fs/fscache/object.c

   1 /* FS-Cache object state machine handler
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  *
  11  * See Documentation/filesystems/caching/object.txt for a description of the
  12  * object state machine and the in-kernel representations.
  13  */
  14
  15 #define FSCACHE_DEBUG_LEVEL COOKIE
  16 #include <linux/module.h>
  17 #include <linux/slab.h>
  18 #include <linux/prefetch.h>
  19 #include "internal.h"
  20
  21 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *, int);
  22 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *, int);
  23 static const struct fscache_state *fscache_drop_object(struct fscache_object *, int);
  24 static const struct fscache_state *fscache_initialise_object(struct fscache_object *, int);
  25 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *, int);
  26 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *, int);
  27 static const struct fscache_state *fscache_kill_object(struct fscache_object *, int);
  28 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *, int);
  29 static const struct fscache_state *fscache_look_up_object(struct fscache_object *, int);
  30 static const struct fscache_state *fscache_object_available(struct fscache_object *, int);
  31 static const struct fscache_state *fscache_parent_ready(struct fscache_object *, int);
  32 static const struct fscache_state *fscache_update_object(struct fscache_object *, int);
  33 static const struct fscache_state *fscache_object_dead(struct fscache_object *, int);
  34
  35 #define __STATE_NAME(n) fscache_osm_##n
  36 #define STATE(n) (&__STATE_NAME(n))
  37
  38 /*
  39  * Define a work state.  Work states are execution states.  No event processing
  40  * is performed by them.  The function attached to a work state returns a
  41  * pointer indicating the next state to which the state machine should
  42  * transition.  Returning NO_TRANSIT repeats the current state, but goes back
  43  * to the scheduler first.
  44  */
  45 #define WORK_STATE(n, sn, f) \
  46         const struct fscache_state __STATE_NAME(n) = {                  \
  47                 .name = #n,                                             \
  48                 .short_name = sn,                                       \
  49                 .work = f                                               \
  50         }
  51
  52 /*
  53  * Returns from work states.
  54  */
  55 #define transit_to(state) ({ prefetch(&STATE(state)->work); STATE(state); })
  56
  57 #define NO_TRANSIT ((struct fscache_state *)NULL)
  58
  59 /*
  60  * Define a wait state.  Wait states are event processing states.  No execution
  61  * is performed by them.  Wait states are just tables of "if event X occurs,
  62  * clear it and transition to state Y".  The dispatcher returns to the
  63  * scheduler if none of the events in which the wait state has an interest are
  64  * currently pending.
  65  */
  66 #define WAIT_STATE(n, sn, ...) \
  67         const struct fscache_state __STATE_NAME(n) = {                  \
  68                 .name = #n,                                             \
  69                 .short_name = sn,                                       \
  70                 .work = NULL,                                           \
  71                 .transitions = { __VA_ARGS__, { 0, NULL } }             \
  72         }
  73
  74 #define TRANSIT_TO(state, emask) \
  75         { .events = (emask), .transit_to = STATE(state) }
  76
  77 /*
  78  * The object state machine.
  79  */
  80 static WORK_STATE(INIT_OBJECT,          "INIT", fscache_initialise_object);
  81 static WORK_STATE(PARENT_READY,         "PRDY", fscache_parent_ready);
  82 static WORK_STATE(ABORT_INIT,           "ABRT", fscache_abort_initialisation);
  83 static WORK_STATE(LOOK_UP_OBJECT,       "LOOK", fscache_look_up_object);
  84 static WORK_STATE(CREATE_OBJECT,        "CRTO", fscache_look_up_object);
  85 static WORK_STATE(OBJECT_AVAILABLE,     "AVBL", fscache_object_available);
  86 static WORK_STATE(JUMPSTART_DEPS,       "JUMP", fscache_jumpstart_dependents);
  87
  88 static WORK_STATE(INVALIDATE_OBJECT,    "INVL", fscache_invalidate_object);
  89 static WORK_STATE(UPDATE_OBJECT,        "UPDT", fscache_update_object);
  90
  91 static WORK_STATE(LOOKUP_FAILURE,       "LCFL", fscache_lookup_failure);
  92 static WORK_STATE(KILL_OBJECT,          "KILL", fscache_kill_object);
  93 static WORK_STATE(KILL_DEPENDENTS,      "KDEP", fscache_kill_dependents);
  94 static WORK_STATE(DROP_OBJECT,          "DROP", fscache_drop_object);
  95 static WORK_STATE(OBJECT_DEAD,          "DEAD", fscache_object_dead);
  96
  97 static WAIT_STATE(WAIT_FOR_INIT,        "?INI",
  98                   TRANSIT_TO(INIT_OBJECT,       1 << FSCACHE_OBJECT_EV_NEW_CHILD));
  99
 100 static WAIT_STATE(WAIT_FOR_PARENT,      "?PRN",
 101                   TRANSIT_TO(PARENT_READY,      1 << FSCACHE_OBJECT_EV_PARENT_READY));
 102
 103 static WAIT_STATE(WAIT_FOR_CMD,         "?CMD",
 104                   TRANSIT_TO(INVALIDATE_OBJECT, 1 << FSCACHE_OBJECT_EV_INVALIDATE),
 105                   TRANSIT_TO(UPDATE_OBJECT,     1 << FSCACHE_OBJECT_EV_UPDATE),
 106                   TRANSIT_TO(JUMPSTART_DEPS,    1 << FSCACHE_OBJECT_EV_NEW_CHILD));
 107
 108 static WAIT_STATE(WAIT_FOR_CLEARANCE,   "?CLR",
 109                   TRANSIT_TO(KILL_OBJECT,       1 << FSCACHE_OBJECT_EV_CLEARED));
 110
 111 /*
 112  * Out-of-band event transition tables.  These are for handling unexpected
 113  * events, such as an I/O error.  If an OOB event occurs, the state machine
 114  * clears and disables the event and forces a transition to the nominated work
 115  * state (acurrently executing work states will complete first).
