GNU Linux-libre 4.19.211-gnu1
[releases.git] / fs / fscache / page.c
1 /* Cache page management and data I/O routines
2  *
3  * Copyright (C) 2004-2008 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 License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11
12 #define FSCACHE_DEBUG_LEVEL PAGE
13 #include <linux/module.h>
14 #include <linux/fscache-cache.h>
15 #include <linux/buffer_head.h>
16 #include <linux/pagevec.h>
17 #include <linux/slab.h>
18 #include "internal.h"
19
20 /*
21  * check to see if a page is being written to the cache
22  */
23 bool __fscache_check_page_write(struct fscache_cookie *cookie, struct page *page)
24 {
25         void *val;
26
27         rcu_read_lock();
28         val = radix_tree_lookup(&cookie->stores, page->index);
29         rcu_read_unlock();
30         trace_fscache_check_page(cookie, page, val, 0);
31
32         return val != NULL;
33 }
34 EXPORT_SYMBOL(__fscache_check_page_write);
35
36 /*
37  * wait for a page to finish being written to the cache
38  */
39 void __fscache_wait_on_page_write(struct fscache_cookie *cookie, struct page *page)
40 {
41         wait_queue_head_t *wq = bit_waitqueue(&cookie->flags, 0);
42
43         trace_fscache_page(cookie, page, fscache_page_write_wait);
44
45         wait_event(*wq, !__fscache_check_page_write(cookie, page));
46 }
47 EXPORT_SYMBOL(__fscache_wait_on_page_write);
48
49 /*
50  * wait for a page to finish being written to the cache. Put a timeout here
51  * since we might be called recursively via parent fs.
52  */
53 static
54 bool release_page_wait_timeout(struct fscache_cookie *cookie, struct page *page)
55 {
56         wait_queue_head_t *wq = bit_waitqueue(&cookie->flags, 0);
57
58         return wait_event_timeout(*wq, !__fscache_check_page_write(cookie, page),
59                                   HZ);
60 }
61
62 /*
63  * decide whether a page can be released, possibly by cancelling a store to it
64  * - we're allowed to sleep if __GFP_DIRECT_RECLAIM is flagged
65  */
66 bool __fscache_maybe_release_page(struct fscache_cookie *cookie,
67                                   struct page *page,
68                                   gfp_t gfp)
69 {
70         struct page *xpage;
71         void *val;
72
73         _enter("%p,%p,%x", cookie, page, gfp);
74
75         trace_fscache_page(cookie, page, fscache_page_maybe_release);
76
77 try_again:
78         rcu_read_lock();
79         val = radix_tree_lookup(&cookie->stores, page->index);
80         if (!val) {
81                 rcu_read_unlock();
82                 fscache_stat(&fscache_n_store_vmscan_not_storing);
83                 __fscache_uncache_page(cookie, page);
84                 return true;
85         }
86
87         /* see if the page is actually undergoing storage - if so we can't get
88          * rid of it till the cache has finished with it */
89         if (radix_tree_tag_get(&cookie->stores, page->index,
90                                FSCACHE_COOKIE_STORING_TAG)) {
91                 rcu_read_unlock();
92                 goto page_busy;
93         }
94
95         /* the page is pending storage, so we attempt to cancel the store and
96          * discard the store request so that the page can be reclaimed */
97         spin_lock(&cookie->stores_lock);
98         rcu_read_unlock();
99
100         if (radix_tree_tag_get(&cookie->stores, page->index,
101                                FSCACHE_COOKIE_STORING_TAG)) {
102                 /* the page started to undergo storage whilst we were looking,
103                  * so now we can only wait or return */
104                 spin_unlock(&cookie->stores_lock);
105                 goto page_busy;
106         }
107
108         xpage = radix_tree_delete(&cookie->stores, page->index);
109         trace_fscache_page(cookie, page, fscache_page_radix_delete);
110         spin_unlock(&cookie->stores_lock);
111
112         if (xpage) {
113                 fscache_stat(&fscache_n_store_vmscan_cancelled);
114                 fscache_stat(&fscache_n_store_radix_deletes);
115                 ASSERTCMP(xpage, ==, page);
116         } else {
117                 fscache_stat(&fscache_n_store_vmscan_gone);
118         }
119
120         wake_up_bit(&cookie->flags, 0);
121         trace_fscache_wake_cookie(cookie);
122         if (xpage)
123                 put_page(xpage);
124         __fscache_uncache_page(cookie, page);
125         return true;
126
127 page_busy:
128         /* We will wait here if we're allowed to, but that could deadlock the
129          * allocator as the work threads writing to the cache may all end up
130          * sleeping on memory allocation, so we may need to impose a timeout
131          * too. */
132         if (!(gfp & __GFP_DIRECT_RECLAIM) || !(gfp & __GFP_FS)) {
133                 fscache_stat(&fscache_n_store_vmscan_busy);
134                 return false;
135         }
136
137         fscache_stat(&fscache_n_store_vmscan_wait);
138         if (!release_page_wait_timeout(cookie, page))
139                 _debug("fscache writeout timeout page: %p{%lx}",
140                         page, page->index);
141
142         gfp &= ~__GFP_DIRECT_RECLAIM;
143         goto try_again;
144 }
145 EXPORT_SYMBOL(__fscache_maybe_release_page);
146
147 /*
148  * note that a page has finished being written to the cache
149  */
150 static void fscache_end_page_write(struct fscache_object *object,
151                                    struct page *page)
152 {
153         struct fscache_cookie *cookie;
154         struct page *xpage = NULL, *val;
155
156         spin_lock(&object->lock);
157         cookie = object->cookie;
158         if (cookie) {
159                 /* delete the page from the tree if it is now no longer
160                  * pending */
161                 spin_lock(&cookie->stores_lock);
162                 radix_tree_tag_clear(&cookie->stores, page->index,
163                                      FSCACHE_COOKIE_STORING_TAG);
164                 trace_fscache_page(cookie, page, fscache_page_radix_clear_store);
165                 if (!radix_tree_tag_get(&cookie->stores, page->index,
166                                         FSCACHE_COOKIE_PENDING_TAG)) {
