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1/* Storage object read/write
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 Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#include <linux/mount.h>
13#include <linux/slab.h>
14#include <linux/file.h>
15#include <linux/swap.h>
16#include "internal.h"
17
18/*
19 * detect wake up events generated by the unlocking of pages in which we're
20 * interested
21 * - we use this to detect read completion of backing pages
22 * - the caller holds the waitqueue lock
23 */
24static int cachefiles_read_waiter(wait_queue_entry_t *wait, unsigned mode,
25 int sync, void *_key)
26{
27 struct cachefiles_one_read *monitor =
28 container_of(wait, struct cachefiles_one_read, monitor);
29 struct cachefiles_object *object;
30 struct wait_bit_key *key = _key;
31 struct page *page = wait->private;
32
33 ASSERT(key);
34
35 _enter("{%lu},%u,%d,{%p,%u}",
36 monitor->netfs_page->index, mode, sync,
37 key->flags, key->bit_nr);
38
39 if (key->flags != &page->flags ||
40 key->bit_nr != PG_locked)
41 return 0;
42
43 _debug("--- monitor %p %lx ---", page, page->flags);
44
45 if (!PageUptodate(page) && !PageError(page)) {
46 /* unlocked, not uptodate and not erronous? */
47 _debug("page probably truncated");
48 }
49
50 /* remove from the waitqueue */
51 list_del(&wait->entry);
52
53 /* move onto the action list and queue for FS-Cache thread pool */
54 ASSERT(monitor->op);
55
56 object = container_of(monitor->op->op.object,
57 struct cachefiles_object, fscache);
58
59 spin_lock(&object->work_lock);
60 list_add_tail(&monitor->op_link, &monitor->op->to_do);
61 spin_unlock(&object->work_lock);
62
63 fscache_enqueue_retrieval(monitor->op);
64 return 0;
65}
66
67/*
68 * handle a probably truncated page
69 * - check to see if the page is still relevant and reissue the read if
70 * possible
71 * - return -EIO on error, -ENODATA if the page is gone, -EINPROGRESS if we
72 * must wait again and 0 if successful
73 */
74static int cachefiles_read_reissue(struct cachefiles_object *object,
75 struct cachefiles_one_read *monitor)
76{
77 struct address_space *bmapping = d_backing_inode(object->backer)->i_mapping;
78 struct page *backpage = monitor->back_page, *backpage2;
79 int ret;
80
81 _enter("{ino=%lx},{%lx,%lx}",
82 d_backing_inode(object->backer)->i_ino,
83 backpage->index, backpage->flags);
84
85 /* skip if the page was truncated away completely */
86 if (backpage->mapping != bmapping) {
87 _leave(" = -ENODATA [mapping]");
88 return -ENODATA;
89 }
90
91 backpage2 = find_get_page(bmapping, backpage->index);
92 if (!backpage2) {
93 _leave(" = -ENODATA [gone]");
94 return -ENODATA;
95 }
96
97 if (backpage != backpage2) {
98 put_page(backpage2);
99 _leave(" = -ENODATA [different]");
100 return -ENODATA;
101 }
102
103 /* the page is still there and we already have a ref on it, so we don't
104 * need a second */
105 put_page(backpage2);
106
107 INIT_LIST_HEAD(&monitor->op_link);
108 add_page_wait_queue(backpage, &monitor->monitor);
109
110 if (trylock_page(backpage)) {
111 ret = -EIO;
112 if (PageError(backpage))
113 goto unlock_discard;
114 ret = 0;
115 if (PageUptodate(backpage))
116 goto unlock_discard;
117
118 _debug("reissue read");
119 ret = bmapping->a_ops->readpage(NULL, backpage);
120 if (ret < 0)
121 goto unlock_discard;
122 }
123
124 /* but the page may have been read before the monitor was installed, so
125 * the monitor may miss the event - so we have to ensure that we do get
126 * one in such a case */
127 if (trylock_page(backpage)) {
128 _debug("jumpstart %p {%lx}", backpage, backpage->flags);
129 unlock_page(backpage);
130 }
131
132 /* it'll reappear on the todo list */
133 _leave(" = -EINPROGRESS");
134 return -EINPROGRESS;
135
136unlock_discard:
137 unlock_page(backpage);
