fs/fscache/object.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* FS-Cache object state machine handler
   3  *
   4  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  *
   7  * See Documentation/filesystems/caching/object.rst for a description of the
   8  * object state machine and the in-kernel representations.
   9  */
  10
  11 #define FSCACHE_DEBUG_LEVEL COOKIE
  12 #include <linux/module.h>
  13 #include <linux/slab.h>
  14 #include <linux/prefetch.h>
  15 #include "internal.h"
  16
  17 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *, int);
  18 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *, int);
  19 static const struct fscache_state *fscache_drop_object(struct fscache_object *, int);
  20 static const struct fscache_state *fscache_initialise_object(struct fscache_object *, int);
  21 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *, int);
  22 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *, int);
  23 static const struct fscache_state *fscache_kill_object(struct fscache_object *, int);
  24 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *, int);
  25 static const struct fscache_state *fscache_look_up_object(struct fscache_object *, int);
  26 static const struct fscache_state *fscache_object_available(struct fscache_object *, int);
  27 static const struct fscache_state *fscache_parent_ready(struct fscache_object *, int);
  28 static const struct fscache_state *fscache_update_object(struct fscache_object *, int);
  29 static const struct fscache_state *fscache_object_dead(struct fscache_object *, int);
  30
  31 #define __STATE_NAME(n) fscache_osm_##n
  32 #define STATE(n) (&__STATE_NAME(n))
  33
  34 /*
  35  * Define a work state.  Work states are execution states.  No event processing
  36  * is performed by them.  The function attached to a work state returns a
  37  * pointer indicating the next state to which the state machine should
  38  * transition.  Returning NO_TRANSIT repeats the current state, but goes back
  39  * to the scheduler first.
  40  */
  41 #define WORK_STATE(n, sn, f) \
  42         const struct fscache_state __STATE_NAME(n) = {                  \
  43                 .name = #n,                                             \
  44                 .short_name = sn,                                       \
  45                 .work = f                                               \
  46         }
  47
  48 /*
  49  * Returns from work states.
  50  */
  51 #define transit_to(state) ({ prefetch(&STATE(state)->work); STATE(state); })
  52
  53 #define NO_TRANSIT ((struct fscache_state *)NULL)
  54
  55 /*
  56  * Define a wait state.  Wait states are event processing states.  No execution
  57  * is performed by them.  Wait states are just tables of "if event X occurs,
  58  * clear it and transition to state Y".  The dispatcher returns to the
  59  * scheduler if none of the events in which the wait state has an interest are
  60  * currently pending.
  61  */
  62 #define WAIT_STATE(n, sn, ...) \
  63         const struct fscache_state __STATE_NAME(n) = {                  \
  64                 .name = #n,                                             \
  65                 .short_name = sn,                                       \
  66                 .work = NULL,                                           \
  67                 .transitions = { __VA_ARGS__, { 0, NULL } }             \
  68         }
  69
  70 #define TRANSIT_TO(state, emask) \
  71         { .events = (emask), .transit_to = STATE(state) }
  72
  73 /*
  74  * The object state machine.
  75  */
  76 static WORK_STATE(INIT_OBJECT,          "INIT", fscache_initialise_object);
  77 static WORK_STATE(PARENT_READY,         "PRDY", fscache_parent_ready);
  78 static WORK_STATE(ABORT_INIT,           "ABRT", fscache_abort_initialisation);
  79 static WORK_STATE(LOOK_UP_OBJECT,       "LOOK", fscache_look_up_object);
  80 static WORK_STATE(CREATE_OBJECT,        "CRTO", fscache_look_up_object);
  81 static WORK_STATE(OBJECT_AVAILABLE,     "AVBL", fscache_object_available);
  82 static WORK_STATE(JUMPSTART_DEPS,       "JUMP", fscache_jumpstart_dependents);
  83
  84 static WORK_STATE(INVALIDATE_OBJECT,    "INVL", fscache_invalidate_object);
  85 static WORK_STATE(UPDATE_OBJECT,        "UPDT", fscache_update_object);
  86
  87 static WORK_STATE(LOOKUP_FAILURE,       "LCFL", fscache_lookup_failure);
  88 static WORK_STATE(KILL_OBJECT,          "KILL", fscache_kill_object);
  89 static WORK_STATE(KILL_DEPENDENTS,      "KDEP", fscache_kill_dependents);
  90 static WORK_STATE(DROP_OBJECT,          "DROP", fscache_drop_object);
  91 static WORK_STATE(OBJECT_DEAD,          "DEAD", fscache_object_dead);
  92
  93 static WAIT_STATE(WAIT_FOR_INIT,        "?INI",
  94                   TRANSIT_TO(INIT_OBJECT,       1 << FSCACHE_OBJECT_EV_NEW_CHILD));
  95
  96 static WAIT_STATE(WAIT_FOR_PARENT,      "?PRN",
  97                   TRANSIT_TO(PARENT_READY,      1 << FSCACHE_OBJECT_EV_PARENT_READY));
  98
  99 static WAIT_STATE(WAIT_FOR_CMD,         "?CMD",
 100                   TRANSIT_TO(INVALIDATE_OBJECT, 1 << FSCACHE_OBJECT_EV_INVALIDATE),
 101                   TRANSIT_TO(UPDATE_OBJECT,     1 << FSCACHE_OBJECT_EV_UPDATE),
 102                   TRANSIT_TO(JUMPSTART_DEPS,    1 << FSCACHE_OBJECT_EV_NEW_CHILD));
 103
 104 static WAIT_STATE(WAIT_FOR_CLEARANCE,   "?CLR",
 105                   TRANSIT_TO(KILL_OBJECT,       1 << FSCACHE_OBJECT_EV_CLEARED));
 106
 107 /*
 108  * Out-of-band event transition tables.  These are for handling unexpected
 109  * events, such as an I/O error.  If an OOB event occurs, the state machine
 110  * clears and disables the event and forces a transition to the nominated work
 111  * state (acurrently executing work states will complete first).
