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 "internal.h"
16
17 /*
18 * detect wake up events generated by the unlocking of pages in which we're
19 * interested
20 * - we use this to detect read completion of backing pages
21 * - the caller holds the waitqueue lock
22 */
cachefiles_read_waiter(wait_queue_t * wait,unsigned mode,int sync,void * _key)23 static int cachefiles_read_waiter(wait_queue_t *wait, unsigned mode,
24 int sync, void *_key)
25 {
26 struct cachefiles_one_read *monitor =
27 container_of(wait, struct cachefiles_one_read, monitor);
28 struct cachefiles_object *object;
29 struct wait_bit_key *key = _key;
30 struct page *page = wait->private;
31
32 ASSERT(key);
33
34 _enter("{%lu},%u,%d,{%p,%u}",
35 monitor->netfs_page->index, mode, sync,
36 key->flags, key->bit_nr);
37
38 if (key->flags != &page->flags ||
39 key->bit_nr != PG_locked)
40 return 0;
41
42 _debug("--- monitor %p %lx ---", page, page->flags);
43
44 if (!PageUptodate(page) && !PageError(page)) {
45 /* unlocked, not uptodate and not erronous? */
46 _debug("page probably truncated");
47 }
48
49 /* remove from the waitqueue */
50 list_del(&wait->task_list);
51
52 /* move onto the action list and queue for FS-Cache thread pool */
53 ASSERT(monitor->op);
54
55 object = container_of(monitor->op->op.object,
56 struct cachefiles_object, fscache);
57
58 spin_lock(&object->work_lock);
59 list_add_tail(&monitor->op_link, &monitor->op->to_do);
60 spin_unlock(&object->work_lock);
61
62 fscache_enqueue_retrieval(monitor->op);
63 return 0;
64 }
65
66 /*
67 * handle a probably truncated page
68 * - check to see if the page is still relevant and reissue the read if
69 * possible
70 * - return -EIO on error, -ENODATA if the page is gone, -EINPROGRESS if we
71 * must wait again and 0 if successful
72 */
cachefiles_read_reissue(struct cachefiles_object * object,struct cachefiles_one_read * monitor)73 static int cachefiles_read_reissue(struct cachefiles_object *object,
74 struct cachefiles_one_read *monitor)
75 {
76 struct address_space *bmapping = object->backer->d_inode->i_mapping;
77 struct page *backpage = monitor->back_page, *backpage2;
78 int ret;
79
80 _enter("{ino=%lx},{%lx,%lx}",
81 object->backer->d_inode->i_ino,
82 backpage->index, backpage->flags);
83
84 /* skip if the page was truncated away completely */
85 if (backpage->mapping != bmapping) {
86 _leave(" = -ENODATA [mapping]");
87 return -ENODATA;
88 }
89
90 backpage2 = find_get_page(bmapping, backpage->index);
91 if (!backpage2) {
92 _leave(" = -ENODATA [gone]");
93 return -ENODATA;
94 }
95
96 if (backpage != backpage2) {
97 put_page(backpage2);
98 _leave(" = -ENODATA [different]");
99 return -ENODATA;
100 }
101
102 /* the page is still there and we already have a ref on it, so we don't
103 * need a second */
104 put_page(backpage2);
105
106 INIT_LIST_HEAD(&monitor->op_link);
107 add_page_wait_queue(backpage, &monitor->monitor);
108
109 if (trylock_page(backpage)) {
110 ret = -EIO;
111 if (PageError(backpage))
112 goto unlock_discard;
113 ret = 0;
114 if (PageUptodate(backpage))
115 goto unlock_discard;
116
117 _debug("reissue read");
118 ret = bmapping->a_ops->readpage(NULL, backpage);
119 if (ret < 0)
120 goto unlock_discard;
121 }
122
123 /* but the page may have been read before the monitor was installed, so
124 * the monitor may miss the event - so we have to ensure that we do get
125 * one in such a case */
126 if (trylock_page(backpage)) {
127 _debug("jumpstart %p {%lx}", backpage, backpage->flags);
128 unlock_page(backpage);
