-
Notifications
You must be signed in to change notification settings - Fork 24
/
uvm_loan.c
1184 lines (1024 loc) · 28.7 KB
/
uvm_loan.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/* $NetBSD: uvm_loan.c,v 1.72 2008/06/17 02:29:10 yamt Exp $ */
/*
*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Charles D. Cranor and
* Washington University.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* from: Id: uvm_loan.c,v 1.1.6.4 1998/02/06 05:08:43 chs Exp
*/
/*
* uvm_loan.c: page loanout handler
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_loan.c,v 1.72 2008/06/17 02:29:10 yamt Exp $");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <uvm/uvm.h>
/*
* "loaned" pages are pages which are (read-only, copy-on-write) loaned
* from the VM system to other parts of the kernel. this allows page
* copying to be avoided (e.g. you can loan pages from objs/anons to
* the mbuf system).
*
* there are 3 types of loans possible:
* O->K uvm_object page to wired kernel page (e.g. mbuf data area)
* A->K anon page to wired kernel page (e.g. mbuf data area)
* O->A uvm_object to anon loan (e.g. vnode page to an anon)
* note that it possible to have an O page loaned to both an A and K
* at the same time.
*
* loans are tracked by pg->loan_count. an O->A page will have both
* a uvm_object and a vm_anon, but PQ_ANON will not be set. this sort
* of page is considered "owned" by the uvm_object (not the anon).
*
* each loan of a page to the kernel bumps the pg->wire_count. the
* kernel mappings for these pages will be read-only and wired. since
* the page will also be wired, it will not be a candidate for pageout,
* and thus will never be pmap_page_protect()'d with VM_PROT_NONE. a
* write fault in the kernel to one of these pages will not cause
* copy-on-write. instead, the page fault is considered fatal. this
* is because the kernel mapping will have no way to look up the
* object/anon which the page is owned by. this is a good side-effect,
* since a kernel write to a loaned page is an error.
*
* owners that want to free their pages and discover that they are
* loaned out simply "disown" them (the page becomes an orphan). these
* pages should be freed when the last loan is dropped. in some cases
* an anon may "adopt" an orphaned page.
*
* locking: to read pg->loan_count either the owner or the page queues
* must be locked. to modify pg->loan_count, both the owner of the page
* and the PQs must be locked. pg->flags is (as always) locked by
* the owner of the page.
*
* note that locking from the "loaned" side is tricky since the object
* getting the loaned page has no reference to the page's owner and thus
* the owner could "die" at any time. in order to prevent the owner
* from dying the page queues should be locked. this forces us to sometimes
* use "try" locking.
*
* loans are typically broken by the following events:
* 1. user-level xwrite fault to a loaned page
* 2. pageout of clean+inactive O->A loaned page
* 3. owner frees page (e.g. pager flush)
*
* note that loaning a page causes all mappings of the page to become
* read-only (via pmap_page_protect). this could have an unexpected
* effect on normal "wired" pages if one is not careful (XXX).
*/
/*
* local prototypes
*/
static int uvm_loananon(struct uvm_faultinfo *, void ***,
int, struct vm_anon *);
static int uvm_loanuobj(struct uvm_faultinfo *, void ***,
int, vaddr_t);
static int uvm_loanzero(struct uvm_faultinfo *, void ***, int);
static void uvm_unloananon(struct vm_anon **, int);
static void uvm_unloanpage(struct vm_page **, int);
static int uvm_loanpage(struct vm_page **, int);
/*
* inlines
*/
/*
* uvm_loanentry: loan out pages in a map entry (helper fn for uvm_loan())
*
* => "ufi" is the result of a successful map lookup (meaning that
* on entry the map is locked by the caller)
* => we may unlock and then relock the map if needed (for I/O)
* => we put our output result in "output"
* => we always return with the map unlocked
* => possible return values:
* -1 == error, map is unlocked
* 0 == map relock error (try again!), map is unlocked
* >0 == number of pages we loaned, map is unlocked
*
* NOTE: We can live with this being an inline, because it is only called
* from one place.
