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 */
cachefiles_read_waiter(wait_queue_t * wait,unsigned mode,int sync,void * _key)24 static int cachefiles_read_waiter(wait_queue_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 fscache_retrieval *op = monitor->op;
31 struct wait_bit_key *key = _key;
32 struct page *page = wait->private;
33
34 ASSERT(key);
35
36 _enter("{%lu},%u,%d,{%p,%u}",
37 monitor->netfs_page->index, mode, sync,
38 key->flags, key->bit_nr);
39
40 if (key->flags != &page->flags ||
41 key->bit_nr != PG_locked)
42 return 0;
43
44 _debug("--- monitor %p %lx ---", page, page->flags);
45
46 if (!PageUptodate(page) && !PageError(page)) {
47 /* unlocked, not uptodate and not erronous? */
48 _debug("page probably truncated");
49 }
50
51 /* remove from the waitqueue */
52 list_del(&wait->task_list);
53
54 /* move onto the action list and queue for FS-Cache thread pool */
55 ASSERT(op);
56
57 /* We need to temporarily bump the usage count as we don't own a ref
58 * here otherwise cachefiles_read_copier() may free the op between the
59 * monitor being enqueued on the op->to_do list and the op getting
60 * enqueued on the work queue.
61 */
62 fscache_get_retrieval(op);
63
64 object = container_of(op->op.object, struct cachefiles_object, fscache);
65 spin_lock(&object->work_lock);
66 list_add_tail(&monitor->op_link, &op->to_do);
67 fscache_enqueue_retrieval(op);
68 spin_unlock(&object->work_lock);
69
70 fscache_put_retrieval(op);
71 return 0;
72 }
73
74 /*
75 * handle a probably truncated page
76 * - check to see if the page is still relevant and reissue the read if
77 * possible
78 * - return -EIO on error, -ENODATA if the page is gone, -EINPROGRESS if we
79 * must wait again and 0 if successful
80 */
cachefiles_read_reissue(struct cachefiles_object * object,struct cachefiles_one_read * monitor)81 static int cachefiles_read_reissue(struct cachefiles_object *object,
82 struct cachefiles_one_read *monitor)
83 {
84 struct address_space *bmapping = d_backing_inode(object->backer)->i_mapping;
85 struct page *backpage = monitor->back_page, *backpage2;
86 int ret;
87
88 _enter("{ino=%lx},{%lx,%lx}",
89 d_backing_inode(object->backer)->i_ino,
90 backpage->index, backpage->flags);
91
92 /* skip if the page was truncated away completely */
93 if (backpage->mapping != bmapping) {
94 _leave(" = -ENODATA [mapping]");
95 return -ENODATA;
96 }
97
98 backpage2 = find_get_page(bmapping, backpage->index);
99 if (!backpage2) {
100 _leave(" = -ENODATA [gone]");
101 return -ENODATA;
102 }
103
104 if (backpage != backpage2) {
105 put_page(backpage2);
106 _leave(" = -ENODATA [different]");
107 return -ENODATA;
108 }
109
110 /* the page is still there and we already have a ref on it, so we don't
111 * need a second */
112 put_page(backpage2);
113
114 INIT_LIST_HEAD(&monitor->op_link);
115 add_page_wait_queue(backpage, &monitor->monitor);
116
117 if (trylock_page(backpage)) {
118 ret = -EIO;
119 if (PageError(backpage))
120 goto unlock_discard;
121 ret = 0;
122 if (PageUptodate(backpage))
123 goto unlock_discard;
124
125 _debug("reissue read");
126 ret = bmapping->a_ops->readpage(NULL, backpage);
127 if (ret < 0)
128 goto discard;
129 }
130
131 /* but the page may have been read before the monitor was installed, so
132 * the monitor may miss the event - so we have to ensure that we do get
133 * one in such a case */
134 if (trylock_page(backpage)) {
135 _debug("jumpstart %p {%lx}", backpage, backpage->flags);
136 unlock_page(backpage);
137 }
138
139 /* it'll reappear on the todo list */
140 _leave(" = -EINPROGRESS");
141 return -EINPROGRESS;
142
143 unlock_discard:
