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         atomic_inc(&cookie->usage);
 317         object->parent = NULL;
 318 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 319         RB_CLEAR_NODE(&object->objlist_link);
 320 #endif
 321
 322         object->oob_event_mask = 0;
 323         for (t = object->oob_table; t->events; t++)
 324                 object->oob_event_mask |= t->events;
 325         object->event_mask = object->oob_event_mask;
 326         for (t = object->state->transitions; t->events; t++)
 327                 object->event_mask |= t->events;
 328 }
 329 EXPORT_SYMBOL(fscache_object_init);
 330
 331 /*
 332  * Abort object initialisation before we start it.
 333  */
 334 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
 335                                                                 int event)
 336 {
 337         _enter("{OBJ%x},%d", object->debug_id, event);
 338
 339         object->oob_event_mask = 0;
 340         fscache_dequeue_object(object);
 341         return transit_to(KILL_OBJECT);
 342 }
 343
 344 /*
 345  * initialise an object
 346  * - check the specified object's parent to see if we can make use of it
 347  *   immediately to do a creation
 348  * - we may need to start the process of creating a parent and we need to wait
 349  *   for the parent's lookup and creation to complete if it's not there yet
 350  */
 351 static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
 352                                                              int event)
 353 {
 354         struct fscache_object *parent;
 355         bool success;
 356
 357         _enter("{OBJ%x},%d", object->debug_id, event);
 358
 359         ASSERT(list_empty(&object->dep_link));
 360
 361         parent = object->parent;
 362         if (!parent) {
 363                 _leave(" [no parent]");
 364                 return transit_to(DROP_OBJECT);
 365         }
 366
 367         _debug("parent: %s of:%lx", parent->state->name, parent->flags);
 368
 369         if (fscache_object_is_dying(parent)) {
 370                 _leave(" [bad parent]");
 371                 return transit_to(DROP_OBJECT);
 372         }
 373
 374         if (fscache_object_is_available(parent)) {
 375                 _leave(" [ready]");
 376                 return transit_to(PARENT_READY);
 377         }
 378
 379         _debug("wait");
 380
 381         spin_lock(&parent->lock);
 382         fscache_stat(&fscache_n_cop_grab_object);
 383         success = false;
 384         if (fscache_object_is_live(parent) &&
 385             object->cache->ops->grab_object(object)) {
 386                 list_add(&object->dep_link, &parent->dependents);
 387                 success = true;
 388         }
 389         fscache_stat_d(&fscache_n_cop_grab_object);
 390         spin_unlock(&parent->lock);
 391         if (!success) {
 392                 _leave(" [grab failed]");
 393                 return transit_to(DROP_OBJECT);
 394         }
 395
 396         /* fscache_acquire_non_index_cookie() uses this
 397          * to wake the chain up */
 398         fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
 399         _leave(" [wait]");
 400         return transit_to(WAIT_FOR_PARENT);
 401 }
 402
 403 /*
 404  * Once the parent object is ready, we should kick off our lookup op.
 405  */
 406 static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
 407                                                         int event)
 408 {
 409         struct fscache_object *parent = object->parent;
 410
 411         _enter("{OBJ%x},%d", object->debug_id, event);
 412
 413         ASSERT(parent != NULL);
 414
 415         spin_lock(&parent->lock);
 416         parent->n_ops++;
 417         parent->n_obj_ops++;
 418         object->lookup_jif = jiffies;
 419         spin_unlock(&parent->lock);
 420
 421         _leave("");
 422         return transit_to(LOOK_UP_OBJECT);
 423 }
 424
 425 /*
 426  * look an object up in the cache from which it was allocated
 427  * - we hold an "access lock" on the parent object, so the parent object cannot
 428  *   be withdrawn by either party till we've finished
 429  */
 430 static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
 431                                                           int event)
 432 {
 433         struct fscache_cookie *cookie = object->cookie;
 434         struct fscache_object *parent = object->parent;
 435         int ret;
 436
 437         _enter("{OBJ%x},%d", object->debug_id, event);
 438
 439         object->oob_table = fscache_osm_lookup_oob;
 440
 441         ASSERT(parent != NULL);
 442         ASSERTCMP(parent->n_ops, >, 0);
 443         ASSERTCMP(parent->n_obj_ops, >, 0);
 444
 445         /* make sure the parent is still available */
 446         ASSERT(fscache_object_is_available(parent));
 447
 448         if (fscache_object_is_dying(parent) ||
 449             test_bit(FSCACHE_IOERROR, &object->cache->flags) ||
 450             !fscache_use_cookie(object)) {
 451                 _leave(" [unavailable]");
 452                 return transit_to(LOOKUP_FAILURE);
 453         }
 454
 455         _debug("LOOKUP \"%s\" in \"%s\"",
 456                cookie->def->name, object->cache->tag->name);
 457
 458         fscache_stat(&fscache_n_object_lookups);
 459         fscache_stat(&fscache_n_cop_lookup_object);
 460         ret = object->cache->ops->lookup_object(object);
 461         fscache_stat_d(&fscache_n_cop_lookup_object);