138 spin_lock_irq(&object->work_lock);
139 list_del(&monitor->op_link);
140 spin_unlock_irq(&object->work_lock);
141 _leave(" = %d", ret);
142 return ret;
143}
144
145/*
146 * copy data from backing pages to netfs pages to complete a read operation
147 * - driven by FS-Cache's thread pool
148 */
149static void cachefiles_read_copier(struct fscache_operation *_op)
150{
151 struct cachefiles_one_read *monitor;
152 struct cachefiles_object *object;
153 struct fscache_retrieval *op;
154 int error, max;
155
156 op = container_of(_op, struct fscache_retrieval, op);
157 object = container_of(op->op.object,
158 struct cachefiles_object, fscache);
159
160 _enter("{ino=%lu}", d_backing_inode(object->backer)->i_ino);
161
162 max = 8;
163 spin_lock_irq(&object->work_lock);
164
165 while (!list_empty(&op->to_do)) {
166 monitor = list_entry(op->to_do.next,
167 struct cachefiles_one_read, op_link);
168 list_del(&monitor->op_link);
169
170 spin_unlock_irq(&object->work_lock);
171
172 _debug("- copy {%lu}", monitor->back_page->index);
173
174 recheck:
175 if (test_bit(FSCACHE_COOKIE_INVALIDATING,
176 &object->fscache.cookie->flags)) {
177 error = -ESTALE;
178 } else if (PageUptodate(monitor->back_page)) {
179 copy_highpage(monitor->netfs_page, monitor->back_page);
180 fscache_mark_page_cached(monitor->op,
181 monitor->netfs_page);
182 error = 0;
183 } else if (!PageError(monitor->back_page)) {
184 /* the page has probably been truncated */
185 error = cachefiles_read_reissue(object, monitor);
186 if (error == -EINPROGRESS)
187 goto next;
188 goto recheck;
189 } else {
190 cachefiles_io_error_obj(
191 object,
192 "Readpage failed on backing file %lx",
193 (unsigned long) monitor->back_page->flags);
194 error = -EIO;
195 }
196
197 put_page(monitor->back_page);
198
199 fscache_end_io(op, monitor->netfs_page, error);
200 put_page(monitor->netfs_page);
201 fscache_retrieval_complete(op, 1);
202 fscache_put_retrieval(op);
203 kfree(monitor);
204
205 next:
206 /* let the thread pool have some air occasionally */
207 max--;
208 if (max < 0 || need_resched()) {
209 if (!list_empty(&op->to_do))
210 fscache_enqueue_retrieval(op);
211 _leave(" [maxed out]");
212 return;
213 }
214
215 spin_lock_irq(&object->work_lock);
216 }
217
218 spin_unlock_irq(&object->work_lock);
219 _leave("");
220}
221
222/*
223 * read the corresponding page to the given set from the backing file
224 * - an uncertain page is simply discarded, to be tried again another time
225 */
226static int cachefiles_read_backing_file_one(struct cachefiles_object *object,
227 struct fscache_retrieval *op,
228 struct page *netpage)
229{
230 struct cachefiles_one_read *monitor;
231 struct address_space *bmapping;
232 struct page *newpage, *backpage;
233 int ret;
234
235 _enter("");
236
237 _debug("read back %p{%lu,%d}",
238 netpage, netpage->index, page_count(netpage));
239
240 monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
241 if (!monitor)
242 goto nomem;
243
244 monitor->netfs_page = netpage;
245 monitor->op = fscache_get_retrieval(op);
246
247 init_waitqueue_func_entry(&monitor->monitor, cachefiles_read_waiter);
248
249 /* attempt to get hold of the backing page */
250 bmapping = d_backing_inode(object->backer)->i_mapping;
251 newpage = NULL;
252
253 for (;;) {
254 backpage = find_get_page(bmapping, netpage->index);
255 if (backpage)
256 goto backing_page_already_present;
257
258 if (!newpage) {
259 newpage = __page_cache_alloc(cachefiles_gfp);
260 if (!newpage)
261 goto nomem_monitor;
262 }
263
264 ret = add_to_page_cache_lru(newpage, bmapping,
265 netpage->index, cachefiles_gfp);
266 if (ret == 0)
267 goto installed_new_backing_page;
268 if (ret != -EEXIST)
269 goto nomem_page;
270 }
271
272 /* we've installed a new backing page, so now we need to start
273 * it reading */