 116  *
 117  * In such a situation, object->state remembers the state the machine should
 118  * have been in/gone to and returning NO_TRANSIT returns to that.
 119  */
 120 static const struct fscache_transition fscache_osm_init_oob[] = {
 121            TRANSIT_TO(ABORT_INIT,
 122                       (1 << FSCACHE_OBJECT_EV_ERROR) |
 123                       (1 << FSCACHE_OBJECT_EV_KILL)),
 124            { 0, NULL }
 125 };
 126
 127 static const struct fscache_transition fscache_osm_lookup_oob[] = {
 128            TRANSIT_TO(LOOKUP_FAILURE,
 129                       (1 << FSCACHE_OBJECT_EV_ERROR) |
 130                       (1 << FSCACHE_OBJECT_EV_KILL)),
 131            { 0, NULL }
 132 };
 133
 134 static const struct fscache_transition fscache_osm_run_oob[] = {
 135            TRANSIT_TO(KILL_OBJECT,
 136                       (1 << FSCACHE_OBJECT_EV_ERROR) |
 137                       (1 << FSCACHE_OBJECT_EV_KILL)),
 138            { 0, NULL }
 139 };
 140
 141 static int  fscache_get_object(struct fscache_object *);
 142 static void fscache_put_object(struct fscache_object *);
 143 static bool fscache_enqueue_dependents(struct fscache_object *, int);
 144 static void fscache_dequeue_object(struct fscache_object *);
 145
 146 /*
 147  * we need to notify the parent when an op completes that we had outstanding
 148  * upon it
 149  */
 150 static inline void fscache_done_parent_op(struct fscache_object *object)
 151 {
 152         struct fscache_object *parent = object->parent;
 153
 154         _enter("OBJ%x {OBJ%x,%x}",
 155                object->debug_id, parent->debug_id, parent->n_ops);
 156
 157         spin_lock_nested(&parent->lock, 1);
 158         parent->n_obj_ops--;
 159         parent->n_ops--;
 160         if (parent->n_ops == 0)
 161                 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 162         spin_unlock(&parent->lock);
 163 }
 164
 165 /*
 166  * Object state machine dispatcher.
 167  */
 168 static void fscache_object_sm_dispatcher(struct fscache_object *object)
 169 {
 170         const struct fscache_transition *t;
 171         const struct fscache_state *state, *new_state;
 172         unsigned long events, event_mask;
 173         int event = -1;
 174
 175         ASSERT(object != NULL);
 176
 177         _enter("{OBJ%x,%s,%lx}",
 178                object->debug_id, object->state->name, object->events);
 179
 180         event_mask = object->event_mask;
 181 restart:
 182         object->event_mask = 0; /* Mask normal event handling */
 183         state = object->state;
 184 restart_masked:
 185         events = object->events;
 186
 187         /* Handle any out-of-band events (typically an error) */
 188         if (events & object->oob_event_mask) {
 189                 _debug("{OBJ%x} oob %lx",
 190                        object->debug_id, events & object->oob_event_mask);
 191                 for (t = object->oob_table; t->events; t++) {
 192                         if (events & t->events) {
 193                                 state = t->transit_to;
 194                                 ASSERT(state->work != NULL);
 195                                 event = fls(events & t->events) - 1;
 196                                 __clear_bit(event, &object->oob_event_mask);
 197                                 clear_bit(event, &object->events);
 198                                 goto execute_work_state;
 199                         }
 200                 }
 201         }
 202
 203         /* Wait states are just transition tables */
 204         if (!state->work) {
 205                 if (events & event_mask) {
 206                         for (t = state->transitions; t->events; t++) {
 207                                 if (events & t->events) {
 208                                         new_state = t->transit_to;
 209                                         event = fls(events & t->events) - 1;
 210                                         clear_bit(event, &object->events);
 211                                         _debug("{OBJ%x} ev %d: %s -> %s",
 212                                                object->debug_id, event,
 213                                                state->name, new_state->name);
 214                                         object->state = state = new_state;
 215                                         goto execute_work_state;
 216                                 }
 217                         }
 218
 219                         /* The event mask didn't include all the tabled bits */
 220                         BUG();
 221                 }
 222                 /* Randomly woke up */
