linux/fs/fscache/object.c
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   1/* FS-Cache object state machine handler
   2 *
   3 * Copyright (C) 2007 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 * See Documentation/filesystems/caching/object.txt for a description of the
  12 * object state machine and the in-kernel representations.
  13 */
  14
  15#define FSCACHE_DEBUG_LEVEL COOKIE
  16#include <linux/module.h>
  17#include "internal.h"
  18
  19const char *fscache_object_states[FSCACHE_OBJECT__NSTATES] = {
  20        [FSCACHE_OBJECT_INIT]           = "OBJECT_INIT",
  21        [FSCACHE_OBJECT_LOOKING_UP]     = "OBJECT_LOOKING_UP",
  22        [FSCACHE_OBJECT_CREATING]       = "OBJECT_CREATING",
  23        [FSCACHE_OBJECT_AVAILABLE]      = "OBJECT_AVAILABLE",
  24        [FSCACHE_OBJECT_ACTIVE]         = "OBJECT_ACTIVE",
  25        [FSCACHE_OBJECT_UPDATING]       = "OBJECT_UPDATING",
  26        [FSCACHE_OBJECT_DYING]          = "OBJECT_DYING",
  27        [FSCACHE_OBJECT_LC_DYING]       = "OBJECT_LC_DYING",
  28        [FSCACHE_OBJECT_ABORT_INIT]     = "OBJECT_ABORT_INIT",
  29        [FSCACHE_OBJECT_RELEASING]      = "OBJECT_RELEASING",
  30        [FSCACHE_OBJECT_RECYCLING]      = "OBJECT_RECYCLING",
  31        [FSCACHE_OBJECT_WITHDRAWING]    = "OBJECT_WITHDRAWING",
  32        [FSCACHE_OBJECT_DEAD]           = "OBJECT_DEAD",
  33};
  34EXPORT_SYMBOL(fscache_object_states);
  35
  36const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5] = {
  37        [FSCACHE_OBJECT_INIT]           = "INIT",
  38        [FSCACHE_OBJECT_LOOKING_UP]     = "LOOK",
  39        [FSCACHE_OBJECT_CREATING]       = "CRTN",
  40        [FSCACHE_OBJECT_AVAILABLE]      = "AVBL",
  41        [FSCACHE_OBJECT_ACTIVE]         = "ACTV",
  42        [FSCACHE_OBJECT_UPDATING]       = "UPDT",
  43        [FSCACHE_OBJECT_DYING]          = "DYNG",
  44        [FSCACHE_OBJECT_LC_DYING]       = "LCDY",
  45        [FSCACHE_OBJECT_ABORT_INIT]     = "ABTI",
  46        [FSCACHE_OBJECT_RELEASING]      = "RELS",
  47        [FSCACHE_OBJECT_RECYCLING]      = "RCYC",
  48        [FSCACHE_OBJECT_WITHDRAWING]    = "WTHD",
  49        [FSCACHE_OBJECT_DEAD]           = "DEAD",
  50};
  51
  52static int  fscache_get_object(struct fscache_object *);
  53static void fscache_put_object(struct fscache_object *);
  54static void fscache_initialise_object(struct fscache_object *);
  55static void fscache_lookup_object(struct fscache_object *);
  56static void fscache_object_available(struct fscache_object *);
  57static void fscache_release_object(struct fscache_object *);
  58static void fscache_withdraw_object(struct fscache_object *);
  59static void fscache_enqueue_dependents(struct fscache_object *);
  60static void fscache_dequeue_object(struct fscache_object *);
  61
  62/*
  63 * we need to notify the parent when an op completes that we had outstanding
  64 * upon it
  65 */
  66static inline void fscache_done_parent_op(struct fscache_object *object)
  67{
  68        struct fscache_object *parent = object->parent;
  69
  70        _enter("OBJ%x {OBJ%x,%x}",
  71               object->debug_id, parent->debug_id, parent->n_ops);
  72
  73        spin_lock_nested(&parent->lock, 1);
  74        parent->n_ops--;
  75        parent->n_obj_ops--;
  76        if (parent->n_ops == 0)
  77                fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
  78        spin_unlock(&parent->lock);
  79}
  80
  81/*
  82 * process events that have been sent to an object's state machine
  83 * - initiates parent lookup
  84 * - does object lookup
  85 * - does object creation
  86 * - does object recycling and retirement
  87 * - does object withdrawal
  88 */
  89static void fscache_object_state_machine(struct fscache_object *object)
  90{
  91        enum fscache_object_state new_state;
  92        struct fscache_cookie *cookie;
  93
  94        ASSERT(object != NULL);
  95
  96        _enter("{OBJ%x,%s,%lx}",
  97               object->debug_id, fscache_object_states[object->state],
  98               object->events);
  99
 100        switch (object->state) {
 101                /* wait for the parent object to become ready */
 102        case FSCACHE_OBJECT_INIT:
 103                object->event_mask =
 104                        ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
