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
  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  * decide whether a page can be released, possibly by cancelling a store to it
  48  * - we're allowed to sleep if __GFP_WAIT is flagged
  49  */
  50 bool __fscache_maybe_release_page(struct fscache_cookie *cookie,
  51                                   struct page *page,
  52                                   gfp_t gfp)
  53 {
  54         struct page *xpage;
  55         void *val;
  56
  57         _enter("%p,%p,%x", cookie, page, gfp);
  58
  59         rcu_read_lock();
  60         val = radix_tree_lookup(&cookie->stores, page->index);
  61         if (!val) {
  62                 rcu_read_unlock();
  63                 fscache_stat(&fscache_n_store_vmscan_not_storing);
  64                 __fscache_uncache_page(cookie, page);
  65                 return true;
  66         }
  67
  68         /* see if the page is actually undergoing storage - if so we can't get
  69          * rid of it till the cache has finished with it */
  70         if (radix_tree_tag_get(&cookie->stores, page->index,
  71                                FSCACHE_COOKIE_STORING_TAG)) {
  72                 rcu_read_unlock();
  73                 goto page_busy;
  74         }
  75
  76         /* the page is pending storage, so we attempt to cancel the store and
  77          * discard the store request so that the page can be reclaimed */
  78         spin_lock(&cookie->stores_lock);
  79         rcu_read_unlock();
  80
  81         if (radix_tree_tag_get(&cookie->stores, page->index,
  82                                FSCACHE_COOKIE_STORING_TAG)) {
  83                 /* the page started to undergo storage whilst we were looking,
  84                  * so now we can only wait or return */
  85                 spin_unlock(&cookie->stores_lock);
  86                 goto page_busy;
  87         }
  88
  89         xpage = radix_tree_delete(&cookie->stores, page->index);
  90         spin_unlock(&cookie->stores_lock);
  91
  92         if (xpage) {
  93                 fscache_stat(&fscache_n_store_vmscan_cancelled);
  94                 fscache_stat(&fscache_n_store_radix_deletes);
  95                 ASSERTCMP(xpage, ==, page);
  96         } else {
  97                 fscache_stat(&fscache_n_store_vmscan_gone);
  98         }
  99
 100         wake_up_bit(&cookie->flags, 0);
 101         if (xpage)
 102                 page_cache_release(xpage);
 103         __fscache_uncache_page(cookie, page);
 104         return true;
 105
 106 page_busy:
 107         /* we might want to wait here, but that could deadlock the allocator as
 108          * the work threads writing to the cache may all end up sleeping
 109          * on memory allocation */
 110         fscache_stat(&fscache_n_store_vmscan_busy);
 111         return false;
 112 }
 113 EXPORT_SYMBOL(__fscache_maybe_release_page);
 114
 115 /*
 116  * note that a page has finished being written to the cache
 117  */
 118 static void fscache_end_page_write(struct fscache_object *object,
 119                                    struct page *page)
 120 {
 121         struct fscache_cookie *cookie;
 122         struct page *xpage = NULL;
 123
 124         spin_lock(&object->lock);
 125         cookie = object->cookie;
 126         if (cookie) {
 127                 /* delete the page from the tree if it is now no longer
 128                  * pending */
 129                 spin_lock(&cookie->stores_lock);
 130                 radix_tree_tag_clear(&cookie->stores, page->index,
 131                                      FSCACHE_COOKIE_STORING_TAG);
 132                 if (!radix_tree_tag_get(&cookie->stores, page->index,
 133                                         FSCACHE_COOKIE_PENDING_TAG)) {
 134                         fscache_stat(&fscache_n_store_radix_deletes);
 135                         xpage = radix_tree_delete(&cookie->stores, page->index);
 136                 }
 137                 spin_unlock(&cookie->stores_lock);
 138                 wake_up_bit(&cookie->flags, 0);
 139         }
 140         spin_unlock(&object->lock);
 141         if (xpage)
 142                 page_cache_release(xpage);
 143 }
 144
 145 /*
 146  * actually apply the changed attributes to a cache object
 147  */
