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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Storage object read/write
3 *
4 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#include <linux/mount.h>
9#include <linux/slab.h>
10#include <linux/file.h>
11#include <linux/swap.h>
12#include "internal.h"
13
14/*
15 * detect wake up events generated by the unlocking of pages in which we're
16 * interested
17 * - we use this to detect read completion of backing pages
18 * - the caller holds the waitqueue lock
19 */
20static int cachefiles_read_waiter(wait_queue_entry_t *wait, unsigned mode,
21 int sync, void *_key)
22{
23 struct cachefiles_one_read *monitor =
24 container_of(wait, struct cachefiles_one_read, monitor);
25 struct cachefiles_object *object;
26 struct fscache_retrieval *op = monitor->op;
27 struct wait_bit_key *key = _key;
28 struct page *page = wait->private;
29
30 ASSERT(key);
31
32 _enter("{%lu},%u,%d,{%p,%u}",
33 monitor->netfs_page->index, mode, sync,
34 key->flags, key->bit_nr);
35
36 if (key->flags != &page->flags ||
37 key->bit_nr != PG_locked)
38 return 0;
39
40 _debug("--- monitor %p %lx ---", page, page->flags);
41
42 if (!PageUptodate(page) && !PageError(page)) {
43 /* unlocked, not uptodate and not erronous? */
44 _debug("page probably truncated");
45 }
46
47 /* remove from the waitqueue */
48 list_del(&wait->entry);
49
50 /* move onto the action list and queue for FS-Cache thread pool */
51 ASSERT(op);
52
53 /* We need to temporarily bump the usage count as we don't own a ref
54 * here otherwise cachefiles_read_copier() may free the op between the
55 * monitor being enqueued on the op->to_do list and the op getting
56 * enqueued on the work queue.
57 */
58 fscache_get_retrieval(op);
59
60 object = container_of(op->op.object, struct cachefiles_object, fscache);
61 spin_lock(&object->work_lock);
62 list_add_tail(&monitor->op_link, &op->to_do);
63 fscache_enqueue_retrieval(op);
64 spin_unlock(&object->work_lock);
65
66 fscache_put_retrieval(op);
67 return 0;
68}
69
70/*
71 * handle a probably truncated page
72 * - check to see if the page is still relevant and reissue the read if
73 * possible
74 * - return -EIO on error, -ENODATA if the page is gone, -EINPROGRESS if we
75 * must wait again and 0 if successful
76 */
77static int cachefiles_read_reissue(struct cachefiles_object *object,
78 struct cachefiles_one_read *monitor)
79{
80 struct address_space *bmapping = d_backing_inode(object->backer)->i_mapping;
81 struct page *backpage = monitor->back_page, *backpage2;
82 int ret;
83
84 _enter("{ino=%lx},{%lx,%lx}",
85 d_backing_inode(object->backer)->i_ino,
86 backpage->index, backpage->flags);
87
88 /* skip if the page was truncated away completely */
89 if (backpage->mapping != bmapping) {
90 _leave(" = -ENODATA [mapping]");
91 return -ENODATA;
92 }
93
94 backpage2 = find_get_page(bmapping, backpage->index);
95 if (!backpage2) {
96 _leave(" = -ENODATA [gone]");
97 return -ENODATA;
98 }
99
100 if (backpage != backpage2) {
101 put_page(backpage2);
102 _leave(" = -ENODATA [different]");
103 return -ENODATA;
104 }
105
106 /* the page is still there and we already have a ref on it, so we don't
107 * need a second */
108 put_page(backpage2);
109
110 INIT_LIST_HEAD(&monitor->op_link);
111 add_page_wait_queue(backpage, &monitor->monitor);
112
113 if (trylock_page(backpage)) {
114 ret = -EIO;
115 if (PageError(backpage))
116 goto unlock_discard;
117 ret = 0;
118 if (PageUptodate(backpage))
119 goto unlock_discard;
120
121 _debug("reissue read");
122 ret = bmapping->a_ops->readpage(NULL, backpage);
123 if (ret < 0)
124 goto unlock_discard;
125 }
126
127 /* but the page may have been read before the monitor was installed, so
128 * the monitor may miss the event - so we have to ensure that we do get
129 * one in such a case */