129 }
130
131 /* it'll reappear on the todo list */
132 _leave(" = -EINPROGRESS");
133 return -EINPROGRESS;
134
135 unlock_discard:
136 unlock_page(backpage);
137 spin_lock_irq(&object->work_lock);
138 list_del(&monitor->op_link);
139 spin_unlock_irq(&object->work_lock);
140 _leave(" = %d", ret);
141 return ret;
142 }
143
144 /*
145 * copy data from backing pages to netfs pages to complete a read operation
146 * - driven by FS-Cache's thread pool
147 */
cachefiles_read_copier(struct fscache_operation * _op)148 static void cachefiles_read_copier(struct fscache_operation *_op)
149 {
150 struct cachefiles_one_read *monitor;
151 struct cachefiles_object *object;
152 struct fscache_retrieval *op;
153 struct pagevec pagevec;
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}", object->backer->d_inode->i_ino);
161
162 pagevec_init(&pagevec, 0);
163
164 max = 8;
165 spin_lock_irq(&object->work_lock);
166
167 while (!list_empty(&op->to_do)) {
168 monitor = list_entry(op->to_do.next,
169 struct cachefiles_one_read, op_link);
170 list_del(&monitor->op_link);
171
172 spin_unlock_irq(&object->work_lock);
173
174 _debug("- copy {%lu}", monitor->back_page->index);
175
176 recheck:
177 if (test_bit(FSCACHE_COOKIE_INVALIDATING,
178 &object->fscache.cookie->flags)) {
179 error = -ESTALE;
180 } else if (PageUptodate(monitor->back_page)) {
181 copy_highpage(monitor->netfs_page, monitor->back_page);
182 fscache_mark_page_cached(monitor->op,
183 monitor->netfs_page);
184 error = 0;
185 } else if (!PageError(monitor->back_page)) {
186 /* the page has probably been truncated */
187 error = cachefiles_read_reissue(object, monitor);
188 if (error == -EINPROGRESS)
189 goto next;
190 goto recheck;
191 } else {
192 cachefiles_io_error_obj(
193 object,
194 "Readpage failed on backing file %lx",
195 (unsigned long) monitor->back_page->flags);
196 error = -EIO;
197 }
198
199 page_cache_release(monitor->back_page);
200
201 fscache_end_io(op, monitor->netfs_page, error);
202 page_cache_release(monitor->netfs_page);
203 fscache_retrieval_complete(op, 1);
204 fscache_put_retrieval(op);
205 kfree(monitor);
206
207 next:
208 /* let the thread pool have some air occasionally */
209 max--;
210 if (max < 0 || need_resched()) {
211 if (!list_empty(&op->to_do))
212 fscache_enqueue_retrieval(op);
213 _leave(" [maxed out]");
214 return;
215 }
216
217 spin_lock_irq(&object->work_lock);
218 }
219
220 spin_unlock_irq(&object->work_lock);
221 _leave("");
222 }
223
224 /*
225 * read the corresponding page to the given set from the backing file
226 * - an uncertain page is simply discarded, to be tried again another time
227 */
cachefiles_read_backing_file_one(struct cachefiles_object * object,struct fscache_retrieval * op,struct page * netpage,struct pagevec * pagevec)228 static int cachefiles_read_backing_file_one(struct cachefiles_object *object,
229 struct fscache_retrieval *op,
230 struct page *netpage,
231 struct pagevec *pagevec)
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 pagevec_reinit(pagevec);
241
242 _debug("read back %p{%lu,%d}",
243 netpage, netpage->index, page_count(netpage));
244
245 monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
246 if (!monitor)
247 goto nomem;
248
249 monitor->netfs_page = netpage;
250 monitor->op = fscache_get_retrieval(op);
251
252 init_waitqueue_func_entry(&monitor->monitor, cachefiles_read_waiter);
253
254 /* attempt to get hold of the backing page */
255 bmapping = object->backer->d_inode->i_mapping;
256 newpage = NULL;
257
