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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 spin_unlock(&object->work_lock);
64
65 fscache_enqueue_retrieval(op);
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 block0, block;
400 unsigned shift;
401 int ret;
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->bmap);
416 ASSERT(inode->i_mapping->a_ops->readpages);
417
418 /* calculate the shift required to use bmap */
419 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
420
421 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
422 op->op.flags |= FSCACHE_OP_ASYNC;
423 op->op.processor = cachefiles_read_copier;
424
425 /* we assume the absence or presence of the first block is a good
426 * enough indication for the page as a whole
427 * - TODO: don't use bmap() for this as it is _not_ actually good
428 * enough for this as it doesn't indicate errors, but it's all we've
429 * got for the moment
430 */
431 block0 = page->index;
432 block0 <<= shift;
433
434 block = inode->i_mapping->a_ops->bmap(inode->i_mapping, block0);
435 _debug("%llx -> %llx",
436 (unsigned long long) block0,
437 (unsigned long long) block);
438
439 if (block) {
440 /* submit the apparently valid page to the backing fs to be
441 * read from disk */
442 ret = cachefiles_read_backing_file_one(object, op, page);
443 } else if (cachefiles_has_space(cache, 0, 1) == 0) {
444 /* there's space in the cache we can use */
445 fscache_mark_page_cached(op, page);
446 fscache_retrieval_complete(op, 1);
447 ret = -ENODATA;
448 } else {
449 goto enobufs;
450 }
451
452 _leave(" = %d", ret);
453 return ret;
454
455enobufs:
456 fscache_retrieval_complete(op, 1);
457 _leave(" = -ENOBUFS");
458 return -ENOBUFS;
459}
460
461/*
462 * read the corresponding pages to the given set from the backing file
463 * - any uncertain pages are simply discarded, to be tried again another time
464 */
465static int cachefiles_read_backing_file(struct cachefiles_object *object,
466 struct fscache_retrieval *op,
467 struct list_head *list)
468{
469 struct cachefiles_one_read *monitor = NULL;
470 struct address_space *bmapping = d_backing_inode(object->backer)->i_mapping;
471 struct page *newpage = NULL, *netpage, *_n, *backpage = NULL;
472 int ret = 0;
473
474 _enter("");
475
476 list_for_each_entry_safe(netpage, _n, list, lru) {
477 list_del(&netpage->lru);
478
479 _debug("read back %p{%lu,%d}",
480 netpage, netpage->index, page_count(netpage));
481
482 if (!monitor) {
483 monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
484 if (!monitor)
485 goto nomem;
486
487 monitor->op = fscache_get_retrieval(op);
488 init_waitqueue_func_entry(&monitor->monitor,
489 cachefiles_read_waiter);
490 }
491
492 for (;;) {
493 backpage = find_get_page(bmapping, netpage->index);
494 if (backpage)
495 goto backing_page_already_present;
496
497 if (!newpage) {
498 newpage = __page_cache_alloc(cachefiles_gfp);
499 if (!newpage)
500 goto nomem;
501 }
502
503 ret = add_to_page_cache_lru(newpage, bmapping,
504 netpage->index,
505 cachefiles_gfp);
506 if (ret == 0)
507 goto installed_new_backing_page;
508 if (ret != -EEXIST)
509 goto nomem;
510 }
511
512 /* we've installed a new backing page, so now we need
513 * to start it reading */
514 installed_new_backing_page:
515 _debug("- new %p", newpage);
516
517 backpage = newpage;
518 newpage = NULL;
519
520 reread_backing_page:
521 ret = bmapping->a_ops->readpage(NULL, backpage);
522 if (ret < 0)
523 goto read_error;
524
525 /* add the netfs page to the pagecache and LRU, and set the
526 * monitor to transfer the data across */
527 monitor_backing_page:
528 _debug("- monitor add");
529
530 ret = add_to_page_cache_lru(netpage, op->mapping,
