AFS: Fix afs_prepare_write()
[linux-2.6.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
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                          unsigned start, unsigned len, struct page *page)
88 {
89         int ret;
90
91         _enter(",,%u,%u", start, len);
92
93         ASSERTCMP(start + len, <=, PAGE_SIZE);
94
95         ret = afs_vnode_fetch_data(vnode, key, start, len, page);
96         if (ret < 0) {
97                 if (ret == -ENOENT) {
98                         _debug("got NOENT from server"
99                                " - marking file deleted and stale");
100                         set_bit(AFS_VNODE_DELETED, &vnode->flags);
101                         ret = -ESTALE;
102                 }
103         }
104
105         _leave(" = %d", ret);
106         return ret;
107 }
108
109 /*
110  * prepare a page for being written to
111  */
112 static int afs_prepare_page(struct afs_vnode *vnode, struct page *page,
113                             struct key *key, unsigned offset, unsigned to)
114 {
115         unsigned eof, tail, start, stop, len;
116         loff_t i_size, pos;
117         void *p;
118         int ret;
119
120         _enter("");
121
122         if (offset == 0 && to == PAGE_SIZE)
123                 return 0;
124
125         p = kmap_atomic(page, KM_USER0);
126
127         i_size = i_size_read(&vnode->vfs_inode);
128         pos = (loff_t) page->index << PAGE_SHIFT;
129         if (pos >= i_size) {
130                 /* partial write, page beyond EOF */
131                 _debug("beyond");
132                 if (offset > 0)
133                         memset(p, 0, offset);
134                 if (to < PAGE_SIZE)
135                         memset(p + to, 0, PAGE_SIZE - to);
136                 kunmap_atomic(p, KM_USER0);
137                 return 0;
138         }
139
140         if (i_size - pos >= PAGE_SIZE) {
141                 /* partial write, page entirely before EOF */
142                 _debug("before");
143                 tail = eof = PAGE_SIZE;
144         } else {
145                 /* partial write, page overlaps EOF */
146                 eof = i_size - pos;
147                 _debug("overlap %u", eof);
148                 tail = max(eof, to);
149                 if (tail < PAGE_SIZE)
150                         memset(p + tail, 0, PAGE_SIZE - tail);
151                 if (offset > eof)
152                         memset(p + eof, 0, PAGE_SIZE - eof);
153         }
154
155         kunmap_atomic(p, KM_USER0);
156
157         ret = 0;
158         if (offset > 0 || eof > to) {
159                 /* need to fill one or two bits that aren't going to be written
160                  * (cover both fillers in one read if there are two) */
161                 start = (offset > 0) ? 0 : to;
162                 stop = (eof > to) ? eof : offset;
163                 len = stop - start;
164                 _debug("wr=%u-%u av=0-%u rd=%u@%u",
165                        offset, to, eof, start, len);
166                 ret = afs_fill_page(vnode, key, start, len, page);
167         }
168
169         _leave(" = %d", ret);
170         return ret;
171 }
172
173 /*
174  * prepare to perform part of a write to a page
175  * - the caller holds the page locked, preventing it from being written out or
176  *   modified by anyone else
177  */
178 int afs_prepare_write(struct file *file, struct page *page,
179                       unsigned offset, unsigned to)
180 {
181         struct afs_writeback *candidate, *wb;
182         struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
183         struct key *key = file->private_data;
184         pgoff_t index;
185         int ret;
186
187         _enter("{%x:%u},{%lx},%u,%u",
188                vnode->fid.vid, vnode->fid.vnode, page->index, offset, to);
189
190         candidate = kzalloc(sizeof(*candidate), GFP_KERNEL);
191         if (!candidate)
192                 return -ENOMEM;
193         candidate->vnode = vnode;
194         candidate->first = candidate->last = page->index;
195         candidate->offset_first = offset;
196         candidate->to_last = to;
197         candidate->usage = 1;
198         candidate->state = AFS_WBACK_PENDING;
199         init_waitqueue_head(&candidate->waitq);
200
201         if (!PageUptodate(page)) {
202                 _debug("not up to date");
203                 ret = afs_prepare_page(vnode, page, key, offset, to);
204                 if (ret < 0) {
205                         kfree(candidate);
206                         _leave(" = %d [prep]", ret);