 112  *
 113  * In such a situation, object->state remembers the state the machine should
 114  * have been in/gone to and returning NO_TRANSIT returns to that.
 115  */
 116 static const struct fscache_transition fscache_osm_init_oob[] = {
 117            TRANSIT_TO(ABORT_INIT,
 118                       (1 << FSCACHE_OBJECT_EV_ERROR) |
 119                       (1 << FSCACHE_OBJECT_EV_KILL)),
 120            { 0, NULL }
 121 };
 122
 123 static const struct fscache_transition fscache_osm_lookup_oob[] = {
 124            TRANSIT_TO(LOOKUP_FAILURE,
 125                       (1 << FSCACHE_OBJECT_EV_ERROR) |
 126                       (1 << FSCACHE_OBJECT_EV_KILL)),
 127            { 0, NULL }
 128 };
 129
 130 static const struct fscache_transition fscache_osm_run_oob[] = {
 131            TRANSIT_TO(KILL_OBJECT,
 132                       (1 << FSCACHE_OBJECT_EV_ERROR) |
 133                       (1 << FSCACHE_OBJECT_EV_KILL)),
 134            { 0, NULL }
 135 };
 136
 137 static int  fscache_get_object(struct fscache_object *,
 138                                enum fscache_obj_ref_trace);
 139 static void fscache_put_object(struct fscache_object *,
 140                                enum fscache_obj_ref_trace);
 141 static bool fscache_enqueue_dependents(struct fscache_object *, int);
 142 static void fscache_dequeue_object(struct fscache_object *);
 143 static void fscache_update_aux_data(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         bool oob;
 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                 oob = true;
 192                 for (t = object->oob_table; t->events; t++) {
 193                         if (events & t->events) {
 194                                 state = t->transit_to;
 195                                 ASSERT(state->work != NULL);
 196                                 event = fls(events & t->events) - 1;
 197                                 __clear_bit(event, &object->oob_event_mask);
 198                                 clear_bit(event, &object->events);
 199                                 goto execute_work_state;
 200                         }
 201                 }
 202         }
 203         oob = false;
 204
 205         /* Wait states are just transition tables */
 206         if (!state->work) {
 207                 if (events & event_mask) {
 208                         for (t = state->transitions; t->events; t++) {
 209                                 if (events & t->events) {
 210                                         new_state = t->transit_to;
 211                                         event = fls(events & t->events) - 1;
 212                                         trace_fscache_osm(object, state,
 213                                                           true, false, event);
 214                                         clear_bit(event, &object->events);
 215                                         _debug("{OBJ%x} ev %d: %s -> %s",
 216                                                object->debug_id, event,
 217                                                state->name, new_state->name);
 218                                         object->state = state = new_state;
 219                                         goto execute_work_state;
 220                                 }
 221                         }
 222
 223                         /* The event mask didn't include all the tabled bits */
 224                         BUG();
 225                 }
 226                 /* Randomly woke up */
 227                 goto unmask_events;
 228         }
 229
 230 execute_work_state:
 231         _debug("{OBJ%x} exec %s", object->debug_id, state->name);
 232
 233         trace_fscache_osm(object, state, false, oob, event);
 234         new_state = state->work(object, event);
 235         event = -1;
 236         if (new_state == NO_TRANSIT) {
 237                 _debug("{OBJ%x} %s notrans", object->debug_id, state->name);
 238                 if (unlikely(state == STATE(OBJECT_DEAD))) {
 239                         _leave(" [dead]");
 240                         return;
 241                 }
 242                 fscache_enqueue_object(object);
 243                 event_mask = object->oob_event_mask;
 244                 goto unmask_events;
 245         }
 246
 247         _debug("{OBJ%x} %s -> %s",
 248                object->debug_id, state->name, new_state->name);
 249         object->state = state = new_state;
 250
 251         if (state->work) {
 252                 if (unlikely(state == STATE(OBJECT_DEAD))) {
 253                         _leave(" [dead]");
 254                         return;
 255                 }
 256                 goto restart_masked;
 257         }
 258
 259         /* Transited to wait state */
 260         event_mask = object->oob_event_mask;
 261         for (t = state->transitions; t->events; t++)
 262                 event_mask |= t->events;
 263
 264 unmask_events:
 265         object->event_mask = event_mask;
 266         smp_mb();
 267         events = object->events;
 268         if (events & event_mask)
 269                 goto restart;
 270         _leave(" [msk %lx]", event_mask);
 271 }
 272
 273 /*
 274  * execute an object
 275  */
 276 static void fscache_object_work_func(struct work_struct *work)
 277 {
 278         struct fscache_object *object =
 279                 container_of(work, struct fscache_object, work);
 280         unsigned long start;
 281
 282         _enter("{OBJ%x}", object->debug_id);
 283
 284         start = jiffies;
 285         fscache_object_sm_dispatcher(object);
 286         fscache_hist(fscache_objs_histogram, start);
 287         fscache_put_object(object, fscache_obj_put_work);
 288 }
 289
 290 /**
 291  * fscache_object_init - Initialise a cache object description
 292  * @object: Object description
 293  * @cookie: Cookie object will be attached to
 294  * @cache: Cache in which backing object will be found
 295  *
 296  * Initialise a cache object description to its basic values.