258 for (;;) {
259 backpage = find_get_page(bmapping, netpage->index);
260 if (backpage)
261 goto backing_page_already_present;
262
263 if (!newpage) {
264 newpage = __page_cache_alloc(cachefiles_gfp |
265 __GFP_COLD);
266 if (!newpage)
267 goto nomem_monitor;
268 }
269
270 ret = add_to_page_cache(newpage, bmapping,
271 netpage->index, cachefiles_gfp);
272 if (ret == 0)
273 goto installed_new_backing_page;
274 if (ret != -EEXIST)
275 goto nomem_page;
276 }
277
278 /* we've installed a new backing page, so now we need to add it
279 * to the LRU list and start it reading */
280 installed_new_backing_page:
281 _debug("- new %p", newpage);
282
283 backpage = newpage;
284 newpage = NULL;
285
286 page_cache_get(backpage);
287 pagevec_add(pagevec, backpage);
288 __pagevec_lru_add_file(pagevec);
289
290 read_backing_page:
291 ret = bmapping->a_ops->readpage(NULL, backpage);
292 if (ret < 0)
293 goto read_error;
294
295 /* set the monitor to transfer the data across */
296 monitor_backing_page:
297 _debug("- monitor add");
298
299 /* install the monitor */
300 page_cache_get(monitor->netfs_page);
301 page_cache_get(backpage);
302 monitor->back_page = backpage;
303 monitor->monitor.private = backpage;
304 add_page_wait_queue(backpage, &monitor->monitor);
305 monitor = NULL;
306
307 /* but the page may have been read before the monitor was installed, so
308 * the monitor may miss the event - so we have to ensure that we do get
309 * one in such a case */
310 if (trylock_page(backpage)) {
311 _debug("jumpstart %p {%lx}", backpage, backpage->flags);
312 unlock_page(backpage);
313 }
314 goto success;
315
316 /* if the backing page is already present, it can be in one of
317 * three states: read in progress, read failed or read okay */
318 backing_page_already_present:
319 _debug("- present");
320
321 if (newpage) {
322 page_cache_release(newpage);
323 newpage = NULL;
324 }
325
326 if (PageError(backpage))
327 goto io_error;
328
329 if (PageUptodate(backpage))
330 goto backing_page_already_uptodate;
331
332 if (!trylock_page(backpage))
333 goto monitor_backing_page;
334 _debug("read %p {%lx}", backpage, backpage->flags);
335 goto read_backing_page;
336
337 /* the backing page is already up to date, attach the netfs
338 * page to the pagecache and LRU and copy the data across */
339 backing_page_already_uptodate:
340 _debug("- uptodate");
341
342 fscache_mark_page_cached(op, netpage);
343
344 copy_highpage(netpage, backpage);
345 fscache_end_io(op, netpage, 0);
346 fscache_retrieval_complete(op, 1);
347
348 success:
349 _debug("success");
350 ret = 0;
351
352 out:
353 if (backpage)
354 page_cache_release(backpage);
355 if (monitor) {
356 fscache_put_retrieval(monitor->op);
357 kfree(monitor);
358 }
359 _leave(" = %d", ret);
360 return ret;
361
362 read_error:
363 _debug("read error %d", ret);
364 if (ret == -ENOMEM) {
365 fscache_retrieval_complete(op, 1);
366 goto out;
367 }
368 io_error:
369 cachefiles_io_error_obj(object, "Page read error on backing file");
370 fscache_retrieval_complete(op, 1);
371 ret = -ENOBUFS;
372 goto out;
373
374 nomem_page:
375 page_cache_release(newpage);
376 nomem_monitor:
377 fscache_put_retrieval(monitor->op);
378 kfree(monitor);
379 nomem:
380 fscache_retrieval_complete(op, 1);
381 _leave(" = -ENOMEM");
382 return -ENOMEM;
383 }
384
385 /*
386 * read a page from the cache or allocate a block in which to store it
387 * - cache withdrawal is prevented by the caller
388 * - returns -EINTR if interrupted
389 * - returns -ENOMEM if ran out of memory