167                         fscache_stat(&fscache_n_store_radix_deletes);
168                         xpage = radix_tree_delete(&cookie->stores, page->index);
169                         trace_fscache_page(cookie, page, fscache_page_radix_delete);
170                         trace_fscache_page(cookie, page, fscache_page_write_end);
171
172                         val = radix_tree_lookup(&cookie->stores, page->index);
173                         trace_fscache_check_page(cookie, page, val, 1);
174                 } else {
175                         trace_fscache_page(cookie, page, fscache_page_write_end_pend);
176                 }
177                 spin_unlock(&cookie->stores_lock);
178                 wake_up_bit(&cookie->flags, 0);
179                 trace_fscache_wake_cookie(cookie);
180         } else {
181                 trace_fscache_page(cookie, page, fscache_page_write_end_noc);
182         }
183         spin_unlock(&object->lock);
184         if (xpage)
185                 put_page(xpage);
186 }
187
188 /*
189  * actually apply the changed attributes to a cache object
190  */
191 static void fscache_attr_changed_op(struct fscache_operation *op)
192 {
193         struct fscache_object *object = op->object;
194         int ret;
195
196         _enter("{OBJ%x OP%x}", object->debug_id, op->debug_id);
197
198         fscache_stat(&fscache_n_attr_changed_calls);
199
200         if (fscache_object_is_active(object)) {
201                 fscache_stat(&fscache_n_cop_attr_changed);
202                 ret = object->cache->ops->attr_changed(object);
203                 fscache_stat_d(&fscache_n_cop_attr_changed);
204                 if (ret < 0)
205                         fscache_abort_object(object);
206                 fscache_op_complete(op, ret < 0);
207         } else {
208                 fscache_op_complete(op, true);
209         }
210
211         _leave("");
212 }
213
214 /*
215  * notification that the attributes on an object have changed
216  */
217 int __fscache_attr_changed(struct fscache_cookie *cookie)
218 {
219         struct fscache_operation *op;
220         struct fscache_object *object;
221         bool wake_cookie = false;
222
223         _enter("%p", cookie);
224
225         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
226
227         fscache_stat(&fscache_n_attr_changed);
228
229         op = kzalloc(sizeof(*op), GFP_KERNEL);
230         if (!op) {
231                 fscache_stat(&fscache_n_attr_changed_nomem);
232                 _leave(" = -ENOMEM");
233                 return -ENOMEM;
234         }
235
236         fscache_operation_init(cookie, op, fscache_attr_changed_op, NULL, NULL);
237         trace_fscache_page_op(cookie, NULL, op, fscache_page_op_attr_changed);
238         op->flags = FSCACHE_OP_ASYNC |
239                 (1 << FSCACHE_OP_EXCLUSIVE) |
240                 (1 << FSCACHE_OP_UNUSE_COOKIE);
241
242         spin_lock(&cookie->lock);
243
244         if (!fscache_cookie_enabled(cookie) ||
245             hlist_empty(&cookie->backing_objects))
246                 goto nobufs;
247         object = hlist_entry(cookie->backing_objects.first,
248                              struct fscache_object, cookie_link);
249
250         __fscache_use_cookie(cookie);
251         if (fscache_submit_exclusive_op(object, op) < 0)
252                 goto nobufs_dec;
253         spin_unlock(&cookie->lock);
254         fscache_stat(&fscache_n_attr_changed_ok);
255         fscache_put_operation(op);
256         _leave(" = 0");
257         return 0;
258
259 nobufs_dec:
260         wake_cookie = __fscache_unuse_cookie(cookie);
261 nobufs:
262         spin_unlock(&cookie->lock);
263         fscache_put_operation(op);
264         if (wake_cookie)
265                 __fscache_wake_unused_cookie(cookie);
266         fscache_stat(&fscache_n_attr_changed_nobufs);
267         _leave(" = %d", -ENOBUFS);
268         return -ENOBUFS;
269 }
270 EXPORT_SYMBOL(__fscache_attr_changed);
271
272 /*
273  * Handle cancellation of a pending retrieval op
274  */
275 static void fscache_do_cancel_retrieval(struct fscache_operation *_op)
276 {
277         struct fscache_retrieval *op =
278                 container_of(_op, struct fscache_retrieval, op);
279
280         atomic_set(&op->n_pages, 0);
281 }
282
283 /*
284  * release a retrieval op reference
285  */
286 static void fscache_release_retrieval_op(struct fscache_operation *_op)
287 {
288         struct fscache_retrieval *op =
289                 container_of(_op, struct fscache_retrieval, op);
290
291         _enter("{OP%x}", op->op.debug_id);
292
293         ASSERTIFCMP(op->op.state != FSCACHE_OP_ST_INITIALISED,
294                     atomic_read(&op->n_pages), ==, 0);
295
296         fscache_hist(fscache_retrieval_histogram, op->start_time);
297         if (op->context)
298                 fscache_put_context(op->cookie, op->context);
299
300         _leave("");
301 }
302
303 /*
304  * allocate a retrieval op
305  */
306 static struct fscache_retrieval *fscache_alloc_retrieval(
307         struct fscache_cookie *cookie,
308         struct address_space *mapping,
309         fscache_rw_complete_t end_io_func,
310         void *context)
311 {
312         struct fscache_retrieval *op;
313
314         /* allocate a retrieval operation and attempt to submit it */
315         op = kzalloc(sizeof(*op), GFP_NOIO);
316         if (!op) {
317                 fscache_stat(&fscache_n_retrievals_nomem);
318                 return NULL;
319         }
320
321         fscache_operation_init(cookie, &op->op, NULL,
322                                fscache_do_cancel_retrieval,
323                                fscache_release_retrieval_op);
324         op->op.flags    = FSCACHE_OP_MYTHREAD |
325                 (1UL << FSCACHE_OP_WAITING) |
326                 (1UL << FSCACHE_OP_UNUSE_COOKIE);
327         op->cookie      = cookie;
328         op->mapping     = mapping;
329         op->end_io_func = end_io_func;
330         op->context     = context;
331         op->start_time  = jiffies;
332         INIT_LIST_HEAD(&op->to_do);
333
334         /* Pin the netfs read context in case we need to do the actual netfs
335          * read because we've encountered a cache read failure.
