xref: /openbmc/linux/fs/afs/write.c (revision 2359ccdd)
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/backing-dev.h>
13 #include <linux/slab.h>
14 #include <linux/fs.h>
15 #include <linux/pagemap.h>
16 #include <linux/writeback.h>
17 #include <linux/pagevec.h>
18 #include "internal.h"
19 
20 /*
21  * mark a page as having been made dirty and thus needing writeback
22  */
23 int afs_set_page_dirty(struct page *page)
24 {
25 	_enter("");
26 	return __set_page_dirty_nobuffers(page);
27 }
28 
29 /*
30  * partly or wholly fill a page that's under preparation for writing
31  */
32 static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
33 			 loff_t pos, unsigned int len, struct page *page)
34 {
35 	struct afs_read *req;
36 	int ret;
37 
38 	_enter(",,%llu", (unsigned long long)pos);
39 
40 	req = kzalloc(sizeof(struct afs_read) + sizeof(struct page *),
41 		      GFP_KERNEL);
42 	if (!req)
43 		return -ENOMEM;
44 
45 	refcount_set(&req->usage, 1);
46 	req->pos = pos;
47 	req->len = len;
48 	req->nr_pages = 1;
49 	req->pages = req->array;
50 	req->pages[0] = page;
51 	get_page(page);
52 
53 	ret = afs_fetch_data(vnode, key, req);
54 	afs_put_read(req);
55 	if (ret < 0) {
56 		if (ret == -ENOENT) {
57 			_debug("got NOENT from server"
58 			       " - marking file deleted and stale");
59 			set_bit(AFS_VNODE_DELETED, &vnode->flags);
60 			ret = -ESTALE;
61 		}
62 	}
63 
64 	_leave(" = %d", ret);
65 	return ret;
66 }
67 
68 /*
69  * prepare to perform part of a write to a page
70  */
71 int afs_write_begin(struct file *file, struct address_space *mapping,
72 		    loff_t pos, unsigned len, unsigned flags,
73 		    struct page **pagep, void **fsdata)
74 {
75 	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
76 	struct page *page;
77 	struct key *key = afs_file_key(file);
78 	unsigned long priv;
79 	unsigned f, from = pos & (PAGE_SIZE - 1);
80 	unsigned t, to = from + len;
81 	pgoff_t index = pos >> PAGE_SHIFT;
82 	int ret;
83 
84 	_enter("{%x:%u},{%lx},%u,%u",
85 	       vnode->fid.vid, vnode->fid.vnode, index, from, to);
86 
87 	/* We want to store information about how much of a page is altered in
88 	 * page->private.
89 	 */
90 	BUILD_BUG_ON(PAGE_SIZE > 32768 && sizeof(page->private) < 8);
91 
92 	page = grab_cache_page_write_begin(mapping, index, flags);
93 	if (!page)
94 		return -ENOMEM;
95 
96 	if (!PageUptodate(page) && len != PAGE_SIZE) {
97 		ret = afs_fill_page(vnode, key, pos & PAGE_MASK, PAGE_SIZE, page);
98 		if (ret < 0) {
99 			unlock_page(page);
100 			put_page(page);
101 			_leave(" = %d [prep]", ret);
102 			return ret;
103 		}
104 		SetPageUptodate(page);
105 	}
106 
107 	/* page won't leak in error case: it eventually gets cleaned off LRU */
108 	*pagep = page;
109 
110 try_again:
111 	/* See if this page is already partially written in a way that we can
112 	 * merge the new write with.
113 	 */
114 	t = f = 0;
115 	if (PagePrivate(page)) {
116 		priv = page_private(page);
117 		f = priv & AFS_PRIV_MAX;
118 		t = priv >> AFS_PRIV_SHIFT;
119 		ASSERTCMP(f, <=, t);
120 	}
121 
122 	if (f != t) {
123 		if (PageWriteback(page)) {
124 			trace_afs_page_dirty(vnode, tracepoint_string("alrdy"),
125 					     page->index, priv);
126 			goto flush_conflicting_write;
127 		}
128 		/* If the file is being filled locally, allow inter-write
129 		 * spaces to be merged into writes.  If it's not, only write
130 		 * back what the user gives us.