207                         return ret;
208                 }
209         }
210
211 try_again:
212         index = page->index;
213         spin_lock(&vnode->writeback_lock);
214
215         /* see if this page is already pending a writeback under a suitable key
216          * - if so we can just join onto that one */
217         wb = (struct afs_writeback *) page_private(page);
218         if (wb) {
219                 if (wb->key == key && wb->state == AFS_WBACK_PENDING)
220                         goto subsume_in_current_wb;
221                 goto flush_conflicting_wb;
222         }
223
224         if (index > 0) {
225                 /* see if we can find an already pending writeback that we can
226                  * append this page to */
227                 list_for_each_entry(wb, &vnode->writebacks, link) {
228                         if (wb->last == index - 1 && wb->key == key &&
229                             wb->state == AFS_WBACK_PENDING)
230                                 goto append_to_previous_wb;
231                 }
232         }
233
234         list_add_tail(&candidate->link, &vnode->writebacks);
235         candidate->key = key_get(key);
236         spin_unlock(&vnode->writeback_lock);
237         SetPagePrivate(page);
238         set_page_private(page, (unsigned long) candidate);
239         _leave(" = 0 [new]");
240         return 0;
241
242 subsume_in_current_wb:
243         _debug("subsume");
244         ASSERTRANGE(wb->first, <=, index, <=, wb->last);
245         if (index == wb->first && offset < wb->offset_first)
246                 wb->offset_first = offset;
247         if (index == wb->last && to > wb->to_last)
248                 wb->to_last = to;
249         spin_unlock(&vnode->writeback_lock);
250         kfree(candidate);
251         _leave(" = 0 [sub]");
252         return 0;
253
254 append_to_previous_wb:
255         _debug("append into %lx-%lx", wb->first, wb->last);
256         wb->usage++;
257         wb->last++;
258         wb->to_last = to;
259         spin_unlock(&vnode->writeback_lock);
260         SetPagePrivate(page);
261         set_page_private(page, (unsigned long) wb);
262         kfree(candidate);
263         _leave(" = 0 [app]");
264         return 0;
265
266         /* the page is currently bound to another context, so if it's dirty we
267          * need to flush it before we can use the new context */
268 flush_conflicting_wb:
269         _debug("flush conflict");
270         if (wb->state == AFS_WBACK_PENDING)
271                 wb->state = AFS_WBACK_CONFLICTING;
272         spin_unlock(&vnode->writeback_lock);
273         if (PageDirty(page)) {
274                 ret = afs_write_back_from_locked_page(wb, page);
275                 if (ret < 0) {
276                         afs_put_writeback(candidate);
277                         _leave(" = %d", ret);
278                         return ret;
279                 }
280         }
281
282         /* the page holds a ref on the writeback record */
283         afs_put_writeback(wb);
284         set_page_private(page, 0);
285         ClearPagePrivate(page);
286         goto try_again;
287 }
288
289 /*
290  * finalise part of a write to a page
291  */
292 int afs_commit_write(struct file *file, struct page *page,
293                      unsigned offset, unsigned to)
294 {
295         struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
296         loff_t i_size, maybe_i_size;
297
298         _enter("{%x:%u},{%lx},%u,%u",
299                vnode->fid.vid, vnode->fid.vnode, page->index, offset, to);
300
301         maybe_i_size = (loff_t) page->index << PAGE_SHIFT;
302         maybe_i_size += to;
303
304         i_size = i_size_read(&vnode->vfs_inode);
305         if (maybe_i_size > i_size) {
306                 spin_lock(&vnode->writeback_lock);
307                 i_size = i_size_read(&vnode->vfs_inode);
308                 if (maybe_i_size > i_size)
309                         i_size_write(&vnode->vfs_inode, maybe_i_size);
310                 spin_unlock(&vnode->writeback_lock);
311         }
312
313         SetPageUptodate(page);
314         set_page_dirty(page);
315         if (PageDirty(page))
316                 _debug("dirtied");
317
318         return 0;
319 }
320
321 /*
322  * kill all the pages in the given range
323  */
324 static void afs_kill_pages(struct afs_vnode *vnode, bool error,
325                            pgoff_t first, pgoff_t last)
326 {
327         struct pagevec pv;
328         unsigned count, loop;
329
330         _enter("{%x:%u},%lx-%lx",
