kernel/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  * Mark the object as no longer being live, making sure that we synchronise
 332  * against op submission.
 333  */
 334 static inline void fscache_mark_object_dead(struct fscache_object *object)
 335 {
 336         spin_lock(&object->lock);
 337         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 338         spin_unlock(&object->lock);
 339 }
 340
 341 /*
 342  * Abort object initialisation before we start it.
 343  */
 344 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
 345                                                                 int event)
 346 {
 347         _enter("{OBJ%x},%d", object->debug_id, event);
 348
 349         object->oob_event_mask = 0;
 350         fscache_dequeue_object(object);
 351         return transit_to(KILL_OBJECT);
 352 }
 353
 354 /*
 355  * initialise an object
 356  * - check the specified object's parent to see if we can make use of it
 357  *   immediately to do a creation
 358  * - we may need to start the process of creating a parent and we need to wait
 359  *   for the parent's lookup and creation to complete if it's not there yet
 360  */
 361 static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
 362                                                              int event)
 363 {
 364         struct fscache_object *parent;
 365         bool success;
 366
 367         _enter("{OBJ%x},%d", object->debug_id, event);
 368
 369         ASSERT(list_empty(&object->dep_link));
 370
 371         parent = object->parent;
 372         if (!parent) {
 373                 _leave(" [no parent]");
 374                 return transit_to(DROP_OBJECT);
 375         }
 376
 377         _debug("parent: %s of:%lx", parent->state->name, parent->flags);
 378
 379         if (fscache_object_is_dying(parent)) {
 380                 _leave(" [bad parent]");
 381                 return transit_to(DROP_OBJECT);
 382         }
 383
 384         if (fscache_object_is_available(parent)) {
 385                 _leave(" [ready]");
 386                 return transit_to(PARENT_READY);
 387         }
 388
 389         _debug("wait");
 390
 391         spin_lock(&parent->lock);
 392         fscache_stat(&fscache_n_cop_grab_object);
 393         success = false;
 394         if (fscache_object_is_live(parent) &&
 395             object->cache->ops->grab_object(object)) {
 396                 list_add(&object->dep_link, &parent->dependents);
 397                 success = true;
 398         }
 399         fscache_stat_d(&fscache_n_cop_grab_object);
 400         spin_unlock(&parent->lock);
 401         if (!success) {
 402                 _leave(" [grab failed]");
 403                 return transit_to(DROP_OBJECT);
 404         }
 405
 406         /* fscache_acquire_non_index_cookie() uses this
 407          * to wake the chain up */
 408         fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
 409         _leave(" [wait]");
 410         return transit_to(WAIT_FOR_PARENT);
 411 }
 412
 413 /*
 414  * Once the parent object is ready, we should kick off our lookup op.
 415  */
 416 static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
 417                                                         int event)
 418 {
 419         struct fscache_object *parent = object->parent;
 420
 421         _enter("{OBJ%x},%d", object->debug_id, event);
 422
 423         ASSERT(parent != NULL);
 424
 425         spin_lock(&parent->lock);
 426         parent->n_ops++;
 427         parent->n_obj_ops++;
 428         object->lookup_jif = jiffies;
 429         spin_unlock(&parent->lock);
 430
 431         _leave("");
 432         return transit_to(LOOK_UP_OBJECT);
 433 }
 434
 435 /*
 436  * look an object up in the cache from which it was allocated
 437  * - we hold an "access lock" on the parent object, so the parent object cannot
 438  *   be withdrawn by either party till we've finished
 439  */
 440 static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
 441                                                           int event)
 442 {
 443         struct fscache_cookie *cookie = object->cookie;
 444         struct fscache_object *parent = object->parent;
 445         int ret;
 446
 447         _enter("{OBJ%x},%d", object->debug_id, event);
 448
 449         object->oob_table = fscache_osm_lookup_oob;
 450
 451         ASSERT(parent != NULL);
 452         ASSERTCMP(parent->n_ops, >, 0);
 453         ASSERTCMP(parent->n_obj_ops, >, 0);
 454
 455         /* make sure the parent is still available */
 456         ASSERT(fscache_object_is_available(parent));
 457
 458         if (fscache_object_is_dying(parent) ||
 459             test_bit(FSCACHE_IOERROR, &object->cache->flags) ||
 460             !fscache_use_cookie(object)) {
 461                 _leave(" [unavailable]");
 462                 return transit_to(LOOKUP_FAILURE);
 463         }
 464
 465         _debug("LOOKUP \"%s\" in \"%s\"",
 466                cookie->def->name, object->cache->tag->name);
 467
 468         fscache_stat(&fscache_n_object_lookups);
 469         fscache_stat(&fscache_n_cop_lookup_object);