130 if (trylock_page(backpage)) {
131 _debug("jumpstart %p {%lx}", backpage, backpage->flags);
132 unlock_page(backpage);
133 }
134
135 /* it'll reappear on the todo list */
136 _leave(" = -EINPROGRESS");
137 return -EINPROGRESS;
138
139unlock_discard:
140 unlock_page(backpage);
141 spin_lock_irq(&object->work_lock);
142 list_del(&monitor->op_link);
143 spin_unlock_irq(&object->work_lock);
144 _leave(" = %d", ret);
145 return ret;
146}
147
148/*
149 * copy data from backing pages to netfs pages to complete a read operation
150 * - driven by FS-Cache's thread pool
151 */
152static void cachefiles_read_copier(struct fscache_operation *_op)
153{
154 struct cachefiles_one_read *monitor;
155 struct cachefiles_object *object;
156 struct fscache_retrieval *op;
157 int error, max;
158
159 op = container_of(_op, struct fscache_retrieval, op);
160 object = container_of(op->op.object,
161 struct cachefiles_object, fscache);
162
163 _enter("{ino=%lu}", d_backing_inode(object->backer)->i_ino);
164
165 max = 8;
166 spin_lock_irq(&object->work_lock);
167
168 while (!list_empty(&op->to_do)) {
169 monitor = list_entry(op->to_do.next,
170 struct cachefiles_one_read, op_link);
171 list_del(&monitor->op_link);
172
173 spin_unlock_irq(&object->work_lock);
174
175 _debug("- copy {%lu}", monitor->back_page->index);
176
177 recheck:
178 if (test_bit(FSCACHE_COOKIE_INVALIDATING,
179 &object->fscache.cookie->flags)) {
180 error = -ESTALE;
181 } else if (PageUptodate(monitor->back_page)) {
182 copy_highpage(monitor->netfs_page, monitor->back_page);
183 fscache_mark_page_cached(monitor->op,
184 monitor->netfs_page);
185 error = 0;
186 } else if (!PageError(monitor->back_page)) {
187 /* the page has probably been truncated */
188 error = cachefiles_read_reissue(object, monitor);
189 if (error == -EINPROGRESS)
190 goto next;
191 goto recheck;
192 } else {
193 cachefiles_io_error_obj(
194 object,
195 "Readpage failed on backing file %lx",
196 (unsigned long) monitor->back_page->flags);
197 error = -EIO;
198 }
199
200 put_page(monitor->back_page);
201
202 fscache_end_io(op, monitor->netfs_page, error);
203 put_page(monitor->netfs_page);
204 fscache_retrieval_complete(op, 1);
205 fscache_put_retrieval(op);
206 kfree(monitor);
207
208 next:
209 /* let the thread pool have some air occasionally */
210 max--;
211 if (max < 0 || need_resched()) {
212 if (!list_empty(&op->to_do))
213 fscache_enqueue_retrieval(op);
214 _leave(" [maxed out]");
215 return;
216 }
217
218 spin_lock_irq(&object->work_lock);
219 }
220
221 spin_unlock_irq(&object->work_lock);
222 _leave("");
223}
224
225/*
226 * read the corresponding page to the given set from the backing file
227 * - an uncertain page is simply discarded, to be tried again another time
228 */
229static int cachefiles_read_backing_file_one(struct cachefiles_object *object,
230 struct fscache_retrieval *op,
231 struct page *netpage)
232{
233 struct cachefiles_one_read *monitor;
234 struct address_space *bmapping;
235 struct page *newpage, *backpage;
236 int ret;
237
238 _enter("");
239
240 _debug("read back %p{%lu,%d}",
241 netpage, netpage->index, page_count(netpage));
242
243 monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
244 if (!monitor)
245 goto nomem;
246
247 monitor->netfs_page = netpage;
248 monitor->op = fscache_get_retrieval(op);
249
250 init_waitqueue_func_entry(&monitor->monitor, cachefiles_read_waiter);
251
252 /* attempt to get hold of the backing page */
253 bmapping = d_backing_inode(object->backer)->i_mapping;
254 newpage = NULL;
255
256 for (;;) {
257 backpage = find_get_page(bmapping, netpage->index);
258 if (backpage)
259 goto backing_page_already_present;
260
261 if (!newpage) {
262 newpage = __page_cache_alloc(cachefiles_gfp);
263 if (!newpage)
264 goto nomem_monitor;
265 }
266