331                vnode->fid.vid, vnode->fid.vnode, first, last);
332
333         pagevec_init(&pv, 0);
334
335         do {
336                 _debug("kill %lx-%lx", first, last);
337
338                 count = last - first + 1;
339                 if (count > PAGEVEC_SIZE)
340                         count = PAGEVEC_SIZE;
341                 pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
342                                               first, count, pv.pages);
343                 ASSERTCMP(pv.nr, ==, count);
344
345                 for (loop = 0; loop < count; loop++) {
346                         ClearPageUptodate(pv.pages[loop]);
347                         if (error)
348                                 SetPageError(pv.pages[loop]);
349                         end_page_writeback(pv.pages[loop]);
350                 }
351
352                 __pagevec_release(&pv);
353         } while (first < last);
354
355         _leave("");
356 }
357
358 /*
359  * synchronously write back the locked page and any subsequent non-locked dirty
360  * pages also covered by the same writeback record
361  */
362 static int afs_write_back_from_locked_page(struct afs_writeback *wb,
363                                            struct page *primary_page)
364 {
365         struct page *pages[8], *page;
366         unsigned long count;
367         unsigned n, offset, to;
368         pgoff_t start, first, last;
369         int loop, ret;
370
371         _enter(",%lx", primary_page->index);
372
373         count = 1;
374         if (!clear_page_dirty_for_io(primary_page))
375                 BUG();
376         if (test_set_page_writeback(primary_page))
377                 BUG();
378
379         /* find all consecutive lockable dirty pages, stopping when we find a
380          * page that is not immediately lockable, is not dirty or is missing,
381          * or we reach the end of the range */
382         start = primary_page->index;
383         if (start >= wb->last)
384                 goto no_more;
385         start++;
386         do {
387                 _debug("more %lx [%lx]", start, count);
388                 n = wb->last - start + 1;
389                 if (n > ARRAY_SIZE(pages))
390                         n = ARRAY_SIZE(pages);
391                 n = find_get_pages_contig(wb->vnode->vfs_inode.i_mapping,
392                                           start, n, pages);
393                 _debug("fgpc %u", n);
394                 if (n == 0)
395                         goto no_more;
396                 if (pages[0]->index != start) {
397                         do {
398                                 put_page(pages[--n]);
399                         } while (n > 0);
400                         goto no_more;
401                 }
402
403                 for (loop = 0; loop < n; loop++) {
404                         page = pages[loop];
405                         if (page->index > wb->last)
406                                 break;
407                         if (TestSetPageLocked(page))
408                                 break;
409                         if (!PageDirty(page) ||
410                             page_private(page) != (unsigned long) wb) {
411                                 unlock_page(page);
412                                 break;
413                         }
414                         if (!clear_page_dirty_for_io(page))
415                                 BUG();
416                         if (test_set_page_writeback(page))
417                                 BUG();
418                         unlock_page(page);
419                         put_page(page);
420                 }
421                 count += loop;
422                 if (loop < n) {
423                         for (; loop < n; loop++)
424                                 put_page(pages[loop]);
425                         goto no_more;
426                 }
427
428                 start += loop;
429         } while (start <= wb->last && count < 65536);
430
431 no_more:
432         /* we now have a contiguous set of dirty pages, each with writeback set
433          * and the dirty mark cleared; the first page is locked and must remain
434          * so, all the rest are unlocked */
435         first = primary_page->index;
436         last = first + count - 1;
437
438         offset = (first == wb->first) ? wb->offset_first : 0;
439         to = (last == wb->last) ? wb->to_last : PAGE_SIZE;
440
441         _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
442
443         ret = afs_vnode_store_data(wb, first, last, offset, to);
