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  */
afs_set_page_dirty(struct page * page)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  */
afs_unlink_writeback(struct afs_writeback * wb)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  */
afs_free_writeback(struct afs_writeback * wb)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  */
afs_put_writeback(struct afs_writeback * wb)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  */
afs_fill_page(struct afs_vnode * vnode,struct key * key,loff_t pos,struct page * page)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_CACHE_SIZE > i_size)
97 		len = i_size - pos;
98 	else
99 		len = PAGE_CACHE_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  */
afs_write_begin(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned flags,struct page ** pagep,void ** fsdata)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->f_dentry->d_inode);
124 	struct page *page;
125 	struct key *key = file->private_data;
126 	unsigned from = pos & (PAGE_CACHE_SIZE - 1);
127 	unsigned to = from + len;
128 	pgoff_t index = pos >> PAGE_CACHE_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 	*pagep = page;
152 	/* page won't leak in error case: it eventually gets cleaned off LRU */
153 
154 	if (!PageUptodate(page) && len != PAGE_CACHE_SIZE) {
155 		ret = afs_fill_page(vnode, key, index << PAGE_CACHE_SHIFT, page);
156 		if (ret < 0) {
157 			kfree(candidate);
158 			_leave(" = %d [prep]", ret);
159 			return ret;
160 		}
161 		SetPageUptodate(page);
162 	}
163 
164 try_again:
165 	spin_lock(&vnode->writeback_lock);
166 
167 	/* see if this page is already pending a writeback under a suitable key
168 	 * - if so we can just join onto that one */
169 	wb = (struct afs_writeback *) page_private(page);
170 	if (wb) {
171 		if (wb->key == key && wb->state == AFS_WBACK_PENDING)
172 			goto subsume_in_current_wb;
173 		goto flush_conflicting_wb;
174 	}
175 
176 	if (index > 0) {
177 		/* see if we can find an already pending writeback that we can
178 		 * append this page to */
179 		list_for_each_entry(wb, &vnode->writebacks, link) {
180 			if (wb->last == index - 1 && wb->key == key &&
181 			    wb->state == AFS_WBACK_PENDING)
182 				goto append_to_previous_wb;
183 		}
184 	}
185 
186 	list_add_tail(&candidate->link, &vnode->writebacks);
187 	candidate->key = key_get(key);
188 	spin_unlock(&vnode->writeback_lock);
189 	SetPagePrivate(page);
190 	set_page_private(page, (unsigned long) candidate);
191 	_leave(" = 0 [new]");
192 	return 0;
193 
194 subsume_in_current_wb:
195 	_debug("subsume");
196 	ASSERTRANGE(wb->first, <=, index, <=, wb->last);
197 	if (index == wb->first && from < wb->offset_first)
198 		wb->offset_first = from;
199 	if (index == wb->last && to > wb->to_last)
200 		wb->to_last = to;
201 	spin_unlock(&vnode->writeback_lock);
202 	kfree(candidate);
203 	_leave(" = 0 [sub]");
204 	return 0;
205 
206 append_to_previous_wb:
207 	_debug("append into %lx-%lx", wb->first, wb->last);
208 	wb->usage++;
209 	wb->last++;
210 	wb->to_last = to;
211 	spin_unlock(&vnode->writeback_lock);
212 	SetPagePrivate(page);
213 	set_page_private(page, (unsigned long) wb);
214 	kfree(candidate);
215 	_leave(" = 0 [app]");
216 	return 0;
217 
218 	/* the page is currently bound to another context, so if it's dirty we
219 	 * need to flush it before we can use the new context */
220 flush_conflicting_wb:
221 	_debug("flush conflict");
222 	if (wb->state == AFS_WBACK_PENDING)
223 		wb->state = AFS_WBACK_CONFLICTING;
224 	spin_unlock(&vnode->writeback_lock);
225 	if (PageDirty(page)) {
226 		ret = afs_write_back_from_locked_page(wb, page);
227 		if (ret < 0) {
228 			afs_put_writeback(candidate);
229 			_leave(" = %d", ret);
230 			return ret;
231 		}
232 	}
233 
234 	/* the page holds a ref on the writeback record */
235 	afs_put_writeback(wb);
236 	set_page_private(page, 0);