267 ret = add_to_page_cache_lru(newpage, bmapping,
268 netpage->index, cachefiles_gfp);
269 if (ret == 0)
270 goto installed_new_backing_page;
271 if (ret != -EEXIST)
272 goto nomem_page;
273 }
274
275 /* we've installed a new backing page, so now we need to start
276 * it reading */
277installed_new_backing_page:
278 _debug("- new %p", newpage);
279
280 backpage = newpage;
281 newpage = NULL;
282
283read_backing_page:
284 ret = bmapping->a_ops->readpage(NULL, backpage);
285 if (ret < 0)
286 goto read_error;
287
288 /* set the monitor to transfer the data across */
289monitor_backing_page:
290 _debug("- monitor add");
291
292 /* install the monitor */
293 get_page(monitor->netfs_page);
294 get_page(backpage);
295 monitor->back_page = backpage;
296 monitor->monitor.private = backpage;
297 add_page_wait_queue(backpage, &monitor->monitor);
298 monitor = NULL;
299
300 /* but the page may have been read before the monitor was installed, so
301 * the monitor may miss the event - so we have to ensure that we do get
302 * one in such a case */
303 if (trylock_page(backpage)) {
304 _debug("jumpstart %p {%lx}", backpage, backpage->flags);
305 unlock_page(backpage);
306 }
307 goto success;
308
309 /* if the backing page is already present, it can be in one of
310 * three states: read in progress, read failed or read okay */
311backing_page_already_present:
312 _debug("- present");
313
314 if (newpage) {
315 put_page(newpage);
316 newpage = NULL;
317 }
318
319 if (PageError(backpage))
320 goto io_error;
321
322 if (PageUptodate(backpage))
323 goto backing_page_already_uptodate;
324
325 if (!trylock_page(backpage))
326 goto monitor_backing_page;
327 _debug("read %p {%lx}", backpage, backpage->flags);
328 goto read_backing_page;
329
330 /* the backing page is already up to date, attach the netfs
331 * page to the pagecache and LRU and copy the data across */
332backing_page_already_uptodate:
333 _debug("- uptodate");
334
335 fscache_mark_page_cached(op, netpage);
336
337 copy_highpage(netpage, backpage);
338 fscache_end_io(op, netpage, 0);
339 fscache_retrieval_complete(op, 1);
340
341success:
342 _debug("success");
343 ret = 0;
344
345out:
346 if (backpage)
347 put_page(backpage);
348 if (monitor) {
349 fscache_put_retrieval(monitor->op);
350 kfree(monitor);
351 }
352 _leave(" = %d", ret);
353 return ret;
354
355read_error:
356 _debug("read error %d", ret);
357 if (ret == -ENOMEM) {
358 fscache_retrieval_complete(op, 1);
359 goto out;
360 }
361io_error:
362 cachefiles_io_error_obj(object, "Page read error on backing file");
363 fscache_retrieval_complete(op, 1);
364 ret = -ENOBUFS;
365 goto out;
366
367nomem_page:
368 put_page(newpage);
369nomem_monitor:
370 fscache_put_retrieval(monitor->op);
371 kfree(monitor);
372nomem:
373 fscache_retrieval_complete(op, 1);
374 _leave(" = -ENOMEM");
375 return -ENOMEM;
376}
377
378/*
379 * read a page from the cache or allocate a block in which to store it
380 * - cache withdrawal is prevented by the caller
381 * - returns -EINTR if interrupted
382 * - returns -ENOMEM if ran out of memory
383 * - returns -ENOBUFS if no buffers can be made available
384 * - returns -ENOBUFS if page is beyond EOF
385 * - if the page is backed by a block in the cache:
386 * - a read will be started which will call the callback on completion
387 * - 0 will be returned
388 * - else if the page is unbacked:
389 * - the metadata will be retained
390 * - -ENODATA will be returned
391 */
392int cachefiles_read_or_alloc_page(struct fscache_retrieval *op,
393 struct page *page,
394 gfp_t gfp)
395{
396 struct cachefiles_object *object;
397 struct cachefiles_cache *cache;
398 struct inode *inode;
399 sector_t block;
400 unsigned shift;
401 int ret, ret2;
402
403 object = container_of(op->op.object,
404 struct cachefiles_object, fscache);
405 cache = container_of(object->fscache.cache,