 297  *
 298  * See Documentation/filesystems/caching/backend-api.rst for a complete
 299  * description.
 300  */
 301 void fscache_object_init(struct fscache_object *object,
 302                          struct fscache_cookie *cookie,
 303                          struct fscache_cache *cache)
 304 {
 305         const struct fscache_transition *t;
 306
 307         atomic_inc(&cache->object_count);
 308
 309         object->state = STATE(WAIT_FOR_INIT);
 310         object->oob_table = fscache_osm_init_oob;
 311         object->flags = 1 << FSCACHE_OBJECT_IS_LIVE;
 312         spin_lock_init(&object->lock);
 313         INIT_LIST_HEAD(&object->cache_link);
 314         INIT_HLIST_NODE(&object->cookie_link);
 315         INIT_WORK(&object->work, fscache_object_work_func);
 316         INIT_LIST_HEAD(&object->dependents);
 317         INIT_LIST_HEAD(&object->dep_link);
 318         INIT_LIST_HEAD(&object->pending_ops);
 319         object->n_children = 0;
 320         object->n_ops = object->n_in_progress = object->n_exclusive = 0;
 321         object->events = 0;
 322         object->store_limit = 0;
 323         object->store_limit_l = 0;
 324         object->cache = cache;
 325         object->cookie = cookie;
 326         fscache_cookie_get(cookie, fscache_cookie_get_attach_object);
 327         object->parent = NULL;
 328 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 329         RB_CLEAR_NODE(&object->objlist_link);
 330 #endif
 331
 332         object->oob_event_mask = 0;
 333         for (t = object->oob_table; t->events; t++)
 334                 object->oob_event_mask |= t->events;
 335         object->event_mask = object->oob_event_mask;
 336         for (t = object->state->transitions; t->events; t++)
 337                 object->event_mask |= t->events;
 338 }
 339 EXPORT_SYMBOL(fscache_object_init);
 340
 341 /*
 342  * Mark the object as no longer being live, making sure that we synchronise
 343  * against op submission.
 344  */
 345 static inline void fscache_mark_object_dead(struct fscache_object *object)
 346 {
 347         spin_lock(&object->lock);
 348         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 349         spin_unlock(&object->lock);
 350 }
 351
 352 /*
 353  * Abort object initialisation before we start it.
 354  */
 355 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
 356                                                                 int event)
 357 {
 358         _enter("{OBJ%x},%d", object->debug_id, event);
 359
 360         object->oob_event_mask = 0;
 361         fscache_dequeue_object(object);
 362         return transit_to(KILL_OBJECT);
 363 }
 364
 365 /*
 366  * initialise an object
 367  * - check the specified object's parent to see if we can make use of it
 368  *   immediately to do a creation
 369  * - we may need to start the process of creating a parent and we need to wait
 370  *   for the parent's lookup and creation to complete if it's not there yet
 371  */
 372 static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
 373                                                              int event)
 374 {
 375         struct fscache_object *parent;
 376         bool success;
 377
 378         _enter("{OBJ%x},%d", object->debug_id, event);
 379
 380         ASSERT(list_empty(&object->dep_link));
 381
 382         parent = object->parent;
 383         if (!parent) {
 384                 _leave(" [no parent]");
 385                 return transit_to(DROP_OBJECT);
 386         }
 387
 388         _debug("parent: %s of:%lx", parent->state->name, parent->flags);
 389
 390         if (fscache_object_is_dying(parent)) {
 391                 _leave(" [bad parent]");
 392                 return transit_to(DROP_OBJECT);
 393         }
 394
 395         if (fscache_object_is_available(parent)) {
 396                 _leave(" [ready]");
 397                 return transit_to(PARENT_READY);
 398         }
 399
 400         _debug("wait");
 401
 402         spin_lock(&parent->lock);
 403         fscache_stat(&fscache_n_cop_grab_object);
 404         success = false;
 405         if (fscache_object_is_live(parent) &&
 406             object->cache->ops->grab_object(object, fscache_obj_get_add_to_deps)) {
 407                 list_add(&object->dep_link, &parent->dependents);
 408                 success = true;
 409         }
 410         fscache_stat_d(&fscache_n_cop_grab_object);
 411         spin_unlock(&parent->lock);
 412         if (!success) {
 413                 _leave(" [grab failed]");
 414                 return transit_to(DROP_OBJECT);
 415         }
 416
 417         /* fscache_acquire_non_index_cookie() uses this
 418          * to wake the chain up */
 419         fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
 420         _leave(" [wait]");
 421         return transit_to(WAIT_FOR_PARENT);
 422 }
 423
 424 /*
 425  * Once the parent object is ready, we should kick off our lookup op.
