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
 281         _enter("{OBJ%x}", object->debug_id);
 282
 283         fscache_object_sm_dispatcher(object);
 284         fscache_put_object(object, fscache_obj_put_work);
 285 }
 286
 287 /**
 288  * fscache_object_init - Initialise a cache object description
 289  * @object: Object description
 290  * @cookie: Cookie object will be attached to
 291  * @cache: Cache in which backing object will be found
 292  *
 293  * Initialise a cache object description to its basic values.
 294  *
 295  * See Documentation/filesystems/caching/backend-api.rst for a complete
 296  * description.
 297  */
 298 void fscache_object_init(struct fscache_object *object,
 299                          struct fscache_cookie *cookie,
 300                          struct fscache_cache *cache)
 301 {
 302         const struct fscache_transition *t;
 303
 304         atomic_inc(&cache->object_count);
 305
 306         object->state = STATE(WAIT_FOR_INIT);
 307         object->oob_table = fscache_osm_init_oob;
 308         object->flags = 1 << FSCACHE_OBJECT_IS_LIVE;
 309         spin_lock_init(&object->lock);
 310         INIT_LIST_HEAD(&object->cache_link);
 311         INIT_HLIST_NODE(&object->cookie_link);
 312         INIT_WORK(&object->work, fscache_object_work_func);
 313         INIT_LIST_HEAD(&object->dependents);
 314         INIT_LIST_HEAD(&object->dep_link);
 315         INIT_LIST_HEAD(&object->pending_ops);
 316         object->n_children = 0;
 317         object->n_ops = object->n_in_progress = object->n_exclusive = 0;
 318         object->events = 0;
 319         object->store_limit = 0;
 320         object->store_limit_l = 0;
 321         object->cache = cache;
 322         object->cookie = cookie;
 323         fscache_cookie_get(cookie, fscache_cookie_get_attach_object);
 324         object->parent = NULL;
 325 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 326         RB_CLEAR_NODE(&object->objlist_link);
 327 #endif
 328
 329         object->oob_event_mask = 0;
 330         for (t = object->oob_table; t->events; t++)
 331                 object->oob_event_mask |= t->events;
 332         object->event_mask = object->oob_event_mask;
 333         for (t = object->state->transitions; t->events; t++)
 334                 object->event_mask |= t->events;
 335 }
 336 EXPORT_SYMBOL(fscache_object_init);
 337
 338 /*
 339  * Mark the object as no longer being live, making sure that we synchronise
 340  * against op submission.
 341  */
 342 static inline void fscache_mark_object_dead(struct fscache_object *object)
 343 {
 344         spin_lock(&object->lock);
 345         clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 346         spin_unlock(&object->lock);
 347 }
 348
 349 /*
 350  * Abort object initialisation before we start it.