131 		 */
132 		if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
133 		    (to < f || from > t))
134 			goto flush_conflicting_write;
135 		if (from < f)
136 			f = from;
137 		if (to > t)
138 			t = to;
139 	} else {
140 		f = from;
141 		t = to;
142 	}
143 
144 	priv = (unsigned long)t << AFS_PRIV_SHIFT;
145 	priv |= f;
146 	trace_afs_page_dirty(vnode, tracepoint_string("begin"),
147 			     page->index, priv);
148 	SetPagePrivate(page);
149 	set_page_private(page, priv);
150 	_leave(" = 0");
151 	return 0;
152 
153 	/* The previous write and this write aren't adjacent or overlapping, so
154 	 * flush the page out.
155 	 */
156 flush_conflicting_write:
157 	_debug("flush conflict");
158 	ret = write_one_page(page);
159 	if (ret < 0) {
160 		_leave(" = %d", ret);
161 		return ret;
162 	}
163 
164 	ret = lock_page_killable(page);
165 	if (ret < 0) {
166 		_leave(" = %d", ret);
167 		return ret;
168 	}
169 	goto try_again;
170 }
171 
172 /*
173  * finalise part of a write to a page
174  */
175 int afs_write_end(struct file *file, struct address_space *mapping,
176 		  loff_t pos, unsigned len, unsigned copied,
177 		  struct page *page, void *fsdata)
178 {
179 	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
180 	struct key *key = afs_file_key(file);
181 	loff_t i_size, maybe_i_size;
182 	int ret;
183 
184 	_enter("{%x:%u},{%lx}",
185 	       vnode->fid.vid, vnode->fid.vnode, page->index);
186 
187 	maybe_i_size = pos + copied;
188 
189 	i_size = i_size_read(&vnode->vfs_inode);
190 	if (maybe_i_size > i_size) {
191 		spin_lock(&vnode->wb_lock);
192 		i_size = i_size_read(&vnode->vfs_inode);
193 		if (maybe_i_size > i_size)
194 			i_size_write(&vnode->vfs_inode, maybe_i_size);
195 		spin_unlock(&vnode->wb_lock);
196 	}
197 
198 	if (!PageUptodate(page)) {
199 		if (copied < len) {
200 			/* Try and load any missing data from the server.  The
201 			 * unmarshalling routine will take care of clearing any
202 			 * bits that are beyond the EOF.
203 			 */
204 			ret = afs_fill_page(vnode, key, pos + copied,
205 					    len - copied, page);
206 			if (ret < 0)
207 				goto out;
208 		}
209 		SetPageUptodate(page);
210 	}
211 
212 	set_page_dirty(page);
213 	if (PageDirty(page))
214 		_debug("dirtied");
215 	ret = copied;
216 
217 out:
218 	unlock_page(page);
219 	put_page(page);
220 	return ret;
221 }
222 
223 /*
224  * kill all the pages in the given range
225  */
226 static void afs_kill_pages(struct address_space *mapping,
227 			   pgoff_t first, pgoff_t last)
228 {
229 	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
230 	struct pagevec pv;
231 	unsigned count, loop;
232 
233 	_enter("{%x:%u},%lx-%lx",
234 	       vnode->fid.vid, vnode->fid.vnode, first, last);
235 
236 	pagevec_init(&pv);
237 
238 	do {
239 		_debug("kill %lx-%lx", first, last);
240 
241 		count = last - first + 1;
242 		if (count > PAGEVEC_SIZE)
243 			count = PAGEVEC_SIZE;
244 		pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
245 		ASSERTCMP(pv.nr, ==, count);
246 
247 		for (loop = 0; loop < count; loop++) {
248 			struct page *page = pv.pages[loop];
249 			ClearPageUptodate(page);
250 			SetPageError(page);
251 			end_page_writeback(page);
252 			if (page->index >= first)
253 				first = page->index + 1;
254 			lock_page(page);
255 			generic_error_remove_page(mapping, page);
256 		}
257 
258 		__pagevec_release(&pv);
259 	} while (first <= last);
260 
261 	_leave("");
262 }
263 
264 /*
265  * Redirty all the pages in a given range.