 105                fscache_initialise_object(object);
 106                goto done;
 107
 108                /* look up the object metadata on disk */
 109        case FSCACHE_OBJECT_LOOKING_UP:
 110                fscache_lookup_object(object);
 111                goto lookup_transit;
 112
 113                /* create the object metadata on disk */
 114        case FSCACHE_OBJECT_CREATING:
 115                fscache_lookup_object(object);
 116                goto lookup_transit;
 117
 118                /* handle an object becoming available; start pending
 119                 * operations and queue dependent operations for processing */
 120        case FSCACHE_OBJECT_AVAILABLE:
 121                fscache_object_available(object);
 122                goto active_transit;
 123
 124                /* normal running state */
 125        case FSCACHE_OBJECT_ACTIVE:
 126                goto active_transit;
 127
 128                /* update the object metadata on disk */
 129        case FSCACHE_OBJECT_UPDATING:
 130                clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
 131                fscache_stat(&fscache_n_updates_run);
 132                fscache_stat(&fscache_n_cop_update_object);
 133                object->cache->ops->update_object(object);
 134                fscache_stat_d(&fscache_n_cop_update_object);
 135                goto active_transit;
 136
 137                /* handle an object dying during lookup or creation */
 138        case FSCACHE_OBJECT_LC_DYING:
 139                object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 140                fscache_stat(&fscache_n_cop_lookup_complete);
 141                object->cache->ops->lookup_complete(object);
 142                fscache_stat_d(&fscache_n_cop_lookup_complete);
 143
 144                spin_lock(&object->lock);
 145                object->state = FSCACHE_OBJECT_DYING;
 146                cookie = object->cookie;
 147                if (cookie) {
 148                        if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP,
 149                                               &cookie->flags))
 150                                wake_up_bit(&cookie->flags,
 151                                            FSCACHE_COOKIE_LOOKING_UP);
 152                        if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 153                                               &cookie->flags))
 154                                wake_up_bit(&cookie->flags,
 155                                            FSCACHE_COOKIE_CREATING);
 156                }
 157                spin_unlock(&object->lock);
 158
 159                fscache_done_parent_op(object);
 160
 161                /* wait for completion of all active operations on this object
 162                 * and the death of all child objects of this object */
 163        case FSCACHE_OBJECT_DYING:
 164        dying:
 165                clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
 166                spin_lock(&object->lock);
 167                _debug("dying OBJ%x {%d,%d}",
 168                       object->debug_id, object->n_ops, object->n_children);
 169                if (object->n_ops == 0 && object->n_children == 0) {
 170                        object->event_mask &=
 171                                ~(1 << FSCACHE_OBJECT_EV_CLEARED);
 172                        object->event_mask |=
 173                                (1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 174                                (1 << FSCACHE_OBJECT_EV_RETIRE) |
 175                                (1 << FSCACHE_OBJECT_EV_RELEASE) |
 176                                (1 << FSCACHE_OBJECT_EV_ERROR);
 177                } else {
 178                        object->event_mask &=
 179                                ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 180                                  (1 << FSCACHE_OBJECT_EV_RETIRE) |
 181                                  (1 << FSCACHE_OBJECT_EV_RELEASE) |
 182                                  (1 << FSCACHE_OBJECT_EV_ERROR));
 183                        object->event_mask |=
 184                                1 << FSCACHE_OBJECT_EV_CLEARED;
 185                }
 186                spin_unlock(&object->lock);
