linux/fs/fscache/page.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/* Cache page management and data I/O routines
   3 *
   4 * Copyright (C) 2004-2008 Red Hat, Inc. All Rights Reserved.
   5 * Written by David Howells (dhowells@redhat.com)
   6 */
   7
   8#define FSCACHE_DEBUG_LEVEL PAGE
   9#include <linux/module.h>
  10#include <linux/fscache-cache.h>
  11#include <linux/buffer_head.h>
  12#include <linux/pagevec.h>
  13#include <linux/slab.h>
  14#include "internal.h"
  15
  16/*
  17 * check to see if a page is being written to the cache
  18 */
  19bool __fscache_check_page_write(struct fscache_cookie *cookie, struct page *page)
  20{
  21        void *val;
  22
  23        rcu_read_lock();
  24        val = radix_tree_lookup(&cookie->stores, page->index);
  25        rcu_read_unlock();
  26        trace_fscache_check_page(cookie, page, val, 0);
  27
  28        return val != NULL;
  29}
  30EXPORT_SYMBOL(__fscache_check_page_write);
  31
  32/*
  33 * wait for a page to finish being written to the cache
  34 */
  35void __fscache_wait_on_page_write(struct fscache_cookie *cookie, struct page *page)
  36{
  37        wait_queue_head_t *wq = bit_waitqueue(&cookie->flags, 0);
  38
  39        trace_fscache_page(cookie, page, fscache_page_write_wait);
  40
  41        wait_event(*wq, !__fscache_check_page_write(cookie, page));
  42}
  43EXPORT_SYMBOL(__fscache_wait_on_page_write);
  44
  45/*
  46 * wait for a page to finish being written to the cache. Put a timeout here
  47 * since we might be called recursively via parent fs.
  48 */
  49static
  50bool release_page_wait_timeout(struct fscache_cookie *cookie, struct page *page)
  51{
  52        wait_queue_head_t *wq = bit_waitqueue(&cookie->flags, 0);
  53
  54        return wait_event_timeout(*wq, !__fscache_check_page_write(cookie, page),
  55                                  HZ);
  56}
  57
  58/*
  59 * decide whether a page can be released, possibly by cancelling a store to it
  60 * - we're allowed to sleep if __GFP_DIRECT_RECLAIM is flagged
  61 */
  62bool __fscache_maybe_release_page(struct fscache_cookie *cookie,
  63                                  struct page *page,
  64                                  gfp_t gfp)
  65{
  66        struct page *xpage;
  67        void *val;
  68
  69        _enter("%p,%p,%x", cookie, page, gfp);
  70
  71        trace_fscache_page(cookie, page, fscache_page_maybe_release);
  72
  73try_again:
  74        rcu_read_lock();
  75        val = radix_tree_lookup(&cookie->stores, page->index);
  76        if (!val) {
  77                rcu_read_unlock();
  78                fscache_stat(&fscache_n_store_vmscan_not_storing);
  79                __fscache_uncache_page(cookie, page);
  80                return true;
  81        }
  82
  83        /* see if the page is actually undergoing storage - if so we can't get
  84         * rid of it till the cache has finished with it */
  85        if (radix_tree_tag_get(&cookie->stores, page->index,
  86                               FSCACHE_COOKIE_STORING_TAG)) {
  87                rcu_read_unlock();
  88                goto page_busy;
  89        }
  90
  91        /* the page is pending storage, so we attempt to cancel the store and
  92         * discard the store request so that the page can be reclaimed */
  93        spin_lock(&cookie->stores_lock);
  94        rcu_read_unlock();
  95
  96        if (radix_tree_tag_get(&cookie->stores, page->index,
  97                               FSCACHE_COOKIE_STORING_TAG)) {
  98                /* the page started to undergo storage whilst we were looking,
  99                 * so now we can only wait or return */
 100                spin_unlock(&cookie->stores_lock);
 101                goto page_busy;
 102        }
 103
 104        xpage = radix_tree_delete(&cookie->stores, page->index);
 105        trace_fscache_page(cookie, page, fscache_page_radix_delete);
 106        spin_unlock(&cookie->stores_lock);
 107
 108        if (xpage) {
 109                fscache_stat(&fscache_n_store_vmscan_cancelled);
 110                fscache_stat(&fscache_n_store_radix_deletes);
 111                ASSERTCMP(xpage, ==, page);
 112        } else {
 113                fscache_stat(&fscache_n_store_vmscan_gone);
 114        }
 115
 116        wake_up_bit(&cookie->flags, 0);
 117        trace_fscache_wake_cookie(cookie);
 118        if (xpage)
 119                put_page(xpage);
 120        __fscache_uncache_page(cookie, page);
 121        return true;
 122
 123page_busy:
 124        /* We will wait here if we're allowed to, but that could deadlock the
 125         * allocator as the work threads writing to the cache may all end up
 126         * sleeping on memory allocation, so we may need to impose a timeout
 127         * too. */
 128        if (!(gfp & __GFP_DIRECT_RECLAIM) || !(gfp & __GFP_FS)) {
 129                fscache_stat(&fscache_n_store_vmscan_busy);
 130                return false;
 131        }
 132
 133        fscache_stat(&fscache_n_store_vmscan_wait);
 134        if (!release_page_wait_timeout(cookie, page))
 135                _debug("fscache writeout timeout page: %p{%lx}",
 136                        page, page->index);
 137
 138        gfp &= ~__GFP_DIRECT_RECLAIM;
 139        goto try_again;
 140}
 141EXPORT_SYMBOL(__fscache_maybe_release_page);
 142
 143/*
 144 * note that a page has finished being written to the cache
 145 */
 146static void fscache_end_page_write(struct fscache_object *object,
 147                                   struct page *page)
 148{
 149        struct fscache_cookie *cookie;
 150        struct page *xpage = NULL, *val;
 151
 152        spin_lock(&object->lock);
 153        cookie = object->cookie;
 154        if (cookie) {
 155                /* delete the page from the tree if it is now no longer
 156                 * pending */
 157                spin_lock(&cookie->stores_lock);
 158                radix_tree_tag_clear(&cookie->stores, page->index,
 159                                     FSCACHE_COOKIE_STORING_TAG);
 160                trace_fscache_page(cookie, page, fscache_page_radix_clear_store);
 161                if (!radix_tree_tag_get(&cookie->stores, page->index,
 162                                        FSCACHE_COOKIE_PENDING_TAG)) {