390 * - returns -ENOBUFS if no buffers can be made available
391 * - returns -ENOBUFS if page is beyond EOF
392 * - if the page is backed by a block in the cache:
393 * - a read will be started which will call the callback on completion
394 * - 0 will be returned
395 * - else if the page is unbacked:
396 * - the metadata will be retained
397 * - -ENODATA will be returned
398 */
cachefiles_read_or_alloc_page(struct fscache_retrieval * op,struct page * page,gfp_t gfp)399 int cachefiles_read_or_alloc_page(struct fscache_retrieval *op,
400 struct page *page,
401 gfp_t gfp)
402 {
403 struct cachefiles_object *object;
404 struct cachefiles_cache *cache;
405 struct pagevec pagevec;
406 struct inode *inode;
407 sector_t block0, block;
408 unsigned shift;
409 int ret;
410
411 object = container_of(op->op.object,
412 struct cachefiles_object, fscache);
413 cache = container_of(object->fscache.cache,
414 struct cachefiles_cache, cache);
415
416 _enter("{%p},{%lx},,,", object, page->index);
417
418 if (!object->backer)
419 goto enobufs;
420
421 inode = object->backer->d_inode;
422 ASSERT(S_ISREG(inode->i_mode));
423 ASSERT(inode->i_mapping->a_ops->bmap);
424 ASSERT(inode->i_mapping->a_ops->readpages);
425
426 /* calculate the shift required to use bmap */
427 if (inode->i_sb->s_blocksize > PAGE_SIZE)
428 goto enobufs;
429
430 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
431
432 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
433 op->op.flags |= FSCACHE_OP_ASYNC;
434 op->op.processor = cachefiles_read_copier;
435
436 pagevec_init(&pagevec, 0);
437
438 /* we assume the absence or presence of the first block is a good
439 * enough indication for the page as a whole
440 * - TODO: don't use bmap() for this as it is _not_ actually good
441 * enough for this as it doesn't indicate errors, but it's all we've
442 * got for the moment
443 */
444 block0 = page->index;
445 block0 <<= shift;
446
447 block = inode->i_mapping->a_ops->bmap(inode->i_mapping, block0);
448 _debug("%llx -> %llx",
449 (unsigned long long) block0,
450 (unsigned long long) block);
451
452 if (block) {
453 /* submit the apparently valid page to the backing fs to be
454 * read from disk */
455 ret = cachefiles_read_backing_file_one(object, op, page,
456 &pagevec);
457 } else if (cachefiles_has_space(cache, 0, 1) == 0) {
458 /* there's space in the cache we can use */
459 fscache_mark_page_cached(op, page);
460 fscache_retrieval_complete(op, 1);
461 ret = -ENODATA;
462 } else {
463 goto enobufs;
464 }
465
466 _leave(" = %d", ret);
467 return ret;
468
469 enobufs:
470 fscache_retrieval_complete(op, 1);
471 _leave(" = -ENOBUFS");
472 return -ENOBUFS;
473 }
474
475 /*
476 * read the corresponding pages to the given set from the backing file
477 * - any uncertain pages are simply discarded, to be tried again another time
478 */
cachefiles_read_backing_file(struct cachefiles_object * object,struct fscache_retrieval * op,struct list_head * list)479 static int cachefiles_read_backing_file(struct cachefiles_object *object,
480 struct fscache_retrieval *op,
481 struct list_head *list)
482 {
483 struct cachefiles_one_read *monitor = NULL;
484 struct address_space *bmapping = object->backer->d_inode->i_mapping;
485 struct pagevec lru_pvec;
486 struct page *newpage = NULL, *netpage, *_n, *backpage = NULL;
487 int ret = 0;
488
489 _enter("");
490
491 pagevec_init(&lru_pvec, 0);
492
493 list_for_each_entry_safe(netpage, _n, list, lru) {
494 list_del(&netpage->lru);
495
496 _debug("read back %p{%lu,%d}",
