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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 "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,unsigned int len,struct page * page)86 static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
87 			 loff_t pos, unsigned int len, struct page *page)
88 {
89 	struct afs_read *req;
90 	int ret;
91 
92 	_enter(",,%llu", (unsigned long long)pos);
93 
94 	req = kzalloc(sizeof(struct afs_read) + sizeof(struct page *),
95 		      GFP_KERNEL);
96 	if (!req)
97 		return -ENOMEM;
98 
99 	atomic_set(&req->usage, 1);
100 	req->pos = pos;
101 	req->len = len;
102 	req->nr_pages = 1;
103 	req->pages[0] = page;
104 	get_page(page);
105 
106 	ret = afs_vnode_fetch_data(vnode, key, req);
107 	afs_put_read(req);
108 	if (ret < 0) {
109 		if (ret == -ENOENT) {
110 			_debug("got NOENT from server"
111 			       " - marking file deleted and stale");
112 			set_bit(AFS_VNODE_DELETED, &vnode->flags);
113 			ret = -ESTALE;
114 		}
115 	}
116 
117 	_leave(" = %d", ret);
118 	return ret;
119 }
120 
121 /*
122  * prepare to perform part of a write to a page
123  */
afs_write_begin(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned flags,struct page ** pagep,void ** fsdata)124 int afs_write_begin(struct file *file, struct address_space *mapping,
125 		    loff_t pos, unsigned len, unsigned flags,
126 		    struct page **pagep, void **fsdata)
127 {
128 	struct afs_writeback *candidate, *wb;
129 	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
130 	struct page *page;
131 	struct key *key = file->private_data;
132 	unsigned from = pos & (PAGE_SIZE - 1);
133 	unsigned to = from + len;
134 	pgoff_t index = pos >> PAGE_SHIFT;
135 	int ret;
136 
137 	_enter("{%x:%u},{%lx},%u,%u",
138 	       vnode->fid.vid, vnode->fid.vnode, index, from, to);
139 
140 	candidate = kzalloc(sizeof(*candidate), GFP_KERNEL);
141 	if (!candidate)
142 		return -ENOMEM;
143 	candidate->vnode = vnode;
144 	candidate->first = candidate->last = index;
145 	candidate->offset_first = from;
146 	candidate->to_last = to;
147 	INIT_LIST_HEAD(&candidate->link);
148 	candidate->usage = 1;
149 	candidate->state = AFS_WBACK_PENDING;
150 	init_waitqueue_head(&candidate->waitq);
151 
152 	page = grab_cache_page_write_begin(mapping, index, flags);
153 	if (!page) {
154 		kfree(candidate);
155 		return -ENOMEM;
156 	}
157 
158 	if (!PageUptodate(page) && len != PAGE_SIZE) {
159 		ret = afs_fill_page(vnode, key, pos & PAGE_MASK, PAGE_SIZE, page);
160 		if (ret < 0) {
161 			unlock_page(page);
162 			put_page(page);
163 			kfree(candidate);
164 			_leave(" = %d [prep]", ret);
165 			return ret;
166 		}
167 		SetPageUptodate(page);
168 	}
169 
170 	/* page won't leak in error case: it eventually gets cleaned off LRU */
171 	*pagep = page;
172 
173 try_again:
174 	spin_lock(&vnode->writeback_lock);
175 
176 	/* see if this page is already pending a writeback under a suitable key
177 	 * - if so we can just join onto that one */
178 	wb = (struct afs_writeback *) page_private(page);
179 	if (wb) {
180 		if (wb->key == key && wb->state == AFS_WBACK_PENDING)
181 			goto subsume_in_current_wb;
182 		goto flush_conflicting_wb;
183 	}