 163                        fscache_stat(&fscache_n_store_radix_deletes);
 164                        xpage = radix_tree_delete(&cookie->stores, page->index);
 165                        trace_fscache_page(cookie, page, fscache_page_radix_delete);
 166                        trace_fscache_page(cookie, page, fscache_page_write_end);
 167
 168                        val = radix_tree_lookup(&cookie->stores, page->index);
 169                        trace_fscache_check_page(cookie, page, val, 1);
 170                } else {
 171                        trace_fscache_page(cookie, page, fscache_page_write_end_pend);
 172                }
 173                spin_unlock(&cookie->stores_lock);
 174                wake_up_bit(&cookie->flags, 0);
 175                trace_fscache_wake_cookie(cookie);
 176        } else {
 177                trace_fscache_page(cookie, page, fscache_page_write_end_noc);
 178        }
 179        spin_unlock(&object->lock);
 180        if (xpage)
 181                put_page(xpage);
 182}
 183
 184/*
 185 * actually apply the changed attributes to a cache object
 186 */
 187static void fscache_attr_changed_op(struct fscache_operation *op)
 188{
 189        struct fscache_object *object = op->object;
 190        int ret;
 191
 192        _enter("{OBJ%x OP%x}", object->debug_id, op->debug_id);
 193
 194        fscache_stat(&fscache_n_attr_changed_calls);
 195
 196        if (fscache_object_is_active(object)) {
 197                fscache_stat(&fscache_n_cop_attr_changed);
 198                ret = object->cache->ops->attr_changed(object);
 199                fscache_stat_d(&fscache_n_cop_attr_changed);
 200                if (ret < 0)
 201                        fscache_abort_object(object);
 202                fscache_op_complete(op, ret < 0);
 203        } else {
 204                fscache_op_complete(op, true);
 205        }
 206
 207        _leave("");
 208}
 209
 210/*
 211 * notification that the attributes on an object have changed
 212 */
 213int __fscache_attr_changed(struct fscache_cookie *cookie)
 214{
 215        struct fscache_operation *op;
 216        struct fscache_object *object;
 217        bool wake_cookie = false;
 218
 219        _enter("%p", cookie);
 220
 221        ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 222
 223        fscache_stat(&fscache_n_attr_changed);
 224
 225        op = kzalloc(sizeof(*op), GFP_KERNEL);
 226        if (!op) {
 227                fscache_stat(&fscache_n_attr_changed_nomem);
 228                _leave(" = -ENOMEM");
 229                return -ENOMEM;
 230        }
 231
 232        fscache_operation_init(cookie, op, fscache_attr_changed_op, NULL, NULL);
 233        trace_fscache_page_op(cookie, NULL, op, fscache_page_op_attr_changed);
 234        op->flags = FSCACHE_OP_ASYNC |
 235                (1 << FSCACHE_OP_EXCLUSIVE) |
 236                (1 << FSCACHE_OP_UNUSE_COOKIE);
 237
 238        spin_lock(&cookie->lock);
 239
 240        if (!fscache_cookie_enabled(cookie) ||
 241            hlist_empty(&cookie->backing_objects))
 242                goto nobufs;
 243        object = hlist_entry(cookie->backing_objects.first,
 244                             struct fscache_object, cookie_link);
 245
 246        __fscache_use_cookie(cookie);
 247        if (fscache_submit_exclusive_op(object, op) < 0)
 248                goto nobufs_dec;
 249        spin_unlock(&cookie->lock);
 250        fscache_stat(&fscache_n_attr_changed_ok);
 251        fscache_put_operation(op);
 252        _leave(" = 0");
 253        return 0;
 254
 255nobufs_dec:
 256        wake_cookie = __fscache_unuse_cookie(cookie);
 257nobufs:
 258        spin_unlock(&cookie->lock);
 259        fscache_put_operation(op);
 260        if (wake_cookie)
 261                __fscache_wake_unused_cookie(cookie);
 262        fscache_stat(&fscache_n_attr_changed_nobufs);
 263        _leave(" = %d", -ENOBUFS);
 264        return -ENOBUFS;
 265}
 266EXPORT_SYMBOL(__fscache_attr_changed);
 267
 268/*
 269 * Handle cancellation of a pending retrieval op
 270 */
 271static void fscache_do_cancel_retrieval(struct fscache_operation *_op)
 272{
 273        struct fscache_retrieval *op =
 274                container_of(_op, struct fscache_retrieval, op);
 275
 276        atomic_set(&op->n_pages, 0);
 277}
 278
 279/*
 280 * release a retrieval op reference
 281 */
 282static void fscache_release_retrieval_op(struct fscache_operation *_op)
 283{
 284        struct fscache_retrieval *op =
 285                container_of(_op, struct fscache_retrieval, op);
 286
 287        _enter("{OP%x}", op->op.debug_id);
 288
 289        ASSERTIFCMP(op->op.state != FSCACHE_OP_ST_INITIALISED,
 290                    atomic_read(&op->n_pages), ==, 0);
 291
 292        fscache_hist(fscache_retrieval_histogram, op->start_time);
 293        if (op->context)
 294                fscache_put_context(op->cookie, op->context);
 295
 296        _leave("");
 297}
 298
 299/*
 300 * allocate a retrieval op
 301 */
 302struct fscache_retrieval *fscache_alloc_retrieval(
 303        struct fscache_cookie *cookie,
 304        struct address_space *mapping,
 305        fscache_rw_complete_t end_io_func,
 306        void *context)
 307{
 308        struct fscache_retrieval *op;
 309
 310        /* allocate a retrieval operation and attempt to submit it */
 311        op = kzalloc(sizeof(*op), GFP_NOIO);
 312        if (!op) {
 313                fscache_stat(&fscache_n_retrievals_nomem);
 314                return NULL;
 315        }
 316
 317        fscache_operation_init(cookie, &op->op, NULL,
 318                               fscache_do_cancel_retrieval,
 319                               fscache_release_retrieval_op);
 320        op->op.flags    = FSCACHE_OP_MYTHREAD |
 321                (1UL << FSCACHE_OP_WAITING) |
 322                (1UL << FSCACHE_OP_UNUSE_COOKIE);
 323        op->cookie      = cookie;
 324        op->mapping     = mapping;
 325        op->end_io_func = end_io_func;
 326        op->context     = context;
 327        op->start_time  = jiffies;
 328        INIT_LIST_HEAD(&op->to_do);
 329
 330        /* Pin the netfs read context in case we need to do the actual netfs
 331         * read because we've encountered a cache read failure.