237 	ClearPagePrivate(page);
238 	goto try_again;
239 }
240 
241 /*
242  * finalise part of a write to a page
243  */
afs_write_end(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned copied,struct page * page,void * fsdata)244 int afs_write_end(struct file *file, struct address_space *mapping,
245 		  loff_t pos, unsigned len, unsigned copied,
246 		  struct page *page, void *fsdata)
247 {
248 	struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
249 	loff_t i_size, maybe_i_size;
250 
251 	_enter("{%x:%u},{%lx}",
252 	       vnode->fid.vid, vnode->fid.vnode, page->index);
253 
254 	maybe_i_size = pos + copied;
255 
256 	i_size = i_size_read(&vnode->vfs_inode);
257 	if (maybe_i_size > i_size) {
258 		spin_lock(&vnode->writeback_lock);
259 		i_size = i_size_read(&vnode->vfs_inode);
260 		if (maybe_i_size > i_size)
261 			i_size_write(&vnode->vfs_inode, maybe_i_size);
262 		spin_unlock(&vnode->writeback_lock);
263 	}
264 
265 	set_page_dirty(page);
266 	if (PageDirty(page))
267 		_debug("dirtied");
268 	unlock_page(page);
269 	page_cache_release(page);
270 
271 	return copied;
272 }
273 
274 /*
275  * kill all the pages in the given range
276  */
afs_kill_pages(struct afs_vnode * vnode,bool error,pgoff_t first,pgoff_t last)277 static void afs_kill_pages(struct afs_vnode *vnode, bool error,
278 			   pgoff_t first, pgoff_t last)
279 {
280 	struct pagevec pv;
281 	unsigned count, loop;
282 
283 	_enter("{%x:%u},%lx-%lx",
284 	       vnode->fid.vid, vnode->fid.vnode, first, last);
285 
286 	pagevec_init(&pv, 0);
287 
288 	do {
289 		_debug("kill %lx-%lx", first, last);
290 
291 		count = last - first + 1;
292 		if (count > PAGEVEC_SIZE)
293 			count = PAGEVEC_SIZE;
294 		pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
295 					      first, count, pv.pages);
296 		ASSERTCMP(pv.nr, ==, count);
297 
298 		for (loop = 0; loop < count; loop++) {
299 			ClearPageUptodate(pv.pages[loop]);
300 			if (error)
301 				SetPageError(pv.pages[loop]);
302 			end_page_writeback(pv.pages[loop]);
303 		}
304 
305 		__pagevec_release(&pv);
306 	} while (first < last);
307 
308 	_leave("");
309 }
310 
311 /*
312  * synchronously write back the locked page and any subsequent non-locked dirty
313  * pages also covered by the same writeback record
314  */
afs_write_back_from_locked_page(struct afs_writeback * wb,struct page * primary_page)315 static int afs_write_back_from_locked_page(struct afs_writeback *wb,
316 					   struct page *primary_page)
317 {
318 	struct page *pages[8], *page;
319 	unsigned long count;
320 	unsigned n, offset, to;
321 	pgoff_t start, first, last;
322 	int loop, ret;
323 
324 	_enter(",%lx", primary_page->index);
325 
326 	count = 1;
327 	if (!clear_page_dirty_for_io(primary_page))
328 		BUG();
329 	if (test_set_page_writeback(primary_page))
330 		BUG();
331 
332 	/* find all consecutive lockable dirty pages, stopping when we find a
333 	 * page that is not immediately lockable, is not dirty or is missing,
334 	 * or we reach the end of the range */
335 	start = primary_page->index;
336 	if (start >= wb->last)
337 		goto no_more;
338 	start++;
339 	do {
340 		_debug("more %lx [%lx]", start, count);
341 		n = wb->last - start + 1;
342 		if (n > ARRAY_SIZE(pages))
343 			n = ARRAY_SIZE(pages);
344 		n = find_get_pages_contig(wb->vnode->vfs_inode.i_mapping,
345 					  start, n, pages);
346 		_debug("fgpc %u", n);
347 		if (n == 0)
348 			goto no_more;
349 		if (pages[0]->index != start) {
350 			do {
351 				put_page(pages[--n]);
352 			} while (n > 0);
353 			goto no_more;
354 		}
355 
356 		for (loop = 0; loop < n; loop++) {
357 			page = pages[loop];
358 			if (page->index > wb->last)
359 				break;
360 			if (!trylock_page(page))
361 				break;
362 			if (!PageDirty(page) ||
363 			    page_private(page) != (unsigned long) wb) {
364 				unlock_page(page);
365 				break;
366 			}