144 unlock_page(backpage);
145 discard:
146 spin_lock_irq(&object->work_lock);
147 list_del(&monitor->op_link);
148 spin_unlock_irq(&object->work_lock);
149 _leave(" = %d", ret);
150 return ret;
151 }
152
153 /*
154 * copy data from backing pages to netfs pages to complete a read operation
155 * - driven by FS-Cache's thread pool
156 */
cachefiles_read_copier(struct fscache_operation * _op)157 static void cachefiles_read_copier(struct fscache_operation *_op)
158 {
159 struct cachefiles_one_read *monitor;
160 struct cachefiles_object *object;
161 struct fscache_retrieval *op;
162 int error, max;
163
164 op = container_of(_op, struct fscache_retrieval, op);
165 object = container_of(op->op.object,
166 struct cachefiles_object, fscache);
167
168 _enter("{ino=%lu}", d_backing_inode(object->backer)->i_ino);
169
170 max = 8;
171 spin_lock_irq(&object->work_lock);
172
173 while (!list_empty(&op->to_do)) {
174 monitor = list_entry(op->to_do.next,
175 struct cachefiles_one_read, op_link);
176 list_del(&monitor->op_link);
177
178 spin_unlock_irq(&object->work_lock);
179
180 _debug("- copy {%lu}", monitor->back_page->index);
181
182 recheck:
183 if (test_bit(FSCACHE_COOKIE_INVALIDATING,
184 &object->fscache.cookie->flags)) {
185 error = -ESTALE;
186 } else if (PageUptodate(monitor->back_page)) {
187 copy_highpage(monitor->netfs_page, monitor->back_page);
188 fscache_mark_page_cached(monitor->op,
189 monitor->netfs_page);
190 error = 0;
191 } else if (!PageError(monitor->back_page)) {
192 /* the page has probably been truncated */
193 error = cachefiles_read_reissue(object, monitor);
194 if (error == -EINPROGRESS)
195 goto next;
196 goto recheck;
197 } else {
198 cachefiles_io_error_obj(
199 object,
200 "Readpage failed on backing file %lx",
201 (unsigned long) monitor->back_page->flags);
202 error = -EIO;
203 }
204
205 page_cache_release(monitor->back_page);
206
207 fscache_end_io(op, monitor->netfs_page, error);
208 page_cache_release(monitor->netfs_page);
209 fscache_retrieval_complete(op, 1);
210 fscache_put_retrieval(op);
211 kfree(monitor);
212
213 next:
214 /* let the thread pool have some air occasionally */
215 max--;
216 if (max < 0 || need_resched()) {
217 if (!list_empty(&op->to_do))
218 fscache_enqueue_retrieval(op);
219 _leave(" [maxed out]");
220 return;
221 }
222
223 spin_lock_irq(&object->work_lock);
224 }
225
226 spin_unlock_irq(&object->work_lock);
227 _leave("");
228 }
229
230 /*
231 * read the corresponding page to the given set from the backing file
232 * - an uncertain page is simply discarded, to be tried again another time
233 */
cachefiles_read_backing_file_one(struct cachefiles_object * object,struct fscache_retrieval * op,struct page * netpage)234 static int cachefiles_read_backing_file_one(struct cachefiles_object *object,
235 struct fscache_retrieval *op,
236 struct page *netpage)
237 {
238 struct cachefiles_one_read *monitor;
239 struct address_space *bmapping;
240 struct page *newpage, *backpage;
241 int ret;
242
243 _enter("");
244
245 _debug("read back %p{%lu,%d}",
246 netpage, netpage->index, page_count(netpage));
247
248 monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
249 if (!monitor)
250 goto nomem;
251
252 monitor->netfs_page = netpage;
253 monitor->op = fscache_get_retrieval(op);
254
255 init_waitqueue_func_entry(&monitor->monitor, cachefiles_read_waiter);
256
257 /* attempt to get hold of the backing page */
258 bmapping = d_backing_inode(object->backer)->i_mapping;
259 newpage = NULL;
260
261 for (;;) {
262 backpage = find_get_page(bmapping, netpage->index);
263 if (backpage)
264 goto backing_page_already_present;
