GNU Linux-libre 4.9.308-gnu1
[releases.git] / fs / afs / write.c
1 /* handling of writes to regular files and writing back to the server
2  *
3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 #include <linux/backing-dev.h>
12 #include <linux/slab.h>
13 #include <linux/fs.h>
14 #include <linux/pagemap.h>
15 #include <linux/writeback.h>
16 #include <linux/pagevec.h>
17 #include "internal.h"
18
19 static int afs_write_back_from_locked_page(struct afs_writeback *wb,
20                                            struct page *page);
21
22 /*
23  * mark a page as having been made dirty and thus needing writeback
24  */
25 int afs_set_page_dirty(struct page *page)
26 {
27         _enter("");
28         return __set_page_dirty_nobuffers(page);
29 }
30
31 /*
32  * unlink a writeback record because its usage has reached zero
33  * - must be called with the wb->vnode->writeback_lock held
34  */
35 static void afs_unlink_writeback(struct afs_writeback *wb)
36 {
37         struct afs_writeback *front;
38         struct afs_vnode *vnode = wb->vnode;
39
40         list_del_init(&wb->link);
41         if (!list_empty(&vnode->writebacks)) {
42                 /* if an fsync rises to the front of the queue then wake it
43                  * up */
44                 front = list_entry(vnode->writebacks.next,
45                                    struct afs_writeback, link);
46                 if (front->state == AFS_WBACK_SYNCING) {
47                         _debug("wake up sync");
48                         front->state = AFS_WBACK_COMPLETE;
49                         wake_up(&front->waitq);
50                 }
51         }
52 }
53
54 /*
55  * free a writeback record
56  */
57 static void afs_free_writeback(struct afs_writeback *wb)
58 {
59         _enter("");
60         key_put(wb->key);
61         kfree(wb);
62 }
63
64 /*
65  * dispose of a reference to a writeback record
66  */
67 void afs_put_writeback(struct afs_writeback *wb)
68 {
69         struct afs_vnode *vnode = wb->vnode;
70
71         _enter("{%d}", wb->usage);
72
73         spin_lock(&vnode->writeback_lock);
74         if (--wb->usage == 0)
75                 afs_unlink_writeback(wb);
76         else
77                 wb = NULL;
78         spin_unlock(&vnode->writeback_lock);
79         if (wb)
80                 afs_free_writeback(wb);
81 }
82
83 /*
84  * partly or wholly fill a page that's under preparation for writing
85  */
86 static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
87                          loff_t pos, struct page *page)
88 {
89         loff_t i_size;
90         int ret;
91         int len;
92
93         _enter(",,%llu", (unsigned long long)pos);
94
95         i_size = i_size_read(&vnode->vfs_inode);
96         if (pos + PAGE_SIZE > i_size)
97                 len = i_size - pos;
98         else
99                 len = PAGE_SIZE;
100
101         ret = afs_vnode_fetch_data(vnode, key, pos, len, page);
102         if (ret < 0) {
103                 if (ret == -ENOENT) {
104                         _debug("got NOENT from server"
105                                " - marking file deleted and stale");
106                         set_bit(AFS_VNODE_DELETED, &vnode->flags);
107                         ret = -ESTALE;
108                 }
109         }
110
111         _leave(" = %d", ret);
112         return ret;
113 }
114
115 /*
116  * prepare to perform part of a write to a page
117  */
118 int afs_write_begin(struct file *file, struct address_space *mapping,
119                     loff_t pos, unsigned len, unsigned flags,
120                     struct page **pagep, void **fsdata)
121 {
122         struct afs_writeback *candidate, *wb;
123         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
124         struct page *page;
125         struct key *key = file->private_data;
126         unsigned from = pos & (PAGE_SIZE - 1);
127         unsigned to = from + len;
128         pgoff_t index = pos >> PAGE_SHIFT;
129         int ret;
130
131         _enter("{%x:%u},{%lx},%u,%u",
132                vnode->fid.vid, vnode->fid.vnode, index, from, to);
133
134         candidate = kzalloc(sizeof(*candidate), GFP_KERNEL);
135         if (!candidate)
136                 return -ENOMEM;
137         candidate->vnode = vnode;
138         candidate->first = candidate->last = index;
139         candidate->offset_first = from;
140         candidate->to_last = to;
141         INIT_LIST_HEAD(&candidate->link);
142         candidate->usage = 1;
143         candidate->state = AFS_WBACK_PENDING;
144         init_waitqueue_head(&candidate->waitq);
145
146         page = grab_cache_page_write_begin(mapping, index, flags);
147         if (!page) {
148                 kfree(candidate);
149                 return -ENOMEM;
150         }
151
152         if (!PageUptodate(page) && len != PAGE_SIZE) {