367 			if (!clear_page_dirty_for_io(page))
368 				BUG();
369 			if (test_set_page_writeback(page))
370 				BUG();
371 			unlock_page(page);
372 			put_page(page);
373 		}
374 		count += loop;
375 		if (loop < n) {
376 			for (; loop < n; loop++)
377 				put_page(pages[loop]);
378 			goto no_more;
379 		}
380 
381 		start += loop;
382 	} while (start <= wb->last && count < 65536);
383 
384 no_more:
385 	/* we now have a contiguous set of dirty pages, each with writeback set
386 	 * and the dirty mark cleared; the first page is locked and must remain
387 	 * so, all the rest are unlocked */
388 	first = primary_page->index;
389 	last = first + count - 1;
390 
391 	offset = (first == wb->first) ? wb->offset_first : 0;
392 	to = (last == wb->last) ? wb->to_last : PAGE_SIZE;
393 
394 	_debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
395 
396 	ret = afs_vnode_store_data(wb, first, last, offset, to);
397 	if (ret < 0) {
398 		switch (ret) {
399 		case -EDQUOT:
400 		case -ENOSPC:
401 			set_bit(AS_ENOSPC,
402 				&wb->vnode->vfs_inode.i_mapping->flags);
403 			break;
404 		case -EROFS:
405 		case -EIO:
406 		case -EREMOTEIO:
407 		case -EFBIG:
408 		case -ENOENT:
409 		case -ENOMEDIUM:
410 		case -ENXIO:
411 			afs_kill_pages(wb->vnode, true, first, last);
412 			set_bit(AS_EIO, &wb->vnode->vfs_inode.i_mapping->flags);
413 			break;
414 		case -EACCES:
415 		case -EPERM:
416 		case -ENOKEY:
417 		case -EKEYEXPIRED:
418 		case -EKEYREJECTED:
419 		case -EKEYREVOKED:
420 			afs_kill_pages(wb->vnode, false, first, last);
421 			break;
422 		default:
423 			break;
424 		}
425 	} else {
426 		ret = count;
427 	}
428 
429 	_leave(" = %d", ret);
430 	return ret;
431 }
432 
433 /*
434  * write a page back to the server
435  * - the caller locked the page for us
436  */
afs_writepage(struct page * page,struct writeback_control * wbc)437 int afs_writepage(struct page *page, struct writeback_control *wbc)
438 {
439 	struct afs_writeback *wb;
440 	int ret;
441 
442 	_enter("{%lx},", page->index);
443 
444 	wb = (struct afs_writeback *) page_private(page);
445 	ASSERT(wb != NULL);
446 
447 	ret = afs_write_back_from_locked_page(wb, page);
448 	unlock_page(page);
449 	if (ret < 0) {
450 		_leave(" = %d", ret);
451 		return 0;
452 	}
453 
454 	wbc->nr_to_write -= ret;
455 
456 	_leave(" = 0");
457 	return 0;
458 }
459 
460 /*
461  * write a region of pages back to the server
462  */
afs_writepages_region(struct address_space * mapping,struct writeback_control * wbc,pgoff_t index,pgoff_t end,pgoff_t * _next)463 static int afs_writepages_region(struct address_space *mapping,
464 				 struct writeback_control *wbc,
465 				 pgoff_t index, pgoff_t end, pgoff_t *_next)
466 {
467 	struct afs_writeback *wb;
468 	struct page *page;
469 	int ret, n;
470 
471 	_enter(",,%lx,%lx,", index, end);
472 
473 	do {
474 		n = find_get_pages_tag(mapping, &index, PAGECACHE_TAG_DIRTY,
475 				       1, &page);
476 		if (!n)
477 			break;
478 
479 		_debug("wback %lx", page->index);
480 
481 		if (page->index > end) {
482 			*_next = index;
483 			page_cache_release(page);
484 			_leave(" = 0 [%lx]", *_next);
485 			return 0;
486 		}
487 
488 		/* at this point we hold neither mapping->tree_lock nor lock on
489 		 * the page itself: the page may be truncated or invalidated
490 		 * (changing page->mapping to NULL), or even swizzled back from
491 		 * swapper_space to tmpfs file mapping
492 		 */
493 		lock_page(page);
494 
495 		if (page->mapping != mapping) {
496 			unlock_page(page);
497 			page_cache_release(page);
498 			continue;
499 		}
500 
501 		if (wbc->sync_mode != WB_SYNC_NONE)
502 			wait_on_page_writeback(page);
503 
504 		if (PageWriteback(page) || !PageDirty(page)) {
505 			unlock_page(page);
506 			continue;
507 		}
508 
509 		wb = (struct afs_writeback *) page_private(page);
510 		ASSERT(wb != NULL);
511 
512 		spin_lock(&wb->vnode->writeback_lock);