 462
 463         fscache_unuse_cookie(object);
 464
 465         if (ret == -ETIMEDOUT) {
 466                 /* probably stuck behind another object, so move this one to
 467                  * the back of the queue */
 468                 fscache_stat(&fscache_n_object_lookups_timed_out);
 469                 _leave(" [timeout]");
 470                 return NO_TRANSIT;
 471         }
 472
 473         if (ret < 0) {
 474                 _leave(" [error]");
 475                 return transit_to(LOOKUP_FAILURE);
 476         }
 477
 478         _leave(" [ok]");
 479         return transit_to(OBJECT_AVAILABLE);
 480 }
 481
 482 /**
 483  * fscache_object_lookup_negative - Note negative cookie lookup
 484  * @object: Object pointing to cookie to mark
 485  *
 486  * Note negative lookup, permitting those waiting to read data from an already
 487  * existing backing object to continue as there's no data for them to read.
 488  */
 489 void fscache_object_lookup_negative(struct fscache_object *object)
 490 {
 491         struct fscache_cookie *cookie = object->cookie;
 492
 493         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 494
 495         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 496                 fscache_stat(&fscache_n_object_lookups_negative);
 497
 498                 /* Allow write requests to begin stacking up and read requests to begin
 499                  * returning ENODATA.
 500                  */
 501                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 502                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 503
 504                 _debug("wake up lookup %p", &cookie->flags);
 505                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 506                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 507         }
 508         _leave("");
 509 }
 510 EXPORT_SYMBOL(fscache_object_lookup_negative);
 511
 512 /**
 513  * fscache_obtained_object - Note successful object lookup or creation
 514  * @object: Object pointing to cookie to mark
 515  *
 516  * Note successful lookup and/or creation, permitting those waiting to write
 517  * data to a backing object to continue.
 518  *
 519  * Note that after calling this, an object's cookie may be relinquished by the
 520  * netfs, and so must be accessed with object lock held.
 521  */
 522 void fscache_obtained_object(struct fscache_object *object)
 523 {
 524         struct fscache_cookie *cookie = object->cookie;
 525
 526         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 527
 528         /* if we were still looking up, then we must have a positive lookup
 529          * result, in which case there may be data available */
 530         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 531                 fscache_stat(&fscache_n_object_lookups_positive);
 532
 533                 /* We do (presumably) have data */
 534                 clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 535                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 536
 537                 /* Allow write requests to begin stacking up and read requests
 538                  * to begin shovelling data.
 539                  */
 540                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 541                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 542         } else {
 543                 fscache_stat(&fscache_n_object_created);
 544         }
 545
 546         set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
 547         _leave("");
 548 }
 549 EXPORT_SYMBOL(fscache_obtained_object);
 550
 551 /*
 552  * handle an object that has just become available
 553  */
 554 static const struct fscache_state *fscache_object_available(struct fscache_object *object,
 555                                                             int event)
 556 {
 557         _enter("{OBJ%x},%d", object->debug_id, event);
 558
 559         object->oob_table = fscache_osm_run_oob;
 560
 561         spin_lock(&object->lock);
 562
 563         fscache_done_parent_op(object);
 564         if (object->n_in_progress == 0) {
 565                 if (object->n_ops > 0) {
 566                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 567                         fscache_start_operations(object);
 568                 } else {
 569                         ASSERT(list_empty(&object->pending_ops));
 570                 }
 571         }
 572         spin_unlock(&object->lock);
 573
 574         fscache_stat(&fscache_n_cop_lookup_complete);
 575         object->cache->ops->lookup_complete(object);
 576         fscache_stat_d(&fscache_n_cop_lookup_complete);
 577
 578         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 579         fscache_stat(&fscache_n_object_avail);
 580
 581         _leave("");
 582         return transit_to(JUMPSTART_DEPS);
 583 }
 584
 585 /*
 586  * Wake up this object's dependent objects now that we've become available.
 587  */
 588 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
 589                                                                 int event)
 590 {
 591         _enter("{OBJ%x},%d", object->debug_id, event);
 592
 593         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
 594                 return NO_TRANSIT; /* Not finished; requeue */
 595         return transit_to(WAIT_FOR_CMD);
 596 }
 597
 598 /*
 599  * Handle lookup or creation failute.