*/
static inline int
uvm_loanentry(struct uvm_faultinfo *ufi, void ***output, int flags)
{
vaddr_t curaddr = ufi->orig_rvaddr;
vsize_t togo = ufi->size;
struct vm_aref *aref = &ufi->entry->aref;
struct uvm_object *uobj = ufi->entry->object.uvm_obj;
struct vm_anon *anon;
int rv, result = 0;
UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist);
/*
* lock us the rest of the way down (we unlock before return)
*/
if (aref->ar_amap)
amap_lock(aref->ar_amap);
/*
* loop until done
*/
while (togo) {
/*
* find the page we want. check the anon layer first.
*/
if (aref->ar_amap) {
anon = amap_lookup(aref, curaddr - ufi->entry->start);
} else {
anon = NULL;
}
/* locked: map, amap, uobj */
if (anon) {
rv = uvm_loananon(ufi, output, flags, anon);
} else if (uobj) {
rv = uvm_loanuobj(ufi, output, flags, curaddr);
} else if (UVM_ET_ISCOPYONWRITE(ufi->entry)) {
rv = uvm_loanzero(ufi, output, flags);
} else {
uvmfault_unlockall(ufi, aref->ar_amap, uobj, NULL);
rv = -1;
}
/* locked: if (rv > 0) => map, amap, uobj [o.w. unlocked] */
KASSERT(rv > 0 || aref->ar_amap == NULL ||
!mutex_owned(&aref->ar_amap->am_l));
KASSERT(rv > 0 || uobj == NULL ||
!mutex_owned(&uobj->vmobjlock));
/* total failure */
if (rv < 0) {
UVMHIST_LOG(loanhist, "failure %d", rv, 0,0,0);
return (-1);
}
/* relock failed, need to do another lookup */
if (rv == 0) {
UVMHIST_LOG(loanhist, "relock failure %d", result
,0,0,0);
return (result);
}
/*
* got it... advance to next page
*/
result++;
togo -= PAGE_SIZE;
curaddr += PAGE_SIZE;
}
/*
* unlock what we locked, unlock the maps and return
*/
if (aref->ar_amap)
amap_unlock(aref->ar_amap);
uvmfault_unlockmaps(ufi, false);
UVMHIST_LOG(loanhist, "done %d", result, 0,0,0);
return (result);
}
/*
* normal functions
*/
/*
* uvm_loan: loan pages in a map out to anons or to the kernel
*
* => map should be unlocked
* => start and len should be multiples of PAGE_SIZE
* => result is either an array of anon's or vm_pages (depending on flags)
* => flag values: UVM_LOAN_TOANON - loan to anons
* UVM_LOAN_TOPAGE - loan to wired kernel page
* one and only one of these flags must be set!
* => returns 0 (success), or an appropriate error number
*/
int
uvm_loan(struct vm_map *map, vaddr_t start, vsize_t len, void *v, int flags)
{
struct uvm_faultinfo ufi;
void **result, **output;
int rv, error;
UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist);
/*
* ensure that one and only one of the flags is set
*/
KASSERT(((flags & UVM_LOAN_TOANON) == 0) ^
((flags & UVM_LOAN_TOPAGE) == 0));
KASSERT((map->flags & VM_MAP_INTRSAFE) == 0);
/*
* "output" is a pointer to the current place to put the loaned page.
*/
result = v;
output = &result[0]; /* start at the beginning ... */
/*
* while we've got pages to do
*/
while (len > 0) {
/*
* fill in params for a call to uvmfault_lookup
*/
ufi.orig_map = map;
ufi.orig_rvaddr = start;
ufi.orig_size = len;
/*
* do the lookup, the only time this will fail is if we hit on
* an unmapped region (an error)
*/
if (!uvmfault_lookup(&ufi, false)) {
error = ENOENT;
goto fail;
}
/*
* map now locked. now do the loanout...