336          */
337         if (context)
338                 fscache_get_context(op->cookie, context);
339         return op;
340 }
341
342 /*
343  * wait for a deferred lookup to complete
344  */
345 int fscache_wait_for_deferred_lookup(struct fscache_cookie *cookie)
346 {
347         unsigned long jif;
348
349         _enter("");
350
351         if (!test_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags)) {
352                 _leave(" = 0 [imm]");
353                 return 0;
354         }
355
356         fscache_stat(&fscache_n_retrievals_wait);
357
358         jif = jiffies;
359         if (wait_on_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP,
360                         TASK_INTERRUPTIBLE) != 0) {
361                 fscache_stat(&fscache_n_retrievals_intr);
362                 _leave(" = -ERESTARTSYS");
363                 return -ERESTARTSYS;
364         }
365
366         ASSERT(!test_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags));
367
368         smp_rmb();
369         fscache_hist(fscache_retrieval_delay_histogram, jif);
370         _leave(" = 0 [dly]");
371         return 0;
372 }
373
374 /*
375  * wait for an object to become active (or dead)
376  */
377 int fscache_wait_for_operation_activation(struct fscache_object *object,
378                                           struct fscache_operation *op,
379                                           atomic_t *stat_op_waits,
380                                           atomic_t *stat_object_dead)
381 {
382         int ret;
383
384         if (!test_bit(FSCACHE_OP_WAITING, &op->flags))
385                 goto check_if_dead;
386
387         _debug(">>> WT");
388         if (stat_op_waits)
389                 fscache_stat(stat_op_waits);
390         if (wait_on_bit(&op->flags, FSCACHE_OP_WAITING,
391                         TASK_INTERRUPTIBLE) != 0) {
392                 trace_fscache_op(object->cookie, op, fscache_op_signal);
393                 ret = fscache_cancel_op(op, false);
394                 if (ret == 0)
395                         return -ERESTARTSYS;
396
397                 /* it's been removed from the pending queue by another party,
398                  * so we should get to run shortly */
399                 wait_on_bit(&op->flags, FSCACHE_OP_WAITING,
400                             TASK_UNINTERRUPTIBLE);
401         }
402         _debug("<<< GO");
403
404 check_if_dead:
405         if (op->state == FSCACHE_OP_ST_CANCELLED) {
406                 if (stat_object_dead)
407                         fscache_stat(stat_object_dead);
408                 _leave(" = -ENOBUFS [cancelled]");
409                 return -ENOBUFS;
410         }
411         if (unlikely(fscache_object_is_dying(object) ||
412                      fscache_cache_is_broken(object))) {
413                 enum fscache_operation_state state = op->state;
414                 trace_fscache_op(object->cookie, op, fscache_op_signal);
415                 fscache_cancel_op(op, true);
416                 if (stat_object_dead)
417                         fscache_stat(stat_object_dead);
418                 _leave(" = -ENOBUFS [obj dead %d]", state);
419                 return -ENOBUFS;
420         }
421         return 0;
422 }
423
424 /*
425  * read a page from the cache or allocate a block in which to store it
426  * - we return:
427  *   -ENOMEM    - out of memory, nothing done
428  *   -ERESTARTSYS - interrupted
429  *   -ENOBUFS   - no backing object available in which to cache the block
430  *   -ENODATA   - no data available in the backing object for this block
431  *   0          - dispatched a read - it'll call end_io_func() when finished
432  */
433 int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
434                                  struct page *page,
435                                  fscache_rw_complete_t end_io_func,
436                                  void *context,
437                                  gfp_t gfp)
438 {
439         struct fscache_retrieval *op;
440         struct fscache_object *object;
441         bool wake_cookie = false;
442         int ret;
443
444         _enter("%p,%p,,,", cookie, page);
445
446         fscache_stat(&fscache_n_retrievals);
447
448         if (hlist_empty(&cookie->backing_objects))
449                 goto nobufs;
450
451         if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
452                 _leave(" = -ENOBUFS [invalidating]");
453                 return -ENOBUFS;
454         }
455
456         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
457         ASSERTCMP(page, !=, NULL);
458
459         if (fscache_wait_for_deferred_lookup(cookie) < 0)
460                 return -ERESTARTSYS;
461
462         op = fscache_alloc_retrieval(cookie, page->mapping,
463                                      end_io_func, context);
464         if (!op) {
465                 _leave(" = -ENOMEM");
466                 return -ENOMEM;
467         }
468         atomic_set(&op->n_pages, 1);
469         trace_fscache_page_op(cookie, page, &op->op, fscache_page_op_retr_one);
470
471         spin_lock(&cookie->lock);
472
473         if (!fscache_cookie_enabled(cookie) ||
474             hlist_empty(&cookie->backing_objects))
475                 goto nobufs_unlock;
476         object = hlist_entry(cookie->backing_objects.first,
477                              struct fscache_object, cookie_link);
478
479         ASSERT(test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags));
480
481         __fscache_use_cookie(cookie);
482         atomic_inc(&object->n_reads);
483         __set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
484
485         if (fscache_submit_op(object, &op->op) < 0)
486                 goto nobufs_unlock_dec;
487         spin_unlock(&cookie->lock);
488
489         fscache_stat(&fscache_n_retrieval_ops);
490
491         /* we wait for the operation to become active, and then process it
492          * *here*, in this thread, and not in the thread pool */
493         ret = fscache_wait_for_operation_activation(
