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 kenter("{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 kleave(" = -ENODATA [mapping]");
87 return -ENODATA;
88 }
89
90 backpage2 = find_get_page(bmapping, backpage->index);
91 if (!backpage2) {
92 kleave(" = -ENODATA [gone]");
93 return -ENODATA;
94 }
95
96 if (backpage != backpage2) {
97 put_page(backpage2);
98 kleave(" = -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 kdebug("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 kleave(" = -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 kleave(" = %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 (PageUptodate(monitor->back_page)) {
178 copy_highpage(monitor->netfs_page, monitor->back_page);
179
180 pagevec_add(&pagevec, monitor->netfs_page);
181 fscache_mark_pages_cached(monitor->op, &pagevec);
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 page_cache_release(monitor->back_page);
198
199 fscache_end_io(op, monitor->netfs_page, error);
200 page_cache_release(monitor->netfs_page);
201 fscache_put_retrieval(op);
202 kfree(monitor);
203
204 next:
205 /* let the thread pool have some air occasionally */
206 max--;
207 if (max < 0 || need_resched()) {
208 if (!list_empty(&op->to_do))
209 fscache_enqueue_retrieval(op);
210 _leave(" [maxed out]");
211 return;
212 }
213
214 spin_lock_irq(&object->work_lock);
215 }
216
217 spin_unlock_irq(&object->work_lock);
218 _leave("");
219 }
220
221 /*
222 * read the corresponding page to the given set from the backing file
223 * - an uncertain page is simply discarded, to be tried again another time
224 */
cachefiles_read_backing_file_one(struct cachefiles_object * object,struct fscache_retrieval * op,struct page * netpage,struct pagevec * pagevec)225 static int cachefiles_read_backing_file_one(struct cachefiles_object *object,
226 struct fscache_retrieval *op,
227 struct page *netpage,
228 struct pagevec *pagevec)
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 pagevec_reinit(pagevec);
238
239 _debug("read back %p{%lu,%d}",
240 netpage, netpage->index, page_count(netpage));
241
242 monitor = kzalloc(sizeof(*monitor), GFP_KERNEL);
243 if (!monitor)
244 goto nomem;
245
246 monitor->netfs_page = netpage;
247 monitor->op = fscache_get_retrieval(op);
248
249 init_waitqueue_func_entry(&monitor->monitor, cachefiles_read_waiter);
250
251 /* attempt to get hold of the backing page */
252 bmapping = object->backer->d_inode->i_mapping;
253 newpage = NULL;
254
255 for (;;) {
256 backpage = find_get_page(bmapping, netpage->index);
257 if (backpage)
258 goto backing_page_already_present;
259
260 if (!newpage) {
261 newpage = page_cache_alloc_cold(bmapping);
262 if (!newpage)
263 goto nomem_monitor;
264 }
265
266 ret = add_to_page_cache(newpage, bmapping,
267 netpage->index, GFP_KERNEL);
268 if (ret == 0)
269 goto installed_new_backing_page;
270 if (ret != -EEXIST)
271 goto nomem_page;
272 }
273
274 /* we've installed a new backing page, so now we need to add it
275 * to the LRU list and start it reading */
276 installed_new_backing_page:
277 _debug("- new %p", newpage);
278
279 backpage = newpage;
280 newpage = NULL;
281
282 page_cache_get(backpage);
283 pagevec_add(pagevec, backpage);
284 __pagevec_lru_add_file(pagevec);
285
286 read_backing_page:
287 ret = bmapping->a_ops->readpage(NULL, backpage);
288 if (ret < 0)
289 goto read_error;
290
291 /* set the monitor to transfer the data across */
292 monitor_backing_page:
293 _debug("- monitor add");
294
295 /* install the monitor */
296 page_cache_get(monitor->netfs_page);
297 page_cache_get(backpage);
298 monitor->back_page = backpage;
299 monitor->monitor.private = backpage;
300 add_page_wait_queue(backpage, &monitor->monitor);
301 monitor = NULL;
302
303 /* but the page may have been read before the monitor was installed, so