153                 ret = afs_fill_page(vnode, key, index << PAGE_SHIFT, page);
154                 if (ret < 0) {
155                         unlock_page(page);
156                         put_page(page);
157                         kfree(candidate);
158                         _leave(" = %d [prep]", ret);
159                         return ret;
160                 }
161                 SetPageUptodate(page);
162         }
163
164         /* page won't leak in error case: it eventually gets cleaned off LRU */
165         *pagep = page;
166
167 try_again:
168         spin_lock(&vnode->writeback_lock);
169
170         /* see if this page is already pending a writeback under a suitable key
171          * - if so we can just join onto that one */
172         wb = (struct afs_writeback *) page_private(page);
173         if (wb) {
174                 if (wb->key == key && wb->state == AFS_WBACK_PENDING)
175                         goto subsume_in_current_wb;
176                 goto flush_conflicting_wb;
177         }
178
179         if (index > 0) {
180                 /* see if we can find an already pending writeback that we can
181                  * append this page to */
182                 list_for_each_entry(wb, &vnode->writebacks, link) {
183                         if (wb->last == index - 1 && wb->key == key &&
184                             wb->state == AFS_WBACK_PENDING)
185                                 goto append_to_previous_wb;
186                 }
187         }
188
189         list_add_tail(&candidate->link, &vnode->writebacks);
190         candidate->key = key_get(key);
191         spin_unlock(&vnode->writeback_lock);
192         SetPagePrivate(page);
193         set_page_private(page, (unsigned long) candidate);
194         _leave(" = 0 [new]");
195         return 0;
196
197 subsume_in_current_wb:
198         _debug("subsume");
199         ASSERTRANGE(wb->first, <=, index, <=, wb->last);
200         if (index == wb->first && from < wb->offset_first)
201                 wb->offset_first = from;
202         if (index == wb->last && to > wb->to_last)
203                 wb->to_last = to;
204         spin_unlock(&vnode->writeback_lock);
205         kfree(candidate);
206         _leave(" = 0 [sub]");
207         return 0;
208
209 append_to_previous_wb:
210         _debug("append into %lx-%lx", wb->first, wb->last);
211         wb->usage++;
212         wb->last++;
213         wb->to_last = to;
214         spin_unlock(&vnode->writeback_lock);
215         SetPagePrivate(page);
216         set_page_private(page, (unsigned long) wb);
217         kfree(candidate);
218         _leave(" = 0 [app]");
219         return 0;
220
221         /* the page is currently bound to another context, so if it's dirty we
222          * need to flush it before we can use the new context */
223 flush_conflicting_wb:
224         _debug("flush conflict");
225         if (wb->state == AFS_WBACK_PENDING)
226                 wb->state = AFS_WBACK_CONFLICTING;
227         spin_unlock(&vnode->writeback_lock);
228         if (PageDirty(page)) {
229                 ret = afs_write_back_from_locked_page(wb, page);
230                 if (ret < 0) {
231                         afs_put_writeback(candidate);
232                         _leave(" = %d", ret);
233                         return ret;
234                 }
235         }
236
237         /* the page holds a ref on the writeback record */
238         afs_put_writeback(wb);
239         set_page_private(page, 0);
240         ClearPagePrivate(page);
241         goto try_again;
242 }
243
244 /*
245  * finalise part of a write to a page
246  */
247 int afs_write_end(struct file *file, struct address_space *mapping,
248                   loff_t pos, unsigned len, unsigned copied,
249                   struct page *page, void *fsdata)
250 {
251         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
252         loff_t i_size, maybe_i_size;
253
254         _enter("{%x:%u},{%lx}",
255                vnode->fid.vid, vnode->fid.vnode, page->index);
256
257         maybe_i_size = pos + copied;
258
259         i_size = i_size_read(&vnode->vfs_inode);
260         if (maybe_i_size > i_size) {
261                 spin_lock(&vnode->writeback_lock);
262                 i_size = i_size_read(&vnode->vfs_inode);
263                 if (maybe_i_size > i_size)
264                         i_size_write(&vnode->vfs_inode, maybe_i_size);
265                 spin_unlock(&vnode->writeback_lock);
266         }
267
268         set_page_dirty(page);
269         if (PageDirty(page))
270                 _debug("dirtied");
271         unlock_page(page);
272         put_page(page);
273
274         return copied;
275 }
276
277 /*
278  * kill all the pages in the given range
279  */
280 static void afs_kill_pages(struct afs_vnode *vnode, bool error,