 470         ret = object->cache->ops->lookup_object(object);
 471         fscache_stat_d(&fscache_n_cop_lookup_object);
 472
 473         fscache_unuse_cookie(object);
 474
 475         if (ret == -ETIMEDOUT) {
 476                 /* probably stuck behind another object, so move this one to
 477                  * the back of the queue */
 478                 fscache_stat(&fscache_n_object_lookups_timed_out);
 479                 _leave(" [timeout]");
 480                 return NO_TRANSIT;
 481         }
 482
 483         if (ret < 0) {
 484                 _leave(" [error]");
 485                 return transit_to(LOOKUP_FAILURE);
 486         }
 487
 488         _leave(" [ok]");
 489         return transit_to(OBJECT_AVAILABLE);
 490 }
 491
 492 /**
 493  * fscache_object_lookup_negative - Note negative cookie lookup
 494  * @object: Object pointing to cookie to mark
 495  *
 496  * Note negative lookup, permitting those waiting to read data from an already
 497  * existing backing object to continue as there's no data for them to read.
 498  */
 499 void fscache_object_lookup_negative(struct fscache_object *object)
 500 {
 501         struct fscache_cookie *cookie = object->cookie;
 502
 503         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 504
 505         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 506                 fscache_stat(&fscache_n_object_lookups_negative);
 507
 508                 /* Allow write requests to begin stacking up and read requests to begin
 509                  * returning ENODATA.
 510                  */
 511                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 512                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 513
 514                 _debug("wake up lookup %p", &cookie->flags);
 515                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 516                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 517         }
 518         _leave("");
 519 }
 520 EXPORT_SYMBOL(fscache_object_lookup_negative);
 521
 522 /**
 523  * fscache_obtained_object - Note successful object lookup or creation
 524  * @object: Object pointing to cookie to mark
 525  *
 526  * Note successful lookup and/or creation, permitting those waiting to write
 527  * data to a backing object to continue.
 528  *
 529  * Note that after calling this, an object's cookie may be relinquished by the
 530  * netfs, and so must be accessed with object lock held.
 531  */
 532 void fscache_obtained_object(struct fscache_object *object)
 533 {
 534         struct fscache_cookie *cookie = object->cookie;
 535
 536         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 537
 538         /* if we were still looking up, then we must have a positive lookup
 539          * result, in which case there may be data available */
 540         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 541                 fscache_stat(&fscache_n_object_lookups_positive);
 542
 543                 /* We do (presumably) have data */
 544                 clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 545                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 546
 547                 /* Allow write requests to begin stacking up and read requests
 548                  * to begin shovelling data.
 549                  */
 550                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 551                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 552         } else {
 553                 fscache_stat(&fscache_n_object_created);
 554         }
 555
 556         set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
 557         _leave("");
 558 }
 559 EXPORT_SYMBOL(fscache_obtained_object);
 560
 561 /*
 562  * handle an object that has just become available
 563  */
 564 static const struct fscache_state *fscache_object_available(struct fscache_object *object,
 565                                                             int event)
 566 {
 567         _enter("{OBJ%x},%d", object->debug_id, event);
 568
 569         object->oob_table = fscache_osm_run_oob;
 570
 571         spin_lock(&object->lock);
 572
 573         fscache_done_parent_op(object);
 574         if (object->n_in_progress == 0) {
 575                 if (object->n_ops > 0) {
 576                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 577                         fscache_start_operations(object);
 578                 } else {
 579                         ASSERT(list_empty(&object->pending_ops));
 580                 }
 581         }
 582         spin_unlock(&object->lock);
 583
 584         fscache_stat(&fscache_n_cop_lookup_complete);
 585         object->cache->ops->lookup_complete(object);
 586         fscache_stat_d(&fscache_n_cop_lookup_complete);
 587
 588         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 589         fscache_stat(&fscache_n_object_avail);
 590
 591         _leave("");
 592         return transit_to(JUMPSTART_DEPS);
 593 }
 594
 595 /*
 596  * Wake up this object's dependent objects now that we've become available.