 148 static void fscache_attr_changed_op(struct fscache_operation *op)
 149 {
 150         struct fscache_object *object = op->object;
 151         int ret;
 152
 153         _enter("{OBJ%x OP%x}", object->debug_id, op->debug_id);
 154
 155         fscache_stat(&fscache_n_attr_changed_calls);
 156
 157         if (fscache_object_is_active(object)) {
 158                 fscache_stat(&fscache_n_cop_attr_changed);
 159                 ret = object->cache->ops->attr_changed(object);
 160                 fscache_stat_d(&fscache_n_cop_attr_changed);
 161                 if (ret < 0)
 162                         fscache_abort_object(object);
 163         }
 164
 165         _leave("");
 166 }
 167
 168 /*
 169  * notification that the attributes on an object have changed
 170  */
 171 int __fscache_attr_changed(struct fscache_cookie *cookie)
 172 {
 173         struct fscache_operation *op;
 174         struct fscache_object *object;
 175
 176         _enter("%p", cookie);
 177
 178         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 179
 180         fscache_stat(&fscache_n_attr_changed);
 181
 182         op = kzalloc(sizeof(*op), GFP_KERNEL);
 183         if (!op) {
 184                 fscache_stat(&fscache_n_attr_changed_nomem);
 185                 _leave(" = -ENOMEM");
 186                 return -ENOMEM;
 187         }
 188
 189         fscache_operation_init(op, fscache_attr_changed_op, NULL);
 190         op->flags = FSCACHE_OP_ASYNC | (1 << FSCACHE_OP_EXCLUSIVE);
 191
 192         spin_lock(&cookie->lock);
 193
 194         if (hlist_empty(&cookie->backing_objects))
 195                 goto nobufs;
 196         object = hlist_entry(cookie->backing_objects.first,
 197                              struct fscache_object, cookie_link);
 198
 199         if (fscache_submit_exclusive_op(object, op) < 0)
 200                 goto nobufs;
 201         spin_unlock(&cookie->lock);
 202         fscache_stat(&fscache_n_attr_changed_ok);
 203         fscache_put_operation(op);
 204         _leave(" = 0");
 205         return 0;
 206
 207 nobufs:
 208         spin_unlock(&cookie->lock);
 209         kfree(op);
 210         fscache_stat(&fscache_n_attr_changed_nobufs);
 211         _leave(" = %d", -ENOBUFS);
 212         return -ENOBUFS;
 213 }
 214 EXPORT_SYMBOL(__fscache_attr_changed);
 215
 216 /*
 217  * release a retrieval op reference
 218  */
 219 static void fscache_release_retrieval_op(struct fscache_operation *_op)
 220 {
 221         struct fscache_retrieval *op =
 222                 container_of(_op, struct fscache_retrieval, op);
 223
 224         _enter("{OP%x}", op->op.debug_id);
 225
 226         fscache_hist(fscache_retrieval_histogram, op->start_time);
 227         if (op->context)
 228                 fscache_put_context(op->op.object->cookie, op->context);
 229
 230         _leave("");
 231 }
 232
 233 /*
 234  * allocate a retrieval op
 235  */
 236 static struct fscache_retrieval *fscache_alloc_retrieval(
 237         struct address_space *mapping,
 238         fscache_rw_complete_t end_io_func,
 239         void *context)
 240 {
 241         struct fscache_retrieval *op;
 242
 243         /* allocate a retrieval operation and attempt to submit it */
 244         op = kzalloc(sizeof(*op), GFP_NOIO);
 245         if (!op) {
 246                 fscache_stat(&fscache_n_retrievals_nomem);
 247                 return NULL;
 248         }
 249
 250         fscache_operation_init(&op->op, NULL, fscache_release_retrieval_op);
 251         op->op.flags    = FSCACHE_OP_MYTHREAD | (1 << FSCACHE_OP_WAITING);
 252         op->mapping     = mapping;
 253         op->end_io_func = end_io_func;
 254         op->context     = context;
 255         op->start_time  = jiffies;
 256         INIT_LIST_HEAD(&op->to_do);
 257         return op;
 258 }
 259
 260 /*
 261  * wait for a deferred lookup to complete
 262  */
 263 static int fscache_wait_for_deferred_lookup(struct fscache_cookie *cookie)
 264 {
 265         unsigned long jif;
 266
 267         _enter("");
 268
 269         if (!test_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags)) {
 270                 _leave(" = 0 [imm]");
 271                 return 0;
 272         }
 273
 274         fscache_stat(&fscache_n_retrievals_wait);
 275
 276         jif = jiffies;
 277         if (wait_on_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP,
