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