 332         */
 333        if (context)
 334                fscache_get_context(op->cookie, context);
 335        return op;
 336}
 337
 338/*
 339 * wait for a deferred lookup to complete
 340 */
 341int fscache_wait_for_deferred_lookup(struct fscache_cookie *cookie)
 342{
 343        unsigned long jif;
 344
 345        _enter("");
 346
 347        if (!test_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags)) {
 348                _leave(" = 0 [imm]");
 349                return 0;
 350        }
 351
 352        fscache_stat(&fscache_n_retrievals_wait);
 353
 354        jif = jiffies;
 355        if (wait_on_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP,
 356                        TASK_INTERRUPTIBLE) != 0) {
 357                fscache_stat(&fscache_n_retrievals_intr);
 358                _leave(" = -ERESTARTSYS");
 359                return -ERESTARTSYS;
 360        }
 361
 362        ASSERT(!test_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags));
 363
 364        smp_rmb();
 365        fscache_hist(fscache_retrieval_delay_histogram, jif);
 366        _leave(" = 0 [dly]");
 367        return 0;
 368}
 369
 370/*
 371 * wait for an object to become active (or dead)
 372 */
 373int fscache_wait_for_operation_activation(struct fscache_object *object,
 374                                          struct fscache_operation *op,
 375                                          atomic_t *stat_op_waits,
 376                                          atomic_t *stat_object_dead)
 377{
 378        int ret;
 379
 380        if (!test_bit(FSCACHE_OP_WAITING, &op->flags))
 381                goto check_if_dead;
 382
 383        _debug(">>> WT");
 384        if (stat_op_waits)
 385                fscache_stat(stat_op_waits);
 386        if (wait_on_bit(&op->flags, FSCACHE_OP_WAITING,
 387                        TASK_INTERRUPTIBLE) != 0) {
 388                trace_fscache_op(object->cookie, op, fscache_op_signal);
 389                ret = fscache_cancel_op(op, false);
 390                if (ret == 0)
 391                        return -ERESTARTSYS;
 392
 393                /* it's been removed from the pending queue by another party,
 394                 * so we should get to run shortly */
 395                wait_on_bit(&op->flags, FSCACHE_OP_WAITING,
 396                            TASK_UNINTERRUPTIBLE);
 397        }
 398        _debug("<<< GO");
 399
 400check_if_dead:
 401        if (op->state == FSCACHE_OP_ST_CANCELLED) {
 402                if (stat_object_dead)
 403                        fscache_stat(stat_object_dead);
 404                _leave(" = -ENOBUFS [cancelled]");
 405                return -ENOBUFS;
 406        }
 407        if (unlikely(fscache_object_is_dying(object) ||
 408                     fscache_cache_is_broken(object))) {
 409                enum fscache_operation_state state = op->state;
 410                trace_fscache_op(object->cookie, op, fscache_op_signal);
 411                fscache_cancel_op(op, true);
 412                if (stat_object_dead)
 413                        fscache_stat(stat_object_dead);
 414                _leave(" = -ENOBUFS [obj dead %d]", state);
 415                return -ENOBUFS;
 416        }
 417        return 0;
 418}
 419
 420/*
 421 * read a page from the cache or allocate a block in which to store it
 422 * - we return:
 423 *   -ENOMEM    - out of memory, nothing done
 424 *   -ERESTARTSYS - interrupted
 425 *   -ENOBUFS   - no backing object available in which to cache the block
 426 *   -ENODATA   - no data available in the backing object for this block
 427 *   0          - dispatched a read - it'll call end_io_func() when finished
 428 */
 429int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 430                                 struct page *page,
 431                                 fscache_rw_complete_t end_io_func,
 432                                 void *context,
 433                                 gfp_t gfp)
 434{
 435        struct fscache_retrieval *op;
 436        struct fscache_object *object;
 437        bool wake_cookie = false;
 438        int ret;
 439
 440        _enter("%p,%p,,,", cookie, page);
 441
 442        fscache_stat(&fscache_n_retrievals);
 443
 444        if (hlist_empty(&cookie->backing_objects))
 445                goto nobufs;
 446
 447        if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
 448                _leave(" = -ENOBUFS [invalidating]");
 449                return -ENOBUFS;
 450        }
 451
 452        ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 453        ASSERTCMP(page, !=, NULL);
 454
 455        if (fscache_wait_for_deferred_lookup(cookie) < 0)
 456                return -ERESTARTSYS;
 457
 458        op = fscache_alloc_retrieval(cookie, page->mapping,
 459                                     end_io_func, context);
 460        if (!op) {
 461                _leave(" = -ENOMEM");
 462                return -ENOMEM;
 463        }
 464        atomic_set(&op->n_pages, 1);
 465        trace_fscache_page_op(cookie, page, &op->op, fscache_page_op_retr_one);
 466
 467        spin_lock(&cookie->lock);
 468
 469        if (!fscache_cookie_enabled(cookie) ||
 470            hlist_empty(&cookie->backing_objects))
 471                goto nobufs_unlock;
 472        object = hlist_entry(cookie->backing_objects.first,
 473                             struct fscache_object, cookie_link);
 474
 475        ASSERT(test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags));
 476
 477        __fscache_use_cookie(cookie);
 478        atomic_inc(&object->n_reads);
 479        __set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
 480
 481        if (fscache_submit_op(object, &op->op) < 0)
 482                goto nobufs_unlock_dec;
 483        spin_unlock(&cookie->lock);
 484
 485        fscache_stat(&fscache_n_retrieval_ops);
 486
 487        /* we wait for the operation to become active, and then process it
 488         * *here*, in this thread, and not in the thread pool */
 489        ret = fscache_wait_for_operation_activation(