 223                 goto unmask_events;
 224         }
 225
 226 execute_work_state:
 227         _debug("{OBJ%x} exec %s", object->debug_id, state->name);
 228
 229         new_state = state->work(object, event);
 230         event = -1;
 231         if (new_state == NO_TRANSIT) {
 232                 _debug("{OBJ%x} %s notrans", object->debug_id, state->name);
 233                 if (unlikely(state == STATE(OBJECT_DEAD))) {
 234                         _leave(" [dead]");
 235                         return;
 236                 }
 237                 fscache_enqueue_object(object);
 238                 event_mask = object->oob_event_mask;
 239                 goto unmask_events;
 240         }
 241
 242         _debug("{OBJ%x} %s -> %s",
 243                object->debug_id, state->name, new_state->name);
 244         object->state = state = new_state;
 245
 246         if (state->work) {
 247                 if (unlikely(state == STATE(OBJECT_DEAD))) {
 248                         _leave(" [dead]");
 249                         return;
 250                 }
 251                 goto restart_masked;
 252         }
 253
 254         /* Transited to wait state */
 255         event_mask = object->oob_event_mask;
 256         for (t = state->transitions; t->events; t++)
 257                 event_mask |= t->events;
 258
 259 unmask_events:
 260         object->event_mask = event_mask;
 261         smp_mb();
 262         events = object->events;
 263         if (events & event_mask)
 264                 goto restart;
 265         _leave(" [msk %lx]", event_mask);
 266 }
 267
 268 /*
 269  * execute an object
 270  */
 271 static void fscache_object_work_func(struct work_struct *work)
 272 {
 273         struct fscache_object *object =
 274                 container_of(work, struct fscache_object, work);
 275         unsigned long start;
 276
 277         _enter("{OBJ%x}", object->debug_id);
 278
 279         start = jiffies;
 280         fscache_object_sm_dispatcher(object);
 281         fscache_hist(fscache_objs_histogram, start);
 282         fscache_put_object(object);
 283 }
 284
 285 /**
 286  * fscache_object_init - Initialise a cache object description
 287  * @object: Object description
 288  * @cookie: Cookie object will be attached to
 289  * @cache: Cache in which backing object will be found
 290  *
 291  * Initialise a cache object description to its basic values.
 292  *
 293  * See Documentation/filesystems/caching/backend-api.txt for a complete
 294  * description.
 295  */
 296 void fscache_object_init(struct fscache_object *object,
 297                          struct fscache_cookie *cookie,
 298                          struct fscache_cache *cache)
 299 {
 300         const struct fscache_transition *t;
 301
 302         atomic_inc(&cache->object_count);
 303
 304         object->state = STATE(WAIT_FOR_INIT);
 305         object->oob_table = fscache_osm_init_oob;
 306         object->flags = 1 << FSCACHE_OBJECT_IS_LIVE;
 307         spin_lock_init(&object->lock);
 308         INIT_LIST_HEAD(&object->cache_link);
 309         INIT_HLIST_NODE(&object->cookie_link);
 310         INIT_WORK(&object->work, fscache_object_work_func);
 311         INIT_LIST_HEAD(&object->dependents);
 312         INIT_LIST_HEAD(&object->dep_link);
 313         INIT_LIST_HEAD(&object->pending_ops);
 314         object->n_children = 0;
 315         object->n_ops = object->n_in_progress = object->n_exclusive = 0;
 316         object->events = 0;
 317         object->store_limit = 0;
 318         object->store_limit_l = 0;
 319         object->cache = cache;
 320         object->cookie = cookie;
 321         object->parent = NULL;
 322 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 323         RB_CLEAR_NODE(&object->objlist_link);
 324 #endif
 325
 326         object->oob_event_mask = 0;
 327         for (t = object->oob_table; t->events; t++)
 328                 object->oob_event_mask |= t->events;
 329         object->event_mask = object->oob_event_mask;
 330         for (t = object->state->transitions; t->events; t++)
 331                 object->event_mask |= t->events;
 332 }
 333 EXPORT_SYMBOL(fscache_object_init);
 334
 335 /*
 336  * Mark the object as no longer being live, making sure that we synchronise
 337  * against op submission.
 338  */
 339 static inline void fscache_mark_object_dead(struct fscache_object *object)
 340 {
 341         spin_lock(&object->lock);
 342         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 343         spin_unlock(&object->lock);
 344 }
 345
 346 /*
 347  * Abort object initialisation before we start it.