406 struct cachefiles_cache, cache);
407
408 _enter("{%p},{%lx},,,", object, page->index);
409
410 if (!object->backer)
411 goto enobufs;
412
413 inode = d_backing_inode(object->backer);
414 ASSERT(S_ISREG(inode->i_mode));
415 ASSERT(inode->i_mapping->a_ops->readpages);
416
417 /* calculate the shift required to use bmap */
418 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
419
420 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
421 op->op.flags |= FSCACHE_OP_ASYNC;
422 op->op.processor = cachefiles_read_copier;
423
424 /* we assume the absence or presence of the first block is a good
425 * enough indication for the page as a whole
426 * - TODO: don't use bmap() for this as it is _not_ actually good
427 * enough for this as it doesn't indicate errors, but it's all we've
428 * got for the moment
429 */
430 block = page->index;
431 block <<= shift;
432
433 ret2 = bmap(inode, &block);
434 ASSERT(ret2 == 0);
435
436 _debug("%llx -> %llx",
437 (unsigned long long) (page->index << shift),
438 (unsigned long long) block);
439
440 if (block) {
441 /* submit the apparently valid page to the backing fs to be
442 * read from disk */
443 ret = cachefiles_read_backing_file_one(object, op, page);
444 } else if (cachefiles_has_space(cache, 0, 1) == 0) {
445 /* there's space in the cache we can use */
446 fscache_mark_page_cached(op, page);
447 fscache_retrieval_complete(op, 1);
448 ret = -ENODATA;
449 } else {
450 goto enobufs;
451 }
452
453 _leave(" = %d", ret);
454 return ret;
455
456enobufs:
457 fscache_retrieval_complete(op, 1);
458 _leave(" = -ENOBUFS");
459 return -ENOBUFS;
460}
461
462/*
463 * read the corresponding pages to the given set from the backing file
464 * - any uncertain pages are simply discarded, to be tried again another time
465 */
466static int cachefiles_read_backing_file(struct cachefiles_object *object,
467 struct fscache_retrieval *op,
468 struct list_head *list)
469{
470 struct cachefiles_one_read *monitor = NULL;
471 struct address_space *bmapping = d_backing_inode(object->backer)->i_mapping;
472 struct page *newpage = NULL, *netpage, *_n, *backpage = NULL;
473 int ret = 0;
474
475 _enter("");
476
477 list_for_each_entry_safe(netpage, _n, list, lru) {
478 list_del(&netpage->lru);
479
480 _debug("read back %p{%lu,%d}",
481 netpage, netpage->index, page_count(netpage));
482
483 if (!monitor) {
484 monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
485 if (!monitor)
486 goto nomem;
487
488 monitor->op = fscache_get_retrieval(op);
489 init_waitqueue_func_entry(&monitor->monitor,
490 cachefiles_read_waiter);
491 }
492
493 for (;;) {
494 backpage = find_get_page(bmapping, netpage->index);
495 if (backpage)
496 goto backing_page_already_present;
497
498 if (!newpage) {
499 newpage = __page_cache_alloc(cachefiles_gfp);
500 if (!newpage)
501 goto nomem;
502 }
503
504 ret = add_to_page_cache_lru(newpage, bmapping,
505 netpage->index,
506 cachefiles_gfp);
507 if (ret == 0)
508 goto installed_new_backing_page;
509 if (ret != -EEXIST)
510 goto nomem;
511 }
512
513 /* we've installed a new backing page, so now we need
514 * to start it reading */
515 installed_new_backing_page:
516 _debug("- new %p", newpage);
517
518 backpage = newpage;
519 newpage = NULL;
520
521 reread_backing_page:
522 ret = bmapping->a_ops->readpage(NULL, backpage);
523 if (ret < 0)
524 goto read_error;
525
526 /* add the netfs page to the pagecache and LRU, and set the
527 * monitor to transfer the data across */
528 monitor_backing_page:
529 _debug("- monitor add");
530
531 ret = add_to_page_cache_lru(netpage, op->mapping,
532 netpage->index, cachefiles_gfp);
533 if (ret < 0) {
534 if (ret == -EEXIST) {
535 put_page(backpage);
536 backpage = NULL;
537 put_page(netpage);
538 netpage = NULL;
539 fscache_retrieval_complete(op, 1);
540 continue;