274installed_new_backing_page:
275 _debug("- new %p", newpage);
276
277 backpage = newpage;
278 newpage = NULL;
279
280read_backing_page:
281 ret = bmapping->a_ops->readpage(NULL, backpage);
282 if (ret < 0)
283 goto read_error;
284
285 /* set the monitor to transfer the data across */
286monitor_backing_page:
287 _debug("- monitor add");
288
289 /* install the monitor */
290 get_page(monitor->netfs_page);
291 get_page(backpage);
292 monitor->back_page = backpage;
293 monitor->monitor.private = backpage;
294 add_page_wait_queue(backpage, &monitor->monitor);
295 monitor = NULL;
296
297 /* but the page may have been read before the monitor was installed, so
298 * the monitor may miss the event - so we have to ensure that we do get
299 * one in such a case */
300 if (trylock_page(backpage)) {
301 _debug("jumpstart %p {%lx}", backpage, backpage->flags);
302 unlock_page(backpage);
303 }
304 goto success;
305
306 /* if the backing page is already present, it can be in one of
307 * three states: read in progress, read failed or read okay */
308backing_page_already_present:
309 _debug("- present");
310
311 if (newpage) {
312 put_page(newpage);
313 newpage = NULL;
314 }
315
316 if (PageError(backpage))
317 goto io_error;
318
319 if (PageUptodate(backpage))
320 goto backing_page_already_uptodate;
321
322 if (!trylock_page(backpage))
323 goto monitor_backing_page;
324 _debug("read %p {%lx}", backpage, backpage->flags);
325 goto read_backing_page;
326
327 /* the backing page is already up to date, attach the netfs
328 * page to the pagecache and LRU and copy the data across */
329backing_page_already_uptodate:
330 _debug("- uptodate");
331
332 fscache_mark_page_cached(op, netpage);
333
334 copy_highpage(netpage, backpage);
335 fscache_end_io(op, netpage, 0);
336 fscache_retrieval_complete(op, 1);
337
338success:
339 _debug("success");
340 ret = 0;
341
342out:
343 if (backpage)
344 put_page(backpage);
345 if (monitor) {
346 fscache_put_retrieval(monitor->op);
347 kfree(monitor);
348 }
349 _leave(" = %d", ret);
350 return ret;
351
352read_error:
353 _debug("read error %d", ret);
354 if (ret == -ENOMEM) {
355 fscache_retrieval_complete(op, 1);
356 goto out;
357 }
358io_error:
359 cachefiles_io_error_obj(object, "Page read error on backing file");
360 fscache_retrieval_complete(op, 1);
361 ret = -ENOBUFS;
362 goto out;
363
364nomem_page:
365 put_page(newpage);
366nomem_monitor:
367 fscache_put_retrieval(monitor->op);
368 kfree(monitor);
369nomem:
370 fscache_retrieval_complete(op, 1);
371 _leave(" = -ENOMEM");
372 return -ENOMEM;
373}
374
375/*
376 * read a page from the cache or allocate a block in which to store it
377 * - cache withdrawal is prevented by the caller
378 * - returns -EINTR if interrupted
379 * - returns -ENOMEM if ran out of memory
380 * - returns -ENOBUFS if no buffers can be made available
381 * - returns -ENOBUFS if page is beyond EOF
382 * - if the page is backed by a block in the cache:
383 * - a read will be started which will call the callback on completion
384 * - 0 will be returned
385 * - else if the page is unbacked:
386 * - the metadata will be retained
387 * - -ENODATA will be returned
388 */
389int cachefiles_read_or_alloc_page(struct fscache_retrieval *op,
390 struct page *page,
391 gfp_t gfp)
392{
393 struct cachefiles_object *object;
394 struct cachefiles_cache *cache;
395 struct inode *inode;
396 sector_t block0, block;
397 unsigned shift;
398 int ret;
399
400 object = container_of(op->op.object,
401 struct cachefiles_object, fscache);
402 cache = container_of(object->fscache.cache,
403 struct cachefiles_cache, cache);
404
405 _enter("{%p},{%lx},,,", object, page->index);
406
407 if (!object->backer)
408 goto enobufs;
409
410 inode = d_backing_inode(object->backer);
