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 */
cachefiles_read_waiter(wait_queue_entry_t * wait,unsigned mode,int sync,void * _key)20 static 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 */
cachefiles_read_reissue(struct cachefiles_object * object,struct cachefiles_one_read * monitor)77 static 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 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
139 unlock_discard:
140 unlock_page(backpage);
141 discard:
142 spin_lock_irq(&object->work_lock);
143 list_del(&monitor->op_link);
144 spin_unlock_irq(&object->work_lock);
145 _leave(" = %d", ret);
146 return ret;
147 }
148
149 /*
150 * copy data from backing pages to netfs pages to complete a read operation
151 * - driven by FS-Cache's thread pool
152 */
cachefiles_read_copier(struct fscache_operation * _op)153 static void cachefiles_read_copier(struct fscache_operation *_op)
154 {
155 struct cachefiles_one_read *monitor;
156 struct cachefiles_object *object;
157 struct fscache_retrieval *op;
158 int error, max;
159
160 op = container_of(_op, struct fscache_retrieval, op);
161 object = container_of(op->op.object,
162 struct cachefiles_object, fscache);
163
164 _enter("{ino=%lu}", d_backing_inode(object->backer)->i_ino);
165
166 max = 8;
167 spin_lock_irq(&object->work_lock);
168
169 while (!list_empty(&op->to_do)) {
170 monitor = list_entry(op->to_do.next,
171 struct cachefiles_one_read, op_link);
172 list_del(&monitor->op_link);
173
174 spin_unlock_irq(&object->work_lock);
175
176 _debug("- copy {%lu}", monitor->back_page->index);
177
178 recheck:
179 if (test_bit(FSCACHE_COOKIE_INVALIDATING,
180 &object->fscache.cookie->flags)) {
181 error = -ESTALE;
182 } else if (PageUptodate(monitor->back_page)) {
183 copy_highpage(monitor->netfs_page, monitor->back_page);
184 fscache_mark_page_cached(monitor->op,
185 monitor->netfs_page);
186 error = 0;
187 } else if (!PageError(monitor->back_page)) {
188 /* the page has probably been truncated */
189 error = cachefiles_read_reissue(object, monitor);
190 if (error == -EINPROGRESS)
191 goto next;
192 goto recheck;
193 } else {
194 cachefiles_io_error_obj(
195 object,
196 "Readpage failed on backing file %lx",
197 (unsigned long) monitor->back_page->flags);
198 error = -EIO;
199 }
200
201 put_page(monitor->back_page);
202
203 fscache_end_io(op, monitor->netfs_page, error);
204 put_page(monitor->netfs_page);
205 fscache_retrieval_complete(op, 1);
206 fscache_put_retrieval(op);
207 kfree(monitor);
208
209 next:
210 /* let the thread pool have some air occasionally */
211 max--;
212 if (max < 0 || need_resched()) {
213 if (!list_empty(&op->to_do))
214 fscache_enqueue_retrieval(op);
215 _leave(" [maxed out]");
216 return;
217 }
218
219 spin_lock_irq(&object->work_lock);
220 }
221
222 spin_unlock_irq(&object->work_lock);
223 _leave("");
224 }
225
226 /*
227 * read the corresponding page to the given set from the backing file
228 * - an uncertain page is simply discarded, to be tried again another time
229 */
cachefiles_read_backing_file_one(struct cachefiles_object * object,struct fscache_retrieval * op,struct page * netpage)230 static int cachefiles_read_backing_file_one(struct cachefiles_object *object,
231 struct fscache_retrieval *op,
232 struct page *netpage)
233 {
234 struct cachefiles_one_read *monitor;
235 struct address_space *bmapping;
236 struct page *newpage, *backpage;
237 int ret;
238
239 _enter("");
240
241 _debug("read back %p{%lu,%d}",
242 netpage, netpage->index, page_count(netpage));
243
244 monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
245 if (!monitor)
246 goto nomem;
247
248 monitor->netfs_page = netpage;
249 monitor->op = fscache_get_retrieval(op);
250
251 init_waitqueue_func_entry(&monitor->monitor, cachefiles_read_waiter);
252
253 /* attempt to get hold of the backing page */
254 bmapping = d_backing_inode(object->backer)->i_mapping;
255 newpage = NULL;
256
257 for (;;) {
258 backpage = find_get_page(bmapping, netpage->index);
259 if (backpage)