 426  */
 427 static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
 428                                                         int event)
 429 {
 430         struct fscache_object *parent = object->parent;
 431
 432         _enter("{OBJ%x},%d", object->debug_id, event);
 433
 434         ASSERT(parent != NULL);
 435
 436         spin_lock(&parent->lock);
 437         parent->n_ops++;
 438         parent->n_obj_ops++;
 439         object->lookup_jif = jiffies;
 440         spin_unlock(&parent->lock);
 441
 442         _leave("");
 443         return transit_to(LOOK_UP_OBJECT);
 444 }
 445
 446 /*
 447  * look an object up in the cache from which it was allocated
 448  * - we hold an "access lock" on the parent object, so the parent object cannot
 449  *   be withdrawn by either party till we've finished
 450  */
 451 static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
 452                                                           int event)
 453 {
 454         struct fscache_cookie *cookie = object->cookie;
 455         struct fscache_object *parent = object->parent;
 456         int ret;
 457
 458         _enter("{OBJ%x},%d", object->debug_id, event);
 459
 460         object->oob_table = fscache_osm_lookup_oob;
 461
 462         ASSERT(parent != NULL);
 463         ASSERTCMP(parent->n_ops, >, 0);
 464         ASSERTCMP(parent->n_obj_ops, >, 0);
 465
 466         /* make sure the parent is still available */
 467         ASSERT(fscache_object_is_available(parent));
 468
 469         if (fscache_object_is_dying(parent) ||
 470             test_bit(FSCACHE_IOERROR, &object->cache->flags) ||
 471             !fscache_use_cookie(object)) {
 472                 _leave(" [unavailable]");
 473                 return transit_to(LOOKUP_FAILURE);
 474         }
 475
 476         _debug("LOOKUP \"%s\" in \"%s\"",
 477                cookie->def->name, object->cache->tag->name);
 478
 479         fscache_stat(&fscache_n_object_lookups);
 480         fscache_stat(&fscache_n_cop_lookup_object);
 481         ret = object->cache->ops->lookup_object(object);
 482         fscache_stat_d(&fscache_n_cop_lookup_object);
 483
 484         fscache_unuse_cookie(object);
 485
 486         if (ret == -ETIMEDOUT) {
 487                 /* probably stuck behind another object, so move this one to
 488                  * the back of the queue */
 489                 fscache_stat(&fscache_n_object_lookups_timed_out);
 490                 _leave(" [timeout]");
 491                 return NO_TRANSIT;
 492         }
 493
 494         if (ret < 0) {
 495                 _leave(" [error]");
 496                 return transit_to(LOOKUP_FAILURE);
 497         }
 498
 499         _leave(" [ok]");
 500         return transit_to(OBJECT_AVAILABLE);
 501 }
 502
 503 /**
 504  * fscache_object_lookup_negative - Note negative cookie lookup
 505  * @object: Object pointing to cookie to mark
 506  *
 507  * Note negative lookup, permitting those waiting to read data from an already
 508  * existing backing object to continue as there's no data for them to read.
 509  */
 510 void fscache_object_lookup_negative(struct fscache_object *object)
 511 {
 512         struct fscache_cookie *cookie = object->cookie;
 513
 514         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 515
 516         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 517                 fscache_stat(&fscache_n_object_lookups_negative);
 518
 519                 /* Allow write requests to begin stacking up and read requests to begin
 520                  * returning ENODATA.
 521                  */
 522                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 523                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 524
 525                 _debug("wake up lookup %p", &cookie->flags);
 526                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 527                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 528         }
 529         _leave("");
 530 }
 531 EXPORT_SYMBOL(fscache_object_lookup_negative);
 532
 533 /**
 534  * fscache_obtained_object - Note successful object lookup or creation
 535  * @object: Object pointing to cookie to mark
 536  *
 537  * Note successful lookup and/or creation, permitting those waiting to write
 538  * data to a backing object to continue.
 539  *
 540  * Note that after calling this, an object's cookie may be relinquished by the
 541  * netfs, and so must be accessed with object lock held.