184 
185 	if (index > 0) {
186 		/* see if we can find an already pending writeback that we can
187 		 * append this page to */
188 		list_for_each_entry(wb, &vnode->writebacks, link) {
189 			if (wb->last == index - 1 && wb->key == key &&
190 			    wb->state == AFS_WBACK_PENDING)
191 				goto append_to_previous_wb;
192 		}
193 	}
194 
195 	list_add_tail(&candidate->link, &vnode->writebacks);
196 	candidate->key = key_get(key);
197 	spin_unlock(&vnode->writeback_lock);
198 	SetPagePrivate(page);
199 	set_page_private(page, (unsigned long) candidate);
200 	_leave(" = 0 [new]");
201 	return 0;
202 
203 subsume_in_current_wb:
204 	_debug("subsume");
205 	ASSERTRANGE(wb->first, <=, index, <=, wb->last);
206 	if (index == wb->first && from < wb->offset_first)
207 		wb->offset_first = from;
208 	if (index == wb->last && to > wb->to_last)
209 		wb->to_last = to;
210 	spin_unlock(&vnode->writeback_lock);
211 	kfree(candidate);
212 	_leave(" = 0 [sub]");
213 	return 0;
214 
215 append_to_previous_wb:
216 	_debug("append into %lx-%lx", wb->first, wb->last);
217 	wb->usage++;
218 	wb->last++;
219 	wb->to_last = to;
220 	spin_unlock(&vnode->writeback_lock);
221 	SetPagePrivate(page);
222 	set_page_private(page, (unsigned long) wb);
223 	kfree(candidate);
224 	_leave(" = 0 [app]");
225 	return 0;
226 
227 	/* the page is currently bound to another context, so if it's dirty we
228 	 * need to flush it before we can use the new context */
229 flush_conflicting_wb:
230 	_debug("flush conflict");
231 	if (wb->state == AFS_WBACK_PENDING)
232 		wb->state = AFS_WBACK_CONFLICTING;
233 	spin_unlock(&vnode->writeback_lock);
234 	if (clear_page_dirty_for_io(page)) {
235 		ret = afs_write_back_from_locked_page(wb, page);
236 		if (ret < 0) {
237 			afs_put_writeback(candidate);
238 			_leave(" = %d", ret);
239 			return ret;
240 		}
241 	}
242 
243 	/* the page holds a ref on the writeback record */
244 	afs_put_writeback(wb);
245 	set_page_private(page, 0);
246 	ClearPagePrivate(page);
247 	goto try_again;
248 }
249 
250 /*
251  * finalise part of a write to a page
252  */
afs_write_end(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned copied,struct page * page,void * fsdata)253 int afs_write_end(struct file *file, struct address_space *mapping,
254 		  loff_t pos, unsigned len, unsigned copied,
255 		  struct page *page, void *fsdata)
256 {
257 	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
258 	struct key *key = file->private_data;
259 	loff_t i_size, maybe_i_size;
260 	int ret;
261 
262 	_enter("{%x:%u},{%lx}",
263 	       vnode->fid.vid, vnode->fid.vnode, page->index);
264 
265 	maybe_i_size = pos + copied;
266 
267 	i_size = i_size_read(&vnode->vfs_inode);
268 	if (maybe_i_size > i_size) {
269 		spin_lock(&vnode->writeback_lock);
270 		i_size = i_size_read(&vnode->vfs_inode);
271 		if (maybe_i_size > i_size)
272 			i_size_write(&vnode->vfs_inode, maybe_i_size);
273 		spin_unlock(&vnode->writeback_lock);
274 	}
275 
276 	if (!PageUptodate(page)) {
277 		if (copied < len) {
278 			/* Try and load any missing data from the server.  The
279 			 * unmarshalling routine will take care of clearing any
280 			 * bits that are beyond the EOF.