260 goto backing_page_already_present;
261
262 if (!newpage) {
263 newpage = __page_cache_alloc(cachefiles_gfp);
264 if (!newpage)
265 goto nomem_monitor;
266 }
267
268 ret = add_to_page_cache_lru(newpage, bmapping,
269 netpage->index, cachefiles_gfp);
270 if (ret == 0)
271 goto installed_new_backing_page;
272 if (ret != -EEXIST)
273 goto nomem_page;
274 }
275
276 /* we've installed a new backing page, so now we need to start
277 * it reading */
278 installed_new_backing_page:
279 _debug("- new %p", newpage);
280
281 backpage = newpage;
282 newpage = NULL;
283
284 read_backing_page:
285 ret = bmapping->a_ops->readpage(NULL, backpage);
286 if (ret < 0)
287 goto read_error;
288
289 /* set the monitor to transfer the data across */
290 monitor_backing_page:
291 _debug("- monitor add");
292
293 /* install the monitor */
294 get_page(monitor->netfs_page);
295 get_page(backpage);
296 monitor->back_page = backpage;
297 monitor->monitor.private = backpage;
298 add_page_wait_queue(backpage, &monitor->monitor);
299 monitor = NULL;
300
301 /* but the page may have been read before the monitor was installed, so
302 * the monitor may miss the event - so we have to ensure that we do get
303 * one in such a case */
304 if (trylock_page(backpage)) {
305 _debug("jumpstart %p {%lx}", backpage, backpage->flags);
306 unlock_page(backpage);
307 }
308 goto success;
309
310 /* if the backing page is already present, it can be in one of
311 * three states: read in progress, read failed or read okay */
312 backing_page_already_present:
313 _debug("- present");
314
315 if (newpage) {
316 put_page(newpage);
317 newpage = NULL;
318 }
319
320 if (PageError(backpage))
321 goto io_error;
322
323 if (PageUptodate(backpage))
324 goto backing_page_already_uptodate;
325
326 if (!trylock_page(backpage))
327 goto monitor_backing_page;
328 _debug("read %p {%lx}", backpage, backpage->flags);
329 goto read_backing_page;
330
331 /* the backing page is already up to date, attach the netfs
332 * page to the pagecache and LRU and copy the data across */
333 backing_page_already_uptodate:
334 _debug("- uptodate");
335
336 fscache_mark_page_cached(op, netpage);
337
338 copy_highpage(netpage, backpage);
339 fscache_end_io(op, netpage, 0);
340 fscache_retrieval_complete(op, 1);
341
342 success:
343 _debug("success");
344 ret = 0;
345
346 out:
347 if (backpage)
348 put_page(backpage);
349 if (monitor) {
350 fscache_put_retrieval(monitor->op);
351 kfree(monitor);
352 }
353 _leave(" = %d", ret);
354 return ret;
355
356 read_error:
357 _debug("read error %d", ret);
358 if (ret == -ENOMEM) {
359 fscache_retrieval_complete(op, 1);
360 goto out;
361 }
362 io_error:
363 cachefiles_io_error_obj(object, "Page read error on backing file");
364 fscache_retrieval_complete(op, 1);
365 ret = -ENOBUFS;
366 goto out;
367
368 nomem_page:
369 put_page(newpage);
370 nomem_monitor:
371 fscache_put_retrieval(monitor->op);
372 kfree(monitor);
373 nomem:
374 fscache_retrieval_complete(op, 1);
375 _leave(" = -ENOMEM");
376 return -ENOMEM;
377 }
378
379 /*
380 * read a page from the cache or allocate a block in which to store it
381 * - cache withdrawal is prevented by the caller
382 * - returns -EINTR if interrupted
383 * - returns -ENOMEM if ran out of memory
384 * - returns -ENOBUFS if no buffers can be made available
385 * - returns -ENOBUFS if page is beyond EOF
386 * - if the page is backed by a block in the cache:
387 * - a read will be started which will call the callback on completion
388 * - 0 will be returned
389 * - else if the page is unbacked:
390 * - the metadata will be retained
391 * - -ENODATA will be returned
392 */
cachefiles_read_or_alloc_page(struct fscache_retrieval * op,struct page * page,gfp_t gfp)393 int cachefiles_read_or_alloc_page(struct fscache_retrieval *op,
394 struct page *page,
395 gfp_t gfp)
396 {
397 struct cachefiles_object *object;
398 struct cachefiles_cache *cache;
399 struct inode *inode;
400 sector_t block0, block;
401 unsigned shift;
402 int ret;
403
404 object = container_of(op->op.object,
