aboutsummaryrefslogtreecommitdiffstats
path: root/fs/afs/write.c
blob: f447c902318da02330b4a08c35bfb6d09481f25c (plain)
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
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
// SPDX-License-Identifier: GPL-2.0-or-later
/* handling of writes to regular files and writing back to the server
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/backing-dev.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include <linux/netfs.h>
#include "internal.h"

static void afs_write_to_cache(struct afs_vnode *vnode, loff_t start, size_t len,
			       loff_t i_size, bool caching);

#ifdef CONFIG_AFS_FSCACHE
/*
 * Mark a page as having been made dirty and thus needing writeback.  We also
 * need to pin the cache object to write back to.
 */
int afs_set_page_dirty(struct page *page)
{
	return fscache_set_page_dirty(page, afs_vnode_cache(AFS_FS_I(page->mapping->host)));
}
static void afs_folio_start_fscache(bool caching, struct folio *folio)
{
	if (caching)
		folio_start_fscache(folio);
}
#else
static void afs_folio_start_fscache(bool caching, struct folio *folio)
{
}
#endif

/*
 * prepare to perform part of a write to a page
 */
int afs_write_begin(struct file *file, struct address_space *mapping,
		    loff_t pos, unsigned len, unsigned flags,
		    struct page **_page, void **fsdata)
{
	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
	struct folio *folio;
	unsigned long priv;
	unsigned f, from;
	unsigned t, to;
	pgoff_t index;
	int ret;

	_enter("{%llx:%llu},%llx,%x",
	       vnode->fid.vid, vnode->fid.vnode, pos, len);

	/* Prefetch area to be written into the cache if we're caching this
	 * file.  We need to do this before we get a lock on the page in case
	 * there's more than one writer competing for the same cache block.
	 */
	ret = netfs_write_begin(file, mapping, pos, len, flags, &folio, fsdata,
				&afs_req_ops, NULL);
	if (ret < 0)
		return ret;

	index = folio_index(folio);
	from = pos - index * PAGE_SIZE;
	to = from + len;

try_again:
	/* See if this page is already partially written in a way that we can
	 * merge the new write with.
	 */
	if (folio_test_private(folio)) {
		priv = (unsigned long)folio_get_private(folio);
		f = afs_folio_dirty_from(folio, priv);
		t = afs_folio_dirty_to(folio, priv);
		ASSERTCMP(f, <=, t);

		if (folio_test_writeback(folio)) {
			trace_afs_folio_dirty(vnode, tracepoint_string("alrdy"), folio);
			goto flush_conflicting_write;
		}
		/* If the file is being filled locally, allow inter-write
		 * spaces to be merged into writes.  If it's not, only write
		 * back what the user gives us.
		 */
		if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
		    (to < f || from > t))
			goto flush_conflicting_write;
	}

	*_page = &folio->page;
	_leave(" = 0");
	return 0;

	/* The previous write and this write aren't adjacent or overlapping, so
	 * flush the page out.
	 */
flush_conflicting_write:
	_debug("flush conflict");
	ret = folio_write_one(folio);
	if (ret < 0)
		goto error;

	ret = folio_lock_killable(folio);
	if (ret < 0)
		goto error;
	goto try_again;

error:
	folio_put(folio);
	_leave(" = %d", ret);
	return ret;
}

/*
 * finalise part of a write to a page
 */
int afs_write_end(struct file *file, struct address_space *mapping,
		  loff_t pos, unsigned len, unsigned copied,
		  struct page *subpage, void *fsdata)
{
	struct folio *folio = page_folio(subpage);
	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
	unsigned long priv;
	unsigned int f, from = offset_in_folio(folio, pos);
	unsigned int t, to = from + copied;
	loff_t i_size, write_end_pos;

