fs/fscache/object.c

   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 <linux/slab.h>
  18 #include <linux/prefetch.h>
  19 #include "internal.h"
  20
  21 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *, int);
  22 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *, int);
  23 static const struct fscache_state *fscache_drop_object(struct fscache_object *, int);
  24 static const struct fscache_state *fscache_initialise_object(struct fscache_object *, int);
  25 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *, int);
  26 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *, int);
  27 static const struct fscache_state *fscache_kill_object(struct fscache_object *, int);
  28 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *, int);
  29 static const struct fscache_state *fscache_look_up_object(struct fscache_object *, int);
  30 static const struct fscache_state *fscache_object_available(struct fscache_object *, int);
  31 static const struct fscache_state *fscache_parent_ready(struct fscache_object *, int);
  32 static const struct fscache_state *fscache_update_object(struct fscache_object *, int);
  33 static const struct fscache_state *fscache_detach_from_cookie(struct fscache_object *, int);
  34
  35 #define __STATE_NAME(n) fscache_osm_##n
  36 #define STATE(n) (&__STATE_NAME(n))
  37
  38 /*
  39  * Define a work state.  Work states are execution states.  No event processing
  40  * is performed by them.  The function attached to a work state returns a
  41  * pointer indicating the next state to which the state machine should
  42  * transition.  Returning NO_TRANSIT repeats the current state, but goes back
  43  * to the scheduler first.
  44  */
  45 #define WORK_STATE(n, sn, f) \
  46         const struct fscache_state __STATE_NAME(n) = {                  \
  47                 .name = #n,                                             \
  48                 .short_name = sn,                                       \
  49                 .work = f                                               \
  50         }
  51
  52 /*
  53  * Returns from work states.
  54  */
  55 #define transit_to(state) ({ prefetch(&STATE(state)->work); STATE(state); })
  56
  57 #define NO_TRANSIT ((struct fscache_state *)NULL)
  58
  59 /*
  60  * Define a wait state.  Wait states are event processing states.  No execution
  61  * is performed by them.  Wait states are just tables of "if event X occurs,
  62  * clear it and transition to state Y".  The dispatcher returns to the
  63  * scheduler if none of the events in which the wait state has an interest are
  64  * currently pending.
  65  */
  66 #define WAIT_STATE(n, sn, ...) \
  67         const struct fscache_state __STATE_NAME(n) = {                  \
  68                 .name = #n,                                             \
  69                 .short_name = sn,                                       \
  70                 .work = NULL,                                           \
  71                 .transitions = { __VA_ARGS__, { 0, NULL } }             \
  72         }
  73
  74 #define TRANSIT_TO(state, emask) \
  75         { .events = (emask), .transit_to = STATE(state) }
  76
  77 /*
  78  * The object state machine.
  79  */
  80 static WORK_STATE(INIT_OBJECT,          "INIT", fscache_initialise_object);
  81 static WORK_STATE(PARENT_READY,         "PRDY", fscache_parent_ready);
  82 static WORK_STATE(ABORT_INIT,           "ABRT", fscache_abort_initialisation);
  83 static WORK_STATE(LOOK_UP_OBJECT,       "LOOK", fscache_look_up_object);
  84 static WORK_STATE(CREATE_OBJECT,        "CRTO", fscache_look_up_object);
  85 static WORK_STATE(OBJECT_AVAILABLE,     "AVBL", fscache_object_available);
  86 static WORK_STATE(JUMPSTART_DEPS,       "JUMP", fscache_jumpstart_dependents);
  87
  88 static WORK_STATE(INVALIDATE_OBJECT,    "INVL", fscache_invalidate_object);
  89 static WORK_STATE(UPDATE_OBJECT,        "UPDT", fscache_update_object);
  90
  91 static WORK_STATE(LOOKUP_FAILURE,       "LCFL", fscache_lookup_failure);
  92 static WORK_STATE(KILL_OBJECT,          "KILL", fscache_kill_object);
  93 static WORK_STATE(KILL_DEPENDENTS,      "KDEP", fscache_kill_dependents);
  94 static WORK_STATE(DROP_OBJECT,          "DROP", fscache_drop_object);
  95 static WORK_STATE(DETACH_FROM_COOKIE,   "DTCH", fscache_detach_from_cookie);
  96 static WORK_STATE(OBJECT_DEAD,          "DEAD", (void*)2UL);
  97
  98 static WAIT_STATE(WAIT_FOR_INIT,        "?INI",
  99                   TRANSIT_TO(INIT_OBJECT,       1 << FSCACHE_OBJECT_EV_NEW_CHILD));
 100
 101 static WAIT_STATE(WAIT_FOR_PARENT,      "?PRN",
 102                   TRANSIT_TO(PARENT_READY,      1 << FSCACHE_OBJECT_EV_PARENT_READY));
 103
 104 static WAIT_STATE(WAIT_FOR_CMD,         "?CMD",
 105                   TRANSIT_TO(INVALIDATE_OBJECT, 1 << FSCACHE_OBJECT_EV_INVALIDATE),
 106                   TRANSIT_TO(UPDATE_OBJECT,     1 << FSCACHE_OBJECT_EV_UPDATE),
 107                   TRANSIT_TO(JUMPSTART_DEPS,    1 << FSCACHE_OBJECT_EV_NEW_CHILD));
 108
 109 static WAIT_STATE(WAIT_FOR_CLEARANCE,   "?CLR",
 110                   TRANSIT_TO(KILL_OBJECT,       1 << FSCACHE_OBJECT_EV_CLEARED));
 111
 112 /*
 113  * Out-of-band event transition tables.  These are for handling unexpected
 114  * events, such as an I/O error.  If an OOB event occurs, the state machine
 115  * clears and disables the event and forces a transition to the nominated work
 116  * state (acurrently executing work states will complete first).
