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         set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags);
 614
 615         cookie = object->cookie;
 616         set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 617         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
 618                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 619
 620         fscache_done_parent_op(object);
 621         return transit_to(KILL_OBJECT);
 622 }
 623
 624 /*
 625  * Wait for completion of all active operations on this object and the death of
 626  * all child objects of this object.
 627  */
 628 static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
 629                                                        int event)
 630 {
 631         _enter("{OBJ%x,%d,%d},%d",
 632                object->debug_id, object->n_ops, object->n_children, event);
 633
 634         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 635         object->oob_event_mask = 0;
 636
 637         if (list_empty(&object->dependents) &&
 638             object->n_ops == 0 &&
 639             object->n_children == 0)
 640                 return transit_to(DROP_OBJECT);
 641
 642         if (object->n_in_progress == 0) {
 643                 spin_lock(&object->lock);
 644                 if (object->n_ops > 0 && object->n_in_progress == 0)
 645                         fscache_start_operations(object);
 646                 spin_unlock(&object->lock);
 647         }
 648
 649         if (!list_empty(&object->dependents))
 650                 return transit_to(KILL_DEPENDENTS);
 651
 652         return transit_to(WAIT_FOR_CLEARANCE);
 653 }
 654
 655 /*
 656  * Kill dependent objects.
 657  */
 658 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
 659                                                            int event)
 660 {
 661         _enter("{OBJ%x},%d", object->debug_id, event);
 662
 663         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
 664                 return NO_TRANSIT; /* Not finished */
 665         return transit_to(WAIT_FOR_CLEARANCE);
 666 }
 667
 668 /*
 669  * Drop an object's attachments
 670  */
 671 static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
 672                                                        int event)
 673 {
 674         struct fscache_object *parent = object->parent;
 675         struct fscache_cookie *cookie = object->cookie;
 676         struct fscache_cache *cache = object->cache;
 677         bool awaken = false;
 678
 679         _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
 680
 681         ASSERT(cookie != NULL);
 682         ASSERT(!hlist_unhashed(&object->cookie_link));
 683
 684         /* Make sure the cookie no longer points here and that the netfs isn't
 685          * waiting for us.
 686          */
 687         spin_lock(&cookie->lock);
 688         hlist_del_init(&object->cookie_link);
 689         if (hlist_empty(&cookie->backing_objects) &&
 690             test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 691                 awaken = true;
 692         spin_unlock(&cookie->lock);
 693
 694         if (awaken)
 695                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 696
 697         /* Prevent a race with our last child, which has to signal EV_CLEARED
 698          * before dropping our spinlock.
 699          */
 700         spin_lock(&object->lock);
 701         spin_unlock(&object->lock);
 702
 703         /* Discard from the cache's collection of objects */
 704         spin_lock(&cache->object_list_lock);
 705         list_del_init(&object->cache_link);
 706         spin_unlock(&cache->object_list_lock);
 707
 708         fscache_stat(&fscache_n_cop_drop_object);
 709         cache->ops->drop_object(object);
 710         fscache_stat_d(&fscache_n_cop_drop_object);
 711
 712         /* The parent object wants to know when all it dependents have gone */
 713         if (parent) {
 714                 _debug("release parent OBJ%x {%d}",
 715                        parent->debug_id, parent->n_children);
 716
 717                 spin_lock(&parent->lock);
 718                 parent->n_children--;
 719                 if (parent->n_children == 0)
 720                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 721                 spin_unlock(&parent->lock);
 722                 object->parent = NULL;
 723         }
 724
 725         /* this just shifts the object release to the work processor */
 726         fscache_put_object(object);
 727         fscache_stat(&fscache_n_object_dead);
 728
 729         _leave("");
 730         return transit_to(OBJECT_DEAD);
 731 }
 732
 733 /*
 734  * get a ref on an object
 735  */
 736 static int fscache_get_object(struct fscache_object *object)
 737 {
 738         int ret;
 739
 740         fscache_stat(&fscache_n_cop_grab_object);
 741         ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 742         fscache_stat_d(&fscache_n_cop_grab_object);
 743         return ret;
 744 }
 745
 746 /*
 747  * Discard a ref on an object
 748  */
 749 static void fscache_put_object(struct fscache_object *object)
 750 {
 751         fscache_stat(&fscache_n_cop_put_object);
 752         object->cache->ops->put_object(object);
 753         fscache_stat_d(&fscache_n_cop_put_object);
 754 }
 755
 756 /**
 757  * fscache_object_destroy - Note that a cache object is about to be destroyed
 758  * @object: The object to be destroyed
 759  *
 760  * Note the imminent destruction and deallocation of a cache object record.