266  */
267 static void afs_redirty_pages(struct writeback_control *wbc,
268 			      struct address_space *mapping,
269 			      pgoff_t first, pgoff_t last)
270 {
271 	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
272 	struct pagevec pv;
273 	unsigned count, loop;
274 
275 	_enter("{%x:%u},%lx-%lx",
276 	       vnode->fid.vid, vnode->fid.vnode, first, last);
277 
278 	pagevec_init(&pv);
279 
280 	do {
281 		_debug("redirty %lx-%lx", first, last);
282 
283 		count = last - first + 1;
284 		if (count > PAGEVEC_SIZE)
285 			count = PAGEVEC_SIZE;
286 		pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
287 		ASSERTCMP(pv.nr, ==, count);
288 
289 		for (loop = 0; loop < count; loop++) {
290 			struct page *page = pv.pages[loop];
291 
292 			redirty_page_for_writepage(wbc, page);
293 			end_page_writeback(page);
294 			if (page->index >= first)
295 				first = page->index + 1;
296 		}
297 
298 		__pagevec_release(&pv);
299 	} while (first <= last);
300 
301 	_leave("");
302 }
303 
304 /*
305  * write to a file
306  */
307 static int afs_store_data(struct address_space *mapping,
308 			  pgoff_t first, pgoff_t last,
309 			  unsigned offset, unsigned to)
310 {
311 	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
312 	struct afs_fs_cursor fc;
313 	struct afs_wb_key *wbk = NULL;
314 	struct list_head *p;
315 	int ret = -ENOKEY, ret2;
316 
317 	_enter("%s{%x:%u.%u},%lx,%lx,%x,%x",
318 	       vnode->volume->name,
319 	       vnode->fid.vid,
320 	       vnode->fid.vnode,
321 	       vnode->fid.unique,
322 	       first, last, offset, to);
323 
324 	spin_lock(&vnode->wb_lock);
325 	p = vnode->wb_keys.next;
326 
327 	/* Iterate through the list looking for a valid key to use. */
328 try_next_key:
329 	while (p != &vnode->wb_keys) {
330 		wbk = list_entry(p, struct afs_wb_key, vnode_link);
331 		_debug("wbk %u", key_serial(wbk->key));
332 		ret2 = key_validate(wbk->key);
333 		if (ret2 == 0)
334 			goto found_key;
335 		if (ret == -ENOKEY)
336 			ret = ret2;
337 		p = p->next;
338 	}
339 
340 	spin_unlock(&vnode->wb_lock);
341 	afs_put_wb_key(wbk);
342 	_leave(" = %d [no keys]", ret);
343 	return ret;
344 
345 found_key:
346 	refcount_inc(&wbk->usage);
347 	spin_unlock(&vnode->wb_lock);
348 
349 	_debug("USE WB KEY %u", key_serial(wbk->key));
350 
351 	ret = -ERESTARTSYS;
352 	if (afs_begin_vnode_operation(&fc, vnode, wbk->key)) {
353 		while (afs_select_fileserver(&fc)) {
354 			fc.cb_break = vnode->cb_break + vnode->cb_s_break;
355 			afs_fs_store_data(&fc, mapping, first, last, offset, to);
356 		}
357 
358 		afs_check_for_remote_deletion(&fc, fc.vnode);
359 		afs_vnode_commit_status(&fc, vnode, fc.cb_break);
360 		ret = afs_end_vnode_operation(&fc);
361 	}
362 
363 	switch (ret) {
364 	case 0:
365 		afs_stat_v(vnode, n_stores);
366 		atomic_long_add((last * PAGE_SIZE + to) -
367 				(first * PAGE_SIZE + offset),
368 				&afs_v2net(vnode)->n_store_bytes);
369 		break;
370 	case -EACCES:
371 	case -EPERM:
372 	case -ENOKEY:
373 	case -EKEYEXPIRED:
374 	case -EKEYREJECTED:
375 	case -EKEYREVOKED:
376 		_debug("next");
377 		spin_lock(&vnode->wb_lock);
378 		p = wbk->vnode_link.next;
379 		afs_put_wb_key(wbk);
380 		goto try_next_key;
381 	}
382 
383 	afs_put_wb_key(wbk);
384 	_leave(" = %d", ret);
385 	return ret;
386 }
387 
388 /*
389  * Synchronously write back the locked page and any subsequent non-locked dirty
390  * pages.
