 #include "opt_vm.h"
74
75 #include <sys/param.h>
76 #include <sys/systm.h>
77 #include <sys/conf.h>
78 #include <sys/kernel.h>
79 #include <sys/priv.h>
80 #include <sys/proc.h>
81 #include <sys/bio.h>
82 #include <sys/buf.h>
83 #include <sys/disk.h>
84 #include <sys/fcntl.h>
85 #include <sys/mount.h>
86 #include <sys/namei.h>
87 #include <sys/vnode.h>
88 #include <sys/malloc.h>
89 #include <sys/racct.h>
90 #include <sys/resource.h>
91 #include <sys/resourcevar.h>
92 #include <sys/rwlock.h>
93 #include <sys/sysctl.h>
94 #include <sys/sysproto.h>
95 #include <sys/blist.h>
96 #include <sys/lock.h>
97 #include <sys/sx.h>
98 #include <sys/vmmeter.h>
99
100 #include <security/mac/mac_framework.h>
101
102 #include <vm/vm.h>
103 #include <vm/pmap.h>
104 #include <vm/vm_map.h>
105 #include <vm/vm_kern.h>
106 #include <vm/vm_object.h>
107 #include <vm/vm_page.h>
108 #include <vm/vm_pager.h>
109 #include <vm/vm_pageout.h>
110 #include <vm/vm_param.h>
111 #include <vm/swap_pager.h>
112 #include <vm/vm_extern.h>
113 #include <vm/uma.h>
114
115 #include <geom/geom.h>
116
117 /*
118 * MAX_PAGEOUT_CLUSTER must be a power of 2 between 1 and 64.
119 * The 64-page limit is due to the radix code (kern/subr_blist.c).
120 */
121 #ifndef MAX_PAGEOUT_CLUSTER
122 #define MAX_PAGEOUT_CLUSTER 16
123 #endif
124
125 #if !defined(SWB_NPAGES)
126 #define SWB_NPAGES MAX_PAGEOUT_CLUSTER
127 #endif
128
129 /*
130 * The swblock structure maps an object and a small, fixed-size range
131 * of page indices to disk addresses within a swap area.
132 * The collection of these mappings is implemented as a hash table.
133 * Unused disk addresses within a swap area are allocated and managed
134 * using a blist.
135 */
136 #define SWCORRECT(n) (sizeof(void *) * (n) / sizeof(daddr_t))
137 #define SWAP_META_PAGES (SWB_NPAGES * 2)
138 #define SWAP_META_MASK (SWAP_META_PAGES - 1)
139
140 struct swblock {
141 struct swblock *swb_hnext;
142 vm_object_t swb_object;
143 vm_pindex_t swb_index;
144 int swb_count;
145 daddr_t swb_pages[SWAP_META_PAGES];
146 };
147
148 static MALLOC_DEFINE(M_VMPGDATA, "vm_pgdata", "swap pager private data");
149 static struct mtx sw_dev_mtx;
150 static TAILQ_HEAD(, swdevt) swtailq = TAILQ_HEAD_INITIALIZER(swtailq);
151 static struct swdevt *swdevhd; /* Allocate from here next */
152 static int nswapdev; /* Number of swap devices */
153 int swap_pager_avail;
154 static struct sx swdev_syscall_lock; /* serialize swap(on|off) */
155
156 static vm_ooffset_t swap_total;
157 SYSCTL_QUAD(_vm, OID_AUTO, swap_total, CTLFLAG_RD, &swap_total, 0,
158 "Total amount of available swap storage.");
159 static vm_ooffset_t swap_reserved;
160 SYSCTL_QUAD(_vm, OID_AUTO, swap_reserved, CTLFLAG_RD, &swap_reserved, 0,
161 "Amount of swap storage needed to back all allocated anonymous memory.");
162 static int overcommit = 0;
163 SYSCTL_INT(_vm, OID_AUTO, overcommit, CTLFLAG_RW, &overcommit, 0,
164 "Configure virtual memory overcommit behavior. See tuning(7) "
165 "for details.");
166 static unsigned long swzone;
167 SYSCTL_ULONG(_vm, OID_AUTO, swzone, CTLFLAG_RD, &swzone, 0,
168 "Actual size of swap metadata zone");
169 static unsigned long swap_maxpages;
170 SYSCTL_ULONG(_vm, OID_AUTO, swap_maxpages, CTLFLAG_RD, &swap_maxpages, 0,
171 "Maximum amount of swap supported");
172
173 /* bits from overcommit */
174 #define SWAP_RESERVE_FORCE_ON (1 << 0)
175 #define SWAP_RESERVE_RLIMIT_ON (1 << 1)
176 #define SWAP_RESERVE_ALLOW_NONWIRED (1 << 2)
177
178 int
179 swap_reserve(vm_ooffset_t incr)
180 {
181
182 return (swap_reserve_by_cred(incr, curthread->td_ucred));
183 }
184
185 int
186 swap_reserve_by_cred(vm_ooffset_t incr, struct ucred *cred)
187 {
188 vm_ooffset_t r, s;
189 int res, error;
190 static int curfail;
191 static struct timeval lastfail;
192 struct uidinfo *uip;
193
194 uip = cred->cr_ruidinfo;
195
196 if (incr & PAGE_MASK)
197 panic("swap_reserve: & PAGE_MASK");
198
199 #ifdef RACCT
200 if (racct_enable) {
201 PROC_LOCK(curproc);
202 error = racct_add(curproc, RACCT_SWAP, incr);
203 PROC_UNLOCK(curproc);
204 if (error != 0)
205 return (0);
206 }
207 #endif
208
209 res = 0;
210 mtx_lock(&sw_dev_mtx);
211 r = swap_reserved + incr;
212 if (overcommit & SWAP_RESERVE_ALLOW_NONWIRED) {
213 s = vm_cnt.v_page_count - vm_cnt.v_free_reserved - vm_cnt.v_wire_count;
214 s *= PAGE_SIZE;
215 } else
216 s = 0;
217 s += swap_total;
218 if ((overcommit & SWAP_RESERVE_FORCE_ON) == 0 || r <= s ||
219 (error = priv_check(curthread, PRIV_VM_SWAP_NOQUOTA)) == 0) {
220 res = 1;
221 swap_reserved = r;
222 }
223 mtx_unlock(&sw_dev_mtx);
224
225 if (res) {
226 UIDINFO_VMSIZE_LOCK(uip);
227 if ((overcommit & SWAP_RESERVE_RLIMIT_ON) != 0 &&
228 uip->ui_vmsize + incr > lim_cur(curthread, RLIMIT_SWAP) &&
229 priv_check(curthread, PRIV_VM_SWAP_NORLIMIT))
230 res = 0;
231 else
232 uip->ui_vmsize += incr;
233 UIDINFO_VMSIZE_UNLOCK(uip);
234 if (!res) {
235 mtx_lock(&sw_dev_mtx);
236 swap_reserved -= incr;
237 mtx_unlock(&sw_dev_mtx);
238 }
239 }
240 if (!res && ppsratecheck(&lastfail, &curfail, 1)) {
241 printf("uid %d, pid %d: swap reservation for %jd bytes failed\n",
242 uip->ui_uid, curproc->p_pid, incr);
243 }
244
245 #ifdef RACCT
246 if (!res) {
247 PROC_LOCK(curproc);
248 racct_sub(curproc, RACCT_SWAP, incr);
249 PROC_UNLOCK(curproc);
250 }
251 #endif
252
253 return (res);
254 }
255
256 void
257 swap_reserve_force(vm_ooffset_t incr)
258 {
259 struct uidinfo *uip;
260
261 mtx_lock(&sw_dev_mtx);
262 swap_reserved += incr;
263 mtx_unlock(&sw_dev_mtx);
264
265 #ifdef RACCT
266 PROC_LOCK(curproc);
267 racct_add_force(curproc, RACCT_SWAP, incr);
268 PROC_UNLOCK(curproc);
269 #endif
270
271 uip = curthread->td_ucred->cr_ruidinfo;
272 PROC_LOCK(curproc);
273 UIDINFO_VMSIZE_LOCK(uip);
274 uip->ui_vmsize += incr;
275 UIDINFO_VMSIZE_UNLOCK(uip);
276 PROC_UNLOCK(curproc);
277 }
278
279 void
280 swap_release(vm_ooffset_t decr)
281 {
282 struct ucred *cred;
283
284 PROC_LOCK(curproc);
285 cred = curthread->td_ucred;
286 swap_release_by_cred(decr, cred);
287 PROC_UNLOCK(curproc);
288 }
289
290 void
291 swap_release_by_cred(vm_ooffset_t decr, struct ucred *cred)
292 {
293 struct uidinfo *uip;
294
295 uip = cred->cr_ruidinfo;
296
297 if (decr & PAGE_MASK)
298 panic("swap_release: & PAGE_MASK");
299
300 mtx_lock(&sw_dev_mtx);
301 if (swap_reserved < decr)
302 panic("swap_reserved < decr");
303 swap_reserved -= decr;
304 mtx_unlock(&sw_dev_mtx);
305
306 UIDINFO_VMSIZE_LOCK(uip);
307 if (uip->ui_vmsize < decr)
308 printf("negative vmsize for uid = %d\n", uip->ui_uid);
309 uip->ui_vmsize -= decr;
310 UIDINFO_VMSIZE_UNLOCK(uip);
311
312 racct_sub_cred(cred, RACCT_SWAP, decr);
313 }
314
315 #define SWM_FREE 0x02 /* free, period */
316 #define SWM_POP 0x04 /* pop out */
317
318 int swap_pager_full = 2; /* swap space exhaustion (task killing) */
319 static int swap_pager_almost_full = 1; /* swap space exhaustion (w/hysteresis)*/
320 static int nsw_rcount; /* free read buffers */
321 static int nsw_wcount_sync; /* limit write buffers / synchronous */
322 static int nsw_wcount_async; /* limit write buffers / asynchronous */
323 static int nsw_wcount_async_max;/* assigned maximum */
324 static int nsw_cluster_max; /* maximum VOP I/O allowed */
325
326 static int sysctl_swap_async_max(SYSCTL_HANDLER_ARGS);
327 SYSCTL_PROC(_vm, OID_AUTO, swap_async_max, CTLTYPE_INT | CTLFLAG_RW |
328 CTLFLAG_MPSAFE, NULL, 0, sysctl_swap_async_max, "I",
329 "Maximum running async swap ops");
330
331 static struct swblock **swhash;
332 static int swhash_mask;
333 static struct mtx swhash_mtx;
334
335 static struct sx sw_alloc_sx;
336
337 /*
338 * "named" and "unnamed" anon region objects. Try to reduce the overhead
339 * of searching a named list by hashing it just a little.
340 */
341
342 #define NOBJLISTS 8
343
344 #define NOBJLIST(handle) \
345 (&swap_pager_object_list[((int)(intptr_t)handle >> 4) & (NOBJLISTS-1)])
346
347 static struct pagerlst swap_pager_object_list[NOBJLISTS];
348 static uma_zone_t swap_zone;
349
350 /*
351 * pagerops for OBJT_SWAP - "swap pager". Some ops are also global procedure
352 * calls hooked from other parts of the VM system and do not appear here.
353 * (see vm/swap_pager.h).
354 */
355 static vm_object_t
356 swap_pager_alloc(void *handle, vm_ooffset_t size,
357 vm_prot_t prot, vm_ooffset_t offset, struct ucred *);
358 static void swap_pager_dealloc(vm_object_t object);
359 static int swap_pager_getpages(vm_object_t, vm_page_t *, int, int *,
360 int *);
361 static int swap_pager_getpages_async(vm_object_t, vm_page_t *, int, int *,
362 int *, pgo_getpages_iodone_t, void *);
363 static void swap_pager_putpages(vm_object_t, vm_page_t *, int, boolean_t, int *);
364 static boolean_t
365 swap_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before, int *after);
366 static void swap_pager_init(void);
367 static void swap_pager_unswapped(vm_page_t);
368 static void swap_pager_swapoff(struct swdevt *sp);
369
370 struct pagerops swappagerops = {
371 .pgo_init = swap_pager_init, /* early system initialization of pager */
372 .pgo_alloc = swap_pager_alloc, /* allocate an OBJT_SWAP object */
373 .pgo_dealloc = swap_pager_dealloc, /* deallocate an OBJT_SWAP object */
374 .pgo_getpages = swap_pager_getpages, /* pagein */
375 .pgo_getpages_async = swap_pager_getpages_async, /* pagein (async) */
376 .pgo_putpages = swap_pager_putpages, /* pageout */
377 .pgo_haspage = swap_pager_haspage, /* get backing store status for page */
378 .pgo_pageunswapped = swap_pager_unswapped, /* remove swap related to page */
379 };
380
381 /*
382 * swap_*() routines are externally accessible. swp_*() routines are
383 * internal.