 761  */
 762 void fscache_object_destroy(struct fscache_object *object)
 763 {
 764         fscache_objlist_remove(object);
 765
 766         /* We can get rid of the cookie now */
 767         fscache_cookie_put(object->cookie);
 768         object->cookie = NULL;
 769 }
 770 EXPORT_SYMBOL(fscache_object_destroy);
 771
 772 /*
 773  * enqueue an object for metadata-type processing
 774  */
 775 void fscache_enqueue_object(struct fscache_object *object)
 776 {
 777         _enter("{OBJ%x}", object->debug_id);
 778
 779         if (fscache_get_object(object) >= 0) {
 780                 wait_queue_head_t *cong_wq =
 781                         &get_cpu_var(fscache_object_cong_wait);
 782
 783                 if (queue_work(fscache_object_wq, &object->work)) {
 784                         if (fscache_object_congested())
 785                                 wake_up(cong_wq);
 786                 } else
 787                         fscache_put_object(object);
 788
 789                 put_cpu_var(fscache_object_cong_wait);
 790         }
 791 }
 792
 793 /**
 794  * fscache_object_sleep_till_congested - Sleep until object wq is congested
 795  * @timeoutp: Scheduler sleep timeout
 796  *
 797  * Allow an object handler to sleep until the object workqueue is congested.
 798  *
 799  * The caller must set up a wake up event before calling this and must have set
 800  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 801  * condition before calling this function as no test is made here.
 802  *
 803  * %true is returned if the object wq is congested, %false otherwise.
 804  */
 805 bool fscache_object_sleep_till_congested(signed long *timeoutp)
 806 {
 807         wait_queue_head_t *cong_wq = this_cpu_ptr(&fscache_object_cong_wait);
 808         DEFINE_WAIT(wait);
 809
 810         if (fscache_object_congested())
 811                 return true;
 812
 813         add_wait_queue_exclusive(cong_wq, &wait);
 814         if (!fscache_object_congested())
 815                 *timeoutp = schedule_timeout(*timeoutp);
 816         finish_wait(cong_wq, &wait);
 817
 818         return fscache_object_congested();
 819 }
 820 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 821
 822 /*
 823  * Enqueue the dependents of an object for metadata-type processing.
 824  *
 825  * If we don't manage to finish the list before the scheduler wants to run
 826  * again then return false immediately.  We return true if the list was
 827  * cleared.
 828  */
 829 static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
 830 {
 831         struct fscache_object *dep;
 832         bool ret = true;
 833
 834         _enter("{OBJ%x}", object->debug_id);
 835
 836         if (list_empty(&object->dependents))
 837                 return true;
 838
 839         spin_lock(&object->lock);
 840
 841         while (!list_empty(&object->dependents)) {
 842                 dep = list_entry(object->dependents.next,
 843                                  struct fscache_object, dep_link);
 844                 list_del_init(&dep->dep_link);
 845
 846                 fscache_raise_event(dep, event);
 847                 fscache_put_object(dep);
 848
 849                 if (!list_empty(&object->dependents) && need_resched()) {
 850                         ret = false;
 851                         break;
 852                 }
 853         }
 854
 855         spin_unlock(&object->lock);
 856         return ret;
 857 }
 858
 859 /*
 860  * remove an object from whatever queue it's waiting on
 861  */
 862 static void fscache_dequeue_object(struct fscache_object *object)
 863 {
 864         _enter("{OBJ%x}", object->debug_id);
 865
 866         if (!list_empty(&object->dep_link)) {
 867                 spin_lock(&object->parent->lock);
 868                 list_del_init(&object->dep_link);
 869                 spin_unlock(&object->parent->lock);
 870         }
 871
 872         _leave("");
 873 }
 874
 875 /**
 876  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 877  * @object: The object to ask about
 878  * @data: The auxiliary data for the object
 879  * @datalen: The size of the auxiliary data
 880  *
 881  * This function consults the netfs about the coherency state of an object.
 882  * The caller must be holding a ref on cookie->n_active (held by
 883  * fscache_look_up_object() on behalf of the cache backend during object lookup
 884  * and creation).
 885  */
 886 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 887                                         const void *data, uint16_t datalen)
 888 {
 889         enum fscache_checkaux result;
 890
 891         if (!object->cookie->def->check_aux) {
 892                 fscache_stat(&fscache_n_checkaux_none);
 893                 return FSCACHE_CHECKAUX_OKAY;
 894         }
 895
 896         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 897                                                 data, datalen);
 898         switch (result) {
 899                 /* entry okay as is */
 900         case FSCACHE_CHECKAUX_OKAY:
 901                 fscache_stat(&fscache_n_checkaux_okay);
 902                 break;
 903
 904                 /* entry requires update */
 905         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 906                 fscache_stat(&fscache_n_checkaux_update);
 907                 break;
 908
 909                 /* entry requires deletion */
 910         case FSCACHE_CHECKAUX_OBSOLETE:
 911                 fscache_stat(&fscache_n_checkaux_obsolete);
 912                 break;
 913
 914         default:
 915                 BUG();
 916         }
 917
 918         return result;
 919 }
 920 EXPORT_SYMBOL(fscache_check_aux);
 921
 922 /*
 923  * Asynchronously invalidate an object.
 924  */
 925 static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
 926                                                               int event)
 927 {
 928         struct fscache_operation *op;
 929         struct fscache_cookie *cookie = object->cookie;
 930
 931         _enter("{OBJ%x},%d", object->debug_id, event);
 932
 933         /* We're going to need the cookie.  If the cookie is not available then
 934          * retire the object instead.