444         if (ret < 0) {
445                 switch (ret) {
446                 case -EDQUOT:
447                 case -ENOSPC:
448                         set_bit(AS_ENOSPC,
449                                 &wb->vnode->vfs_inode.i_mapping->flags);
450                         break;
451                 case -EROFS:
452                 case -EIO:
453                 case -EREMOTEIO:
454                 case -EFBIG:
455                 case -ENOENT:
456                 case -ENOMEDIUM:
457                 case -ENXIO:
458                         afs_kill_pages(wb->vnode, true, first, last);
459                         set_bit(AS_EIO, &wb->vnode->vfs_inode.i_mapping->flags);
460                         break;
461                 case -EACCES:
462                 case -EPERM:
463                 case -ENOKEY:
464                 case -EKEYEXPIRED:
465                 case -EKEYREJECTED:
466                 case -EKEYREVOKED:
467                         afs_kill_pages(wb->vnode, false, first, last);
468                         break;
469                 default:
470                         break;
471                 }
472         } else {
473                 ret = count;
474         }
475
476         _leave(" = %d", ret);
477         return ret;
478 }
479
480 /*
481  * write a page back to the server
482  * - the caller locked the page for us
483  */
484 int afs_writepage(struct page *page, struct writeback_control *wbc)
485 {
486         struct backing_dev_info *bdi = page->mapping->backing_dev_info;
487         struct afs_writeback *wb;
488         int ret;
489
490         _enter("{%lx},", page->index);
491
492         wb = (struct afs_writeback *) page_private(page);
493         ASSERT(wb != NULL);
494
495         ret = afs_write_back_from_locked_page(wb, page);
496         unlock_page(page);
497         if (ret < 0) {
498                 _leave(" = %d", ret);
499                 return 0;
500         }
501
502         wbc->nr_to_write -= ret;
503         if (wbc->nonblocking && bdi_write_congested(bdi))
504                 wbc->encountered_congestion = 1;
505
506         _leave(" = 0");
507         return 0;
508 }
509
510 /*
511  * write a region of pages back to the server
512  */
513 int afs_writepages_region(struct address_space *mapping,
514                           struct writeback_control *wbc,
515                           pgoff_t index, pgoff_t end, pgoff_t *_next)
516 {
517         struct backing_dev_info *bdi = mapping->backing_dev_info;
518         struct afs_writeback *wb;
519         struct page *page;
520         int ret, n;
521
522         _enter(",,%lx,%lx,", index, end);
523
524         do {
525                 n = find_get_pages_tag(mapping, &index, PAGECACHE_TAG_DIRTY,
526                                        1, &page);
527                 if (!n)
528                         break;
529
530                 _debug("wback %lx", page->index);
531
532                 if (page->index > end) {
533                         *_next = index;
534                         page_cache_release(page);
535                         _leave(" = 0 [%lx]", *_next);
536                         return 0;
537                 }
538
539                 /* at this point we hold neither mapping->tree_lock nor lock on
540                  * the page itself: the page may be truncated or invalidated
541                  * (changing page->mapping to NULL), or even swizzled back from
542                  * swapper_space to tmpfs file mapping
543                  */
544                 lock_page(page);
545
546                 if (page->mapping != mapping) {
547                         unlock_page(page);
548                         page_cache_release(page);
549                         continue;
550                 }
551
552                 if (wbc->sync_mode != WB_SYNC_NONE)
553                         wait_on_page_writeback(page);
554
555                 if (PageWriteback(page) || !PageDirty(page)) {
556                         unlock_page(page);
557                         continue;
558                 }
559
560                 wb = (struct afs_writeback *) page_private(page);
561                 ASSERT(wb != NULL);
562
563                 spin_lock(&wb->vnode->writeback_lock);
564                 wb->state = AFS_WBACK_WRITING;
565                 spin_unlock(&wb->vnode->writeback_lock);
566
567                 ret = afs_write_back_from_locked_page(wb, page);
568                 unlock_page(page);
569                 page_cache_release(page);
570                 if (ret < 0) {
571                         _leave(" = %d", ret);