411 ASSERT(S_ISREG(inode->i_mode));
412 ASSERT(inode->i_mapping->a_ops->bmap);
413 ASSERT(inode->i_mapping->a_ops->readpages);
414
415 /* calculate the shift required to use bmap */
416 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
417
418 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
419 op->op.flags |= FSCACHE_OP_ASYNC;
420 op->op.processor = cachefiles_read_copier;
421
422 /* we assume the absence or presence of the first block is a good
423 * enough indication for the page as a whole
424 * - TODO: don't use bmap() for this as it is _not_ actually good
425 * enough for this as it doesn't indicate errors, but it's all we've
426 * got for the moment
427 */
428 block0 = page->index;
429 block0 <<= shift;
430
431 block = inode->i_mapping->a_ops->bmap(inode->i_mapping, block0);
432 _debug("%llx -> %llx",
433 (unsigned long long) block0,
434 (unsigned long long) block);
435
436 if (block) {
437 /* submit the apparently valid page to the backing fs to be
438 * read from disk */
439 ret = cachefiles_read_backing_file_one(object, op, page);
440 } else if (cachefiles_has_space(cache, 0, 1) == 0) {
441 /* there's space in the cache we can use */
442 fscache_mark_page_cached(op, page);
443 fscache_retrieval_complete(op, 1);
444 ret = -ENODATA;
445 } else {
446 goto enobufs;
447 }
448
449 _leave(" = %d", ret);
450 return ret;
451
452enobufs:
453 fscache_retrieval_complete(op, 1);
454 _leave(" = -ENOBUFS");
455 return -ENOBUFS;
456}
457
458/*
459 * read the corresponding pages to the given set from the backing file
460 * - any uncertain pages are simply discarded, to be tried again another time
461 */
462static int cachefiles_read_backing_file(struct cachefiles_object *object,
463 struct fscache_retrieval *op,
464 struct list_head *list)
465{
466 struct cachefiles_one_read *monitor = NULL;
467 struct address_space *bmapping = d_backing_inode(object->backer)->i_mapping;
468 struct page *newpage = NULL, *netpage, *_n, *backpage = NULL;
469 int ret = 0;
470
471 _enter("");
472
473 list_for_each_entry_safe(netpage, _n, list, lru) {
474 list_del(&netpage->lru);
475
476 _debug("read back %p{%lu,%d}",
477 netpage, netpage->index, page_count(netpage));
478
479 if (!monitor) {
480 monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
481 if (!monitor)
482 goto nomem;
483
484 monitor->op = fscache_get_retrieval(op);
485 init_waitqueue_func_entry(&monitor->monitor,
486 cachefiles_read_waiter);
487 }
488
489 for (;;) {
490 backpage = find_get_page(bmapping, netpage->index);
491 if (backpage)
492 goto backing_page_already_present;
493
494 if (!newpage) {
495 newpage = __page_cache_alloc(cachefiles_gfp);
496 if (!newpage)
497 goto nomem;
498 }
499
500 ret = add_to_page_cache_lru(newpage, bmapping,
501 netpage->index,
502 cachefiles_gfp);
503 if (ret == 0)
504 goto installed_new_backing_page;
505 if (ret != -EEXIST)
506 goto nomem;
507 }
508
509 /* we've installed a new backing page, so now we need
510 * to start it reading */
511 installed_new_backing_page:
512 _debug("- new %p", newpage);
513
514 backpage = newpage;
515 newpage = NULL;
516
517 reread_backing_page:
518 ret = bmapping->a_ops->readpage(NULL, backpage);
519 if (ret < 0)
520 goto read_error;
521
522 /* add the netfs page to the pagecache and LRU, and set the
523 * monitor to transfer the data across */
524 monitor_backing_page:
525 _debug("- monitor add");
526
527 ret = add_to_page_cache_lru(netpage, op->mapping,
528 netpage->index, cachefiles_gfp);
529 if (ret < 0) {
530 if (ret == -EEXIST) {
531 put_page(netpage);
532 fscache_retrieval_complete(op, 1);
533 continue;
534 }
535 goto nomem;
536 }
537
538 /* install a monitor */
539 get_page(netpage);
540 monitor->netfs_page = netpage;
541
542 get_page(backpage);
543 monitor->back_page = backpage;
544 monitor->monitor.private = backpage;