384 */
385 static int nswap_lowat = 128; /* in pages, swap_pager_almost_full warn */
386 static int nswap_hiwat = 512; /* in pages, swap_pager_almost_full warn */
387
388 SYSCTL_INT(_vm, OID_AUTO, dmmax, CTLFLAG_RD, &nsw_cluster_max, 0,
389 "Maximum size of a swap block in pages");
390
391 static void swp_sizecheck(void);
392 static void swp_pager_async_iodone(struct buf *bp);
393 static int swapongeom(struct vnode *);
394 static int swaponvp(struct thread *, struct vnode *, u_long);
395 static int swapoff_one(struct swdevt *sp, struct ucred *cred);
396
397 /*
398 * Swap bitmap functions
399 */
400 static void swp_pager_freeswapspace(daddr_t blk, int npages);
401 static daddr_t swp_pager_getswapspace(int npages);
402
403 /*
404 * Metadata functions
405 */
406 static struct swblock **swp_pager_hash(vm_object_t object, vm_pindex_t index);
407 static void swp_pager_meta_build(vm_object_t, vm_pindex_t, daddr_t);
408 static void swp_pager_meta_free(vm_object_t, vm_pindex_t, vm_pindex_t);
409 static void swp_pager_meta_free_all(vm_object_t);
410 static daddr_t swp_pager_meta_ctl(vm_object_t, vm_pindex_t, int);
411
412 /*
413 * SWP_SIZECHECK() - update swap_pager_full indication
414 *
415 * update the swap_pager_almost_full indication and warn when we are
416 * about to run out of swap space, using lowat/hiwat hysteresis.
417 *
418 * Clear swap_pager_full ( task killing ) indication when lowat is met.
419 *
420 * No restrictions on call
421 * This routine may not block.
422 */
423 static void
424 swp_sizecheck(void)
425 {
426
427 if (swap_pager_avail < nswap_lowat) {
428 if (swap_pager_almost_full == 0) {
429 printf("swap_pager: out of swap space\n");
430 swap_pager_almost_full = 1;
431 }
432 } else {
433 swap_pager_full = 0;
434 if (swap_pager_avail > nswap_hiwat)
435 swap_pager_almost_full = 0;
436 }
437 }
438
439 /*
440 * SWP_PAGER_HASH() - hash swap meta data
441 *
442 * This is an helper function which hashes the swapblk given
443 * the object and page index. It returns a pointer to a pointer
444 * to the object, or a pointer to a NULL pointer if it could not
445 * find a swapblk.
446 */
447 static struct swblock **
448 swp_pager_hash(vm_object_t object, vm_pindex_t index)
449 {
450 struct swblock **pswap;
451 struct swblock *swap;
452
453 index &= ~(vm_pindex_t)SWAP_META_MASK;
454 pswap = &swhash[(index ^ (int)(intptr_t)object) & swhash_mask];
455 while ((swap = *pswap) != NULL) {
456 if (swap->swb_object == object &&
457 swap->swb_index == index
458 ) {
459 break;
460 }
461 pswap = &swap->swb_hnext;
462 }
463 return (pswap);
464 }
465
466 /*
467 * SWAP_PAGER_INIT() - initialize the swap pager!
468 *
469 * Expected to be started from system init. NOTE: This code is run
470 * before much else so be careful what you depend on. Most of the VM
471 * system has yet to be initialized at this point.
472 */
473 static void
474 swap_pager_init(void)
475 {
476 /*
477 * Initialize object lists
478 */
479 int i;
480
481 for (i = 0; i < NOBJLISTS; ++i)
482 TAILQ_INIT(&swap_pager_object_list[i]);
483 mtx_init(&sw_dev_mtx, "swapdev", NULL, MTX_DEF);
484 sx_init(&sw_alloc_sx, "swspsx");
485 sx_init(&swdev_syscall_lock, "swsysc");
486 }
487
488 /*
489 * SWAP_PAGER_SWAP_INIT() - swap pager initialization from pageout process
490 *
491 * Expected to be started from pageout process once, prior to entering
492 * its main loop.
493 */
494 void
495 swap_pager_swap_init(void)
496 {
497 unsigned long n, n2;
498
499 /*
500 * Number of in-transit swap bp operations. Don't
501 * exhaust the pbufs completely. Make sure we
502 * initialize workable values (0 will work for hysteresis
503 * but it isn't very efficient).
504 *
505 * The nsw_cluster_max is constrained by the bp->b_pages[]
506 * array (MAXPHYS/PAGE_SIZE) and our locally defined
507 * MAX_PAGEOUT_CLUSTER. Also be aware that swap ops are
508 * constrained by the swap device interleave stripe size.
509 *
510 * Currently we hardwire nsw_wcount_async to 4. This limit is
511 * designed to prevent other I/O from having high latencies due to
512 * our pageout I/O. The value 4 works well for one or two active swap
513 * devices but is probably a little low if you have more. Even so,
514 * a higher value would probably generate only a limited improvement
515 * with three or four active swap devices since the system does not
516 * typically have to pageout at extreme bandwidths. We will want
517 * at least 2 per swap devices, and 4 is a pretty good value if you
518 * have one NFS swap device due to the command/ack latency over NFS.
519 * So it all works out pretty well.
520 */
521 nsw_cluster_max = min((MAXPHYS/PAGE_SIZE), MAX_PAGEOUT_CLUSTER);
522
523 mtx_lock(&pbuf_mtx);
524 nsw_rcount = (nswbuf + 1) / 2;
525 nsw_wcount_sync = (nswbuf + 3) / 4;
526 nsw_wcount_async = 4;
527 nsw_wcount_async_max = nsw_wcount_async;
528 mtx_unlock(&pbuf_mtx);
529
530 /*
531 * Initialize our zone. Right now I'm just guessing on the number
532 * we need based on the number of pages in the system. Each swblock
533 * can hold 32 pages, so this is probably overkill. This reservation
534 * is typically limited to around 32MB by default.
535 */
536 n = vm_cnt.v_page_count / 2;
537 if (maxswzone && n > maxswzone / sizeof(struct swblock))
538 n = maxswzone / sizeof(struct swblock);
539 n2 = n;
540 swap_zone = uma_zcreate("SWAPMETA", sizeof(struct swblock), NULL, NULL,
541 NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE | UMA_ZONE_VM);
542 if (swap_zone == NULL)
543 panic("failed to create swap_zone.");
544 do {
545 if (uma_zone_reserve_kva(swap_zone, n))
546 break;
547 /*
548 * if the allocation failed, try a zone two thirds the
549 * size of the previous attempt.
550 */
551 n -= ((n + 2) / 3);
552 } while (n > 0);
553 if (n2 != n)
554 printf("Swap zone entries reduced from %lu to %lu.\n", n2, n);
555 swap_maxpages = n * SWAP_META_PAGES;
556 swzone = n * sizeof(struct swblock);
557 n2 = n;
558
559 /*
560 * Initialize our meta-data hash table. The swapper does not need to
561 * be quite as efficient as the VM system, so we do not use an
562 * oversized hash table.
563 *
564 * n: size of hash table, must be power of 2
565 * swhash_mask: hash table index mask
566 */
567 for (n = 1; n < n2 / 8; n *= 2)
568 ;
569 swhash = malloc(sizeof(struct swblock *) * n, M_VMPGDATA, M_WAITOK | M_ZERO);
570 swhash_mask = n - 1;
571 mtx_init(&swhash_mtx, "swap_pager swhash", NULL, MTX_DEF);
572 }
573
574 static vm_object_t
575 swap_pager_alloc_init(void *handle, struct ucred *cred, vm_ooffset_t size,
576 vm_ooffset_t offset)
577 {
578 vm_object_t object;
579
580 if (cred != NULL) {
581 if (!swap_reserve_by_cred(size, cred))
582 return (NULL);
583 crhold(cred);
584 }
585 object = vm_object_allocate(OBJT_SWAP, OFF_TO_IDX(offset +
586 PAGE_MASK + size));
587 object->handle = handle;
588 if (cred != NULL) {
589 object->cred = cred;
590 object->charge = size;
591 }
592 object->un_pager.swp.swp_bcount = 0;
593 return (object);
594 }
595
596 /*
597 * SWAP_PAGER_ALLOC() - allocate a new OBJT_SWAP VM object and instantiate
598 * its metadata structures.
599 *
600 * This routine is called from the mmap and fork code to create a new
601 * OBJT_SWAP object.
602 *
603 * This routine must ensure that no live duplicate is created for
604 * the named object request, which is protected against by
605 * holding the sw_alloc_sx lock in case handle != NULL.
606 */
607 static vm_object_t
608 swap_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
609 vm_ooffset_t offset, struct ucred *cred)
610 {
611 vm_object_t object;
612
613 if (handle != NULL) {
614 /*
615 * Reference existing named region or allocate new one. There
616 * should not be a race here against swp_pager_meta_build()
617 * as called from vm_page_remove() in regards to the lookup
618 * of the handle.
619 */
620 sx_xlock(&sw_alloc_sx);
621 object = vm_pager_object_lookup(NOBJLIST(handle), handle);
622 if (object == NULL) {
623 object = swap_pager_alloc_init(handle, cred, size,
624 offset);
625 if (object != NULL) {
626 TAILQ_INSERT_TAIL(NOBJLIST(object->handle),
627 object, pager_object_list);
628 }
629 }
630 sx_xunlock(&sw_alloc_sx);
631 } else {
632 object = swap_pager_alloc_init(handle, cred, size, offset);
633 }
634 return (object);
635 }
636
637 /*
638 * SWAP_PAGER_DEALLOC() - remove swap metadata from object
639 *
640 * The swap backing for the object is destroyed. The code is
641 * designed such that we can reinstantiate it later, but this
642 * routine is typically called only when the entire object is
643 * about to be destroyed.
644 *
645 * The object must be locked.
646 */
647 static void
648 swap_pager_dealloc(vm_object_t object)
649 {
650
651 VM_OBJECT_ASSERT_WLOCKED(object);
652 KASSERT((object->flags & OBJ_DEAD) != 0, ("dealloc of reachable obj"));
653
654 /*
655 * Remove from list right away so lookups will fail if we block for
656 * pageout completion.
657 */
658 if (object->handle != NULL) {
659 VM_OBJECT_WUNLOCK(object);
660 sx_xlock(&sw_alloc_sx);
661 TAILQ_REMOVE(NOBJLIST(object->handle), object,
662 pager_object_list);
663 sx_xunlock(&sw_alloc_sx);
664 VM_OBJECT_WLOCK(object);
665 }
666
667 vm_object_pip_wait(object, "swpdea");
668
669 /*
670 * Free all remaining metadata. We only bother to free it from
671 * the swap meta data. We do not attempt to free swapblk's still
672 * associated with vm_page_t's for this object. We do not care
673 * if paging is still in progress on some objects.
674 */
675 swp_pager_meta_free_all(object);
676 object->handle = NULL;
677 object->type = OBJT_DEAD;
678 }
679
680 /************************************************************************
681 * SWAP PAGER BITMAP ROUTINES *
682 ************************************************************************/
683
684 /*
685 * SWP_PAGER_GETSWAPSPACE() - allocate raw swap space
686 *
687 * Allocate swap for the requested number of pages. The starting
688 * swap block number (a page index) is returned or SWAPBLK_NONE
689 * if the allocation failed.
690 *
691 * Also has the side effect of advising that somebody made a mistake
692 * when they configured swap and didn't configure enough.
693 *
694 * This routine may not sleep.
695 *
696 * We allocate in round-robin fashion from the configured devices.
