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 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 318         RB_CLEAR_NODE(&object->objlist_link);
 319 #endif
 320
 321         object->oob_event_mask = 0;
 322         for (t = object->oob_table; t->events; t++)
 323                 object->oob_event_mask |= t->events;
 324         object->event_mask = object->oob_event_mask;
 325         for (t = object->state->transitions; t->events; t++)
 326                 object->event_mask |= t->events;
 327 }
 328 EXPORT_SYMBOL(fscache_object_init);
 329
 330 /*
 331  * Abort object initialisation before we start it.
 332  */
 333 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
 334                                                                 int event)
 335 {
 336         _enter("{OBJ%x},%d", object->debug_id, event);
 337
 338         object->oob_event_mask = 0;
 339         fscache_dequeue_object(object);
 340         return transit_to(KILL_OBJECT);
 341 }
 342
 343 /*
 344  * initialise an object
 345  * - check the specified object's parent to see if we can make use of it
 346  *   immediately to do a creation
 347  * - we may need to start the process of creating a parent and we need to wait
 348  *   for the parent's lookup and creation to complete if it's not there yet
 349  */
 350 static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
 351                                                              int event)
 352 {
 353         struct fscache_object *parent;
 354         bool success;
 355
 356         _enter("{OBJ%x},%d", object->debug_id, event);
 357
 358         ASSERT(list_empty(&object->dep_link));
 359
 360         parent = object->parent;
 361         if (!parent) {
 362                 _leave(" [no parent]");
 363                 return transit_to(DROP_OBJECT);
 364         }
 365
 366         _debug("parent: %s of:%lx", parent->state->name, parent->flags);
 367
 368         if (fscache_object_is_dying(parent)) {
 369                 _leave(" [bad parent]");
 370                 return transit_to(DROP_OBJECT);
 371         }
 372
 373         if (fscache_object_is_available(parent)) {
 374                 _leave(" [ready]");
 375                 return transit_to(PARENT_READY);
 376         }
 377
 378         _debug("wait");
 379
 380         spin_lock(&parent->lock);
 381         fscache_stat(&fscache_n_cop_grab_object);
 382         success = false;
 383         if (fscache_object_is_live(parent) &&
 384             object->cache->ops->grab_object(object)) {
 385                 list_add(&object->dep_link, &parent->dependents);
 386                 success = true;
 387         }
 388         fscache_stat_d(&fscache_n_cop_grab_object);
 389         spin_unlock(&parent->lock);
 390         if (!success) {
 391                 _leave(" [grab failed]");
 392                 return transit_to(DROP_OBJECT);
 393         }
 394
 395         /* fscache_acquire_non_index_cookie() uses this
 396          * to wake the chain up */
 397         fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
 398         _leave(" [wait]");
 399         return transit_to(WAIT_FOR_PARENT);
 400 }
 401
 402 /*
 403  * Once the parent object is ready, we should kick off our lookup op.
 404  */
 405 static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
 406                                                         int event)
 407 {
 408         struct fscache_object *parent = object->parent;
 409
 410         _enter("{OBJ%x},%d", object->debug_id, event);
 411
 412         ASSERT(parent != NULL);
 413
 414         spin_lock(&parent->lock);
 415         parent->n_ops++;
 416         parent->n_obj_ops++;
 417         object->lookup_jif = jiffies;
 418         spin_unlock(&parent->lock);
 419
 420         _leave("");
 421         return transit_to(LOOK_UP_OBJECT);
 422 }
 423
 424 /*
 425  * look an object up in the cache from which it was allocated
 426  * - we hold an "access lock" on the parent object, so the parent object cannot
 427  *   be withdrawn by either party till we've finished
 428  */
 429 static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
 430                                                           int event)
 431 {
 432         struct fscache_cookie *cookie = object->cookie;
 433         struct fscache_object *parent = object->parent;
 434         int ret;
 435
 436         _enter("{OBJ%x},%d", object->debug_id, event);
 437
 438         object->oob_table = fscache_osm_lookup_oob;
 439
 440         ASSERT(parent != NULL);
 441         ASSERTCMP(parent->n_ops, >, 0);
 442         ASSERTCMP(parent->n_obj_ops, >, 0);
 443
 444         /* make sure the parent is still available */
 445         ASSERT(fscache_object_is_available(parent));
 446
 447         if (fscache_object_is_dying(parent) ||
 448             test_bit(FSCACHE_IOERROR, &object->cache->flags) ||
 449             !fscache_use_cookie(object)) {
 450                 _leave(" [unavailable]");
 451                 return transit_to(LOOKUP_FAILURE);
 452         }
 453
 454         _debug("LOOKUP \"%s\" in \"%s\"",
 455                cookie->def->name, object->cache->tag->name);
 456
 457         fscache_stat(&fscache_n_object_lookups);
 458         fscache_stat(&fscache_n_cop_lookup_object);
 459         ret = object->cache->ops->lookup_object(object);
 460         fscache_stat_d(&fscache_n_cop_lookup_object);
 461
 462         fscache_unuse_cookie(object);
 463
 464         if (ret == -ETIMEDOUT) {
 465                 /* probably stuck behind another object, so move this one to
 466                  * the back of the queue */
 467                 fscache_stat(&fscache_n_object_lookups_timed_out);
 468                 _leave(" [timeout]");
 469                 return NO_TRANSIT;
 470         }
 471
 472         if (ret < 0) {
 473                 _leave(" [error]");
 474                 return transit_to(LOOKUP_FAILURE);
 475         }
 476
 477         _leave(" [ok]");
 478         return transit_to(OBJECT_AVAILABLE);
 479 }
 480
 481 /**
 482  * fscache_object_lookup_negative - Note negative cookie lookup
 483  * @object: Object pointing to cookie to mark
 484  *
 485  * Note negative lookup, permitting those waiting to read data from an already
 486  * existing backing object to continue as there's no data for them to read.