 542  */
 543 void fscache_obtained_object(struct fscache_object *object)
 544 {
 545         struct fscache_cookie *cookie = object->cookie;
 546
 547         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 548
 549         /* if we were still looking up, then we must have a positive lookup
 550          * result, in which case there may be data available */
 551         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 552                 fscache_stat(&fscache_n_object_lookups_positive);
 553
 554                 /* We do (presumably) have data */
 555                 clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 556                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 557
 558                 /* Allow write requests to begin stacking up and read requests
 559                  * to begin shovelling data.
 560                  */
 561                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 562                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 563         } else {
 564                 fscache_stat(&fscache_n_object_created);
 565         }
 566
 567         set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
 568         _leave("");
 569 }
 570 EXPORT_SYMBOL(fscache_obtained_object);
 571
 572 /*
 573  * handle an object that has just become available
 574  */
 575 static const struct fscache_state *fscache_object_available(struct fscache_object *object,
 576                                                             int event)
 577 {
 578         _enter("{OBJ%x},%d", object->debug_id, event);
 579
 580         object->oob_table = fscache_osm_run_oob;
 581
 582         spin_lock(&object->lock);
 583
 584         fscache_done_parent_op(object);
 585         if (object->n_in_progress == 0) {
 586                 if (object->n_ops > 0) {
 587                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 588                         fscache_start_operations(object);
 589                 } else {
 590                         ASSERT(list_empty(&object->pending_ops));
 591                 }
 592         }
 593         spin_unlock(&object->lock);
 594
 595         fscache_stat(&fscache_n_cop_lookup_complete);
 596         object->cache->ops->lookup_complete(object);
 597         fscache_stat_d(&fscache_n_cop_lookup_complete);
 598
 599         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 600         fscache_stat(&fscache_n_object_avail);
 601
 602         _leave("");
 603         return transit_to(JUMPSTART_DEPS);
 604 }
 605
 606 /*
 607  * Wake up this object's dependent objects now that we've become available.
 608  */
 609 static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
 610                                                                 int event)
 611 {
 612         _enter("{OBJ%x},%d", object->debug_id, event);
 613
 614         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
 615                 return NO_TRANSIT; /* Not finished; requeue */
 616         return transit_to(WAIT_FOR_CMD);
 617 }
 618
 619 /*
 620  * Handle lookup or creation failute.
 621  */
 622 static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
 623                                                           int event)
 624 {
 625         struct fscache_cookie *cookie;
 626
 627         _enter("{OBJ%x},%d", object->debug_id, event);
 628
 629         object->oob_event_mask = 0;
 630
 631         fscache_stat(&fscache_n_cop_lookup_complete);
 632         object->cache->ops->lookup_complete(object);
 633         fscache_stat_d(&fscache_n_cop_lookup_complete);
 634
 635         set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags);
 636
 637         cookie = object->cookie;
 638         set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 639         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
 640                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 641
 642         fscache_done_parent_op(object);
 643         return transit_to(KILL_OBJECT);
 644 }
 645
 646 /*
 647  * Wait for completion of all active operations on this object and the death of
 648  * all child objects of this object.
 649  */
 650 static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
 651                                                        int event)
 652 {
 653         _enter("{OBJ%x,%d,%d},%d",
 654                object->debug_id, object->n_ops, object->n_children, event);
 655
 656         fscache_mark_object_dead(object);
 657         object->oob_event_mask = 0;
 658
 659         if (test_bit(FSCACHE_OBJECT_RETIRED, &object->flags)) {
 660                 /* Reject any new read/write ops and abort any that are pending. */
 661                 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 662                 fscache_cancel_all_ops(object);
 663         }
 664
 665         if (list_empty(&object->dependents) &&
 666             object->n_ops == 0 &&
 667             object->n_children == 0)
 668                 return transit_to(DROP_OBJECT);
 669
 670         if (object->n_in_progress == 0) {
 671                 spin_lock(&object->lock);
 672                 if (object->n_ops > 0 && object->n_in_progress == 0)
 673                         fscache_start_operations(object);
 674                 spin_unlock(&object->lock);
 675         }
 676
 677         if (!list_empty(&object->dependents))
 678                 return transit_to(KILL_DEPENDENTS);
 679
 680         return transit_to(WAIT_FOR_CLEARANCE);
 681 }
 682
 683 /*
 684  * Kill dependent objects.
 685  */
 686 static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
 687                                                            int event)
 688 {
 689         _enter("{OBJ%x},%d", object->debug_id, event);
 690
 691         if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
 692                 return NO_TRANSIT; /* Not finished */
 693         return transit_to(WAIT_FOR_CLEARANCE);
 694 }
 695
 696 /*
 697  * Drop an object's attachments
 698  */
 699 static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
 700                                                        int event)
 701 {
 702         struct fscache_object *parent = object->parent;
 703         struct fscache_cookie *cookie = object->cookie;
 704         struct fscache_cache *cache = object->cache;
 705         bool awaken = false;
 706
 707         _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
 708
 709         ASSERT(cookie != NULL);
 710         ASSERT(!hlist_unhashed(&object->cookie_link));
 711
 712         if (test_bit(FSCACHE_COOKIE_AUX_UPDATED, &cookie->flags)) {
 713                 _debug("final update");
 714                 fscache_update_aux_data(object);
 715         }
 716
 717         /* Make sure the cookie no longer points here and that the netfs isn't
 718          * waiting for us.