 348  */
 349 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
 350                                                                 int event)
 351 {
 352         _enter("{OBJ%x},%d", object->debug_id, event);
 353
 354         object->oob_event_mask = 0;
 355         fscache_dequeue_object(object);
 356         return transit_to(KILL_OBJECT);
 357 }
 358
 359 /*
 360  * initialise an object
 361  * - check the specified object's parent to see if we can make use of it
 362  *   immediately to do a creation
 363  * - we may need to start the process of creating a parent and we need to wait
 364  *   for the parent's lookup and creation to complete if it's not there yet
 365  */
 366 static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
 367                                                              int event)
 368 {
 369         struct fscache_object *parent;
 370         bool success;
 371
 372         _enter("{OBJ%x},%d", object->debug_id, event);
 373
 374         ASSERT(list_empty(&object->dep_link));
 375
 376         parent = object->parent;
 377         if (!parent) {
 378                 _leave(" [no parent]");
 379                 return transit_to(DROP_OBJECT);
 380         }
 381
 382         _debug("parent: %s of:%lx", parent->state->name, parent->flags);
 383
 384         if (fscache_object_is_dying(parent)) {
 385                 _leave(" [bad parent]");
 386                 return transit_to(DROP_OBJECT);
 387         }
 388
 389         if (fscache_object_is_available(parent)) {
 390                 _leave(" [ready]");
 391                 return transit_to(PARENT_READY);
 392         }
 393
 394         _debug("wait");
 395
 396         spin_lock(&parent->lock);
 397         fscache_stat(&fscache_n_cop_grab_object);
 398         success = false;
 399         if (fscache_object_is_live(parent) &&
 400             object->cache->ops->grab_object(object)) {
 401                 list_add(&object->dep_link, &parent->dependents);
 402                 success = true;
 403         }
 404         fscache_stat_d(&fscache_n_cop_grab_object);
 405         spin_unlock(&parent->lock);
 406         if (!success) {
 407                 _leave(" [grab failed]");
 408                 return transit_to(DROP_OBJECT);
 409         }
 410
 411         /* fscache_acquire_non_index_cookie() uses this
 412          * to wake the chain up */
 413         fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
 414         _leave(" [wait]");
 415         return transit_to(WAIT_FOR_PARENT);
 416 }
 417
 418 /*
 419  * Once the parent object is ready, we should kick off our lookup op.
 420  */
 421 static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
 422                                                         int event)
 423 {
 424         struct fscache_object *parent = object->parent;
 425
 426         _enter("{OBJ%x},%d", object->debug_id, event);
 427
 428         ASSERT(parent != NULL);
 429
 430         spin_lock(&parent->lock);
 431         parent->n_ops++;
 432         parent->n_obj_ops++;
 433         object->lookup_jif = jiffies;
 434         spin_unlock(&parent->lock);
 435
 436         _leave("");
 437         return transit_to(LOOK_UP_OBJECT);
 438 }
 439
 440 /*
 441  * look an object up in the cache from which it was allocated
 442  * - we hold an "access lock" on the parent object, so the parent object cannot
 443  *   be withdrawn by either party till we've finished
 444  */
 445 static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
 446                                                           int event)
 447 {
 448         struct fscache_cookie *cookie = object->cookie;
 449         struct fscache_object *parent = object->parent;
 450         int ret;
 451
 452         _enter("{OBJ%x},%d", object->debug_id, event);
 453
 454         object->oob_table = fscache_osm_lookup_oob;
 455
 456         ASSERT(parent != NULL);
 457         ASSERTCMP(parent->n_ops, >, 0);
 458         ASSERTCMP(parent->n_obj_ops, >, 0);
 459
 460         /* make sure the parent is still available */
 461         ASSERT(fscache_object_is_available(parent));
 462
 463         if (fscache_object_is_dying(parent) ||
 464             test_bit(FSCACHE_IOERROR, &object->cache->flags) ||
 465             !fscache_use_cookie(object)) {
 466                 _leave(" [unavailable]");
 467                 return transit_to(LOOKUP_FAILURE);
 468         }
 469
 470         _debug("LOOKUP \"%s\" in \"%s\"",
 471                cookie->def->name, object->cache->tag->name);
 472
 473         fscache_stat(&fscache_n_object_lookups);
 474         fscache_stat(&fscache_n_cop_lookup_object);
 475         ret = object->cache->ops->lookup_object(object);
 476         fscache_stat_d(&fscache_n_cop_lookup_object);
 477
 478         fscache_unuse_cookie(object);
 479
 480         if (ret == -ETIMEDOUT) {
 481                 /* probably stuck behind another object, so move this one to
 482                  * the back of the queue */
 483                 fscache_stat(&fscache_n_object_lookups_timed_out);
 484                 _leave(" [timeout]");
 485                 return NO_TRANSIT;
 486         }
 487
 488         if (ret < 0) {
 489                 _leave(" [error]");
 490                 return transit_to(LOOKUP_FAILURE);
 491         }
 492
 493         _leave(" [ok]");
 494         return transit_to(OBJECT_AVAILABLE);
 495 }
 496
 497 /**
 498  * fscache_object_lookup_negative - Note negative cookie lookup
 499  * @object: Object pointing to cookie to mark
 500  *
 501  * Note negative lookup, permitting those waiting to read data from an already
 502  * existing backing object to continue as there's no data for them to read.