 490                object, &op->op,
 491                __fscache_stat(&fscache_n_retrieval_op_waits),
 492                __fscache_stat(&fscache_n_retrievals_object_dead));
 493        if (ret < 0)
 494                goto error;
 495
 496        /* ask the cache to honour the operation */
 497        if (test_bit(FSCACHE_COOKIE_NO_DATA_YET, &object->cookie->flags)) {
 498                fscache_stat(&fscache_n_cop_allocate_page);
 499                ret = object->cache->ops->allocate_page(op, page, gfp);
 500                fscache_stat_d(&fscache_n_cop_allocate_page);
 501                if (ret == 0)
 502                        ret = -ENODATA;
 503        } else {
 504                fscache_stat(&fscache_n_cop_read_or_alloc_page);
 505                ret = object->cache->ops->read_or_alloc_page(op, page, gfp);
 506                fscache_stat_d(&fscache_n_cop_read_or_alloc_page);
 507        }
 508
 509error:
 510        if (ret == -ENOMEM)
 511                fscache_stat(&fscache_n_retrievals_nomem);
 512        else if (ret == -ERESTARTSYS)
 513                fscache_stat(&fscache_n_retrievals_intr);
 514        else if (ret == -ENODATA)
 515                fscache_stat(&fscache_n_retrievals_nodata);
 516        else if (ret < 0)
 517                fscache_stat(&fscache_n_retrievals_nobufs);
 518        else
 519                fscache_stat(&fscache_n_retrievals_ok);
 520
 521        fscache_put_retrieval(op);
 522        _leave(" = %d", ret);
 523        return ret;
 524
 525nobufs_unlock_dec:
 526        atomic_dec(&object->n_reads);
 527        wake_cookie = __fscache_unuse_cookie(cookie);
 528nobufs_unlock:
 529        spin_unlock(&cookie->lock);
 530        if (wake_cookie)
 531                __fscache_wake_unused_cookie(cookie);
 532        fscache_put_retrieval(op);
 533nobufs:
 534        fscache_stat(&fscache_n_retrievals_nobufs);
 535        _leave(" = -ENOBUFS");
 536        return -ENOBUFS;
 537}
 538EXPORT_SYMBOL(__fscache_read_or_alloc_page);
 539
 540/*
 541 * read a list of page from the cache or allocate a block in which to store
 542 * them
 543 * - we return:
 544 *   -ENOMEM    - out of memory, some pages may be being read
 545 *   -ERESTARTSYS - interrupted, some pages may be being read
 546 *   -ENOBUFS   - no backing object or space available in which to cache any
 547 *                pages not being read
 548 *   -ENODATA   - no data available in the backing object for some or all of
 549 *                the pages
 550 *   0          - dispatched a read on all pages
 551 *
 552 * end_io_func() will be called for each page read from the cache as it is
 553 * finishes being read
 554 *
 555 * any pages for which a read is dispatched will be removed from pages and
 556 * nr_pages
 557 */
 558int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
 559                                  struct address_space *mapping,
 560                                  struct list_head *pages,
 561                                  unsigned *nr_pages,
 562                                  fscache_rw_complete_t end_io_func,
 563                                  void *context,
 564                                  gfp_t gfp)
 565{
 566        struct fscache_retrieval *op;
 567        struct fscache_object *object;
 568        bool wake_cookie = false;
 569        int ret;
 570
 571        _enter("%p,,%d,,,", cookie, *nr_pages);
 572
 573        fscache_stat(&fscache_n_retrievals);
 574
 575        if (hlist_empty(&cookie->backing_objects))
 576                goto nobufs;
 577
 578        if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
 579                _leave(" = -ENOBUFS [invalidating]");
 580                return -ENOBUFS;
 581        }
 582
 583        ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 584        ASSERTCMP(*nr_pages, >, 0);
 585        ASSERT(!list_empty(pages));
 586
 587        if (fscache_wait_for_deferred_lookup(cookie) < 0)
 588                return -ERESTARTSYS;
 589
 590        op = fscache_alloc_retrieval(cookie, mapping, end_io_func, context);
 591        if (!op)
 592                return -ENOMEM;
 593        atomic_set(&op->n_pages, *nr_pages);
 594        trace_fscache_page_op(cookie, NULL, &op->op, fscache_page_op_retr_multi);
 595
 596        spin_lock(&cookie->lock);
 597
 598        if (!fscache_cookie_enabled(cookie) ||
 599            hlist_empty(&cookie->backing_objects))
 600                goto nobufs_unlock;
 601        object = hlist_entry(cookie->backing_objects.first,
 602                             struct fscache_object, cookie_link);
 603
 604        __fscache_use_cookie(cookie);
 605        atomic_inc(&object->n_reads);
 606        __set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
 607
 608        if (fscache_submit_op(object, &op->op) < 0)
 609                goto nobufs_unlock_dec;
 610        spin_unlock(&cookie->lock);
 611
 612        fscache_stat(&fscache_n_retrieval_ops);
 613
 614        /* we wait for the operation to become active, and then process it
 615         * *here*, in this thread, and not in the thread pool */
 616        ret = fscache_wait_for_operation_activation(
 617                object, &op->op,
 618                __fscache_stat(&fscache_n_retrieval_op_waits),
 619                __fscache_stat(&fscache_n_retrievals_object_dead));
 620        if (ret < 0)
 621                goto error;
 622
 623        /* ask the cache to honour the operation */
 624        if (test_bit(FSCACHE_COOKIE_NO_DATA_YET, &object->cookie->flags)) {
 625                fscache_stat(&fscache_n_cop_allocate_pages);
 626                ret = object->cache->ops->allocate_pages(
 627                        op, pages, nr_pages, gfp);
 628                fscache_stat_d(&fscache_n_cop_allocate_pages);
 629        } else {
 630                fscache_stat(&fscache_n_cop_read_or_alloc_pages);
 631                ret = object->cache->ops->read_or_alloc_pages(
 632                        op, pages, nr_pages, gfp);
 633                fscache_stat_d(&fscache_n_cop_read_or_alloc_pages);
 634        }
 635