*/
rv = uvm_loanentry(&ufi, &output, flags);
if (rv < 0) {
/* all unlocked due to error */
error = EINVAL;
goto fail;
}
/*
* done! the map is unlocked. advance, if possible.
*
* XXXCDC: could be recoded to hold the map lock with
* smarter code (but it only happens on map entry
* boundaries, so it isn't that bad).
*/
if (rv) {
rv <<= PAGE_SHIFT;
len -= rv;
start += rv;
}
}
UVMHIST_LOG(loanhist, "success", 0,0,0,0);
return 0;
fail:
/*
* failed to complete loans. drop any loans and return failure code.
* map is already unlocked.
*/
if (output - result) {
if (flags & UVM_LOAN_TOANON) {
uvm_unloananon((struct vm_anon **)result,
output - result);
} else {
uvm_unloanpage((struct vm_page **)result,
output - result);
}
}
UVMHIST_LOG(loanhist, "error %d", error,0,0,0);
return (error);
}
/*
* uvm_loananon: loan a page from an anon out
*
* => called with map, amap, uobj locked
* => return value:
* -1 = fatal error, everything is unlocked, abort.
* 0 = lookup in ufi went stale, everything unlocked, relookup and
* try again
* 1 = got it, everything still locked
*/
int
uvm_loananon(struct uvm_faultinfo *ufi, void ***output, int flags,
struct vm_anon *anon)
{
struct vm_page *pg;
int error;
UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist);
/*
* if we are loaning to "another" anon then it is easy, we just
* bump the reference count on the current anon and return a
* pointer to it (it becomes copy-on-write shared).
*/
if (flags & UVM_LOAN_TOANON) {
mutex_enter(&anon->an_lock);
pg = anon->an_page;
if (pg && (pg->pqflags & PQ_ANON) != 0 && anon->an_ref == 1) {
if (pg->wire_count > 0) {
UVMHIST_LOG(loanhist, "->A wired %p", pg,0,0,0);
uvmfault_unlockall(ufi,
ufi->entry->aref.ar_amap,
ufi->entry->object.uvm_obj, anon);
return (-1);
}
pmap_page_protect(pg, VM_PROT_READ);
}
anon->an_ref++;
**output = anon;
(*output)++;
mutex_exit(&anon->an_lock);
UVMHIST_LOG(loanhist, "->A done", 0,0,0,0);
return (1);
}
/*
* we are loaning to a kernel-page. we need to get the page
* resident so we can wire it. uvmfault_anonget will handle
* this for us.
*/
mutex_enter(&anon->an_lock);
error = uvmfault_anonget(ufi, ufi->entry->aref.ar_amap, anon);
/*
* if we were unable to get the anon, then uvmfault_anonget has
* unlocked everything and returned an error code.
*/
if (error) {
UVMHIST_LOG(loanhist, "error %d", error,0,0,0);
/* need to refault (i.e. refresh our lookup) ? */
if (error == ERESTART) {
return (0);
}
/* "try again"? sleep a bit and retry ... */
if (error == EAGAIN) {
tsleep(&lbolt, PVM, "loanagain", 0);
return (0);
}
/* otherwise flag it as an error */
return (-1);
}
/*
* we have the page and its owner locked: do the loan now.
*/
pg = anon->an_page;
mutex_enter(&uvm_pageqlock);
if (pg->wire_count > 0) {
mutex_exit(&uvm_pageqlock);
UVMHIST_LOG(loanhist, "->K wired %p", pg,0,0,0);
KASSERT(pg->uobject == NULL);
uvmfault_unlockall(ufi, ufi->entry->aref.ar_amap,
NULL, anon);
return (-1);
}
if (pg->loan_count == 0) {
pmap_page_protect(pg, VM_PROT_READ);
}
pg->loan_count++;
uvm_pageactivate(pg);
mutex_exit(&uvm_pageqlock);
**output = pg;
(*output)++;
/* unlock anon and return success */
if (pg->uobject)
mutex_exit(&pg->uobject->vmobjlock);
mutex_exit(&anon->an_lock);
UVMHIST_LOG(loanhist, "->K done", 0,0,0,0);
return (1);
}
/*
* uvm_loanpage: loan out pages to kernel (->K)
*
* => pages should be object-owned and the object should be locked.