 278                         fscache_wait_bit_interruptible,
 279                         TASK_INTERRUPTIBLE) != 0) {
 280                 fscache_stat(&fscache_n_retrievals_intr);
 281                 _leave(" = -ERESTARTSYS");
 282                 return -ERESTARTSYS;
 283         }
 284
 285         ASSERT(!test_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags));
 286
 287         smp_rmb();
 288         fscache_hist(fscache_retrieval_delay_histogram, jif);
 289         _leave(" = 0 [dly]");
 290         return 0;
 291 }
 292
 293 /*
 294  * wait for an object to become active (or dead)
 295  */
 296 static int fscache_wait_for_retrieval_activation(struct fscache_object *object,
 297                                                  struct fscache_retrieval *op,
 298                                                  atomic_t *stat_op_waits,
 299                                                  atomic_t *stat_object_dead)
 300 {
 301         int ret;
 302
 303         if (!test_bit(FSCACHE_OP_WAITING, &op->op.flags))
 304                 goto check_if_dead;
 305
 306         _debug(">>> WT");
 307         fscache_stat(stat_op_waits);
 308         if (wait_on_bit(&op->op.flags, FSCACHE_OP_WAITING,
 309                         fscache_wait_bit_interruptible,
 310                         TASK_INTERRUPTIBLE) < 0) {
 311                 ret = fscache_cancel_op(&op->op);
 312                 if (ret == 0)
 313                         return -ERESTARTSYS;
 314
 315                 /* it's been removed from the pending queue by another party,
 316                  * so we should get to run shortly */
 317                 wait_on_bit(&op->op.flags, FSCACHE_OP_WAITING,
 318                             fscache_wait_bit, TASK_UNINTERRUPTIBLE);
 319         }
 320         _debug("<<< GO");
 321
 322 check_if_dead:
 323         if (unlikely(fscache_object_is_dead(object))) {
 324                 fscache_stat(stat_object_dead);
 325                 return -ENOBUFS;
 326         }
 327         return 0;
 328 }
 329
 330 /*
 331  * read a page from the cache or allocate a block in which to store it
 332  * - we return:
 333  *   -ENOMEM    - out of memory, nothing done
 334  *   -ERESTARTSYS - interrupted
 335  *   -ENOBUFS   - no backing object available in which to cache the block
 336  *   -ENODATA   - no data available in the backing object for this block
 337  *   0          - dispatched a read - it'll call end_io_func() when finished
 338  */
 339 int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 340                                  struct page *page,
 341                                  fscache_rw_complete_t end_io_func,
 342                                  void *context,
 343                                  gfp_t gfp)
 344 {
 345         struct fscache_retrieval *op;
 346         struct fscache_object *object;
 347         int ret;
 348
 349         _enter("%p,%p,,,", cookie, page);
 350
 351         fscache_stat(&fscache_n_retrievals);
 352
 353         if (hlist_empty(&cookie->backing_objects))
 354                 goto nobufs;
 355
 356         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 357         ASSERTCMP(page, !=, NULL);
 358
 359         if (fscache_wait_for_deferred_lookup(cookie) < 0)
 360                 return -ERESTARTSYS;
 361
 362         op = fscache_alloc_retrieval(page->mapping, end_io_func, context);
 363         if (!op) {
 364                 _leave(" = -ENOMEM");
 365                 return -ENOMEM;
 366         }
 367
 368         spin_lock(&cookie->lock);
 369
 370         if (hlist_empty(&cookie->backing_objects))
 371                 goto nobufs_unlock;
 372         object = hlist_entry(cookie->backing_objects.first,
 373                              struct fscache_object, cookie_link);
 374
 375         ASSERTCMP(object->state, >, FSCACHE_OBJECT_LOOKING_UP);
 376
 377         atomic_inc(&object->n_reads);
 378         set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
 379
 380         if (fscache_submit_op(object, &op->op) < 0)
 381                 goto nobufs_unlock;
 382         spin_unlock(&cookie->lock);
 383
 384         fscache_stat(&fscache_n_retrieval_ops);
 385
 386         /* pin the netfs read context in case we need to do the actual netfs