545 add_page_wait_queue(backpage, &monitor->monitor);
546 monitor = NULL;
547
548 /* but the page may have been read before the monitor was
549 * installed, so the monitor may miss the event - so we have to
550 * ensure that we do get one in such a case */
551 if (trylock_page(backpage)) {
552 _debug("2unlock %p {%lx}", backpage, backpage->flags);
553 unlock_page(backpage);
554 }
555
556 put_page(backpage);
557 backpage = NULL;
558
559 put_page(netpage);
560 netpage = NULL;
561 continue;
562
563 /* if the backing page is already present, it can be in one of
564 * three states: read in progress, read failed or read okay */
565 backing_page_already_present:
566 _debug("- present %p", backpage);
567
568 if (PageError(backpage))
569 goto io_error;
570
571 if (PageUptodate(backpage))
572 goto backing_page_already_uptodate;
573
574 _debug("- not ready %p{%lx}", backpage, backpage->flags);
575
576 if (!trylock_page(backpage))
577 goto monitor_backing_page;
578
579 if (PageError(backpage)) {
580 _debug("error %lx", backpage->flags);
581 unlock_page(backpage);
582 goto io_error;
583 }
584
585 if (PageUptodate(backpage))
586 goto backing_page_already_uptodate_unlock;
587
588 /* we've locked a page that's neither up to date nor erroneous,
589 * so we need to attempt to read it again */
590 goto reread_backing_page;
591
592 /* the backing page is already up to date, attach the netfs
593 * page to the pagecache and LRU and copy the data across */
594 backing_page_already_uptodate_unlock:
595 _debug("uptodate %lx", backpage->flags);
596 unlock_page(backpage);
597 backing_page_already_uptodate:
598 _debug("- uptodate");
599
600 ret = add_to_page_cache_lru(netpage, op->mapping,
601 netpage->index, cachefiles_gfp);
602 if (ret < 0) {
603 if (ret == -EEXIST) {
604 put_page(netpage);
605 fscache_retrieval_complete(op, 1);
606 continue;
607 }
608 goto nomem;
609 }
610
611 copy_highpage(netpage, backpage);
612
613 put_page(backpage);
614 backpage = NULL;
615
616 fscache_mark_page_cached(op, netpage);
617
618 /* the netpage is unlocked and marked up to date here */
619 fscache_end_io(op, netpage, 0);
620 put_page(netpage);
621 netpage = NULL;
622 fscache_retrieval_complete(op, 1);
623 continue;
624 }
625
626 netpage = NULL;
627
628 _debug("out");
629
630out:
631 /* tidy up */
632 if (newpage)
633 put_page(newpage);
634 if (netpage)
635 put_page(netpage);
636 if (backpage)
637 put_page(backpage);
638 if (monitor) {
639 fscache_put_retrieval(op);
640 kfree(monitor);
641 }
642
643 list_for_each_entry_safe(netpage, _n, list, lru) {
644 list_del(&netpage->lru);
645 put_page(netpage);
646 fscache_retrieval_complete(op, 1);
647 }
648
649 _leave(" = %d", ret);
650 return ret;
651
652nomem:
653 _debug("nomem");
654 ret = -ENOMEM;
655 goto record_page_complete;
656
657read_error:
658 _debug("read error %d", ret);
659 if (ret == -ENOMEM)
660 goto record_page_complete;
661io_error:
662 cachefiles_io_error_obj(object, "Page read error on backing file");
663 ret = -ENOBUFS;
664record_page_complete:
665 fscache_retrieval_complete(op, 1);
666 goto out;
667}
668
669/*
670 * read a list of pages from the cache or allocate blocks in which to store
671 * them
672 */
673int cachefiles_read_or_alloc_pages(struct fscache_retrieval *op,
674 struct list_head *pages,
675 unsigned *nr_pages,
676 gfp_t gfp)
677{
678 struct cachefiles_object *object;
679 struct cachefiles_cache *cache;
680 struct list_head backpages;
681 struct pagevec pagevec;
682 struct inode *inode;
683 struct page *page, *_n;
684 unsigned shift, nrbackpages;
685 int ret, ret2, space;
686
687 object = container_of(op->op.object,
688 struct cachefiles_object, fscache);
689 cache = container_of(object->fscache.cache,
690 struct cachefiles_cache, cache);
691
692 _enter("{OBJ%x,%d},,%d,,",