 187                fscache_enqueue_dependents(object);
 188                fscache_start_operations(object);
 189                goto terminal_transit;
 190
 191                /* handle an abort during initialisation */
 192        case FSCACHE_OBJECT_ABORT_INIT:
 193                _debug("handle abort init %lx", object->events);
 194                object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 195
 196                spin_lock(&object->lock);
 197                fscache_dequeue_object(object);
 198
 199                object->state = FSCACHE_OBJECT_DYING;
 200                if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 201                                       &object->cookie->flags))
 202                        wake_up_bit(&object->cookie->flags,
 203                                    FSCACHE_COOKIE_CREATING);
 204                spin_unlock(&object->lock);
 205                goto dying;
 206
 207                /* handle the netfs releasing an object and possibly marking it
 208                 * obsolete too */
 209        case FSCACHE_OBJECT_RELEASING:
 210        case FSCACHE_OBJECT_RECYCLING:
 211                object->event_mask &=
 212                        ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 213                          (1 << FSCACHE_OBJECT_EV_RETIRE) |
 214                          (1 << FSCACHE_OBJECT_EV_RELEASE) |
 215                          (1 << FSCACHE_OBJECT_EV_ERROR));
 216                fscache_release_object(object);
 217                spin_lock(&object->lock);
 218                object->state = FSCACHE_OBJECT_DEAD;
 219                spin_unlock(&object->lock);
 220                fscache_stat(&fscache_n_object_dead);
 221                goto terminal_transit;
 222
 223                /* handle the parent cache of this object being withdrawn from
 224                 * active service */
 225        case FSCACHE_OBJECT_WITHDRAWING:
 226                object->event_mask &=
 227                        ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 228                          (1 << FSCACHE_OBJECT_EV_RETIRE) |
 229                          (1 << FSCACHE_OBJECT_EV_RELEASE) |
 230                          (1 << FSCACHE_OBJECT_EV_ERROR));
 231                fscache_withdraw_object(object);
 232                spin_lock(&object->lock);
 233                object->state = FSCACHE_OBJECT_DEAD;
 234                spin_unlock(&object->lock);
 235                fscache_stat(&fscache_n_object_dead);
 236                goto terminal_transit;
 237
 238                /* complain about the object being woken up once it is
 239                 * deceased */
 240        case FSCACHE_OBJECT_DEAD:
 241                printk(KERN_ERR "FS-Cache:"
 242                       " Unexpected event in dead state %lx\n",
 243                       object->events & object->event_mask);
 244                BUG();
 245
 246        default:
 247                printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
 248                       object->state);
 249                BUG();
 250        }
 251
 252        /* determine the transition from a lookup state */
 253lookup_transit:
 254        switch (fls(object->events & object->event_mask) - 1) {
 255        case FSCACHE_OBJECT_EV_WITHDRAW:
 256        case FSCACHE_OBJECT_EV_RETIRE:
 257        case FSCACHE_OBJECT_EV_RELEASE:
 258        case FSCACHE_OBJECT_EV_ERROR:
 259                new_state = FSCACHE_OBJECT_LC_DYING;
 260                goto change_state;
 261        case FSCACHE_OBJECT_EV_REQUEUE:
 262                goto done;
 263        case -1:
 264                goto done; /* sleep until event */
 265        default:
 266                goto unsupported_event;
 267        }
 268
 269        /* determine the transition from an active state */
 270active_transit:
 271        switch (fls(object->events & object->event_mask) - 1) {
 272        case FSCACHE_OBJECT_EV_WITHDRAW:
 273        case FSCACHE_OBJECT_EV_RETIRE:
 274        case FSCACHE_OBJECT_EV_RELEASE:
 275        case FSCACHE_OBJECT_EV_ERROR:
 276                new_state = FSCACHE_OBJECT_DYING;
 277                goto change_state;
 278        case FSCACHE_OBJECT_EV_UPDATE:
 279                new_state = FSCACHE_OBJECT_UPDATING;
 280                goto change_state;