281 			 */
282 			ret = afs_fill_page(vnode, key, pos + copied,
283 					    len - copied, page);
284 			if (ret < 0)
285 				goto out;
286 		}
287 		SetPageUptodate(page);
288 	}
289 
290 	set_page_dirty(page);
291 	if (PageDirty(page))
292 		_debug("dirtied");
293 	ret = copied;
294 
295 out:
296 	unlock_page(page);
297 	put_page(page);
298 	return ret;
299 }
300 
301 /*
302  * kill all the pages in the given range
303  */
afs_kill_pages(struct afs_vnode * vnode,bool error,pgoff_t first,pgoff_t last)304 static void afs_kill_pages(struct afs_vnode *vnode, bool error,
305 			   pgoff_t first, pgoff_t last)
306 {
307 	struct pagevec pv;
308 	unsigned count, loop;
309 
310 	_enter("{%x:%u},%lx-%lx",
311 	       vnode->fid.vid, vnode->fid.vnode, first, last);
312 
313 	pagevec_init(&pv, 0);
314 
315 	do {
316 		_debug("kill %lx-%lx", first, last);
317 
318 		count = last - first + 1;
319 		if (count > PAGEVEC_SIZE)
320 			count = PAGEVEC_SIZE;
321 		pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
322 					      first, count, pv.pages);
323 		ASSERTCMP(pv.nr, ==, count);
324 
325 		for (loop = 0; loop < count; loop++) {
326 			struct page *page = pv.pages[loop];
327 			ClearPageUptodate(page);
328 			if (error)
329 				SetPageError(page);
330 			if (PageWriteback(page))
331 				end_page_writeback(page);
332 			if (page->index >= first)
333 				first = page->index + 1;
334 		}
335 
336 		__pagevec_release(&pv);
337 	} while (first < last);
338 
339 	_leave("");
340 }
341 
342 /*
343  * synchronously write back the locked page and any subsequent non-locked dirty
344  * pages also covered by the same writeback record
345  */
afs_write_back_from_locked_page(struct afs_writeback * wb,struct page * primary_page)346 static int afs_write_back_from_locked_page(struct afs_writeback *wb,
347 					   struct page *primary_page)
348 {
349 	struct page *pages[8], *page;
350 	unsigned long count;
351 	unsigned n, offset, to;
352 	pgoff_t start, first, last;
353 	int loop, ret;
354 
355 	_enter(",%lx", primary_page->index);
356 
357 	count = 1;
358 	if (test_set_page_writeback(primary_page))
359 		BUG();
360 
361 	/* find all consecutive lockable dirty pages, stopping when we find a
362 	 * page that is not immediately lockable, is not dirty or is missing,
363 	 * or we reach the end of the range */
364 	start = primary_page->index;
365 	if (start >= wb->last)
366 		goto no_more;
367 	start++;
368 	do {
369 		_debug("more %lx [%lx]", start, count);
370 		n = wb->last - start + 1;
371 		if (n > ARRAY_SIZE(pages))
372 			n = ARRAY_SIZE(pages);
373 		n = find_get_pages_contig(wb->vnode->vfs_inode.i_mapping,
374 					  start, n, pages);
375 		_debug("fgpc %u", n);
376 		if (n == 0)
377 			goto no_more;
378 		if (pages[0]->index != start) {
379 			do {
380 				put_page(pages[--n]);
381 			} while (n > 0);
382 			goto no_more;
383 		}
384 
385 		for (loop = 0; loop < n; loop++) {
386 			page = pages[loop];
387 			if (page->index > wb->last)
388 				break;
389 			if (!trylock_page(page))
390 				break;
391 			if (!PageDirty(page) ||
392 			    page_private(page) != (unsigned long) wb) {
393 				unlock_page(page);
394 				break;
395 			}
396 			if (!clear_page_dirty_for_io(page))
397 				BUG();
398 			if (test_set_page_writeback(page))
399 				BUG();
400 			unlock_page(page);
401 			put_page(page);
402 		}
403 		count += loop;
404 		if (loop < n) {
405 			for (; loop < n; loop++)
406 				put_page(pages[loop]);
407 			goto no_more;
408 		}
409 
410 		start += loop;
411 	} while (start <= wb->last && count < 65536);
412 
413 no_more:
414 	/* we now have a contiguous set of dirty pages, each with writeback set
415 	 * and the dirty mark cleared; the first page is locked and must remain
416 	 * so, all the rest are unlocked */
417 	first = primary_page->index;
418 	last = first + count - 1;
419 