531 netpage->index, cachefiles_gfp);
532 if (ret < 0) {
533 if (ret == -EEXIST) {
534 put_page(backpage);
535 backpage = NULL;
536 put_page(netpage);
537 netpage = NULL;
538 fscache_retrieval_complete(op, 1);
539 continue;
540 }
541 goto nomem;
542 }
543
544 /* install a monitor */
545 get_page(netpage);
546 monitor->netfs_page = netpage;
547
548 get_page(backpage);
549 monitor->back_page = backpage;
550 monitor->monitor.private = backpage;
551 add_page_wait_queue(backpage, &monitor->monitor);
552 monitor = NULL;
553
554 /* but the page may have been read before the monitor was
555 * installed, so the monitor may miss the event - so we have to
556 * ensure that we do get one in such a case */
557 if (trylock_page(backpage)) {
558 _debug("2unlock %p {%lx}", backpage, backpage->flags);
559 unlock_page(backpage);
560 }
561
562 put_page(backpage);
563 backpage = NULL;
564
565 put_page(netpage);
566 netpage = NULL;
567 continue;
568
569 /* if the backing page is already present, it can be in one of
570 * three states: read in progress, read failed or read okay */
571 backing_page_already_present:
572 _debug("- present %p", backpage);
573
574 if (PageError(backpage))
575 goto io_error;
576
577 if (PageUptodate(backpage))
578 goto backing_page_already_uptodate;
579
580 _debug("- not ready %p{%lx}", backpage, backpage->flags);
581
582 if (!trylock_page(backpage))
583 goto monitor_backing_page;
584
585 if (PageError(backpage)) {
586 _debug("error %lx", backpage->flags);
587 unlock_page(backpage);
588 goto io_error;
589 }
590
591 if (PageUptodate(backpage))
592 goto backing_page_already_uptodate_unlock;
593
594 /* we've locked a page that's neither up to date nor erroneous,
595 * so we need to attempt to read it again */
596 goto reread_backing_page;
597
598 /* the backing page is already up to date, attach the netfs
599 * page to the pagecache and LRU and copy the data across */
600 backing_page_already_uptodate_unlock:
601 _debug("uptodate %lx", backpage->flags);
602 unlock_page(backpage);
603 backing_page_already_uptodate:
604 _debug("- uptodate");
605
606 ret = add_to_page_cache_lru(netpage, op->mapping,
607 netpage->index, cachefiles_gfp);
608 if (ret < 0) {
609 if (ret == -EEXIST) {
610 put_page(backpage);
611 backpage = NULL;
612 put_page(netpage);
613 netpage = NULL;
614 fscache_retrieval_complete(op, 1);
615 continue;
616 }
617 goto nomem;
618 }
619
620 copy_highpage(netpage, backpage);
621
622 put_page(backpage);
623 backpage = NULL;
624
625 fscache_mark_page_cached(op, netpage);
626
627 /* the netpage is unlocked and marked up to date here */
628 fscache_end_io(op, netpage, 0);
629 put_page(netpage);
630 netpage = NULL;
631 fscache_retrieval_complete(op, 1);
632 continue;
633 }
634
635 netpage = NULL;
636
637 _debug("out");
638
639out:
640 /* tidy up */
641 if (newpage)
642 put_page(newpage);
643 if (netpage)
644 put_page(netpage);
645 if (backpage)
646 put_page(backpage);
647 if (monitor) {
648 fscache_put_retrieval(op);
649 kfree(monitor);
650 }
651
652 list_for_each_entry_safe(netpage, _n, list, lru) {
653 list_del(&netpage->lru);
654 put_page(netpage);
655 fscache_retrieval_complete(op, 1);
656 }
657
658 _leave(" = %d", ret);
659 return ret;
660
661nomem:
662 _debug("nomem");
663 ret = -ENOMEM;
664 goto record_page_complete;
665
666read_error:
667 _debug("read error %d", ret);
668 if (ret == -ENOMEM)
669 goto record_page_complete;
670io_error:
671 cachefiles_io_error_obj(object, "Page read error on backing file");
672 ret = -ENOBUFS;
673record_page_complete:
674 fscache_retrieval_complete(op, 1);
675 goto out;
676}
677
678/*
679 * read a list of pages from the cache or allocate blocks in which to store