 503  */
 504 void fscache_object_lookup_negative(struct fscache_object *object)
 505 {
 506         struct fscache_cookie *cookie = object->cookie;
 507
 508         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 509
 510         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 511                 fscache_stat(&fscache_n_object_lookups_negative);
 512
 513                 /* Allow write requests to begin stacking up and read requests to begin
 514                  * returning ENODATA.
 515                  */
 516                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 517                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 518
 519                 _debug("wake up lookup %p", &cookie->flags);
 520                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 521                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 522         }
 523         _leave("");
 524 }
 525 EXPORT_SYMBOL(fscache_object_lookup_negative);
 526
 527 /**
 528  * fscache_obtained_object - Note successful object lookup or creation
 529  * @object: Object pointing to cookie to mark
 530  *
 531  * Note successful lookup and/or creation, permitting those waiting to write
 532  * data to a backing object to continue.
 533  *
 534  * Note that after calling this, an object's cookie may be relinquished by the
 535  * netfs, and so must be accessed with object lock held.
 536  */
 537 void fscache_obtained_object(struct fscache_object *object)
 538 {
 539         struct fscache_cookie *cookie = object->cookie;
 540
 541         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 542
 543         /* if we were still looking up, then we must have a positive lookup
 544          * result, in which case there may be data available */
 545         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 546                 fscache_stat(&fscache_n_object_lookups_positive);
 547
 548                 /* We do (presumably) have data */
 549                 clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 550                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 551
 552                 /* Allow write requests to begin stacking up and read requests
 553                  * to begin shovelling data.
 554                  */
 555                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 556                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 557         } else {
 558                 fscache_stat(&fscache_n_object_created);
 559         }
 560
 561         set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
 562         _leave("");
 563 }
 564 EXPORT_SYMBOL(fscache_obtained_object);
 565
 566 /*
 567  * handle an object that has just become available
 568  */
 569 static const struct fscache_state *fscache_object_available(struct fscache_object *object,
 570                                                             int event)
 571 {
 572         _enter("{OBJ%x},%d", object->debug_id, event);
 573
 574         object->oob_table = fscache_osm_run_oob;
 575
 576         spin_lock(&object->lock);
 577
 578         fscache_done_parent_op(object);
 579         if (object->n_in_progress == 0) {
 580                 if (object->n_ops > 0) {
 581                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 582                         fscache_start_operations(object);
 583                 } else {
 584                         ASSERT(list_empty(&object->pending_ops));
 585                 }
 586         }
 587         spin_unlock(&object->lock);
 588
 589         fscache_stat(&fscache_n_cop_lookup_complete);
 590         object->cache->ops->lookup_complete(object);
 591         fscache_stat_d(&fscache_n_cop_lookup_complete);
 592
 593         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 594         fscache_stat(&fscache_n_object_avail);
 595
 596         _leave("");
 597         return transit_to(JUMPSTART_DEPS);
 598 }
 599
 600 /*
 601  * Wake up this object's dependent objects now that we've become available.
 602  */
 603 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
 604                                                                 int event)
 605 {
 606         _enter("{OBJ%x},%d", object->debug_id, event);
 607
 608         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
 609                 return NO_TRANSIT; /* Not finished; requeue */
 610         return transit_to(WAIT_FOR_CMD);
 611 }
 612
 613 /*
 614  * Handle lookup or creation failute.
 615  */
 616 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
 617                                                           int event)
 618 {
 619         struct fscache_cookie *cookie;
 620
 621         _enter("{OBJ%x},%d", object->debug_id, event);
 622
 623         object->oob_event_mask = 0;
 624
 625         fscache_stat(&fscache_n_cop_lookup_complete);
 626         object->cache->ops->lookup_complete(object);
 627         fscache_stat_d(&fscache_n_cop_lookup_complete);
 628
 629         set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags);
 630
 631         cookie = object->cookie;
 632         set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 633         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
 634                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 635
 636         fscache_done_parent_op(object);
 637         return transit_to(KILL_OBJECT);
 638 }
 639
 640 /*
 641  * Wait for completion of all active operations on this object and the death of
 642  * all child objects of this object.
 643  */
 644 static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
 645                                                        int event)
 646 {
 647         _enter("{OBJ%x,%d,%d},%d",
 648                object->debug_id, object->n_ops, object->n_children, event);
 649
 650         fscache_mark_object_dead(object);
 651         object->oob_event_mask = 0;
 652
 653         if (test_bit(FSCACHE_OBJECT_RETIRED, &object->flags)) {
 654                 /* Reject any new read/write ops and abort any that are pending. */
 655                 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 656                 fscache_cancel_all_ops(object);
 657         }
 658
 659         if (list_empty(&object->dependents) &&
 660             object->n_ops == 0 &&
 661             object->n_children == 0)
 662                 return transit_to(DROP_OBJECT);
 663
 664         if (object->n_in_progress == 0) {
 665                 spin_lock(&object->lock);
 666                 if (object->n_ops > 0 && object->n_in_progress == 0)
 667                         fscache_start_operations(object);
 668                 spin_unlock(&object->lock);
 669         }
 670
 671         if (!list_empty(&object->dependents))
 672                 return transit_to(KILL_DEPENDENTS);
 673
 674         return transit_to(WAIT_FOR_CLEARANCE);
 675 }
 676
 677 /*
 678  * Kill dependent objects.