 117  *
 118  * In such a situation, object->state remembers the state the machine should
 119  * have been in/gone to and returning NO_TRANSIT returns to that.
 120  */
 121 static const struct fscache_transition fscache_osm_init_oob[] = {
 122            TRANSIT_TO(ABORT_INIT,
 123                       (1 << FSCACHE_OBJECT_EV_ERROR) |
 124                       (1 << FSCACHE_OBJECT_EV_KILL)),
 125            { 0, NULL }
 126 };
 127
 128 static const struct fscache_transition fscache_osm_lookup_oob[] = {
 129            TRANSIT_TO(LOOKUP_FAILURE,
 130                       (1 << FSCACHE_OBJECT_EV_ERROR) |
 131                       (1 << FSCACHE_OBJECT_EV_KILL)),
 132            { 0, NULL }
 133 };
 134
 135 static const struct fscache_transition fscache_osm_run_oob[] = {
 136            TRANSIT_TO(KILL_OBJECT,
 137                       (1 << FSCACHE_OBJECT_EV_ERROR) |
 138                       (1 << FSCACHE_OBJECT_EV_KILL)),
 139            { 0, NULL }
 140 };
 141
 142 static int  fscache_get_object(struct fscache_object *);
 143 static void fscache_put_object(struct fscache_object *);
 144 static bool fscache_enqueue_dependents(struct fscache_object *, int);
 145 static void fscache_dequeue_object(struct fscache_object *);
 146
 147 /*
 148  * we need to notify the parent when an op completes that we had outstanding
 149  * upon it
 150  */
 151 static inline void fscache_done_parent_op(struct fscache_object *object)
 152 {
 153         struct fscache_object *parent = object->parent;
 154
 155         _enter("OBJ%x {OBJ%x,%x}",
 156                object->debug_id, parent->debug_id, parent->n_ops);
 157
 158         spin_lock_nested(&parent->lock, 1);
 159         parent->n_ops--;
 160         parent->n_obj_ops--;
 161         if (parent->n_ops == 0)
 162                 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 163         spin_unlock(&parent->lock);
 164 }
 165
 166 /*
 167  * Object state machine dispatcher.