 281        case -1:
 282                new_state = FSCACHE_OBJECT_ACTIVE;
 283                goto change_state; /* sleep until event */
 284        default:
 285                goto unsupported_event;
 286        }
 287
 288        /* determine the transition from a terminal state */
 289terminal_transit:
 290        switch (fls(object->events & object->event_mask) - 1) {
 291        case FSCACHE_OBJECT_EV_WITHDRAW:
 292                new_state = FSCACHE_OBJECT_WITHDRAWING;
 293                goto change_state;
 294        case FSCACHE_OBJECT_EV_RETIRE:
 295                new_state = FSCACHE_OBJECT_RECYCLING;
 296                goto change_state;
 297        case FSCACHE_OBJECT_EV_RELEASE:
 298                new_state = FSCACHE_OBJECT_RELEASING;
 299                goto change_state;
 300        case FSCACHE_OBJECT_EV_ERROR:
 301                new_state = FSCACHE_OBJECT_WITHDRAWING;
 302                goto change_state;
 303        case FSCACHE_OBJECT_EV_CLEARED:
 304                new_state = FSCACHE_OBJECT_DYING;
 305                goto change_state;
 306        case -1:
 307                goto done; /* sleep until event */
 308        default:
 309                goto unsupported_event;
 310        }
 311
 312change_state:
 313        spin_lock(&object->lock);
 314        object->state = new_state;
 315        spin_unlock(&object->lock);
 316
 317done:
 318        _leave(" [->%s]", fscache_object_states[object->state]);
 319        return;
 320
 321unsupported_event:
 322        printk(KERN_ERR "FS-Cache:"
 323               " Unsupported event %lx [mask %lx] in state %s\n",
 324               object->events, object->event_mask,
 325               fscache_object_states[object->state]);
 326        BUG();
 327}
 328
 329/*
 330 * execute an object
 331 */
 332void fscache_object_work_func(struct work_struct *work)
 333{
 334        struct fscache_object *object =
 335                container_of(work, struct fscache_object, work);
 336        unsigned long start;
 337
 338        _enter("{OBJ%x}", object->debug_id);
 339
 340        start = jiffies;
 341        fscache_object_state_machine(object);
 342        fscache_hist(fscache_objs_histogram, start);
 343        if (object->events & object->event_mask)
 344                fscache_enqueue_object(object);
 345        clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 346        fscache_put_object(object);
 347}
 348EXPORT_SYMBOL(fscache_object_work_func);
 349
 350/*
 351 * initialise an object
 352 * - check the specified object's parent to see if we can make use of it
 353 *   immediately to do a creation
 354 * - we may need to start the process of creating a parent and we need to wait
 355 *   for the parent's lookup and creation to complete if it's not there yet
 356 * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 357 *   leaf-most cookies of the object and all its children
 358 */
 359static void fscache_initialise_object(struct fscache_object *object)
 360{
 361        struct fscache_object *parent;
 362
 363        _enter("");
 364        ASSERT(object->cookie != NULL);
 365        ASSERT(object->cookie->parent != NULL);
 366
 367        if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
 368                              (1 << FSCACHE_OBJECT_EV_RELEASE) |
 369                              (1 << FSCACHE_OBJECT_EV_RETIRE) |
 370                              (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
 371                _debug("abort init %lx", object->events);
 372                spin_lock(&object->lock);
 373                object->state = FSCACHE_OBJECT_ABORT_INIT;
 374                spin_unlock(&object->lock);
 375                return;
 376        }
 377
 378        spin_lock(&object->cookie->lock);
 379        spin_lock_nested(&object->cookie->parent->lock, 1);
 380
 381        parent = object->parent;
 382        if (!parent) {
 383                _debug("no parent");
 384                set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 385        } else {
 386                spin_lock(&object->lock);
 387                spin_lock_nested(&parent->lock, 1);
 388                _debug("parent %s", fscache_object_states[parent->state]);
 389
 390                if (parent->state >= FSCACHE_OBJECT_DYING) {