304 * the monitor may miss the event - so we have to ensure that we do get
305 * one in such a case */
306 if (trylock_page(backpage)) {
307 _debug("jumpstart %p {%lx}", backpage, backpage->flags);
308 unlock_page(backpage);
309 }
310 goto success;
311
312 /* if the backing page is already present, it can be in one of
313 * three states: read in progress, read failed or read okay */
314 backing_page_already_present:
315 _debug("- present");
316
317 if (newpage) {
318 page_cache_release(newpage);
319 newpage = NULL;
320 }
321
322 if (PageError(backpage))
323 goto io_error;
324
325 if (PageUptodate(backpage))
326 goto backing_page_already_uptodate;
327
328 if (!trylock_page(backpage))
329 goto monitor_backing_page;
330 _debug("read %p {%lx}", backpage, backpage->flags);
331 goto read_backing_page;
332
333 /* the backing page is already up to date, attach the netfs
334 * page to the pagecache and LRU and copy the data across */
335 backing_page_already_uptodate:
336 _debug("- uptodate");
337
338 pagevec_add(pagevec, netpage);
339 fscache_mark_pages_cached(op, pagevec);
340
341 copy_highpage(netpage, backpage);
342 fscache_end_io(op, netpage, 0);
343
344 success:
345 _debug("success");
346 ret = 0;
347
348 out:
349 if (backpage)
350 page_cache_release(backpage);
351 if (monitor) {
352 fscache_put_retrieval(monitor->op);
353 kfree(monitor);
354 }
355 _leave(" = %d", ret);
356 return ret;
357
358 read_error:
359 _debug("read error %d", ret);
360 if (ret == -ENOMEM)
361 goto out;
362 io_error:
363 cachefiles_io_error_obj(object, "Page read error on backing file");
364 ret = -ENOBUFS;
365 goto out;
366
367 nomem_page:
368 page_cache_release(newpage);
369 nomem_monitor:
370 fscache_put_retrieval(monitor->op);
371 kfree(monitor);
372 nomem:
373 _leave(" = -ENOMEM");
374 return -ENOMEM;
375 }
376
377 /*
378 * read a page from the cache or allocate a block in which to store it
379 * - cache withdrawal is prevented by the caller
380 * - returns -EINTR if interrupted
381 * - returns -ENOMEM if ran out of memory
382 * - returns -ENOBUFS if no buffers can be made available
383 * - returns -ENOBUFS if page is beyond EOF
384 * - if the page is backed by a block in the cache:
385 * - a read will be started which will call the callback on completion
386 * - 0 will be returned
387 * - else if the page is unbacked:
388 * - the metadata will be retained
389 * - -ENODATA will be returned
390 */
cachefiles_read_or_alloc_page(struct fscache_retrieval * op,struct page * page,gfp_t gfp)391 int cachefiles_read_or_alloc_page(struct fscache_retrieval *op,
392 struct page *page,
393 gfp_t gfp)
394 {
395 struct cachefiles_object *object;
396 struct cachefiles_cache *cache;
397 struct pagevec pagevec;
398 struct inode *inode;
399 sector_t block0, block;
400 unsigned shift;
401 int ret;
402
403 object = container_of(op->op.object,
404 struct cachefiles_object, fscache);
405 cache = container_of(object->fscache.cache,
406 struct cachefiles_cache, cache);
407
408 _enter("{%p},{%lx},,,", object, page->index);
409
410 if (!object->backer)
411 return -ENOBUFS;
412
413 inode = object->backer->d_inode;
414 ASSERT(S_ISREG(inode->i_mode));
415 ASSERT(inode->i_mapping->a_ops->bmap);
416 ASSERT(inode->i_mapping->a_ops->readpages);
417
418 /* calculate the shift required to use bmap */
419 if (inode->i_sb->s_blocksize > PAGE_SIZE)
420 return -ENOBUFS;
421
422 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
423
424 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
425 op->op.flags |= FSCACHE_OP_ASYNC;
426 op->op.processor = cachefiles_read_copier;
427
428 pagevec_init(&pagevec, 0);
429
430 /* we assume the absence or presence of the first block is a good
431 * enough indication for the page as a whole
432 * - TODO: don't use bmap() for this as it is _not_ actually good