541 }
542 goto nomem;
543 }
544
545 /* install a monitor */
546 get_page(netpage);
547 monitor->netfs_page = netpage;
548
549 get_page(backpage);
550 monitor->back_page = backpage;
551 monitor->monitor.private = backpage;
552 add_page_wait_queue(backpage, &monitor->monitor);
553 monitor = NULL;
554
555 /* but the page may have been read before the monitor was
556 * installed, so the monitor may miss the event - so we have to
557 * ensure that we do get one in such a case */
558 if (trylock_page(backpage)) {
559 _debug("2unlock %p {%lx}", backpage, backpage->flags);
560 unlock_page(backpage);
561 }
562
563 put_page(backpage);
564 backpage = NULL;
565
566 put_page(netpage);
567 netpage = NULL;
568 continue;
569
570 /* if the backing page is already present, it can be in one of
571 * three states: read in progress, read failed or read okay */
572 backing_page_already_present:
573 _debug("- present %p", backpage);
574
575 if (PageError(backpage))
576 goto io_error;
577
578 if (PageUptodate(backpage))
579 goto backing_page_already_uptodate;
580
581 _debug("- not ready %p{%lx}", backpage, backpage->flags);
582
583 if (!trylock_page(backpage))
584 goto monitor_backing_page;
585
586 if (PageError(backpage)) {
587 _debug("error %lx", backpage->flags);
588 unlock_page(backpage);
589 goto io_error;
590 }
591
592 if (PageUptodate(backpage))
593 goto backing_page_already_uptodate_unlock;
594
595 /* we've locked a page that's neither up to date nor erroneous,
596 * so we need to attempt to read it again */
597 goto reread_backing_page;
598
599 /* the backing page is already up to date, attach the netfs
600 * page to the pagecache and LRU and copy the data across */
601 backing_page_already_uptodate_unlock:
602 _debug("uptodate %lx", backpage->flags);
603 unlock_page(backpage);
604 backing_page_already_uptodate:
605 _debug("- uptodate");
606
607 ret = add_to_page_cache_lru(netpage, op->mapping,
608 netpage->index, cachefiles_gfp);
609 if (ret < 0) {
610 if (ret == -EEXIST) {
611 put_page(backpage);
612 backpage = NULL;
613 put_page(netpage);
614 netpage = NULL;
615 fscache_retrieval_complete(op, 1);
616 continue;
617 }
618 goto nomem;
619 }
620
621 copy_highpage(netpage, backpage);
622
623 put_page(backpage);
624 backpage = NULL;
625
626 fscache_mark_page_cached(op, netpage);
627
628 /* the netpage is unlocked and marked up to date here */
629 fscache_end_io(op, netpage, 0);
630 put_page(netpage);
631 netpage = NULL;
632 fscache_retrieval_complete(op, 1);
633 continue;
634 }
635
636 netpage = NULL;
637
638 _debug("out");
639
640out:
641 /* tidy up */
642 if (newpage)
643 put_page(newpage);
644 if (netpage)
645 put_page(netpage);
646 if (backpage)
647 put_page(backpage);
648 if (monitor) {
649 fscache_put_retrieval(op);
650 kfree(monitor);
651 }
652
653 list_for_each_entry_safe(netpage, _n, list, lru) {
654 list_del(&netpage->lru);
655 put_page(netpage);
656 fscache_retrieval_complete(op, 1);
657 }
658
659 _leave(" = %d", ret);
660 return ret;
661
662nomem:
663 _debug("nomem");
664 ret = -ENOMEM;
665 goto record_page_complete;
666
667read_error:
668 _debug("read error %d", ret);
669 if (ret == -ENOMEM)
670 goto record_page_complete;
671io_error:
672 cachefiles_io_error_obj(object, "Page read error on backing file");
673 ret = -ENOBUFS;
674record_page_complete:
675 fscache_retrieval_complete(op, 1);
676 goto out;
677}
678
679/*
680 * read a list of pages from the cache or allocate blocks in which to store
681 * them
682 */
683int cachefiles_read_or_alloc_pages(struct fscache_retrieval *op,
684 struct list_head *pages,
685 unsigned *nr_pages,
686 gfp_t gfp)
687{
688 struct cachefiles_object *object;
689 struct cachefiles_cache *cache;
690 struct list_head backpages;
691 struct pagevec pagevec;
692 struct inode *inode;
693 struct page *page, *_n;