* => in the case of error, the object might be unlocked and relocked.
* => caller should busy the pages beforehand.
* => pages will be unbusied.
* => fail with EBUSY if meet a wired page.
*/
static int
uvm_loanpage(struct vm_page **pgpp, int npages)
{
int i;
int error = 0;
UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist);
for (i = 0; i < npages; i++) {
struct vm_page *pg = pgpp[i];
KASSERT(pg->uobject != NULL);
KASSERT(pg->uobject == pgpp[0]->uobject);
KASSERT(!(pg->flags & (PG_RELEASED|PG_PAGEOUT)));
KASSERT(mutex_owned(&pg->uobject->vmobjlock));
KASSERT(pg->flags & PG_BUSY);
mutex_enter(&uvm_pageqlock);
if (pg->wire_count > 0) {
mutex_exit(&uvm_pageqlock);
UVMHIST_LOG(loanhist, "wired %p", pg,0,0,0);
error = EBUSY;
break;
}
if (pg->loan_count == 0) {
pmap_page_protect(pg, VM_PROT_READ);
}
pg->loan_count++;
uvm_pageactivate(pg);
mutex_exit(&uvm_pageqlock);
}
uvm_page_unbusy(pgpp, npages);
if (error) {
/*
* backout what we've done
*/
kmutex_t *slock = &pgpp[0]->uobject->vmobjlock;
mutex_exit(slock);
uvm_unloan(pgpp, i, UVM_LOAN_TOPAGE);
mutex_enter(slock);
}
UVMHIST_LOG(loanhist, "done %d", error,0,0,0);
return error;
}
/*
* XXX UBC temp limit
* number of pages to get at once.
* should be <= MAX_READ_AHEAD in genfs_vnops.c
*/
#define UVM_LOAN_GET_CHUNK 16
/*
* uvm_loanuobjpages: loan pages from a uobj out (O->K)
*
* => uobj shouldn't be locked. (we'll lock it)
* => fail with EBUSY if we meet a wired page.
*/
int
uvm_loanuobjpages(struct uvm_object *uobj, voff_t pgoff, int orignpages,
struct vm_page **origpgpp)
{
int ndone; /* # of pages loaned out */
struct vm_page **pgpp;
int error;
int i;
kmutex_t *slock;
pgpp = origpgpp;
for (ndone = 0; ndone < orignpages; ) {
int npages;
/* npendloan: # of pages busied but not loand out yet. */
int npendloan = 0xdead; /* XXX gcc */
reget:
npages = MIN(UVM_LOAN_GET_CHUNK, orignpages - ndone);
mutex_enter(&uobj->vmobjlock);
error = (*uobj->pgops->pgo_get)(uobj,
pgoff + (ndone << PAGE_SHIFT), pgpp, &npages, 0,
VM_PROT_READ, 0, PGO_SYNCIO);
if (error == EAGAIN) {
tsleep(&lbolt, PVM, "nfsread", 0);
continue;
}
if (error)
goto fail;
KASSERT(npages > 0);
/* loan and unbusy pages */
slock = NULL;
for (i = 0; i < npages; i++) {
kmutex_t *nextslock; /* slock for next page */
struct vm_page *pg = *pgpp;
/* XXX assuming that the page is owned by uobj */
KASSERT(pg->uobject != NULL);
nextslock = &pg->uobject->vmobjlock;
if (slock != nextslock) {
if (slock) {
KASSERT(npendloan > 0);
error = uvm_loanpage(pgpp - npendloan,
npendloan);
mutex_exit(slock);
if (error)
goto fail;
ndone += npendloan;
KASSERT(origpgpp + ndone == pgpp);
}
slock = nextslock;
npendloan = 0;
mutex_enter(slock);
}
if ((pg->flags & PG_RELEASED) != 0) {
/*
* release pages and try again.