 597  */
 598 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
 599                                                                 int event)
 600 {
 601         _enter("{OBJ%x},%d", object->debug_id, event);
 602
 603         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
 604                 return NO_TRANSIT; /* Not finished; requeue */
 605         return transit_to(WAIT_FOR_CMD);
 606 }
 607
 608 /*
 609  * Handle lookup or creation failute.
 610  */
 611 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
 612                                                           int event)
 613 {
 614         struct fscache_cookie *cookie;
 615
 616         _enter("{OBJ%x},%d", object->debug_id, event);
 617
 618         object->oob_event_mask = 0;
 619
 620         fscache_stat(&fscache_n_cop_lookup_complete);
 621         object->cache->ops->lookup_complete(object);
 622         fscache_stat_d(&fscache_n_cop_lookup_complete);
 623
 624         set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags);
 625
 626         cookie = object->cookie;
 627         set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 628         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
 629                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 630
 631         fscache_done_parent_op(object);
 632         return transit_to(KILL_OBJECT);
 633 }
 634
 635 /*
 636  * Wait for completion of all active operations on this object and the death of
 637  * all child objects of this object.
 638  */
 639 static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
 640                                                        int event)
 641 {
 642         _enter("{OBJ%x,%d,%d},%d",
 643                object->debug_id, object->n_ops, object->n_children, event);
 644
 645         fscache_mark_object_dead(object);
 646         object->oob_event_mask = 0;
 647
 648         if (list_empty(&object->dependents) &&
 649             object->n_ops == 0 &&
 650             object->n_children == 0)
 651                 return transit_to(DROP_OBJECT);
 652
 653         if (object->n_in_progress == 0) {
 654                 spin_lock(&object->lock);
 655                 if (object->n_ops > 0 && object->n_in_progress == 0)
 656                         fscache_start_operations(object);
 657                 spin_unlock(&object->lock);
 658         }
 659
 660         if (!list_empty(&object->dependents))
 661                 return transit_to(KILL_DEPENDENTS);
 662
 663         return transit_to(WAIT_FOR_CLEARANCE);
 664 }
 665
 666 /*
 667  * Kill dependent objects.
 668  */
 669 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
 670                                                            int event)
 671 {
 672         _enter("{OBJ%x},%d", object->debug_id, event);
 673
 674         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
 675                 return NO_TRANSIT; /* Not finished */
 676         return transit_to(WAIT_FOR_CLEARANCE);
 677 }
 678
 679 /*
 680  * Drop an object's attachments
 681  */
 682 static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
 683                                                        int event)
 684 {
 685         struct fscache_object *parent = object->parent;
 686         struct fscache_cookie *cookie = object->cookie;
 687         struct fscache_cache *cache = object->cache;
 688         bool awaken = false;
 689
 690         _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
 691
 692         ASSERT(cookie != NULL);
 693         ASSERT(!hlist_unhashed(&object->cookie_link));
 694
 695         /* Make sure the cookie no longer points here and that the netfs isn't
 696          * waiting for us.
 697          */
 698         spin_lock(&cookie->lock);
 699         hlist_del_init(&object->cookie_link);
 700         if (hlist_empty(&cookie->backing_objects) &&
 701             test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 702                 awaken = true;
 703         spin_unlock(&cookie->lock);
 704
 705         if (awaken)
 706                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 707
 708         /* Prevent a race with our last child, which has to signal EV_CLEARED
 709          * before dropping our spinlock.