	_enter("{%llx:%llu},{%lx}",
	       vnode->fid.vid, vnode->fid.vnode, folio_index(folio));

	if (!folio_test_uptodate(folio)) {
		if (copied < len) {
			copied = 0;
			goto out;
		}

		folio_mark_uptodate(folio);
	}

	if (copied == 0)
		goto out;

	write_end_pos = pos + copied;

	i_size = i_size_read(&vnode->vfs_inode);
	if (write_end_pos > i_size) {
		write_seqlock(&vnode->cb_lock);
		i_size = i_size_read(&vnode->vfs_inode);
		if (write_end_pos > i_size)
			afs_set_i_size(vnode, write_end_pos);
		write_sequnlock(&vnode->cb_lock);
		fscache_update_cookie(afs_vnode_cache(vnode), NULL, &write_end_pos);
	}

	if (folio_test_private(folio)) {
		priv = (unsigned long)folio_get_private(folio);
		f = afs_folio_dirty_from(folio, priv);
		t = afs_folio_dirty_to(folio, priv);
		if (from < f)
			f = from;
		if (to > t)
			t = to;
		priv = afs_folio_dirty(folio, f, t);
		folio_change_private(folio, (void *)priv);
		trace_afs_folio_dirty(vnode, tracepoint_string("dirty+"), folio);
	} else {
		priv = afs_folio_dirty(folio, from, to);
		folio_attach_private(folio, (void *)priv);
		trace_afs_folio_dirty(vnode, tracepoint_string("dirty"), folio);
	}

	if (folio_mark_dirty(folio))
		_debug("dirtied %lx", folio_index(folio));

out:
	folio_unlock(folio);
	folio_put(folio);
	return copied;
}

/*
 * kill all the pages in the given range
 */
static void afs_kill_pages(struct address_space *mapping,
			   loff_t start, loff_t len)
{
	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
	struct folio *folio;
	pgoff_t index = start / PAGE_SIZE;
	pgoff_t last = (start + len - 1) / PAGE_SIZE, next;

	_enter("{%llx:%llu},%llx @%llx",
	       vnode->fid.vid, vnode->fid.vnode, len, start);

	do {
		_debug("kill %lx (to %lx)", index, last);

		folio = filemap_get_folio(mapping, index);
		if (!folio) {
			next = index + 1;
			continue;
		}

		next = folio_next_index(folio);

		folio_clear_uptodate(folio);
		folio_end_writeback(folio);
		folio_lock(folio);
		generic_error_remove_page(mapping, &folio->page);
		folio_unlock(folio);
		folio_put(folio);

	} while (index = next, index <= last);

	_leave("");
}

/*
 * Redirty all the pages in a given range.
 */
static void afs_redirty_pages(struct writeback_control *wbc,
			      struct address_space *mapping,
			      loff_t start, loff_t len)
{
	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
	struct folio *folio;
	pgoff_t index = start / PAGE_SIZE;
	pgoff_t last = (start + len - 1) / PAGE_SIZE, next;

	_enter("{%llx:%llu},%llx @%llx",
	       vnode->fid.vid, vnode->fid.vnode, len, start);

	do {
		_debug("redirty %llx @%llx", len, start);

		folio = filemap_get_folio(mapping, index);
		if (!folio) {
			next = index + 1;
			continue;
		}

		next = index + folio_nr_pages(folio);
		folio_redirty_for_writepage(wbc, folio);
		folio_end_writeback(folio);
		folio_put(folio);
	} while (index = next, index <= last);

	_leave("");
}

/*
 * completion of write to server
 */
static void afs_pages_written_back(struct afs_vnode *vnode, loff_t start, unsigned int len)
{
	struct address_space *mapping = vnode->vfs_inode.i_mapping;
	struct folio *folio;
	pgoff_t end;

	XA_STATE(xas, &mapping->i_pages, start / PAGE_SIZE);

	_enter("{%llx:%llu},{%x @%llx}",
	       vnode->fid.vid, vnode->fid.vnode, len, start);

	rcu_read_lock();

	end = (start + len - 1) / PAGE_SIZE;
	xas_for_each(&xas, folio, end) {
		if (!folio_test_writeback(folio)) {
			kdebug("bad %x @%llx page %lx %lx",
			       len, start, folio_index(folio), end);
			ASSERT(folio_test_writeback(folio));
		}

		trace_afs_folio_dirty(vnode, tracepoint_string("clear"), folio);
		folio_detach_private(folio);
		folio_end_writeback(folio);
	}

	rcu_read_unlock();

	afs_prune_wb_keys(vnode);
	_leave("");
}

/*
 * Find a key to use for the writeback.  We cached the keys used to author the
 * writes on the vnode.  *_wbk will contain the last writeback key used or NULL
 * and we need to start from there if it's set.
 */
static int afs_get_writeback_key(struct afs_vnode *vnode,
				 struct afs_wb_key **_wbk)
{
	struct afs_wb_key *wbk = NULL;
	struct list_head *p;
	int ret = -ENOKEY, ret2;