281                            pgoff_t first, pgoff_t last)
282 {
283         struct pagevec pv;
284         unsigned count, loop;
285
286         _enter("{%x:%u},%lx-%lx",
287                vnode->fid.vid, vnode->fid.vnode, first, last);
288
289         pagevec_init(&pv, 0);
290
291         do {
292                 _debug("kill %lx-%lx", first, last);
293
294                 count = last - first + 1;
295                 if (count > PAGEVEC_SIZE)
296                         count = PAGEVEC_SIZE;
297                 pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
298                                               first, count, pv.pages);
299                 ASSERTCMP(pv.nr, ==, count);
300
301                 for (loop = 0; loop < count; loop++) {
302                         struct page *page = pv.pages[loop];
303                         ClearPageUptodate(page);
304                         if (error)
305                                 SetPageError(page);
306                         if (PageWriteback(page))
307                                 end_page_writeback(page);
308                         if (page->index >= first)
309                                 first = page->index + 1;
310                 }
311
312                 __pagevec_release(&pv);
313         } while (first < last);
314
315         _leave("");
316 }
317
318 /*
319  * synchronously write back the locked page and any subsequent non-locked dirty
320  * pages also covered by the same writeback record
321  */
322 static int afs_write_back_from_locked_page(struct afs_writeback *wb,
323                                            struct page *primary_page)
324 {
325         struct page *pages[8], *page;
326         unsigned long count;
327         unsigned n, offset, to;
328         pgoff_t start, first, last;
329         int loop, ret;
330
331         _enter(",%lx", primary_page->index);
332
333         count = 1;
334         if (!clear_page_dirty_for_io(primary_page))
335                 BUG();
336         if (test_set_page_writeback(primary_page))
337                 BUG();
338
339         /* find all consecutive lockable dirty pages, stopping when we find a
340          * page that is not immediately lockable, is not dirty or is missing,
341          * or we reach the end of the range */
342         start = primary_page->index;
343         if (start >= wb->last)
344                 goto no_more;
345         start++;
346         do {
347                 _debug("more %lx [%lx]", start, count);
348                 n = wb->last - start + 1;
349                 if (n > ARRAY_SIZE(pages))
350                         n = ARRAY_SIZE(pages);
351                 n = find_get_pages_contig(wb->vnode->vfs_inode.i_mapping,
352                                           start, n, pages);
353                 _debug("fgpc %u", n);
354                 if (n == 0)
355                         goto no_more;
356                 if (pages[0]->index != start) {
357                         do {
358                                 put_page(pages[--n]);
359                         } while (n > 0);
360                         goto no_more;
361                 }
362
363                 for (loop = 0; loop < n; loop++) {
364                         page = pages[loop];
365                         if (page->index > wb->last)
366                                 break;
367                         if (!trylock_page(page))
368                                 break;
369                         if (!PageDirty(page) ||
370                             page_private(page) != (unsigned long) wb) {
371                                 unlock_page(page);
372                                 break;
373                         }
374                         if (!clear_page_dirty_for_io(page))
375                                 BUG();
376                         if (test_set_page_writeback(page))
377                                 BUG();
378                         unlock_page(page);
379                         put_page(page);
380                 }
381                 count += loop;
382                 if (loop < n) {
383                         for (; loop < n; loop++)
384                                 put_page(pages[loop]);
385                         goto no_more;
386                 }
387
388                 start += loop;
389         } while (start <= wb->last && count < 65536);
390
391 no_more:
392         /* we now have a contiguous set of dirty pages, each with writeback set
393          * and the dirty mark cleared; the first page is locked and must remain
394          * so, all the rest are unlocked */
395         first = primary_page->index;
396         last = first + count - 1;
397
398         offset = (first == wb->first) ? wb->offset_first : 0;
399         to = (last == wb->last) ? wb->to_last : PAGE_SIZE;