 600  */
 601 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
 602                                                           int event)
 603 {
 604         struct fscache_cookie *cookie;
 605
 606         _enter("{OBJ%x},%d", object->debug_id, event);
 607
 608         object->oob_event_mask = 0;
 609
 610         fscache_stat(&fscache_n_cop_lookup_complete);
 611         object->cache->ops->lookup_complete(object);
 612         fscache_stat_d(&fscache_n_cop_lookup_complete);
 613
 614         cookie = object->cookie;
 615         set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 616         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
 617                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 618
 619         fscache_done_parent_op(object);
 620         return transit_to(KILL_OBJECT);
 621 }
 622
 623 /*
 624  * Wait for completion of all active operations on this object and the death of
 625  * all child objects of this object.
 626  */
 627 static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
 628                                                        int event)
 629 {
 630         _enter("{OBJ%x,%d,%d},%d",
 631                object->debug_id, object->n_ops, object->n_children, event);
 632
 633         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 634         object->oob_event_mask = 0;
 635
 636         if (list_empty(&object->dependents) &&
 637             object->n_ops == 0 &&
 638             object->n_children == 0)
 639                 return transit_to(DROP_OBJECT);
 640
 641         if (object->n_in_progress == 0) {
 642                 spin_lock(&object->lock);
 643                 if (object->n_ops > 0 && object->n_in_progress == 0)
 644                         fscache_start_operations(object);
 645                 spin_unlock(&object->lock);
 646         }
 647
 648         if (!list_empty(&object->dependents))
 649                 return transit_to(KILL_DEPENDENTS);
 650
 651         return transit_to(WAIT_FOR_CLEARANCE);
 652 }
 653
 654 /*
 655  * Kill dependent objects.
 656  */
 657 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
 658                                                            int event)
 659 {
 660         _enter("{OBJ%x},%d", object->debug_id, event);
 661
 662         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
 663                 return NO_TRANSIT; /* Not finished */
 664         return transit_to(WAIT_FOR_CLEARANCE);
 665 }
 666
 667 /*
 668  * Drop an object's attachments
 669  */
 670 static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
 671                                                        int event)
 672 {
 673         struct fscache_object *parent = object->parent;
 674         struct fscache_cookie *cookie = object->cookie;
 675         struct fscache_cache *cache = object->cache;
 676         bool awaken = false;
 677
 678         _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
 679
 680         ASSERT(cookie != NULL);
 681         ASSERT(!hlist_unhashed(&object->cookie_link));
 682
 683         /* Make sure the cookie no longer points here and that the netfs isn't
 684          * waiting for us.
 685          */
 686         spin_lock(&cookie->lock);
 687         hlist_del_init(&object->cookie_link);
 688         if (hlist_empty(&cookie->backing_objects) &&
 689             test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 690                 awaken = true;
 691         spin_unlock(&cookie->lock);
 692
 693         if (awaken)
 694                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 695
 696         /* Prevent a race with our last child, which has to signal EV_CLEARED
 697          * before dropping our spinlock.
 698          */
 699         spin_lock(&object->lock);
 700         spin_unlock(&object->lock);
 701
 702         /* Discard from the cache's collection of objects */
 703         spin_lock(&cache->object_list_lock);
 704         list_del_init(&object->cache_link);
 705         spin_unlock(&cache->object_list_lock);
 706
 707         fscache_stat(&fscache_n_cop_drop_object);
 708         cache->ops->drop_object(object);
 709         fscache_stat_d(&fscache_n_cop_drop_object);
 710
 711         /* The parent object wants to know when all it dependents have gone */
 712         if (parent) {
 713                 _debug("release parent OBJ%x {%d}",
 714                        parent->debug_id, parent->n_children);
 715
 716                 spin_lock(&parent->lock);
 717                 parent->n_children--;
 718                 if (parent->n_children == 0)
 719                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 720                 spin_unlock(&parent->lock);
 721                 object->parent = NULL;
 722         }
 723
 724         /* this just shifts the object release to the work processor */
 725         fscache_put_object(object);
 726         fscache_stat(&fscache_n_object_dead);
 727
 728         _leave("");
 729         return transit_to(OBJECT_DEAD);
 730 }
 731
 732 /*
 733  * get a ref on an object
 734  */
 735 static int fscache_get_object(struct fscache_object *object)
 736 {
 737         int ret;
 738
 739         fscache_stat(&fscache_n_cop_grab_object);
 740         ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 741         fscache_stat_d(&fscache_n_cop_grab_object);
 742         return ret;
 743 }
 744
 745 /*
 746  * Discard a ref on an object
 747  */
 748 static void fscache_put_object(struct fscache_object *object)
 749 {
 750         fscache_stat(&fscache_n_cop_put_object);
 751         object->cache->ops->put_object(object);
 752         fscache_stat_d(&fscache_n_cop_put_object);
 753 }
 754
 755 /**
 756  * fscache_object_destroy - Note that a cache object is about to be destroyed
 757  * @object: The object to be destroyed
 758  *
 759  * Note the imminent destruction and deallocation of a cache object record.