*/
mutex_exit(slock);
for (; i < npages; i++) {
pg = pgpp[i];
slock = &pg->uobject->vmobjlock;
mutex_enter(slock);
mutex_enter(&uvm_pageqlock);
uvm_page_unbusy(&pg, 1);
mutex_exit(&uvm_pageqlock);
mutex_exit(slock);
}
goto reget;
}
npendloan++;
pgpp++;
KASSERT(origpgpp + ndone + npendloan == pgpp);
}
KASSERT(slock != NULL);
KASSERT(npendloan > 0);
error = uvm_loanpage(pgpp - npendloan, npendloan);
mutex_exit(slock);
if (error)
goto fail;
ndone += npendloan;
KASSERT(origpgpp + ndone == pgpp);
}
return 0;
fail:
uvm_unloan(origpgpp, ndone, UVM_LOAN_TOPAGE);
return error;
}
/*
* uvm_loanuobj: loan a page from a uobj out
*
* => called with map, amap, uobj locked
* => return value:
* -1 = fatal error, everything is unlocked, abort.
* 0 = lookup in ufi went stale, everything unlocked, relookup and
* try again
* 1 = got it, everything still locked
*/
static int
uvm_loanuobj(struct uvm_faultinfo *ufi, void ***output, int flags, vaddr_t va)
{
struct vm_amap *amap = ufi->entry->aref.ar_amap;
struct uvm_object *uobj = ufi->entry->object.uvm_obj;
struct vm_page *pg;
struct vm_anon *anon;
int error, npages;
bool locked;
UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist);
/*
* first we must make sure the page is resident.
*
* XXXCDC: duplicate code with uvm_fault().
*/
mutex_enter(&uobj->vmobjlock);
if (uobj->pgops->pgo_get) { /* try locked pgo_get */
npages = 1;
pg = NULL;
error = (*uobj->pgops->pgo_get)(uobj,
va - ufi->entry->start + ufi->entry->offset,
&pg, &npages, 0, VM_PROT_READ, MADV_NORMAL, PGO_LOCKED);
} else {
error = EIO; /* must have pgo_get op */
}
/*
* check the result of the locked pgo_get. if there is a problem,
* then we fail the loan.
*/
if (error && error != EBUSY) {
uvmfault_unlockall(ufi, amap, uobj, NULL);
return (-1);
}
/*
* if we need to unlock for I/O, do so now.
*/
if (error == EBUSY) {
uvmfault_unlockall(ufi, amap, NULL, NULL);
/* locked: uobj */
npages = 1;
error = (*uobj->pgops->pgo_get)(uobj,
va - ufi->entry->start + ufi->entry->offset,
&pg, &npages, 0, VM_PROT_READ, MADV_NORMAL, PGO_SYNCIO);
/* locked: <nothing> */
if (error) {
if (error == EAGAIN) {
tsleep(&lbolt, PVM, "fltagain2", 0);
return (0);
}
return (-1);
}
/*
* pgo_get was a success. attempt to relock everything.
*/
locked = uvmfault_relock(ufi);
if (locked && amap)
amap_lock(amap);
uobj = pg->uobject;
mutex_enter(&uobj->vmobjlock);
/*
* verify that the page has not be released and re-verify
* that amap slot is still free. if there is a problem we
* drop our lock (thus force a lookup refresh/retry).
*/
if ((pg->flags & PG_RELEASED) != 0 ||
(locked && amap && amap_lookup(&ufi->entry->aref,
ufi->orig_rvaddr - ufi->entry->start))) {
if (locked)
uvmfault_unlockall(ufi, amap, NULL, NULL);
locked = false;
}
/*
* didn't get the lock? release the page and retry.