 168  */
 169 static void fscache_object_sm_dispatcher(struct fscache_object *object)
 170 {
 171         const struct fscache_transition *t;
 172         const struct fscache_state *state, *new_state;
 173         unsigned long events, event_mask;
 174         int event = -1;
 175
 176         ASSERT(object != NULL);
 177
 178         _enter("{OBJ%x,%s,%lx}",
 179                object->debug_id, object->state->name, object->events);
 180
 181         event_mask = object->event_mask;
 182 restart:
 183         object->event_mask = 0; /* Mask normal event handling */
 184         state = object->state;
 185 restart_masked:
 186         events = object->events;
 187
 188         /* Handle any out-of-band events (typically an error) */
 189         if (events & object->oob_event_mask) {
 190                 _debug("{OBJ%x} oob %lx",
 191                        object->debug_id, events & object->oob_event_mask);
 192                 for (t = object->oob_table; t->events; t++) {
 193                         if (events & t->events) {
 194                                 state = t->transit_to;
 195                                 ASSERT(state->work != NULL);
 196                                 event = fls(events & t->events) - 1;
 197                                 __clear_bit(event, &object->oob_event_mask);
 198                                 clear_bit(event, &object->events);
 199                                 goto execute_work_state;
 200                         }
 201                 }
 202         }
 203
 204         /* Wait states are just transition tables */
 205         if (!state->work) {
 206                 if (events & event_mask) {
 207                         for (t = state->transitions; t->events; t++) {
 208                                 if (events & t->events) {
 209                                         new_state = t->transit_to;
 210                                         event = fls(events & t->events) - 1;
 211                                         clear_bit(event, &object->events);
 212                                         _debug("{OBJ%x} ev %d: %s -> %s",
 213                                                object->debug_id, event,
 214                                                state->name, new_state->name);
 215                                         object->state = state = new_state;
 216                                         goto execute_work_state;
 217                                 }
 218                         }
 219
 220                         /* The event mask didn't include all the tabled bits */
 221                         BUG();
 222                 }
 223                 /* Randomly woke up */
 224                 goto unmask_events;
 225         }
 226
 227 execute_work_state:
 228         _debug("{OBJ%x} exec %s", object->debug_id, state->name);
 229
 230         new_state = state->work(object, event);
 231         event = -1;
 232         if (new_state == NO_TRANSIT) {
 233                 _debug("{OBJ%x} %s notrans", object->debug_id, state->name);
 234                 fscache_enqueue_object(object);
 235                 event_mask = object->oob_event_mask;
 236                 goto unmask_events;
 237         }
 238
 239         _debug("{OBJ%x} %s -> %s",
 240                object->debug_id, state->name, new_state->name);
 241         object->state = state = new_state;
 242
 243         if (state->work) {
 244                 if (unlikely(state->work == ((void *)2UL))) {
 245                         _leave(" [dead]");
 246                         return;
 247                 }
 248                 goto restart_masked;
 249         }
 250
 251         /* Transited to wait state */
 252         event_mask = object->oob_event_mask;
 253         for (t = state->transitions; t->events; t++)
 254                 event_mask |= t->events;
 255
 256 unmask_events:
 257         object->event_mask = event_mask;
 258         smp_mb();
 259         events = object->events;
 260         if (events & event_mask)
 261                 goto restart;
 262         _leave(" [msk %lx]", event_mask);
 263 }
 264
 265 /*
 266  * execute an object
 267  */
 268 static void fscache_object_work_func(struct work_struct *work)
 269 {
 270         struct fscache_object *object =
 271                 container_of(work, struct fscache_object, work);
 272         unsigned long start;
 273
 274         _enter("{OBJ%x}", object->debug_id);
 275
 276         start = jiffies;
 277         fscache_object_sm_dispatcher(object);
 278         fscache_hist(fscache_objs_histogram, start);
 279         fscache_put_object(object);
 280 }
 281
 282 /**
 283  * fscache_object_init - Initialise a cache object description
 284  * @object: Object description
 285  * @cookie: Cookie object will be attached to
 286  * @cache: Cache in which backing object will be found
 287  *
 288  * Initialise a cache object description to its basic values.
 289  *
 290  * See Documentation/filesystems/caching/backend-api.txt for a complete
 291  * description.
 292  */
 293 void fscache_object_init(struct fscache_object *object,
 294                          struct fscache_cookie *cookie,
 295                          struct fscache_cache *cache)
 296 {
 297         const struct fscache_transition *t;
 298
 299         atomic_inc(&cache->object_count);
 300
 301         object->state = STATE(WAIT_FOR_INIT);
 302         object->oob_table = fscache_osm_init_oob;
 303         object->flags = 1 << FSCACHE_OBJECT_IS_LIVE;
 304         spin_lock_init(&object->lock);
 305         INIT_LIST_HEAD(&object->cache_link);
 306         INIT_HLIST_NODE(&object->cookie_link);
 307         INIT_WORK(&object->work, fscache_object_work_func);
 308         INIT_LIST_HEAD(&object->dependents);
 309         INIT_LIST_HEAD(&object->dep_link);
 310         INIT_LIST_HEAD(&object->pending_ops);
 311         object->n_children = 0;
 312         object->n_ops = object->n_in_progress = object->n_exclusive = 0;
 313         object->events = 0;
 314         object->store_limit = 0;
 315         object->store_limit_l = 0;
 316         object->cache = cache;
 317         object->cookie = cookie;
 318         object->parent = NULL;
 319
 320         object->oob_event_mask = 0;
 321         for (t = object->oob_table; t->events; t++)
 322                 object->oob_event_mask |= t->events;
 323         object->event_mask = object->oob_event_mask;
 324         for (t = object->state->transitions; t->events; t++)
 325                 object->event_mask |= t->events;
 326 }
 327 EXPORT_SYMBOL(fscache_object_init);
 328
 329 /*
 330  * Abort object initialisation before we start it.