 387          * read because we've encountered a cache read failure */
 388         fscache_get_context(object->cookie, op->context);
 389
 390         /* we wait for the operation to become active, and then process it
 391          * *here*, in this thread, and not in the thread pool */
 392         ret = fscache_wait_for_retrieval_activation(
 393                 object, op,
 394                 __fscache_stat(&fscache_n_retrieval_op_waits),
 395                 __fscache_stat(&fscache_n_retrievals_object_dead));
 396         if (ret < 0)
 397                 goto error;
 398
 399         /* ask the cache to honour the operation */
 400         if (test_bit(FSCACHE_COOKIE_NO_DATA_YET, &object->cookie->flags)) {
 401                 fscache_stat(&fscache_n_cop_allocate_page);
 402                 ret = object->cache->ops->allocate_page(op, page, gfp);
 403                 fscache_stat_d(&fscache_n_cop_allocate_page);
 404                 if (ret == 0)
 405                         ret = -ENODATA;
 406         } else {
 407                 fscache_stat(&fscache_n_cop_read_or_alloc_page);
 408                 ret = object->cache->ops->read_or_alloc_page(op, page, gfp);
 409                 fscache_stat_d(&fscache_n_cop_read_or_alloc_page);
 410         }
 411
 412 error:
 413         if (ret == -ENOMEM)
 414                 fscache_stat(&fscache_n_retrievals_nomem);
 415         else if (ret == -ERESTARTSYS)
 416                 fscache_stat(&fscache_n_retrievals_intr);
 417         else if (ret == -ENODATA)
 418                 fscache_stat(&fscache_n_retrievals_nodata);
 419         else if (ret < 0)
 420                 fscache_stat(&fscache_n_retrievals_nobufs);
 421         else
 422                 fscache_stat(&fscache_n_retrievals_ok);
 423
 424         fscache_put_retrieval(op);
 425         _leave(" = %d", ret);
 426         return ret;
 427
 428 nobufs_unlock:
 429         spin_unlock(&cookie->lock);
 430         kfree(op);
 431 nobufs:
 432         fscache_stat(&fscache_n_retrievals_nobufs);
 433         _leave(" = -ENOBUFS");
 434         return -ENOBUFS;
 435 }
 436 EXPORT_SYMBOL(__fscache_read_or_alloc_page);
 437
 438 /*
 439  * read a list of page from the cache or allocate a block in which to store
 440  * them
 441  * - we return:
 442  *   -ENOMEM    - out of memory, some pages may be being read
 443  *   -ERESTARTSYS - interrupted, some pages may be being read
 444  *   -ENOBUFS   - no backing object or space available in which to cache any
 445  *                pages not being read
 446  *   -ENODATA   - no data available in the backing object for some or all of
 447  *                the pages
 448  *   0          - dispatched a read on all pages
 449  *
 450  * end_io_func() will be called for each page read from the cache as it is
 451  * finishes being read
 452  *
 453  * any pages for which a read is dispatched will be removed from pages and
 454  * nr_pages
 455  */
 456 int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
 457                                   struct address_space *mapping,
 458                                   struct list_head *pages,
 459                                   unsigned *nr_pages,
 460                                   fscache_rw_complete_t end_io_func,
 461                                   void *context,
 462                                   gfp_t gfp)
 463 {
 464         struct fscache_retrieval *op;
 465         struct fscache_object *object;
 466         int ret;
 467
 468         _enter("%p,,%d,,,", cookie, *nr_pages);
 469
 470         fscache_stat(&fscache_n_retrievals);
 471
 472         if (hlist_empty(&cookie->backing_objects))
 473                 goto nobufs;
 474
 475         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 476         ASSERTCMP(*nr_pages, >, 0);
 477         ASSERT(!list_empty(pages));
 478
 479         if (fscache_wait_for_deferred_lookup(cookie) < 0)
 480                 return -ERESTARTSYS;
 481
 482         op = fscache_alloc_retrieval(mapping, end_io_func, context);
 483         if (!op)
 484                 return -ENOMEM;
 485
 486         spin_lock(&cookie->lock);
 487
 488         if (hlist_empty(&cookie->backing_objects))
 489                 goto nobufs_unlock;
 490         object = hlist_entry(cookie->backing_objects.first,
 491                              struct fscache_object, cookie_link);