433 * enough for this as it doesn't indicate errors, but it's all we've
434 * got for the moment
435 */
436 block0 = page->index;
437 block0 <<= shift;
438
439 block = inode->i_mapping->a_ops->bmap(inode->i_mapping, block0);
440 _debug("%llx -> %llx",
441 (unsigned long long) block0,
442 (unsigned long long) block);
443
444 if (block) {
445 /* submit the apparently valid page to the backing fs to be
446 * read from disk */
447 ret = cachefiles_read_backing_file_one(object, op, page,
448 &pagevec);
449 } else if (cachefiles_has_space(cache, 0, 1) == 0) {
450 /* there's space in the cache we can use */
451 pagevec_add(&pagevec, page);
452 fscache_mark_pages_cached(op, &pagevec);
453 ret = -ENODATA;
454 } else {
455 ret = -ENOBUFS;
456 }
457
458 _leave(" = %d", ret);
459 return ret;
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,struct pagevec * mark_pvec)466 static int cachefiles_read_backing_file(struct cachefiles_object *object,
467 struct fscache_retrieval *op,
468 struct list_head *list,
469 struct pagevec *mark_pvec)
470 {
471 struct cachefiles_one_read *monitor = NULL;
472 struct address_space *bmapping = object->backer->d_inode->i_mapping;
473 struct pagevec lru_pvec;
474 struct page *newpage = NULL, *netpage, *_n, *backpage = NULL;
475 int ret = 0;
476
477 _enter("");
478
479 pagevec_init(&lru_pvec, 0);
480
481 list_for_each_entry_safe(netpage, _n, list, lru) {
482 list_del(&netpage->lru);
483
484 _debug("read back %p{%lu,%d}",
485 netpage, netpage->index, page_count(netpage));
486
487 if (!monitor) {
488 monitor = kzalloc(sizeof(*monitor), GFP_KERNEL);
489 if (!monitor)
490 goto nomem;
491
492 monitor->op = fscache_get_retrieval(op);
493 init_waitqueue_func_entry(&monitor->monitor,
494 cachefiles_read_waiter);
495 }
496
497 for (;;) {
498 backpage = find_get_page(bmapping, netpage->index);
499 if (backpage)
500 goto backing_page_already_present;
501
502 if (!newpage) {
503 newpage = page_cache_alloc_cold(bmapping);
504 if (!newpage)
505 goto nomem;
506 }
507
508 ret = add_to_page_cache(newpage, bmapping,
509 netpage->index, GFP_KERNEL);
510 if (ret == 0)
511 goto installed_new_backing_page;
512 if (ret != -EEXIST)
513 goto nomem;
514 }
515
516 /* we've installed a new backing page, so now we need to add it
517 * to the LRU list and start it reading */
518 installed_new_backing_page:
519 _debug("- new %p", newpage);
520
521 backpage = newpage;
522 newpage = NULL;
523
524 page_cache_get(backpage);
525 if (!pagevec_add(&lru_pvec, backpage))
526 __pagevec_lru_add_file(&lru_pvec);
527
528 reread_backing_page:
529 ret = bmapping->a_ops->readpage(NULL, backpage);
530 if (ret < 0)
531 goto read_error;
532
533 /* add the netfs page to the pagecache and LRU, and set the
534 * monitor to transfer the data across */
535 monitor_backing_page:
536 _debug("- monitor add");
537
538 ret = add_to_page_cache(netpage, op->mapping, netpage->index,
539 GFP_KERNEL);
540 if (ret < 0) {
541 if (ret == -EEXIST) {
542 page_cache_release(netpage);
543 continue;
544 }
545 goto nomem;
546 }
547
548 page_cache_get(netpage);
549 if (!pagevec_add(&lru_pvec, netpage))
550 __pagevec_lru_add_file(&lru_pvec);
551
552 /* install a monitor */
553 page_cache_get(netpage);
554 monitor->netfs_page = netpage;
555
556 page_cache_get(backpage);
557 monitor->back_page = backpage;
558 monitor->monitor.private = backpage;
559 add_page_wait_queue(backpage, &monitor->monitor);
560 monitor = NULL;
561
562 /* but the page may have been read before the monitor was
563 * installed, so the monitor may miss the event - so we have to
564 * ensure that we do get one in such a case */
565 if (trylock_page(backpage)) {
566 _debug("2unlock %p {%lx}", backpage, backpage->flags);
567 unlock_page(backpage);
568 }
569
570 page_cache_release(backpage);
571 backpage = NULL;
572