 331  */
 332 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
 333                                                                 int event)
 334 {
 335         struct fscache_cookie *cookie;
 336
 337         _enter("{OBJ%x},%d", object->debug_id, event);
 338
 339         object->oob_event_mask = 0;
 340         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 341
 342         fscache_dequeue_object(object);
 343
 344         spin_lock(&object->lock);
 345         cookie = object->cookie;
 346         clear_bit_unlock(FSCACHE_COOKIE_CREATING, &cookie->flags);
 347         spin_unlock(&object->lock);
 348
 349         wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 350
 351         return transit_to(KILL_OBJECT);
 352 }
 353
 354 /*
 355  * initialise an object
 356  * - check the specified object's parent to see if we can make use of it
 357  *   immediately to do a creation
 358  * - we may need to start the process of creating a parent and we need to wait
 359  *   for the parent's lookup and creation to complete if it's not there yet
 360  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 361  *   leaf-most cookies of the object and all its children
 362  */
 363 static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
 364                                                              int event)
 365 {
 366         struct fscache_object *parent;
 367         bool success;
 368
 369         _enter("{OBJ%x},%d", object->debug_id, event);
 370
 371         ASSERT(list_empty(&object->dep_link));
 372
 373         parent = object->parent;
 374         if (!parent) {
 375                 _leave(" [no parent]");
 376                 return transit_to(DETACH_FROM_COOKIE);
 377         }
 378
 379         _debug("parent %s", parent->state->name);
 380
 381         if (fscache_object_is_dying(parent)) {
 382                 _leave(" [bad parent]");
 383                 return transit_to(DETACH_FROM_COOKIE);
 384         }
 385
 386         if (fscache_object_is_available(parent)) {
 387                 _leave(" [ready]");
 388                 return transit_to(PARENT_READY);
 389         }
 390
 391         _debug("wait");
 392
 393         spin_lock(&parent->lock);
 394         fscache_stat(&fscache_n_cop_grab_object);
 395         success = false;
 396         if (fscache_object_is_live(parent) &&
 397             object->cache->ops->grab_object(object)) {
 398                 list_add(&object->dep_link, &parent->dependents);
 399                 success = true;
 400         }
 401         fscache_stat_d(&fscache_n_cop_grab_object);
 402         spin_unlock(&parent->lock);
 403         if (!success) {
 404                 _leave(" [grab failed]");
 405                 return transit_to(DETACH_FROM_COOKIE);
 406         }
 407
 408         /* fscache_acquire_non_index_cookie() uses this
 409          * to wake the chain up */
 410         fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
 411         _leave(" [wait]");
 412         return transit_to(WAIT_FOR_PARENT);
 413 }
 414
 415 /*
 416  * Once the parent object is ready, we should kick off our lookup op.
 417  */
 418 static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
 419                                                         int event)
 420 {
 421         struct fscache_object *parent = object->parent;
 422
 423         _enter("{OBJ%x},%d", object->debug_id, event);
 424
 425         ASSERT(parent != NULL);
 426
 427         spin_lock(&parent->lock);
 428         parent->n_ops++;
 429         parent->n_obj_ops++;
 430         object->lookup_jif = jiffies;
 431         spin_unlock(&parent->lock);
 432
 433         _leave("");
 434         return transit_to(LOOK_UP_OBJECT);
 435 }
 436
 437 /*
 438  * look an object up in the cache from which it was allocated
 439  * - we hold an "access lock" on the parent object, so the parent object cannot
 440  *   be withdrawn by either party till we've finished
 441  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 442  *   leaf-most cookies of the object and all its children
 443  */
 444 static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
 445                                                           int event)
 446 {
 447         struct fscache_cookie *cookie = object->cookie;
 448         struct fscache_object *parent = object->parent;
 449         int ret;
 450
 451         _enter("{OBJ%x},%d", object->debug_id, event);
 452
 453         object->oob_table = fscache_osm_lookup_oob;
 454
 455         ASSERT(parent != NULL);
 456         ASSERTCMP(parent->n_ops, >, 0);
 457         ASSERTCMP(parent->n_obj_ops, >, 0);
 458
 459         /* make sure the parent is still available */
 460         ASSERT(fscache_object_is_available(parent));
 461
 462         if (fscache_object_is_dying(parent) ||
 463             test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 464                 _leave(" [unavailable]");
 465                 return transit_to(LOOKUP_FAILURE);
 466         }
 467
 468         _debug("LOOKUP \"%s/%s\" in \"%s\"",
 469                parent->cookie->def->name, cookie->def->name,
 470                object->cache->tag->name);
 471
 472         fscache_stat(&fscache_n_object_lookups);
 473         fscache_stat(&fscache_n_cop_lookup_object);
 474         ret = object->cache->ops->lookup_object(object);
 475         fscache_stat_d(&fscache_n_cop_lookup_object);
 476
 477         if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
 478                 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 479
 480         if (ret == -ETIMEDOUT) {
 481                 /* probably stuck behind another object, so move this one to
 482                  * the back of the queue */
 483                 fscache_stat(&fscache_n_object_lookups_timed_out);
 484                 _leave(" [timeout]");
 485                 return NO_TRANSIT;
 486         }
 487
 488         if (ret < 0) {
 489                 _leave(" [error]");
 490                 return transit_to(LOOKUP_FAILURE);
 491         }
 492
 493         _leave(" [ok]");
 494         return transit_to(OBJECT_AVAILABLE);
 495 }
 496
 497 /**
 498  * fscache_object_lookup_negative - Note negative cookie lookup
 499  * @object: Object pointing to cookie to mark
 500  *
 501  * Note negative lookup, permitting those waiting to read data from an already
 502  * existing backing object to continue as there's no data for them to read.