 719          */
 720         spin_lock(&cookie->lock);
 721         hlist_del_init(&object->cookie_link);
 722         if (hlist_empty(&cookie->backing_objects) &&
 723             test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 724                 awaken = true;
 725         spin_unlock(&cookie->lock);
 726
 727         if (awaken)
 728                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 729         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
 730                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 731
 732
 733         /* Prevent a race with our last child, which has to signal EV_CLEARED
 734          * before dropping our spinlock.
 735          */
 736         spin_lock(&object->lock);
 737         spin_unlock(&object->lock);
 738
 739         /* Discard from the cache's collection of objects */
 740         spin_lock(&cache->object_list_lock);
 741         list_del_init(&object->cache_link);
 742         spin_unlock(&cache->object_list_lock);
 743
 744         fscache_stat(&fscache_n_cop_drop_object);
 745         cache->ops->drop_object(object);
 746         fscache_stat_d(&fscache_n_cop_drop_object);
 747
 748         /* The parent object wants to know when all it dependents have gone */
 749         if (parent) {
 750                 _debug("release parent OBJ%x {%d}",
 751                        parent->debug_id, parent->n_children);
 752
 753                 spin_lock(&parent->lock);
 754                 parent->n_children--;
 755                 if (parent->n_children == 0)
 756                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 757                 spin_unlock(&parent->lock);
 758                 object->parent = NULL;
 759         }
 760
 761         /* this just shifts the object release to the work processor */
 762         fscache_put_object(object, fscache_obj_put_drop_obj);
 763         fscache_stat(&fscache_n_object_dead);
 764
 765         _leave("");
 766         return transit_to(OBJECT_DEAD);
 767 }
 768
 769 /*
 770  * get a ref on an object
 771  */
 772 static int fscache_get_object(struct fscache_object *object,
 773                               enum fscache_obj_ref_trace why)
 774 {
 775         int ret;
 776
 777         fscache_stat(&fscache_n_cop_grab_object);
 778         ret = object->cache->ops->grab_object(object, why) ? 0 : -EAGAIN;
 779         fscache_stat_d(&fscache_n_cop_grab_object);
 780         return ret;
 781 }
 782
 783 /*
 784  * Discard a ref on an object
 785  */
 786 static void fscache_put_object(struct fscache_object *object,
 787                                enum fscache_obj_ref_trace why)
 788 {
 789         fscache_stat(&fscache_n_cop_put_object);
 790         object->cache->ops->put_object(object, why);
 791         fscache_stat_d(&fscache_n_cop_put_object);
 792 }
 793
 794 /**
 795  * fscache_object_destroy - Note that a cache object is about to be destroyed
 796  * @object: The object to be destroyed
 797  *
 798  * Note the imminent destruction and deallocation of a cache object record.
 799  */
 800 void fscache_object_destroy(struct fscache_object *object)
 801 {
 802         fscache_objlist_remove(object);
 803
 804         /* We can get rid of the cookie now */
 805         fscache_cookie_put(object->cookie, fscache_cookie_put_object);
 806         object->cookie = NULL;
 807 }
 808 EXPORT_SYMBOL(fscache_object_destroy);
 809
 810 /*
 811  * enqueue an object for metadata-type processing
 812  */
 813 void fscache_enqueue_object(struct fscache_object *object)
 814 {
 815         _enter("{OBJ%x}", object->debug_id);
 816
 817         if (fscache_get_object(object, fscache_obj_get_queue) >= 0) {
 818                 wait_queue_head_t *cong_wq =
 819                         &get_cpu_var(fscache_object_cong_wait);
 820
 821                 if (queue_work(fscache_object_wq, &object->work)) {
 822                         if (fscache_object_congested())
 823                                 wake_up(cong_wq);
 824                 } else
 825                         fscache_put_object(object, fscache_obj_put_queue);
 826
 827                 put_cpu_var(fscache_object_cong_wait);
 828         }
 829 }
 830
 831 /**
 832  * fscache_object_sleep_till_congested - Sleep until object wq is congested
 833  * @timeoutp: Scheduler sleep timeout
 834  *
 835  * Allow an object handler to sleep until the object workqueue is congested.
 836  *
 837  * The caller must set up a wake up event before calling this and must have set
 838  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 839  * condition before calling this function as no test is made here.
 840  *
 841  * %true is returned if the object wq is congested, %false otherwise.