 636error:
 637        if (ret == -ENOMEM)
 638                fscache_stat(&fscache_n_retrievals_nomem);
 639        else if (ret == -ERESTARTSYS)
 640                fscache_stat(&fscache_n_retrievals_intr);
 641        else if (ret == -ENODATA)
 642                fscache_stat(&fscache_n_retrievals_nodata);
 643        else if (ret < 0)
 644                fscache_stat(&fscache_n_retrievals_nobufs);
 645        else
 646                fscache_stat(&fscache_n_retrievals_ok);
 647
 648        fscache_put_retrieval(op);
 649        _leave(" = %d", ret);
 650        return ret;
 651
 652nobufs_unlock_dec:
 653        atomic_dec(&object->n_reads);
 654        wake_cookie = __fscache_unuse_cookie(cookie);
 655nobufs_unlock:
 656        spin_unlock(&cookie->lock);
 657        fscache_put_retrieval(op);
 658        if (wake_cookie)
 659                __fscache_wake_unused_cookie(cookie);
 660nobufs:
 661        fscache_stat(&fscache_n_retrievals_nobufs);
 662        _leave(" = -ENOBUFS");
 663        return -ENOBUFS;
 664}
 665EXPORT_SYMBOL(__fscache_read_or_alloc_pages);
 666
 667/*
 668 * allocate a block in the cache on which to store a page
 669 * - we return:
 670 *   -ENOMEM    - out of memory, nothing done
 671 *   -ERESTARTSYS - interrupted
 672 *   -ENOBUFS   - no backing object available in which to cache the block
 673 *   0          - block allocated
 674 */
 675int __fscache_alloc_page(struct fscache_cookie *cookie,
 676                         struct page *page,
 677                         gfp_t gfp)
 678{
 679        struct fscache_retrieval *op;
 680        struct fscache_object *object;
 681        bool wake_cookie = false;
 682        int ret;
 683
 684        _enter("%p,%p,,,", cookie, page);
 685
 686        fscache_stat(&fscache_n_allocs);
 687
 688        if (hlist_empty(&cookie->backing_objects))
 689                goto nobufs;
 690
 691        ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 692        ASSERTCMP(page, !=, NULL);
 693
 694        if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
 695                _leave(" = -ENOBUFS [invalidating]");
 696                return -ENOBUFS;
 697        }
 698
 699        if (fscache_wait_for_deferred_lookup(cookie) < 0)
 700                return -ERESTARTSYS;
 701
 702        op = fscache_alloc_retrieval(cookie, page->mapping, NULL, NULL);
 703        if (!op)
 704                return -ENOMEM;
 705        atomic_set(&op->n_pages, 1);
 706        trace_fscache_page_op(cookie, page, &op->op, fscache_page_op_alloc_one);
 707
 708        spin_lock(&cookie->lock);
 709
 710        if (!fscache_cookie_enabled(cookie) ||
 711            hlist_empty(&cookie->backing_objects))
 712                goto nobufs_unlock;
 713        object = hlist_entry(cookie->backing_objects.first,
 714                             struct fscache_object, cookie_link);
 715
 716        __fscache_use_cookie(cookie);
 717        if (fscache_submit_op(object, &op->op) < 0)
 718                goto nobufs_unlock_dec;
 719        spin_unlock(&cookie->lock);
 720
 721        fscache_stat(&fscache_n_alloc_ops);
 722
 723        ret = fscache_wait_for_operation_activation(
 724                object, &op->op,
 725                __fscache_stat(&fscache_n_alloc_op_waits),
 726                __fscache_stat(&fscache_n_allocs_object_dead));
 727        if (ret < 0)
 728                goto error;
 729
 730        /* ask the cache to honour the operation */
 731        fscache_stat(&fscache_n_cop_allocate_page);
 732        ret = object->cache->ops->allocate_page(op, page, gfp);
 733        fscache_stat_d(&fscache_n_cop_allocate_page);
 734
 735error:
 736        if (ret == -ERESTARTSYS)
 737                fscache_stat(&fscache_n_allocs_intr);
 738        else if (ret < 0)
 739                fscache_stat(&fscache_n_allocs_nobufs);
 740        else
 741                fscache_stat(&fscache_n_allocs_ok);
 742
 743        fscache_put_retrieval(op);
 744        _leave(" = %d", ret);
 745        return ret;
 746
 747nobufs_unlock_dec:
 748        wake_cookie = __fscache_unuse_cookie(cookie);
 749nobufs_unlock:
 750        spin_unlock(&cookie->lock);
 751        fscache_put_retrieval(op);
 752        if (wake_cookie)
 753                __fscache_wake_unused_cookie(cookie);
 754nobufs:
 755        fscache_stat(&fscache_n_allocs_nobufs);
 756        _leave(" = -ENOBUFS");
 757        return -ENOBUFS;
 758}
 759EXPORT_SYMBOL(__fscache_alloc_page);
 760
 761/*
 762 * Unmark pages allocate in the readahead code path (via:
 763 * fscache_readpages_or_alloc) after delegating to the base filesystem
 764 */
 765void __fscache_readpages_cancel(struct fscache_cookie *cookie,
 766                                struct list_head *pages)
 767{
 768        struct page *page;
 769
 770        list_for_each_entry(page, pages, lru) {
 771                if (PageFsCache(page))
 772                        __fscache_uncache_page(cookie, page);
 773        }
 774}
 775EXPORT_SYMBOL(__fscache_readpages_cancel);
 776
 777/*
 778 * release a write op reference
 779 */
 780static void fscache_release_write_op(struct fscache_operation *_op)
 781{
 782        _enter("{OP%x}", _op->debug_id);
 783}
 784
 785/*
 786 * perform the background storage of a page into the cache
 787 */
 788static void fscache_write_op(struct fscache_operation *_op)
 789{
 790        struct fscache_storage *op =
 791                container_of(_op, struct fscache_storage, op);
 792        struct fscache_object *object = op->op.object;
 793        struct fscache_cookie *cookie;
 794        struct page *page;
 795        unsigned n;
 796        void *results[1];
 797        int ret;
 798
 799        _enter("{OP%x,%d}", op->op.debug_id, atomic_read(&op->op.usage));
 800
 801again:
 802        spin_lock(&object->lock);
 803        cookie = object->cookie;
 804
 805        if (!fscache_object_is_active(object)) {
 806                /* If we get here, then the on-disk cache object likely no
 807                 * longer exists, so we should just cancel this write
 808                 * operation.