 487  */
 488 void fscache_object_lookup_negative(struct fscache_object *object)
 489 {
 490         struct fscache_cookie *cookie = object->cookie;
 491
 492         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 493
 494         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 495                 fscache_stat(&fscache_n_object_lookups_negative);
 496
 497                 /* Allow write requests to begin stacking up and read requests to begin
 498                  * returning ENODATA.
 499                  */
 500                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 501                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 502
 503                 _debug("wake up lookup %p", &cookie->flags);
 504                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 505                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 506         }
 507         _leave("");
 508 }
 509 EXPORT_SYMBOL(fscache_object_lookup_negative);
 510
 511 /**
 512  * fscache_obtained_object - Note successful object lookup or creation
 513  * @object: Object pointing to cookie to mark
 514  *
 515  * Note successful lookup and/or creation, permitting those waiting to write
 516  * data to a backing object to continue.
 517  *
 518  * Note that after calling this, an object's cookie may be relinquished by the
 519  * netfs, and so must be accessed with object lock held.
 520  */
 521 void fscache_obtained_object(struct fscache_object *object)
 522 {
 523         struct fscache_cookie *cookie = object->cookie;
 524
 525         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 526
 527         /* if we were still looking up, then we must have a positive lookup
 528          * result, in which case there may be data available */
 529         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 530                 fscache_stat(&fscache_n_object_lookups_positive);
 531
 532                 /* We do (presumably) have data */
 533                 clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 534                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 535
 536                 /* Allow write requests to begin stacking up and read requests
 537                  * to begin shovelling data.
 538                  */
 539                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 540                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 541         } else {
 542                 fscache_stat(&fscache_n_object_created);
 543         }
 544
 545         set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
 546         _leave("");
 547 }
 548 EXPORT_SYMBOL(fscache_obtained_object);
 549
 550 /*
 551  * handle an object that has just become available
 552  */
 553 static const struct fscache_state *fscache_object_available(struct fscache_object *object,
 554                                                             int event)
 555 {
 556         _enter("{OBJ%x},%d", object->debug_id, event);
 557
 558         object->oob_table = fscache_osm_run_oob;
 559
 560         spin_lock(&object->lock);
 561
 562         fscache_done_parent_op(object);
 563         if (object->n_in_progress == 0) {
 564                 if (object->n_ops > 0) {
 565                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 566                         fscache_start_operations(object);
 567                 } else {
 568                         ASSERT(list_empty(&object->pending_ops));
 569                 }
 570         }
 571         spin_unlock(&object->lock);
 572
 573         fscache_stat(&fscache_n_cop_lookup_complete);
 574         object->cache->ops->lookup_complete(object);
 575         fscache_stat_d(&fscache_n_cop_lookup_complete);
 576
 577         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 578         fscache_stat(&fscache_n_object_avail);
 579
 580         _leave("");
 581         return transit_to(JUMPSTART_DEPS);
 582 }
 583
 584 /*
 585  * Wake up this object's dependent objects now that we've become available.
 586  */
 587 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
 588                                                                 int event)
 589 {
 590         _enter("{OBJ%x},%d", object->debug_id, event);
 591
 592         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
 593                 return NO_TRANSIT; /* Not finished; requeue */
 594         return transit_to(WAIT_FOR_CMD);
 595 }
 596
 597 /*
 598  * Handle lookup or creation failute.