265
266 if (!newpage) {
267 newpage = __page_cache_alloc(cachefiles_gfp |
268 __GFP_COLD);
269 if (!newpage)
270 goto nomem_monitor;
271 }
272
273 ret = add_to_page_cache_lru(newpage, bmapping,
274 netpage->index, cachefiles_gfp);
275 if (ret == 0)
276 goto installed_new_backing_page;
277 if (ret != -EEXIST)
278 goto nomem_page;
279 }
280
281 /* we've installed a new backing page, so now we need to start
282 * it reading */
283 installed_new_backing_page:
284 _debug("- new %p", newpage);
285
286 backpage = newpage;
287 newpage = NULL;
288
289 read_backing_page:
290 ret = bmapping->a_ops->readpage(NULL, backpage);
291 if (ret < 0)
292 goto read_error;
293
294 /* set the monitor to transfer the data across */
295 monitor_backing_page:
296 _debug("- monitor add");
297
298 /* install the monitor */
299 page_cache_get(monitor->netfs_page);
300 page_cache_get(backpage);
301 monitor->back_page = backpage;
302 monitor->monitor.private = backpage;
303 add_page_wait_queue(backpage, &monitor->monitor);
304 monitor = NULL;
305
306 /* but the page may have been read before the monitor was installed, so
307 * the monitor may miss the event - so we have to ensure that we do get
308 * one in such a case */
309 if (trylock_page(backpage)) {
310 _debug("jumpstart %p {%lx}", backpage, backpage->flags);
311 unlock_page(backpage);
312 }
313 goto success;
314
315 /* if the backing page is already present, it can be in one of
316 * three states: read in progress, read failed or read okay */
317 backing_page_already_present:
318 _debug("- present");
319
320 if (newpage) {
321 page_cache_release(newpage);
322 newpage = NULL;
323 }
324
325 if (PageError(backpage))
326 goto io_error;
327
328 if (PageUptodate(backpage))
329 goto backing_page_already_uptodate;
330
331 if (!trylock_page(backpage))
332 goto monitor_backing_page;
333 _debug("read %p {%lx}", backpage, backpage->flags);
334 goto read_backing_page;
335
336 /* the backing page is already up to date, attach the netfs
337 * page to the pagecache and LRU and copy the data across */
338 backing_page_already_uptodate:
339 _debug("- uptodate");
340
341 fscache_mark_page_cached(op, netpage);
342
343 copy_highpage(netpage, backpage);
344 fscache_end_io(op, netpage, 0);
345 fscache_retrieval_complete(op, 1);
346
347 success:
348 _debug("success");
349 ret = 0;
350
351 out:
352 if (backpage)
353 page_cache_release(backpage);
354 if (monitor) {
355 fscache_put_retrieval(monitor->op);
356 kfree(monitor);
357 }
358 _leave(" = %d", ret);
359 return ret;
360
361 read_error:
362 _debug("read error %d", ret);
363 if (ret == -ENOMEM) {
364 fscache_retrieval_complete(op, 1);
365 goto out;
366 }
367 io_error:
368 cachefiles_io_error_obj(object, "Page read error on backing file");
369 fscache_retrieval_complete(op, 1);
370 ret = -ENOBUFS;
371 goto out;
372
373 nomem_page:
374 page_cache_release(newpage);
375 nomem_monitor:
376 fscache_put_retrieval(monitor->op);
377 kfree(monitor);
378 nomem:
379 fscache_retrieval_complete(op, 1);
380 _leave(" = -ENOMEM");
381 return -ENOMEM;
382 }
383
384 /*
385 * read a page from the cache or allocate a block in which to store it
386 * - cache withdrawal is prevented by the caller
387 * - returns -EINTR if interrupted
388 * - returns -ENOMEM if ran out of memory
389 * - returns -ENOBUFS if no buffers can be made available
390 * - returns -ENOBUFS if page is beyond EOF
391 * - if the page is backed by a block in the cache:
392 * - a read will be started which will call the callback on completion
393 * - 0 will be returned
394 * - else if the page is unbacked:
395 * - the metadata will be retained
