linux/fs/fscache/page.c
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   1/* Cache page management and data I/O routines
   2 *
   3 * Copyright (C) 2004-2008 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public License
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the License, or (at your option) any later version.
  10 */
  11
  12#define FSCACHE_DEBUG_LEVEL PAGE
  13#include <linux/module.h>
  14#include <linux/fscache-cache.h>
  15#include <linux/buffer_head.h>
  16#include <linux/pagevec.h>
  17#include <linux/slab.h>
  18#include "internal.h"
  19
  20/*
  21 * check to see if a page is being written to the cache
  22 */
  23bool __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}
  33EXPORT_SYMBOL(__fscache_check_page_write);
  34
  35/*
  36 * wait for a page to finish being written to the cache
  37 */
  38void __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}
  44EXPORT_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 */
  50bool __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
 106page_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}
 113EXPORT_SYMBOL(__fscache_maybe_release_page);
 114
 115/*
 116 * note that a page has finished being written to the cache
 117 */
 118static 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 */
 148static 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 */
 171int __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
 207nobufs:
 208        spin_unlock(&cookie->lock);
 209        kfree(op);
 210        fscache_stat(&fscache_n_attr_changed_nobufs);
 211        _leave(" = %d", -ENOBUFS);
 212        return -ENOBUFS;
 213}
 214EXPORT_SYMBOL(__fscache_attr_changed);
 215
 216/*
 217 * release a retrieval op reference
 218 */
 219static 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 */
 236static 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 */
 263static 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 */
 296static 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
 322check_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 */
 339int __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
 412error:
 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
 428nobufs_unlock:
 429        spin_unlock(&cookie->lock);
 430        kfree(op);
 431nobufs:
 432        fscache_stat(&fscache_n_retrievals_nobufs);
 433        _leave(" = -ENOBUFS");
 434        return -ENOBUFS;
 435}
 436EXPORT_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 */
 456int __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
 528error:
 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
 544nobufs_unlock:
 545        spin_unlock(&cookie->lock);
 546        kfree(op);
 547nobufs:
 548        fscache_stat(&fscache_n_retrievals_nobufs);
 549        _leave(" = -ENOBUFS");
 550        return -ENOBUFS;
 551}
 552EXPORT_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 */
 562int __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
 612error:
 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
 624nobufs_unlock:
 625        spin_unlock(&cookie->lock);
 626        kfree(op);
 627nobufs:
 628        fscache_stat(&fscache_n_allocs_nobufs);
 629        _leave(" = -ENOBUFS");
 630        return -ENOBUFS;
 631}
 632EXPORT_SYMBOL(__fscache_alloc_page);
 633
 634/*
 635 * release a write op reference
 636 */
 637static 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 */
 645static 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
 706superseded:
 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 */
 747int __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
 827already_queued:
 828        fscache_stat(&fscache_n_stores_again);
 829already_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
 839submit_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
 847nobufs_unlock_obj:
 848        spin_unlock(&cookie->stores_lock);
 849        spin_unlock(&object->lock);
 850nobufs:
 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
 858nomem_free:
 859        kfree(op);
 860nomem:
 861        fscache_stat(&fscache_n_stores_oom);
 862        _leave(" = -ENOMEM");
 863        return -ENOMEM;
 864}
 865EXPORT_SYMBOL(__fscache_write_page);
 866
 867/*
 868 * remove a page from the cache
 869 */
 870void __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
 910done_unlock:
 911        spin_unlock(&cookie->lock);
 912done:
 913        _leave("");
 914}
 915EXPORT_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 */
 925void 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}
 956EXPORT_SYMBOL(fscache_mark_pages_cached);
 957
 958/*
 959 * Uncache all the pages in an inode that are marked PG_fscache, assuming them
 960 * to be associated with the given cookie.
 961 */
 962void __fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
 963                                       struct inode *inode)
 964{
 965        struct address_space *mapping = inode->i_mapping;
 966        struct pagevec pvec;
 967        pgoff_t next;
 968        int i;
 969
 970        _enter("%p,%p", cookie, inode);
 971
 972        if (!mapping || mapping->nrpages == 0) {
 973                _leave(" [no pages]");
 974                return;
 975        }
 976
 977        pagevec_init(&pvec, 0);
 978        next = 0;
 979        do {
 980                if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE))
 981                        break;
 982                for (i = 0; i < pagevec_count(&pvec); i++) {
 983                        struct page *page = pvec.pages[i];
 984                        next = page->index;
 985                        if (PageFsCache(page)) {
 986                                __fscache_wait_on_page_write(cookie, page);
 987                                __fscache_uncache_page(cookie, page);
 988                        }
 989                }
 990                pagevec_release(&pvec);
 991                cond_resched();
 992        } while (++next);
 993
 994        _leave("");
 995}
 996EXPORT_SYMBOL(__fscache_uncache_all_inode_pages);
 997
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