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TOMOYO Linux Cross Reference
Linux/fs/fscache/page.c

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

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