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Linux/fs/afs/write.c

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

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