494                 object, &op->op,
495                 __fscache_stat(&fscache_n_retrieval_op_waits),
496                 __fscache_stat(&fscache_n_retrievals_object_dead));
497         if (ret < 0)
498                 goto error;
499
500         /* ask the cache to honour the operation */
501         if (test_bit(FSCACHE_COOKIE_NO_DATA_YET, &object->cookie->flags)) {
502                 fscache_stat(&fscache_n_cop_allocate_page);
503                 ret = object->cache->ops->allocate_page(op, page, gfp);
504                 fscache_stat_d(&fscache_n_cop_allocate_page);
505                 if (ret == 0)
506                         ret = -ENODATA;
507         } else {
508                 fscache_stat(&fscache_n_cop_read_or_alloc_page);
509                 ret = object->cache->ops->read_or_alloc_page(op, page, gfp);
510                 fscache_stat_d(&fscache_n_cop_read_or_alloc_page);
511         }
512
513 error:
514         if (ret == -ENOMEM)
515                 fscache_stat(&fscache_n_retrievals_nomem);
516         else if (ret == -ERESTARTSYS)
517                 fscache_stat(&fscache_n_retrievals_intr);
518         else if (ret == -ENODATA)
519                 fscache_stat(&fscache_n_retrievals_nodata);
520         else if (ret < 0)
521                 fscache_stat(&fscache_n_retrievals_nobufs);
522         else
523                 fscache_stat(&fscache_n_retrievals_ok);
524
525         fscache_put_retrieval(op);
526         _leave(" = %d", ret);
527         return ret;
528
529 nobufs_unlock_dec:
530         atomic_dec(&object->n_reads);
531         wake_cookie = __fscache_unuse_cookie(cookie);
532 nobufs_unlock:
533         spin_unlock(&cookie->lock);
534         if (wake_cookie)
535                 __fscache_wake_unused_cookie(cookie);
536         fscache_put_retrieval(op);
537 nobufs:
538         fscache_stat(&fscache_n_retrievals_nobufs);
539         _leave(" = -ENOBUFS");
540         return -ENOBUFS;
541 }
542 EXPORT_SYMBOL(__fscache_read_or_alloc_page);
543
544 /*
545  * read a list of page from the cache or allocate a block in which to store
546  * them
547  * - we return:
548  *   -ENOMEM    - out of memory, some pages may be being read
549  *   -ERESTARTSYS - interrupted, some pages may be being read
550  *   -ENOBUFS   - no backing object or space available in which to cache any
551  *                pages not being read
552  *   -ENODATA   - no data available in the backing object for some or all of
553  *                the pages
554  *   0          - dispatched a read on all pages
555  *
556  * end_io_func() will be called for each page read from the cache as it is
557  * finishes being read
558  *
559  * any pages for which a read is dispatched will be removed from pages and
560  * nr_pages
561  */
562 int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
563                                   struct address_space *mapping,
564                                   struct list_head *pages,
565                                   unsigned *nr_pages,
566                                   fscache_rw_complete_t end_io_func,
567                                   void *context,
568                                   gfp_t gfp)
569 {
570         struct fscache_retrieval *op;
571         struct fscache_object *object;
572         bool wake_cookie = false;
573         int ret;
574
575         _enter("%p,,%d,,,", cookie, *nr_pages);
576
577         fscache_stat(&fscache_n_retrievals);
578
579         if (hlist_empty(&cookie->backing_objects))
580                 goto nobufs;
581
582         if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
583                 _leave(" = -ENOBUFS [invalidating]");
584                 return -ENOBUFS;
585         }
586
587         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
588         ASSERTCMP(*nr_pages, >, 0);
589         ASSERT(!list_empty(pages));
590
591         if (fscache_wait_for_deferred_lookup(cookie) < 0)
592                 return -ERESTARTSYS;
593
594         op = fscache_alloc_retrieval(cookie, mapping, end_io_func, context);
595         if (!op)
596                 return -ENOMEM;
597         atomic_set(&op->n_pages, *nr_pages);
598         trace_fscache_page_op(cookie, NULL, &op->op, fscache_page_op_retr_multi);
599
600         spin_lock(&cookie->lock);
601
602         if (!fscache_cookie_enabled(cookie) ||
603             hlist_empty(&cookie->backing_objects))
604                 goto nobufs_unlock;
605         object = hlist_entry(cookie->backing_objects.first,
606                              struct fscache_object, cookie_link);
607
608         __fscache_use_cookie(cookie);
609         atomic_inc(&object->n_reads);
610         __set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
611
612         if (fscache_submit_op(object, &op->op) < 0)
613                 goto nobufs_unlock_dec;
614         spin_unlock(&cookie->lock);
615
616         fscache_stat(&fscache_n_retrieval_ops);
617
618         /* we wait for the operation to become active, and then process it
619          * *here*, in this thread, and not in the thread pool */
620         ret = fscache_wait_for_operation_activation(
621                 object, &op->op,
622                 __fscache_stat(&fscache_n_retrieval_op_waits),
623                 __fscache_stat(&fscache_n_retrievals_object_dead));
624         if (ret < 0)
625                 goto error;
626
627         /* ask the cache to honour the operation */
628         if (test_bit(FSCACHE_COOKIE_NO_DATA_YET, &object->cookie->flags)) {
629                 fscache_stat(&fscache_n_cop_allocate_pages);
630                 ret = object->cache->ops->allocate_pages(
631                         op, pages, nr_pages, gfp);
632                 fscache_stat_d(&fscache_n_cop_allocate_pages);
633         } else {
634                 fscache_stat(&fscache_n_cop_read_or_alloc_pages);
635                 ret = object->cache->ops->read_or_alloc_pages(
636                         op, pages, nr_pages, gfp);
637                 fscache_stat_d(&fscache_n_cop_read_or_alloc_pages);
638         }
639