697 */
698 static daddr_t
699 swp_pager_getswapspace(int npages)
700 {
701 daddr_t blk;
702 struct swdevt *sp;
703 int i;
704
705 blk = SWAPBLK_NONE;
706 mtx_lock(&sw_dev_mtx);
707 sp = swdevhd;
708 for (i = 0; i < nswapdev; i++) {
709 if (sp == NULL)
710 sp = TAILQ_FIRST(&swtailq);
711 if (!(sp->sw_flags & SW_CLOSING)) {
712 blk = blist_alloc(sp->sw_blist, npages);
713 if (blk != SWAPBLK_NONE) {
714 blk += sp->sw_first;
715 sp->sw_used += npages;
716 swap_pager_avail -= npages;
717 swp_sizecheck();
718 swdevhd = TAILQ_NEXT(sp, sw_list);
719 goto done;
720 }
721 }
722 sp = TAILQ_NEXT(sp, sw_list);
723 }
724 if (swap_pager_full != 2) {
725 printf("swap_pager_getswapspace(%d): failed\n", npages);
726 swap_pager_full = 2;
727 swap_pager_almost_full = 1;
728 }
729 swdevhd = NULL;
730 done:
731 mtx_unlock(&sw_dev_mtx);
732 return (blk);
733 }
734
735 static int
736 swp_pager_isondev(daddr_t blk, struct swdevt *sp)
737 {
738
739 return (blk >= sp->sw_first && blk < sp->sw_end);
740 }
741
742 static void
743 swp_pager_strategy(struct buf *bp)
744 {
745 struct swdevt *sp;
746
747 mtx_lock(&sw_dev_mtx);
748 TAILQ_FOREACH(sp, &swtailq, sw_list) {
749 if (bp->b_blkno >= sp->sw_first && bp->b_blkno < sp->sw_end) {
750 mtx_unlock(&sw_dev_mtx);
751 if ((sp->sw_flags & SW_UNMAPPED) != 0 &&
752 unmapped_buf_allowed) {
753 bp->b_data = unmapped_buf;
754 bp->b_offset = 0;
755 } else {
756 pmap_qenter((vm_offset_t)bp->b_data,
757 &bp->b_pages[0], bp->b_bcount / PAGE_SIZE);
758 }
759 sp->sw_strategy(bp, sp);
760 return;
761 }
762 }
763 panic("Swapdev not found");
764 }
765
766
767 /*
768 * SWP_PAGER_FREESWAPSPACE() - free raw swap space
769 *
770 * This routine returns the specified swap blocks back to the bitmap.
771 *
772 * This routine may not sleep.
773 */
774 static void
775 swp_pager_freeswapspace(daddr_t blk, int npages)
776 {
777 struct swdevt *sp;
778
779 mtx_lock(&sw_dev_mtx);
780 TAILQ_FOREACH(sp, &swtailq, sw_list) {
781 if (blk >= sp->sw_first && blk < sp->sw_end) {
782 sp->sw_used -= npages;
783 /*
784 * If we are attempting to stop swapping on
785 * this device, we don't want to mark any
786 * blocks free lest they be reused.
787 */
788 if ((sp->sw_flags & SW_CLOSING) == 0) {
789 blist_free(sp->sw_blist, blk - sp->sw_first,
790 npages);
791 swap_pager_avail += npages;
792 swp_sizecheck();
793 }
794 mtx_unlock(&sw_dev_mtx);
795 return;
796 }
797 }
798 panic("Swapdev not found");
799 }
800
801 /*
802 * SWAP_PAGER_FREESPACE() - frees swap blocks associated with a page
803 * range within an object.
804 *
805 * This is a globally accessible routine.
806 *
807 * This routine removes swapblk assignments from swap metadata.
808 *
809 * The external callers of this routine typically have already destroyed
810 * or renamed vm_page_t's associated with this range in the object so
811 * we should be ok.
812 *
813 * The object must be locked.
814 */
815 void
816 swap_pager_freespace(vm_object_t object, vm_pindex_t start, vm_size_t size)
817 {
818
819 swp_pager_meta_free(object, start, size);
820 }
821
822 /*
823 * SWAP_PAGER_RESERVE() - reserve swap blocks in object
824 *
825 * Assigns swap blocks to the specified range within the object. The
826 * swap blocks are not zeroed. Any previous swap assignment is destroyed.
827 *
828 * Returns 0 on success, -1 on failure.
829 */
830 int
831 swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_size_t size)
832 {
833 int n = 0;
834 daddr_t blk = SWAPBLK_NONE;
835 vm_pindex_t beg = start; /* save start index */
836
837 VM_OBJECT_WLOCK(object);
838 while (size) {
839 if (n == 0) {
840 n = BLIST_MAX_ALLOC;
841 while ((blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE) {
842 n >>= 1;
843 if (n == 0) {
844 swp_pager_meta_free(object, beg, start - beg);
845 VM_OBJECT_WUNLOCK(object);
846 return (-1);
847 }
848 }
849 }
850 swp_pager_meta_build(object, start, blk);
851 --size;
852 ++start;
853 ++blk;
854 --n;
855 }
856 swp_pager_meta_free(object, start, n);
857 VM_OBJECT_WUNLOCK(object);
858 return (0);
859 }
860
861 /*
862 * SWAP_PAGER_COPY() - copy blocks from source pager to destination pager
863 * and destroy the source.
864 *
865 * Copy any valid swapblks from the source to the destination. In
866 * cases where both the source and destination have a valid swapblk,
867 * we keep the destination's.
868 *
869 * This routine is allowed to sleep. It may sleep allocating metadata
870 * indirectly through swp_pager_meta_build() or if paging is still in
871 * progress on the source.
872 *
873 * The source object contains no vm_page_t's (which is just as well)
874 *
875 * The source object is of type OBJT_SWAP.
876 *
877 * The source and destination objects must be locked.
878 * Both object locks may temporarily be released.
879 */
880 void
881 swap_pager_copy(vm_object_t srcobject, vm_object_t dstobject,
882 vm_pindex_t offset, int destroysource)
883 {
884 vm_pindex_t i;
885
886 VM_OBJECT_ASSERT_WLOCKED(srcobject);
887 VM_OBJECT_ASSERT_WLOCKED(dstobject);
888
889 /*
890 * If destroysource is set, we remove the source object from the
891 * swap_pager internal queue now.
892 */
893 if (destroysource && srcobject->handle != NULL) {
894 vm_object_pip_add(srcobject, 1);
895 VM_OBJECT_WUNLOCK(srcobject);
896 vm_object_pip_add(dstobject, 1);
897 VM_OBJECT_WUNLOCK(dstobject);
898 sx_xlock(&sw_alloc_sx);
899 TAILQ_REMOVE(NOBJLIST(srcobject->handle), srcobject,
900 pager_object_list);
901 sx_xunlock(&sw_alloc_sx);
902 VM_OBJECT_WLOCK(dstobject);
903 vm_object_pip_wakeup(dstobject);
904 VM_OBJECT_WLOCK(srcobject);
905 vm_object_pip_wakeup(srcobject);
906 }
907
908 /*
909 * transfer source to destination.
910 */
911 for (i = 0; i < dstobject->size; ++i) {
912 daddr_t dstaddr;
913
914 /*
915 * Locate (without changing) the swapblk on the destination,
916 * unless it is invalid in which case free it silently, or
917 * if the destination is a resident page, in which case the
918 * source is thrown away.
919 */
920 dstaddr = swp_pager_meta_ctl(dstobject, i, 0);
921
922 if (dstaddr == SWAPBLK_NONE) {
923 /*
924 * Destination has no swapblk and is not resident,
925 * copy source.
926 */
927 daddr_t srcaddr;
928
929 srcaddr = swp_pager_meta_ctl(
930 srcobject,
931 i + offset,
932 SWM_POP
933 );
934
935 if (srcaddr != SWAPBLK_NONE) {
936 /*
937 * swp_pager_meta_build() can sleep.
938 */
939 vm_object_pip_add(srcobject, 1);
940 VM_OBJECT_WUNLOCK(srcobject);
941 vm_object_pip_add(dstobject, 1);
942 swp_pager_meta_build(dstobject, i, srcaddr);
943 vm_object_pip_wakeup(dstobject);
944 VM_OBJECT_WLOCK(srcobject);
945 vm_object_pip_wakeup(srcobject);
946 }
947 } else {
948 /*
949 * Destination has valid swapblk or it is represented
950 * by a resident page. We destroy the sourceblock.
951 */
952
953 swp_pager_meta_ctl(srcobject, i + offset, SWM_FREE);
954 }
955 }
956
957 /*
958 * Free left over swap blocks in source.
959 *
960 * We have to revert the type to OBJT_DEFAULT so we do not accidentally
961 * double-remove the object from the swap queues.
962 */
963 if (destroysource) {
964 swp_pager_meta_free_all(srcobject);
965 /*
966 * Reverting the type is not necessary, the caller is going
967 * to destroy srcobject directly, but I'm doing it here
968 * for consistency since we've removed the object from its
969 * queues.
970 */
971 srcobject->type = OBJT_DEFAULT;
972 }
973 }
974
975 /*
976 * SWAP_PAGER_HASPAGE() - determine if we have good backing store for
977 * the requested page.
978 *
979 * We determine whether good backing store exists for the requested
980 * page and return TRUE if it does, FALSE if it doesn't.
981 *
982 * If TRUE, we also try to determine how much valid, contiguous backing
983 * store exists before and after the requested page.
984 */
985 static boolean_t
986 swap_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
987 int *after)
988 {
989 daddr_t blk, blk0;
990 int i;
991
992 VM_OBJECT_ASSERT_LOCKED(object);
993
994 /*
995 * do we have good backing store at the requested index ?
996 */
997 blk0 = swp_pager_meta_ctl(object, pindex, 0);
998 if (blk0 == SWAPBLK_NONE) {
999 if (before)
1000 *before = 0;
1001 if (after)
1002 *after = 0;
1003 return (FALSE);
1004 }
1005
1006 /*
1007 * find backwards-looking contiguous good backing store
1008 */
1009 if (before != NULL) {
1010 for (i = 1; i < SWB_NPAGES; i++) {
1011 if (i > pindex)
1012 break;
1013 blk = swp_pager_meta_ctl(object, pindex - i, 0);
1014 if (blk != blk0 - i)
1015 break;
1016 }
1017 *before = i - 1;
1018 }
1019
1020 /*
1021 * find forward-looking contiguous good backing store
1022 */
1023 if (after != NULL) {
1024 for (i = 1; i < SWB_NPAGES; i++) {
1025 blk = swp_pager_meta_ctl(object, pindex + i, 0);
1026 if (blk != blk0 + i)
1027 break;
1028 }
1029 *after = i - 1;
1030 }
1031 return (TRUE);
1032 }
1033
1034 /*
1035 * SWAP_PAGER_PAGE_UNSWAPPED() - remove swap backing store related to page
1036 *
1037 * This removes any associated swap backing store, whether valid or
1038 * not, from the page.
1039 *
1040 * This routine is typically called when a page is made dirty, at
1041 * which point any associated swap can be freed. MADV_FREE also
1042 * calls us in a special-case situation
1043 *
1044 * NOTE!!! If the page is clean and the swap was valid, the caller
1045 * should make the page dirty before calling this routine. This routine
1046 * does NOT change the m->dirty status of the page. Also: MADV_FREE
1047 * depends on it.
1048 *
1049 * This routine may not sleep.
1050 *
1051 * The object containing the page must be locked.
1052 */
1053 static void
1054 swap_pager_unswapped(vm_page_t m)
1055 {
1056
1057 swp_pager_meta_ctl(m->object, m->pindex, SWM_FREE);
1058 }
1059
1060 /*
1061 * swap_pager_getpages() - bring pages in from swap
1062 *
1063 * Attempt to page in the pages in array "m" of length "count". The caller
1064 * may optionally specify that additional pages preceding and succeeding
1065 * the specified range be paged in. The number of such pages is returned
1066 * in the "rbehind" and "rahead" parameters, and they will be in the
1067 * inactive queue upon return.
1068 *
1069 * The pages in "m" must be busied and will remain busied upon return.
1070 */
1071 static int
1072 swap_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
1073 int *rahead)
1074 {
1075 struct buf *bp;
1076 vm_page_t mpred, msucc, p;
1077 vm_pindex_t pindex;
1078 daddr_t blk;
1079 int i, j, maxahead, maxbehind, reqcount, shift;
1080
1081 reqcount = count;
1082
1083 VM_OBJECT_WUNLOCK(object);
1084 bp = getpbuf(&nsw_rcount);
1085 VM_OBJECT_WLOCK(object);
1086
1087 if (!swap_pager_haspage(object, m[0]->pindex, &maxbehind, &maxahead)) {
1088 relpbuf(bp, &nsw_rcount);
1089 return (VM_PAGER_FAIL);
1090 }
1091
1092 /*
1093 * Clip the readahead and readbehind ranges to exclude resident pages.