 599  */
 600 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
 601                                                           int event)
 602 {
 603         struct fscache_cookie *cookie;
 604
 605         _enter("{OBJ%x},%d", object->debug_id, event);
 606
 607         object->oob_event_mask = 0;
 608
 609         fscache_stat(&fscache_n_cop_lookup_complete);
 610         object->cache->ops->lookup_complete(object);
 611         fscache_stat_d(&fscache_n_cop_lookup_complete);
 612
 613         cookie = object->cookie;
 614         set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 615         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
 616                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 617
 618         fscache_done_parent_op(object);
 619         return transit_to(KILL_OBJECT);
 620 }
 621
 622 /*
 623  * Wait for completion of all active operations on this object and the death of
 624  * all child objects of this object.
 625  */
 626 static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
 627                                                        int event)
 628 {
 629         _enter("{OBJ%x,%d,%d},%d",
 630                object->debug_id, object->n_ops, object->n_children, event);
 631
 632         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 633         object->oob_event_mask = 0;
 634
 635         if (list_empty(&object->dependents) &&
 636             object->n_ops == 0 &&
 637             object->n_children == 0)
 638                 return transit_to(DROP_OBJECT);
 639
 640         if (object->n_in_progress == 0) {
 641                 spin_lock(&object->lock);
 642                 if (object->n_ops > 0 && object->n_in_progress == 0)
 643                         fscache_start_operations(object);
 644                 spin_unlock(&object->lock);
 645         }
 646
 647         if (!list_empty(&object->dependents))
 648                 return transit_to(KILL_DEPENDENTS);
 649
 650         return transit_to(WAIT_FOR_CLEARANCE);
 651 }
 652
 653 /*
 654  * Kill dependent objects.
 655  */
 656 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
 657                                                            int event)
 658 {
 659         _enter("{OBJ%x},%d", object->debug_id, event);
 660
 661         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
 662                 return NO_TRANSIT; /* Not finished */
 663         return transit_to(WAIT_FOR_CLEARANCE);
 664 }
 665
 666 /*
 667  * Drop an object's attachments
 668  */
 669 static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
 670                                                        int event)
 671 {
 672         struct fscache_object *parent = object->parent;
 673         struct fscache_cookie *cookie = object->cookie;
 674         struct fscache_cache *cache = object->cache;
 675         bool awaken = false;
 676
 677         _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
 678
 679         ASSERT(cookie != NULL);
 680         ASSERT(!hlist_unhashed(&object->cookie_link));
 681
 682         /* Make sure the cookie no longer points here and that the netfs isn't
 683          * waiting for us.
 684          */
 685         spin_lock(&cookie->lock);
 686         hlist_del_init(&object->cookie_link);
 687         if (hlist_empty(&cookie->backing_objects) &&
 688             test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 689                 awaken = true;
 690         spin_unlock(&cookie->lock);
 691
 692         if (awaken)
 693                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 694
 695         /* Prevent a race with our last child, which has to signal EV_CLEARED
 696          * before dropping our spinlock.
 697          */
 698         spin_lock(&object->lock);
 699         spin_unlock(&object->lock);
 700
 701         /* Discard from the cache's collection of objects */
 702         spin_lock(&cache->object_list_lock);
 703         list_del_init(&object->cache_link);
 704         spin_unlock(&cache->object_list_lock);
 705
 706         fscache_stat(&fscache_n_cop_drop_object);
 707         cache->ops->drop_object(object);
 708         fscache_stat_d(&fscache_n_cop_drop_object);
 709
 710         /* The parent object wants to know when all it dependents have gone */
 711         if (parent) {
 712                 _debug("release parent OBJ%x {%d}",
 713                        parent->debug_id, parent->n_children);
 714
 715                 spin_lock(&parent->lock);
 716                 parent->n_children--;
 717                 if (parent->n_children == 0)
 718                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 719                 spin_unlock(&parent->lock);
 720                 object->parent = NULL;
 721         }
 722
 723         /* this just shifts the object release to the work processor */
 724         fscache_put_object(object);
 725         fscache_stat(&fscache_n_object_dead);
 726
 727         _leave("");
 728         return transit_to(OBJECT_DEAD);
 729 }
 730
 731 /*
 732  * get a ref on an object
 733  */
 734 static int fscache_get_object(struct fscache_object *object)
 735 {
 736         int ret;
 737
 738         fscache_stat(&fscache_n_cop_grab_object);
 739         ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 740         fscache_stat_d(&fscache_n_cop_grab_object);
 741         return ret;
 742 }
 743
 744 /*
 745  * Discard a ref on an object
 746  */
 747 static void fscache_put_object(struct fscache_object *object)
 748 {
 749         fscache_stat(&fscache_n_cop_put_object);
 750         object->cache->ops->put_object(object);
 751         fscache_stat_d(&fscache_n_cop_put_object);
 752 }
 753
 754 /**
 755  * fscache_object_destroy - Note that a cache object is about to be destroyed
 756  * @object: The object to be destroyed
 757  *
 758  * Note the imminent destruction and deallocation of a cache object record.