	spin_lock(&vnode->wb_lock);
	if (*_wbk)
		p = (*_wbk)->vnode_link.next;
	else
		p = vnode->wb_keys.next;

	while (p != &vnode->wb_keys) {
		wbk = list_entry(p, struct afs_wb_key, vnode_link);
		_debug("wbk %u", key_serial(wbk->key));
		ret2 = key_validate(wbk->key);
		if (ret2 == 0) {
			refcount_inc(&wbk->usage);
			_debug("USE WB KEY %u", key_serial(wbk->key));
			break;
		}

		wbk = NULL;
		if (ret == -ENOKEY)
			ret = ret2;
		p = p->next;
	}

	spin_unlock(&vnode->wb_lock);
	if (*_wbk)
		afs_put_wb_key(*_wbk);
	*_wbk = wbk;
	return 0;
}

static void afs_store_data_success(struct afs_operation *op)
{
	struct afs_vnode *vnode = op->file[0].vnode;

	op->ctime = op->file[0].scb.status.mtime_client;
	afs_vnode_commit_status(op, &op->file[0]);
	if (op->error == 0) {
		if (!op->store.laundering)
			afs_pages_written_back(vnode, op->store.pos, op->store.size);
		afs_stat_v(vnode, n_stores);
		atomic_long_add(op->store.size, &afs_v2net(vnode)->n_store_bytes);
	}
}

static const struct afs_operation_ops afs_store_data_operation = {
	.issue_afs_rpc	= afs_fs_store_data,
	.issue_yfs_rpc	= yfs_fs_store_data,
	.success	= afs_store_data_success,
};

/*
 * write to a file
 */
static int afs_store_data(struct afs_vnode *vnode, struct iov_iter *iter, loff_t pos,
			  bool laundering)
{
	struct afs_operation *op;
	struct afs_wb_key *wbk = NULL;
	loff_t size = iov_iter_count(iter), i_size;
	int ret = -ENOKEY;

	_enter("%s{%llx:%llu.%u},%llx,%llx",
	       vnode->volume->name,
	       vnode->fid.vid,
	       vnode->fid.vnode,
	       vnode->fid.unique,
	       size, pos);

	ret = afs_get_writeback_key(vnode, &wbk);
	if (ret) {
		_leave(" = %d [no keys]", ret);
		return ret;
	}

	op = afs_alloc_operation(wbk->key, vnode->volume);
	if (IS_ERR(op)) {
		afs_put_wb_key(wbk);
		return -ENOMEM;
	}

	i_size = i_size_read(&vnode->vfs_inode);

	afs_op_set_vnode(op, 0, vnode);
	op->file[0].dv_delta = 1;
	op->file[0].modification = true;
	op->store.write_iter = iter;
	op->store.pos = pos;
	op->store.size = size;
	op->store.i_size = max(pos + size, i_size);
	op->store.laundering = laundering;
	op->mtime = vnode->vfs_inode.i_mtime;
	op->flags |= AFS_OPERATION_UNINTR;
	op->ops = &afs_store_data_operation;

try_next_key:
	afs_begin_vnode_operation(op);
	afs_wait_for_operation(op);

	switch (op->error) {
	case -EACCES:
	case -EPERM:
	case -ENOKEY:
	case -EKEYEXPIRED:
	case -EKEYREJECTED:
	case -EKEYREVOKED:
		_debug("next");

		ret = afs_get_writeback_key(vnode, &wbk);
		if (ret == 0) {
			key_put(op->key);
			op->key = key_get(wbk->key);
			goto try_next_key;
		}
		break;
	}

	afs_put_wb_key(wbk);
	_leave(" = %d", op->error);
	return afs_put_operation(op);
}

/*
 * Extend the region to be written back to include subsequent contiguously
 * dirty pages if possible, but don't sleep while doing so.
 *
 * If this page holds new content, then we can include filler zeros in the
 * writeback.
 */
static void afs_extend_writeback(struct address_space *mapping,
				 struct afs_vnode *vnode,
				 long *_count,
				 loff_t start,
				 loff_t max_len,
				 bool new_content,
				 bool caching,
				 unsigned int *_len)
{
	struct pagevec pvec;
	struct folio *folio;
	unsigned long priv;
	unsigned int psize, filler = 0;
	unsigned int f, t;
	loff_t len = *_len;
	pgoff_t index = (start + len) / PAGE_SIZE;
	bool stop = true;
	unsigned int i;