 809                 */
 810                spin_unlock(&object->lock);
 811                fscache_op_complete(&op->op, true);
 812                _leave(" [inactive]");
 813                return;
 814        }
 815
 816        if (!cookie) {
 817                /* If we get here, then the cookie belonging to the object was
 818                 * detached, probably by the cookie being withdrawn due to
 819                 * memory pressure, which means that the pages we might write
 820                 * to the cache from no longer exist - therefore, we can just
 821                 * cancel this write operation.
 822                 */
 823                spin_unlock(&object->lock);
 824                fscache_op_complete(&op->op, true);
 825                _leave(" [cancel] op{f=%lx s=%u} obj{s=%s f=%lx}",
 826                       _op->flags, _op->state, object->state->short_name,
 827                       object->flags);
 828                return;
 829        }
 830
 831        spin_lock(&cookie->stores_lock);
 832
 833        fscache_stat(&fscache_n_store_calls);
 834
 835        /* find a page to store */
 836        results[0] = NULL;
 837        page = NULL;
 838        n = radix_tree_gang_lookup_tag(&cookie->stores, results, 0, 1,
 839                                       FSCACHE_COOKIE_PENDING_TAG);
 840        trace_fscache_gang_lookup(cookie, &op->op, results, n, op->store_limit);
 841        if (n != 1)
 842                goto superseded;
 843        page = results[0];
 844        _debug("gang %d [%lx]", n, page->index);
 845
 846        radix_tree_tag_set(&cookie->stores, page->index,
 847                           FSCACHE_COOKIE_STORING_TAG);
 848        radix_tree_tag_clear(&cookie->stores, page->index,
 849                             FSCACHE_COOKIE_PENDING_TAG);
 850        trace_fscache_page(cookie, page, fscache_page_radix_pend2store);
 851
 852        spin_unlock(&cookie->stores_lock);
 853        spin_unlock(&object->lock);
 854
 855        if (page->index >= op->store_limit)
 856                goto discard_page;
 857
 858        fscache_stat(&fscache_n_store_pages);
 859        fscache_stat(&fscache_n_cop_write_page);
 860        ret = object->cache->ops->write_page(op, page);
 861        fscache_stat_d(&fscache_n_cop_write_page);
 862        trace_fscache_wrote_page(cookie, page, &op->op, ret);
 863        fscache_end_page_write(object, page);
 864        if (ret < 0) {
 865                fscache_abort_object(object);
 866                fscache_op_complete(&op->op, true);
 867        } else {
 868                fscache_enqueue_operation(&op->op);
 869        }
 870
 871        _leave("");
 872        return;
 873
 874discard_page:
 875        fscache_stat(&fscache_n_store_pages_over_limit);
 876        trace_fscache_wrote_page(cookie, page, &op->op, -ENOBUFS);
 877        fscache_end_page_write(object, page);
 878        goto again;
 879
 880superseded:
 881        /* this writer is going away and there aren't any more things to
 882         * write */
 883        _debug("cease");
 884        spin_unlock(&cookie->stores_lock);
 885        clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 886        spin_unlock(&object->lock);
 887        fscache_op_complete(&op->op, false);
 888        _leave("");
 889}
 890
 891/*
 892 * Clear the pages pending writing for invalidation
 893 */
 894void fscache_invalidate_writes(struct fscache_cookie *cookie)
 895{
 896        struct page *page;
 897        void *results[16];
 898        int n, i;
 899
 900        _enter("");
 901
 902        for (;;) {
 903                spin_lock(&cookie->stores_lock);
 904                n = radix_tree_gang_lookup_tag(&cookie->stores, results, 0,
 905                                               ARRAY_SIZE(results),
 906                                               FSCACHE_COOKIE_PENDING_TAG);
 907                if (n == 0) {
 908                        spin_unlock(&cookie->stores_lock);
 909                        break;
 910                }
 911
 912                for (i = n - 1; i >= 0; i--) {
 913                        page = results[i];
 914                        radix_tree_delete(&cookie->stores, page->index);
 915                        trace_fscache_page(cookie, page, fscache_page_radix_delete);
 916                        trace_fscache_page(cookie, page, fscache_page_inval);
 917                }
 918
 919                spin_unlock(&cookie->stores_lock);
 920
 921                for (i = n - 1; i >= 0; i--)
 922                        put_page(results[i]);
 923        }
 924
 925        wake_up_bit(&cookie->flags, 0);
 926        trace_fscache_wake_cookie(cookie);
 927
 928        _leave("");
 929}
 930
 931/*
 932 * request a page be stored in the cache
 933 * - returns:
 934 *   -ENOMEM    - out of memory, nothing done
 935 *   -ENOBUFS   - no backing object available in which to cache the page
 936 *   0          - dispatched a write - it'll call end_io_func() when finished
 937 *
 938 * if the cookie still has a backing object at this point, that object can be
 939 * in one of a few states with respect to storage processing:
 940 *
 941 *  (1) negative lookup, object not yet created (FSCACHE_COOKIE_CREATING is
 942 *      set)
 943 *
 944 *      (a) no writes yet
 945 *
 946 *      (b) writes deferred till post-creation (mark page for writing and
 947 *          return immediately)
 948 *
 949 *  (2) negative lookup, object created, initial fill being made from netfs