 391                        _debug("bad parent");
 392                        set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 393                } else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
 394                        _debug("wait");
 395
 396                        /* we may get woken up in this state by child objects
 397                         * binding on to us, so we need to make sure we don't
 398                         * add ourself to the list multiple times */
 399                        if (list_empty(&object->dep_link)) {
 400                                fscache_stat(&fscache_n_cop_grab_object);
 401                                object->cache->ops->grab_object(object);
 402                                fscache_stat_d(&fscache_n_cop_grab_object);
 403                                list_add(&object->dep_link,
 404                                         &parent->dependents);
 405
 406                                /* fscache_acquire_non_index_cookie() uses this
 407                                 * to wake the chain up */
 408                                if (parent->state == FSCACHE_OBJECT_INIT)
 409                                        fscache_enqueue_object(parent);
 410                        }
 411                } else {
 412                        _debug("go");
 413                        parent->n_ops++;
 414                        parent->n_obj_ops++;
 415                        object->lookup_jif = jiffies;
 416                        object->state = FSCACHE_OBJECT_LOOKING_UP;
 417                        set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 418                }
 419
 420                spin_unlock(&parent->lock);
 421                spin_unlock(&object->lock);
 422        }
 423
 424        spin_unlock(&object->cookie->parent->lock);
 425        spin_unlock(&object->cookie->lock);
 426        _leave("");
 427}
 428
 429/*
 430 * look an object up in the cache from which it was allocated
 431 * - we hold an "access lock" on the parent object, so the parent object cannot
 432 *   be withdrawn by either party till we've finished
 433 * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 434 *   leaf-most cookies of the object and all its children
 435 */
 436static void fscache_lookup_object(struct fscache_object *object)
 437{
 438        struct fscache_cookie *cookie = object->cookie;
 439        struct fscache_object *parent;
 440        int ret;
 441
 442        _enter("");
 443
 444        parent = object->parent;
 445        ASSERT(parent != NULL);
 446        ASSERTCMP(parent->n_ops, >, 0);
 447        ASSERTCMP(parent->n_obj_ops, >, 0);
 448
 449        /* make sure the parent is still available */
 450        ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
 451
 452        if (parent->state >= FSCACHE_OBJECT_DYING ||
 453            test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 454                _debug("unavailable");
 455                set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 456                _leave("");
 457                return;
 458        }
 459
 460        _debug("LOOKUP \"%s/%s\" in \"%s\"",
 461               parent->cookie->def->name, cookie->def->name,
 462               object->cache->tag->name);
 463
 464        fscache_stat(&fscache_n_object_lookups);
 465        fscache_stat(&fscache_n_cop_lookup_object);
 466        ret = object->cache->ops->lookup_object(object);
 467        fscache_stat_d(&fscache_n_cop_lookup_object);
 468
 469        if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
 470                set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 471
 472        if (ret == -ETIMEDOUT) {
 473                /* probably stuck behind another object, so move this one to
 474                 * the back of the queue */
 475                fscache_stat(&fscache_n_object_lookups_timed_out);
 476                set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 477        }
 478
 479        _leave("");
 480}
 481
 482/**
 483 * fscache_object_lookup_negative - Note negative cookie lookup
 484 * @object: Object pointing to cookie to mark
 485 *
 486 * Note negative lookup, permitting those waiting to read data from an already
 487 * existing backing object to continue as there's no data for them to read.