 351  */
 352 static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
 353                                                                 int event)
 354 {
 355         _enter("{OBJ%x},%d", object->debug_id, event);
 356
 357         object->oob_event_mask = 0;
 358         fscache_dequeue_object(object);
 359         return transit_to(KILL_OBJECT);
 360 }
 361
 362 /*
 363  * initialise an object
 364  * - check the specified object's parent to see if we can make use of it
 365  *   immediately to do a creation
 366  * - we may need to start the process of creating a parent and we need to wait
 367  *   for the parent's lookup and creation to complete if it's not there yet
 368  */
 369 static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
 370                                                              int event)
 371 {
 372         struct fscache_object *parent;
 373         bool success;
 374
 375         _enter("{OBJ%x},%d", object->debug_id, event);
 376
 377         ASSERT(list_empty(&object->dep_link));
 378
 379         parent = object->parent;
 380         if (!parent) {
 381                 _leave(" [no parent]");
 382                 return transit_to(DROP_OBJECT);
 383         }
 384
 385         _debug("parent: %s of:%lx", parent->state->name, parent->flags);
 386
 387         if (fscache_object_is_dying(parent)) {
 388                 _leave(" [bad parent]");
 389                 return transit_to(DROP_OBJECT);
 390         }
 391
 392         if (fscache_object_is_available(parent)) {
 393                 _leave(" [ready]");
 394                 return transit_to(PARENT_READY);
 395         }
 396
 397         _debug("wait");
 398
 399         spin_lock(&parent->lock);
 400         fscache_stat(&fscache_n_cop_grab_object);
 401         success = false;
 402         if (fscache_object_is_live(parent) &&
 403             object->cache->ops->grab_object(object, fscache_obj_get_add_to_deps)) {
 404                 list_add(&object->dep_link, &parent->dependents);
 405                 success = true;
 406         }
 407         fscache_stat_d(&fscache_n_cop_grab_object);
 408         spin_unlock(&parent->lock);
 409         if (!success) {
 410                 _leave(" [grab failed]");
 411                 return transit_to(DROP_OBJECT);
 412         }
 413
 414         /* fscache_acquire_non_index_cookie() uses this
 415          * to wake the chain up */
 416         fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
 417         _leave(" [wait]");
 418         return transit_to(WAIT_FOR_PARENT);
 419 }
 420
 421 /*
 422  * Once the parent object is ready, we should kick off our lookup op.
 423  */
 424 static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
 425                                                         int event)
 426 {
 427         struct fscache_object *parent = object->parent;
 428
 429         _enter("{OBJ%x},%d", object->debug_id, event);
 430
 431         ASSERT(parent != NULL);
 432
 433         spin_lock(&parent->lock);
 434         parent->n_ops++;
 435         parent->n_obj_ops++;
 436         spin_unlock(&parent->lock);
 437
 438         _leave("");
 439         return transit_to(LOOK_UP_OBJECT);
 440 }
 441
 442 /*
 443  * look an object up in the cache from which it was allocated
 444  * - we hold an "access lock" on the parent object, so the parent object cannot
 445  *   be withdrawn by either party till we've finished
 446  */
 447 static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
 448                                                           int event)
 449 {
 450         struct fscache_cookie *cookie = object->cookie;
 451         struct fscache_object *parent = object->parent;
 452         int ret;
 453
 454         _enter("{OBJ%x},%d", object->debug_id, event);
 455
 456         object->oob_table = fscache_osm_lookup_oob;
 457
 458         ASSERT(parent != NULL);
 459         ASSERTCMP(parent->n_ops, >, 0);
 460         ASSERTCMP(parent->n_obj_ops, >, 0);
 461
 462         /* make sure the parent is still available */
 463         ASSERT(fscache_object_is_available(parent));
 464
 465         if (fscache_object_is_dying(parent) ||
 466             test_bit(FSCACHE_IOERROR, &object->cache->flags) ||
 467             !fscache_use_cookie(object)) {
 468                 _leave(" [unavailable]");
 469                 return transit_to(LOOKUP_FAILURE);
 470         }
 471
 472         _debug("LOOKUP \"%s\" in \"%s\"",
 473                cookie->def->name, object->cache->tag->name);
 474
 475         fscache_stat(&fscache_n_object_lookups);
 476         fscache_stat(&fscache_n_cop_lookup_object);
 477         ret = object->cache->ops->lookup_object(object);
 478         fscache_stat_d(&fscache_n_cop_lookup_object);
 479
 480         fscache_unuse_cookie(object);
 481
 482         if (ret == -ETIMEDOUT) {
 483                 /* probably stuck behind another object, so move this one to
 484                  * the back of the queue */
 485                 fscache_stat(&fscache_n_object_lookups_timed_out);
 486                 _leave(" [timeout]");
 487                 return NO_TRANSIT;
 488         }
 489
 490         if (ret < 0) {
 491                 _leave(" [error]");
 492                 return transit_to(LOOKUP_FAILURE);
 493         }
 494
 495         _leave(" [ok]");
 496         return transit_to(OBJECT_AVAILABLE);
 497 }
 498
 499 /**
 500  * fscache_object_lookup_negative - Note negative cookie lookup
 501  * @object: Object pointing to cookie to mark
 502  *
 503  * Note negative lookup, permitting those waiting to read data from an already
 504  * existing backing object to continue as there's no data for them to read.