497 netpage, netpage->index, page_count(netpage));
498
499 if (!monitor) {
500 monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
501 if (!monitor)
502 goto nomem;
503
504 monitor->op = fscache_get_retrieval(op);
505 init_waitqueue_func_entry(&monitor->monitor,
506 cachefiles_read_waiter);
507 }
508
509 for (;;) {
510 backpage = find_get_page(bmapping, netpage->index);
511 if (backpage)
512 goto backing_page_already_present;
513
514 if (!newpage) {
515 newpage = __page_cache_alloc(cachefiles_gfp |
516 __GFP_COLD);
517 if (!newpage)
518 goto nomem;
519 }
520
521 ret = add_to_page_cache(newpage, bmapping,
522 netpage->index, cachefiles_gfp);
523 if (ret == 0)
524 goto installed_new_backing_page;
525 if (ret != -EEXIST)
526 goto nomem;
527 }
528
529 /* we've installed a new backing page, so now we need to add it
530 * to the LRU list and start it reading */
531 installed_new_backing_page:
532 _debug("- new %p", newpage);
533
534 backpage = newpage;
535 newpage = NULL;
536
537 page_cache_get(backpage);
538 if (!pagevec_add(&lru_pvec, backpage))
539 __pagevec_lru_add_file(&lru_pvec);
540
541 reread_backing_page:
542 ret = bmapping->a_ops->readpage(NULL, backpage);
543 if (ret < 0)
544 goto read_error;
545
546 /* add the netfs page to the pagecache and LRU, and set the
547 * monitor to transfer the data across */
548 monitor_backing_page:
549 _debug("- monitor add");
550
551 ret = add_to_page_cache(netpage, op->mapping, netpage->index,
552 cachefiles_gfp);
553 if (ret < 0) {
554 if (ret == -EEXIST) {
555 page_cache_release(netpage);
556 fscache_retrieval_complete(op, 1);
557 continue;
558 }
559 goto nomem;
560 }
561
562 page_cache_get(netpage);
563 if (!pagevec_add(&lru_pvec, netpage))
564 __pagevec_lru_add_file(&lru_pvec);
565
566 /* install a monitor */
567 page_cache_get(netpage);
568 monitor->netfs_page = netpage;
569
570 page_cache_get(backpage);
571 monitor->back_page = backpage;
572 monitor->monitor.private = backpage;
573 add_page_wait_queue(backpage, &monitor->monitor);
574 monitor = NULL;
575
576 /* but the page may have been read before the monitor was
577 * installed, so the monitor may miss the event - so we have to
578 * ensure that we do get one in such a case */
579 if (trylock_page(backpage)) {
580 _debug("2unlock %p {%lx}", backpage, backpage->flags);
581 unlock_page(backpage);
582 }
583
584 page_cache_release(backpage);
585 backpage = NULL;
586
587 page_cache_release(netpage);
588 netpage = NULL;
589 continue;
590
591 /* if the backing page is already present, it can be in one of
592 * three states: read in progress, read failed or read okay */
593 backing_page_already_present:
594 _debug("- present %p", backpage);
595
596 if (PageError(backpage))
597 goto io_error;
598
599 if (PageUptodate(backpage))
600 goto backing_page_already_uptodate;
601
602 _debug("- not ready %p{%lx}", backpage, backpage->flags);
603
604 if (!trylock_page(backpage))
605 goto monitor_backing_page;
606
607 if (PageError(backpage)) {
608 _debug("error %lx", backpage->flags);
609 unlock_page(backpage);
610 goto io_error;
611 }
612
613 if (PageUptodate(backpage))
614 goto backing_page_already_uptodate_unlock;
615
616 /* we've locked a page that's neither up to date nor erroneous,
617 * so we need to attempt to read it again */
618 goto reread_backing_page;
619
620 /* the backing page is already up to date, attach the netfs
621 * page to the pagecache and LRU and copy the data across */
622 backing_page_already_uptodate_unlock:
623 _debug("uptodate %lx", backpage->flags);
