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