 503  */
 504 void fscache_object_lookup_negative(struct fscache_object *object)
 505 {
 506         struct fscache_cookie *cookie = object->cookie;
 507
 508         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 509
 510         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 511                 fscache_stat(&fscache_n_object_lookups_negative);
 512
 513                 /* Allow write requests to begin stacking up and read requests to begin
 514                  * returning ENODATA.
 515                  */
 516                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 517
 518                 _debug("wake up lookup %p", &cookie->flags);
 519                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 520                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 521         }
 522         _leave("");
 523 }
 524 EXPORT_SYMBOL(fscache_object_lookup_negative);
 525
 526 /**
 527  * fscache_obtained_object - Note successful object lookup or creation
 528  * @object: Object pointing to cookie to mark
 529  *
 530  * Note successful lookup and/or creation, permitting those waiting to write
 531  * data to a backing object to continue.
 532  *
 533  * Note that after calling this, an object's cookie may be relinquished by the
 534  * netfs, and so must be accessed with object lock held.
 535  */
 536 void fscache_obtained_object(struct fscache_object *object)
 537 {
 538         struct fscache_cookie *cookie = object->cookie;
 539
 540         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 541
 542         /* if we were still looking up, then we must have a positive lookup
 543          * result, in which case there may be data available */
 544         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 545                 fscache_stat(&fscache_n_object_lookups_positive);
 546
 547                 /* We do (presumably) have data */
 548                 clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 549
 550                 /* Allow write requests to begin stacking up and read requests
 551                  * to begin shovelling data.
 552                  */
 553                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 554                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 555         } else {
 556                 fscache_stat(&fscache_n_object_created);
 557         }
 558
 559         set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
 560
 561         /* Permit __fscache_relinquish_cookie() to proceed */
 562         clear_bit_unlock(FSCACHE_COOKIE_CREATING, &cookie->flags);
 563         wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 564
 565         _leave("");
 566 }
 567 EXPORT_SYMBOL(fscache_obtained_object);
 568
 569 /*
 570  * handle an object that has just become available
 571  */
 572 static const struct fscache_state *fscache_object_available(struct fscache_object *object,
 573                                                             int event)
 574 {
 575         struct fscache_cookie *cookie = object->cookie;
 576
 577         _enter("{OBJ%x},%d", object->debug_id, event);
 578
 579         object->oob_table = fscache_osm_run_oob;
 580
 581         spin_lock(&object->lock);
 582
 583         ASSERTIF(cookie, !test_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags));
 584
 585         fscache_done_parent_op(object);
 586         if (object->n_in_progress == 0) {
 587                 if (object->n_ops > 0) {
 588                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 589                         fscache_start_operations(object);
 590                 } else {
 591                         ASSERT(list_empty(&object->pending_ops));
 592                 }
 593         }
 594         spin_unlock(&object->lock);
 595
 596         fscache_stat(&fscache_n_cop_lookup_complete);
 597         object->cache->ops->lookup_complete(object);
 598         fscache_stat_d(&fscache_n_cop_lookup_complete);
 599
 600         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 601         fscache_stat(&fscache_n_object_avail);
 602
 603         _leave("");
 604         return transit_to(JUMPSTART_DEPS);
 605 }
 606
 607 /*
 608  * Wake up this object's dependent objects now that we've become available.
 609  */
 610 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
 611                                                                 int event)
 612 {
 613         _enter("{OBJ%x},%d", object->debug_id, event);
 614
 615         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
 616                 return NO_TRANSIT; /* Not finished; requeue */
 617         return transit_to(WAIT_FOR_CMD);
 618 }
 619
 620 /*
 621  * Handle lookup or creation failute.