1094 */
1095 if (rahead != NULL) {
1096 KASSERT(reqcount - 1 <= maxahead,
1097 ("page count %d extends beyond swap block", reqcount));
1098 *rahead = imin(*rahead, maxahead - (reqcount - 1));
1099 pindex = m[reqcount - 1]->pindex;
1100 msucc = TAILQ_NEXT(m[reqcount - 1], listq);
1101 if (msucc != NULL && msucc->pindex - pindex - 1 < *rahead)
1102 *rahead = msucc->pindex - pindex - 1;
1103 }
1104 if (rbehind != NULL) {
1105 *rbehind = imin(*rbehind, maxbehind);
1106 pindex = m[0]->pindex;
1107 mpred = TAILQ_PREV(m[0], pglist, listq);
1108 if (mpred != NULL && pindex - mpred->pindex - 1 < *rbehind)
1109 *rbehind = pindex - mpred->pindex - 1;
1110 }
1111
1112 /*
1113 * Allocate readahead and readbehind pages.
1114 */
1115 shift = rbehind != NULL ? *rbehind : 0;
1116 if (shift != 0) {
1117 for (i = 1; i <= shift; i++) {
1118 p = vm_page_alloc(object, m[0]->pindex - i,
1119 VM_ALLOC_NORMAL);
1120 if (p == NULL) {
1121 /* Shift allocated pages to the left. */
1122 for (j = 0; j < i - 1; j++)
1123 bp->b_pages[j] =
1124 bp->b_pages[j + shift - i + 1];
1125 break;
1126 }
1127 bp->b_pages[shift - i] = p;
1128 }
1129 shift = i - 1;
1130 *rbehind = shift;
1131 }
1132 for (i = 0; i < reqcount; i++)
1133 bp->b_pages[i + shift] = m[i];
1134 if (rahead != NULL) {
1135 for (i = 0; i < *rahead; i++) {
1136 p = vm_page_alloc(object,
1137 m[reqcount - 1]->pindex + i + 1, VM_ALLOC_NORMAL);
1138 if (p == NULL)
1139 break;
1140 bp->b_pages[shift + reqcount + i] = p;
1141 }
1142 *rahead = i;
1143 }
1144 if (rbehind != NULL)
1145 count += *rbehind;
1146 if (rahead != NULL)
1147 count += *rahead;
1148
1149 vm_object_pip_add(object, count);
1150
1151 for (i = 0; i < count; i++)
1152 bp->b_pages[i]->oflags |= VPO_SWAPINPROG;
1153
1154 pindex = bp->b_pages[0]->pindex;
1155 blk = swp_pager_meta_ctl(object, pindex, 0);
1156 KASSERT(blk != SWAPBLK_NONE,
1157 ("no swap blocking containing %p(%jx)", object, (uintmax_t)pindex));
1158
1159 VM_OBJECT_WUNLOCK(object);
1160
1161 bp->b_flags |= B_PAGING;
1162 bp->b_iocmd = BIO_READ;
1163 bp->b_iodone = swp_pager_async_iodone;
1164 bp->b_rcred = crhold(thread0.td_ucred);
1165 bp->b_wcred = crhold(thread0.td_ucred);
1166 bp->b_blkno = blk;
1167 bp->b_bcount = PAGE_SIZE * count;
1168 bp->b_bufsize = PAGE_SIZE * count;
1169 bp->b_npages = count;
1170 bp->b_pgbefore = rbehind != NULL ? *rbehind : 0;
1171 bp->b_pgafter = rahead != NULL ? *rahead : 0;
1172
1173 PCPU_INC(cnt.v_swapin);
1174 PCPU_ADD(cnt.v_swappgsin, count);
1175
1176 /*
1177 * perform the I/O. NOTE!!! bp cannot be considered valid after
1178 * this point because we automatically release it on completion.
1179 * Instead, we look at the one page we are interested in which we
1180 * still hold a lock on even through the I/O completion.
1181 *
1182 * The other pages in our m[] array are also released on completion,
1183 * so we cannot assume they are valid anymore either.
1184 *
1185 * NOTE: b_blkno is destroyed by the call to swapdev_strategy
1186 */
1187 BUF_KERNPROC(bp);
1188 swp_pager_strategy(bp);
1189
1190 /*
1191 * Wait for the pages we want to complete. VPO_SWAPINPROG is always
1192 * cleared on completion. If an I/O error occurs, SWAPBLK_NONE
1193 * is set in the metadata for each page in the request.
1194 */
1195 VM_OBJECT_WLOCK(object);
1196 while ((m[0]->oflags & VPO_SWAPINPROG) != 0) {
1197 m[0]->oflags |= VPO_SWAPSLEEP;
1198 PCPU_INC(cnt.v_intrans);
1199 if (VM_OBJECT_SLEEP(object, &object->paging_in_progress, PSWP,
1200 "swread", hz * 20)) {
1201 printf(
1202 "swap_pager: indefinite wait buffer: bufobj: %p, blkno: %jd, size: %ld\n",
1203 bp->b_bufobj, (intmax_t)bp->b_blkno, bp->b_bcount);
1204 }
1205 }
1206
1207 /*
1208 * If we had an unrecoverable read error pages will not be valid.
1209 */
1210 for (i = 0; i < reqcount; i++)
1211 if (m[i]->valid != VM_PAGE_BITS_ALL)
1212 return (VM_PAGER_ERROR);
1213
1214 return (VM_PAGER_OK);
1215
1216 /*
1217 * A final note: in a low swap situation, we cannot deallocate swap
1218 * and mark a page dirty here because the caller is likely to mark
1219 * the page clean when we return, causing the page to possibly revert
1220 * to all-zero's later.
1221 */
1222 }
1223
1224 /*
1225 * swap_pager_getpages_async():
1226 *
1227 * Right now this is emulation of asynchronous operation on top of
1228 * swap_pager_getpages().
1229 */
1230 static int
1231 swap_pager_getpages_async(vm_object_t object, vm_page_t *m, int count,
1232 int *rbehind, int *rahead, pgo_getpages_iodone_t iodone, void *arg)
1233 {
1234 int r, error;
1235
1236 r = swap_pager_getpages(object, m, count, rbehind, rahead);
1237 VM_OBJECT_WUNLOCK(object);
1238 switch (r) {
1239 case VM_PAGER_OK:
1240 error = 0;
1241 break;
1242 case VM_PAGER_ERROR:
1243 error = EIO;
1244 break;
1245 case VM_PAGER_FAIL:
1246 error = EINVAL;
1247 break;
1248 default:
1249 panic("unhandled swap_pager_getpages() error %d", r);
1250 }
1251 (iodone)(arg, m, count, error);
1252 VM_OBJECT_WLOCK(object);
1253
1254 return (r);
1255 }
1256
1257 /*
1258 * swap_pager_putpages:
1259 *
1260 * Assign swap (if necessary) and initiate I/O on the specified pages.
1261 *
1262 * We support both OBJT_DEFAULT and OBJT_SWAP objects. DEFAULT objects
1263 * are automatically converted to SWAP objects.
1264 *
1265 * In a low memory situation we may block in VOP_STRATEGY(), but the new
1266 * vm_page reservation system coupled with properly written VFS devices
1267 * should ensure that no low-memory deadlock occurs. This is an area
1268 * which needs work.
1269 *
1270 * The parent has N vm_object_pip_add() references prior to
1271 * calling us and will remove references for rtvals[] that are
1272 * not set to VM_PAGER_PEND. We need to remove the rest on I/O
1273 * completion.
1274 *
1275 * The parent has soft-busy'd the pages it passes us and will unbusy
1276 * those whos rtvals[] entry is not set to VM_PAGER_PEND on return.
1277 * We need to unbusy the rest on I/O completion.
1278 */
1279 static void
1280 swap_pager_putpages(vm_object_t object, vm_page_t *m, int count,
1281 int flags, int *rtvals)
1282 {
1283 int i, n;
1284 boolean_t sync;
1285
1286 if (count && m[0]->object != object) {
1287 panic("swap_pager_putpages: object mismatch %p/%p",
1288 object,
1289 m[0]->object
1290 );
1291 }
1292
1293 /*
1294 * Step 1
1295 *
1296 * Turn object into OBJT_SWAP
1297 * check for bogus sysops
1298 * force sync if not pageout process
1299 */
1300 if (object->type != OBJT_SWAP)
1301 swp_pager_meta_build(object, 0, SWAPBLK_NONE);
1302 VM_OBJECT_WUNLOCK(object);
1303
1304 n = 0;
1305 if (curproc != pageproc)
1306 sync = TRUE;
1307 else
1308 sync = (flags & VM_PAGER_PUT_SYNC) != 0;
1309
1310 /*
1311 * Step 2
1312 *
1313 * Assign swap blocks and issue I/O. We reallocate swap on the fly.
1314 * The page is left dirty until the pageout operation completes
1315 * successfully.
1316 */
1317 for (i = 0; i < count; i += n) {
1318 int j;
1319 struct buf *bp;
1320 daddr_t blk;
1321
1322 /*
1323 * Maximum I/O size is limited by a number of factors.
1324 */
1325 n = min(BLIST_MAX_ALLOC, count - i);
1326 n = min(n, nsw_cluster_max);
1327
1328 /*
1329 * Get biggest block of swap we can. If we fail, fall
1330 * back and try to allocate a smaller block. Don't go
1331 * overboard trying to allocate space if it would overly
1332 * fragment swap.
1333 */
1334 while (
1335 (blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE &&
1336 n > 4
1337 ) {
1338 n >>= 1;
1339 }
1340 if (blk == SWAPBLK_NONE) {
1341 for (j = 0; j < n; ++j)
1342 rtvals[i+j] = VM_PAGER_FAIL;
1343 continue;
1344 }
1345
1346 /*
1347 * All I/O parameters have been satisfied, build the I/O
1348 * request and assign the swap space.
1349 */
1350 if (sync == TRUE) {
1351 bp = getpbuf(&nsw_wcount_sync);
1352 } else {
1353 bp = getpbuf(&nsw_wcount_async);
1354 bp->b_flags = B_ASYNC;
1355 }
1356 bp->b_flags |= B_PAGING;
1357 bp->b_iocmd = BIO_WRITE;
1358
1359 bp->b_rcred = crhold(thread0.td_ucred);
1360 bp->b_wcred = crhold(thread0.td_ucred);
1361 bp->b_bcount = PAGE_SIZE * n;
1362 bp->b_bufsize = PAGE_SIZE * n;
1363 bp->b_blkno = blk;
1364
1365 VM_OBJECT_WLOCK(object);
1366 for (j = 0; j < n; ++j) {
1367 vm_page_t mreq = m[i+j];
1368
1369 swp_pager_meta_build(
1370 mreq->object,
1371 mreq->pindex,
1372 blk + j
1373 );
1374 vm_page_dirty(mreq);
1375 mreq->oflags |= VPO_SWAPINPROG;
1376 bp->b_pages[j] = mreq;
1377 }
1378 VM_OBJECT_WUNLOCK(object);
1379 bp->b_npages = n;
1380 /*
1381 * Must set dirty range for NFS to work.
1382 */
1383 bp->b_dirtyoff = 0;
1384 bp->b_dirtyend = bp->b_bcount;
1385
1386 PCPU_INC(cnt.v_swapout);
1387 PCPU_ADD(cnt.v_swappgsout, bp->b_npages);
1388
1389 /*
1390 * We unconditionally set rtvals[] to VM_PAGER_PEND so that we
1391 * can call the async completion routine at the end of a
1392 * synchronous I/O operation. Otherwise, our caller would
1393 * perform duplicate unbusy and wakeup operations on the page
1394 * and object, respectively.
1395 */
1396 for (j = 0; j < n; j++)
1397 rtvals[i + j] = VM_PAGER_PEND;
1398
1399 /*
1400 * asynchronous
1401 *
1402 * NOTE: b_blkno is destroyed by the call to swapdev_strategy
1403 */
1404 if (sync == FALSE) {
1405 bp->b_iodone = swp_pager_async_iodone;
1406 BUF_KERNPROC(bp);
1407 swp_pager_strategy(bp);
1408 continue;
1409 }
1410
1411 /*
1412 * synchronous
1413 *
1414 * NOTE: b_blkno is destroyed by the call to swapdev_strategy
1415 */
1416 bp->b_iodone = bdone;
1417 swp_pager_strategy(bp);
1418
1419 /*
1420 * Wait for the sync I/O to complete.
1421 */
1422 bwait(bp, PVM, "swwrt");
1423
1424 /*
1425 * Now that we are through with the bp, we can call the
1426 * normal async completion, which frees everything up.