573 page_cache_release(netpage);
574 netpage = NULL;
575 continue;
576
577 /* if the backing page is already present, it can be in one of
578 * three states: read in progress, read failed or read okay */
579 backing_page_already_present:
580 _debug("- present %p", backpage);
581
582 if (PageError(backpage))
583 goto io_error;
584
585 if (PageUptodate(backpage))
586 goto backing_page_already_uptodate;
587
588 _debug("- not ready %p{%lx}", backpage, backpage->flags);
589
590 if (!trylock_page(backpage))
591 goto monitor_backing_page;
592
593 if (PageError(backpage)) {
594 _debug("error %lx", backpage->flags);
595 unlock_page(backpage);
596 goto io_error;
597 }
598
599 if (PageUptodate(backpage))
600 goto backing_page_already_uptodate_unlock;
601
602 /* we've locked a page that's neither up to date nor erroneous,
603 * so we need to attempt to read it again */
604 goto reread_backing_page;
605
606 /* the backing page is already up to date, attach the netfs
607 * page to the pagecache and LRU and copy the data across */
608 backing_page_already_uptodate_unlock:
609 _debug("uptodate %lx", backpage->flags);
610 unlock_page(backpage);
611 backing_page_already_uptodate:
612 _debug("- uptodate");
613
614 ret = add_to_page_cache(netpage, op->mapping, netpage->index,
615 GFP_KERNEL);
616 if (ret < 0) {
617 if (ret == -EEXIST) {
618 page_cache_release(netpage);
619 continue;
620 }
621 goto nomem;
622 }
623
624 copy_highpage(netpage, backpage);
625
626 page_cache_release(backpage);
627 backpage = NULL;
628
629 if (!pagevec_add(mark_pvec, netpage))
630 fscache_mark_pages_cached(op, mark_pvec);
631
632 page_cache_get(netpage);
633 if (!pagevec_add(&lru_pvec, netpage))
634 __pagevec_lru_add_file(&lru_pvec);
635
636 fscache_end_io(op, netpage, 0);
637 page_cache_release(netpage);
638 netpage = NULL;
639 continue;
640 }
641
642 netpage = NULL;
643
644 _debug("out");
645
646 out:
647 /* tidy up */
648 pagevec_lru_add_file(&lru_pvec);
649
650 if (newpage)
651 page_cache_release(newpage);
652 if (netpage)
653 page_cache_release(netpage);
654 if (backpage)
655 page_cache_release(backpage);
656 if (monitor) {
657 fscache_put_retrieval(op);
658 kfree(monitor);
659 }
660
661 list_for_each_entry_safe(netpage, _n, list, lru) {
662 list_del(&netpage->lru);
663 page_cache_release(netpage);
664 }
665
666 _leave(" = %d", ret);
667 return ret;
668
669 nomem:
670 _debug("nomem");
671 ret = -ENOMEM;
672 goto out;
673
674 read_error:
675 _debug("read error %d", ret);
676 if (ret == -ENOMEM)
677 goto out;
678 io_error:
679 cachefiles_io_error_obj(object, "Page read error on backing file");
680 ret = -ENOBUFS;
681 goto out;
682 }
683
684 /*
685 * read a list of pages from the cache or allocate blocks in which to store
686 * them
687 */
cachefiles_read_or_alloc_pages(struct fscache_retrieval * op,struct list_head * pages,unsigned * nr_pages,gfp_t gfp)688 int cachefiles_read_or_alloc_pages(struct fscache_retrieval *op,
689 struct list_head *pages,
690 unsigned *nr_pages,
691 gfp_t gfp)
692 {
693 struct cachefiles_object *object;
694 struct cachefiles_cache *cache;
695 struct list_head backpages;
696 struct pagevec pagevec;
697 struct inode *inode;
698 struct page *page, *_n;
699 unsigned shift, nrbackpages;
700 int ret, ret2, space;
701
702 object = container_of(op->op.object,
703 struct cachefiles_object, fscache);
704 cache = container_of(object->fscache.cache,
705 struct cachefiles_cache, cache);
706
707 _enter("{OBJ%x,%d},,%d,,",
708 object->fscache.debug_id, atomic_read(&op->op.usage),
709 *nr_pages);
710
711 if (!object->backer)
712 return -ENOBUFS;
713
714 space = 1;
715 if (cachefiles_has_space(cache, 0, *nr_pages) < 0)
716 space = 0;
717
718 inode = object->backer->d_inode;
719 ASSERT(S_ISREG(inode->i_mode));
720 ASSERT(inode->i_mapping->a_ops->bmap);