*/
if (locked == false) {
if (pg->flags & PG_WANTED) {
wakeup(pg);
}
if (pg->flags & PG_RELEASED) {
mutex_enter(&uvm_pageqlock);
uvm_pagefree(pg);
mutex_exit(&uvm_pageqlock);
mutex_exit(&uobj->vmobjlock);
return (0);
}
mutex_enter(&uvm_pageqlock);
uvm_pageactivate(pg);
mutex_exit(&uvm_pageqlock);
pg->flags &= ~(PG_BUSY|PG_WANTED);
UVM_PAGE_OWN(pg, NULL);
mutex_exit(&uobj->vmobjlock);
return (0);
}
}
KASSERT(uobj == pg->uobject);
/*
* at this point we have the page we want ("pg") marked PG_BUSY for us
* and we have all data structures locked. do the loanout. page can
* not be PG_RELEASED (we caught this above).
*/
if ((flags & UVM_LOAN_TOANON) == 0) {
if (uvm_loanpage(&pg, 1)) {
uvmfault_unlockall(ufi, amap, uobj, NULL);
return (-1);
}
mutex_exit(&uobj->vmobjlock);
**output = pg;
(*output)++;
return (1);
}
/*
* must be a loan to an anon. check to see if there is already
* an anon associated with this page. if so, then just return
* a reference to this object. the page should already be
* mapped read-only because it is already on loan.
*/
if (pg->uanon) {
anon = pg->uanon;
mutex_enter(&anon->an_lock);
anon->an_ref++;
mutex_exit(&anon->an_lock);
if (pg->flags & PG_WANTED) {
wakeup(pg);
}
pg->flags &= ~(PG_WANTED|PG_BUSY);
UVM_PAGE_OWN(pg, NULL);
mutex_exit(&uobj->vmobjlock);
**output = anon;
(*output)++;
return (1);
}
/*
* need to allocate a new anon
*/
anon = uvm_analloc();
if (anon == NULL) {
goto fail;
}
anon->an_page = pg;
pg->uanon = anon;
mutex_enter(&uvm_pageqlock);
if (pg->wire_count > 0) {
mutex_exit(&uvm_pageqlock);
UVMHIST_LOG(loanhist, "wired %p", pg,0,0,0);
pg->uanon = NULL;
anon->an_page = NULL;
anon->an_ref--;
mutex_exit(&anon->an_lock);
uvm_anfree(anon);
goto fail;
}
if (pg->loan_count == 0) {
pmap_page_protect(pg, VM_PROT_READ);
}
pg->loan_count++;
uvm_pageactivate(pg);
mutex_exit(&uvm_pageqlock);
if (pg->flags & PG_WANTED) {
wakeup(pg);
}
pg->flags &= ~(PG_WANTED|PG_BUSY);
UVM_PAGE_OWN(pg, NULL);
mutex_exit(&uobj->vmobjlock);
mutex_exit(&anon->an_lock);
**output = anon;
(*output)++;
return (1);
fail:
UVMHIST_LOG(loanhist, "fail", 0,0,0,0);
/*
* unlock everything and bail out.
*/
if (pg->flags & PG_WANTED) {
wakeup(pg);
}
pg->flags &= ~(PG_WANTED|PG_BUSY);
UVM_PAGE_OWN(pg, NULL);
uvmfault_unlockall(ufi, amap, uobj, NULL);
return (-1);
}
/*
* uvm_loanzero: loan a zero-fill page out
*
* => called with map, amap, uobj locked
* => return value:
* -1 = fatal error, everything is unlocked, abort.
* 0 = lookup in ufi went stale, everything unlocked, relookup and
* try again
* 1 = got it, everything still locked
*/
static struct uvm_object uvm_loanzero_object;
static int
uvm_loanzero(struct uvm_faultinfo *ufi, void ***output, int flags)
{
struct vm_anon *anon;
struct vm_page *pg;
struct vm_amap *amap = ufi->entry->aref.ar_amap;
UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist);
again:
mutex_enter(&uvm_loanzero_object.vmobjlock);
/*
* first, get ahold of our single zero page.