 505  */
 506 void fscache_object_lookup_negative(struct fscache_object *object)
 507 {
 508         struct fscache_cookie *cookie = object->cookie;
 509
 510         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 511
 512         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 513                 fscache_stat(&fscache_n_object_lookups_negative);
 514
 515                 /* Allow write requests to begin stacking up and read requests to begin
 516                  * returning ENODATA.
 517                  */
 518                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 519                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 520
 521                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 522                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 523         }
 524         _leave("");
 525 }
 526 EXPORT_SYMBOL(fscache_object_lookup_negative);
 527
 528 /**
 529  * fscache_obtained_object - Note successful object lookup or creation
 530  * @object: Object pointing to cookie to mark
 531  *
 532  * Note successful lookup and/or creation, permitting those waiting to write
 533  * data to a backing object to continue.
 534  *
 535  * Note that after calling this, an object's cookie may be relinquished by the
 536  * netfs, and so must be accessed with object lock held.
 537  */
 538 void fscache_obtained_object(struct fscache_object *object)
 539 {
 540         struct fscache_cookie *cookie = object->cookie;
 541
 542         _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 543
 544         /* if we were still looking up, then we must have a positive lookup
 545          * result, in which case there may be data available */
 546         if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 547                 fscache_stat(&fscache_n_object_lookups_positive);
 548
 549                 /* We do (presumably) have data */
 550                 clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 551                 clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 552
 553                 /* Allow write requests to begin stacking up and read requests
 554                  * to begin shovelling data.
 555                  */
 556                 clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 557                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 558         } else {
 559                 fscache_stat(&fscache_n_object_created);
 560         }
 561
 562         set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
 563         _leave("");
 564 }
 565 EXPORT_SYMBOL(fscache_obtained_object);
 566
 567 /*
 568  * handle an object that has just become available
 569  */
 570 static const struct fscache_state *fscache_object_available(struct fscache_object *object,
 571                                                             int event)
 572 {
 573         _enter("{OBJ%x},%d", object->debug_id, event);
 574
 575         object->oob_table = fscache_osm_run_oob;
 576
 577         spin_lock(&object->lock);
 578
 579         fscache_done_parent_op(object);
 580         if (object->n_in_progress == 0) {
 581                 if (object->n_ops > 0) {
 582                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 583                         fscache_start_operations(object);
 584                 } else {
 585                         ASSERT(list_empty(&object->pending_ops));
 586                 }
 587         }
 588         spin_unlock(&object->lock);
 589
 590         fscache_stat(&fscache_n_cop_lookup_complete);
 591         object->cache->ops->lookup_complete(object);
 592         fscache_stat_d(&fscache_n_cop_lookup_complete);
 593
 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         if (test_bit(FSCACHE_COOKIE_AUX_UPDATED, &cookie->flags)) {
 707                 _debug("final update");
 708                 fscache_update_aux_data(object);
 709         }
 710
 711         /* Make sure the cookie no longer points here and that the netfs isn't
 712          * waiting for us.
 713          */
 714         spin_lock(&cookie->lock);
 715         hlist_del_init(&object->cookie_link);
 716         if (hlist_empty(&cookie->backing_objects) &&
 717             test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 718                 awaken = true;
 719         spin_unlock(&cookie->lock);
 720
 721         if (awaken)
 722                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 723         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
 724                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 725
 726
 727         /* Prevent a race with our last child, which has to signal EV_CLEARED
 728          * before dropping our spinlock.
