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