 492
 493         atomic_inc(&object->n_reads);
 494         set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
 495
 496         if (fscache_submit_op(object, &op->op) < 0)
 497                 goto nobufs_unlock;
 498         spin_unlock(&cookie->lock);
 499
 500         fscache_stat(&fscache_n_retrieval_ops);
 501
 502         /* pin the netfs read context in case we need to do the actual netfs
 503          * read because we've encountered a cache read failure */
 504         fscache_get_context(object->cookie, op->context);
 505
 506         /* we wait for the operation to become active, and then process it
 507          * *here*, in this thread, and not in the thread pool */
 508         ret = fscache_wait_for_retrieval_activation(
 509                 object, op,
 510                 __fscache_stat(&fscache_n_retrieval_op_waits),
 511                 __fscache_stat(&fscache_n_retrievals_object_dead));
 512         if (ret < 0)
 513                 goto error;
 514
 515         /* ask the cache to honour the operation */
 516         if (test_bit(FSCACHE_COOKIE_NO_DATA_YET, &object->cookie->flags)) {
 517                 fscache_stat(&fscache_n_cop_allocate_pages);
 518                 ret = object->cache->ops->allocate_pages(
 519                         op, pages, nr_pages, gfp);
 520                 fscache_stat_d(&fscache_n_cop_allocate_pages);
 521         } else {
 522                 fscache_stat(&fscache_n_cop_read_or_alloc_pages);
 523                 ret = object->cache->ops->read_or_alloc_pages(
 524                         op, pages, nr_pages, gfp);
 525                 fscache_stat_d(&fscache_n_cop_read_or_alloc_pages);
 526         }
 527
 528 error:
 529         if (ret == -ENOMEM)
 530                 fscache_stat(&fscache_n_retrievals_nomem);
 531         else if (ret == -ERESTARTSYS)
 532                 fscache_stat(&fscache_n_retrievals_intr);
 533         else if (ret == -ENODATA)
 534                 fscache_stat(&fscache_n_retrievals_nodata);
 535         else if (ret < 0)
 536                 fscache_stat(&fscache_n_retrievals_nobufs);
 537         else
 538                 fscache_stat(&fscache_n_retrievals_ok);
 539
 540         fscache_put_retrieval(op);
 541         _leave(" = %d", ret);
 542         return ret;
 543
 544 nobufs_unlock:
 545         spin_unlock(&cookie->lock);
 546         kfree(op);
 547 nobufs:
 548         fscache_stat(&fscache_n_retrievals_nobufs);
 549         _leave(" = -ENOBUFS");
 550         return -ENOBUFS;
 551 }
 552 EXPORT_SYMBOL(__fscache_read_or_alloc_pages);
 553
 554 /*
 555  * allocate a block in the cache on which to store a page
 556  * - we return:
 557  *   -ENOMEM    - out of memory, nothing done
 558  *   -ERESTARTSYS - interrupted
 559  *   -ENOBUFS   - no backing object available in which to cache the block
 560  *   0          - block allocated
 561  */
 562 int __fscache_alloc_page(struct fscache_cookie *cookie,
 563                          struct page *page,
 564                          gfp_t gfp)
 565 {
 566         struct fscache_retrieval *op;
 567         struct fscache_object *object;
 568         int ret;
 569
 570         _enter("%p,%p,,,", cookie, page);
 571
 572         fscache_stat(&fscache_n_allocs);
 573
 574         if (hlist_empty(&cookie->backing_objects))
 575                 goto nobufs;
 576
 577         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 578         ASSERTCMP(page, !=, NULL);
 579
 580         if (fscache_wait_for_deferred_lookup(cookie) < 0)
 581                 return -ERESTARTSYS;
 582
 583         op = fscache_alloc_retrieval(page->mapping, NULL, NULL);
 584         if (!op)
 585                 return -ENOMEM;
 586
 587         spin_lock(&cookie->lock);
 588
 589         if (hlist_empty(&cookie->backing_objects))
 590                 goto nobufs_unlock;
 591         object = hlist_entry(cookie->backing_objects.first,
 592                              struct fscache_object, cookie_link);
 593
 594         if (fscache_submit_op(object, &op->op) < 0)
 595                 goto nobufs_unlock;
 596         spin_unlock(&cookie->lock);
 597
 598         fscache_stat(&fscache_n_alloc_ops);
 599
 600         ret = fscache_wait_for_retrieval_activation(
 601                 object, op,