396 * - -ENODATA will be returned
397 */
cachefiles_read_or_alloc_page(struct fscache_retrieval * op,struct page * page,gfp_t gfp)398 int cachefiles_read_or_alloc_page(struct fscache_retrieval *op,
399 struct page *page,
400 gfp_t gfp)
401 {
402 struct cachefiles_object *object;
403 struct cachefiles_cache *cache;
404 struct inode *inode;
405 sector_t block0, block;
406 unsigned shift;
407 int ret;
408
409 object = container_of(op->op.object,
410 struct cachefiles_object, fscache);
411 cache = container_of(object->fscache.cache,
412 struct cachefiles_cache, cache);
413
414 _enter("{%p},{%lx},,,", object, page->index);
415
416 if (!object->backer)
417 goto enobufs;
418
419 inode = d_backing_inode(object->backer);
420 ASSERT(S_ISREG(inode->i_mode));
421 ASSERT(inode->i_mapping->a_ops->bmap);
422 ASSERT(inode->i_mapping->a_ops->readpages);
423
424 /* calculate the shift required to use bmap */
425 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
426
427 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
428 op->op.flags |= FSCACHE_OP_ASYNC;
429 op->op.processor = cachefiles_read_copier;
430
431 /* we assume the absence or presence of the first block is a good
432 * enough indication for the page as a whole
433 * - TODO: don't use bmap() for this as it is _not_ actually good
434 * enough for this as it doesn't indicate errors, but it's all we've
435 * got for the moment
436 */
437 block0 = page->index;
438 block0 <<= shift;
439
440 block = inode->i_mapping->a_ops->bmap(inode->i_mapping, block0);
441 _debug("%llx -> %llx",
442 (unsigned long long) block0,
443 (unsigned long long) block);
444
445 if (block) {
446 /* submit the apparently valid page to the backing fs to be
447 * read from disk */
448 ret = cachefiles_read_backing_file_one(object, op, page);
449 } else if (cachefiles_has_space(cache, 0, 1) == 0) {
450 /* there's space in the cache we can use */
451 fscache_mark_page_cached(op, page);
452 fscache_retrieval_complete(op, 1);
453 ret = -ENODATA;
454 } else {
455 goto enobufs;
456 }
457
458 _leave(" = %d", ret);
459 return ret;
460
461 enobufs:
462 fscache_retrieval_complete(op, 1);
463 _leave(" = -ENOBUFS");
464 return -ENOBUFS;
465 }
466
467 /*
468 * read the corresponding pages to the given set from the backing file
469 * - any uncertain pages are simply discarded, to be tried again another time
470 */
cachefiles_read_backing_file(struct cachefiles_object * object,struct fscache_retrieval * op,struct list_head * list)471 static int cachefiles_read_backing_file(struct cachefiles_object *object,
472 struct fscache_retrieval *op,
473 struct list_head *list)
474 {
475 struct cachefiles_one_read *monitor = NULL;
476 struct address_space *bmapping = d_backing_inode(object->backer)->i_mapping;
477 struct page *newpage = NULL, *netpage, *_n, *backpage = NULL;
478 int ret = 0;
479
480 _enter("");
481
482 list_for_each_entry_safe(netpage, _n, list, lru) {
483 list_del(&netpage->lru);
484
485 _debug("read back %p{%lu,%d}",
486 netpage, netpage->index, page_count(netpage));
487
488 if (!monitor) {
489 monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
490 if (!monitor)
491 goto nomem;
492
493 monitor->op = fscache_get_retrieval(op);
494 init_waitqueue_func_entry(&monitor->monitor,
495 cachefiles_read_waiter);
496 }
497
498 for (;;) {
499 backpage = find_get_page(bmapping, netpage->index);
500 if (backpage)
501 goto backing_page_already_present;
502
503 if (!newpage) {
504 newpage = __page_cache_alloc(cachefiles_gfp |
505 __GFP_COLD);
506 if (!newpage)
507 goto nomem;
508 }
509
510 ret = add_to_page_cache_lru(newpage, bmapping,