 710          */
 711         spin_lock(&object->lock);
 712         spin_unlock(&object->lock);
 713
 714         /* Discard from the cache's collection of objects */
 715         spin_lock(&cache->object_list_lock);
 716         list_del_init(&object->cache_link);
 717         spin_unlock(&cache->object_list_lock);
 718
 719         fscache_stat(&fscache_n_cop_drop_object);
 720         cache->ops->drop_object(object);
 721         fscache_stat_d(&fscache_n_cop_drop_object);
 722
 723         /* The parent object wants to know when all it dependents have gone */
 724         if (parent) {
 725                 _debug("release parent OBJ%x {%d}",
 726                        parent->debug_id, parent->n_children);
 727
 728                 spin_lock(&parent->lock);
 729                 parent->n_children--;
 730                 if (parent->n_children == 0)
 731                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 732                 spin_unlock(&parent->lock);
 733                 object->parent = NULL;
 734         }
 735
 736         /* this just shifts the object release to the work processor */
 737         fscache_put_object(object);
 738         fscache_stat(&fscache_n_object_dead);
 739
 740         _leave("");
 741         return transit_to(OBJECT_DEAD);
 742 }
 743
 744 /*
 745  * get a ref on an object
 746  */
 747 static int fscache_get_object(struct fscache_object *object)
 748 {
 749         int ret;
 750
 751         fscache_stat(&fscache_n_cop_grab_object);
 752         ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 753         fscache_stat_d(&fscache_n_cop_grab_object);
 754         return ret;
 755 }
 756
 757 /*
 758  * Discard a ref on an object
 759  */
 760 static void fscache_put_object(struct fscache_object *object)
 761 {
 762         fscache_stat(&fscache_n_cop_put_object);
 763         object->cache->ops->put_object(object);
 764         fscache_stat_d(&fscache_n_cop_put_object);
 765 }
 766
 767 /**
 768  * fscache_object_destroy - Note that a cache object is about to be destroyed
 769  * @object: The object to be destroyed
 770  *
 771  * Note the imminent destruction and deallocation of a cache object record.
 772  */
 773 void fscache_object_destroy(struct fscache_object *object)
 774 {
 775         fscache_objlist_remove(object);
 776
 777         /* We can get rid of the cookie now */
 778         fscache_cookie_put(object->cookie);
 779         object->cookie = NULL;
 780 }
 781 EXPORT_SYMBOL(fscache_object_destroy);
 782
 783 /*
 784  * enqueue an object for metadata-type processing
 785  */
 786 void fscache_enqueue_object(struct fscache_object *object)
 787 {
 788         _enter("{OBJ%x}", object->debug_id);
 789
 790         if (fscache_get_object(object) >= 0) {
 791                 wait_queue_head_t *cong_wq =
 792                         &get_cpu_var(fscache_object_cong_wait);
 793
 794                 if (queue_work(fscache_object_wq, &object->work)) {
 795                         if (fscache_object_congested())
 796                                 wake_up(cong_wq);
 797                 } else
 798                         fscache_put_object(object);
 799
 800                 put_cpu_var(fscache_object_cong_wait);
 801         }
 802 }
 803
 804 /**
 805  * fscache_object_sleep_till_congested - Sleep until object wq is congested
 806  * @timeoutp: Scheduler sleep timeout
 807  *
 808  * Allow an object handler to sleep until the object workqueue is congested.
 809  *
 810  * The caller must set up a wake up event before calling this and must have set
 811  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 812  * condition before calling this function as no test is made here.
 813  *
 814  * %true is returned if the object wq is congested, %false otherwise.
 815  */
 816 bool fscache_object_sleep_till_congested(signed long *timeoutp)
 817 {
 818         wait_queue_head_t *cong_wq = this_cpu_ptr(&fscache_object_cong_wait);
 819         DEFINE_WAIT(wait);
 820
 821         if (fscache_object_congested())
 822                 return true;
 823
 824         add_wait_queue_exclusive(cong_wq, &wait);
 825         if (!fscache_object_congested())
 826                 *timeoutp = schedule_timeout(*timeoutp);
 827         finish_wait(cong_wq, &wait);
 828
 829         return fscache_object_congested();
 830 }
 831 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 832
 833 /*
 834  * Enqueue the dependents of an object for metadata-type processing.
 835  *
 836  * If we don't manage to finish the list before the scheduler wants to run
 837  * again then return false immediately.  We return true if the list was
 838  * cleared.