 602                 __fscache_stat(&fscache_n_alloc_op_waits),
 603                 __fscache_stat(&fscache_n_allocs_object_dead));
 604         if (ret < 0)
 605                 goto error;
 606
 607         /* ask the cache to honour the operation */
 608         fscache_stat(&fscache_n_cop_allocate_page);
 609         ret = object->cache->ops->allocate_page(op, page, gfp);
 610         fscache_stat_d(&fscache_n_cop_allocate_page);
 611
 612 error:
 613         if (ret == -ERESTARTSYS)
 614                 fscache_stat(&fscache_n_allocs_intr);
 615         else if (ret < 0)
 616                 fscache_stat(&fscache_n_allocs_nobufs);
 617         else
 618                 fscache_stat(&fscache_n_allocs_ok);
 619
 620         fscache_put_retrieval(op);
 621         _leave(" = %d", ret);
 622         return ret;
 623
 624 nobufs_unlock:
 625         spin_unlock(&cookie->lock);
 626         kfree(op);
 627 nobufs:
 628         fscache_stat(&fscache_n_allocs_nobufs);
 629         _leave(" = -ENOBUFS");
 630         return -ENOBUFS;
 631 }
 632 EXPORT_SYMBOL(__fscache_alloc_page);
 633
 634 /*
 635  * release a write op reference
 636  */
 637 static void fscache_release_write_op(struct fscache_operation *_op)
 638 {
 639         _enter("{OP%x}", _op->debug_id);
 640 }
 641
 642 /*
 643  * perform the background storage of a page into the cache
 644  */
 645 static void fscache_write_op(struct fscache_operation *_op)
 646 {
 647         struct fscache_storage *op =
 648                 container_of(_op, struct fscache_storage, op);
 649         struct fscache_object *object = op->op.object;
 650         struct fscache_cookie *cookie;
 651         struct page *page;
 652         unsigned n;
 653         void *results[1];
 654         int ret;
 655
 656         _enter("{OP%x,%d}", op->op.debug_id, atomic_read(&op->op.usage));
 657
 658         spin_lock(&object->lock);
 659         cookie = object->cookie;
 660
 661         if (!fscache_object_is_active(object) || !cookie) {
 662                 spin_unlock(&object->lock);
 663                 _leave("");
 664                 return;
 665         }
 666
 667         spin_lock(&cookie->stores_lock);
 668
 669         fscache_stat(&fscache_n_store_calls);
 670
 671         /* find a page to store */
 672         page = NULL;
 673         n = radix_tree_gang_lookup_tag(&cookie->stores, results, 0, 1,
 674                                        FSCACHE_COOKIE_PENDING_TAG);
 675         if (n != 1)
 676                 goto superseded;
 677         page = results[0];
 678         _debug("gang %d [%lx]", n, page->index);
 679         if (page->index > op->store_limit) {
 680                 fscache_stat(&fscache_n_store_pages_over_limit);
 681                 goto superseded;
 682         }
 683
 684         radix_tree_tag_set(&cookie->stores, page->index,
 685                            FSCACHE_COOKIE_STORING_TAG);
 686         radix_tree_tag_clear(&cookie->stores, page->index,
 687                              FSCACHE_COOKIE_PENDING_TAG);
 688
 689         spin_unlock(&cookie->stores_lock);
 690         spin_unlock(&object->lock);
 691
 692         fscache_stat(&fscache_n_store_pages);
 693         fscache_stat(&fscache_n_cop_write_page);
 694         ret = object->cache->ops->write_page(op, page);
 695         fscache_stat_d(&fscache_n_cop_write_page);
 696         fscache_end_page_write(object, page);
 697         if (ret < 0) {
 698                 fscache_abort_object(object);
 699         } else {
 700                 fscache_enqueue_operation(&op->op);
 701         }
 702
 703         _leave("");
 704         return;
 705
 706 superseded:
 707         /* this writer is going away and there aren't any more things to
 708          * write */
 709         _debug("cease");
 710         spin_unlock(&cookie->stores_lock);
 711         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 712         spin_unlock(&object->lock);
 713         _leave("");
 714 }
 715
 716 /*
 717  * request a page be stored in the cache
 718  * - returns:
 719  *   -ENOMEM    - out of memory, nothing done
 720  *   -ENOBUFS   - no backing object available in which to cache the page
 721  *   0          - dispatched a write - it'll call end_io_func() when finished
 722  *
 723  * if the cookie still has a backing object at this point, that object can be