 760  */
 761 void fscache_object_destroy(struct fscache_object *object)
 762 {
 763         fscache_objlist_remove(object);
 764
 765         /* We can get rid of the cookie now */
 766         fscache_cookie_put(object->cookie);
 767         object->cookie = NULL;
 768 }
 769 EXPORT_SYMBOL(fscache_object_destroy);
 770
 771 /*
 772  * enqueue an object for metadata-type processing
 773  */
 774 void fscache_enqueue_object(struct fscache_object *object)
 775 {
 776         _enter("{OBJ%x}", object->debug_id);
 777
 778         if (fscache_get_object(object) >= 0) {
 779                 wait_queue_head_t *cong_wq =
 780                         &get_cpu_var(fscache_object_cong_wait);
 781
 782                 if (queue_work(fscache_object_wq, &object->work)) {
 783                         if (fscache_object_congested())
 784                                 wake_up(cong_wq);
 785                 } else
 786                         fscache_put_object(object);
 787
 788                 put_cpu_var(fscache_object_cong_wait);
 789         }
 790 }
 791
 792 /**
 793  * fscache_object_sleep_till_congested - Sleep until object wq is congested
 794  * @timeoutp: Scheduler sleep timeout
 795  *
 796  * Allow an object handler to sleep until the object workqueue is congested.
 797  *
 798  * The caller must set up a wake up event before calling this and must have set
 799  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 800  * condition before calling this function as no test is made here.
 801  *
 802  * %true is returned if the object wq is congested, %false otherwise.
 803  */
 804 bool fscache_object_sleep_till_congested(signed long *timeoutp)
 805 {
 806         wait_queue_head_t *cong_wq = this_cpu_ptr(&fscache_object_cong_wait);
 807         DEFINE_WAIT(wait);
 808
 809         if (fscache_object_congested())
 810                 return true;
 811
 812         add_wait_queue_exclusive(cong_wq, &wait);
 813         if (!fscache_object_congested())
 814                 *timeoutp = schedule_timeout(*timeoutp);
 815         finish_wait(cong_wq, &wait);
 816
 817         return fscache_object_congested();
 818 }
 819 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 820
 821 /*
 822  * Enqueue the dependents of an object for metadata-type processing.
 823  *
 824  * If we don't manage to finish the list before the scheduler wants to run
 825  * again then return false immediately.  We return true if the list was
 826  * cleared.
 827  */
 828 static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
 829 {
 830         struct fscache_object *dep;
 831         bool ret = true;
 832
 833         _enter("{OBJ%x}", object->debug_id);
 834
 835         if (list_empty(&object->dependents))
 836                 return true;
 837
 838         spin_lock(&object->lock);
 839
 840         while (!list_empty(&object->dependents)) {
 841                 dep = list_entry(object->dependents.next,
 842                                  struct fscache_object, dep_link);
 843                 list_del_init(&dep->dep_link);
 844
 845                 fscache_raise_event(dep, event);
 846                 fscache_put_object(dep);
 847
 848                 if (!list_empty(&object->dependents) && need_resched()) {
 849                         ret = false;
 850                         break;
 851                 }
 852         }
 853
 854         spin_unlock(&object->lock);
 855         return ret;
 856 }
 857
 858 /*
 859  * remove an object from whatever queue it's waiting on
 860  */
 861 static void fscache_dequeue_object(struct fscache_object *object)
 862 {
 863         _enter("{OBJ%x}", object->debug_id);
 864
 865         if (!list_empty(&object->dep_link)) {
 866                 spin_lock(&object->parent->lock);
 867                 list_del_init(&object->dep_link);
 868                 spin_unlock(&object->parent->lock);
 869         }
 870
 871         _leave("");
 872 }
 873
 874 /**
 875  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 876  * @object: The object to ask about
 877  * @data: The auxiliary data for the object
 878  * @datalen: The size of the auxiliary data
 879  *
 880  * This function consults the netfs about the coherency state of an object.
 881  * The caller must be holding a ref on cookie->n_active (held by
 882  * fscache_look_up_object() on behalf of the cache backend during object lookup
 883  * and creation).