 622  */
 623 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
 624                                                           int event)
 625 {
 626         struct fscache_cookie *cookie;
 627         bool wake_looking_up = false;
 628
 629         _enter("{OBJ%x},%d", object->debug_id, event);
 630
 631         object->oob_event_mask = 0;
 632
 633         fscache_stat(&fscache_n_cop_lookup_complete);
 634         object->cache->ops->lookup_complete(object);
 635         fscache_stat_d(&fscache_n_cop_lookup_complete);
 636
 637         spin_lock(&object->lock);
 638         cookie = object->cookie;
 639         set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 640         if (cookie) {
 641                 if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
 642                         wake_looking_up = true;
 643                 clear_bit_unlock(FSCACHE_COOKIE_CREATING, &cookie->flags);
 644         }
 645         spin_unlock(&object->lock);
 646
 647         if (wake_looking_up)
 648                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 649         wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 650
 651         fscache_done_parent_op(object);
 652         return transit_to(KILL_OBJECT);
 653 }
 654
 655 /*
 656  * Wait for completion of all active operations on this object and the death of
 657  * all child objects of this object.
 658  */
 659 static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
 660                                                        int event)
 661 {
 662         _enter("{OBJ%x,%d,%d},%d",
 663                object->debug_id, object->n_ops, object->n_children, event);
 664
 665         object->oob_event_mask = 0;
 666
 667         spin_lock(&object->lock);
 668         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 669         spin_unlock(&object->lock);
 670
 671         if (list_empty(&object->dependents) &&
 672             object->n_ops == 0 &&
 673             object->n_children == 0)
 674                 return object->cookie ?
 675                         transit_to(DETACH_FROM_COOKIE) : transit_to(DROP_OBJECT);
 676
 677         spin_lock(&object->lock);
 678         fscache_start_operations(object);
 679         spin_unlock(&object->lock);
 680
 681         if (!list_empty(&object->dependents))
 682                 return transit_to(KILL_DEPENDENTS);
 683
 684         return transit_to(WAIT_FOR_CLEARANCE);
 685 }
 686
 687 /*
 688  * Kill dependent objects.
 689  */
 690 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
 691                                                            int event)
 692 {
 693         _enter("{OBJ%x},%d", object->debug_id, event);
 694
 695         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
 696                 return NO_TRANSIT; /* Not finished */
 697         return transit_to(WAIT_FOR_CLEARANCE);
 698 }
 699
 700 /*
 701  * withdraw an object from active service
 702  */
 703 static const struct fscache_state *fscache_detach_from_cookie(struct fscache_object *object,
 704                                                               int event)
 705 {
 706         struct fscache_cookie *cookie;
 707         bool detached = false, awaken = false;
 708
 709         _enter("{OBJ%x},%d", object->debug_id, event);
 710
 711         spin_lock(&object->lock);
 712         cookie = object->cookie;
 713         if (cookie) {
 714                 /* need to get the cookie lock before the object lock, starting
 715                  * from the object pointer */
 716                 atomic_inc(&cookie->usage);
 717                 spin_unlock(&object->lock);
 718
 719                 spin_lock(&cookie->lock);
 720                 spin_lock(&object->lock);
 721
 722                 if (object->cookie == cookie) {
 723                         hlist_del_init(&object->cookie_link);
 724                         object->cookie = NULL;
 725                         if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING,
 726                                                &cookie->flags))
 727                                 awaken = true;
 728                         detached = true;
 729                 }
 730                 spin_unlock(&cookie->lock);
 731                 fscache_cookie_put(cookie);
 732                 if (detached)
 733                         fscache_cookie_put(cookie);
 734         }
 735
 736         spin_unlock(&object->lock);
 737
 738         if (awaken)
 739                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 740
 741         fscache_stat(&fscache_n_object_dead);
 742         _leave("");
 743         return transit_to(DROP_OBJECT);
 744 }
 745
 746 /*
 747  * Drop an object's attachments
 748  */
 749 static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
 750                                                        int event)
 751 {
 752         struct fscache_object *parent = object->parent;
 753         struct fscache_cache *cache = object->cache;
 754
 755         _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
 756
 757         ASSERTCMP(object->cookie, ==, NULL);
 758         ASSERT(hlist_unhashed(&object->cookie_link));
 759
 760         /* Prevent a race with our last child, which has to signal EV_CLEARED
 761          * before dropping our spinlock.