420 	offset = (first == wb->first) ? wb->offset_first : 0;
421 	to = (last == wb->last) ? wb->to_last : PAGE_SIZE;
422 
423 	_debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
424 
425 	ret = afs_vnode_store_data(wb, first, last, offset, to);
426 	if (ret < 0) {
427 		switch (ret) {
428 		case -EDQUOT:
429 		case -ENOSPC:
430 			mapping_set_error(wb->vnode->vfs_inode.i_mapping, -ENOSPC);
431 			break;
432 		case -EROFS:
433 		case -EIO:
434 		case -EREMOTEIO:
435 		case -EFBIG:
436 		case -ENOENT:
437 		case -ENOMEDIUM:
438 		case -ENXIO:
439 			afs_kill_pages(wb->vnode, true, first, last);
440 			mapping_set_error(wb->vnode->vfs_inode.i_mapping, -EIO);
441 			break;
442 		case -EACCES:
443 		case -EPERM:
444 		case -ENOKEY:
445 		case -EKEYEXPIRED:
446 		case -EKEYREJECTED:
447 		case -EKEYREVOKED:
448 			afs_kill_pages(wb->vnode, false, first, last);
449 			break;
450 		default:
451 			break;
452 		}
453 	} else {
454 		ret = count;
455 	}
456 
457 	_leave(" = %d", ret);
458 	return ret;
459 }
460 
461 /*
462  * write a page back to the server
463  * - the caller locked the page for us
464  */
afs_writepage(struct page * page,struct writeback_control * wbc)465 int afs_writepage(struct page *page, struct writeback_control *wbc)
466 {
467 	struct afs_writeback *wb;
468 	int ret;
469 
470 	_enter("{%lx},", page->index);
471 
472 	wb = (struct afs_writeback *) page_private(page);
473 	ASSERT(wb != NULL);
474 
475 	ret = afs_write_back_from_locked_page(wb, page);
476 	unlock_page(page);
477 	if (ret < 0) {
478 		_leave(" = %d", ret);
479 		return 0;
480 	}
481 
482 	wbc->nr_to_write -= ret;
483 
484 	_leave(" = 0");
485 	return 0;
486 }
487 
488 /*
489  * write a region of pages back to the server
490  */
afs_writepages_region(struct address_space * mapping,struct writeback_control * wbc,pgoff_t index,pgoff_t end,pgoff_t * _next)491 static int afs_writepages_region(struct address_space *mapping,
492 				 struct writeback_control *wbc,
493 				 pgoff_t index, pgoff_t end, pgoff_t *_next)
494 {
495 	struct afs_writeback *wb;
496 	struct page *page;
497 	int ret, n;
498 
499 	_enter(",,%lx,%lx,", index, end);
500 
501 	do {
502 		n = find_get_pages_tag(mapping, &index, PAGECACHE_TAG_DIRTY,
503 				       1, &page);
504 		if (!n)
505 			break;
506 
507 		_debug("wback %lx", page->index);
508 
509 		if (page->index > end) {
510 			*_next = index;
511 			put_page(page);
512 			_leave(" = 0 [%lx]", *_next);
513 			return 0;
514 		}
515 
516 		/* at this point we hold neither mapping->tree_lock nor lock on
517 		 * the page itself: the page may be truncated or invalidated
518 		 * (changing page->mapping to NULL), or even swizzled back from
519 		 * swapper_space to tmpfs file mapping
520 		 */
521 		lock_page(page);
522 
523 		if (page->mapping != mapping || !PageDirty(page)) {
524 			unlock_page(page);
525 			put_page(page);
526 			continue;
527 		}
528 
529 		if (PageWriteback(page)) {
530 			unlock_page(page);
531 			if (wbc->sync_mode != WB_SYNC_NONE)
532 				wait_on_page_writeback(page);
533 			put_page(page);
534 			continue;
535 		}
536 
537 		wb = (struct afs_writeback *) page_private(page);
538 		ASSERT(wb != NULL);
539 
540 		spin_lock(&wb->vnode->writeback_lock);
541 		wb->state = AFS_WBACK_WRITING;
542 		spin_unlock(&wb->vnode->writeback_lock);
543 
544 		if (!clear_page_dirty_for_io(page))
545 			BUG();
546 		ret = afs_write_back_from_locked_page(wb, page);
547 		unlock_page(page);
548 		put_page(page);
549 		if (ret < 0) {
550 			_leave(" = %d", ret);
551 			return ret;
552 		}
553 
554 		wbc->nr_to_write -= ret;
555 
556 		cond_resched();
557 	} while (index < end && wbc->nr_to_write > 0);
558 
559 	*_next = index;
560 	_leave(" = 0 [%lx]", *_next);
561 	return 0;
562 }
563 
564 /*
565  * write some of the pending data back to the server
566  */