	XA_STATE(xas, &mapping->i_pages, index);
	pagevec_init(&pvec);

	do {
		/* Firstly, we gather up a batch of contiguous dirty pages
		 * under the RCU read lock - but we can't clear the dirty flags
		 * there if any of those pages are mapped.
		 */
		rcu_read_lock();

		xas_for_each(&xas, folio, ULONG_MAX) {
			stop = true;
			if (xas_retry(&xas, folio))
				continue;
			if (xa_is_value(folio))
				break;
			if (folio_index(folio) != index)
				break;

			if (!folio_try_get_rcu(folio)) {
				xas_reset(&xas);
				continue;
			}

			/* Has the page moved or been split? */
			if (unlikely(folio != xas_reload(&xas))) {
				folio_put(folio);
				break;
			}

			if (!folio_trylock(folio)) {
				folio_put(folio);
				break;
			}
			if (!folio_test_dirty(folio) ||
			    folio_test_writeback(folio) ||
			    folio_test_fscache(folio)) {
				folio_unlock(folio);
				folio_put(folio);
				break;
			}

			psize = folio_size(folio);
			priv = (unsigned long)folio_get_private(folio);
			f = afs_folio_dirty_from(folio, priv);
			t = afs_folio_dirty_to(folio, priv);
			if (f != 0 && !new_content) {
				folio_unlock(folio);
				folio_put(folio);
				break;
			}

			len += filler + t;
			filler = psize - t;
			if (len >= max_len || *_count <= 0)
				stop = true;
			else if (t == psize || new_content)
				stop = false;

			index += folio_nr_pages(folio);
			if (!pagevec_add(&pvec, &folio->page))
				break;
			if (stop)
				break;
		}

		if (!stop)
			xas_pause(&xas);
		rcu_read_unlock();

		/* Now, if we obtained any pages, we can shift them to being
		 * writable and mark them for caching.
		 */
		if (!pagevec_count(&pvec))
			break;

		for (i = 0; i < pagevec_count(&pvec); i++) {
			folio = page_folio(pvec.pages[i]);
			trace_afs_folio_dirty(vnode, tracepoint_string("store+"), folio);

			if (!folio_clear_dirty_for_io(folio))
				BUG();
			if (folio_start_writeback(folio))
				BUG();
			afs_folio_start_fscache(caching, folio);

			*_count -= folio_nr_pages(folio);
			folio_unlock(folio);
		}

		pagevec_release(&pvec);
		cond_resched();
	} while (!stop);

	*_len = len;
}

/*
 * Synchronously write back the locked page and any subsequent non-locked dirty
 * pages.
 */
static ssize_t afs_write_back_from_locked_folio(struct address_space *mapping,
						struct writeback_control *wbc,
						struct folio *folio,
						loff_t start, loff_t end)
{
	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
	struct iov_iter iter;
	unsigned long priv;
	unsigned int offset, to, len, max_len;
	loff_t i_size = i_size_read(&vnode->vfs_inode);
	bool new_content = test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
	bool caching = fscache_cookie_enabled(afs_vnode_cache(vnode));
	long count = wbc->nr_to_write;
	int ret;

	_enter(",%lx,%llx-%llx", folio_index(folio), start, end);

	if (folio_start_writeback(folio))
		BUG();
	afs_folio_start_fscache(caching, folio);

	count -= folio_nr_pages(folio);

	/* Find all consecutive lockable dirty pages that have contiguous
	 * written regions, stopping when we find a page that is not
	 * immediately lockable, is not dirty or is missing, or we reach the
	 * end of the range.
	 */
	priv = (unsigned long)folio_get_private(folio);
	offset = afs_folio_dirty_from(folio, priv);
	to = afs_folio_dirty_to(folio, priv);
	trace_afs_folio_dirty(vnode, tracepoint_string("store"), folio);

	len = to - offset;
	start += offset;
	if (start < i_size) {
		/* Trim the write to the EOF; the extra data is ignored.  Also
		 * put an upper limit on the size of a single storedata op.
		 */
		max_len = 65536 * 4096;
		max_len = min_t(unsigned long long, max_len, end - start + 1);
		max_len = min_t(unsigned long long, max_len, i_size - start);

		if (len < max_len &&
		    (to == folio_size(folio) || new_content))
			afs_extend_writeback(mapping, vnode, &count,
					     start, max_len, new_content,
					     caching, &len);
		len = min_t(loff_t, len, max_len);
	}