400
401         _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
402
403         ret = afs_vnode_store_data(wb, first, last, offset, to);
404         if (ret < 0) {
405                 switch (ret) {
406                 case -EDQUOT:
407                 case -ENOSPC:
408                         mapping_set_error(wb->vnode->vfs_inode.i_mapping, -ENOSPC);
409                         break;
410                 case -EROFS:
411                 case -EIO:
412                 case -EREMOTEIO:
413                 case -EFBIG:
414                 case -ENOENT:
415                 case -ENOMEDIUM:
416                 case -ENXIO:
417                         afs_kill_pages(wb->vnode, true, first, last);
418                         mapping_set_error(wb->vnode->vfs_inode.i_mapping, -EIO);
419                         break;
420                 case -EACCES:
421                 case -EPERM:
422                 case -ENOKEY:
423                 case -EKEYEXPIRED:
424                 case -EKEYREJECTED:
425                 case -EKEYREVOKED:
426                         afs_kill_pages(wb->vnode, false, first, last);
427                         break;
428                 default:
429                         break;
430                 }
431         } else {
432                 ret = count;
433         }
434
435         _leave(" = %d", ret);
436         return ret;
437 }
438
439 /*
440  * write a page back to the server
441  * - the caller locked the page for us
442  */
443 int afs_writepage(struct page *page, struct writeback_control *wbc)
444 {
445         struct afs_writeback *wb;
446         int ret;
447
448         _enter("{%lx},", page->index);
449
450         wb = (struct afs_writeback *) page_private(page);
451         ASSERT(wb != NULL);
452
453         ret = afs_write_back_from_locked_page(wb, page);
454         unlock_page(page);
455         if (ret < 0) {
456                 _leave(" = %d", ret);
457                 return 0;
458         }
459
460         wbc->nr_to_write -= ret;
461
462         _leave(" = 0");
463         return 0;
464 }
465
466 /*
467  * write a region of pages back to the server
468  */
469 static int afs_writepages_region(struct address_space *mapping,
470                                  struct writeback_control *wbc,
471                                  pgoff_t index, pgoff_t end, pgoff_t *_next)
472 {
473         struct afs_writeback *wb;
474         struct page *page;
475         int ret, n;
476
477         _enter(",,%lx,%lx,", index, end);
478
479         do {
480                 n = find_get_pages_tag(mapping, &index, PAGECACHE_TAG_DIRTY,
481                                        1, &page);
482                 if (!n)
483                         break;
484
485                 _debug("wback %lx", page->index);
486
487                 if (page->index > end) {
488                         *_next = index;
489                         put_page(page);
490                         _leave(" = 0 [%lx]", *_next);
491                         return 0;
492                 }
493
494                 /* at this point we hold neither mapping->tree_lock nor lock on
495                  * the page itself: the page may be truncated or invalidated
496                  * (changing page->mapping to NULL), or even swizzled back from
497                  * swapper_space to tmpfs file mapping
498                  */
499                 lock_page(page);
500
501                 if (page->mapping != mapping) {
502                         unlock_page(page);
503                         put_page(page);
504                         continue;
505                 }
506
507                 if (wbc->sync_mode != WB_SYNC_NONE)
508                         wait_on_page_writeback(page);
509
510                 if (PageWriteback(page) || !PageDirty(page)) {
511                         unlock_page(page);
512                         put_page(page);
513                         continue;
514                 }
515
516                 wb = (struct afs_writeback *) page_private(page);
517                 ASSERT(wb != NULL);
518
519                 spin_lock(&wb->vnode->writeback_lock);
520                 wb->state = AFS_WBACK_WRITING;
521                 spin_unlock(&wb->vnode->writeback_lock);
522
523                 ret = afs_write_back_from_locked_page(wb, page);
524                 unlock_page(page);
525                 put_page(page);
526                 if (ret < 0) {
527                         _leave(" = %d", ret);
528                         return ret;
529                 }
530
531                 wbc->nr_to_write -= ret;
532
533                 cond_resched();
534         } while (index < end && wbc->nr_to_write > 0);
535
536         *_next = index;
537         _leave(" = 0 [%lx]", *_next);
538         return 0;
539 }
540
541 /*
542  * write some of the pending data back to the server