 759  */
 760 void fscache_object_destroy(struct fscache_object *object)
 761 {
 762         fscache_objlist_remove(object);
 763
 764         /* We can get rid of the cookie now */
 765         fscache_cookie_put(object->cookie);
 766         object->cookie = NULL;
 767 }
 768 EXPORT_SYMBOL(fscache_object_destroy);
 769
 770 /*
 771  * enqueue an object for metadata-type processing
 772  */
 773 void fscache_enqueue_object(struct fscache_object *object)
 774 {
 775         _enter("{OBJ%x}", object->debug_id);
 776
 777         if (fscache_get_object(object) >= 0) {
 778                 wait_queue_head_t *cong_wq =
 779                         &get_cpu_var(fscache_object_cong_wait);
 780
 781                 if (queue_work(fscache_object_wq, &object->work)) {
 782                         if (fscache_object_congested())
 783                                 wake_up(cong_wq);
 784                 } else
 785                         fscache_put_object(object);
 786
 787                 put_cpu_var(fscache_object_cong_wait);
 788         }
 789 }
 790
 791 /**
 792  * fscache_object_sleep_till_congested - Sleep until object wq is congested
 793  * @timeoutp: Scheduler sleep timeout
 794  *
 795  * Allow an object handler to sleep until the object workqueue is congested.
 796  *
 797  * The caller must set up a wake up event before calling this and must have set
 798  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 799  * condition before calling this function as no test is made here.
 800  *
 801  * %true is returned if the object wq is congested, %false otherwise.
 802  */
 803 bool fscache_object_sleep_till_congested(signed long *timeoutp)
 804 {
 805         wait_queue_head_t *cong_wq = this_cpu_ptr(&fscache_object_cong_wait);
 806         DEFINE_WAIT(wait);
 807
 808         if (fscache_object_congested())
 809                 return true;
 810
 811         add_wait_queue_exclusive(cong_wq, &wait);
 812         if (!fscache_object_congested())
 813                 *timeoutp = schedule_timeout(*timeoutp);
 814         finish_wait(cong_wq, &wait);
 815
 816         return fscache_object_congested();
 817 }
 818 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 819
 820 /*
 821  * Enqueue the dependents of an object for metadata-type processing.
 822  *
 823  * If we don't manage to finish the list before the scheduler wants to run
 824  * again then return false immediately.  We return true if the list was
 825  * cleared.
 826  */
 827 static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
 828 {
 829         struct fscache_object *dep;
 830         bool ret = true;
 831
 832         _enter("{OBJ%x}", object->debug_id);
 833
 834         if (list_empty(&object->dependents))
 835                 return true;
 836
 837         spin_lock(&object->lock);
 838
 839         while (!list_empty(&object->dependents)) {
 840                 dep = list_entry(object->dependents.next,
 841                                  struct fscache_object, dep_link);
 842                 list_del_init(&dep->dep_link);
 843
 844                 fscache_raise_event(dep, event);
 845                 fscache_put_object(dep);
 846
 847                 if (!list_empty(&object->dependents) && need_resched()) {
 848                         ret = false;
 849                         break;
 850                 }
 851         }
 852
 853         spin_unlock(&object->lock);
 854         return ret;
 855 }
 856
 857 /*
 858  * remove an object from whatever queue it's waiting on
 859  */
 860 static void fscache_dequeue_object(struct fscache_object *object)
 861 {
 862         _enter("{OBJ%x}", object->debug_id);
 863
 864         if (!list_empty(&object->dep_link)) {
 865                 spin_lock(&object->parent->lock);
 866                 list_del_init(&object->dep_link);
 867                 spin_unlock(&object->parent->lock);
 868         }
 869
 870         _leave("");
 871 }
 872
 873 /**
 874  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 875  * @object: The object to ask about
 876  * @data: The auxiliary data for the object
 877  * @datalen: The size of the auxiliary data
 878  *
 879  * This function consults the netfs about the coherency state of an object.
 880  * The caller must be holding a ref on cookie->n_active (held by
 881  * fscache_look_up_object() on behalf of the cache backend during object lookup
 882  * and creation).