	/* We now have a contiguous set of dirty pages, each with writeback
	 * set; the first page is still locked at this point, but all the rest
	 * have been unlocked.
	 */
	folio_unlock(folio);

	if (start < i_size) {
		_debug("write back %x @%llx [%llx]", len, start, i_size);

		/* Speculatively write to the cache.  We have to fix this up
		 * later if the store fails.
		 */
		afs_write_to_cache(vnode, start, len, i_size, caching);

		iov_iter_xarray(&iter, WRITE, &mapping->i_pages, start, len);
		ret = afs_store_data(vnode, &iter, start, false);
	} else {
		_debug("write discard %x @%llx [%llx]", len, start, i_size);

		/* The dirty region was entirely beyond the EOF. */
		fscache_clear_page_bits(afs_vnode_cache(vnode),
					mapping, start, len, caching);
		afs_pages_written_back(vnode, start, len);
		ret = 0;
	}

	switch (ret) {
	case 0:
		wbc->nr_to_write = count;
		ret = len;
		break;

	default:
		pr_notice("kAFS: Unexpected error from FS.StoreData %d\n", ret);
		fallthrough;
	case -EACCES:
	case -EPERM:
	case -ENOKEY:
	case -EKEYEXPIRED:
	case -EKEYREJECTED:
	case -EKEYREVOKED:
		afs_redirty_pages(wbc, mapping, start, len);
		mapping_set_error(mapping, ret);
		break;

	case -EDQUOT:
	case -ENOSPC:
		afs_redirty_pages(wbc, mapping, start, len);
		mapping_set_error(mapping, -ENOSPC);
		break;

	case -EROFS:
	case -EIO:
	case -EREMOTEIO:
	case -EFBIG:
	case -ENOENT:
	case -ENOMEDIUM:
	case -ENXIO:
		trace_afs_file_error(vnode, ret, afs_file_error_writeback_fail);
		afs_kill_pages(mapping, start, len);
		mapping_set_error(mapping, ret);
		break;
	}

	_leave(" = %d", ret);
	return ret;
}

/*
 * write a page back to the server
 * - the caller locked the page for us
 */
int afs_writepage(struct page *subpage, struct writeback_control *wbc)
{
	struct folio *folio = page_folio(subpage);
	ssize_t ret;
	loff_t start;

	_enter("{%lx},", folio_index(folio));

#ifdef CONFIG_AFS_FSCACHE
	folio_wait_fscache(folio);
#endif

	start = folio_index(folio) * PAGE_SIZE;
	ret = afs_write_back_from_locked_folio(folio_mapping(folio), wbc,
					       folio, start, LLONG_MAX - start);
	if (ret < 0) {
		_leave(" = %zd", ret);
		return ret;
	}

	_leave(" = 0");
	return 0;
}

/*
 * write a region of pages back to the server
 */
static int afs_writepages_region(struct address_space *mapping,
				 struct writeback_control *wbc,
				 loff_t start, loff_t end, loff_t *_next)
{
	struct folio *folio;
	struct page *head_page;
	ssize_t ret;
	int n, skips = 0;

	_enter("%llx,%llx,", start, end);

	do {
		pgoff_t index = start / PAGE_SIZE;

		n = find_get_pages_range_tag(mapping, &index, end / PAGE_SIZE,
					     PAGECACHE_TAG_DIRTY, 1, &head_page);
		if (!n)
			break;

		folio = page_folio(head_page);
		start = folio_pos(folio); /* May regress with THPs */

		_debug("wback %lx", folio_index(folio));

		/* At this point we hold neither the i_pages lock nor the
		 * page lock: the page may be truncated or invalidated
		 * (changing page->mapping to NULL), or even swizzled
		 * back from swapper_space to tmpfs file mapping
		 */
		if (wbc->sync_mode != WB_SYNC_NONE) {
			ret = folio_lock_killable(folio);
			if (ret < 0) {
				folio_put(folio);
				return ret;
			}
		} else {
			if (!folio_trylock(folio)) {
				folio_put(folio);
				return 0;
			}
		}

		if (folio_mapping(folio) != mapping ||
		    !folio_test_dirty(folio)) {
			start += folio_size(folio);
			folio_unlock(folio);
			folio_put(folio);
			continue;
		}