640 error:
641         if (ret == -ENOMEM)
642                 fscache_stat(&fscache_n_retrievals_nomem);
643         else if (ret == -ERESTARTSYS)
644                 fscache_stat(&fscache_n_retrievals_intr);
645         else if (ret == -ENODATA)
646                 fscache_stat(&fscache_n_retrievals_nodata);
647         else if (ret < 0)
648                 fscache_stat(&fscache_n_retrievals_nobufs);
649         else
650                 fscache_stat(&fscache_n_retrievals_ok);
651
652         fscache_put_retrieval(op);
653         _leave(" = %d", ret);
654         return ret;
655
656 nobufs_unlock_dec:
657         atomic_dec(&object->n_reads);
658         wake_cookie = __fscache_unuse_cookie(cookie);
659 nobufs_unlock:
660         spin_unlock(&cookie->lock);
661         fscache_put_retrieval(op);
662         if (wake_cookie)
663                 __fscache_wake_unused_cookie(cookie);
664 nobufs:
665         fscache_stat(&fscache_n_retrievals_nobufs);
666         _leave(" = -ENOBUFS");
667         return -ENOBUFS;
668 }
669 EXPORT_SYMBOL(__fscache_read_or_alloc_pages);
670
671 /*
672  * allocate a block in the cache on which to store a page
673  * - we return:
674  *   -ENOMEM    - out of memory, nothing done
675  *   -ERESTARTSYS - interrupted
676  *   -ENOBUFS   - no backing object available in which to cache the block
677  *   0          - block allocated
678  */
679 int __fscache_alloc_page(struct fscache_cookie *cookie,
680                          struct page *page,
681                          gfp_t gfp)
682 {
683         struct fscache_retrieval *op;
684         struct fscache_object *object;
685         bool wake_cookie = false;
686         int ret;
687
688         _enter("%p,%p,,,", cookie, page);
689
690         fscache_stat(&fscache_n_allocs);
691
692         if (hlist_empty(&cookie->backing_objects))
693                 goto nobufs;
694
695         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
696         ASSERTCMP(page, !=, NULL);
697
698         if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
699                 _leave(" = -ENOBUFS [invalidating]");
700                 return -ENOBUFS;
701         }
702
703         if (fscache_wait_for_deferred_lookup(cookie) < 0)
704                 return -ERESTARTSYS;
705
706         op = fscache_alloc_retrieval(cookie, page->mapping, NULL, NULL);
707         if (!op)
708                 return -ENOMEM;
709         atomic_set(&op->n_pages, 1);
710         trace_fscache_page_op(cookie, page, &op->op, fscache_page_op_alloc_one);
711
712         spin_lock(&cookie->lock);
713
714         if (!fscache_cookie_enabled(cookie) ||
715             hlist_empty(&cookie->backing_objects))
716                 goto nobufs_unlock;
717         object = hlist_entry(cookie->backing_objects.first,
718                              struct fscache_object, cookie_link);
719
720         __fscache_use_cookie(cookie);
721         if (fscache_submit_op(object, &op->op) < 0)
722                 goto nobufs_unlock_dec;
723         spin_unlock(&cookie->lock);
724
725         fscache_stat(&fscache_n_alloc_ops);
726
727         ret = fscache_wait_for_operation_activation(
728                 object, &op->op,
729                 __fscache_stat(&fscache_n_alloc_op_waits),
730                 __fscache_stat(&fscache_n_allocs_object_dead));
731         if (ret < 0)
732                 goto error;
733
734         /* ask the cache to honour the operation */
735         fscache_stat(&fscache_n_cop_allocate_page);
736         ret = object->cache->ops->allocate_page(op, page, gfp);
737         fscache_stat_d(&fscache_n_cop_allocate_page);
738
739 error:
740         if (ret == -ERESTARTSYS)
741                 fscache_stat(&fscache_n_allocs_intr);
742         else if (ret < 0)
743                 fscache_stat(&fscache_n_allocs_nobufs);
744         else
745                 fscache_stat(&fscache_n_allocs_ok);
746
747         fscache_put_retrieval(op);
748         _leave(" = %d", ret);
749         return ret;
750
751 nobufs_unlock_dec:
752         wake_cookie = __fscache_unuse_cookie(cookie);
753 nobufs_unlock:
754         spin_unlock(&cookie->lock);
755         fscache_put_retrieval(op);
756         if (wake_cookie)
757                 __fscache_wake_unused_cookie(cookie);
758 nobufs:
759         fscache_stat(&fscache_n_allocs_nobufs);
760         _leave(" = -ENOBUFS");
761         return -ENOBUFS;
762 }
763 EXPORT_SYMBOL(__fscache_alloc_page);
764
765 /*
766  * Unmark pages allocate in the readahead code path (via:
767  * fscache_readpages_or_alloc) after delegating to the base filesystem
768  */
769 void __fscache_readpages_cancel(struct fscache_cookie *cookie,
770                                 struct list_head *pages)
771 {
772         struct page *page;
773
774         list_for_each_entry(page, pages, lru) {
775                 if (PageFsCache(page))
776                         __fscache_uncache_page(cookie, page);
777         }
778 }
779 EXPORT_SYMBOL(__fscache_readpages_cancel);
780
781 /*
782  * release a write op reference
783  */
784 static void fscache_release_write_op(struct fscache_operation *_op)
785 {
786         _enter("{OP%x}", _op->debug_id);
787 }
788
789 /*
790  * perform the background storage of a page into the cache
791  */
792 static void fscache_write_op(struct fscache_operation *_op)
793 {
794         struct fscache_storage *op =
795                 container_of(_op, struct fscache_storage, op);
796         struct fscache_object *object = op->op.object;
797         struct fscache_cookie *cookie;
798         struct page *page;
799         unsigned n;
800         void *results[1];
801         int ret;
802
803         _enter("{OP%x,%d}", op->op.debug_id, atomic_read(&op->op.usage));
804
805 again:
806         spin_lock(&object->lock);
807         cookie = object->cookie;
808
809         if (!fscache_object_is_active(object)) {
810                 /* If we get here, then the on-disk cache object likely no
811                  * longer exists, so we should just cancel this write
812                  * operation.