 839  */
 840 static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
 841 {
 842         struct fscache_object *dep;
 843         bool ret = true;
 844
 845         _enter("{OBJ%x}", object->debug_id);
 846
 847         if (list_empty(&object->dependents))
 848                 return true;
 849
 850         spin_lock(&object->lock);
 851
 852         while (!list_empty(&object->dependents)) {
 853                 dep = list_entry(object->dependents.next,
 854                                  struct fscache_object, dep_link);
 855                 list_del_init(&dep->dep_link);
 856
 857                 fscache_raise_event(dep, event);
 858                 fscache_put_object(dep);
 859
 860                 if (!list_empty(&object->dependents) && need_resched()) {
 861                         ret = false;
 862                         break;
 863                 }
 864         }
 865
 866         spin_unlock(&object->lock);
 867         return ret;
 868 }
 869
 870 /*
 871  * remove an object from whatever queue it's waiting on
 872  */
 873 static void fscache_dequeue_object(struct fscache_object *object)
 874 {
 875         _enter("{OBJ%x}", object->debug_id);
 876
 877         if (!list_empty(&object->dep_link)) {
 878                 spin_lock(&object->parent->lock);
 879                 list_del_init(&object->dep_link);
 880                 spin_unlock(&object->parent->lock);
 881         }
 882
 883         _leave("");
 884 }
 885
 886 /**
 887  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 888  * @object: The object to ask about
 889  * @data: The auxiliary data for the object
 890  * @datalen: The size of the auxiliary data
 891  *
 892  * This function consults the netfs about the coherency state of an object.
 893  * The caller must be holding a ref on cookie->n_active (held by
 894  * fscache_look_up_object() on behalf of the cache backend during object lookup
 895  * and creation).
 896  */
 897 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 898                                         const void *data, uint16_t datalen)
 899 {
 900         enum fscache_checkaux result;
 901
 902         if (!object->cookie->def->check_aux) {
 903                 fscache_stat(&fscache_n_checkaux_none);
 904                 return FSCACHE_CHECKAUX_OKAY;
 905         }
 906
 907         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 908                                                 data, datalen);
 909         switch (result) {
 910                 /* entry okay as is */
 911         case FSCACHE_CHECKAUX_OKAY:
 912                 fscache_stat(&fscache_n_checkaux_okay);
 913                 break;
 914
 915                 /* entry requires update */
 916         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 917                 fscache_stat(&fscache_n_checkaux_update);
 918                 break;
 919
 920                 /* entry requires deletion */
 921         case FSCACHE_CHECKAUX_OBSOLETE:
 922                 fscache_stat(&fscache_n_checkaux_obsolete);
 923                 break;
 924
 925         default:
 926                 BUG();
 927         }
 928
 929         return result;
 930 }
 931 EXPORT_SYMBOL(fscache_check_aux);
 932
 933 /*
 934  * Asynchronously invalidate an object.
 935  */
 936 static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
 937                                                               int event)
 938 {
 939         struct fscache_operation *op;
 940         struct fscache_cookie *cookie = object->cookie;
 941
 942         _enter("{OBJ%x},%d", object->debug_id, event);
 943
 944         /* We're going to need the cookie.  If the cookie is not available then
 945          * retire the object instead.
 946          */
 947         if (!fscache_use_cookie(object)) {
 948                 ASSERT(object->cookie->stores.rnode == NULL);
 949                 set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
 950                 _leave(" [no cookie]");
 951                 return transit_to(KILL_OBJECT);
 952         }
 953
 954         /* Reject any new read/write ops and abort any that are pending. */
 955         fscache_invalidate_writes(cookie);
 956         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 957         fscache_cancel_all_ops(object);
 958
 959         /* Now we have to wait for in-progress reads and writes */
 960         op = kzalloc(sizeof(*op), GFP_KERNEL);
 961         if (!op)
 962                 goto nomem;
 963
 964         fscache_operation_init(op, object->cache->ops->invalidate_object,
 965                                NULL, NULL);
 966         op->flags = FSCACHE_OP_ASYNC |
 967                 (1 << FSCACHE_OP_EXCLUSIVE) |
 968                 (1 << FSCACHE_OP_UNUSE_COOKIE);
 969
 970         spin_lock(&cookie->lock);
 971         if (fscache_submit_exclusive_op(object, op) < 0)
 972                 goto submit_op_failed;
 973         spin_unlock(&cookie->lock);
 974         fscache_put_operation(op);
 975
 976         /* Once we've completed the invalidation, we know there will be no data
 977          * stored in the cache and thus we can reinstate the data-check-skip
 978          * optimisation.