 488 */
 489void fscache_object_lookup_negative(struct fscache_object *object)
 490{
 491        struct fscache_cookie *cookie = object->cookie;
 492
 493        _enter("{OBJ%x,%s}",
 494               object->debug_id, fscache_object_states[object->state]);
 495
 496        spin_lock(&object->lock);
 497        if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 498                fscache_stat(&fscache_n_object_lookups_negative);
 499
 500                /* transit here to allow write requests to begin stacking up
 501                 * and read requests to begin returning ENODATA */
 502                object->state = FSCACHE_OBJECT_CREATING;
 503                spin_unlock(&object->lock);
 504
 505                set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
 506                set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 507
 508                _debug("wake up lookup %p", &cookie->flags);
 509                smp_mb__before_clear_bit();
 510                clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 511                smp_mb__after_clear_bit();
 512                wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 513                set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 514        } else {
 515                ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 516                spin_unlock(&object->lock);
 517        }
 518
 519        _leave("");
 520}
 521EXPORT_SYMBOL(fscache_object_lookup_negative);
 522
 523/**
 524 * fscache_obtained_object - Note successful object lookup or creation
 525 * @object: Object pointing to cookie to mark
 526 *
 527 * Note successful lookup and/or creation, permitting those waiting to write
 528 * data to a backing object to continue.
 529 *
 530 * Note that after calling this, an object's cookie may be relinquished by the
 531 * netfs, and so must be accessed with object lock held.
 532 */
 533void fscache_obtained_object(struct fscache_object *object)
 534{
 535        struct fscache_cookie *cookie = object->cookie;
 536
 537        _enter("{OBJ%x,%s}",
 538               object->debug_id, fscache_object_states[object->state]);
 539
 540        /* if we were still looking up, then we must have a positive lookup
 541         * result, in which case there may be data available */
 542        spin_lock(&object->lock);
 543        if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 544                fscache_stat(&fscache_n_object_lookups_positive);
 545
 546                clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 547
 548                object->state = FSCACHE_OBJECT_AVAILABLE;
 549                spin_unlock(&object->lock);
 550
 551                smp_mb__before_clear_bit();
 552                clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 553                smp_mb__after_clear_bit();
 554                wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 555                set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 556        } else {
 557                ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 558                fscache_stat(&fscache_n_object_created);
 559
 560                object->state = FSCACHE_OBJECT_AVAILABLE;
 561                spin_unlock(&object->lock);
 562                set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 563                smp_wmb();
 564        }
 565
 566        if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
 567                wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 568
 569        _leave("");
 570}
 571EXPORT_SYMBOL(fscache_obtained_object);
 572
 573/*
 574 * handle an object that has just become available
 575 */
 576static void fscache_object_available(struct fscache_object *object)
 577{
 578        _enter("{OBJ%x}", object->debug_id);
 579
 580        spin_lock(&object->lock);
 581
 582        if (object->cookie &&
 583            test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
 584                wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
 585
 586        fscache_done_parent_op(object);
 587        if (object->n_in_progress == 0) {
 588                if (object->n_ops > 0) {
 589                        ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 590                        ASSERTIF(object->n_ops > object->n_obj_ops,
 591                                 !list_empty(&object->pending_ops));
 592                        fscache_start_operations(object);
 593                } else {
 594                        ASSERT(list_empty(&object->pending_ops));
 595                }
 596        }
 597        spin_unlock(&object->lock);
 598
 599        fscache_stat(&fscache_n_cop_lookup_complete);
 600        object->cache->ops->lookup_complete(object);
 601        fscache_stat_d(&fscache_n_cop_lookup_complete);
 602        fscache_enqueue_dependents(object);
 603
 604        fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 605        fscache_stat(&fscache_n_object_avail);
 606
 607        _leave("");
 608}
 609
 610/*
 611 * drop an object's attachments
 612 */
 613static void fscache_drop_object(struct fscache_object *object)
 614{
 615        struct fscache_object *parent = object->parent;
 616        struct fscache_cache *cache = object->cache;