391  */
392 static int afs_write_back_from_locked_page(struct address_space *mapping,
393 					   struct writeback_control *wbc,
394 					   struct page *primary_page,
395 					   pgoff_t final_page)
396 {
397 	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
398 	struct page *pages[8], *page;
399 	unsigned long count, priv;
400 	unsigned n, offset, to, f, t;
401 	pgoff_t start, first, last;
402 	int loop, ret;
403 
404 	_enter(",%lx", primary_page->index);
405 
406 	count = 1;
407 	if (test_set_page_writeback(primary_page))
408 		BUG();
409 
410 	/* Find all consecutive lockable dirty pages that have contiguous
411 	 * written regions, stopping when we find a page that is not
412 	 * immediately lockable, is not dirty or is missing, or we reach the
413 	 * end of the range.
414 	 */
415 	start = primary_page->index;
416 	priv = page_private(primary_page);
417 	offset = priv & AFS_PRIV_MAX;
418 	to = priv >> AFS_PRIV_SHIFT;
419 	trace_afs_page_dirty(vnode, tracepoint_string("store"),
420 			     primary_page->index, priv);
421 
422 	WARN_ON(offset == to);
423 	if (offset == to)
424 		trace_afs_page_dirty(vnode, tracepoint_string("WARN"),
425 				     primary_page->index, priv);
426 
427 	if (start >= final_page ||
428 	    (to < PAGE_SIZE && !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)))
429 		goto no_more;
430 
431 	start++;
432 	do {
433 		_debug("more %lx [%lx]", start, count);
434 		n = final_page - start + 1;
435 		if (n > ARRAY_SIZE(pages))
436 			n = ARRAY_SIZE(pages);
437 		n = find_get_pages_contig(mapping, start, ARRAY_SIZE(pages), pages);
438 		_debug("fgpc %u", n);
439 		if (n == 0)
440 			goto no_more;
441 		if (pages[0]->index != start) {
442 			do {
443 				put_page(pages[--n]);
444 			} while (n > 0);
445 			goto no_more;
446 		}
447 
448 		for (loop = 0; loop < n; loop++) {
449 			page = pages[loop];
450 			if (to != PAGE_SIZE &&
451 			    !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags))
452 				break;
453 			if (page->index > final_page)
454 				break;
455 			if (!trylock_page(page))
456 				break;
457 			if (!PageDirty(page) || PageWriteback(page)) {
458 				unlock_page(page);
459 				break;
460 			}
461 
462 			priv = page_private(page);
463 			f = priv & AFS_PRIV_MAX;
464 			t = priv >> AFS_PRIV_SHIFT;
465 			if (f != 0 &&
466 			    !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)) {
467 				unlock_page(page);
468 				break;
469 			}
470 			to = t;
471 
472 			trace_afs_page_dirty(vnode, tracepoint_string("store+"),
473 					     page->index, priv);
474 
475 			if (!clear_page_dirty_for_io(page))
476 				BUG();
477 			if (test_set_page_writeback(page))
478 				BUG();
479 			unlock_page(page);
480 			put_page(page);
481 		}
482 		count += loop;
483 		if (loop < n) {
484 			for (; loop < n; loop++)
485 				put_page(pages[loop]);
486 			goto no_more;
487 		}
488 
489 		start += loop;
490 	} while (start <= final_page && count < 65536);
491 
492 no_more:
493 	/* We now have a contiguous set of dirty pages, each with writeback
494 	 * set; the first page is still locked at this point, but all the rest
495 	 * have been unlocked.