 935          */
 936         if (!fscache_use_cookie(object)) {
 937                 ASSERT(object->cookie->stores.rnode == NULL);
 938                 set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
 939                 _leave(" [no cookie]");
 940                 return transit_to(KILL_OBJECT);
 941         }
 942
 943         /* Reject any new read/write ops and abort any that are pending. */
 944         fscache_invalidate_writes(cookie);
 945         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 946         fscache_cancel_all_ops(object);
 947
 948         /* Now we have to wait for in-progress reads and writes */
 949         op = kzalloc(sizeof(*op), GFP_KERNEL);
 950         if (!op)
 951                 goto nomem;
 952
 953         fscache_operation_init(op, object->cache->ops->invalidate_object, NULL);
 954         op->flags = FSCACHE_OP_ASYNC |
 955                 (1 << FSCACHE_OP_EXCLUSIVE) |
 956                 (1 << FSCACHE_OP_UNUSE_COOKIE);
 957
 958         spin_lock(&cookie->lock);
 959         if (fscache_submit_exclusive_op(object, op) < 0)
 960                 goto submit_op_failed;
 961         spin_unlock(&cookie->lock);
 962         fscache_put_operation(op);
 963
 964         /* Once we've completed the invalidation, we know there will be no data
 965          * stored in the cache and thus we can reinstate the data-check-skip
 966          * optimisation.
 967          */
 968         set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 969
 970         /* We can allow read and write requests to come in once again.  They'll
 971          * queue up behind our exclusive invalidation operation.
 972          */
 973         if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 974                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 975         _leave(" [ok]");
 976         return transit_to(UPDATE_OBJECT);
 977
 978 nomem:
 979         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 980         fscache_unuse_cookie(object);
 981         _leave(" [ENOMEM]");
 982         return transit_to(KILL_OBJECT);
 983
 984 submit_op_failed:
 985         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 986         spin_unlock(&cookie->lock);
 987         fscache_unuse_cookie(object);
 988         kfree(op);
 989         _leave(" [EIO]");
 990         return transit_to(KILL_OBJECT);
 991 }
 992
 993 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
 994                                                              int event)
 995 {
 996         const struct fscache_state *s;
 997
 998         fscache_stat(&fscache_n_invalidates_run);
 999         fscache_stat(&fscache_n_cop_invalidate_object);
1000         s = _fscache_invalidate_object(object, event);
1001         fscache_stat_d(&fscache_n_cop_invalidate_object);
1002         return s;
1003 }
1004
1005 /*
1006  * Asynchronously update an object.
1007  */
1008 static const struct fscache_state *fscache_update_object(struct fscache_object *object,
1009                                                          int event)
1010 {
1011         _enter("{OBJ%x},%d", object->debug_id, event);
1012
1013         fscache_stat(&fscache_n_updates_run);
1014         fscache_stat(&fscache_n_cop_update_object);
1015         object->cache->ops->update_object(object);
1016         fscache_stat_d(&fscache_n_cop_update_object);
1017
1018         _leave("");
1019         return transit_to(WAIT_FOR_CMD);
1020 }
1021
1022 /**
1023  * fscache_object_retrying_stale - Note retrying stale object
1024  * @object: The object that will be retried
1025  *
1026  * Note that an object lookup found an on-disk object that was adjudged to be
1027  * stale and has been deleted.  The lookup will be retried.
1028  */
1029 void fscache_object_retrying_stale(struct fscache_object *object)
1030 {
1031         fscache_stat(&fscache_n_cache_no_space_reject);
1032 }
1033 EXPORT_SYMBOL(fscache_object_retrying_stale);
1034
1035 /**
1036  * fscache_object_mark_killed - Note that an object was killed
1037  * @object: The object that was culled
1038  * @why: The reason the object was killed.
1039  *
1040  * Note that an object was killed.  Returns true if the object was
1041  * already marked killed, false if it wasn't.
1042  */
1043 void fscache_object_mark_killed(struct fscache_object *object,
1044                                 enum fscache_why_object_killed why)
1045 {
1046         if (test_and_set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags)) {
1047                 pr_err("Error: Object already killed by cache [%s]\n",
1048                        object->cache->identifier);
1049                 return;
1050         }
1051
1052         switch (why) {
1053         case FSCACHE_OBJECT_NO_SPACE:
1054                 fscache_stat(&fscache_n_cache_no_space_reject);
1055                 break;
1056         case FSCACHE_OBJECT_IS_STALE:
1057                 fscache_stat(&fscache_n_cache_stale_objects);
1058                 break;
1059         case FSCACHE_OBJECT_WAS_RETIRED:
1060                 fscache_stat(&fscache_n_cache_retired_objects);
1061                 break;
1062         case FSCACHE_OBJECT_WAS_CULLED:
1063                 fscache_stat(&fscache_n_cache_culled_objects);
1064                 break;
1065         }
1066 }
1067 EXPORT_SYMBOL(fscache_object_mark_killed);