572                         return ret;
573                 }
574
575                 wbc->nr_to_write -= ret;
576
577                 if (wbc->nonblocking && bdi_write_congested(bdi)) {
578                         wbc->encountered_congestion = 1;
579                         break;
580                 }
581
582                 cond_resched();
583         } while (index < end && wbc->nr_to_write > 0);
584
585         *_next = index;
586         _leave(" = 0 [%lx]", *_next);
587         return 0;
588 }
589
590 /*
591  * write some of the pending data back to the server
592  */
593 int afs_writepages(struct address_space *mapping,
594                    struct writeback_control *wbc)
595 {
596         struct backing_dev_info *bdi = mapping->backing_dev_info;
597         pgoff_t start, end, next;
598         int ret;
599
600         _enter("");
601
602         if (wbc->nonblocking && bdi_write_congested(bdi)) {
603                 wbc->encountered_congestion = 1;
604                 _leave(" = 0 [congest]");
605                 return 0;
606         }
607
608         if (wbc->range_cyclic) {
609                 start = mapping->writeback_index;
610                 end = -1;
611                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
612                 if (start > 0 && wbc->nr_to_write > 0 && ret == 0 &&
613                     !(wbc->nonblocking && wbc->encountered_congestion))
614                         ret = afs_writepages_region(mapping, wbc, 0, start,
615                                                     &next);
616                 mapping->writeback_index = next;
617         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
618                 end = (pgoff_t)(LLONG_MAX >> PAGE_CACHE_SHIFT);
619                 ret = afs_writepages_region(mapping, wbc, 0, end, &next);
620                 if (wbc->nr_to_write > 0)
621                         mapping->writeback_index = next;
622         } else {
623                 start = wbc->range_start >> PAGE_CACHE_SHIFT;
624                 end = wbc->range_end >> PAGE_CACHE_SHIFT;
625                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
626         }
627
628         _leave(" = %d", ret);
629         return ret;
630 }
631
632 /*
633  * write an inode back
634  */
635 int afs_write_inode(struct inode *inode, int sync)
636 {
637         struct afs_vnode *vnode = AFS_FS_I(inode);
638         int ret;
639
640         _enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);
641
642         ret = 0;
643         if (sync) {
644                 ret = filemap_fdatawait(inode->i_mapping);
645                 if (ret < 0)
646                         __mark_inode_dirty(inode, I_DIRTY_DATASYNC);
647         }
648
649         _leave(" = %d", ret);
650         return ret;
651 }
652
653 /*
654  * completion of write to server
655  */
656 void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
657 {
658         struct afs_writeback *wb = call->wb;
659         struct pagevec pv;
660         unsigned count, loop;
661         pgoff_t first = call->first, last = call->last;
662         bool free_wb;
663
664         _enter("{%x:%u},{%lx-%lx}",
665                vnode->fid.vid, vnode->fid.vnode, first, last);
666
667         ASSERT(wb != NULL);
668
669         pagevec_init(&pv, 0);
670
671         do {
672                 _debug("done %lx-%lx", first, last);
673
674                 count = last - first + 1;
675                 if (count > PAGEVEC_SIZE)
676                         count = PAGEVEC_SIZE;
677                 pv.nr = find_get_pages_contig(call->mapping, first, count,
678                                               pv.pages);
679                 ASSERTCMP(pv.nr, ==, count);
680
681                 spin_lock(&vnode->writeback_lock);
682                 for (loop = 0; loop < count; loop++) {
683                         struct page *page = pv.pages[loop];
684                         end_page_writeback(page);
685                         if (page_private(page) == (unsigned long) wb) {
686                                 set_page_private(page, 0);
687                                 ClearPagePrivate(page);
688                                 wb->usage--;
689                         }
690                 }
691                 free_wb = false;
692                 if (wb->usage == 0) {
693                         afs_unlink_writeback(wb);
694                         free_wb = true;
695                 }
696                 spin_unlock(&vnode->writeback_lock);
697                 first += count;
698                 if (free_wb) {