1427 */
1428 swp_pager_async_iodone(bp);
1429 }
1430 VM_OBJECT_WLOCK(object);
1431 }
1432
1433 /*
1434 * swp_pager_async_iodone:
1435 *
1436 * Completion routine for asynchronous reads and writes from/to swap.
1437 * Also called manually by synchronous code to finish up a bp.
1438 *
1439 * This routine may not sleep.
1440 */
1441 static void
1442 swp_pager_async_iodone(struct buf *bp)
1443 {
1444 int i;
1445 vm_object_t object = NULL;
1446
1447 /*
1448 * report error
1449 */
1450 if (bp->b_ioflags & BIO_ERROR) {
1451 printf(
1452 "swap_pager: I/O error - %s failed; blkno %ld,"
1453 "size %ld, error %d\n",
1454 ((bp->b_iocmd == BIO_READ) ? "pagein" : "pageout"),
1455 (long)bp->b_blkno,
1456 (long)bp->b_bcount,
1457 bp->b_error
1458 );
1459 }
1460
1461 /*
1462 * remove the mapping for kernel virtual
1463 */
1464 if (buf_mapped(bp))
1465 pmap_qremove((vm_offset_t)bp->b_data, bp->b_npages);
1466 else
1467 bp->b_data = bp->b_kvabase;
1468
1469 if (bp->b_npages) {
1470 object = bp->b_pages[0]->object;
1471 VM_OBJECT_WLOCK(object);
1472 }
1473
1474 /*
1475 * cleanup pages. If an error occurs writing to swap, we are in
1476 * very serious trouble. If it happens to be a disk error, though,
1477 * we may be able to recover by reassigning the swap later on. So
1478 * in this case we remove the m->swapblk assignment for the page
1479 * but do not free it in the rlist. The errornous block(s) are thus
1480 * never reallocated as swap. Redirty the page and continue.
1481 */
1482 for (i = 0; i < bp->b_npages; ++i) {
1483 vm_page_t m = bp->b_pages[i];
1484
1485 m->oflags &= ~VPO_SWAPINPROG;
1486 if (m->oflags & VPO_SWAPSLEEP) {
1487 m->oflags &= ~VPO_SWAPSLEEP;
1488 wakeup(&object->paging_in_progress);
1489 }
1490
1491 if (bp->b_ioflags & BIO_ERROR) {
1492 /*
1493 * If an error occurs I'd love to throw the swapblk
1494 * away without freeing it back to swapspace, so it
1495 * can never be used again. But I can't from an
1496 * interrupt.
1497 */
1498 if (bp->b_iocmd == BIO_READ) {
1499 /*
1500 * NOTE: for reads, m->dirty will probably
1501 * be overridden by the original caller of
1502 * getpages so don't play cute tricks here.
1503 */
1504 m->valid = 0;
1505 } else {
1506 /*
1507 * If a write error occurs, reactivate page
1508 * so it doesn't clog the inactive list,
1509 * then finish the I/O.
1510 */
1511 vm_page_dirty(m);
1512 vm_page_lock(m);
1513 vm_page_activate(m);
1514 vm_page_unlock(m);
1515 vm_page_sunbusy(m);
1516 }
1517 } else if (bp->b_iocmd == BIO_READ) {
1518 /*
1519 * NOTE: for reads, m->dirty will probably be
1520 * overridden by the original caller of getpages so
1521 * we cannot set them in order to free the underlying
1522 * swap in a low-swap situation. I don't think we'd
1523 * want to do that anyway, but it was an optimization
1524 * that existed in the old swapper for a time before
1525 * it got ripped out due to precisely this problem.
1526 */
1527 KASSERT(!pmap_page_is_mapped(m),
1528 ("swp_pager_async_iodone: page %p is mapped", m));
1529 KASSERT(m->dirty == 0,
1530 ("swp_pager_async_iodone: page %p is dirty", m));
1531
1532 m->valid = VM_PAGE_BITS_ALL;
1533 if (i < bp->b_pgbefore ||
1534 i >= bp->b_npages - bp->b_pgafter)
1535 vm_page_readahead_finish(m);
1536 } else {
1537 /*
1538 * For write success, clear the dirty
1539 * status, then finish the I/O ( which decrements the
1540 * busy count and possibly wakes waiter's up ).
1541 * A page is only written to swap after a period of
1542 * inactivity. Therefore, we do not expect it to be
1543 * reused.
1544 */
1545 KASSERT(!pmap_page_is_write_mapped(m),
1546 ("swp_pager_async_iodone: page %p is not write"
1547 " protected", m));
1548 vm_page_undirty(m);
1549 vm_page_lock(m);
1550 vm_page_deactivate_noreuse(m);
1551 vm_page_unlock(m);
1552 vm_page_sunbusy(m);
1553 }
1554 }
1555
1556 /*
1557 * adjust pip. NOTE: the original parent may still have its own
1558 * pip refs on the object.
1559 */
1560 if (object != NULL) {
1561 vm_object_pip_wakeupn(object, bp->b_npages);
1562 VM_OBJECT_WUNLOCK(object);
1563 }
1564
1565 /*
1566 * swapdev_strategy() manually sets b_vp and b_bufobj before calling
1567 * bstrategy(). Set them back to NULL now we're done with it, or we'll
1568 * trigger a KASSERT in relpbuf().
1569 */
1570 if (bp->b_vp) {
1571 bp->b_vp = NULL;
1572 bp->b_bufobj = NULL;
1573 }
1574 /*
1575 * release the physical I/O buffer
1576 */
1577 relpbuf(
1578 bp,
1579 ((bp->b_iocmd == BIO_READ) ? &nsw_rcount :
1580 ((bp->b_flags & B_ASYNC) ?
1581 &nsw_wcount_async :
1582 &nsw_wcount_sync
1583 )
1584 )
1585 );
1586 }
1587
1588 /*
1589 * swap_pager_isswapped:
1590 *
1591 * Return 1 if at least one page in the given object is paged
1592 * out to the given swap device.
1593 *
1594 * This routine may not sleep.
1595 */
1596 int
1597 swap_pager_isswapped(vm_object_t object, struct swdevt *sp)
1598 {
1599 daddr_t index = 0;
1600 int bcount;
1601 int i;
1602
1603 VM_OBJECT_ASSERT_WLOCKED(object);
1604 if (object->type != OBJT_SWAP)
1605 return (0);
1606
1607 mtx_lock(&swhash_mtx);
1608 for (bcount = 0; bcount < object->un_pager.swp.swp_bcount; bcount++) {
1609 struct swblock *swap;
1610
1611 if ((swap = *swp_pager_hash(object, index)) != NULL) {
1612 for (i = 0; i < SWAP_META_PAGES; ++i) {
1613 if (swp_pager_isondev(swap->swb_pages[i], sp)) {
1614 mtx_unlock(&swhash_mtx);
1615 return (1);
1616 }
1617 }
1618 }
1619 index += SWAP_META_PAGES;
1620 }
1621 mtx_unlock(&swhash_mtx);
1622 return (0);
1623 }
1624
1625 /*
1626 * SWP_PAGER_FORCE_PAGEIN() - force a swap block to be paged in
1627 *
1628 * This routine dissociates the page at the given index within an object
1629 * from its backing store, paging it in if it does not reside in memory.
1630 * If the page is paged in, it is marked dirty and placed in the laundry
1631 * queue. The page is marked dirty because it no longer has backing
1632 * store. It is placed in the laundry queue because it has not been
1633 * accessed recently. Otherwise, it would already reside in memory.
1634 *
1635 * We also attempt to swap in all other pages in the swap block.
1636 * However, we only guarantee that the one at the specified index is
1637 * paged in.
1638 *
1639 * XXX - The code to page the whole block in doesn't work, so we
1640 * revert to the one-by-one behavior for now. Sigh.
1641 */
1642 static inline void
1643 swp_pager_force_pagein(vm_object_t object, vm_pindex_t pindex)
1644 {
1645 vm_page_t m;
1646
1647 vm_object_pip_add(object, 1);
1648 m = vm_page_grab(object, pindex, VM_ALLOC_NORMAL);
1649 if (m->valid == VM_PAGE_BITS_ALL) {
1650 vm_object_pip_wakeup(object);
1651 vm_page_dirty(m);
1652 vm_page_lock(m);
1653 vm_page_activate(m);
1654 vm_page_unlock(m);
1655 vm_page_xunbusy(m);
1656 vm_pager_page_unswapped(m);
1657 return;
1658 }
1659
1660 if (swap_pager_getpages(object, &m, 1, NULL, NULL) != VM_PAGER_OK)
1661 panic("swap_pager_force_pagein: read from swap failed");/*XXX*/
1662 vm_object_pip_wakeup(object);
1663 vm_page_dirty(m);
1664 vm_page_lock(m);
1665 vm_page_launder(m);
1666 vm_page_unlock(m);
1667 vm_page_xunbusy(m);
1668 vm_pager_page_unswapped(m);
1669 }
1670
1671 /*
1672 * swap_pager_swapoff:
1673 *
1674 * Page in all of the pages that have been paged out to the
1675 * given device. The corresponding blocks in the bitmap must be
1676 * marked as allocated and the device must be flagged SW_CLOSING.
1677 * There may be no processes swapped out to the device.
1678 *
1679 * This routine may block.
1680 */
1681 static void
1682 swap_pager_swapoff(struct swdevt *sp)
1683 {
1684 struct swblock *swap;
1685 vm_object_t locked_obj, object;
1686 vm_pindex_t pindex;
1687 int i, j, retries;
1688
1689 sx_assert(&swdev_syscall_lock, SA_XLOCKED);
1690
1691 retries = 0;
1692 locked_obj = NULL;
1693 full_rescan:
1694 mtx_lock(&swhash_mtx);
1695 for (i = 0; i <= swhash_mask; i++) { /* '<=' is correct here */
1696 restart:
1697 for (swap = swhash[i]; swap != NULL; swap = swap->swb_hnext) {
1698 object = swap->swb_object;
1699 pindex = swap->swb_index;
1700 for (j = 0; j < SWAP_META_PAGES; ++j) {
1701 if (!swp_pager_isondev(swap->swb_pages[j], sp))
1702 continue;
1703 if (locked_obj != object) {
1704 if (locked_obj != NULL)
1705 VM_OBJECT_WUNLOCK(locked_obj);
1706 locked_obj = object;
1707 if (!VM_OBJECT_TRYWLOCK(object)) {
1708 mtx_unlock(&swhash_mtx);
1709 /* Depends on type-stability. */
1710 VM_OBJECT_WLOCK(object);
1711 mtx_lock(&swhash_mtx);
1712 goto restart;
1713 }
1714 }
1715 MPASS(locked_obj == object);
1716 mtx_unlock(&swhash_mtx);
1717 swp_pager_force_pagein(object, pindex + j);
1718 mtx_lock(&swhash_mtx);
1719 goto restart;
1720 }
1721 }
1722 }
1723 mtx_unlock(&swhash_mtx);
1724 if (locked_obj != NULL) {
1725 VM_OBJECT_WUNLOCK(locked_obj);
1726 locked_obj = NULL;
1727 }
1728 if (sp->sw_used) {
1729 /*
1730 * Objects may be locked or paging to the device being
1731 * removed, so we will miss their pages and need to
1732 * make another pass. We have marked this device as
1733 * SW_CLOSING, so the activity should finish soon.
1734 */
1735 retries++;
1736 if (retries > 100) {
1737 panic("swapoff: failed to locate %d swap blocks",
1738 sp->sw_used);
1739 }
1740 pause("swpoff", hz / 20);
1741 goto full_rescan;
1742 }
1743 }
1744
1745 /************************************************************************
1746 * SWAP META DATA *
1747 ************************************************************************
1748 *
1749 * These routines manipulate the swap metadata stored in the
1750 * OBJT_SWAP object.
1751 *
1752 * Swap metadata is implemented with a global hash and not directly
1753 * linked into the object. Instead the object simply contains
1754 * appropriate tracking counters.
1755 */
1756
1757 /*
1758 * SWP_PAGER_META_BUILD() - add swap block to swap meta data for object
1759 *
1760 * We first convert the object to a swap object if it is a default
1761 * object.
1762 *
1763 * The specified swapblk is added to the object's swap metadata. If
1764 * the swapblk is not valid, it is freed instead. Any previously
1765 * assigned swapblk is freed.