496 	 */
497 	unlock_page(primary_page);
498 
499 	first = primary_page->index;
500 	last = first + count - 1;
501 
502 	_debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
503 
504 	ret = afs_store_data(mapping, first, last, offset, to);
505 	switch (ret) {
506 	case 0:
507 		ret = count;
508 		break;
509 
510 	default:
511 		pr_notice("kAFS: Unexpected error from FS.StoreData %d\n", ret);
512 		/* Fall through */
513 	case -EACCES:
514 	case -EPERM:
515 	case -ENOKEY:
516 	case -EKEYEXPIRED:
517 	case -EKEYREJECTED:
518 	case -EKEYREVOKED:
519 		afs_redirty_pages(wbc, mapping, first, last);
520 		mapping_set_error(mapping, ret);
521 		break;
522 
523 	case -EDQUOT:
524 	case -ENOSPC:
525 		afs_redirty_pages(wbc, mapping, first, last);
526 		mapping_set_error(mapping, -ENOSPC);
527 		break;
528 
529 	case -EROFS:
530 	case -EIO:
531 	case -EREMOTEIO:
532 	case -EFBIG:
533 	case -ENOENT:
534 	case -ENOMEDIUM:
535 	case -ENXIO:
536 		afs_kill_pages(mapping, first, last);
537 		mapping_set_error(mapping, ret);
538 		break;
539 	}
540 
541 	_leave(" = %d", ret);
542 	return ret;
543 }
544 
545 /*
546  * write a page back to the server
547  * - the caller locked the page for us
548  */
549 int afs_writepage(struct page *page, struct writeback_control *wbc)
550 {
551 	int ret;
552 
553 	_enter("{%lx},", page->index);
554 
555 	ret = afs_write_back_from_locked_page(page->mapping, wbc, page,
556 					      wbc->range_end >> PAGE_SHIFT);
557 	if (ret < 0) {
558 		_leave(" = %d", ret);
559 		return 0;
560 	}
561 
562 	wbc->nr_to_write -= ret;
563 
564 	_leave(" = 0");
565 	return 0;
566 }
567 
568 /*
569  * write a region of pages back to the server
570  */
571 static int afs_writepages_region(struct address_space *mapping,
572 				 struct writeback_control *wbc,
573 				 pgoff_t index, pgoff_t end, pgoff_t *_next)
574 {
575 	struct page *page;
576 	int ret, n;
577 
578 	_enter(",,%lx,%lx,", index, end);
579 
580 	do {
581 		n = find_get_pages_range_tag(mapping, &index, end,
582 					PAGECACHE_TAG_DIRTY, 1, &page);
583 		if (!n)
584 			break;
585 
586 		_debug("wback %lx", page->index);
587 
588 		/*
589 		 * at this point we hold neither the i_pages lock nor the
590 		 * page lock: the page may be truncated or invalidated
591 		 * (changing page->mapping to NULL), or even swizzled
592 		 * back from swapper_space to tmpfs file mapping
593 		 */
594 		ret = lock_page_killable(page);
595 		if (ret < 0) {
596 			put_page(page);
597 			_leave(" = %d", ret);
598 			return ret;
599 		}
600 
601 		if (page->mapping != mapping || !PageDirty(page)) {
602 			unlock_page(page);
603 			put_page(page);
604 			continue;
605 		}
606 
607 		if (PageWriteback(page)) {
608 			unlock_page(page);
609 			if (wbc->sync_mode != WB_SYNC_NONE)
610 				wait_on_page_writeback(page);
611 			put_page(page);
612 			continue;
613 		}
614 
615 		if (!clear_page_dirty_for_io(page))
616 			BUG();
617 		ret = afs_write_back_from_locked_page(mapping, wbc, page, end);
618 		put_page(page);
619 		if (ret < 0) {
620 			_leave(" = %d", ret);
621 			return ret;
622 		}
623 
624 		wbc->nr_to_write -= ret;
625 
626 		cond_resched();
627 	} while (index < end && wbc->nr_to_write > 0);
628 
629 	*_next = index;
630 	_leave(" = 0 [%lx]", *_next);
631 	return 0;
632 }
633 
634 /*
635  * write some of the pending data back to the server
636  */
637 int afs_writepages(struct address_space *mapping,
638 		   struct writeback_control *wbc)
639 {
640 	pgoff_t start, end, next;
641 	int ret;
642 
643 	_enter("");
644 
645 	if (wbc->range_cyclic) {
646 		start = mapping->writeback_index;
647 		end = -1;
648 		ret = afs_writepages_region(mapping, wbc, start, end, &next);