 842  */
 843 bool fscache_object_sleep_till_congested(signed long *timeoutp)
 844 {
 845         wait_queue_head_t *cong_wq = this_cpu_ptr(&fscache_object_cong_wait);
 846         DEFINE_WAIT(wait);
 847
 848         if (fscache_object_congested())
 849                 return true;
 850
 851         add_wait_queue_exclusive(cong_wq, &wait);
 852         if (!fscache_object_congested())
 853                 *timeoutp = schedule_timeout(*timeoutp);
 854         finish_wait(cong_wq, &wait);
 855
 856         return fscache_object_congested();
 857 }
 858 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 859
 860 /*
 861  * Enqueue the dependents of an object for metadata-type processing.
 862  *
 863  * If we don't manage to finish the list before the scheduler wants to run
 864  * again then return false immediately.  We return true if the list was
 865  * cleared.
 866  */
 867 static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
 868 {
 869         struct fscache_object *dep;
 870         bool ret = true;
 871
 872         _enter("{OBJ%x}", object->debug_id);
 873
 874         if (list_empty(&object->dependents))
 875                 return true;
 876
 877         spin_lock(&object->lock);
 878
 879         while (!list_empty(&object->dependents)) {
 880                 dep = list_entry(object->dependents.next,
 881                                  struct fscache_object, dep_link);
 882                 list_del_init(&dep->dep_link);
 883
 884                 fscache_raise_event(dep, event);
 885                 fscache_put_object(dep, fscache_obj_put_enq_dep);
 886
 887                 if (!list_empty(&object->dependents) && need_resched()) {
 888                         ret = false;
 889                         break;
 890                 }
 891         }
 892
 893         spin_unlock(&object->lock);
 894         return ret;
 895 }
 896
 897 /*
 898  * remove an object from whatever queue it's waiting on
 899  */
 900 static void fscache_dequeue_object(struct fscache_object *object)
 901 {
 902         _enter("{OBJ%x}", object->debug_id);
 903
 904         if (!list_empty(&object->dep_link)) {
 905                 spin_lock(&object->parent->lock);
 906                 list_del_init(&object->dep_link);
 907                 spin_unlock(&object->parent->lock);
 908         }
 909
 910         _leave("");
 911 }
 912
 913 /**
 914  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 915  * @object: The object to ask about
 916  * @data: The auxiliary data for the object
 917  * @datalen: The size of the auxiliary data
 918  *
 919  * This function consults the netfs about the coherency state of an object.
 920  * The caller must be holding a ref on cookie->n_active (held by
 921  * fscache_look_up_object() on behalf of the cache backend during object lookup
 922  * and creation).
 923  */
 924 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 925                                         const void *data, uint16_t datalen,
 926                                         loff_t object_size)
 927 {
 928         enum fscache_checkaux result;
 929
 930         if (!object->cookie->def->check_aux) {
 931                 fscache_stat(&fscache_n_checkaux_none);
 932                 return FSCACHE_CHECKAUX_OKAY;
 933         }
 934
 935         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 936                                                 data, datalen, object_size);
 937         switch (result) {
 938                 /* entry okay as is */
 939         case FSCACHE_CHECKAUX_OKAY:
 940                 fscache_stat(&fscache_n_checkaux_okay);
 941                 break;
 942
 943                 /* entry requires update */
 944         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 945                 fscache_stat(&fscache_n_checkaux_update);
 946                 break;
 947
 948                 /* entry requires deletion */
 949         case FSCACHE_CHECKAUX_OBSOLETE:
 950                 fscache_stat(&fscache_n_checkaux_obsolete);
 951                 break;
 952
 953         default:
 954                 BUG();
 955         }
 956
 957         return result;
 958 }
 959 EXPORT_SYMBOL(fscache_check_aux);
 960
 961 /*
 962  * Asynchronously invalidate an object.
 963  */
 964 static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
 965                                                               int event)
 966 {
 967         struct fscache_operation *op;
 968         struct fscache_cookie *cookie = object->cookie;
 969
 970         _enter("{OBJ%x},%d", object->debug_id, event);
 971
 972         /* We're going to need the cookie.  If the cookie is not available then
 973          * retire the object instead.
 974          */
 975         if (!fscache_use_cookie(object)) {
 976                 ASSERT(radix_tree_empty(&object->cookie->stores));
 977                 set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
 978                 _leave(" [no cookie]");
 979                 return transit_to(KILL_OBJECT);
 980         }
 981
 982         /* Reject any new read/write ops and abort any that are pending. */
 983         fscache_invalidate_writes(cookie);
 984         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 985         fscache_cancel_all_ops(object);
 986
 987         /* Now we have to wait for in-progress reads and writes */
 988         op = kzalloc(sizeof(*op), GFP_KERNEL);
 989         if (!op)
 990                 goto nomem;
 991
 992         fscache_operation_init(cookie, op, object->cache->ops->invalidate_object,
 993                                NULL, NULL);
 994         op->flags = FSCACHE_OP_ASYNC |
 995                 (1 << FSCACHE_OP_EXCLUSIVE) |
 996                 (1 << FSCACHE_OP_UNUSE_COOKIE);
 997         trace_fscache_page_op(cookie, NULL, op, fscache_page_op_invalidate);
 998
 999         spin_lock(&cookie->lock);
1000         if (fscache_submit_exclusive_op(object, op) < 0)
1001                 goto submit_op_failed;
1002         spin_unlock(&cookie->lock);
1003         fscache_put_operation(op);
1004
1005         /* Once we've completed the invalidation, we know there will be no data
1006          * stored in the cache and thus we can reinstate the data-check-skip
1007          * optimisation.