513 		wb->state = AFS_WBACK_WRITING;
514 		spin_unlock(&wb->vnode->writeback_lock);
515 
516 		ret = afs_write_back_from_locked_page(wb, page);
517 		unlock_page(page);
518 		page_cache_release(page);
519 		if (ret < 0) {
520 			_leave(" = %d", ret);
521 			return ret;
522 		}
523 
524 		wbc->nr_to_write -= ret;
525 
526 		cond_resched();
527 	} while (index < end && wbc->nr_to_write > 0);
528 
529 	*_next = index;
530 	_leave(" = 0 [%lx]", *_next);
531 	return 0;
532 }
533 
534 /*
535  * write some of the pending data back to the server
536  */
afs_writepages(struct address_space * mapping,struct writeback_control * wbc)537 int afs_writepages(struct address_space *mapping,
538 		   struct writeback_control *wbc)
539 {
540 	pgoff_t start, end, next;
541 	int ret;
542 
543 	_enter("");
544 
545 	if (wbc->range_cyclic) {
546 		start = mapping->writeback_index;
547 		end = -1;
548 		ret = afs_writepages_region(mapping, wbc, start, end, &next);
549 		if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
550 			ret = afs_writepages_region(mapping, wbc, 0, start,
551 						    &next);
552 		mapping->writeback_index = next;
553 	} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
554 		end = (pgoff_t)(LLONG_MAX >> PAGE_CACHE_SHIFT);
555 		ret = afs_writepages_region(mapping, wbc, 0, end, &next);
556 		if (wbc->nr_to_write > 0)
557 			mapping->writeback_index = next;
558 	} else {
559 		start = wbc->range_start >> PAGE_CACHE_SHIFT;
560 		end = wbc->range_end >> PAGE_CACHE_SHIFT;
561 		ret = afs_writepages_region(mapping, wbc, start, end, &next);
562 	}
563 
564 	_leave(" = %d", ret);
565 	return ret;
566 }
567 
568 /*
569  * completion of write to server
570  */
afs_pages_written_back(struct afs_vnode * vnode,struct afs_call * call)571 void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
572 {
573 	struct afs_writeback *wb = call->wb;
574 	struct pagevec pv;
575 	unsigned count, loop;
576 	pgoff_t first = call->first, last = call->last;
577 	bool free_wb;
578 
579 	_enter("{%x:%u},{%lx-%lx}",
580 	       vnode->fid.vid, vnode->fid.vnode, first, last);
581 
582 	ASSERT(wb != NULL);
583 
584 	pagevec_init(&pv, 0);
585 
586 	do {
587 		_debug("done %lx-%lx", first, last);
588 
589 		count = last - first + 1;
590 		if (count > PAGEVEC_SIZE)
591 			count = PAGEVEC_SIZE;
592 		pv.nr = find_get_pages_contig(call->mapping, first, count,
593 					      pv.pages);
594 		ASSERTCMP(pv.nr, ==, count);
595 
596 		spin_lock(&vnode->writeback_lock);
597 		for (loop = 0; loop < count; loop++) {
598 			struct page *page = pv.pages[loop];
599 			end_page_writeback(page);
600 			if (page_private(page) == (unsigned long) wb) {
601 				set_page_private(page, 0);
602 				ClearPagePrivate(page);
603 				wb->usage--;
604 			}
605 		}
606 		free_wb = false;
607 		if (wb->usage == 0) {
608 			afs_unlink_writeback(wb);
609 			free_wb = true;
610 		}
611 		spin_unlock(&vnode->writeback_lock);
612 		first += count;
613 		if (free_wb) {
614 			afs_free_writeback(wb);
615 			wb = NULL;
616 		}
617 
618 		__pagevec_release(&pv);
619 	} while (first <= last);
620 
621 	_leave("");
622 }
623 
624 /*
625  * write to an AFS file
626  */
afs_file_write(struct kiocb * iocb,const struct iovec * iov,unsigned long nr_segs,loff_t pos)627 ssize_t afs_file_write(struct kiocb *iocb, const struct iovec *iov,
628 		       unsigned long nr_segs, loff_t pos)
629 {
630 	struct dentry *dentry = iocb->ki_filp->f_path.dentry;
631 	struct afs_vnode *vnode = AFS_FS_I(dentry->d_inode);
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  */
afs_writeback_all(struct afs_vnode * vnode)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  */
afs_fsync(struct file * file,loff_t start,loff_t end,int datasync)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  */
afs_page_mkwrite(struct vm_area_struct * vma,struct page * page)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