721 ASSERT(inode->i_mapping->a_ops->readpages);
722
723 /* calculate the shift required to use bmap */
724 if (inode->i_sb->s_blocksize > PAGE_SIZE)
725 return -ENOBUFS;
726
727 shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
728
729 pagevec_init(&pagevec, 0);
730
731 op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
732 op->op.flags |= FSCACHE_OP_ASYNC;
733 op->op.processor = cachefiles_read_copier;
734
735 INIT_LIST_HEAD(&backpages);
736 nrbackpages = 0;
737
738 ret = space ? -ENODATA : -ENOBUFS;
739 list_for_each_entry_safe(page, _n, pages, lru) {
740 sector_t block0, block;
741
742 /* we assume the absence or presence of the first block is a
743 * good enough indication for the page as a whole
744 * - TODO: don't use bmap() for this as it is _not_ actually
745 * good enough for this as it doesn't indicate errors, but
746 * it's all we've got for the moment
747 */
748 block0 = page->index;
749 block0 <<= shift;
750
751 block = inode->i_mapping->a_ops->bmap(inode->i_mapping,
752 block0);
753 _debug("%llx -> %llx",
754 (unsigned long long) block0,
755 (unsigned long long) block);
756
757 if (block) {
758 /* we have data - add it to the list to give to the
759 * backing fs */
760 list_move(&page->lru, &backpages);
761 (*nr_pages)--;
762 nrbackpages++;
763 } else if (space && pagevec_add(&pagevec, page) == 0) {
764 fscache_mark_pages_cached(op, &pagevec);
765 ret = -ENODATA;
766 }
767 }
768
769 if (pagevec_count(&pagevec) > 0)
770 fscache_mark_pages_cached(op, &pagevec);
771
772 if (list_empty(pages))
773 ret = 0;
774
775 /* submit the apparently valid pages to the backing fs to be read from
776 * disk */
777 if (nrbackpages > 0) {
778 ret2 = cachefiles_read_backing_file(object, op, &backpages,
779 &pagevec);
780 if (ret2 == -ENOMEM || ret2 == -EINTR)
781 ret = ret2;
782 }
783
784 if (pagevec_count(&pagevec) > 0)
785 fscache_mark_pages_cached(op, &pagevec);
786
787 _leave(" = %d [nr=%u%s]",
788 ret, *nr_pages, list_empty(pages) ? " empty" : "");
789 return ret;
790 }
791
792 /*
793 * allocate a block in the cache in which to store a page
794 * - cache withdrawal is prevented by the caller
795 * - returns -EINTR if interrupted
796 * - returns -ENOMEM if ran out of memory
797 * - returns -ENOBUFS if no buffers can be made available
798 * - returns -ENOBUFS if page is beyond EOF
799 * - otherwise:
800 * - the metadata will be retained
801 * - 0 will be returned
802 */
cachefiles_allocate_page(struct fscache_retrieval * op,struct page * page,gfp_t gfp)803 int cachefiles_allocate_page(struct fscache_retrieval *op,
804 struct page *page,
805 gfp_t gfp)
806 {
807 struct cachefiles_object *object;
808 struct cachefiles_cache *cache;
809 struct pagevec pagevec;
810 int ret;
811
812 object = container_of(op->op.object,
813 struct cachefiles_object, fscache);
814 cache = container_of(object->fscache.cache,
815 struct cachefiles_cache, cache);
816
817 _enter("%p,{%lx},", object, page->index);
818
819 ret = cachefiles_has_space(cache, 0, 1);
820 if (ret == 0) {
821 pagevec_init(&pagevec, 0);
822 pagevec_add(&pagevec, page);
823 fscache_mark_pages_cached(op, &pagevec);
824 } else {
825 ret = -ENOBUFS;
826 }
827
828 _leave(" = %d", ret);
829 return ret;
830 }
831
832 /*
833 * allocate blocks in the cache in which to store a set of pages
834 * - cache withdrawal is prevented by the caller
835 * - returns -EINTR if interrupted
836 * - returns -ENOMEM if ran out of memory
837 * - returns -ENOBUFS if some buffers couldn't be made available
838 * - returns -ENOBUFS if some pages are beyond EOF
839 * - otherwise:
840 * - -ENODATA will be returned
841 * - metadata will be retained for any page marked
842 */
cachefiles_allocate_pages(struct fscache_retrieval * op,struct list_head * pages,unsigned * nr_pages,gfp_t gfp)843 int cachefiles_allocate_pages(struct fscache_retrieval *op,