694 unsigned shift, nrbackpages;
695 int ret, ret2, space;
696
697 object = container_of(op->op.object,
698 struct cachefiles_object, fscache);
699 cache = container_of(object->fscache.cache,
700 struct cachefiles_cache, cache);
701
702 _enter("{OBJ%x,%d},,%d,,",
703 object->fscache.debug_id, atomic_read(&op->op.usage),
704 *nr_pages);
705
706 if (!object->backer)
707 goto all_enobufs;
708
709 space = 1;
710 if (cachefiles_has_space(cache, 0, *nr_pages) < 0)
711 space = 0;
712
713 inode = d_backing_inode(object->backer);
714 ASSERT(S_ISREG(inode->i_mode));
715 ASSERT(inode->i_mapping->a_ops->readpages);
716
717 /* calculate the shift required to use bmap */
718 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
719
720 pagevec_init(&pagevec);
721
722 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
723 op->op.flags |= FSCACHE_OP_ASYNC;
724 op->op.processor = cachefiles_read_copier;
725
726 INIT_LIST_HEAD(&backpages);
727 nrbackpages = 0;
728
729 ret = space ? -ENODATA : -ENOBUFS;
730 list_for_each_entry_safe(page, _n, pages, lru) {
731 sector_t block;
732
733 /* we assume the absence or presence of the first block is a
734 * good enough indication for the page as a whole
735 * - TODO: don't use bmap() for this as it is _not_ actually
736 * good enough for this as it doesn't indicate errors, but
737 * it's all we've got for the moment
738 */
739 block = page->index;
740 block <<= shift;
741
742 ret2 = bmap(inode, &block);
743 ASSERT(ret2 == 0);
744
745 _debug("%llx -> %llx",
746 (unsigned long long) (page->index << shift),
747 (unsigned long long) block);
748
749 if (block) {
750 /* we have data - add it to the list to give to the
751 * backing fs */
752 list_move(&page->lru, &backpages);
753 (*nr_pages)--;
754 nrbackpages++;
755 } else if (space && pagevec_add(&pagevec, page) == 0) {
756 fscache_mark_pages_cached(op, &pagevec);
757 fscache_retrieval_complete(op, 1);
758 ret = -ENODATA;
759 } else {
760 fscache_retrieval_complete(op, 1);
761 }
762 }
763
764 if (pagevec_count(&pagevec) > 0)
765 fscache_mark_pages_cached(op, &pagevec);
766
767 if (list_empty(pages))
768 ret = 0;
769
770 /* submit the apparently valid pages to the backing fs to be read from
771 * disk */
772 if (nrbackpages > 0) {
773 ret2 = cachefiles_read_backing_file(object, op, &backpages);
774 if (ret2 == -ENOMEM || ret2 == -EINTR)
775 ret = ret2;
776 }
777
778 _leave(" = %d [nr=%u%s]",
779 ret, *nr_pages, list_empty(pages) ? " empty" : "");
780 return ret;
781
782all_enobufs:
783 fscache_retrieval_complete(op, *nr_pages);
784 return -ENOBUFS;
785}
786
787/*
788 * allocate a block in the cache in which to store a page
789 * - cache withdrawal is prevented by the caller
790 * - returns -EINTR if interrupted
791 * - returns -ENOMEM if ran out of memory
792 * - returns -ENOBUFS if no buffers can be made available
793 * - returns -ENOBUFS if page is beyond EOF
794 * - otherwise:
795 * - the metadata will be retained
796 * - 0 will be returned
797 */
798int cachefiles_allocate_page(struct fscache_retrieval *op,
799 struct page *page,
800 gfp_t gfp)
801{
802 struct cachefiles_object *object;
803 struct cachefiles_cache *cache;
804 int ret;
805
806 object = container_of(op->op.object,
807 struct cachefiles_object, fscache);
808 cache = container_of(object->fscache.cache,
809 struct cachefiles_cache, cache);
810
811 _enter("%p,{%lx},", object, page->index);
812
813 ret = cachefiles_has_space(cache, 0, 1);
814 if (ret == 0)
815 fscache_mark_page_cached(op, page);
816 else
817 ret = -ENOBUFS;
818
819 fscache_retrieval_complete(op, 1);
820 _leave(" = %d", ret);
821 return ret;
822}
823
824/*
825 * allocate blocks in the cache in which to store a set of pages
826 * - cache withdrawal is prevented by the caller
827 * - returns -EINTR if interrupted
828 * - returns -ENOMEM if ran out of memory