 950 *
 951 *      (a) fill point not yet reached this page (mark page for writing and
 952 *          return)
 953 *
 954 *      (b) fill point passed this page (queue op to store this page)
 955 *
 956 *  (3) object extant (queue op to store this page)
 957 *
 958 * any other state is invalid
 959 */
 960int __fscache_write_page(struct fscache_cookie *cookie,
 961                         struct page *page,
 962                         loff_t object_size,
 963                         gfp_t gfp)
 964{
 965        struct fscache_storage *op;
 966        struct fscache_object *object;
 967        bool wake_cookie = false;
 968        int ret;
 969
 970        _enter("%p,%x,", cookie, (u32) page->flags);
 971
 972        ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 973        ASSERT(PageFsCache(page));
 974
 975        fscache_stat(&fscache_n_stores);
 976
 977        if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
 978                _leave(" = -ENOBUFS [invalidating]");
 979                return -ENOBUFS;
 980        }
 981
 982        op = kzalloc(sizeof(*op), GFP_NOIO | __GFP_NOMEMALLOC | __GFP_NORETRY);
 983        if (!op)
 984                goto nomem;
 985
 986        fscache_operation_init(cookie, &op->op, fscache_write_op, NULL,
 987                               fscache_release_write_op);
 988        op->op.flags = FSCACHE_OP_ASYNC |
 989                (1 << FSCACHE_OP_WAITING) |
 990                (1 << FSCACHE_OP_UNUSE_COOKIE);
 991
 992        ret = radix_tree_maybe_preload(gfp & ~__GFP_HIGHMEM);
 993        if (ret < 0)
 994                goto nomem_free;
 995
 996        trace_fscache_page_op(cookie, page, &op->op, fscache_page_op_write_one);
 997
 998        ret = -ENOBUFS;
 999        spin_lock(&cookie->lock);
1000
1001        if (!fscache_cookie_enabled(cookie) ||
1002            hlist_empty(&cookie->backing_objects))
1003                goto nobufs;
1004        object = hlist_entry(cookie->backing_objects.first,
1005                             struct fscache_object, cookie_link);
1006        if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
1007                goto nobufs;
1008
1009        trace_fscache_page(cookie, page, fscache_page_write);
1010
1011        /* add the page to the pending-storage radix tree on the backing
1012         * object */
1013        spin_lock(&object->lock);
1014
1015        if (object->store_limit_l != object_size)
1016                fscache_set_store_limit(object, object_size);
1017
1018        spin_lock(&cookie->stores_lock);
1019
1020        _debug("store limit %llx", (unsigned long long) object->store_limit);
1021
1022        ret = radix_tree_insert(&cookie->stores, page->index, page);
1023        if (ret < 0) {
1024                if (ret == -EEXIST)
1025                        goto already_queued;
1026                _debug("insert failed %d", ret);
1027                goto nobufs_unlock_obj;
1028        }
1029
1030        trace_fscache_page(cookie, page, fscache_page_radix_insert);
1031        radix_tree_tag_set(&cookie->stores, page->index,
1032                           FSCACHE_COOKIE_PENDING_TAG);
1033        trace_fscache_page(cookie, page, fscache_page_radix_set_pend);
1034        get_page(page);
1035
1036        /* we only want one writer at a time, but we do need to queue new
1037         * writers after exclusive ops */
1038        if (test_and_set_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags))
1039                goto already_pending;
1040
1041        spin_unlock(&cookie->stores_lock);
1042        spin_unlock(&object->lock);
1043
1044        op->op.debug_id = atomic_inc_return(&fscache_op_debug_id);
1045        op->store_limit = object->store_limit;
1046
1047        __fscache_use_cookie(cookie);
1048        if (fscache_submit_op(object, &op->op) < 0)
1049                goto submit_failed;
1050
1051        spin_unlock(&cookie->lock);
1052        radix_tree_preload_end();
1053        fscache_stat(&fscache_n_store_ops);
1054        fscache_stat(&fscache_n_stores_ok);
1055
1056        /* the work queue now carries its own ref on the object */
1057        fscache_put_operation(&op->op);
1058        _leave(" = 0");
1059        return 0;
1060
1061already_queued:
1062        fscache_stat(&fscache_n_stores_again);
1063already_pending:
1064        spin_unlock(&cookie->stores_lock);
1065        spin_unlock(&object->lock);
1066        spin_unlock(&cookie->lock);
1067        radix_tree_preload_end();
1068        fscache_put_operation(&op->op);
1069        fscache_stat(&fscache_n_stores_ok);
1070        _leave(" = 0");
1071        return 0;
1072
1073submit_failed:
1074        spin_lock(&cookie->stores_lock);
1075        radix_tree_delete(&cookie->stores, page->index);
1076        trace_fscache_page(cookie, page, fscache_page_radix_delete);
1077        spin_unlock(&cookie->stores_lock);
1078        wake_cookie = __fscache_unuse_cookie(cookie);
1079        put_page(page);
1080        ret = -ENOBUFS;
1081        goto nobufs;
1082
1083nobufs_unlock_obj:
1084        spin_unlock(&cookie->stores_lock);
1085        spin_unlock(&object->lock);
1086nobufs:
1087        spin_unlock(&cookie->lock);
1088        radix_tree_preload_end();
1089        fscache_put_operation(&op->op);
1090        if (wake_cookie)
1091                __fscache_wake_unused_cookie(cookie);
1092        fscache_stat(&fscache_n_stores_nobufs);
1093        _leave(" = -ENOBUFS");