844 struct list_head *pages,
845 unsigned *nr_pages,
846 gfp_t gfp)
847 {
848 struct cachefiles_object *object;
849 struct cachefiles_cache *cache;
850 struct pagevec pagevec;
851 struct page *page;
852 int ret;
853
854 object = container_of(op->op.object,
855 struct cachefiles_object, fscache);
856 cache = container_of(object->fscache.cache,
857 struct cachefiles_cache, cache);
858
859 _enter("%p,,,%d,", object, *nr_pages);
860
861 ret = cachefiles_has_space(cache, 0, *nr_pages);
862 if (ret == 0) {
863 pagevec_init(&pagevec, 0);
864
865 list_for_each_entry(page, pages, lru) {
866 if (pagevec_add(&pagevec, page) == 0)
867 fscache_mark_pages_cached(op, &pagevec);
868 }
869
870 if (pagevec_count(&pagevec) > 0)
871 fscache_mark_pages_cached(op, &pagevec);
872 ret = -ENODATA;
873 } else {
874 ret = -ENOBUFS;
875 }
876
877 _leave(" = %d", ret);
878 return ret;
879 }
880
881 /*
882 * request a page be stored in the cache
883 * - cache withdrawal is prevented by the caller
884 * - this request may be ignored if there's no cache block available, in which
885 * case -ENOBUFS will be returned
886 * - if the op is in progress, 0 will be returned
887 */
cachefiles_write_page(struct fscache_storage * op,struct page * page)888 int cachefiles_write_page(struct fscache_storage *op, struct page *page)
889 {
890 struct cachefiles_object *object;
891 struct cachefiles_cache *cache;
892 mm_segment_t old_fs;
893 struct file *file;
894 loff_t pos, eof;
895 size_t len;
896 void *data;
897 int ret;
898
899 ASSERT(op != NULL);
900 ASSERT(page != NULL);
901
902 object = container_of(op->op.object,
903 struct cachefiles_object, fscache);
904
905 _enter("%p,%p{%lx},,,", object, page, page->index);
906
907 if (!object->backer) {
908 _leave(" = -ENOBUFS");
909 return -ENOBUFS;
910 }
911
912 ASSERT(S_ISREG(object->backer->d_inode->i_mode));
913
914 cache = container_of(object->fscache.cache,
915 struct cachefiles_cache, cache);
916
917 /* write the page to the backing filesystem and let it store it in its
918 * own time */
919 dget(object->backer);
920 mntget(cache->mnt);
921 file = dentry_open(object->backer, cache->mnt, O_RDWR | O_LARGEFILE,
922 cache->cache_cred);
923 if (IS_ERR(file)) {
924 ret = PTR_ERR(file);
925 } else {
926 ret = -EIO;
927 if (file->f_op->write) {
928 pos = (loff_t) page->index << PAGE_SHIFT;
929
930 /* we mustn't write more data than we have, so we have
931 * to beware of a partial page at EOF */
932 eof = object->fscache.store_limit_l;
933 len = PAGE_SIZE;
934 if (eof & ~PAGE_MASK) {
935 ASSERTCMP(pos, <, eof);
936 if (eof - pos < PAGE_SIZE) {
937 _debug("cut short %llx to %llx",
938 pos, eof);
939 len = eof - pos;
940 ASSERTCMP(pos + len, ==, eof);
941 }
942 }
943
944 data = kmap(page);
945 old_fs = get_fs();
946 set_fs(KERNEL_DS);
947 ret = file->f_op->write(
948 file, (const void __user *) data, len, &pos);
949 set_fs(old_fs);
950 kunmap(page);
951 if (ret != len)
952 ret = -EIO;
953 }
954 fput(file);
955 }
956
957 if (ret < 0) {
958 if (ret == -EIO)
959 cachefiles_io_error_obj(
960 object, "Write page to backing file failed");
961 ret = -ENOBUFS;
962 }
963
964 _leave(" = %d", ret);
965 return ret;
966 }
967
968 /*
969 * detach a backing block from a page
970 * - cache withdrawal is prevented by the caller
971 */
cachefiles_uncache_page(struct fscache_object * _object,struct page * page)972 void cachefiles_uncache_page(struct fscache_object *_object, struct page *page)
973 {
974 struct cachefiles_object *object;
975 struct cachefiles_cache *cache;
976
977 object = container_of(_object, struct cachefiles_object, fscache);
978 cache = container_of(object->fscache.cache,
979 struct cachefiles_cache, cache);
980
981 _enter("%p,{%lu}", object, page->index);
982
983 spin_unlock(&object->fscache.cookie->lock);
984 }
985