405 struct cachefiles_object, fscache);
406 cache = container_of(object->fscache.cache,
407 struct cachefiles_cache, cache);
408
409 _enter("{%p},{%lx},,,", object, page->index);
410
411 if (!object->backer)
412 goto enobufs;
413
414 inode = d_backing_inode(object->backer);
415 ASSERT(S_ISREG(inode->i_mode));
416 ASSERT(inode->i_mapping->a_ops->bmap);
417 ASSERT(inode->i_mapping->a_ops->readpages);
418
419 /* calculate the shift required to use bmap */
420 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
421
422 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
423 op->op.flags |= FSCACHE_OP_ASYNC;
424 op->op.processor = cachefiles_read_copier;
425
426 /* we assume the absence or presence of the first block is a good
427 * enough indication for the page as a whole
428 * - TODO: don't use bmap() for this as it is _not_ actually good
429 * enough for this as it doesn't indicate errors, but it's all we've
430 * got for the moment
431 */
432 block0 = page->index;
433 block0 <<= shift;
434
435 block = inode->i_mapping->a_ops->bmap(inode->i_mapping, block0);
436 _debug("%llx -> %llx",
437 (unsigned long long) block0,
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
456 enobufs:
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 */
cachefiles_read_backing_file(struct cachefiles_object * object,struct fscache_retrieval * op,struct list_head * list)466 static 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
640 out:
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
662 nomem:
663 _debug("nomem");
664 ret = -ENOMEM;
665 goto record_page_complete;
666
667 read_error:
668 _debug("read error %d", ret);
669 if (ret == -ENOMEM)
670 goto record_page_complete;
671 io_error:
672 cachefiles_io_error_obj(object, "Page read error on backing file");
673 ret = -ENOBUFS;
674 record_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 */
cachefiles_read_or_alloc_pages(struct fscache_retrieval * op,struct list_head * pages,unsigned * nr_pages,gfp_t gfp)683 int 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->bmap);
716 ASSERT(inode->i_mapping->a_ops->readpages);
717
718 /* calculate the shift required to use bmap */
719 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
720
721 pagevec_init(&pagevec);
722
723 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
724 op->op.flags |= FSCACHE_OP_ASYNC;
725 op->op.processor = cachefiles_read_copier;
726
727 INIT_LIST_HEAD(&backpages);
728 nrbackpages = 0;
729
730 ret = space ? -ENODATA : -ENOBUFS;
731 list_for_each_entry_safe(page, _n, pages, lru) {
732 sector_t block0, block;
733
734 /* we assume the absence or presence of the first block is a
735 * good enough indication for the page as a whole
736 * - TODO: don't use bmap() for this as it is _not_ actually
737 * good enough for this as it doesn't indicate errors, but
738 * it's all we've got for the moment
739 */
740 block0 = page->index;
741 block0 <<= shift;
742
743 block = inode->i_mapping->a_ops->bmap(inode->i_mapping,
744 block0);
745 _debug("%llx -> %llx",
746 (unsigned long long) block0,
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
782 all_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 */
cachefiles_allocate_page(struct fscache_retrieval * op,struct page * page,gfp_t gfp)798 int 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 */
cachefiles_allocate_pages(struct fscache_retrieval * op,struct list_head * pages,unsigned * nr_pages,gfp_t gfp)835 int 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 */
cachefiles_write_page(struct fscache_storage * op,struct page * page)881 int 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
949 error_eio:
950 ret = -EIO;
951 error_2:
952 if (ret == -EIO)
953 cachefiles_io_error_obj(object,
954 "Write page to backing file failed");
955 error:
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 */
cachefiles_uncache_page(struct fscache_object * _object,struct page * page)964 void 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 }
975