 679  */
 680 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
 681                                                            int event)
 682 {
 683         _enter("{OBJ%x},%d", object->debug_id, event);
 684
 685         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
 686                 return NO_TRANSIT; /* Not finished */
 687         return transit_to(WAIT_FOR_CLEARANCE);
 688 }
 689
 690 /*
 691  * Drop an object's attachments
 692  */
 693 static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
 694                                                        int event)
 695 {
 696         struct fscache_object *parent = object->parent;
 697         struct fscache_cookie *cookie = object->cookie;
 698         struct fscache_cache *cache = object->cache;
 699         bool awaken = false;
 700
 701         _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
 702
 703         ASSERT(cookie != NULL);
 704         ASSERT(!hlist_unhashed(&object->cookie_link));
 705
 706         /* Make sure the cookie no longer points here and that the netfs isn't
 707          * waiting for us.
 708          */
 709         spin_lock(&cookie->lock);
 710         hlist_del_init(&object->cookie_link);
 711         if (hlist_empty(&cookie->backing_objects) &&
 712             test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 713                 awaken = true;
 714         spin_unlock(&cookie->lock);
 715
 716         if (awaken)
 717                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 718
 719         /* Prevent a race with our last child, which has to signal EV_CLEARED
 720          * before dropping our spinlock.
 721          */
 722         spin_lock(&object->lock);
 723         spin_unlock(&object->lock);
 724
 725         /* Discard from the cache's collection of objects */
 726         spin_lock(&cache->object_list_lock);
 727         list_del_init(&object->cache_link);
 728         spin_unlock(&cache->object_list_lock);
 729
 730         fscache_stat(&fscache_n_cop_drop_object);
 731         cache->ops->drop_object(object);
 732         fscache_stat_d(&fscache_n_cop_drop_object);
 733
 734         /* The parent object wants to know when all it dependents have gone */
 735         if (parent) {
 736                 _debug("release parent OBJ%x {%d}",
 737                        parent->debug_id, parent->n_children);
 738
 739                 spin_lock(&parent->lock);
 740                 parent->n_children--;
 741                 if (parent->n_children == 0)
 742                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 743                 spin_unlock(&parent->lock);
 744                 object->parent = NULL;
 745         }
 746
 747         /* this just shifts the object release to the work processor */
 748         fscache_put_object(object);
 749         fscache_stat(&fscache_n_object_dead);
 750
 751         _leave("");
 752         return transit_to(OBJECT_DEAD);
 753 }
 754
 755 /*
 756  * get a ref on an object
 757  */
 758 static int fscache_get_object(struct fscache_object *object)
 759 {
 760         int ret;
 761
 762         fscache_stat(&fscache_n_cop_grab_object);
 763         ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 764         fscache_stat_d(&fscache_n_cop_grab_object);
 765         return ret;
 766 }
 767
 768 /*
 769  * Discard a ref on an object
 770  */
 771 static void fscache_put_object(struct fscache_object *object)
 772 {
 773         fscache_stat(&fscache_n_cop_put_object);
 774         object->cache->ops->put_object(object);
 775         fscache_stat_d(&fscache_n_cop_put_object);
 776 }
 777
 778 /**
 779  * fscache_object_destroy - Note that a cache object is about to be destroyed
 780  * @object: The object to be destroyed
 781  *
 782  * Note the imminent destruction and deallocation of a cache object record.
 783  */
 784 void fscache_object_destroy(struct fscache_object *object)
 785 {
 786         fscache_objlist_remove(object);
 787
 788         /* We can get rid of the cookie now */
 789         fscache_cookie_put(object->cookie);
 790         object->cookie = NULL;
 791 }
 792 EXPORT_SYMBOL(fscache_object_destroy);
 793
 794 /*
 795  * enqueue an object for metadata-type processing
 796  */
 797 void fscache_enqueue_object(struct fscache_object *object)
 798 {
 799         _enter("{OBJ%x}", object->debug_id);
 800
 801         if (fscache_get_object(object) >= 0) {
 802                 wait_queue_head_t *cong_wq =
 803                         &get_cpu_var(fscache_object_cong_wait);
 804
 805                 if (queue_work(fscache_object_wq, &object->work)) {
 806                         if (fscache_object_congested())
 807                                 wake_up(cong_wq);
 808                 } else
 809                         fscache_put_object(object);
 810
 811                 put_cpu_var(fscache_object_cong_wait);
 812         }
 813 }
 814
 815 /**
 816  * fscache_object_sleep_till_congested - Sleep until object wq is congested
 817  * @timeoutp: Scheduler sleep timeout
 818  *
 819  * Allow an object handler to sleep until the object workqueue is congested.