afs_writepages(struct address_space * mapping,struct writeback_control * wbc)567 int afs_writepages(struct address_space *mapping,
568 		   struct writeback_control *wbc)
569 {
570 	pgoff_t start, end, next;
571 	int ret;
572 
573 	_enter("");
574 
575 	if (wbc->range_cyclic) {
576 		start = mapping->writeback_index;
577 		end = -1;
578 		ret = afs_writepages_region(mapping, wbc, start, end, &next);
579 		if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
580 			ret = afs_writepages_region(mapping, wbc, 0, start,
581 						    &next);
582 		mapping->writeback_index = next;
583 	} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
584 		end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT);
585 		ret = afs_writepages_region(mapping, wbc, 0, end, &next);
586 		if (wbc->nr_to_write > 0)
587 			mapping->writeback_index = next;
588 	} else {
589 		start = wbc->range_start >> PAGE_SHIFT;
590 		end = wbc->range_end >> PAGE_SHIFT;
591 		ret = afs_writepages_region(mapping, wbc, start, end, &next);
592 	}
593 
594 	_leave(" = %d", ret);
595 	return ret;
596 }
597 
598 /*
599  * completion of write to server
600  */
afs_pages_written_back(struct afs_vnode * vnode,struct afs_call * call)601 void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
602 {
603 	struct afs_writeback *wb = call->wb;
604 	struct pagevec pv;
605 	unsigned count, loop;
606 	pgoff_t first = call->first, last = call->last;
607 	bool free_wb;
608 
609 	_enter("{%x:%u},{%lx-%lx}",
610 	       vnode->fid.vid, vnode->fid.vnode, first, last);
611 
612 	ASSERT(wb != NULL);
613 
614 	pagevec_init(&pv, 0);
615 
616 	do {
617 		_debug("done %lx-%lx", first, last);
618 
619 		count = last - first + 1;
620 		if (count > PAGEVEC_SIZE)
621 			count = PAGEVEC_SIZE;
622 		pv.nr = find_get_pages_contig(call->mapping, first, count,
623 					      pv.pages);
624 		ASSERTCMP(pv.nr, ==, count);
625 
626 		spin_lock(&vnode->writeback_lock);
627 		for (loop = 0; loop < count; loop++) {
628 			struct page *page = pv.pages[loop];
629 			end_page_writeback(page);
630 			if (page_private(page) == (unsigned long) wb) {
631 				set_page_private(page, 0);
632 				ClearPagePrivate(page);
633 				wb->usage--;
634 			}
635 		}
636 		free_wb = false;
637 		if (wb->usage == 0) {
638 			afs_unlink_writeback(wb);
639 			free_wb = true;
640 		}
641 		spin_unlock(&vnode->writeback_lock);
642 		first += count;
643 		if (free_wb) {
644 			afs_free_writeback(wb);
645 			wb = NULL;
646 		}
647 
648 		__pagevec_release(&pv);
649 	} while (first <= last);
650 
651 	_leave("");
652 }
653 
654 /*
655  * write to an AFS file
656  */
afs_file_write(struct kiocb * iocb,struct iov_iter * from)657 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
658 {
659 	struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
660 	ssize_t result;
661 	size_t count = iov_iter_count(from);
662 
663 	_enter("{%x.%u},{%zu},",
664 	       vnode->fid.vid, vnode->fid.vnode, count);
665 
666 	if (IS_SWAPFILE(&vnode->vfs_inode)) {
667 		printk(KERN_INFO
668 		       "AFS: Attempt to write to active swap file!\n");
669 		return -EBUSY;
670 	}
671 
672 	if (!count)
673 		return 0;
674 
675 	result = generic_file_write_iter(iocb, from);
676 
677 	_leave(" = %zd", result);
678 	return result;
679 }
680 
681 /*
682  * flush the vnode to the fileserver
683  */
afs_writeback_all(struct afs_vnode * vnode)684 int afs_writeback_all(struct afs_vnode *vnode)
685 {
686 	struct address_space *mapping = vnode->vfs_inode.i_mapping;
687 	struct writeback_control wbc = {
688 		.sync_mode	= WB_SYNC_ALL,
689 		.nr_to_write	= LONG_MAX,
690 		.range_cyclic	= 1,
691 	};
692 	int ret;
693 
694 	_enter("");
695 
696 	ret = mapping->a_ops->writepages(mapping, &wbc);
697 	__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
698 
699 	_leave(" = %d", ret);
700 	return ret;
701 }
702 
703 /*
704  * flush any dirty pages for this process, and check for write errors.