 883  */
 884 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 885                                         const void *data, uint16_t datalen)
 886 {
 887         enum fscache_checkaux result;
 888
 889         if (!object->cookie->def->check_aux) {
 890                 fscache_stat(&fscache_n_checkaux_none);
 891                 return FSCACHE_CHECKAUX_OKAY;
 892         }
 893
 894         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 895                                                 data, datalen);
 896         switch (result) {
 897                 /* entry okay as is */
 898         case FSCACHE_CHECKAUX_OKAY:
 899                 fscache_stat(&fscache_n_checkaux_okay);
 900                 break;
 901
 902                 /* entry requires update */
 903         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 904                 fscache_stat(&fscache_n_checkaux_update);
 905                 break;
 906
 907                 /* entry requires deletion */
 908         case FSCACHE_CHECKAUX_OBSOLETE:
 909                 fscache_stat(&fscache_n_checkaux_obsolete);
 910                 break;
 911
 912         default:
 913                 BUG();
 914         }
 915
 916         return result;
 917 }
 918 EXPORT_SYMBOL(fscache_check_aux);
 919
 920 /*
 921  * Asynchronously invalidate an object.
 922  */
 923 static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
 924                                                               int event)
 925 {
 926         struct fscache_operation *op;
 927         struct fscache_cookie *cookie = object->cookie;
 928
 929         _enter("{OBJ%x},%d", object->debug_id, event);
 930
 931         /* We're going to need the cookie.  If the cookie is not available then
 932          * retire the object instead.
 933          */
 934         if (!fscache_use_cookie(object)) {
 935                 ASSERT(object->cookie->stores.rnode == NULL);
 936                 set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
 937                 _leave(" [no cookie]");
 938                 return transit_to(KILL_OBJECT);
 939         }
 940
 941         /* Reject any new read/write ops and abort any that are pending. */
 942         fscache_invalidate_writes(cookie);
 943         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 944         fscache_cancel_all_ops(object);
 945
 946         /* Now we have to wait for in-progress reads and writes */
 947         op = kzalloc(sizeof(*op), GFP_KERNEL);
 948         if (!op)
 949                 goto nomem;
 950
 951         fscache_operation_init(op, object->cache->ops->invalidate_object, NULL);
 952         op->flags = FSCACHE_OP_ASYNC |
 953                 (1 << FSCACHE_OP_EXCLUSIVE) |
 954                 (1 << FSCACHE_OP_UNUSE_COOKIE);
 955
 956         spin_lock(&cookie->lock);
 957         if (fscache_submit_exclusive_op(object, op) < 0)
 958                 goto submit_op_failed;
 959         spin_unlock(&cookie->lock);
 960         fscache_put_operation(op);
 961
 962         /* Once we've completed the invalidation, we know there will be no data
 963          * stored in the cache and thus we can reinstate the data-check-skip
 964          * optimisation.
 965          */
 966         set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 967
 968         /* We can allow read and write requests to come in once again.  They'll
 969          * queue up behind our exclusive invalidation operation.
 970          */
 971         if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 972                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 973         _leave(" [ok]");
 974         return transit_to(UPDATE_OBJECT);
 975
 976 nomem:
 977         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 978         fscache_unuse_cookie(object);
 979         _leave(" [ENOMEM]");
 980         return transit_to(KILL_OBJECT);
 981
 982 submit_op_failed:
 983         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 984         spin_unlock(&cookie->lock);
 985         kfree(op);
 986         _leave(" [EIO]");
 987         return transit_to(KILL_OBJECT);
 988 }
 989
 990 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
 991                                                              int event)
 992 {
 993         const struct fscache_state *s;
 994
 995         fscache_stat(&fscache_n_invalidates_run);
 996         fscache_stat(&fscache_n_cop_invalidate_object);
 997         s = _fscache_invalidate_object(object, event);
 998         fscache_stat_d(&fscache_n_cop_invalidate_object);
 999         return s;
1000 }
1001
1002 /*
1003  * Asynchronously update an object.
1004  */
1005 static const struct fscache_state *fscache_update_object(struct fscache_object *object,
1006                                                          int event)
1007 {
1008         _enter("{OBJ%x},%d", object->debug_id, event);
1009
1010         fscache_stat(&fscache_n_updates_run);
1011         fscache_stat(&fscache_n_cop_update_object);
1012         object->cache->ops->update_object(object);
1013         fscache_stat_d(&fscache_n_cop_update_object);
1014
1015         _leave("");
1016         return transit_to(WAIT_FOR_CMD);
1017 }