1766 */
1767 static void
1768 swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk)
1769 {
1770 static volatile int exhausted;
1771 struct swblock *swap;
1772 struct swblock **pswap;
1773 int idx;
1774
1775 VM_OBJECT_ASSERT_WLOCKED(object);
1776 /*
1777 * Convert default object to swap object if necessary
1778 */
1779 if (object->type != OBJT_SWAP) {
1780 object->type = OBJT_SWAP;
1781 object->un_pager.swp.swp_bcount = 0;
1782 KASSERT(object->handle == NULL, ("default pager with handle"));
1783 }
1784
1785 /*
1786 * Locate hash entry. If not found create, but if we aren't adding
1787 * anything just return. If we run out of space in the map we wait
1788 * and, since the hash table may have changed, retry.
1789 */
1790 retry:
1791 mtx_lock(&swhash_mtx);
1792 pswap = swp_pager_hash(object, pindex);
1793
1794 if ((swap = *pswap) == NULL) {
1795 int i;
1796
1797 if (swapblk == SWAPBLK_NONE)
1798 goto done;
1799
1800 swap = *pswap = uma_zalloc(swap_zone, M_NOWAIT |
1801 (curproc == pageproc ? M_USE_RESERVE : 0));
1802 if (swap == NULL) {
1803 mtx_unlock(&swhash_mtx);
1804 VM_OBJECT_WUNLOCK(object);
1805 if (uma_zone_exhausted(swap_zone)) {
1806 if (atomic_cmpset_int(&exhausted, 0, 1))
1807 printf("swap zone exhausted, "
1808 "increase kern.maxswzone\n");
1809 vm_pageout_oom(VM_OOM_SWAPZ);
1810 pause("swzonex", 10);
1811 } else
1812 VM_WAIT;
1813 VM_OBJECT_WLOCK(object);
1814 goto retry;
1815 }
1816
1817 if (atomic_cmpset_int(&exhausted, 1, 0))
1818 printf("swap zone ok\n");
1819
1820 swap->swb_hnext = NULL;
1821 swap->swb_object = object;
1822 swap->swb_index = pindex & ~(vm_pindex_t)SWAP_META_MASK;
1823 swap->swb_count = 0;
1824
1825 ++object->un_pager.swp.swp_bcount;
1826
1827 for (i = 0; i < SWAP_META_PAGES; ++i)
1828 swap->swb_pages[i] = SWAPBLK_NONE;
1829 }
1830
1831 /*
1832 * Delete prior contents of metadata
1833 */
1834 idx = pindex & SWAP_META_MASK;
1835
1836 if (swap->swb_pages[idx] != SWAPBLK_NONE) {
1837 swp_pager_freeswapspace(swap->swb_pages[idx], 1);
1838 --swap->swb_count;
1839 }
1840
1841 /*
1842 * Enter block into metadata
1843 */
1844 swap->swb_pages[idx] = swapblk;
1845 if (swapblk != SWAPBLK_NONE)
1846 ++swap->swb_count;
1847 done:
1848 mtx_unlock(&swhash_mtx);
1849 }
1850
1851 /*
1852 * SWP_PAGER_META_FREE() - free a range of blocks in the object's swap metadata
1853 *
1854 * The requested range of blocks is freed, with any associated swap
1855 * returned to the swap bitmap.
1856 *
1857 * This routine will free swap metadata structures as they are cleaned
1858 * out. This routine does *NOT* operate on swap metadata associated
1859 * with resident pages.
1860 */
1861 static void
1862 swp_pager_meta_free(vm_object_t object, vm_pindex_t index, vm_pindex_t count)
1863 {
1864 struct swblock **pswap, *swap;
1865 vm_pindex_t c;
1866 daddr_t v;
1867 int n, sidx;
1868
1869 VM_OBJECT_ASSERT_LOCKED(object);
1870 if (object->type != OBJT_SWAP || count == 0)
1871 return;
1872
1873 mtx_lock(&swhash_mtx);
1874 for (c = 0; c < count;) {
1875 pswap = swp_pager_hash(object, index);
1876 sidx = index & SWAP_META_MASK;
1877 n = SWAP_META_PAGES - sidx;
1878 index += n;
1879 if ((swap = *pswap) == NULL) {
1880 c += n;
1881 continue;
1882 }
1883 for (; c < count && sidx < SWAP_META_PAGES; ++c, ++sidx) {
1884 if ((v = swap->swb_pages[sidx]) == SWAPBLK_NONE)
1885 continue;
1886 swp_pager_freeswapspace(v, 1);
1887 swap->swb_pages[sidx] = SWAPBLK_NONE;
1888 if (--swap->swb_count == 0) {
1889 *pswap = swap->swb_hnext;
1890 uma_zfree(swap_zone, swap);
1891 --object->un_pager.swp.swp_bcount;
1892 c += SWAP_META_PAGES - sidx;
1893 break;
1894 }
1895 }
1896 }
1897 mtx_unlock(&swhash_mtx);
1898 }
1899
1900 /*
1901 * SWP_PAGER_META_FREE_ALL() - destroy all swap metadata associated with object
1902 *
1903 * This routine locates and destroys all swap metadata associated with
1904 * an object.
1905 */
1906 static void
1907 swp_pager_meta_free_all(vm_object_t object)
1908 {
1909 struct swblock **pswap, *swap;
1910 vm_pindex_t index;
1911 daddr_t v;
1912 int i;
1913
1914 VM_OBJECT_ASSERT_WLOCKED(object);
1915 if (object->type != OBJT_SWAP)
1916 return;
1917
1918 index = 0;
1919 while (object->un_pager.swp.swp_bcount != 0) {
1920 mtx_lock(&swhash_mtx);
1921 pswap = swp_pager_hash(object, index);
1922 if ((swap = *pswap) != NULL) {
1923 for (i = 0; i < SWAP_META_PAGES; ++i) {
1924 v = swap->swb_pages[i];
1925 if (v != SWAPBLK_NONE) {
1926 --swap->swb_count;
1927 swp_pager_freeswapspace(v, 1);
1928 }
1929 }
1930 if (swap->swb_count != 0)
1931 panic(
1932 "swap_pager_meta_free_all: swb_count != 0");
1933 *pswap = swap->swb_hnext;
1934 uma_zfree(swap_zone, swap);
1935 --object->un_pager.swp.swp_bcount;
1936 }
1937 mtx_unlock(&swhash_mtx);
1938 index += SWAP_META_PAGES;
1939 }
1940 }
1941
1942 /*
1943 * SWP_PAGER_METACTL() - misc control of swap and vm_page_t meta data.
1944 *
1945 * This routine is capable of looking up, popping, or freeing
1946 * swapblk assignments in the swap meta data or in the vm_page_t.
1947 * The routine typically returns the swapblk being looked-up, or popped,
1948 * or SWAPBLK_NONE if the block was freed, or SWAPBLK_NONE if the block
1949 * was invalid. This routine will automatically free any invalid
1950 * meta-data swapblks.
1951 *
1952 * It is not possible to store invalid swapblks in the swap meta data
1953 * (other then a literal 'SWAPBLK_NONE'), so we don't bother checking.
1954 *
1955 * When acting on a busy resident page and paging is in progress, we
1956 * have to wait until paging is complete but otherwise can act on the
1957 * busy page.
1958 *
1959 * SWM_FREE remove and free swap block from metadata
1960 * SWM_POP remove from meta data but do not free.. pop it out
1961 */
1962 static daddr_t
1963 swp_pager_meta_ctl(vm_object_t object, vm_pindex_t pindex, int flags)
1964 {
1965 struct swblock **pswap;
1966 struct swblock *swap;
1967 daddr_t r1;
1968 int idx;
1969
1970 VM_OBJECT_ASSERT_LOCKED(object);
1971 /*
1972 * The meta data only exists of the object is OBJT_SWAP
1973 * and even then might not be allocated yet.
1974 */
1975 if (object->type != OBJT_SWAP)
1976 return (SWAPBLK_NONE);
1977
1978 r1 = SWAPBLK_NONE;
1979 mtx_lock(&swhash_mtx);
1980 pswap = swp_pager_hash(object, pindex);
1981
1982 if ((swap = *pswap) != NULL) {
1983 idx = pindex & SWAP_META_MASK;
1984 r1 = swap->swb_pages[idx];
1985
1986 if (r1 != SWAPBLK_NONE) {
1987 if (flags & SWM_FREE) {
1988 swp_pager_freeswapspace(r1, 1);
1989 r1 = SWAPBLK_NONE;
1990 }
1991 if (flags & (SWM_FREE|SWM_POP)) {
1992 swap->swb_pages[idx] = SWAPBLK_NONE;
1993 if (--swap->swb_count == 0) {
1994 *pswap = swap->swb_hnext;
1995 uma_zfree(swap_zone, swap);
1996 --object->un_pager.swp.swp_bcount;
1997 }
1998 }
1999 }
2000 }
2001 mtx_unlock(&swhash_mtx);
2002 return (r1);
2003 }
2004
2005 /*
2006 * Returns the least page index which is greater than or equal to the
2007 * parameter pindex and for which there is a swap block allocated.
2008 * Returns object's size if the object's type is not swap or if there
2009 * are no allocated swap blocks for the object after the requested
2010 * pindex.
2011 */
2012 vm_pindex_t
2013 swap_pager_find_least(vm_object_t object, vm_pindex_t pindex)
2014 {
2015 struct swblock **pswap, *swap;
2016 vm_pindex_t i, j, lim;
2017 int idx;
2018
2019 VM_OBJECT_ASSERT_LOCKED(object);
2020 if (object->type != OBJT_SWAP || object->un_pager.swp.swp_bcount == 0)
2021 return (object->size);
2022
2023 mtx_lock(&swhash_mtx);
2024 for (j = pindex; j < object->size; j = lim) {
2025 pswap = swp_pager_hash(object, j);
2026 lim = rounddown2(j + SWAP_META_PAGES, SWAP_META_PAGES);
2027 if (lim > object->size)
2028 lim = object->size;
2029 if ((swap = *pswap) != NULL) {
2030 for (idx = j & SWAP_META_MASK, i = j; i < lim;
2031 i++, idx++) {
2032 if (swap->swb_pages[idx] != SWAPBLK_NONE)
2033 goto found;
2034 }
2035 }
2036 }
2037 i = object->size;
2038 found:
2039 mtx_unlock(&swhash_mtx);
2040 return (i);
2041 }
2042
2043 /*
2044 * System call swapon(name) enables swapping on device name,
2045 * which must be in the swdevsw. Return EBUSY
2046 * if already swapping on this device.
2047 */
2048 #ifndef _SYS_SYSPROTO_H_
2049 struct swapon_args {
2050 char *name;
2051 };
2052 #endif
2053
2054 /*
2055 * MPSAFE
2056 */
2057 /* ARGSUSED */
2058 int
2059 sys_swapon(struct thread *td, struct swapon_args *uap)
2060 {
2061 struct vattr attr;
2062 struct vnode *vp;
2063 struct nameidata nd;
2064 int error;
2065
2066 error = priv_check(td, PRIV_SWAPON);
2067 if (error)
2068 return (error);
2069
2070 sx_xlock(&swdev_syscall_lock);
2071
2072 /*
2073 * Swap metadata may not fit in the KVM if we have physical
2074 * memory of >1GB.
2075 */
2076 if (swap_zone == NULL) {
2077 error = ENOMEM;
2078 goto done;
2079 }
2080
2081 NDINIT(&nd, LOOKUP, ISOPEN | FOLLOW | AUDITVNODE1, UIO_USERSPACE,
2082 uap->name, td);
2083 error = namei(&nd);
2084 if (error)
2085 goto done;
2086
2087 NDFREE(&nd, NDF_ONLY_PNBUF);
2088 vp = nd.ni_vp;
2089
2090 if (vn_isdisk(vp, &error)) {
2091 error = swapongeom(vp);
2092 } else if (vp->v_type == VREG &&
2093 (vp->v_mount->mnt_vfc->vfc_flags & VFCF_NETWORK) != 0 &&
2094 (error = VOP_GETATTR(vp, &attr, td->td_ucred)) == 0) {
2095 /*
2096 * Allow direct swapping to NFS regular files in the same
2097 * way that nfs_mountroot() sets up diskless swapping.
2098 */
2099 error = swaponvp(td, vp, attr.va_size / DEV_BSIZE);
2100 }
2101
2102 if (error)
2103 vrele(vp);
2104 done:
2105 sx_xunlock(&swdev_syscall_lock);
2106 return (error);
2107 }
2108
2109 /*
2110 * Check that the total amount of swap currently configured does not
2111 * exceed half the theoretical maximum. If it does, print a warning
2112 * message and return -1; otherwise, return 0.