624 unlock_page(backpage);
625 backing_page_already_uptodate:
626 _debug("- uptodate");
627
628 ret = add_to_page_cache(netpage, op->mapping, netpage->index,
629 cachefiles_gfp);
630 if (ret < 0) {
631 if (ret == -EEXIST) {
632 page_cache_release(netpage);
633 fscache_retrieval_complete(op, 1);
634 continue;
635 }
636 goto nomem;
637 }
638
639 copy_highpage(netpage, backpage);
640
641 page_cache_release(backpage);
642 backpage = NULL;
643
644 fscache_mark_page_cached(op, netpage);
645
646 page_cache_get(netpage);
647 if (!pagevec_add(&lru_pvec, netpage))
648 __pagevec_lru_add_file(&lru_pvec);
649
650 /* the netpage is unlocked and marked up to date here */
651 fscache_end_io(op, netpage, 0);
652 page_cache_release(netpage);
653 netpage = NULL;
654 fscache_retrieval_complete(op, 1);
655 continue;
656 }
657
658 netpage = NULL;
659
660 _debug("out");
661
662 out:
663 /* tidy up */
664 pagevec_lru_add_file(&lru_pvec);
665
666 if (newpage)
667 page_cache_release(newpage);
668 if (netpage)
669 page_cache_release(netpage);
670 if (backpage)
671 page_cache_release(backpage);
672 if (monitor) {
673 fscache_put_retrieval(op);
674 kfree(monitor);
675 }
676
677 list_for_each_entry_safe(netpage, _n, list, lru) {
678 list_del(&netpage->lru);
679 page_cache_release(netpage);
680 fscache_retrieval_complete(op, 1);
681 }
682
683 _leave(" = %d", ret);
684 return ret;
685
686 nomem:
687 _debug("nomem");
688 ret = -ENOMEM;
689 goto record_page_complete;
690
691 read_error:
692 _debug("read error %d", ret);
693 if (ret == -ENOMEM)
694 goto record_page_complete;
695 io_error:
696 cachefiles_io_error_obj(object, "Page read error on backing file");
697 ret = -ENOBUFS;
698 record_page_complete:
699 fscache_retrieval_complete(op, 1);
700 goto out;
701 }
702
703 /*
704 * read a list of pages from the cache or allocate blocks in which to store
705 * them
706 */
cachefiles_read_or_alloc_pages(struct fscache_retrieval * op,struct list_head * pages,unsigned * nr_pages,gfp_t gfp)707 int cachefiles_read_or_alloc_pages(struct fscache_retrieval *op,
708 struct list_head *pages,
709 unsigned *nr_pages,
710 gfp_t gfp)
711 {
712 struct cachefiles_object *object;
713 struct cachefiles_cache *cache;
714 struct list_head backpages;
715 struct pagevec pagevec;
716 struct inode *inode;
717 struct page *page, *_n;
718 unsigned shift, nrbackpages;
719 int ret, ret2, space;
720
721 object = container_of(op->op.object,
722 struct cachefiles_object, fscache);
723 cache = container_of(object->fscache.cache,
724 struct cachefiles_cache, cache);
725
726 _enter("{OBJ%x,%d},,%d,,",
727 object->fscache.debug_id, atomic_read(&op->op.usage),
728 *nr_pages);
729
730 if (!object->backer)
731 goto all_enobufs;
732
733 space = 1;
734 if (cachefiles_has_space(cache, 0, *nr_pages) < 0)
735 space = 0;
736
737 inode = object->backer->d_inode;
738 ASSERT(S_ISREG(inode->i_mode));
739 ASSERT(inode->i_mapping->a_ops->bmap);
740 ASSERT(inode->i_mapping->a_ops->readpages);
741
742 /* calculate the shift required to use bmap */
743 if (inode->i_sb->s_blocksize > PAGE_SIZE)
744 goto all_enobufs;
745
746 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
747
748 pagevec_init(&pagevec, 0);
749
750 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
751 op->op.flags |= FSCACHE_OP_ASYNC;
752 op->op.processor = cachefiles_read_copier;
753
754 INIT_LIST_HEAD(&backpages);
755 nrbackpages = 0;
756
757 ret = space ? -ENODATA : -ENOBUFS;
758 list_for_each_entry_safe(page, _n, pages, lru) {
759 sector_t block0, block;
760