1094        return -ENOBUFS;
1095
1096nomem_free:
1097        fscache_put_operation(&op->op);
1098nomem:
1099        fscache_stat(&fscache_n_stores_oom);
1100        _leave(" = -ENOMEM");
1101        return -ENOMEM;
1102}
1103EXPORT_SYMBOL(__fscache_write_page);
1104
1105/*
1106 * remove a page from the cache
1107 */
1108void __fscache_uncache_page(struct fscache_cookie *cookie, struct page *page)
1109{
1110        struct fscache_object *object;
1111
1112        _enter(",%p", page);
1113
1114        ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
1115        ASSERTCMP(page, !=, NULL);
1116
1117        fscache_stat(&fscache_n_uncaches);
1118
1119        /* cache withdrawal may beat us to it */
1120        if (!PageFsCache(page))
1121                goto done;
1122
1123        trace_fscache_page(cookie, page, fscache_page_uncache);
1124
1125        /* get the object */
1126        spin_lock(&cookie->lock);
1127
1128        if (hlist_empty(&cookie->backing_objects)) {
1129                ClearPageFsCache(page);
1130                goto done_unlock;
1131        }
1132
1133        object = hlist_entry(cookie->backing_objects.first,
1134                             struct fscache_object, cookie_link);
1135
1136        /* there might now be stuff on disk we could read */
1137        clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
1138
1139        /* only invoke the cache backend if we managed to mark the page
1140         * uncached here; this deals with synchronisation vs withdrawal */
1141        if (TestClearPageFsCache(page) &&
1142            object->cache->ops->uncache_page) {
1143                /* the cache backend releases the cookie lock */
1144                fscache_stat(&fscache_n_cop_uncache_page);
1145                object->cache->ops->uncache_page(object, page);
1146                fscache_stat_d(&fscache_n_cop_uncache_page);
1147                goto done;
1148        }
1149
1150done_unlock:
1151        spin_unlock(&cookie->lock);
1152done:
1153        _leave("");
1154}
1155EXPORT_SYMBOL(__fscache_uncache_page);
1156
1157/**
1158 * fscache_mark_page_cached - Mark a page as being cached
1159 * @op: The retrieval op pages are being marked for
1160 * @page: The page to be marked
1161 *
1162 * Mark a netfs page as being cached.  After this is called, the netfs
1163 * must call fscache_uncache_page() to remove the mark.
1164 */
1165void fscache_mark_page_cached(struct fscache_retrieval *op, struct page *page)
1166{
1167        struct fscache_cookie *cookie = op->op.object->cookie;
1168
1169#ifdef CONFIG_FSCACHE_STATS
1170        atomic_inc(&fscache_n_marks);
1171#endif
1172
1173        trace_fscache_page(cookie, page, fscache_page_cached);
1174
1175        _debug("- mark %p{%lx}", page, page->index);
1176        if (TestSetPageFsCache(page)) {
1177                static bool once_only;
1178                if (!once_only) {
1179                        once_only = true;
1180                        pr_warn("Cookie type %s marked page %lx multiple times\n",
1181                                cookie->def->name, page->index);
1182                }
1183        }
1184
1185        if (cookie->def->mark_page_cached)
1186                cookie->def->mark_page_cached(cookie->netfs_data,
1187                                              op->mapping, page);
1188}
1189EXPORT_SYMBOL(fscache_mark_page_cached);
1190
1191/**
1192 * fscache_mark_pages_cached - Mark pages as being cached
1193 * @op: The retrieval op pages are being marked for
1194 * @pagevec: The pages to be marked
1195 *
1196 * Mark a bunch of netfs pages as being cached.  After this is called,
1197 * the netfs must call fscache_uncache_page() to remove the mark.
1198 */
1199void fscache_mark_pages_cached(struct fscache_retrieval *op,
1200                               struct pagevec *pagevec)
1201{
1202        unsigned long loop;
1203
1204        for (loop = 0; loop < pagevec->nr; loop++)
1205                fscache_mark_page_cached(op, pagevec->pages[loop]);
1206
1207        pagevec_reinit(pagevec);
1208}
1209EXPORT_SYMBOL(fscache_mark_pages_cached);
1210
1211/*
1212 * Uncache all the pages in an inode that are marked PG_fscache, assuming them
1213 * to be associated with the given cookie.
1214 */
1215void __fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
1216                                       struct inode *inode)
1217{
1218        struct address_space *mapping = inode->i_mapping;
1219        struct pagevec pvec;
1220        pgoff_t next;
1221        int i;
1222
1223        _enter("%p,%p", cookie, inode);
1224
1225        if (!mapping || mapping->nrpages == 0) {
1226                _leave(" [no pages]");
1227                return;
1228        }
1229
1230        pagevec_init(&pvec);
1231        next = 0;
1232        do {
1233                if (!pagevec_lookup(&pvec, mapping, &next))
1234                        break;
1235                for (i = 0; i < pagevec_count(&pvec); i++) {
1236                        struct page *page = pvec.pages[i];
1237                        if (PageFsCache(page)) {
1238                                __fscache_wait_on_page_write(cookie, page);
1239                                __fscache_uncache_page(cookie, page);
1240                        }
1241                }
1242                pagevec_release(&pvec);
1243                cond_resched();
1244        } while (next);
1245
1246        _leave("");
1247}
1248EXPORT_SYMBOL(__fscache_uncache_all_inode_pages);
1249