680 * them
681 */
682int cachefiles_read_or_alloc_pages(struct fscache_retrieval *op,
683 struct list_head *pages,
684 unsigned *nr_pages,
685 gfp_t gfp)
686{
687 struct cachefiles_object *object;
688 struct cachefiles_cache *cache;
689 struct list_head backpages;
690 struct pagevec pagevec;
691 struct inode *inode;
692 struct page *page, *_n;
693 unsigned shift, nrbackpages;
694 int ret, ret2, space;
695
696 object = container_of(op->op.object,
697 struct cachefiles_object, fscache);
698 cache = container_of(object->fscache.cache,
699 struct cachefiles_cache, cache);
700
701 _enter("{OBJ%x,%d},,%d,,",
702 object->fscache.debug_id, atomic_read(&op->op.usage),
703 *nr_pages);
704
705 if (!object->backer)
706 goto all_enobufs;
707
708 space = 1;
709 if (cachefiles_has_space(cache, 0, *nr_pages) < 0)
710 space = 0;
711
712 inode = d_backing_inode(object->backer);
713 ASSERT(S_ISREG(inode->i_mode));
714 ASSERT(inode->i_mapping->a_ops->bmap);
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 block0, 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 block0 = page->index;
740 block0 <<= shift;
741
742 block = inode->i_mapping->a_ops->bmap(inode->i_mapping,
743 block0);
744 _debug("%llx -> %llx",
745 (unsigned long long) block0,
746 (unsigned long long) block);
747
748 if (block) {
749 /* we have data - add it to the list to give to the
750 * backing fs */
751 list_move(&page->lru, &backpages);
752 (*nr_pages)--;
753 nrbackpages++;
754 } else if (space && pagevec_add(&pagevec, page) == 0) {
755 fscache_mark_pages_cached(op, &pagevec);
756 fscache_retrieval_complete(op, 1);
757 ret = -ENODATA;
758 } else {
759 fscache_retrieval_complete(op, 1);
760 }
761 }
762
763 if (pagevec_count(&pagevec) > 0)
764 fscache_mark_pages_cached(op, &pagevec);
765
766 if (list_empty(pages))
767 ret = 0;
768
769 /* submit the apparently valid pages to the backing fs to be read from
770 * disk */
771 if (nrbackpages > 0) {
772 ret2 = cachefiles_read_backing_file(object, op, &backpages);
773 if (ret2 == -ENOMEM || ret2 == -EINTR)
774 ret = ret2;
775 }
776
777 _leave(" = %d [nr=%u%s]",
778 ret, *nr_pages, list_empty(pages) ? " empty" : "");
779 return ret;
780
781all_enobufs:
782 fscache_retrieval_complete(op, *nr_pages);
783 return -ENOBUFS;
784}
785
786/*
787 * allocate a block in the cache in which to store a page
788 * - cache withdrawal is prevented by the caller
789 * - returns -EINTR if interrupted
790 * - returns -ENOMEM if ran out of memory
791 * - returns -ENOBUFS if no buffers can be made available
792 * - returns -ENOBUFS if page is beyond EOF
793 * - otherwise:
794 * - the metadata will be retained
795 * - 0 will be returned
796 */
797int cachefiles_allocate_page(struct fscache_retrieval *op,
798 struct page *page,
799 gfp_t gfp)
800{
801 struct cachefiles_object *object;
802 struct cachefiles_cache *cache;
803 int ret;
804
805 object = container_of(op->op.object,
806 struct cachefiles_object, fscache);
807 cache = container_of(object->fscache.cache,
808 struct cachefiles_cache, cache);
809
810 _enter("%p,{%lx},", object, page->index);
811
812 ret = cachefiles_has_space(cache, 0, 1);
813 if (ret == 0)
814 fscache_mark_page_cached(op, page);
815 else
816 ret = -ENOBUFS;
817
818 fscache_retrieval_complete(op, 1);
819 _leave(" = %d", ret);
820 return ret;
821}
822
823/*
824 * allocate blocks in the cache in which to store a set of pages
825 * - cache withdrawal is prevented by the caller
826 * - returns -EINTR if interrupted
827 * - returns -ENOMEM if ran out of memory
828 * - returns -ENOBUFS if some buffers couldn't be made available
829 * - returns -ENOBUFS if some pages are beyond EOF
830 * - otherwise:
831 * - -ENODATA will be returned
832 * - metadata will be retained for any page marked
833 */
834int cachefiles_allocate_pages(struct fscache_retrieval *op,
835 struct list_head *pages,
836 unsigned *nr_pages,
837 gfp_t gfp)
838{
839 struct cachefiles_object *object;
840 struct cachefiles_cache *cache;
841 struct pagevec pagevec;
842 struct page *page;
843 int ret;
844
845 object = container_of(op->op.object,
846 struct cachefiles_object, fscache);
847 cache = container_of(object->fscache.cache,
848 struct cachefiles_cache, cache);
849
850 _enter("%p,,,%d,", object, *nr_pages);
851
852 ret = cachefiles_has_space(cache, 0, *nr_pages);
853 if (ret == 0) {
854 pagevec_init(&pagevec);
855
856 list_for_each_entry(page, pages, lru) {
857 if (pagevec_add(&pagevec, page) == 0)
858 fscache_mark_pages_cached(op, &pagevec);
859 }
860
861 if (pagevec_count(&pagevec) > 0)
862 fscache_mark_pages_cached(op, &pagevec);
863 ret = -ENODATA;
864 } else {
865 ret = -ENOBUFS;
866 }
867
868 fscache_retrieval_complete(op, *nr_pages);
869 _leave(" = %d", ret);
870 return ret;
871}
872
873/*
874 * request a page be stored in the cache
875 * - cache withdrawal is prevented by the caller
876 * - this request may be ignored if there's no cache block available, in which
877 * case -ENOBUFS will be returned
878 * - if the op is in progress, 0 will be returned
879 */
880int cachefiles_write_page(struct fscache_storage *op, struct page *page)
881{
882 struct cachefiles_object *object;
883 struct cachefiles_cache *cache;
884 struct file *file;
885 struct path path;
886 loff_t pos, eof;
887 size_t len;
888 void *data;
889 int ret = -ENOBUFS;
890
891 ASSERT(op != NULL);
892 ASSERT(page != NULL);
893
894 object = container_of(op->op.object,
895 struct cachefiles_object, fscache);
896
897 _enter("%p,%p{%lx},,,", object, page, page->index);
898
899 if (!object->backer) {
900 _leave(" = -ENOBUFS");
901 return -ENOBUFS;
902 }
903
904 ASSERT(d_is_reg(object->backer));
905
906 cache = container_of(object->fscache.cache,
907 struct cachefiles_cache, cache);
908
909 pos = (loff_t)page->index << PAGE_SHIFT;
910
911 /* We mustn't write more data than we have, so we have to beware of a
912 * partial page at EOF.
913 */
914 eof = object->fscache.store_limit_l;
915 if (pos >= eof)
916 goto error;
917
918 /* write the page to the backing filesystem and let it store it in its
919 * own time */
920 path.mnt = cache->mnt;
921 path.dentry = object->backer;
922 file = dentry_open(&path, O_RDWR | O_LARGEFILE, cache->cache_cred);
923 if (IS_ERR(file)) {
924 ret = PTR_ERR(file);
925 goto error_2;
926 }
927
928 len = PAGE_SIZE;
929 if (eof & ~PAGE_MASK) {
930 if (eof - pos < PAGE_SIZE) {
931 _debug("cut short %llx to %llx",
932 pos, eof);
933 len = eof - pos;
934 ASSERTCMP(pos + len, ==, eof);
935 }
936 }
937
938 data = kmap(page);
939 ret = __kernel_write(file, data, len, &pos);
940 kunmap(page);
941 fput(file);
942 if (ret != len)
943 goto error_eio;
944
945 _leave(" = 0");
946 return 0;
947
948error_eio:
949 ret = -EIO;
950error_2:
951 if (ret == -EIO)
952 cachefiles_io_error_obj(object,
953 "Write page to backing file failed");
954error:
955 _leave(" = -ENOBUFS [%d]", ret);
956 return -ENOBUFS;
957}
958
959/*
960 * detach a backing block from a page
961 * - cache withdrawal is prevented by the caller
962 */
963void cachefiles_uncache_page(struct fscache_object *_object, struct page *page)
964 __releases(&object->fscache.cookie->lock)
965{
966 struct cachefiles_object *object;
967
968 object = container_of(_object, struct cachefiles_object, fscache);
969
970 _enter("%p,{%lu}", object, page->index);
971
972 spin_unlock(&object->fscache.cookie->lock);
973}