761 /* we assume the absence or presence of the first block is a
762 * good enough indication for the page as a whole
763 * - TODO: don't use bmap() for this as it is _not_ actually
764 * good enough for this as it doesn't indicate errors, but
765 * it's all we've got for the moment
766 */
767 block0 = page->index;
768 block0 <<= shift;
769
770 block = inode->i_mapping->a_ops->bmap(inode->i_mapping,
771 block0);
772 _debug("%llx -> %llx",
773 (unsigned long long) block0,
774 (unsigned long long) block);
775
776 if (block) {
777 /* we have data - add it to the list to give to the
778 * backing fs */
779 list_move(&page->lru, &backpages);
780 (*nr_pages)--;
781 nrbackpages++;
782 } else if (space && pagevec_add(&pagevec, page) == 0) {
783 fscache_mark_pages_cached(op, &pagevec);
784 fscache_retrieval_complete(op, 1);
785 ret = -ENODATA;
786 } else {
787 fscache_retrieval_complete(op, 1);
788 }
789 }
790
791 if (pagevec_count(&pagevec) > 0)
792 fscache_mark_pages_cached(op, &pagevec);
793
794 if (list_empty(pages))
795 ret = 0;
796
797 /* submit the apparently valid pages to the backing fs to be read from
798 * disk */
799 if (nrbackpages > 0) {
800 ret2 = cachefiles_read_backing_file(object, op, &backpages);
801 if (ret2 == -ENOMEM || ret2 == -EINTR)
802 ret = ret2;
803 }
804
805 _leave(" = %d [nr=%u%s]",
806 ret, *nr_pages, list_empty(pages) ? " empty" : "");
807 return ret;
808
809 all_enobufs:
810 fscache_retrieval_complete(op, *nr_pages);
811 return -ENOBUFS;
812 }
813
814 /*
815 * allocate a block in the cache in which to store a page
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 no buffers can be made available
820 * - returns -ENOBUFS if page is beyond EOF
821 * - otherwise:
822 * - the metadata will be retained
823 * - 0 will be returned
824 */
cachefiles_allocate_page(struct fscache_retrieval * op,struct page * page,gfp_t gfp)825 int cachefiles_allocate_page(struct fscache_retrieval *op,
826 struct page *page,
827 gfp_t gfp)
828 {
829 struct cachefiles_object *object;
830 struct cachefiles_cache *cache;
831 int ret;
832
833 object = container_of(op->op.object,
834 struct cachefiles_object, fscache);
835 cache = container_of(object->fscache.cache,
836 struct cachefiles_cache, cache);
837
838 _enter("%p,{%lx},", object, page->index);
839
840 ret = cachefiles_has_space(cache, 0, 1);
841 if (ret == 0)
842 fscache_mark_page_cached(op, page);
843 else
844 ret = -ENOBUFS;
845
846 fscache_retrieval_complete(op, 1);
847 _leave(" = %d", ret);
848 return ret;
849 }
850
851 /*
852 * allocate blocks in the cache in which to store a set of pages
853 * - cache withdrawal is prevented by the caller
854 * - returns -EINTR if interrupted
855 * - returns -ENOMEM if ran out of memory
856 * - returns -ENOBUFS if some buffers couldn't be made available
857 * - returns -ENOBUFS if some pages are beyond EOF
858 * - otherwise:
859 * - -ENODATA will be returned
860 * - metadata will be retained for any page marked
861 */
cachefiles_allocate_pages(struct fscache_retrieval * op,struct list_head * pages,unsigned * nr_pages,gfp_t gfp)862 int cachefiles_allocate_pages(struct fscache_retrieval *op,
863 struct list_head *pages,
864 unsigned *nr_pages,
865 gfp_t gfp)
866 {
867 struct cachefiles_object *object;
868 struct cachefiles_cache *cache;
869 struct pagevec pagevec;
870 struct page *page;
871 int ret;
872
873 object = container_of(op->op.object,
874 struct cachefiles_object, fscache);
875 cache = container_of(object->fscache.cache,
876 struct cachefiles_cache, cache);