 729          */
 730         spin_lock(&object->lock);
 731         spin_unlock(&object->lock);
 732
 733         /* Discard from the cache's collection of objects */
 734         spin_lock(&cache->object_list_lock);
 735         list_del_init(&object->cache_link);
 736         spin_unlock(&cache->object_list_lock);
 737
 738         fscache_stat(&fscache_n_cop_drop_object);
 739         cache->ops->drop_object(object);
 740         fscache_stat_d(&fscache_n_cop_drop_object);
 741
 742         /* The parent object wants to know when all it dependents have gone */
 743         if (parent) {
 744                 _debug("release parent OBJ%x {%d}",
 745                        parent->debug_id, parent->n_children);
 746
 747                 spin_lock(&parent->lock);
 748                 parent->n_children--;
 749                 if (parent->n_children == 0)
 750                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 751                 spin_unlock(&parent->lock);
 752                 object->parent = NULL;
 753         }
 754
 755         /* this just shifts the object release to the work processor */
 756         fscache_put_object(object, fscache_obj_put_drop_obj);
 757         fscache_stat(&fscache_n_object_dead);
 758
 759         _leave("");
 760         return transit_to(OBJECT_DEAD);
 761 }
 762
 763 /*
 764  * get a ref on an object
 765  */
 766 static int fscache_get_object(struct fscache_object *object,
 767                               enum fscache_obj_ref_trace why)
 768 {
 769         int ret;
 770
 771         fscache_stat(&fscache_n_cop_grab_object);
 772         ret = object->cache->ops->grab_object(object, why) ? 0 : -EAGAIN;
 773         fscache_stat_d(&fscache_n_cop_grab_object);
 774         return ret;
 775 }
 776
 777 /*
 778  * Discard a ref on an object
 779  */
 780 static void fscache_put_object(struct fscache_object *object,
 781                                enum fscache_obj_ref_trace why)
 782 {
 783         fscache_stat(&fscache_n_cop_put_object);
 784         object->cache->ops->put_object(object, why);
 785         fscache_stat_d(&fscache_n_cop_put_object);
 786 }
 787
 788 /**
 789  * fscache_object_destroy - Note that a cache object is about to be destroyed
 790  * @object: The object to be destroyed
 791  *
 792  * Note the imminent destruction and deallocation of a cache object record.
 793  */
 794 void fscache_object_destroy(struct fscache_object *object)
 795 {
 796         /* We can get rid of the cookie now */
 797         fscache_cookie_put(object->cookie, fscache_cookie_put_object);
 798         object->cookie = NULL;
 799 }
 800 EXPORT_SYMBOL(fscache_object_destroy);
 801
 802 /*
 803  * enqueue an object for metadata-type processing
 804  */
 805 void fscache_enqueue_object(struct fscache_object *object)
 806 {
 807         _enter("{OBJ%x}", object->debug_id);
 808
 809         if (fscache_get_object(object, fscache_obj_get_queue) >= 0) {
 810                 wait_queue_head_t *cong_wq =
 811                         &get_cpu_var(fscache_object_cong_wait);
 812
 813                 if (queue_work(fscache_object_wq, &object->work)) {
 814                         if (fscache_object_congested())
 815                                 wake_up(cong_wq);
 816                 } else
 817                         fscache_put_object(object, fscache_obj_put_queue);
 818
 819                 put_cpu_var(fscache_object_cong_wait);
 820         }
 821 }
 822
 823 /**
 824  * fscache_object_sleep_till_congested - Sleep until object wq is congested
 825  * @timeoutp: Scheduler sleep timeout
 826  *
 827  * Allow an object handler to sleep until the object workqueue is congested.
 828  *
 829  * The caller must set up a wake up event before calling this and must have set
 830  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 831  * condition before calling this function as no test is made here.
 832  *
 833  * %true is returned if the object wq is congested, %false otherwise.