649 		if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
650 			ret = afs_writepages_region(mapping, wbc, 0, start,
651 						    &next);
652 		mapping->writeback_index = next;
653 	} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
654 		end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT);
655 		ret = afs_writepages_region(mapping, wbc, 0, end, &next);
656 		if (wbc->nr_to_write > 0)
657 			mapping->writeback_index = next;
658 	} else {
659 		start = wbc->range_start >> PAGE_SHIFT;
660 		end = wbc->range_end >> PAGE_SHIFT;
661 		ret = afs_writepages_region(mapping, wbc, start, end, &next);
662 	}
663 
664 	_leave(" = %d", ret);
665 	return ret;
666 }
667 
668 /*
669  * completion of write to server
670  */
671 void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
672 {
673 	struct pagevec pv;
674 	unsigned long priv;
675 	unsigned count, loop;
676 	pgoff_t first = call->first, last = call->last;
677 
678 	_enter("{%x:%u},{%lx-%lx}",
679 	       vnode->fid.vid, vnode->fid.vnode, first, last);
680 
681 	pagevec_init(&pv);
682 
683 	do {
684 		_debug("done %lx-%lx", first, last);
685 
686 		count = last - first + 1;
687 		if (count > PAGEVEC_SIZE)
688 			count = PAGEVEC_SIZE;
689 		pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
690 					      first, count, pv.pages);
691 		ASSERTCMP(pv.nr, ==, count);
692 
693 		for (loop = 0; loop < count; loop++) {
694 			priv = page_private(pv.pages[loop]);
695 			trace_afs_page_dirty(vnode, tracepoint_string("clear"),
696 					     pv.pages[loop]->index, priv);
697 			set_page_private(pv.pages[loop], 0);
698 			end_page_writeback(pv.pages[loop]);
699 		}
700 		first += count;
701 		__pagevec_release(&pv);
702 	} while (first <= last);
703 
704 	afs_prune_wb_keys(vnode);
705 	_leave("");
706 }
707 
708 /*
709  * write to an AFS file
710  */
711 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
712 {
713 	struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
714 	ssize_t result;
715 	size_t count = iov_iter_count(from);
716 
717 	_enter("{%x.%u},{%zu},",
718 	       vnode->fid.vid, vnode->fid.vnode, count);
719 
720 	if (IS_SWAPFILE(&vnode->vfs_inode)) {
721 		printk(KERN_INFO
722 		       "AFS: Attempt to write to active swap file!\n");
723 		return -EBUSY;
724 	}
725 
726 	if (!count)
727 		return 0;
728 
729 	result = generic_file_write_iter(iocb, from);
730 
731 	_leave(" = %zd", result);
732 	return result;
733 }
734 
735 /*
736  * flush any dirty pages for this process, and check for write errors.
737  * - the return status from this call provides a reliable indication of
738  *   whether any write errors occurred for this process.
739  */
740 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
741 {
742 	struct inode *inode = file_inode(file);
743 	struct afs_vnode *vnode = AFS_FS_I(inode);
744 
745 	_enter("{%x:%u},{n=%pD},%d",
746 	       vnode->fid.vid, vnode->fid.vnode, file,
747 	       datasync);
748 
749 	return file_write_and_wait_range(file, start, end);
750 }
751 
752 /*
753  * notification that a previously read-only page is about to become writable
754  * - if it returns an error, the caller will deliver a bus error signal
755  */
756 int afs_page_mkwrite(struct vm_fault *vmf)
757 {
758 	struct file *file = vmf->vma->vm_file;
759 	struct inode *inode = file_inode(file);
760 	struct afs_vnode *vnode = AFS_FS_I(inode);
761 	unsigned long priv;
762 
763 	_enter("{{%x:%u}},{%lx}",
764 	       vnode->fid.vid, vnode->fid.vnode, vmf->page->index);
765 
766 	sb_start_pagefault(inode->i_sb);
767 
768 	/* Wait for the page to be written to the cache before we allow it to
769 	 * be modified.  We then assume the entire page will need writing back.