705  * - the return status from this call provides a reliable indication of
706  *   whether any write errors occurred for this process.
707  */
afs_fsync(struct file * file,loff_t start,loff_t end,int datasync)708 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
709 {
710 	struct inode *inode = file_inode(file);
711 	struct afs_writeback *wb, *xwb;
712 	struct afs_vnode *vnode = AFS_FS_I(inode);
713 	int ret;
714 
715 	_enter("{%x:%u},{n=%pD},%d",
716 	       vnode->fid.vid, vnode->fid.vnode, file,
717 	       datasync);
718 
719 	ret = file_write_and_wait_range(file, start, end);
720 	if (ret)
721 		return ret;
722 	inode_lock(inode);
723 
724 	/* use a writeback record as a marker in the queue - when this reaches
725 	 * the front of the queue, all the outstanding writes are either
726 	 * completed or rejected */
727 	wb = kzalloc(sizeof(*wb), GFP_KERNEL);
728 	if (!wb) {
729 		ret = -ENOMEM;
730 		goto out;
731 	}
732 	wb->vnode = vnode;
733 	wb->first = 0;
734 	wb->last = -1;
735 	wb->offset_first = 0;
736 	wb->to_last = PAGE_SIZE;
737 	wb->usage = 1;
738 	wb->state = AFS_WBACK_SYNCING;
739 	init_waitqueue_head(&wb->waitq);
740 
741 	spin_lock(&vnode->writeback_lock);
742 	list_for_each_entry(xwb, &vnode->writebacks, link) {
743 		if (xwb->state == AFS_WBACK_PENDING)
744 			xwb->state = AFS_WBACK_CONFLICTING;
745 	}
746 	list_add_tail(&wb->link, &vnode->writebacks);
747 	spin_unlock(&vnode->writeback_lock);
748 
749 	/* push all the outstanding writebacks to the server */
750 	ret = afs_writeback_all(vnode);
751 	if (ret < 0) {
752 		afs_put_writeback(wb);
753 		_leave(" = %d [wb]", ret);
754 		goto out;
755 	}
756 
757 	/* wait for the preceding writes to actually complete */
758 	ret = wait_event_interruptible(wb->waitq,
759 				       wb->state == AFS_WBACK_COMPLETE ||
760 				       vnode->writebacks.next == &wb->link);
761 	afs_put_writeback(wb);
762 	_leave(" = %d", ret);
763 out:
764 	inode_unlock(inode);
765 	return ret;
766 }
767 
768 /*
769  * Flush out all outstanding writes on a file opened for writing when it is
770  * closed.
771  */
afs_flush(struct file * file,fl_owner_t id)772 int afs_flush(struct file *file, fl_owner_t id)
773 {
774 	_enter("");
775 
776 	if ((file->f_mode & FMODE_WRITE) == 0)
777 		return 0;
778 
779 	return vfs_fsync(file, 0);
780 }
781 
782 /*
783  * notification that a previously read-only page is about to become writable
784  * - if it returns an error, the caller will deliver a bus error signal
785  */
afs_page_mkwrite(struct vm_area_struct * vma,struct page * page)786 int afs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
787 {
788 	struct afs_vnode *vnode = AFS_FS_I(vma->vm_file->f_mapping->host);
789 
790 	_enter("{{%x:%u}},{%lx}",
791 	       vnode->fid.vid, vnode->fid.vnode, page->index);
792 
793 	/* wait for the page to be written to the cache before we allow it to
794 	 * be modified */
795 #ifdef CONFIG_AFS_FSCACHE
796 	fscache_wait_on_page_write(vnode->cache, page);
797 #endif
798 
799 	_leave(" = 0");
800 	return 0;
801 }
802