2113 */
2114 static int
2115 swapon_check_swzone(unsigned long npages)
2116 {
2117 unsigned long maxpages;
2118
2119 /* absolute maximum we can handle assuming 100% efficiency */
2120 maxpages = uma_zone_get_max(swap_zone) * SWAP_META_PAGES;
2121
2122 /* recommend using no more than half that amount */
2123 if (npages > maxpages / 2) {
2124 printf("warning: total configured swap (%lu pages) "
2125 "exceeds maximum recommended amount (%lu pages).\n",
2126 npages, maxpages / 2);
2127 printf("warning: increase kern.maxswzone "
2128 "or reduce amount of swap.\n");
2129 return (-1);
2130 }
2131 return (0);
2132 }
2133
2134 static void
2135 swaponsomething(struct vnode *vp, void *id, u_long nblks,
2136 sw_strategy_t *strategy, sw_close_t *close, dev_t dev, int flags)
2137 {
2138 struct swdevt *sp, *tsp;
2139 swblk_t dvbase;
2140 u_long mblocks;
2141
2142 /*
2143 * nblks is in DEV_BSIZE'd chunks, convert to PAGE_SIZE'd chunks.
2144 * First chop nblks off to page-align it, then convert.
2145 *
2146 * sw->sw_nblks is in page-sized chunks now too.
2147 */
2148 nblks &= ~(ctodb(1) - 1);
2149 nblks = dbtoc(nblks);
2150
2151 /*
2152 * If we go beyond this, we get overflows in the radix
2153 * tree bitmap code.
2154 */
2155 mblocks = 0x40000000 / BLIST_META_RADIX;
2156 if (nblks > mblocks) {
2157 printf(
2158 "WARNING: reducing swap size to maximum of %luMB per unit\n",
2159 mblocks / 1024 / 1024 * PAGE_SIZE);
2160 nblks = mblocks;
2161 }
2162
2163 sp = malloc(sizeof *sp, M_VMPGDATA, M_WAITOK | M_ZERO);
2164 sp->sw_vp = vp;
2165 sp->sw_id = id;
2166 sp->sw_dev = dev;
2167 sp->sw_flags = 0;
2168 sp->sw_nblks = nblks;
2169 sp->sw_used = 0;
2170 sp->sw_strategy = strategy;
2171 sp->sw_close = close;
2172 sp->sw_flags = flags;
2173
2174 sp->sw_blist = blist_create(nblks, M_WAITOK);
2175 /*
2176 * Do not free the first two block in order to avoid overwriting
2177 * any bsd label at the front of the partition
2178 */
2179 blist_free(sp->sw_blist, 2, nblks - 2);
2180
2181 dvbase = 0;
2182 mtx_lock(&sw_dev_mtx);
2183 TAILQ_FOREACH(tsp, &swtailq, sw_list) {
2184 if (tsp->sw_end >= dvbase) {
2185 /*
2186 * We put one uncovered page between the devices
2187 * in order to definitively prevent any cross-device
2188 * I/O requests
2189 */
2190 dvbase = tsp->sw_end + 1;
2191 }
2192 }
2193 sp->sw_first = dvbase;
2194 sp->sw_end = dvbase + nblks;
2195 TAILQ_INSERT_TAIL(&swtailq, sp, sw_list);
2196 nswapdev++;
2197 swap_pager_avail += nblks - 2;
2198 swap_total += (vm_ooffset_t)nblks * PAGE_SIZE;
2199 swapon_check_swzone(swap_total / PAGE_SIZE);
2200 swp_sizecheck();
2201 mtx_unlock(&sw_dev_mtx);
2202 }
2203
2204 /*
2205 * SYSCALL: swapoff(devname)
2206 *
2207 * Disable swapping on the given device.
2208 *
2209 * XXX: Badly designed system call: it should use a device index
2210 * rather than filename as specification. We keep sw_vp around
2211 * only to make this work.
2212 */
2213 #ifndef _SYS_SYSPROTO_H_
2214 struct swapoff_args {
2215 char *name;
2216 };
2217 #endif
2218
2219 /*
2220 * MPSAFE
2221 */
2222 /* ARGSUSED */
2223 int
2224 sys_swapoff(struct thread *td, struct swapoff_args *uap)
2225 {
2226 struct vnode *vp;
2227 struct nameidata nd;
2228 struct swdevt *sp;
2229 int error;
2230
2231 error = priv_check(td, PRIV_SWAPOFF);
2232 if (error)
2233 return (error);
2234
2235 sx_xlock(&swdev_syscall_lock);
2236
2237 NDINIT(&nd, LOOKUP, FOLLOW | AUDITVNODE1, UIO_USERSPACE, uap->name,
2238 td);
2239 error = namei(&nd);
2240 if (error)
2241 goto done;
2242 NDFREE(&nd, NDF_ONLY_PNBUF);
2243 vp = nd.ni_vp;
2244
2245 mtx_lock(&sw_dev_mtx);
2246 TAILQ_FOREACH(sp, &swtailq, sw_list) {
2247 if (sp->sw_vp == vp)
2248 break;
2249 }
2250 mtx_unlock(&sw_dev_mtx);
2251 if (sp == NULL) {
2252 error = EINVAL;
2253 goto done;
2254 }
2255 error = swapoff_one(sp, td->td_ucred);
2256 done:
2257 sx_xunlock(&swdev_syscall_lock);
2258 return (error);
2259 }
2260
2261 static int
2262 swapoff_one(struct swdevt *sp, struct ucred *cred)
2263 {
2264 u_long nblks;
2265 #ifdef MAC
2266 int error;
2267 #endif
2268
2269 sx_assert(&swdev_syscall_lock, SA_XLOCKED);
2270 #ifdef MAC
2271 (void) vn_lock(sp->sw_vp, LK_EXCLUSIVE | LK_RETRY);
2272 error = mac_system_check_swapoff(cred, sp->sw_vp);
2273 (void) VOP_UNLOCK(sp->sw_vp, 0);
2274 if (error != 0)
2275 return (error);
2276 #endif
2277 nblks = sp->sw_nblks;
2278
2279 /*
2280 * We can turn off this swap device safely only if the
2281 * available virtual memory in the system will fit the amount
2282 * of data we will have to page back in, plus an epsilon so
2283 * the system doesn't become critically low on swap space.
2284 */
2285 if (vm_cnt.v_free_count + swap_pager_avail < nblks + nswap_lowat)
2286 return (ENOMEM);
2287
2288 /*
2289 * Prevent further allocations on this device.
2290 */
2291 mtx_lock(&sw_dev_mtx);
2292 sp->sw_flags |= SW_CLOSING;
2293 swap_pager_avail -= blist_fill(sp->sw_blist, 0, nblks);
2294 swap_total -= (vm_ooffset_t)nblks * PAGE_SIZE;
2295 mtx_unlock(&sw_dev_mtx);
2296
2297 /*
2298 * Page in the contents of the device and close it.
2299 */
2300 swap_pager_swapoff(sp);
2301
2302 sp->sw_close(curthread, sp);
2303 mtx_lock(&sw_dev_mtx);
2304 sp->sw_id = NULL;
2305 TAILQ_REMOVE(&swtailq, sp, sw_list);
2306 nswapdev--;
2307 if (nswapdev == 0) {
2308 swap_pager_full = 2;
2309 swap_pager_almost_full = 1;
2310 }
2311 if (swdevhd == sp)
2312 swdevhd = NULL;
2313 mtx_unlock(&sw_dev_mtx);
2314 blist_destroy(sp->sw_blist);
2315 free(sp, M_VMPGDATA);
2316 return (0);
2317 }
2318
2319 void
2320 swapoff_all(void)
2321 {
2322 struct swdevt *sp, *spt;
2323 const char *devname;
2324 int error;
2325
2326 sx_xlock(&swdev_syscall_lock);
2327
2328 mtx_lock(&sw_dev_mtx);
2329 TAILQ_FOREACH_SAFE(sp, &swtailq, sw_list, spt) {
2330 mtx_unlock(&sw_dev_mtx);
2331 if (vn_isdisk(sp->sw_vp, NULL))
2332 devname = devtoname(sp->sw_vp->v_rdev);
2333 else
2334 devname = "[file]";
2335 error = swapoff_one(sp, thread0.td_ucred);
2336 if (error != 0) {
2337 printf("Cannot remove swap device %s (error=%d), "
2338 "skipping.\n", devname, error);
2339 } else if (bootverbose) {
2340 printf("Swap device %s removed.\n", devname);
2341 }
2342 mtx_lock(&sw_dev_mtx);
2343 }
2344 mtx_unlock(&sw_dev_mtx);
2345
2346 sx_xunlock(&swdev_syscall_lock);
2347 }
2348
2349 void
2350 swap_pager_status(int *total, int *used)
2351 {
2352 struct swdevt *sp;
2353
2354 *total = 0;
2355 *used = 0;
2356 mtx_lock(&sw_dev_mtx);
2357 TAILQ_FOREACH(sp, &swtailq, sw_list) {
2358 *total += sp->sw_nblks;
2359 *used += sp->sw_used;
2360 }
2361 mtx_unlock(&sw_dev_mtx);
2362 }
2363
2364 int
2365 swap_dev_info(int name, struct xswdev *xs, char *devname, size_t len)
2366 {
2367 struct swdevt *sp;
2368 const char *tmp_devname;
2369 int error, n;
2370
2371 n = 0;
2372 error = ENOENT;
2373 mtx_lock(&sw_dev_mtx);
2374 TAILQ_FOREACH(sp, &swtailq, sw_list) {
2375 if (n != name) {
2376 n++;
2377 continue;
2378 }
2379 xs->xsw_version = XSWDEV_VERSION;
2380 xs->xsw_dev = sp->sw_dev;
2381 xs->xsw_flags = sp->sw_flags;
2382 xs->xsw_nblks = sp->sw_nblks;
2383 xs->xsw_used = sp->sw_used;
2384 if (devname != NULL) {
2385 if (vn_isdisk(sp->sw_vp, NULL))
2386 tmp_devname = devtoname(sp->sw_vp->v_rdev);
2387 else
2388 tmp_devname = "[file]";
2389 strncpy(devname, tmp_devname, len);
2390 }
2391 error = 0;
2392 break;
2393 }
2394 mtx_unlock(&sw_dev_mtx);
2395 return (error);
2396 }
2397
2398 static int
2399 sysctl_vm_swap_info(SYSCTL_HANDLER_ARGS)
2400 {
2401 struct xswdev xs;
2402 int error;
2403
2404 if (arg2 != 1) /* name length */
2405 return (EINVAL);
2406 error = swap_dev_info(*(int *)arg1, &xs, NULL, 0);
2407 if (error != 0)
2408 return (error);
2409 error = SYSCTL_OUT(req, &xs, sizeof(xs));
2410 return (error);
2411 }
2412
2413 SYSCTL_INT(_vm, OID_AUTO, nswapdev, CTLFLAG_RD, &nswapdev, 0,
2414 "Number of swap devices");
2415 SYSCTL_NODE(_vm, OID_AUTO, swap_info, CTLFLAG_RD | CTLFLAG_MPSAFE,
2416 sysctl_vm_swap_info,
2417 "Swap statistics by device");
2418
2419 /*
2420 * vmspace_swap_count() - count the approximate swap usage in pages for a
2421 * vmspace.
2422 *
2423 * The map must be locked.
2424 *
2425 * Swap usage is determined by taking the proportional swap used by
2426 * VM objects backing the VM map. To make up for fractional losses,
2427 * if the VM object has any swap use at all the associated map entries
2428 * count for at least 1 swap page.
2429 */
2430 long
2431 vmspace_swap_count(struct vmspace *vmspace)
2432 {
2433 vm_map_t map;
2434 vm_map_entry_t cur;
2435 vm_object_t object;
2436 long count, n;
2437
2438 map = &vmspace->vm_map;
2439 count = 0;
2440
2441 for (cur = map->header.next; cur != &map->header; cur = cur->next) {
2442 if ((cur->eflags & MAP_ENTRY_IS_SUB_MAP) == 0 &&
2443 (object = cur->object.vm_object) != NULL) {
2444 VM_OBJECT_WLOCK(object);
2445 if (object->type == OBJT_SWAP &&
2446 object->un_pager.swp.swp_bcount != 0) {
2447 n = (cur->end - cur->start) / PAGE_SIZE;
2448 count += object->un_pager.swp.swp_bcount *
2449 SWAP_META_PAGES * n / object->size + 1;
2450 }
2451 VM_OBJECT_WUNLOCK(object);
2452 }
2453 }
2454 return (count);
2455 }
2456
2457 /*
2458 * GEOM backend
2459 *
2460 * Swapping onto disk devices.