 820  *
 821  * The caller must set up a wake up event before calling this and must have set
 822  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 823  * condition before calling this function as no test is made here.
 824  *
 825  * %true is returned if the object wq is congested, %false otherwise.
 826  */
 827 bool fscache_object_sleep_till_congested(signed long *timeoutp)
 828 {
 829         wait_queue_head_t *cong_wq = this_cpu_ptr(&fscache_object_cong_wait);
 830         DEFINE_WAIT(wait);
 831
 832         if (fscache_object_congested())
 833                 return true;
 834
 835         add_wait_queue_exclusive(cong_wq, &wait);
 836         if (!fscache_object_congested())
 837                 *timeoutp = schedule_timeout(*timeoutp);
 838         finish_wait(cong_wq, &wait);
 839
 840         return fscache_object_congested();
 841 }
 842 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 843
 844 /*
 845  * Enqueue the dependents of an object for metadata-type processing.
 846  *
 847  * If we don't manage to finish the list before the scheduler wants to run
 848  * again then return false immediately.  We return true if the list was
 849  * cleared.
 850  */
 851 static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
 852 {
 853         struct fscache_object *dep;
 854         bool ret = true;
 855
 856         _enter("{OBJ%x}", object->debug_id);
 857
 858         if (list_empty(&object->dependents))
 859                 return true;
 860
 861         spin_lock(&object->lock);
 862
 863         while (!list_empty(&object->dependents)) {
 864                 dep = list_entry(object->dependents.next,
 865                                  struct fscache_object, dep_link);
 866                 list_del_init(&dep->dep_link);
 867
 868                 fscache_raise_event(dep, event);
 869                 fscache_put_object(dep);
 870
 871                 if (!list_empty(&object->dependents) && need_resched()) {
 872                         ret = false;
 873                         break;
 874                 }
 875         }
 876
 877         spin_unlock(&object->lock);
 878         return ret;
 879 }
 880
 881 /*
 882  * remove an object from whatever queue it's waiting on
 883  */
 884 static void fscache_dequeue_object(struct fscache_object *object)
 885 {
 886         _enter("{OBJ%x}", object->debug_id);
 887
 888         if (!list_empty(&object->dep_link)) {
 889                 spin_lock(&object->parent->lock);
 890                 list_del_init(&object->dep_link);
 891                 spin_unlock(&object->parent->lock);
 892         }
 893
 894         _leave("");
 895 }
 896
 897 /**
 898  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 899  * @object: The object to ask about
 900  * @data: The auxiliary data for the object
 901  * @datalen: The size of the auxiliary data
 902  *
 903  * This function consults the netfs about the coherency state of an object.
 904  * The caller must be holding a ref on cookie->n_active (held by
 905  * fscache_look_up_object() on behalf of the cache backend during object lookup
 906  * and creation).
 907  */
 908 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 909                                         const void *data, uint16_t datalen)
 910 {
 911         enum fscache_checkaux result;
 912
 913         if (!object->cookie->def->check_aux) {
 914                 fscache_stat(&fscache_n_checkaux_none);
 915                 return FSCACHE_CHECKAUX_OKAY;
 916         }
 917
 918         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 919                                                 data, datalen);
 920         switch (result) {
 921                 /* entry okay as is */
 922         case FSCACHE_CHECKAUX_OKAY:
 923                 fscache_stat(&fscache_n_checkaux_okay);
 924                 break;
 925
 926                 /* entry requires update */
 927         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 928                 fscache_stat(&fscache_n_checkaux_update);
 929                 break;
 930
 931                 /* entry requires deletion */
 932         case FSCACHE_CHECKAUX_OBSOLETE:
 933                 fscache_stat(&fscache_n_checkaux_obsolete);
 934                 break;
 935
 936         default:
 937                 BUG();
 938         }
 939
 940         return result;
 941 }
 942 EXPORT_SYMBOL(fscache_check_aux);
 943
 944 /*
 945  * Asynchronously invalidate an object.
 946  */
 947 static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
 948                                                               int event)
 949 {
 950         struct fscache_operation *op;
 951         struct fscache_cookie *cookie = object->cookie;
 952
 953         _enter("{OBJ%x},%d", object->debug_id, event);
 954
 955         /* We're going to need the cookie.  If the cookie is not available then
 956          * retire the object instead.
 957          */
 958         if (!fscache_use_cookie(object)) {
 959                 ASSERT(object->cookie->stores.rnode == NULL);
 960                 set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
 961                 _leave(" [no cookie]");
 962                 return transit_to(KILL_OBJECT);
 963         }
 964
 965         /* Reject any new read/write ops and abort any that are pending. */
 966         fscache_invalidate_writes(cookie);
 967         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 968         fscache_cancel_all_ops(object);
 969
 970         /* Now we have to wait for in-progress reads and writes */
 971         op = kzalloc(sizeof(*op), GFP_KERNEL);
 972         if (!op)
 973                 goto nomem;
 974
 975         fscache_operation_init(op, object->cache->ops->invalidate_object,
 976                                NULL, NULL);
 977         op->flags = FSCACHE_OP_ASYNC |
 978                 (1 << FSCACHE_OP_EXCLUSIVE) |
 979                 (1 << FSCACHE_OP_UNUSE_COOKIE);
 980
 981         spin_lock(&cookie->lock);
 982         if (fscache_submit_exclusive_op(object, op) < 0)
 983                 goto submit_op_failed;
 984         spin_unlock(&cookie->lock);
 985         fscache_put_operation(op);
 986
 987         /* Once we've completed the invalidation, we know there will be no data
 988          * stored in the cache and thus we can reinstate the data-check-skip
 989          * optimisation.