		if (folio_test_writeback(folio) ||
		    folio_test_fscache(folio)) {
			folio_unlock(folio);
			if (wbc->sync_mode != WB_SYNC_NONE) {
				folio_wait_writeback(folio);
#ifdef CONFIG_AFS_FSCACHE
				folio_wait_fscache(folio);
#endif
			} else {
				start += folio_size(folio);
			}
			folio_put(folio);
			if (wbc->sync_mode == WB_SYNC_NONE) {
				if (skips >= 5 || need_resched())
					break;
				skips++;
			}
			continue;
		}

		if (!folio_clear_dirty_for_io(folio))
			BUG();
		ret = afs_write_back_from_locked_folio(mapping, wbc, folio, start, end);
		folio_put(folio);
		if (ret < 0) {
			_leave(" = %zd", ret);
			return ret;
		}

		start += ret;

		cond_resched();
	} while (wbc->nr_to_write > 0);

	*_next = start;
	_leave(" = 0 [%llx]", *_next);
	return 0;
}

/*
 * write some of the pending data back to the server
 */
int afs_writepages(struct address_space *mapping,
		   struct writeback_control *wbc)
{
	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
	loff_t start, next;
	int ret;

	_enter("");

	/* We have to be careful as we can end up racing with setattr()
	 * truncating the pagecache since the caller doesn't take a lock here
	 * to prevent it.
	 */
	if (wbc->sync_mode == WB_SYNC_ALL)
		down_read(&vnode->validate_lock);
	else if (!down_read_trylock(&vnode->validate_lock))
		return 0;

	if (wbc->range_cyclic) {
		start = mapping->writeback_index * PAGE_SIZE;
		ret = afs_writepages_region(mapping, wbc, start, LLONG_MAX, &next);
		if (ret == 0) {
			mapping->writeback_index = next / PAGE_SIZE;
			if (start > 0 && wbc->nr_to_write > 0) {
				ret = afs_writepages_region(mapping, wbc, 0,
							    start, &next);
				if (ret == 0)
					mapping->writeback_index =
						next / PAGE_SIZE;
			}
		}
	} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
		ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX, &next);
		if (wbc->nr_to_write > 0 && ret == 0)
			mapping->writeback_index = next / PAGE_SIZE;
	} else {
		ret = afs_writepages_region(mapping, wbc,
					    wbc->range_start, wbc->range_end, &next);
	}

	up_read(&vnode->validate_lock);
	_leave(" = %d", ret);
	return ret;
}

/*
 * write to an AFS file
 */
ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
{
	struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
	struct afs_file *af = iocb->ki_filp->private_data;
	ssize_t result;
	size_t count = iov_iter_count(from);

	_enter("{%llx:%llu},{%zu},",
	       vnode->fid.vid, vnode->fid.vnode, count);

	if (IS_SWAPFILE(&vnode->vfs_inode)) {
		printk(KERN_INFO
		       "AFS: Attempt to write to active swap file!\n");
		return -EBUSY;
	}

	if (!count)
		return 0;

	result = afs_validate(vnode, af->key);
	if (result < 0)
		return result;

	result = generic_file_write_iter(iocb, from);

	_leave(" = %zd", result);
	return result;
}

/*
 * flush any dirty pages for this process, and check for write errors.
 * - the return status from this call provides a reliable indication of
 *   whether any write errors occurred for this process.
 */
int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
	struct afs_file *af = file->private_data;
	int ret;

	_enter("{%llx:%llu},{n=%pD},%d",
	       vnode->fid.vid, vnode->fid.vnode, file,
	       datasync);

	ret = afs_validate(vnode, af->key);
	if (ret < 0)
		return ret;

	return file_write_and_wait_range(file, start, end);
}

/*
 * notification that a previously read-only page is about to become writable
 * - if it returns an error, the caller will deliver a bus error signal
 */
vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
{
	struct folio *folio = page_folio(vmf->page);
	struct file *file = vmf->vma->vm_file;
	struct inode *inode = file_inode(file);
	struct afs_vnode *vnode = AFS_FS_I(inode);
	struct afs_file *af = file->private_data;
	unsigned long priv;
	vm_fault_t ret = VM_FAULT_RETRY;

	_enter("{{%llx:%llu}},{%lx}", vnode->fid.vid, vnode->fid.vnode, folio_index(folio));

	afs_validate(vnode, af->key);

	sb_start_pagefault(inode->i_sb);