829 * - returns -ENOBUFS if some buffers couldn't be made available
830 * - returns -ENOBUFS if some pages are beyond EOF
831 * - otherwise:
832 * - -ENODATA will be returned
833 * - metadata will be retained for any page marked
834 */
835int cachefiles_allocate_pages(struct fscache_retrieval *op,
836 struct list_head *pages,
837 unsigned *nr_pages,
838 gfp_t gfp)
839{
840 struct cachefiles_object *object;
841 struct cachefiles_cache *cache;
842 struct pagevec pagevec;
843 struct page *page;
844 int ret;
845
846 object = container_of(op->op.object,
847 struct cachefiles_object, fscache);
848 cache = container_of(object->fscache.cache,
849 struct cachefiles_cache, cache);
850
851 _enter("%p,,,%d,", object, *nr_pages);
852
853 ret = cachefiles_has_space(cache, 0, *nr_pages);
854 if (ret == 0) {
855 pagevec_init(&pagevec);
856
857 list_for_each_entry(page, pages, lru) {
858 if (pagevec_add(&pagevec, page) == 0)
859 fscache_mark_pages_cached(op, &pagevec);
860 }
861
862 if (pagevec_count(&pagevec) > 0)
863 fscache_mark_pages_cached(op, &pagevec);
864 ret = -ENODATA;
865 } else {
866 ret = -ENOBUFS;
867 }
868
869 fscache_retrieval_complete(op, *nr_pages);
870 _leave(" = %d", ret);
871 return ret;
872}
873
874/*
875 * request a page be stored in the cache
876 * - cache withdrawal is prevented by the caller
877 * - this request may be ignored if there's no cache block available, in which
878 * case -ENOBUFS will be returned
879 * - if the op is in progress, 0 will be returned
880 */
881int cachefiles_write_page(struct fscache_storage *op, struct page *page)
882{
883 struct cachefiles_object *object;
884 struct cachefiles_cache *cache;
885 struct file *file;
886 struct path path;
887 loff_t pos, eof;
888 size_t len;
889 void *data;
890 int ret = -ENOBUFS;
891
892 ASSERT(op != NULL);
893 ASSERT(page != NULL);
894
895 object = container_of(op->op.object,
896 struct cachefiles_object, fscache);
897
898 _enter("%p,%p{%lx},,,", object, page, page->index);
899
900 if (!object->backer) {
901 _leave(" = -ENOBUFS");
902 return -ENOBUFS;
903 }
904
905 ASSERT(d_is_reg(object->backer));
906
907 cache = container_of(object->fscache.cache,
908 struct cachefiles_cache, cache);
909
910 pos = (loff_t)page->index << PAGE_SHIFT;
911
912 /* We mustn't write more data than we have, so we have to beware of a
913 * partial page at EOF.
914 */
915 eof = object->fscache.store_limit_l;
916 if (pos >= eof)
917 goto error;
918
919 /* write the page to the backing filesystem and let it store it in its
920 * own time */
921 path.mnt = cache->mnt;
922 path.dentry = object->backer;
923 file = dentry_open(&path, O_RDWR | O_LARGEFILE, cache->cache_cred);
924 if (IS_ERR(file)) {
925 ret = PTR_ERR(file);
926 goto error_2;
927 }
928
929 len = PAGE_SIZE;
930 if (eof & ~PAGE_MASK) {
931 if (eof - pos < PAGE_SIZE) {
932 _debug("cut short %llx to %llx",
933 pos, eof);
934 len = eof - pos;
935 ASSERTCMP(pos + len, ==, eof);
936 }
937 }
938
939 data = kmap(page);
940 ret = kernel_write(file, data, len, &pos);
941 kunmap(page);
942 fput(file);
943 if (ret != len)
944 goto error_eio;
945
946 _leave(" = 0");
947 return 0;
948
949error_eio:
950 ret = -EIO;
951error_2:
952 if (ret == -EIO)
953 cachefiles_io_error_obj(object,
954 "Write page to backing file failed");
955error:
956 _leave(" = -ENOBUFS [%d]", ret);
957 return -ENOBUFS;
958}
959
960/*
961 * detach a backing block from a page
962 * - cache withdrawal is prevented by the caller
963 */
964void cachefiles_uncache_page(struct fscache_object *_object, struct page *page)
965 __releases(&object->fscache.cookie->lock)
966{
967 struct cachefiles_object *object;
968
969 object = container_of(_object, struct cachefiles_object, fscache);
970
971 _enter("%p,{%lu}", object, page->index);
972
973 spin_unlock(&object->fscache.cookie->lock);
974}