543  */
544 int afs_writepages(struct address_space *mapping,
545                    struct writeback_control *wbc)
546 {
547         pgoff_t start, end, next;
548         int ret;
549
550         _enter("");
551
552         if (wbc->range_cyclic) {
553                 start = mapping->writeback_index;
554                 end = -1;
555                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
556                 if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
557                         ret = afs_writepages_region(mapping, wbc, 0, start,
558                                                     &next);
559                 mapping->writeback_index = next;
560         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
561                 end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT);
562                 ret = afs_writepages_region(mapping, wbc, 0, end, &next);
563                 if (wbc->nr_to_write > 0)
564                         mapping->writeback_index = next;
565         } else {
566                 start = wbc->range_start >> PAGE_SHIFT;
567                 end = wbc->range_end >> PAGE_SHIFT;
568                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
569         }
570
571         _leave(" = %d", ret);
572         return ret;
573 }
574
575 /*
576  * completion of write to server
577  */
578 void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
579 {
580         struct afs_writeback *wb = call->wb;
581         struct pagevec pv;
582         unsigned count, loop;
583         pgoff_t first = call->first, last = call->last;
584         bool free_wb;
585
586         _enter("{%x:%u},{%lx-%lx}",
587                vnode->fid.vid, vnode->fid.vnode, first, last);
588
589         ASSERT(wb != NULL);
590
591         pagevec_init(&pv, 0);
592
593         do {
594                 _debug("done %lx-%lx", first, last);
595
596                 count = last - first + 1;
597                 if (count > PAGEVEC_SIZE)
598                         count = PAGEVEC_SIZE;
599                 pv.nr = find_get_pages_contig(call->mapping, first, count,
600                                               pv.pages);
601                 ASSERTCMP(pv.nr, ==, count);
602
603                 spin_lock(&vnode->writeback_lock);
604                 for (loop = 0; loop < count; loop++) {
605                         struct page *page = pv.pages[loop];
606                         end_page_writeback(page);
607                         if (page_private(page) == (unsigned long) wb) {
608                                 set_page_private(page, 0);
609                                 ClearPagePrivate(page);
610                                 wb->usage--;
611                         }
612                 }
613                 free_wb = false;
614                 if (wb->usage == 0) {
615                         afs_unlink_writeback(wb);
616                         free_wb = true;
617                 }
618                 spin_unlock(&vnode->writeback_lock);
619                 first += count;
620                 if (free_wb) {
621                         afs_free_writeback(wb);
622                         wb = NULL;
623                 }
624
625                 __pagevec_release(&pv);
626         } while (first <= last);
627
628         _leave("");
629 }
630
631 /*
632  * write to an AFS file
633  */
634 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
635 {
636         struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
637         ssize_t result;
638         size_t count = iov_iter_count(from);
639
640         _enter("{%x.%u},{%zu},",
641                vnode->fid.vid, vnode->fid.vnode, count);
642
643         if (IS_SWAPFILE(&vnode->vfs_inode)) {
644                 printk(KERN_INFO
645                        "AFS: Attempt to write to active swap file!\n");
646                 return -EBUSY;
647         }
648
649         if (!count)
650                 return 0;
651
652         result = generic_file_write_iter(iocb, from);
653
654         _leave(" = %zd", result);
655         return result;
656 }
657
658 /*
659  * flush the vnode to the fileserver
660  */
661 int afs_writeback_all(struct afs_vnode *vnode)
662 {
663         struct address_space *mapping = vnode->vfs_inode.i_mapping;
664         struct writeback_control wbc = {
665                 .sync_mode      = WB_SYNC_ALL,
666                 .nr_to_write    = LONG_MAX,
667                 .range_cyclic   = 1,
668         };
669         int ret;
670
671         _enter("");
672
673         ret = mapping->a_ops->writepages(mapping, &wbc);
674         __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
675
676         _leave(" = %d", ret);
677         return ret;
678 }
679
680 /*
681  * flush any dirty pages for this process, and check for write errors.