 762          */
 763         spin_lock(&object->lock);
 764         spin_unlock(&object->lock);
 765
 766         /* Discard from the cache's collection of objects */
 767         spin_lock(&cache->object_list_lock);
 768         list_del_init(&object->cache_link);
 769         spin_unlock(&cache->object_list_lock);
 770
 771         fscache_stat(&fscache_n_cop_drop_object);
 772         cache->ops->drop_object(object);
 773         fscache_stat_d(&fscache_n_cop_drop_object);
 774
 775         /* The parent object wants to know when all it dependents have gone */
 776         if (parent) {
 777                 _debug("release parent OBJ%x {%d}",
 778                        parent->debug_id, parent->n_children);
 779
 780                 spin_lock(&parent->lock);
 781                 parent->n_children--;
 782                 if (parent->n_children == 0)
 783                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 784                 spin_unlock(&parent->lock);
 785                 object->parent = NULL;
 786         }
 787
 788         /* this just shifts the object release to the work processor */
 789         fscache_put_object(object);
 790         fscache_stat(&fscache_n_object_dead);
 791
 792         _leave("");
 793         return transit_to(OBJECT_DEAD);
 794 }
 795
 796 /*
 797  * get a ref on an object
 798  */
 799 static int fscache_get_object(struct fscache_object *object)
 800 {
 801         int ret;
 802
 803         fscache_stat(&fscache_n_cop_grab_object);
 804         ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 805         fscache_stat_d(&fscache_n_cop_grab_object);
 806         return ret;
 807 }
 808
 809 /*
 810  * Discard a ref on an object
 811  */
 812 static void fscache_put_object(struct fscache_object *object)
 813 {
 814         fscache_stat(&fscache_n_cop_put_object);
 815         object->cache->ops->put_object(object);
 816         fscache_stat_d(&fscache_n_cop_put_object);
 817 }
 818
 819 /*
 820  * enqueue an object for metadata-type processing
 821  */
 822 void fscache_enqueue_object(struct fscache_object *object)
 823 {
 824         _enter("{OBJ%x}", object->debug_id);
 825
 826         if (fscache_get_object(object) >= 0) {
 827                 wait_queue_head_t *cong_wq =
 828                         &get_cpu_var(fscache_object_cong_wait);
 829
 830                 if (queue_work(fscache_object_wq, &object->work)) {
 831                         if (fscache_object_congested())
 832                                 wake_up(cong_wq);
 833                 } else
 834                         fscache_put_object(object);
 835
 836                 put_cpu_var(fscache_object_cong_wait);
 837         }
 838 }
 839
 840 /**
 841  * fscache_object_sleep_till_congested - Sleep until object wq is congested
 842  * @timeoutp: Scheduler sleep timeout
 843  *
 844  * Allow an object handler to sleep until the object workqueue is congested.
 845  *
 846  * The caller must set up a wake up event before calling this and must have set
 847  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 848  * condition before calling this function as no test is made here.
 849  *
 850  * %true is returned if the object wq is congested, %false otherwise.
 851  */
 852 bool fscache_object_sleep_till_congested(signed long *timeoutp)
 853 {
 854         wait_queue_head_t *cong_wq = &__get_cpu_var(fscache_object_cong_wait);
 855         DEFINE_WAIT(wait);
 856
 857         if (fscache_object_congested())
 858                 return true;
 859
 860         add_wait_queue_exclusive(cong_wq, &wait);
 861         if (!fscache_object_congested())
 862                 *timeoutp = schedule_timeout(*timeoutp);
 863         finish_wait(cong_wq, &wait);
 864
 865         return fscache_object_congested();
 866 }
 867 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 868
 869 /*
 870  * Enqueue the dependents of an object for metadata-type processing.
 871  *
 872  * If we don't manage to finish the list before the scheduler wants to run
 873  * again then return false immediately.  We return true if the list was
 874  * cleared.