 617
 618        _enter("{OBJ%x,%d}", object->debug_id, object->n_children);
 619
 620        ASSERTCMP(object->cookie, ==, NULL);
 621        ASSERT(hlist_unhashed(&object->cookie_link));
 622
 623        spin_lock(&cache->object_list_lock);
 624        list_del_init(&object->cache_link);
 625        spin_unlock(&cache->object_list_lock);
 626
 627        fscache_stat(&fscache_n_cop_drop_object);
 628        cache->ops->drop_object(object);
 629        fscache_stat_d(&fscache_n_cop_drop_object);
 630
 631        if (parent) {
 632                _debug("release parent OBJ%x {%d}",
 633                       parent->debug_id, parent->n_children);
 634
 635                spin_lock(&parent->lock);
 636                parent->n_children--;
 637                if (parent->n_children == 0)
 638                        fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 639                spin_unlock(&parent->lock);
 640                object->parent = NULL;
 641        }
 642
 643        /* this just shifts the object release to the work processor */
 644        fscache_put_object(object);
 645
 646        _leave("");
 647}
 648
 649/*
 650 * release or recycle an object that the netfs has discarded
 651 */
 652static void fscache_release_object(struct fscache_object *object)
 653{
 654        _enter("");
 655
 656        fscache_drop_object(object);
 657}
 658
 659/*
 660 * withdraw an object from active service
 661 */
 662static void fscache_withdraw_object(struct fscache_object *object)
 663{
 664        struct fscache_cookie *cookie;
 665        bool detached;
 666
 667        _enter("");
 668
 669        spin_lock(&object->lock);
 670        cookie = object->cookie;
 671        if (cookie) {
 672                /* need to get the cookie lock before the object lock, starting
 673                 * from the object pointer */
 674                atomic_inc(&cookie->usage);
 675                spin_unlock(&object->lock);
 676
 677                detached = false;
 678                spin_lock(&cookie->lock);
 679                spin_lock(&object->lock);
 680
 681                if (object->cookie == cookie) {
 682                        hlist_del_init(&object->cookie_link);
 683                        object->cookie = NULL;
 684                        detached = true;
 685                }
 686                spin_unlock(&cookie->lock);
 687                fscache_cookie_put(cookie);
 688                if (detached)
 689                        fscache_cookie_put(cookie);
 690        }
 691
 692        spin_unlock(&object->lock);
 693
 694        fscache_drop_object(object);
 695}
 696
 697/*
 698 * withdraw an object from active service at the behest of the cache
 699 * - need break the links to a cached object cookie
 700 * - called under two situations:
 701 *   (1) recycler decides to reclaim an in-use object
 702 *   (2) a cache is unmounted
 703 * - have to take care as the cookie can be being relinquished by the netfs
 704 *   simultaneously
 705 * - the object is pinned by the caller holding a refcount on it
 706 */
 707void fscache_withdrawing_object(struct fscache_cache *cache,
 708                                struct fscache_object *object)
 709{
 710        bool enqueue = false;
 711
 712        _enter(",OBJ%x", object->debug_id);
 713
 714        spin_lock(&object->lock);
 715        if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
 716                object->state = FSCACHE_OBJECT_WITHDRAWING;
 717                enqueue = true;
 718        }
 719        spin_unlock(&object->lock);
 720
 721        if (enqueue)
 722                fscache_enqueue_object(object);
 723
 724        _leave("");
 725}
 726
 727/*
 728 * get a ref on an object
 729 */
 730static int fscache_get_object(struct fscache_object *object)
 731{
 732        int ret;
 733
 734        fscache_stat(&fscache_n_cop_grab_object);
 735        ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 736        fscache_stat_d(&fscache_n_cop_grab_object);
 737        return ret;
 738}
 739
 740/*
 741 * discard a ref on a work item
 742 */
 743static void fscache_put_object(struct fscache_object *object)
 744{
 745        fscache_stat(&fscache_n_cop_put_object);
 746        object->cache->ops->put_object(object);
 747        fscache_stat_d(&fscache_n_cop_put_object);
 748}
 749
 750/*
 751 * enqueue an object for metadata-type processing
 752 */
 753void fscache_enqueue_object(struct fscache_object *object)
 754{
 755        _enter("{OBJ%x}", object->debug_id);
 756
 757        if (fscache_get_object(object) >= 0) {
 758                wait_queue_head_t *cong_wq =
 759                        &get_cpu_var(fscache_object_cong_wait);
 760
 761                if (queue_work(fscache_object_wq, &object->work)) {
 762                        if (fscache_object_congested())
 763                                wake_up(cong_wq);
 764                } else
 765                        fscache_put_object(object);
 766
 767                put_cpu_var(fscache_object_cong_wait);
 768        }
 769}
 770
 771/**
 772 * fscache_object_sleep_till_congested - Sleep until object wq is congested
 773 * @timoutp: Scheduler sleep timeout
 774 *
 775 * Allow an object handler to sleep until the object workqueue is congested.