 834  */
 835 bool fscache_object_sleep_till_congested(signed long *timeoutp)
 836 {
 837         wait_queue_head_t *cong_wq = this_cpu_ptr(&fscache_object_cong_wait);
 838         DEFINE_WAIT(wait);
 839
 840         if (fscache_object_congested())
 841                 return true;
 842
 843         add_wait_queue_exclusive(cong_wq, &wait);
 844         if (!fscache_object_congested())
 845                 *timeoutp = schedule_timeout(*timeoutp);
 846         finish_wait(cong_wq, &wait);
 847
 848         return fscache_object_congested();
 849 }
 850 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 851
 852 /*
 853  * Enqueue the dependents of an object for metadata-type processing.
 854  *
 855  * If we don't manage to finish the list before the scheduler wants to run
 856  * again then return false immediately.  We return true if the list was
 857  * cleared.
 858  */
 859 static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
 860 {
 861         struct fscache_object *dep;
 862         bool ret = true;
 863
 864         _enter("{OBJ%x}", object->debug_id);
 865
 866         if (list_empty(&object->dependents))
 867                 return true;
 868
 869         spin_lock(&object->lock);
 870
 871         while (!list_empty(&object->dependents)) {
 872                 dep = list_entry(object->dependents.next,
 873                                  struct fscache_object, dep_link);
 874                 list_del_init(&dep->dep_link);
 875
 876                 fscache_raise_event(dep, event);
 877                 fscache_put_object(dep, fscache_obj_put_enq_dep);
 878
 879                 if (!list_empty(&object->dependents) && need_resched()) {
 880                         ret = false;
 881                         break;
 882                 }
 883         }
 884
 885         spin_unlock(&object->lock);
 886         return ret;
 887 }
 888
 889 /*
 890  * remove an object from whatever queue it's waiting on
 891  */
 892 static void fscache_dequeue_object(struct fscache_object *object)
 893 {
 894         _enter("{OBJ%x}", object->debug_id);
 895
 896         if (!list_empty(&object->dep_link)) {
 897                 spin_lock(&object->parent->lock);
 898                 list_del_init(&object->dep_link);
 899                 spin_unlock(&object->parent->lock);
 900         }
 901
 902         _leave("");
 903 }
 904
 905 /**
 906  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 907  * @object: The object to ask about
 908  * @data: The auxiliary data for the object
 909  * @datalen: The size of the auxiliary data
 910  *
 911  * This function consults the netfs about the coherency state of an object.
 912  * The caller must be holding a ref on cookie->n_active (held by
 913  * fscache_look_up_object() on behalf of the cache backend during object lookup
 914  * and creation).
 915  */
 916 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 917                                         const void *data, uint16_t datalen,
 918                                         loff_t object_size)
 919 {
 920         enum fscache_checkaux result;
 921
 922         if (!object->cookie->def->check_aux) {
 923                 fscache_stat(&fscache_n_checkaux_none);
 924                 return FSCACHE_CHECKAUX_OKAY;
 925         }
 926
 927         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 928                                                 data, datalen, object_size);
 929         switch (result) {
 930                 /* entry okay as is */
 931         case FSCACHE_CHECKAUX_OKAY:
 932                 fscache_stat(&fscache_n_checkaux_okay);
 933                 break;
 934
 935                 /* entry requires update */
 936         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 937                 fscache_stat(&fscache_n_checkaux_update);
 938                 break;
 939
 940                 /* entry requires deletion */
 941         case FSCACHE_CHECKAUX_OBSOLETE:
 942                 fscache_stat(&fscache_n_checkaux_obsolete);
 943                 break;
 944
 945         default:
 946                 BUG();
 947         }
 948
 949         return result;
 950 }
 951 EXPORT_SYMBOL(fscache_check_aux);
 952
 953 /*
 954  * Asynchronously invalidate an object.
 955  */
 956 static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
 957                                                               int event)
 958 {
 959         struct fscache_operation *op;
 960         struct fscache_cookie *cookie = object->cookie;
 961
 962         _enter("{OBJ%x},%d", object->debug_id, event);
 963
 964         /* We're going to need the cookie.  If the cookie is not available then
 965          * retire the object instead.