*/
if (__predict_false((pg =
TAILQ_FIRST(&uvm_loanzero_object.memq)) == NULL)) {
while ((pg = uvm_pagealloc(&uvm_loanzero_object, 0, NULL,
UVM_PGA_ZERO)) == NULL) {
mutex_exit(&uvm_loanzero_object.vmobjlock);
uvmfault_unlockall(ufi, amap, NULL, NULL);
uvm_wait("loanzero");
if (!uvmfault_relock(ufi)) {
return (0);
}
if (amap) {
amap_lock(amap);
}
goto again;
}
/* got a zero'd page. */
pg->flags &= ~(PG_WANTED|PG_BUSY|PG_FAKE);
pg->flags |= PG_RDONLY;
mutex_enter(&uvm_pageqlock);
uvm_pageactivate(pg);
mutex_exit(&uvm_pageqlock);
UVM_PAGE_OWN(pg, NULL);
}
if ((flags & UVM_LOAN_TOANON) == 0) { /* loaning to kernel-page */
mutex_enter(&uvm_pageqlock);
pg->loan_count++;
mutex_exit(&uvm_pageqlock);
mutex_exit(&uvm_loanzero_object.vmobjlock);
**output = pg;
(*output)++;
return (1);
}
/*
* loaning to an anon. check to see if there is already an anon
* associated with this page. if so, then just return a reference
* to this object.
*/
if (pg->uanon) {
anon = pg->uanon;
mutex_enter(&anon->an_lock);
anon->an_ref++;
mutex_exit(&anon->an_lock);
mutex_exit(&uvm_loanzero_object.vmobjlock);
**output = anon;
(*output)++;
return (1);
}
/*
* need to allocate a new anon
*/
anon = uvm_analloc();
if (anon == NULL) {
/* out of swap causes us to fail */
mutex_exit(&uvm_loanzero_object.vmobjlock);
uvmfault_unlockall(ufi, amap, NULL, NULL);
return (-1);
}
anon->an_page = pg;
pg->uanon = anon;
mutex_enter(&uvm_pageqlock);
pg->loan_count++;
uvm_pageactivate(pg);
mutex_exit(&uvm_pageqlock);
mutex_exit(&anon->an_lock);
mutex_exit(&uvm_loanzero_object.vmobjlock);
**output = anon;
(*output)++;
return (1);
}
/*
* uvm_unloananon: kill loans on anons (basically a normal ref drop)
*
* => we expect all our resources to be unlocked
*/
static void
uvm_unloananon(struct vm_anon **aloans, int nanons)
{
struct vm_anon *anon;
while (nanons-- > 0) {
int refs;
anon = *aloans++;
mutex_enter(&anon->an_lock);
refs = --anon->an_ref;
mutex_exit(&anon->an_lock);
if (refs == 0) {
uvm_anfree(anon);
}
}
}
/*
* uvm_unloanpage: kill loans on pages loaned out to the kernel
*
* => we expect all our resources to be unlocked
*/
static void
uvm_unloanpage(struct vm_page **ploans, int npages)
{
struct vm_page *pg;
kmutex_t *slock;
mutex_enter(&uvm_pageqlock);
while (npages-- > 0) {
pg = *ploans++;
/*
* do a little dance to acquire the object or anon lock
* as appropriate. we are locking in the wrong order,
* so we have to do a try-lock here.
*/
slock = NULL;
while (pg->uobject != NULL || pg->uanon != NULL) {
if (pg->uobject != NULL) {
slock = &pg->uobject->vmobjlock;
} else {
slock = &pg->uanon->an_lock;
}
if (mutex_tryenter(slock)) {
break;
}
mutex_exit(&uvm_pageqlock);
/* XXX Better than yielding but inadequate. */
kpause("livelock", false, 1, NULL);
mutex_enter(&uvm_pageqlock);
slock = NULL;
}
/*
* drop our loan. if page is owned by an anon but
* PQ_ANON is not set, the page was loaned to the anon
* from an object which dropped ownership, so resolve
* this by turning the anon's loan into real ownership