 990          */
 991         set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 992
 993         /* We can allow read and write requests to come in once again.  They'll
 994          * queue up behind our exclusive invalidation operation.
 995          */
 996         if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 997                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 998         _leave(" [ok]");
 999         return transit_to(UPDATE_OBJECT);
1000
1001 nomem:
1002         fscache_mark_object_dead(object);
1003         fscache_unuse_cookie(object);
1004         _leave(" [ENOMEM]");
1005         return transit_to(KILL_OBJECT);
1006
1007 submit_op_failed:
1008         fscache_mark_object_dead(object);
1009         spin_unlock(&cookie->lock);
1010         fscache_unuse_cookie(object);
1011         kfree(op);
1012         _leave(" [EIO]");
1013         return transit_to(KILL_OBJECT);
1014 }
1015
1016 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
1017                                                              int event)
1018 {
1019         const struct fscache_state *s;
1020
1021         fscache_stat(&fscache_n_invalidates_run);
1022         fscache_stat(&fscache_n_cop_invalidate_object);
1023         s = _fscache_invalidate_object(object, event);
1024         fscache_stat_d(&fscache_n_cop_invalidate_object);
1025         return s;
1026 }
1027
1028 /*
1029  * Asynchronously update an object.
1030  */
1031 static const struct fscache_state *fscache_update_object(struct fscache_object *object,
1032                                                          int event)
1033 {
1034         _enter("{OBJ%x},%d", object->debug_id, event);
1035
1036         fscache_stat(&fscache_n_updates_run);
1037         fscache_stat(&fscache_n_cop_update_object);
1038         object->cache->ops->update_object(object);
1039         fscache_stat_d(&fscache_n_cop_update_object);
1040
1041         _leave("");
1042         return transit_to(WAIT_FOR_CMD);
1043 }
1044
1045 /**
1046  * fscache_object_retrying_stale - Note retrying stale object
1047  * @object: The object that will be retried
1048  *
1049  * Note that an object lookup found an on-disk object that was adjudged to be
1050  * stale and has been deleted.  The lookup will be retried.
1051  */
1052 void fscache_object_retrying_stale(struct fscache_object *object)
1053 {
1054         fscache_stat(&fscache_n_cache_no_space_reject);
1055 }
1056 EXPORT_SYMBOL(fscache_object_retrying_stale);
1057
1058 /**
1059  * fscache_object_mark_killed - Note that an object was killed
1060  * @object: The object that was culled
1061  * @why: The reason the object was killed.
1062  *
1063  * Note that an object was killed.  Returns true if the object was
1064  * already marked killed, false if it wasn't.
1065  */
1066 void fscache_object_mark_killed(struct fscache_object *object,
1067                                 enum fscache_why_object_killed why)
1068 {
1069         if (test_and_set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags)) {
1070                 pr_err("Error: Object already killed by cache [%s]\n",
1071                        object->cache->identifier);
1072                 return;
1073         }
1074
1075         switch (why) {
1076         case FSCACHE_OBJECT_NO_SPACE:
1077                 fscache_stat(&fscache_n_cache_no_space_reject);
1078                 break;
1079         case FSCACHE_OBJECT_IS_STALE:
1080                 fscache_stat(&fscache_n_cache_stale_objects);
1081                 break;
1082         case FSCACHE_OBJECT_WAS_RETIRED:
1083                 fscache_stat(&fscache_n_cache_retired_objects);
1084                 break;
1085         case FSCACHE_OBJECT_WAS_CULLED:
1086                 fscache_stat(&fscache_n_cache_culled_objects);
1087                 break;
1088         }
1089 }
1090 EXPORT_SYMBOL(fscache_object_mark_killed);
1091
1092 /*
1093  * The object is dead.  We can get here if an object gets queued by an event
1094  * that would lead to its death (such as EV_KILL) when the dispatcher is
1095  * already running (and so can be requeued) but hasn't yet cleared the event
1096  * mask.
1097  */
1098 static const struct fscache_state *fscache_object_dead(struct fscache_object *object,
1099                                                        int event)
1100 {
1101         if (!test_and_set_bit(FSCACHE_OBJECT_RUN_AFTER_DEAD,
1102                               &object->flags))
1103                 return NO_TRANSIT;
1104
1105         WARN(true, "FS-Cache object redispatched after death");
1106         return NO_TRANSIT;
1107 }