 776 *
 777 * The caller must set up a wake up event before calling this and must have set
 778 * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 779 * condition before calling this function as no test is made here.
 780 *
 781 * %true is returned if the object wq is congested, %false otherwise.
 782 */
 783bool fscache_object_sleep_till_congested(signed long *timeoutp)
 784{
 785        wait_queue_head_t *cong_wq = &__get_cpu_var(fscache_object_cong_wait);
 786        DEFINE_WAIT(wait);
 787
 788        if (fscache_object_congested())
 789                return true;
 790
 791        add_wait_queue_exclusive(cong_wq, &wait);
 792        if (!fscache_object_congested())
 793                *timeoutp = schedule_timeout(*timeoutp);
 794        finish_wait(cong_wq, &wait);
 795
 796        return fscache_object_congested();
 797}
 798EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 799
 800/*
 801 * enqueue the dependents of an object for metadata-type processing
 802 * - the caller must hold the object's lock
 803 * - this may cause an already locked object to wind up being processed again
 804 */
 805static void fscache_enqueue_dependents(struct fscache_object *object)
 806{
 807        struct fscache_object *dep;
 808
 809        _enter("{OBJ%x}", object->debug_id);
 810
 811        if (list_empty(&object->dependents))
 812                return;
 813
 814        spin_lock(&object->lock);
 815
 816        while (!list_empty(&object->dependents)) {
 817                dep = list_entry(object->dependents.next,
 818                                 struct fscache_object, dep_link);
 819                list_del_init(&dep->dep_link);
 820
 821
 822                /* sort onto appropriate lists */
 823                fscache_enqueue_object(dep);
 824                fscache_put_object(dep);
 825
 826                if (!list_empty(&object->dependents))
 827                        cond_resched_lock(&object->lock);
 828        }
 829
 830        spin_unlock(&object->lock);
 831}
 832
 833/*
 834 * remove an object from whatever queue it's waiting on
 835 * - the caller must hold object->lock
 836 */
 837void fscache_dequeue_object(struct fscache_object *object)
 838{
 839        _enter("{OBJ%x}", object->debug_id);
 840
 841        if (!list_empty(&object->dep_link)) {
 842                spin_lock(&object->parent->lock);
 843                list_del_init(&object->dep_link);
 844                spin_unlock(&object->parent->lock);
 845        }
 846
 847        _leave("");
 848}
 849
 850/**
 851 * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 852 * @object: The object to ask about
 853 * @data: The auxiliary data for the object
 854 * @datalen: The size of the auxiliary data
 855 *
 856 * This function consults the netfs about the coherency state of an object
 857 */
 858enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 859                                        const void *data, uint16_t datalen)
 860{
 861        enum fscache_checkaux result;
 862
 863        if (!object->cookie->def->check_aux) {
 864                fscache_stat(&fscache_n_checkaux_none);
 865                return FSCACHE_CHECKAUX_OKAY;
 866        }
 867
 868        result = object->cookie->def->check_aux(object->cookie->netfs_data,
 869                                                data, datalen);
 870        switch (result) {
 871                /* entry okay as is */
 872        case FSCACHE_CHECKAUX_OKAY:
 873                fscache_stat(&fscache_n_checkaux_okay);
 874                break;
 875
 876                /* entry requires update */
 877        case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 878                fscache_stat(&fscache_n_checkaux_update);
 879                break;
 880
 881                /* entry requires deletion */
 882        case FSCACHE_CHECKAUX_OBSOLETE:
 883                fscache_stat(&fscache_n_checkaux_obsolete);
 884                break;
 885
 886        default:
 887                BUG();
 888        }
 889
 890        return result;
 891}
 892EXPORT_SYMBOL(fscache_check_aux);
 893
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