 884  */
 885 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 886                                         const void *data, uint16_t datalen)
 887 {
 888         enum fscache_checkaux result;
 889
 890         if (!object->cookie->def->check_aux) {
 891                 fscache_stat(&fscache_n_checkaux_none);
 892                 return FSCACHE_CHECKAUX_OKAY;
 893         }
 894
 895         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 896                                                 data, datalen);
 897         switch (result) {
 898                 /* entry okay as is */
 899         case FSCACHE_CHECKAUX_OKAY:
 900                 fscache_stat(&fscache_n_checkaux_okay);
 901                 break;
 902
 903                 /* entry requires update */
 904         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 905                 fscache_stat(&fscache_n_checkaux_update);
 906                 break;
 907
 908                 /* entry requires deletion */
 909         case FSCACHE_CHECKAUX_OBSOLETE:
 910                 fscache_stat(&fscache_n_checkaux_obsolete);
 911                 break;
 912
 913         default:
 914                 BUG();
 915         }
 916
 917         return result;
 918 }
 919 EXPORT_SYMBOL(fscache_check_aux);
 920
 921 /*
 922  * Asynchronously invalidate an object.
 923  */
 924 static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
 925                                                               int event)
 926 {
 927         struct fscache_operation *op;
 928         struct fscache_cookie *cookie = object->cookie;
 929
 930         _enter("{OBJ%x},%d", object->debug_id, event);
 931
 932         /* We're going to need the cookie.  If the cookie is not available then
 933          * retire the object instead.
 934          */
 935         if (!fscache_use_cookie(object)) {
 936                 ASSERT(object->cookie->stores.rnode == NULL);
 937                 set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
 938                 _leave(" [no cookie]");
 939                 return transit_to(KILL_OBJECT);
 940         }
 941
 942         /* Reject any new read/write ops and abort any that are pending. */
 943         fscache_invalidate_writes(cookie);
 944         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 945         fscache_cancel_all_ops(object);
 946
 947         /* Now we have to wait for in-progress reads and writes */
 948         op = kzalloc(sizeof(*op), GFP_KERNEL);
 949         if (!op)
 950                 goto nomem;
 951
 952         fscache_operation_init(op, object->cache->ops->invalidate_object, NULL);
 953         op->flags = FSCACHE_OP_ASYNC |
 954                 (1 << FSCACHE_OP_EXCLUSIVE) |
 955                 (1 << FSCACHE_OP_UNUSE_COOKIE);
 956
 957         spin_lock(&cookie->lock);
 958         if (fscache_submit_exclusive_op(object, op) < 0)
 959                 goto submit_op_failed;
 960         spin_unlock(&cookie->lock);
 961         fscache_put_operation(op);
 962
 963         /* Once we've completed the invalidation, we know there will be no data
 964          * stored in the cache and thus we can reinstate the data-check-skip
 965          * optimisation.
 966          */
 967         set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 968
 969         /* We can allow read and write requests to come in once again.  They'll
 970          * queue up behind our exclusive invalidation operation.
 971          */
 972         if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 973                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 974         _leave(" [ok]");
 975         return transit_to(UPDATE_OBJECT);
 976
 977 nomem:
 978         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 979         fscache_unuse_cookie(object);
 980         _leave(" [ENOMEM]");
 981         return transit_to(KILL_OBJECT);
 982
 983 submit_op_failed:
 984         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 985         spin_unlock(&cookie->lock);
 986         kfree(op);
 987         _leave(" [EIO]");
 988         return transit_to(KILL_OBJECT);
 989 }
 990
 991 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
 992                                                              int event)
 993 {
 994         const struct fscache_state *s;
 995
 996         fscache_stat(&fscache_n_invalidates_run);
 997         fscache_stat(&fscache_n_cop_invalidate_object);
 998         s = _fscache_invalidate_object(object, event);
 999         fscache_stat_d(&fscache_n_cop_invalidate_object);
1000         return s;
1001 }
1002
1003 /*
1004  * Asynchronously update an object.
1005  */
1006 static const struct fscache_state *fscache_update_object(struct fscache_object *object,
1007                                                          int event)
1008 {
1009         _enter("{OBJ%x},%d", object->debug_id, event);
1010
1011         fscache_stat(&fscache_n_updates_run);
1012         fscache_stat(&fscache_n_cop_update_object);
1013         object->cache->ops->update_object(object);
1014         fscache_stat_d(&fscache_n_cop_update_object);
1015
1016         _leave("");
1017         return transit_to(WAIT_FOR_CMD);
1018 }