 979          */
 980         set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 981
 982         /* We can allow read and write requests to come in once again.  They'll
 983          * queue up behind our exclusive invalidation operation.
 984          */
 985         if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 986                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 987         _leave(" [ok]");
 988         return transit_to(UPDATE_OBJECT);
 989
 990 nomem:
 991         fscache_mark_object_dead(object);
 992         fscache_unuse_cookie(object);
 993         _leave(" [ENOMEM]");
 994         return transit_to(KILL_OBJECT);
 995
 996 submit_op_failed:
 997         fscache_mark_object_dead(object);
 998         spin_unlock(&cookie->lock);
 999         fscache_unuse_cookie(object);
1000         kfree(op);
1001         _leave(" [EIO]");
1002         return transit_to(KILL_OBJECT);
1003 }
1004
1005 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
1006                                                              int event)
1007 {
1008         const struct fscache_state *s;
1009
1010         fscache_stat(&fscache_n_invalidates_run);
1011         fscache_stat(&fscache_n_cop_invalidate_object);
1012         s = _fscache_invalidate_object(object, event);
1013         fscache_stat_d(&fscache_n_cop_invalidate_object);
1014         return s;
1015 }
1016
1017 /*
1018  * Asynchronously update an object.
1019  */
1020 static const struct fscache_state *fscache_update_object(struct fscache_object *object,
1021                                                          int event)
1022 {
1023         _enter("{OBJ%x},%d", object->debug_id, event);
1024
1025         fscache_stat(&fscache_n_updates_run);
1026         fscache_stat(&fscache_n_cop_update_object);
1027         object->cache->ops->update_object(object);
1028         fscache_stat_d(&fscache_n_cop_update_object);
1029
1030         _leave("");
1031         return transit_to(WAIT_FOR_CMD);
1032 }
1033
1034 /**
1035  * fscache_object_retrying_stale - Note retrying stale object
1036  * @object: The object that will be retried
1037  *
1038  * Note that an object lookup found an on-disk object that was adjudged to be
1039  * stale and has been deleted.  The lookup will be retried.
1040  */
1041 void fscache_object_retrying_stale(struct fscache_object *object)
1042 {
1043         fscache_stat(&fscache_n_cache_no_space_reject);
1044 }
1045 EXPORT_SYMBOL(fscache_object_retrying_stale);
1046
1047 /**
1048  * fscache_object_mark_killed - Note that an object was killed
1049  * @object: The object that was culled
1050  * @why: The reason the object was killed.
1051  *
1052  * Note that an object was killed.  Returns true if the object was
1053  * already marked killed, false if it wasn't.
1054  */
1055 void fscache_object_mark_killed(struct fscache_object *object,
1056                                 enum fscache_why_object_killed why)
1057 {
1058         if (test_and_set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags)) {
1059                 pr_err("Error: Object already killed by cache [%s]\n",
1060                        object->cache->identifier);
1061                 return;
1062         }
1063
1064         switch (why) {
1065         case FSCACHE_OBJECT_NO_SPACE:
1066                 fscache_stat(&fscache_n_cache_no_space_reject);
1067                 break;
1068         case FSCACHE_OBJECT_IS_STALE:
1069                 fscache_stat(&fscache_n_cache_stale_objects);
1070                 break;
1071         case FSCACHE_OBJECT_WAS_RETIRED:
1072                 fscache_stat(&fscache_n_cache_retired_objects);
1073                 break;
1074         case FSCACHE_OBJECT_WAS_CULLED:
1075                 fscache_stat(&fscache_n_cache_culled_objects);
1076                 break;
1077         }
1078 }
1079 EXPORT_SYMBOL(fscache_object_mark_killed);