511 netpage->index,
512 cachefiles_gfp);
513 if (ret == 0)
514 goto installed_new_backing_page;
515 if (ret != -EEXIST)
516 goto nomem;
517 }
518
519 /* we've installed a new backing page, so now we need
520 * to start it reading */
521 installed_new_backing_page:
522 _debug("- new %p", newpage);
523
524 backpage = newpage;
525 newpage = NULL;
526
527 reread_backing_page:
528 ret = bmapping->a_ops->readpage(NULL, backpage);
529 if (ret < 0)
530 goto read_error;
531
532 /* add the netfs page to the pagecache and LRU, and set the
533 * monitor to transfer the data across */
534 monitor_backing_page:
535 _debug("- monitor add");
536
537 ret = add_to_page_cache_lru(netpage, op->mapping,
538 netpage->index, cachefiles_gfp);
539 if (ret < 0) {
540 if (ret == -EEXIST) {
541 page_cache_release(netpage);
542 fscache_retrieval_complete(op, 1);
543 continue;
544 }
545 goto nomem;
546 }
547
548 /* install a monitor */
549 page_cache_get(netpage);
550 monitor->netfs_page = netpage;
551
552 page_cache_get(backpage);
553 monitor->back_page = backpage;
554 monitor->monitor.private = backpage;
555 add_page_wait_queue(backpage, &monitor->monitor);
556 monitor = NULL;
557
558 /* but the page may have been read before the monitor was
559 * installed, so the monitor may miss the event - so we have to
560 * ensure that we do get one in such a case */
561 if (trylock_page(backpage)) {
562 _debug("2unlock %p {%lx}", backpage, backpage->flags);
563 unlock_page(backpage);
564 }
565
566 page_cache_release(backpage);
567 backpage = NULL;
568
569 page_cache_release(netpage);
570 netpage = NULL;
571 continue;
572
573 /* if the backing page is already present, it can be in one of
574 * three states: read in progress, read failed or read okay */
575 backing_page_already_present:
576 _debug("- present %p", backpage);
577
578 if (PageError(backpage))
579 goto io_error;
580
581 if (PageUptodate(backpage))
582 goto backing_page_already_uptodate;
583
584 _debug("- not ready %p{%lx}", backpage, backpage->flags);
585
586 if (!trylock_page(backpage))
587 goto monitor_backing_page;
588
589 if (PageError(backpage)) {
590 _debug("error %lx", backpage->flags);
591 unlock_page(backpage);
592 goto io_error;
593 }
594
595 if (PageUptodate(backpage))
596 goto backing_page_already_uptodate_unlock;
597
598 /* we've locked a page that's neither up to date nor erroneous,
599 * so we need to attempt to read it again */
600 goto reread_backing_page;
601
602 /* the backing page is already up to date, attach the netfs
603 * page to the pagecache and LRU and copy the data across */
604 backing_page_already_uptodate_unlock:
605 _debug("uptodate %lx", backpage->flags);
606 unlock_page(backpage);
607 backing_page_already_uptodate:
608 _debug("- uptodate");
609
610 ret = add_to_page_cache_lru(netpage, op->mapping,
611 netpage->index, cachefiles_gfp);
612 if (ret < 0) {
613 if (ret == -EEXIST) {
614 page_cache_release(netpage);
615 fscache_retrieval_complete(op, 1);
616 continue;
617 }
618 goto nomem;
619 }
620
621 copy_highpage(netpage, backpage);
622
623 page_cache_release(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 page_cache_release(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 page_cache_release(newpage);
644 if (netpage)
645 page_cache_release(netpage);
646 if (backpage)
647 page_cache_release(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 page_cache_release(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, 0);
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, 0);
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 {
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 }
974