682  * - the return status from this call provides a reliable indication of
683  *   whether any write errors occurred for this process.
684  */
685 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
686 {
687         struct inode *inode = file_inode(file);
688         struct afs_writeback *wb, *xwb;
689         struct afs_vnode *vnode = AFS_FS_I(inode);
690         int ret;
691
692         _enter("{%x:%u},{n=%pD},%d",
693                vnode->fid.vid, vnode->fid.vnode, file,
694                datasync);
695
696         ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
697         if (ret)
698                 return ret;
699         inode_lock(inode);
700
701         /* use a writeback record as a marker in the queue - when this reaches
702          * the front of the queue, all the outstanding writes are either
703          * completed or rejected */
704         wb = kzalloc(sizeof(*wb), GFP_KERNEL);
705         if (!wb) {
706                 ret = -ENOMEM;
707                 goto out;
708         }
709         wb->vnode = vnode;
710         wb->first = 0;
711         wb->last = -1;
712         wb->offset_first = 0;
713         wb->to_last = PAGE_SIZE;
714         wb->usage = 1;
715         wb->state = AFS_WBACK_SYNCING;
716         init_waitqueue_head(&wb->waitq);
717
718         spin_lock(&vnode->writeback_lock);
719         list_for_each_entry(xwb, &vnode->writebacks, link) {
720                 if (xwb->state == AFS_WBACK_PENDING)
721                         xwb->state = AFS_WBACK_CONFLICTING;
722         }
723         list_add_tail(&wb->link, &vnode->writebacks);
724         spin_unlock(&vnode->writeback_lock);
725
726         /* push all the outstanding writebacks to the server */
727         ret = afs_writeback_all(vnode);
728         if (ret < 0) {
729                 afs_put_writeback(wb);
730                 _leave(" = %d [wb]", ret);
731                 goto out;
732         }
733
734         /* wait for the preceding writes to actually complete */
735         ret = wait_event_interruptible(wb->waitq,
736                                        wb->state == AFS_WBACK_COMPLETE ||
737                                        vnode->writebacks.next == &wb->link);
738         afs_put_writeback(wb);
739         _leave(" = %d", ret);
740 out:
741         inode_unlock(inode);
742         return ret;
743 }
744
745 /*
746  * Flush out all outstanding writes on a file opened for writing when it is
747  * closed.
748  */
749 int afs_flush(struct file *file, fl_owner_t id)
750 {
751         _enter("");
752
753         if ((file->f_mode & FMODE_WRITE) == 0)
754                 return 0;
755
756         return vfs_fsync(file, 0);
757 }
758
759 /*
760  * notification that a previously read-only page is about to become writable
761  * - if it returns an error, the caller will deliver a bus error signal
762  */
763 int afs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
764 {
765         struct afs_vnode *vnode = AFS_FS_I(vma->vm_file->f_mapping->host);
766
767         _enter("{{%x:%u}},{%lx}",
768                vnode->fid.vid, vnode->fid.vnode, page->index);
769
770         /* wait for the page to be written to the cache before we allow it to
771          * be modified */
772 #ifdef CONFIG_AFS_FSCACHE
773         fscache_wait_on_page_write(vnode->cache, page);
774 #endif
775
776         _leave(" = 0");
777         return 0;
778 }