 875  */
 876 static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
 877 {
 878         struct fscache_object *dep;
 879         bool ret = true;
 880
 881         _enter("{OBJ%x}", object->debug_id);
 882
 883         if (list_empty(&object->dependents))
 884                 return true;
 885
 886         spin_lock(&object->lock);
 887
 888         while (!list_empty(&object->dependents)) {
 889                 dep = list_entry(object->dependents.next,
 890                                  struct fscache_object, dep_link);
 891                 list_del_init(&dep->dep_link);
 892
 893                 fscache_raise_event(dep, event);
 894                 fscache_put_object(dep);
 895
 896                 if (!list_empty(&object->dependents) && need_resched()) {
 897                         ret = false;
 898                         break;
 899                 }
 900         }
 901
 902         spin_unlock(&object->lock);
 903         return ret;
 904 }
 905
 906 /*
 907  * remove an object from whatever queue it's waiting on
 908  */
 909 static void fscache_dequeue_object(struct fscache_object *object)
 910 {
 911         _enter("{OBJ%x}", object->debug_id);
 912
 913         if (!list_empty(&object->dep_link)) {
 914                 spin_lock(&object->parent->lock);
 915                 list_del_init(&object->dep_link);
 916                 spin_unlock(&object->parent->lock);
 917         }
 918
 919         _leave("");
 920 }
 921
 922 /**
 923  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 924  * @object: The object to ask about
 925  * @data: The auxiliary data for the object
 926  * @datalen: The size of the auxiliary data
 927  *
 928  * This function consults the netfs about the coherency state of an object
 929  */
 930 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 931                                         const void *data, uint16_t datalen)
 932 {
 933         enum fscache_checkaux result;
 934
 935         if (!object->cookie->def->check_aux) {
 936                 fscache_stat(&fscache_n_checkaux_none);
 937                 return FSCACHE_CHECKAUX_OKAY;
 938         }
 939
 940         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 941                                                 data, datalen);
 942         switch (result) {
 943                 /* entry okay as is */
 944         case FSCACHE_CHECKAUX_OKAY:
 945                 fscache_stat(&fscache_n_checkaux_okay);
 946                 break;
 947
 948                 /* entry requires update */
 949         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 950                 fscache_stat(&fscache_n_checkaux_update);
 951                 break;
 952
 953                 /* entry requires deletion */
 954         case FSCACHE_CHECKAUX_OBSOLETE:
 955                 fscache_stat(&fscache_n_checkaux_obsolete);
 956                 break;
 957
 958         default:
 959                 BUG();
 960         }
 961
 962         return result;
 963 }
 964 EXPORT_SYMBOL(fscache_check_aux);
 965
 966 /*
 967  * Asynchronously invalidate an object.
 968  */
 969 static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
 970                                                               int event)
 971 {
 972         struct fscache_operation *op;
 973         struct fscache_cookie *cookie = object->cookie;
 974
 975         _enter("{OBJ%x},%d", object->debug_id, event);
 976
 977
 978         /* Reject any new read/write ops and abort any that are pending. */
 979         fscache_invalidate_writes(cookie);
 980         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 981         fscache_cancel_all_ops(object);
 982
 983         /* Now we have to wait for in-progress reads and writes */
 984         op = kzalloc(sizeof(*op), GFP_KERNEL);
 985         if (!op) {
 986                 clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 987                 _leave(" [ENOMEM]");
 988                 return transit_to(KILL_OBJECT);
 989         }
 990
 991         fscache_operation_init(op, object->cache->ops->invalidate_object, NULL);
 992         op->flags = FSCACHE_OP_ASYNC | (1 << FSCACHE_OP_EXCLUSIVE);
 993
 994         spin_lock(&cookie->lock);
 995         if (fscache_submit_exclusive_op(object, op) < 0)
 996                 goto submit_op_failed;
 997         spin_unlock(&cookie->lock);
 998         fscache_put_operation(op);
 999
1000         /* Once we've completed the invalidation, we know there will be no data
1001          * stored in the cache and thus we can reinstate the data-check-skip
1002          * optimisation.
1003          */
1004         set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
1005
1006         /* We can allow read and write requests to come in once again.  They'll
1007          * queue up behind our exclusive invalidation operation.
1008          */
1009         if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
1010                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
1011         _leave(" [ok]");
1012         return transit_to(UPDATE_OBJECT);
1013
1014 submit_op_failed:
1015         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
1016         spin_unlock(&cookie->lock);
1017         kfree(op);
1018         _leave(" [EIO]");
1019         return transit_to(KILL_OBJECT);
1020 }
1021
1022 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
1023                                                              int event)
1024 {
1025         const struct fscache_state *s;
1026
1027         fscache_stat(&fscache_n_invalidates_run);
1028         fscache_stat(&fscache_n_cop_invalidate_object);
1029         s = _fscache_invalidate_object(object, event);
1030         fscache_stat_d(&fscache_n_cop_invalidate_object);
1031         return s;
1032 }
1033
1034 /*
1035  * Asynchronously update an object.
1036  */
1037 static const struct fscache_state *fscache_update_object(struct fscache_object *object,
1038                                                          int event)
1039 {
1040         _enter("{OBJ%x},%d", object->debug_id, event);
1041
1042         fscache_stat(&fscache_n_updates_run);
1043         fscache_stat(&fscache_n_cop_update_object);
1044         object->cache->ops->update_object(object);
1045         fscache_stat_d(&fscache_n_cop_update_object);
1046
1047         _leave("");
1048         return transit_to(WAIT_FOR_CMD);
1049 }