693 object->fscache.debug_id, atomic_read(&op->op.usage),
694 *nr_pages);
695
696 if (!object->backer)
697 goto all_enobufs;
698
699 space = 1;
700 if (cachefiles_has_space(cache, 0, *nr_pages) < 0)
701 space = 0;
702
703 inode = d_backing_inode(object->backer);
704 ASSERT(S_ISREG(inode->i_mode));
705 ASSERT(inode->i_mapping->a_ops->bmap);
706 ASSERT(inode->i_mapping->a_ops->readpages);
707
708 /* calculate the shift required to use bmap */
709 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
710
711 pagevec_init(&pagevec);
712
713 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
714 op->op.flags |= FSCACHE_OP_ASYNC;
715 op->op.processor = cachefiles_read_copier;
716
717 INIT_LIST_HEAD(&backpages);
718 nrbackpages = 0;
719
720 ret = space ? -ENODATA : -ENOBUFS;
721 list_for_each_entry_safe(page, _n, pages, lru) {
722 sector_t block0, block;
723
724 /* we assume the absence or presence of the first block is a
725 * good enough indication for the page as a whole
726 * - TODO: don't use bmap() for this as it is _not_ actually
727 * good enough for this as it doesn't indicate errors, but
728 * it's all we've got for the moment
729 */
730 block0 = page->index;
731 block0 <<= shift;
732
733 block = inode->i_mapping->a_ops->bmap(inode->i_mapping,
734 block0);
735 _debug("%llx -> %llx",
736 (unsigned long long) block0,
737 (unsigned long long) block);
738
739 if (block) {
740 /* we have data - add it to the list to give to the
741 * backing fs */
742 list_move(&page->lru, &backpages);
743 (*nr_pages)--;
744 nrbackpages++;
745 } else if (space && pagevec_add(&pagevec, page) == 0) {
746 fscache_mark_pages_cached(op, &pagevec);
747 fscache_retrieval_complete(op, 1);
748 ret = -ENODATA;
749 } else {
750 fscache_retrieval_complete(op, 1);
751 }
752 }
753
754 if (pagevec_count(&pagevec) > 0)
755 fscache_mark_pages_cached(op, &pagevec);
756
757 if (list_empty(pages))
758 ret = 0;
759
760 /* submit the apparently valid pages to the backing fs to be read from
761 * disk */
762 if (nrbackpages > 0) {
763 ret2 = cachefiles_read_backing_file(object, op, &backpages);
764 if (ret2 == -ENOMEM || ret2 == -EINTR)
765 ret = ret2;
766 }
767
768 _leave(" = %d [nr=%u%s]",
769 ret, *nr_pages, list_empty(pages) ? " empty" : "");
770 return ret;
771
772all_enobufs:
773 fscache_retrieval_complete(op, *nr_pages);
774 return -ENOBUFS;
775}
776
777/*
778 * allocate a block in the cache in which to store a page
779 * - cache withdrawal is prevented by the caller
780 * - returns -EINTR if interrupted
781 * - returns -ENOMEM if ran out of memory
782 * - returns -ENOBUFS if no buffers can be made available
783 * - returns -ENOBUFS if page is beyond EOF
784 * - otherwise:
785 * - the metadata will be retained
786 * - 0 will be returned
787 */
788int cachefiles_allocate_page(struct fscache_retrieval *op,
789 struct page *page,
790 gfp_t gfp)
791{
792 struct cachefiles_object *object;
793 struct cachefiles_cache *cache;
794 int ret;
795
796 object = container_of(op->op.object,
797 struct cachefiles_object, fscache);
798 cache = container_of(object->fscache.cache,
799 struct cachefiles_cache, cache);
800
801 _enter("%p,{%lx},", object, page->index);
802
803 ret = cachefiles_has_space(cache, 0, 1);
804 if (ret == 0)
805 fscache_mark_page_cached(op, page);
806 else
807 ret = -ENOBUFS;
808
809 fscache_retrieval_complete(op, 1);
810 _leave(" = %d", ret);
811 return ret;
812}
813
814/*
815 * allocate blocks in the cache in which to store a set of pages
816 * - cache withdrawal is prevented by the caller
817 * - returns -EINTR if interrupted
818 * - returns -ENOMEM if ran out of memory
819 * - returns -ENOBUFS if some buffers couldn't be made available
820 * - returns -ENOBUFS if some pages are beyond EOF
821 * - otherwise:
822 * - -ENODATA will be returned
823 * - metadata will be retained for any page marked
824 */
825int cachefiles_allocate_pages(struct fscache_retrieval *op,
826 struct list_head *pages,
827 unsigned *nr_pages,
828 gfp_t gfp)
829{
830 struct cachefiles_object *object;
831 struct cachefiles_cache *cache;
832 struct pagevec pagevec;
833 struct page *page;
834 int ret;
835
836 object = container_of(op->op.object,
837 struct cachefiles_object, fscache);
838 cache = container_of(object->fscache.cache,
839 struct cachefiles_cache, cache);
840
841 _enter("%p,,,%d,", object, *nr_pages);
842
843 ret = cachefiles_has_space(cache, 0, *nr_pages);
844 if (ret == 0) {
845 pagevec_init(&pagevec);
846
847 list_for_each_entry(page, pages, lru) {
848 if (pagevec_add(&pagevec, page) == 0)
849 fscache_mark_pages_cached(op, &pagevec);
850 }
851
852 if (pagevec_count(&pagevec) > 0)
853 fscache_mark_pages_cached(op, &pagevec);
854 ret = -ENODATA;
855 } else {
856 ret = -ENOBUFS;
857 }
858
859 fscache_retrieval_complete(op, *nr_pages);
860 _leave(" = %d", ret);
861 return ret;
862}
863
864/*
865 * request a page be stored in the cache
866 * - cache withdrawal is prevented by the caller
867 * - this request may be ignored if there's no cache block available, in which
868 * case -ENOBUFS will be returned
869 * - if the op is in progress, 0 will be returned
870 */
871int cachefiles_write_page(struct fscache_storage *op, struct page *page)
872{
873 struct cachefiles_object *object;
874 struct cachefiles_cache *cache;
875 struct file *file;
876 struct path path;
877 loff_t pos, eof;
878 size_t len;
879 void *data;
880 int ret = -ENOBUFS;
881
882 ASSERT(op != NULL);
883 ASSERT(page != NULL);
884
885 object = container_of(op->op.object,
886 struct cachefiles_object, fscache);
887
888 _enter("%p,%p{%lx},,,", object, page, page->index);
889
890 if (!object->backer) {
891 _leave(" = -ENOBUFS");
892 return -ENOBUFS;
893 }
894
895 ASSERT(d_is_reg(object->backer));
896
897 cache = container_of(object->fscache.cache,
898 struct cachefiles_cache, cache);
899
900 pos = (loff_t)page->index << PAGE_SHIFT;
901
902 /* We mustn't write more data than we have, so we have to beware of a
903 * partial page at EOF.
904 */
905 eof = object->fscache.store_limit_l;
906 if (pos >= eof)
907 goto error;
908
909 /* write the page to the backing filesystem and let it store it in its
910 * own time */
911 path.mnt = cache->mnt;
912 path.dentry = object->backer;
913 file = dentry_open(&path, O_RDWR | O_LARGEFILE, cache->cache_cred);
914 if (IS_ERR(file)) {
915 ret = PTR_ERR(file);
916 goto error_2;
917 }
918
919 len = PAGE_SIZE;
920 if (eof & ~PAGE_MASK) {
921 if (eof - pos < PAGE_SIZE) {
922 _debug("cut short %llx to %llx",
923 pos, eof);
924 len = eof - pos;
925 ASSERTCMP(pos + len, ==, eof);
926 }
927 }
928
929 data = kmap(page);
930 ret = __kernel_write(file, data, len, &pos);
931 kunmap(page);
932 fput(file);
933 if (ret != len)
934 goto error_eio;
935
936 _leave(" = 0");
937 return 0;
938
939error_eio:
940 ret = -EIO;
941error_2:
942 if (ret == -EIO)
943 cachefiles_io_error_obj(object,
944 "Write page to backing file failed");
945error:
946 _leave(" = -ENOBUFS [%d]", ret);
947 return -ENOBUFS;
948}
949
950/*
951 * detach a backing block from a page
952 * - cache withdrawal is prevented by the caller
953 */
954void cachefiles_uncache_page(struct fscache_object *_object, struct page *page)
955 __releases(&object->fscache.cookie->lock)
956{
957 struct cachefiles_object *object;
958 struct cachefiles_cache *cache;
959
960 object = container_of(_object, struct cachefiles_object, fscache);
961 cache = container_of(object->fscache.cache,
962 struct cachefiles_cache, cache);
963
964 _enter("%p,{%lu}", object, page->index);
965
966 spin_unlock(&object->fscache.cookie->lock);
967}