1008          */
1009         set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
1010
1011         /* We can allow read and write requests to come in once again.  They'll
1012          * queue up behind our exclusive invalidation operation.
1013          */
1014         if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
1015                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
1016         _leave(" [ok]");
1017         return transit_to(UPDATE_OBJECT);
1018
1019 nomem:
1020         fscache_mark_object_dead(object);
1021         fscache_unuse_cookie(object);
1022         _leave(" [ENOMEM]");
1023         return transit_to(KILL_OBJECT);
1024
1025 submit_op_failed:
1026         fscache_mark_object_dead(object);
1027         spin_unlock(&cookie->lock);
1028         fscache_unuse_cookie(object);
1029         kfree(op);
1030         _leave(" [EIO]");
1031         return transit_to(KILL_OBJECT);
1032 }
1033
1034 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
1035                                                              int event)
1036 {
1037         const struct fscache_state *s;
1038
1039         fscache_stat(&fscache_n_invalidates_run);
1040         fscache_stat(&fscache_n_cop_invalidate_object);
1041         s = _fscache_invalidate_object(object, event);
1042         fscache_stat_d(&fscache_n_cop_invalidate_object);
1043         return s;
1044 }
1045
1046 /*
1047  * Update auxiliary data.
1048  */
1049 static void fscache_update_aux_data(struct fscache_object *object)
1050 {
1051         fscache_stat(&fscache_n_updates_run);
1052         fscache_stat(&fscache_n_cop_update_object);
1053         object->cache->ops->update_object(object);
1054         fscache_stat_d(&fscache_n_cop_update_object);
1055 }
1056
1057 /*
1058  * Asynchronously update an object.
1059  */
1060 static const struct fscache_state *fscache_update_object(struct fscache_object *object,
1061                                                          int event)
1062 {
1063         _enter("{OBJ%x},%d", object->debug_id, event);
1064
1065         fscache_update_aux_data(object);
1066
1067         _leave("");
1068         return transit_to(WAIT_FOR_CMD);
1069 }
1070
1071 /**
1072  * fscache_object_retrying_stale - Note retrying stale object
1073  * @object: The object that will be retried
1074  *
1075  * Note that an object lookup found an on-disk object that was adjudged to be
1076  * stale and has been deleted.  The lookup will be retried.
1077  */
1078 void fscache_object_retrying_stale(struct fscache_object *object)
1079 {
1080         fscache_stat(&fscache_n_cache_no_space_reject);
1081 }
1082 EXPORT_SYMBOL(fscache_object_retrying_stale);
1083
1084 /**
1085  * fscache_object_mark_killed - Note that an object was killed
1086  * @object: The object that was culled
1087  * @why: The reason the object was killed.
1088  *
1089  * Note that an object was killed.  Returns true if the object was
1090  * already marked killed, false if it wasn't.
1091  */
1092 void fscache_object_mark_killed(struct fscache_object *object,
1093                                 enum fscache_why_object_killed why)
1094 {
1095         if (test_and_set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags)) {
1096                 pr_err("Error: Object already killed by cache [%s]\n",
1097                        object->cache->identifier);
1098                 return;
1099         }
1100
1101         switch (why) {
1102         case FSCACHE_OBJECT_NO_SPACE:
1103                 fscache_stat(&fscache_n_cache_no_space_reject);
1104                 break;
1105         case FSCACHE_OBJECT_IS_STALE:
1106                 fscache_stat(&fscache_n_cache_stale_objects);
1107                 break;
1108         case FSCACHE_OBJECT_WAS_RETIRED:
1109                 fscache_stat(&fscache_n_cache_retired_objects);
1110                 break;
1111         case FSCACHE_OBJECT_WAS_CULLED:
1112                 fscache_stat(&fscache_n_cache_culled_objects);
1113                 break;
1114         }
1115 }
1116 EXPORT_SYMBOL(fscache_object_mark_killed);
1117
1118 /*
1119  * The object is dead.  We can get here if an object gets queued by an event
1120  * that would lead to its death (such as EV_KILL) when the dispatcher is
1121  * already running (and so can be requeued) but hasn't yet cleared the event
1122  * mask.
1123  */
1124 static const struct fscache_state *fscache_object_dead(struct fscache_object *object,
1125                                                        int event)
1126 {
1127         if (!test_and_set_bit(FSCACHE_OBJECT_RUN_AFTER_DEAD,
1128                               &object->flags))
1129                 return NO_TRANSIT;
1130
1131         WARN(true, "FS-Cache object redispatched after death");
1132         return NO_TRANSIT;
1133 }