770 	 */
771 #ifdef CONFIG_AFS_FSCACHE
772 	fscache_wait_on_page_write(vnode->cache, vmf->page);
773 #endif
774 
775 	if (PageWriteback(vmf->page) &&
776 	    wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)
777 		return VM_FAULT_RETRY;
778 
779 	if (lock_page_killable(vmf->page) < 0)
780 		return VM_FAULT_RETRY;
781 
782 	/* We mustn't change page->private until writeback is complete as that
783 	 * details the portion of the page we need to write back and we might
784 	 * need to redirty the page if there's a problem.
785 	 */
786 	wait_on_page_writeback(vmf->page);
787 
788 	priv = (unsigned long)PAGE_SIZE << AFS_PRIV_SHIFT; /* To */
789 	priv |= 0; /* From */
790 	trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"),
791 			     vmf->page->index, priv);
792 	SetPagePrivate(vmf->page);
793 	set_page_private(vmf->page, priv);
794 
795 	sb_end_pagefault(inode->i_sb);
796 	return VM_FAULT_LOCKED;
797 }
798 
799 /*
800  * Prune the keys cached for writeback.  The caller must hold vnode->wb_lock.
801  */
802 void afs_prune_wb_keys(struct afs_vnode *vnode)
803 {
804 	LIST_HEAD(graveyard);
805 	struct afs_wb_key *wbk, *tmp;
806 
807 	/* Discard unused keys */
808 	spin_lock(&vnode->wb_lock);
809 
810 	if (!mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_WRITEBACK) &&
811 	    !mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_DIRTY)) {
812 		list_for_each_entry_safe(wbk, tmp, &vnode->wb_keys, vnode_link) {
813 			if (refcount_read(&wbk->usage) == 1)
814 				list_move(&wbk->vnode_link, &graveyard);
815 		}
816 	}
817 
818 	spin_unlock(&vnode->wb_lock);
819 
820 	while (!list_empty(&graveyard)) {
821 		wbk = list_entry(graveyard.next, struct afs_wb_key, vnode_link);
822 		list_del(&wbk->vnode_link);
823 		afs_put_wb_key(wbk);
824 	}
825 }
826 
827 /*
828  * Clean up a page during invalidation.
829  */
830 int afs_launder_page(struct page *page)
831 {
832 	struct address_space *mapping = page->mapping;
833 	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
834 	unsigned long priv;
835 	unsigned int f, t;
836 	int ret = 0;
837 
838 	_enter("{%lx}", page->index);
839 
840 	priv = page_private(page);
841 	if (clear_page_dirty_for_io(page)) {
842 		f = 0;
843 		t = PAGE_SIZE;
844 		if (PagePrivate(page)) {
845 			f = priv & AFS_PRIV_MAX;
846 			t = priv >> AFS_PRIV_SHIFT;
847 		}
848 
849 		trace_afs_page_dirty(vnode, tracepoint_string("launder"),
850 				     page->index, priv);
851 		ret = afs_store_data(mapping, page->index, page->index, t, f);
852 	}
853 
854 	trace_afs_page_dirty(vnode, tracepoint_string("laundered"),
855 			     page->index, priv);
856 	set_page_private(page, 0);
857 	ClearPagePrivate(page);
858 
859 #ifdef CONFIG_AFS_FSCACHE
860 	if (PageFsCache(page)) {
861 		fscache_wait_on_page_write(vnode->cache, page);
862 		fscache_uncache_page(vnode->cache, page);
863 	}
864 #endif
865 	return ret;
866 }
867