699                         afs_free_writeback(wb);
700                         wb = NULL;
701                 }
702
703                 __pagevec_release(&pv);
704         } while (first <= last);
705
706         _leave("");
707 }
708
709 /*
710  * write to an AFS file
711  */
712 ssize_t afs_file_write(struct kiocb *iocb, const struct iovec *iov,
713                        unsigned long nr_segs, loff_t pos)
714 {
715         struct dentry *dentry = iocb->ki_filp->f_path.dentry;
716         struct afs_vnode *vnode = AFS_FS_I(dentry->d_inode);
717         ssize_t result;
718         size_t count = iov_length(iov, nr_segs);
719         int ret;
720
721         _enter("{%x.%u},{%zu},%lu,",
722                vnode->fid.vid, vnode->fid.vnode, count, nr_segs);
723
724         if (IS_SWAPFILE(&vnode->vfs_inode)) {
725                 printk(KERN_INFO
726                        "AFS: Attempt to write to active swap file!\n");
727                 return -EBUSY;
728         }
729
730         if (!count)
731                 return 0;
732
733         result = generic_file_aio_write(iocb, iov, nr_segs, pos);
734         if (IS_ERR_VALUE(result)) {
735                 _leave(" = %zd", result);
736                 return result;
737         }
738
739         /* return error values for O_SYNC and IS_SYNC() */
740         if (IS_SYNC(&vnode->vfs_inode) || iocb->ki_filp->f_flags & O_SYNC) {
741                 ret = afs_fsync(iocb->ki_filp, dentry, 1);
742                 if (ret < 0)
743                         result = ret;
744         }
745
746         _leave(" = %zd", result);
747         return result;
748 }
749
750 /*
751  * flush the vnode to the fileserver
752  */
753 int afs_writeback_all(struct afs_vnode *vnode)
754 {
755         struct address_space *mapping = vnode->vfs_inode.i_mapping;
756         struct writeback_control wbc = {
757                 .bdi            = mapping->backing_dev_info,
758                 .sync_mode      = WB_SYNC_ALL,
759                 .nr_to_write    = LONG_MAX,
760                 .for_writepages = 1,
761                 .range_cyclic   = 1,
762         };
763         int ret;
764
765         _enter("");
766
767         ret = mapping->a_ops->writepages(mapping, &wbc);
768         __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
769
770         _leave(" = %d", ret);
771         return ret;
772 }
773
774 /*
775  * flush any dirty pages for this process, and check for write errors.
776  * - the return status from this call provides a reliable indication of
777  *   whether any write errors occurred for this process.
778  */
779 int afs_fsync(struct file *file, struct dentry *dentry, int datasync)
780 {
781         struct afs_writeback *wb, *xwb;
782         struct afs_vnode *vnode = AFS_FS_I(dentry->d_inode);
783         int ret;
784
785         _enter("{%x:%u},{n=%s},%d",
786                vnode->fid.vid, vnode->fid.vnode, dentry->d_name.name,
787                datasync);
788
789         /* use a writeback record as a marker in the queue - when this reaches
790          * the front of the queue, all the outstanding writes are either
791          * completed or rejected */
792         wb = kzalloc(sizeof(*wb), GFP_KERNEL);
793         if (!wb)
794                 return -ENOMEM;
795         wb->vnode = vnode;
796         wb->first = 0;
797         wb->last = -1;
798         wb->offset_first = 0;
799         wb->to_last = PAGE_SIZE;
800         wb->usage = 1;
801         wb->state = AFS_WBACK_SYNCING;
802         init_waitqueue_head(&wb->waitq);
803
804         spin_lock(&vnode->writeback_lock);
805         list_for_each_entry(xwb, &vnode->writebacks, link) {
806                 if (xwb->state == AFS_WBACK_PENDING)
807                         xwb->state = AFS_WBACK_CONFLICTING;
808         }
809         list_add_tail(&wb->link, &vnode->writebacks);
810         spin_unlock(&vnode->writeback_lock);
811
812         /* push all the outstanding writebacks to the server */
813         ret = afs_writeback_all(vnode);
814         if (ret < 0) {
815                 afs_put_writeback(wb);
816                 _leave(" = %d [wb]", ret);
817                 return ret;
818         }
819
820         /* wait for the preceding writes to actually complete */
821         ret = wait_event_interruptible(wb->waitq,
822                                        wb->state == AFS_WBACK_COMPLETE ||
823                                        vnode->writebacks.next == &wb->link);
824         afs_put_writeback(wb);
825         _leave(" = %d", ret);
826         return ret;
827 }