813                  */
814                 spin_unlock(&object->lock);
815                 fscache_op_complete(&op->op, true);
816                 _leave(" [inactive]");
817                 return;
818         }
819
820         if (!cookie) {
821                 /* If we get here, then the cookie belonging to the object was
822                  * detached, probably by the cookie being withdrawn due to
823                  * memory pressure, which means that the pages we might write
824                  * to the cache from no longer exist - therefore, we can just
825                  * cancel this write operation.
826                  */
827                 spin_unlock(&object->lock);
828                 fscache_op_complete(&op->op, true);
829                 _leave(" [cancel] op{f=%lx s=%u} obj{s=%s f=%lx}",
830                        _op->flags, _op->state, object->state->short_name,
831                        object->flags);
832                 return;
833         }
834
835         spin_lock(&cookie->stores_lock);
836
837         fscache_stat(&fscache_n_store_calls);
838
839         /* find a page to store */
840         results[0] = NULL;
841         page = NULL;
842         n = radix_tree_gang_lookup_tag(&cookie->stores, results, 0, 1,
843                                        FSCACHE_COOKIE_PENDING_TAG);
844         trace_fscache_gang_lookup(cookie, &op->op, results, n, op->store_limit);
845         if (n != 1)
846                 goto superseded;
847         page = results[0];
848         _debug("gang %d [%lx]", n, page->index);
849
850         radix_tree_tag_set(&cookie->stores, page->index,
851                            FSCACHE_COOKIE_STORING_TAG);
852         radix_tree_tag_clear(&cookie->stores, page->index,
853                              FSCACHE_COOKIE_PENDING_TAG);
854         trace_fscache_page(cookie, page, fscache_page_radix_pend2store);
855
856         spin_unlock(&cookie->stores_lock);
857         spin_unlock(&object->lock);
858
859         if (page->index >= op->store_limit)
860                 goto discard_page;
861
862         fscache_stat(&fscache_n_store_pages);
863         fscache_stat(&fscache_n_cop_write_page);
864         ret = object->cache->ops->write_page(op, page);
865         fscache_stat_d(&fscache_n_cop_write_page);
866         trace_fscache_wrote_page(cookie, page, &op->op, ret);
867         fscache_end_page_write(object, page);
868         if (ret < 0) {
869                 fscache_abort_object(object);
870                 fscache_op_complete(&op->op, true);
871         } else {
872                 fscache_enqueue_operation(&op->op);
873         }
874
875         _leave("");
876         return;
877
878 discard_page:
879         fscache_stat(&fscache_n_store_pages_over_limit);
880         trace_fscache_wrote_page(cookie, page, &op->op, -ENOBUFS);
881         fscache_end_page_write(object, page);
882         goto again;
883
884 superseded:
885         /* this writer is going away and there aren't any more things to
886          * write */
887         _debug("cease");
888         spin_unlock(&cookie->stores_lock);
889         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
890         spin_unlock(&object->lock);
891         fscache_op_complete(&op->op, false);
892         _leave("");
893 }
894
895 /*
896  * Clear the pages pending writing for invalidation
897  */
898 void fscache_invalidate_writes(struct fscache_cookie *cookie)
899 {
900         struct page *page;
901         void *results[16];
902         int n, i;
903
904         _enter("");
905
906         for (;;) {
907                 spin_lock(&cookie->stores_lock);
908                 n = radix_tree_gang_lookup_tag(&cookie->stores, results, 0,
909                                                ARRAY_SIZE(results),
910                                                FSCACHE_COOKIE_PENDING_TAG);
911                 if (n == 0) {
912                         spin_unlock(&cookie->stores_lock);
913                         break;
914                 }
915
916                 for (i = n - 1; i >= 0; i--) {
917                         page = results[i];
918                         radix_tree_delete(&cookie->stores, page->index);
919                         trace_fscache_page(cookie, page, fscache_page_radix_delete);
920                         trace_fscache_page(cookie, page, fscache_page_inval);
921                 }
922
923                 spin_unlock(&cookie->stores_lock);
924
925                 for (i = n - 1; i >= 0; i--)
926                         put_page(results[i]);
927         }
928
929         wake_up_bit(&cookie->flags, 0);
930         trace_fscache_wake_cookie(cookie);
931
932         _leave("");
933 }
934
935 /*
936  * request a page be stored in the cache
937  * - returns:
938  *   -ENOMEM    - out of memory, nothing done
939  *   -ENOBUFS   - no backing object available in which to cache the page
940  *   0          - dispatched a write - it'll call end_io_func() when finished
941  *
942  * if the cookie still has a backing object at this point, that object can be
943  * in one of a few states with respect to storage processing:
944  *
945  *  (1) negative lookup, object not yet created (FSCACHE_COOKIE_CREATING is
946  *      set)
947  *
948  *      (a) no writes yet
949  *
950  *      (b) writes deferred till post-creation (mark page for writing and
951  *          return immediately)
952  *
953  *  (2) negative lookup, object created, initial fill being made from netfs
954  *