2461 *
2462 */
2463
2464 static g_orphan_t swapgeom_orphan;
2465
2466 static struct g_class g_swap_class = {
2467 .name = "SWAP",
2468 .version = G_VERSION,
2469 .orphan = swapgeom_orphan,
2470 };
2471
2472 DECLARE_GEOM_CLASS(g_swap_class, g_class);
2473
2474
2475 static void
2476 swapgeom_close_ev(void *arg, int flags)
2477 {
2478 struct g_consumer *cp;
2479
2480 cp = arg;
2481 g_access(cp, -1, -1, 0);
2482 g_detach(cp);
2483 g_destroy_consumer(cp);
2484 }
2485
2486 /*
2487 * Add a reference to the g_consumer for an inflight transaction.
2488 */
2489 static void
2490 swapgeom_acquire(struct g_consumer *cp)
2491 {
2492
2493 mtx_assert(&sw_dev_mtx, MA_OWNED);
2494 cp->index++;
2495 }
2496
2497 /*
2498 * Remove a reference from the g_consumer. Post a close event if all
2499 * references go away, since the function might be called from the
2500 * biodone context.
2501 */
2502 static void
2503 swapgeom_release(struct g_consumer *cp, struct swdevt *sp)
2504 {
2505
2506 mtx_assert(&sw_dev_mtx, MA_OWNED);
2507 cp->index--;
2508 if (cp->index == 0) {
2509 if (g_post_event(swapgeom_close_ev, cp, M_NOWAIT, NULL) == 0)
2510 sp->sw_id = NULL;
2511 }
2512 }
2513
2514 static void
2515 swapgeom_done(struct bio *bp2)
2516 {
2517 struct swdevt *sp;
2518 struct buf *bp;
2519 struct g_consumer *cp;
2520
2521 bp = bp2->bio_caller2;
2522 cp = bp2->bio_from;
2523 bp->b_ioflags = bp2->bio_flags;
2524 if (bp2->bio_error)
2525 bp->b_ioflags |= BIO_ERROR;
2526 bp->b_resid = bp->b_bcount - bp2->bio_completed;
2527 bp->b_error = bp2->bio_error;
2528 bufdone(bp);
2529 sp = bp2->bio_caller1;
2530 mtx_lock(&sw_dev_mtx);
2531 swapgeom_release(cp, sp);
2532 mtx_unlock(&sw_dev_mtx);
2533 g_destroy_bio(bp2);
2534 }
2535
2536 static void
2537 swapgeom_strategy(struct buf *bp, struct swdevt *sp)
2538 {
2539 struct bio *bio;
2540 struct g_consumer *cp;
2541
2542 mtx_lock(&sw_dev_mtx);
2543 cp = sp->sw_id;
2544 if (cp == NULL) {
2545 mtx_unlock(&sw_dev_mtx);
2546 bp->b_error = ENXIO;
2547 bp->b_ioflags |= BIO_ERROR;
2548 bufdone(bp);
2549 return;
2550 }
2551 swapgeom_acquire(cp);
2552 mtx_unlock(&sw_dev_mtx);
2553 if (bp->b_iocmd == BIO_WRITE)
2554 bio = g_new_bio();
2555 else
2556 bio = g_alloc_bio();
2557 if (bio == NULL) {
2558 mtx_lock(&sw_dev_mtx);
2559 swapgeom_release(cp, sp);
2560 mtx_unlock(&sw_dev_mtx);
2561 bp->b_error = ENOMEM;
2562 bp->b_ioflags |= BIO_ERROR;
2563 bufdone(bp);
2564 return;
2565 }
2566
2567 bio->bio_caller1 = sp;
2568 bio->bio_caller2 = bp;
2569 bio->bio_cmd = bp->b_iocmd;
2570 bio->bio_offset = (bp->b_blkno - sp->sw_first) * PAGE_SIZE;
2571 bio->bio_length = bp->b_bcount;
2572 bio->bio_done = swapgeom_done;
2573 if (!buf_mapped(bp)) {
2574 bio->bio_ma = bp->b_pages;
2575 bio->bio_data = unmapped_buf;
2576 bio->bio_ma_offset = (vm_offset_t)bp->b_offset & PAGE_MASK;
2577 bio->bio_ma_n = bp->b_npages;
2578 bio->bio_flags |= BIO_UNMAPPED;
2579 } else {
2580 bio->bio_data = bp->b_data;
2581 bio->bio_ma = NULL;
2582 }
2583 g_io_request(bio, cp);
2584 return;
2585 }
2586
2587 static void
2588 swapgeom_orphan(struct g_consumer *cp)
2589 {
2590 struct swdevt *sp;
2591 int destroy;
2592
2593 mtx_lock(&sw_dev_mtx);
2594 TAILQ_FOREACH(sp, &swtailq, sw_list) {
2595 if (sp->sw_id == cp) {
2596 sp->sw_flags |= SW_CLOSING;
2597 break;
2598 }
2599 }
2600 /*
2601 * Drop reference we were created with. Do directly since we're in a
2602 * special context where we don't have to queue the call to
2603 * swapgeom_close_ev().
2604 */
2605 cp->index--;
2606 destroy = ((sp != NULL) && (cp->index == 0));
2607 if (destroy)
2608 sp->sw_id = NULL;
2609 mtx_unlock(&sw_dev_mtx);
2610 if (destroy)
2611 swapgeom_close_ev(cp, 0);
2612 }
2613
2614 static void
2615 swapgeom_close(struct thread *td, struct swdevt *sw)
2616 {
2617 struct g_consumer *cp;
2618
2619 mtx_lock(&sw_dev_mtx);
2620 cp = sw->sw_id;
2621 sw->sw_id = NULL;
2622 mtx_unlock(&sw_dev_mtx);
2623
2624 /*
2625 * swapgeom_close() may be called from the biodone context,
2626 * where we cannot perform topology changes. Delegate the
2627 * work to the events thread.
2628 */
2629 if (cp != NULL)
2630 g_waitfor_event(swapgeom_close_ev, cp, M_WAITOK, NULL);
2631 }
2632
2633 static int
2634 swapongeom_locked(struct cdev *dev, struct vnode *vp)
2635 {
2636 struct g_provider *pp;
2637 struct g_consumer *cp;
2638 static struct g_geom *gp;
2639 struct swdevt *sp;
2640 u_long nblks;
2641 int error;
2642
2643 pp = g_dev_getprovider(dev);
2644 if (pp == NULL)
2645 return (ENODEV);
2646 mtx_lock(&sw_dev_mtx);
2647 TAILQ_FOREACH(sp, &swtailq, sw_list) {
2648 cp = sp->sw_id;
2649 if (cp != NULL && cp->provider == pp) {
2650 mtx_unlock(&sw_dev_mtx);
2651 return (EBUSY);
2652 }
2653 }
2654 mtx_unlock(&sw_dev_mtx);
2655 if (gp == NULL)
2656 gp = g_new_geomf(&g_swap_class, "swap");
2657 cp = g_new_consumer(gp);
2658 cp->index = 1; /* Number of active I/Os, plus one for being active. */
2659 cp->flags |= G_CF_DIRECT_SEND | G_CF_DIRECT_RECEIVE;
2660 g_attach(cp, pp);
2661 /*
2662 * XXX: Every time you think you can improve the margin for
2663 * footshooting, somebody depends on the ability to do so:
2664 * savecore(8) wants to write to our swapdev so we cannot
2665 * set an exclusive count :-(
2666 */
2667 error = g_access(cp, 1, 1, 0);
2668 if (error != 0) {
2669 g_detach(cp);
2670 g_destroy_consumer(cp);
2671 return (error);
2672 }
2673 nblks = pp->mediasize / DEV_BSIZE;
2674 swaponsomething(vp, cp, nblks, swapgeom_strategy,
2675 swapgeom_close, dev2udev(dev),
2676 (pp->flags & G_PF_ACCEPT_UNMAPPED) != 0 ? SW_UNMAPPED : 0);
2677 return (0);
2678 }
2679
2680 static int
2681 swapongeom(struct vnode *vp)
2682 {
2683 int error;
2684
2685 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
2686 if (vp->v_type != VCHR || (vp->v_iflag & VI_DOOMED) != 0) {
2687 error = ENOENT;
2688 } else {
2689 g_topology_lock();
2690 error = swapongeom_locked(vp->v_rdev, vp);
2691 g_topology_unlock();
2692 }
2693 VOP_UNLOCK(vp, 0);
2694 return (error);
2695 }
2696
2697 /*
2698 * VNODE backend
2699 *
2700 * This is used mainly for network filesystem (read: probably only tested
2701 * with NFS) swapfiles.
2702 *
2703 */
2704
2705 static void
2706 swapdev_strategy(struct buf *bp, struct swdevt *sp)
2707 {
2708 struct vnode *vp2;
2709
2710 bp->b_blkno = ctodb(bp->b_blkno - sp->sw_first);
2711
2712 vp2 = sp->sw_id;
2713 vhold(vp2);
2714 if (bp->b_iocmd == BIO_WRITE) {
2715 if (bp->b_bufobj)
2716 bufobj_wdrop(bp->b_bufobj);
2717 bufobj_wref(&vp2->v_bufobj);
2718 }
2719 if (bp->b_bufobj != &vp2->v_bufobj)
2720 bp->b_bufobj = &vp2->v_bufobj;
2721 bp->b_vp = vp2;
2722 bp->b_iooffset = dbtob(bp->b_blkno);
2723 bstrategy(bp);
2724 return;
2725 }
2726
2727 static void
2728 swapdev_close(struct thread *td, struct swdevt *sp)
2729 {
2730
2731 VOP_CLOSE(sp->sw_vp, FREAD | FWRITE, td->td_ucred, td);
2732 vrele(sp->sw_vp);
2733 }
2734
2735
2736 static int
2737 swaponvp(struct thread *td, struct vnode *vp, u_long nblks)
2738 {
2739 struct swdevt *sp;
2740 int error;
2741
2742 if (nblks == 0)
2743 return (ENXIO);
2744 mtx_lock(&sw_dev_mtx);
2745 TAILQ_FOREACH(sp, &swtailq, sw_list) {
2746 if (sp->sw_id == vp) {
2747 mtx_unlock(&sw_dev_mtx);
2748 return (EBUSY);
2749 }
2750 }
2751 mtx_unlock(&sw_dev_mtx);
2752
2753 (void) vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
2754 #ifdef MAC
2755 error = mac_system_check_swapon(td->td_ucred, vp);
2756 if (error == 0)
2757 #endif
2758 error = VOP_OPEN(vp, FREAD | FWRITE, td->td_ucred, td, NULL);
2759 (void) VOP_UNLOCK(vp, 0);
2760 if (error)
2761 return (error);
2762
2763 swaponsomething(vp, vp, nblks, swapdev_strategy, swapdev_close,
2764 NODEV, 0);
2765 return (0);
2766 }
2767
2768 static int
2769 sysctl_swap_async_max(SYSCTL_HANDLER_ARGS)
2770 {
2771 int error, new, n;
2772
2773 new = nsw_wcount_async_max;
2774 error = sysctl_handle_int(oidp, &new, 0, req);
2775 if (error != 0 || req->newptr == NULL)
2776 return (error);
2777
2778 if (new > nswbuf / 2 || new < 1)
2779 return (EINVAL);
2780
2781 mtx_lock(&pbuf_mtx);
2782 while (nsw_wcount_async_max != new) {
2783 /*
2784 * Adjust difference. If the current async count is too low,
2785 * we will need to sqeeze our update slowly in. Sleep with a
2786 * higher priority than getpbuf() to finish faster.
2787 */
2788 n = new - nsw_wcount_async_max;
2789 if (nsw_wcount_async + n >= 0) {
2790 nsw_wcount_async += n;
2791 nsw_wcount_async_max += n;
2792 wakeup(&nsw_wcount_async);
2793 } else {
2794 nsw_wcount_async_max -= nsw_wcount_async;
2795 nsw_wcount_async = 0;
2796 msleep(&nsw_wcount_async, &pbuf_mtx, PSWP,
2797 "swpsysctl", 0);
2798 }
2799 }
2800 mtx_unlock(&pbuf_mtx);
2801
2802 return (0);
2803 }
Cache object: 7cfdb7ef44bd9654310d4670508771dc
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