 724  * in one of a few states with respect to storage processing:
 725  *
 726  *  (1) negative lookup, object not yet created (FSCACHE_COOKIE_CREATING is
 727  *      set)
 728  *
 729  *      (a) no writes yet (set FSCACHE_COOKIE_PENDING_FILL and queue deferred
 730  *          fill op)
 731  *
 732  *      (b) writes deferred till post-creation (mark page for writing and
 733  *          return immediately)
 734  *
 735  *  (2) negative lookup, object created, initial fill being made from netfs
 736  *      (FSCACHE_COOKIE_INITIAL_FILL is set)
 737  *
 738  *      (a) fill point not yet reached this page (mark page for writing and
 739  *          return)
 740  *
 741  *      (b) fill point passed this page (queue op to store this page)
 742  *
 743  *  (3) object extant (queue op to store this page)
 744  *
 745  * any other state is invalid
 746  */
 747 int __fscache_write_page(struct fscache_cookie *cookie,
 748                          struct page *page,
 749                          gfp_t gfp)
 750 {
 751         struct fscache_storage *op;
 752         struct fscache_object *object;
 753         int ret;
 754
 755         _enter("%p,%x,", cookie, (u32) page->flags);
 756
 757         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 758         ASSERT(PageFsCache(page));
 759
 760         fscache_stat(&fscache_n_stores);
 761
 762         op = kzalloc(sizeof(*op), GFP_NOIO);
 763         if (!op)
 764                 goto nomem;
 765
 766         fscache_operation_init(&op->op, fscache_write_op,
 767                                fscache_release_write_op);
 768         op->op.flags = FSCACHE_OP_ASYNC | (1 << FSCACHE_OP_WAITING);
 769
 770         ret = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
 771         if (ret < 0)
 772                 goto nomem_free;
 773
 774         ret = -ENOBUFS;
 775         spin_lock(&cookie->lock);
 776
 777         if (hlist_empty(&cookie->backing_objects))
 778                 goto nobufs;
 779         object = hlist_entry(cookie->backing_objects.first,
 780                              struct fscache_object, cookie_link);
 781         if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
 782                 goto nobufs;
 783
 784         /* add the page to the pending-storage radix tree on the backing
 785          * object */
 786         spin_lock(&object->lock);
 787         spin_lock(&cookie->stores_lock);
 788
 789         _debug("store limit %llx", (unsigned long long) object->store_limit);
 790
 791         ret = radix_tree_insert(&cookie->stores, page->index, page);
 792         if (ret < 0) {
 793                 if (ret == -EEXIST)
 794                         goto already_queued;
 795                 _debug("insert failed %d", ret);
 796                 goto nobufs_unlock_obj;
 797         }
 798
 799         radix_tree_tag_set(&cookie->stores, page->index,
 800                            FSCACHE_COOKIE_PENDING_TAG);
 801         page_cache_get(page);
 802
 803         /* we only want one writer at a time, but we do need to queue new
 804          * writers after exclusive ops */
 805         if (test_and_set_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags))
 806                 goto already_pending;
 807
 808         spin_unlock(&cookie->stores_lock);
 809         spin_unlock(&object->lock);
 810
 811         op->op.debug_id = atomic_inc_return(&fscache_op_debug_id);
 812         op->store_limit = object->store_limit;
 813
 814         if (fscache_submit_op(object, &op->op) < 0)
 815                 goto submit_failed;
 816
 817         spin_unlock(&cookie->lock);
 818         radix_tree_preload_end();
 819         fscache_stat(&fscache_n_store_ops);
 820         fscache_stat(&fscache_n_stores_ok);
 821
 822         /* the work queue now carries its own ref on the object */
 823         fscache_put_operation(&op->op);
 824         _leave(" = 0");
 825         return 0;
 826
 827 already_queued:
 828         fscache_stat(&fscache_n_stores_again);
 829 already_pending:
 830         spin_unlock(&cookie->stores_lock);
 831         spin_unlock(&object->lock);
 832         spin_unlock(&cookie->lock);
 833         radix_tree_preload_end();
 834         kfree(op);
 835         fscache_stat(&fscache_n_stores_ok);
 836         _leave(" = 0");
 837         return 0;
 838
 839 submit_failed:
 840         spin_lock(&cookie->stores_lock);
 841         radix_tree_delete(&cookie->stores, page->index);
 842         spin_unlock(&cookie->stores_lock);
 843         page_cache_release(page);
 844         ret = -ENOBUFS;
 845         goto nobufs;
 846
 847 nobufs_unlock_obj:
 848         spin_unlock(&cookie->stores_lock);
 849         spin_unlock(&object->lock);
 850 nobufs:
 851         spin_unlock(&cookie->lock);
 852         radix_tree_preload_end();
 853         kfree(op);
 854         fscache_stat(&fscache_n_stores_nobufs);
 855         _leave(" = -ENOBUFS");
 856         return -ENOBUFS;
 857
 858 nomem_free:
 859         kfree(op);
 860 nomem:
 861         fscache_stat(&fscache_n_stores_oom);
 862         _leave(" = -ENOMEM");
 863         return -ENOMEM;
 864 }
 865 EXPORT_SYMBOL(__fscache_write_page);
 866
 867 /*
 868  * remove a page from the cache
 869  */
 870 void __fscache_uncache_page(struct fscache_cookie *cookie, struct page *page)
 871 {
 872         struct fscache_object *object;
 873
 874         _enter(",%p", page);
 875
 876         ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 877         ASSERTCMP(page, !=, NULL);
 878
 879         fscache_stat(&fscache_n_uncaches);
 880
 881         /* cache withdrawal may beat us to it */
 882         if (!PageFsCache(page))
 883                 goto done;
 884
 885         /* get the object */
 886         spin_lock(&cookie->lock);
 887
 888         if (hlist_empty(&cookie->backing_objects)) {
 889                 ClearPageFsCache(page);
 890                 goto done_unlock;
 891         }
 892
 893         object = hlist_entry(cookie->backing_objects.first,
 894                              struct fscache_object, cookie_link);
 895
 896         /* there might now be stuff on disk we could read */
 897         clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 898
 899         /* only invoke the cache backend if we managed to mark the page
 900          * uncached here; this deals with synchronisation vs withdrawal */
 901         if (TestClearPageFsCache(page) &&
 902             object->cache->ops->uncache_page) {
 903                 /* the cache backend releases the cookie lock */
 904                 fscache_stat(&fscache_n_cop_uncache_page);
 905                 object->cache->ops->uncache_page(object, page);
 906                 fscache_stat_d(&fscache_n_cop_uncache_page);
 907                 goto done;
 908         }
 909
 910 done_unlock:
 911         spin_unlock(&cookie->lock);
 912 done:
 913         _leave("");
 914 }
 915 EXPORT_SYMBOL(__fscache_uncache_page);
 916
 917 /**
 918  * fscache_mark_pages_cached - Mark pages as being cached
 919  * @op: The retrieval op pages are being marked for
 920  * @pagevec: The pages to be marked
 921  *
 922  * Mark a bunch of netfs pages as being cached.  After this is called,
 923  * the netfs must call fscache_uncache_page() to remove the mark.
 924  */
 925 void fscache_mark_pages_cached(struct fscache_retrieval *op,
 926                                struct pagevec *pagevec)
 927 {
 928         struct fscache_cookie *cookie = op->op.object->cookie;
 929         unsigned long loop;
 930
 931 #ifdef CONFIG_FSCACHE_STATS
 932         atomic_add(pagevec->nr, &fscache_n_marks);
 933 #endif
 934
 935         for (loop = 0; loop < pagevec->nr; loop++) {
 936                 struct page *page = pagevec->pages[loop];
 937
 938                 _debug("- mark %p{%lx}", page, page->index);
 939                 if (TestSetPageFsCache(page)) {
 940                         static bool once_only;
 941                         if (!once_only) {
 942                                 once_only = true;
 943                                 printk(KERN_WARNING "FS-Cache:"
 944                                        " Cookie type %s marked page %lx"
 945                                        " multiple times\n",
 946                                        cookie->def->name, page->index);
 947                         }
 948                 }
 949         }
 950
 951         if (cookie->def->mark_pages_cached)
 952                 cookie->def->mark_pages_cached(cookie->netfs_data,
 953                                                op->mapping, pagevec);
 954         pagevec_reinit(pagevec);
 955 }
 956 EXPORT_SYMBOL(fscache_mark_pages_cached);