955  *      (a) fill point not yet reached this page (mark page for writing and
956  *          return)
957  *
958  *      (b) fill point passed this page (queue op to store this page)
959  *
960  *  (3) object extant (queue op to store this page)
961  *
962  * any other state is invalid
963  */
964 int __fscache_write_page(struct fscache_cookie *cookie,
965                          struct page *page,
966                          loff_t object_size,
967                          gfp_t gfp)
968 {
969         struct fscache_storage *op;
970         struct fscache_object *object;
971         bool wake_cookie = false;
972         int ret;
973
974         _enter("%p,%x,", cookie, (u32) page->flags);
975
976         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
977         ASSERT(PageFsCache(page));
978
979         fscache_stat(&fscache_n_stores);
980
981         if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
982                 _leave(" = -ENOBUFS [invalidating]");
983                 return -ENOBUFS;
984         }
985
986         op = kzalloc(sizeof(*op), GFP_NOIO | __GFP_NOMEMALLOC | __GFP_NORETRY);
987         if (!op)
988                 goto nomem;
989
990         fscache_operation_init(cookie, &op->op, fscache_write_op, NULL,
991                                fscache_release_write_op);
992         op->op.flags = FSCACHE_OP_ASYNC |
993                 (1 << FSCACHE_OP_WAITING) |
994                 (1 << FSCACHE_OP_UNUSE_COOKIE);
995
996         ret = radix_tree_maybe_preload(gfp & ~__GFP_HIGHMEM);
997         if (ret < 0)
998                 goto nomem_free;
999
1000         trace_fscache_page_op(cookie, page, &op->op, fscache_page_op_write_one);
1001
1002         ret = -ENOBUFS;
1003         spin_lock(&cookie->lock);
1004
1005         if (!fscache_cookie_enabled(cookie) ||
1006             hlist_empty(&cookie->backing_objects))
1007                 goto nobufs;
1008         object = hlist_entry(cookie->backing_objects.first,
1009                              struct fscache_object, cookie_link);
1010         if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
1011                 goto nobufs;
1012
1013         trace_fscache_page(cookie, page, fscache_page_write);
1014
1015         /* add the page to the pending-storage radix tree on the backing
1016          * object */
1017         spin_lock(&object->lock);
1018
1019         if (object->store_limit_l != object_size)
1020                 fscache_set_store_limit(object, object_size);
1021
1022         spin_lock(&cookie->stores_lock);
1023
1024         _debug("store limit %llx", (unsigned long long) object->store_limit);
1025
1026         ret = radix_tree_insert(&cookie->stores, page->index, page);
1027         if (ret < 0) {
1028                 if (ret == -EEXIST)
1029                         goto already_queued;
1030                 _debug("insert failed %d", ret);
1031                 goto nobufs_unlock_obj;
1032         }
1033
1034         trace_fscache_page(cookie, page, fscache_page_radix_insert);
1035         radix_tree_tag_set(&cookie->stores, page->index,
1036                            FSCACHE_COOKIE_PENDING_TAG);
1037         trace_fscache_page(cookie, page, fscache_page_radix_set_pend);
1038         get_page(page);
1039
1040         /* we only want one writer at a time, but we do need to queue new
1041          * writers after exclusive ops */
1042         if (test_and_set_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags))
1043                 goto already_pending;
1044
1045         spin_unlock(&cookie->stores_lock);
1046         spin_unlock(&object->lock);
1047
1048         op->op.debug_id = atomic_inc_return(&fscache_op_debug_id);
1049         op->store_limit = object->store_limit;
1050
1051         __fscache_use_cookie(cookie);
1052         if (fscache_submit_op(object, &op->op) < 0)
1053                 goto submit_failed;
1054
1055         spin_unlock(&cookie->lock);
1056         radix_tree_preload_end();
1057         fscache_stat(&fscache_n_store_ops);
1058         fscache_stat(&fscache_n_stores_ok);
1059
1060         /* the work queue now carries its own ref on the object */
1061         fscache_put_operation(&op->op);
1062         _leave(" = 0");
1063         return 0;
1064
1065 already_queued:
1066         fscache_stat(&fscache_n_stores_again);
1067 already_pending:
1068         spin_unlock(&cookie->stores_lock);
1069         spin_unlock(&object->lock);
1070         spin_unlock(&cookie->lock);
1071         radix_tree_preload_end();
1072         fscache_put_operation(&op->op);
1073         fscache_stat(&fscache_n_stores_ok);
1074         _leave(" = 0");
1075         return 0;
1076
1077 submit_failed:
1078         spin_lock(&cookie->stores_lock);
1079         radix_tree_delete(&cookie->stores, page->index);
1080         trace_fscache_page(cookie, page, fscache_page_radix_delete);
1081         spin_unlock(&cookie->stores_lock);
1082         wake_cookie = __fscache_unuse_cookie(cookie);
1083         put_page(page);
1084         ret = -ENOBUFS;
1085         goto nobufs;
1086
1087 nobufs_unlock_obj:
1088         spin_unlock(&cookie->stores_lock);
1089         spin_unlock(&object->lock);
1090 nobufs:
1091         spin_unlock(&cookie->lock);
1092         radix_tree_preload_end();
1093         fscache_put_operation(&op->op);
1094         if (wake_cookie)
1095                 __fscache_wake_unused_cookie(cookie);
1096         fscache_stat(&fscache_n_stores_nobufs);
1097         _leave(" = -ENOBUFS");
1098         return -ENOBUFS;
1099
1100 nomem_free:
1101         fscache_put_operation(&op->op);
1102 nomem:
1103         fscache_stat(&fscache_n_stores_oom);
1104         _leave(" = -ENOMEM");
1105         return -ENOMEM;
1106 }
1107 EXPORT_SYMBOL(__fscache_write_page);
1108
1109 /*
1110  * remove a page from the cache
1111  */
1112 void __fscache_uncache_page(struct fscache_cookie *cookie, struct page *page)
1113 {
1114         struct fscache_object *object;
1115
1116         _enter(",%p", page);
1117
1118         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
1119         ASSERTCMP(page, !=, NULL);
1120
1121         fscache_stat(&fscache_n_uncaches);
1122
1123         /* cache withdrawal may beat us to it */
1124         if (!PageFsCache(page))
1125                 goto done;
1126
1127         trace_fscache_page(cookie, page, fscache_page_uncache);
1128
1129         /* get the object */
1130         spin_lock(&cookie->lock);
1131
1132         if (hlist_empty(&cookie->backing_objects)) {
1133                 ClearPageFsCache(page);
1134                 goto done_unlock;
1135         }
1136
1137         object = hlist_entry(cookie->backing_objects.first,
1138                              struct fscache_object, cookie_link);
1139
1140         /* there might now be stuff on disk we could read */
1141         clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
1142
1143         /* only invoke the cache backend if we managed to mark the page
1144          * uncached here; this deals with synchronisation vs withdrawal */
1145         if (TestClearPageFsCache(page) &&
1146             object->cache->ops->uncache_page) {
1147                 /* the cache backend releases the cookie lock */
1148                 fscache_stat(&fscache_n_cop_uncache_page);
1149                 object->cache->ops->uncache_page(object, page);
1150                 fscache_stat_d(&fscache_n_cop_uncache_page);
1151                 goto done;
1152         }
1153
1154 done_unlock:
1155         spin_unlock(&cookie->lock);
1156 done:
1157         _leave("");
1158 }
1159 EXPORT_SYMBOL(__fscache_uncache_page);
1160
1161 /**
1162  * fscache_mark_page_cached - Mark a page as being cached
1163  * @op: The retrieval op pages are being marked for
1164  * @page: The page to be marked
1165  *
1166  * Mark a netfs page as being cached.  After this is called, the netfs
1167  * must call fscache_uncache_page() to remove the mark.
1168  */
1169 void fscache_mark_page_cached(struct fscache_retrieval *op, struct page *page)
1170 {
1171         struct fscache_cookie *cookie = op->op.object->cookie;
1172
1173 #ifdef CONFIG_FSCACHE_STATS
1174         atomic_inc(&fscache_n_marks);
1175 #endif
1176
1177         trace_fscache_page(cookie, page, fscache_page_cached);
1178
1179         _debug("- mark %p{%lx}", page, page->index);
1180         if (TestSetPageFsCache(page)) {
1181                 static bool once_only;
1182                 if (!once_only) {
1183                         once_only = true;
1184                         pr_warn("Cookie type %s marked page %lx multiple times\n",
1185                                 cookie->def->name, page->index);
1186                 }
1187         }
1188
1189         if (cookie->def->mark_page_cached)
1190                 cookie->def->mark_page_cached(cookie->netfs_data,
1191                                               op->mapping, page);
1192 }
1193 EXPORT_SYMBOL(fscache_mark_page_cached);
1194
1195 /**
1196  * fscache_mark_pages_cached - Mark pages as being cached
1197  * @op: The retrieval op pages are being marked for
1198  * @pagevec: The pages to be marked
1199  *
1200  * Mark a bunch of netfs pages as being cached.  After this is called,
1201  * the netfs must call fscache_uncache_page() to remove the mark.
1202  */
1203 void fscache_mark_pages_cached(struct fscache_retrieval *op,
1204                                struct pagevec *pagevec)
1205 {
1206         unsigned long loop;
1207
1208         for (loop = 0; loop < pagevec->nr; loop++)
1209                 fscache_mark_page_cached(op, pagevec->pages[loop]);
1210
1211         pagevec_reinit(pagevec);
1212 }
1213 EXPORT_SYMBOL(fscache_mark_pages_cached);
1214
1215 /*
1216  * Uncache all the pages in an inode that are marked PG_fscache, assuming them
1217  * to be associated with the given cookie.
1218  */
1219 void __fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
1220                                        struct inode *inode)
1221 {
1222         struct address_space *mapping = inode->i_mapping;
1223         struct pagevec pvec;
1224         pgoff_t next;
1225         int i;
1226
1227         _enter("%p,%p", cookie, inode);
1228
1229         if (!mapping || mapping->nrpages == 0) {
1230                 _leave(" [no pages]");
1231                 return;
1232         }
1233
1234         pagevec_init(&pvec);
1235         next = 0;
1236         do {
1237                 if (!pagevec_lookup(&pvec, mapping, &next))
1238                         break;
1239                 for (i = 0; i < pagevec_count(&pvec); i++) {
1240                         struct page *page = pvec.pages[i];
1241                         if (PageFsCache(page)) {
1242                                 __fscache_wait_on_page_write(cookie, page);
1243                                 __fscache_uncache_page(cookie, page);
1244                         }
1245                 }
1246                 pagevec_release(&pvec);
1247                 cond_resched();
1248         } while (next);
1249
1250         _leave("");
1251 }
1252 EXPORT_SYMBOL(__fscache_uncache_all_inode_pages);