	/* Wait for the page to be written to the cache before we allow it to
	 * be modified.  We then assume the entire page will need writing back.
	 */
#ifdef CONFIG_AFS_FSCACHE
	if (folio_test_fscache(folio) &&
	    folio_wait_fscache_killable(folio) < 0)
		goto out;
#endif

	if (folio_wait_writeback_killable(folio))
		goto out;

	if (folio_lock_killable(folio) < 0)
		goto out;

	/* We mustn't change folio->private until writeback is complete as that
	 * details the portion of the page we need to write back and we might
	 * need to redirty the page if there's a problem.
	 */
	if (folio_wait_writeback_killable(folio) < 0) {
		folio_unlock(folio);
		goto out;
	}

	priv = afs_folio_dirty(folio, 0, folio_size(folio));
	priv = afs_folio_dirty_mmapped(priv);
	if (folio_test_private(folio)) {
		folio_change_private(folio, (void *)priv);
		trace_afs_folio_dirty(vnode, tracepoint_string("mkwrite+"), folio);
	} else {
		folio_attach_private(folio, (void *)priv);
		trace_afs_folio_dirty(vnode, tracepoint_string("mkwrite"), folio);
	}
	file_update_time(file);

	ret = VM_FAULT_LOCKED;
out:
	sb_end_pagefault(inode->i_sb);
	return ret;
}

/*
 * Prune the keys cached for writeback.  The caller must hold vnode->wb_lock.
 */
void afs_prune_wb_keys(struct afs_vnode *vnode)
{
	LIST_HEAD(graveyard);
	struct afs_wb_key *wbk, *tmp;

	/* Discard unused keys */
	spin_lock(&vnode->wb_lock);

	if (!mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_WRITEBACK) &&
	    !mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_DIRTY)) {
		list_for_each_entry_safe(wbk, tmp, &vnode->wb_keys, vnode_link) {
			if (refcount_read(&wbk->usage) == 1)
				list_move(&wbk->vnode_link, &graveyard);
		}
	}

	spin_unlock(&vnode->wb_lock);

	while (!list_empty(&graveyard)) {
		wbk = list_entry(graveyard.next, struct afs_wb_key, vnode_link);
		list_del(&wbk->vnode_link);
		afs_put_wb_key(wbk);
	}
}

/*
 * Clean up a page during invalidation.
 */
int afs_launder_page(struct page *subpage)
{
	struct folio *folio = page_folio(subpage);
	struct afs_vnode *vnode = AFS_FS_I(folio_inode(folio));
	struct iov_iter iter;
	struct bio_vec bv[1];
	unsigned long priv;
	unsigned int f, t;
	int ret = 0;

	_enter("{%lx}", folio_index(folio));

	priv = (unsigned long)folio_get_private(folio);
	if (folio_clear_dirty_for_io(folio)) {
		f = 0;
		t = folio_size(folio);
		if (folio_test_private(folio)) {
			f = afs_folio_dirty_from(folio, priv);
			t = afs_folio_dirty_to(folio, priv);
		}

		bv[0].bv_page = &folio->page;
		bv[0].bv_offset = f;
		bv[0].bv_len = t - f;
		iov_iter_bvec(&iter, WRITE, bv, 1, bv[0].bv_len);

		trace_afs_folio_dirty(vnode, tracepoint_string("launder"), folio);
		ret = afs_store_data(vnode, &iter, folio_pos(folio) + f, true);
	}

	trace_afs_folio_dirty(vnode, tracepoint_string("laundered"), folio);
	folio_detach_private(folio);
	folio_wait_fscache(folio);
	return ret;
}

/*
 * Deal with the completion of writing the data to the cache.
 */
static void afs_write_to_cache_done(void *priv, ssize_t transferred_or_error,
				    bool was_async)
{
	struct afs_vnode *vnode = priv;

	if (IS_ERR_VALUE(transferred_or_error) &&
	    transferred_or_error != -ENOBUFS)
		afs_invalidate_cache(vnode, 0);
}

/*
 * Save the write to the cache also.
 */
static void afs_write_to_cache(struct afs_vnode *vnode,
			       loff_t start, size_t len, loff_t i_size,
			       bool caching)
{
	fscache_write_to_cache(afs_vnode_cache(vnode),
			       vnode->vfs_inode.i_mapping, start, len, i_size,
			       afs_write_to_cache_done, vnode, caching);
}