877
878 _enter("%p,,,%d,", object, *nr_pages);
879
880 ret = cachefiles_has_space(cache, 0, *nr_pages);
881 if (ret == 0) {
882 pagevec_init(&pagevec, 0);
883
884 list_for_each_entry(page, pages, lru) {
885 if (pagevec_add(&pagevec, page) == 0)
886 fscache_mark_pages_cached(op, &pagevec);
887 }
888
889 if (pagevec_count(&pagevec) > 0)
890 fscache_mark_pages_cached(op, &pagevec);
891 ret = -ENODATA;
892 } else {
893 ret = -ENOBUFS;
894 }
895
896 fscache_retrieval_complete(op, *nr_pages);
897 _leave(" = %d", ret);
898 return ret;
899 }
900
901 /*
902 * request a page be stored in the cache
903 * - cache withdrawal is prevented by the caller
904 * - this request may be ignored if there's no cache block available, in which
905 * case -ENOBUFS will be returned
906 * - if the op is in progress, 0 will be returned
907 */
cachefiles_write_page(struct fscache_storage * op,struct page * page)908 int cachefiles_write_page(struct fscache_storage *op, struct page *page)
909 {
910 struct cachefiles_object *object;
911 struct cachefiles_cache *cache;
912 mm_segment_t old_fs;
913 struct file *file;
914 struct path path;
915 loff_t pos, eof;
916 size_t len;
917 void *data;
918 int ret;
919
920 ASSERT(op != NULL);
921 ASSERT(page != NULL);
922
923 object = container_of(op->op.object,
924 struct cachefiles_object, fscache);
925
926 _enter("%p,%p{%lx},,,", object, page, page->index);
927
928 if (!object->backer) {
929 _leave(" = -ENOBUFS");
930 return -ENOBUFS;
931 }
932
933 ASSERT(S_ISREG(object->backer->d_inode->i_mode));
934
935 cache = container_of(object->fscache.cache,
936 struct cachefiles_cache, cache);
937
938 /* write the page to the backing filesystem and let it store it in its
939 * own time */
940 path.mnt = cache->mnt;
941 path.dentry = object->backer;
942 file = dentry_open(&path, O_RDWR | O_LARGEFILE, cache->cache_cred);
943 if (IS_ERR(file)) {
944 ret = PTR_ERR(file);
945 } else {
946 ret = -EIO;
947 if (file->f_op->write) {
948 pos = (loff_t) page->index << PAGE_SHIFT;
949
950 /* we mustn't write more data than we have, so we have
951 * to beware of a partial page at EOF */
952 eof = object->fscache.store_limit_l;
953 len = PAGE_SIZE;
954 if (eof & ~PAGE_MASK) {
955 ASSERTCMP(pos, <, eof);
956 if (eof - pos < PAGE_SIZE) {
957 _debug("cut short %llx to %llx",
958 pos, eof);
959 len = eof - pos;
960 ASSERTCMP(pos + len, ==, eof);
961 }
962 }
963
964 data = kmap(page);
965 file_start_write(file);
966 old_fs = get_fs();
967 set_fs(KERNEL_DS);
968 ret = file->f_op->write(
969 file, (const void __user *) data, len, &pos);
970 set_fs(old_fs);
971 kunmap(page);
972 file_end_write(file);
973 if (ret != len)
974 ret = -EIO;
975 }
976 fput(file);
977 }
978
979 if (ret < 0) {
980 if (ret == -EIO)
981 cachefiles_io_error_obj(
982 object, "Write page to backing file failed");
983 ret = -ENOBUFS;
984 }
985
986 _leave(" = %d", ret);
987 return ret;
988 }
989
990 /*
991 * detach a backing block from a page
992 * - cache withdrawal is prevented by the caller
993 */
cachefiles_uncache_page(struct fscache_object * _object,struct page * page)994 void cachefiles_uncache_page(struct fscache_object *_object, struct page *page)
995 {
996 struct cachefiles_object *object;
997 struct cachefiles_cache *cache;
998
999 object = container_of(_object, struct cachefiles_object, fscache);
1000 cache = container_of(object->fscache.cache,
1001 struct cachefiles_cache, cache);
1002
1003 _enter("%p,{%lu}", object, page->index);
1004
1005 spin_unlock(&object->fscache.cookie->lock);
1006 }
1007