 966          */
 967         if (!fscache_use_cookie(object)) {
 968                 ASSERT(radix_tree_empty(&object->cookie->stores));
 969                 set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
 970                 _leave(" [no cookie]");
 971                 return transit_to(KILL_OBJECT);
 972         }
 973
 974         /* Reject any new read/write ops and abort any that are pending. */
 975         fscache_invalidate_writes(cookie);
 976         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 977         fscache_cancel_all_ops(object);
 978
 979         /* Now we have to wait for in-progress reads and writes */
 980         op = kzalloc(sizeof(*op), GFP_KERNEL);
 981         if (!op)
 982                 goto nomem;
 983
 984         fscache_operation_init(cookie, op, object->cache->ops->invalidate_object,
 985                                NULL, NULL);
 986         op->flags = FSCACHE_OP_ASYNC |
 987                 (1 << FSCACHE_OP_EXCLUSIVE) |
 988                 (1 << FSCACHE_OP_UNUSE_COOKIE);
 989         trace_fscache_page_op(cookie, NULL, op, fscache_page_op_invalidate);
 990
 991         spin_lock(&cookie->lock);
 992         if (fscache_submit_exclusive_op(object, op) < 0)
 993                 goto submit_op_failed;
 994         spin_unlock(&cookie->lock);
 995         fscache_put_operation(op);
 996
 997         /* Once we've completed the invalidation, we know there will be no data
 998          * stored in the cache and thus we can reinstate the data-check-skip
 999          * optimisation.
1000          */
1001         set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
1002
1003         /* We can allow read and write requests to come in once again.  They'll
1004          * queue up behind our exclusive invalidation operation.
1005          */
1006         if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
1007                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
1008         _leave(" [ok]");
1009         return transit_to(UPDATE_OBJECT);
1010
1011 nomem:
1012         fscache_mark_object_dead(object);
1013         fscache_unuse_cookie(object);
1014         _leave(" [ENOMEM]");
1015         return transit_to(KILL_OBJECT);
1016
1017 submit_op_failed:
1018         fscache_mark_object_dead(object);
1019         spin_unlock(&cookie->lock);
1020         fscache_unuse_cookie(object);
1021         kfree(op);
1022         _leave(" [EIO]");
1023         return transit_to(KILL_OBJECT);
1024 }
1025
1026 static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
1027                                                              int event)
1028 {
1029         const struct fscache_state *s;
1030
1031         fscache_stat(&fscache_n_invalidates_run);
1032         fscache_stat(&fscache_n_cop_invalidate_object);
1033         s = _fscache_invalidate_object(object, event);
1034         fscache_stat_d(&fscache_n_cop_invalidate_object);
1035         return s;
1036 }
1037
1038 /*
1039  * Update auxiliary data.
1040  */
1041 static void fscache_update_aux_data(struct fscache_object *object)
1042 {
1043         fscache_stat(&fscache_n_updates_run);
1044         fscache_stat(&fscache_n_cop_update_object);
1045         object->cache->ops->update_object(object);
1046         fscache_stat_d(&fscache_n_cop_update_object);
1047 }
1048
1049 /*
1050  * Asynchronously update an object.
1051  */
1052 static const struct fscache_state *fscache_update_object(struct fscache_object *object,
1053                                                          int event)
1054 {
1055         _enter("{OBJ%x},%d", object->debug_id, event);
1056
1057         fscache_update_aux_data(object);
1058
1059         _leave("");
1060         return transit_to(WAIT_FOR_CMD);
1061 }
1062
1063 /**
1064  * fscache_object_retrying_stale - Note retrying stale object
1065  * @object: The object that will be retried
1066  *
1067  * Note that an object lookup found an on-disk object that was adjudged to be
1068  * stale and has been deleted.  The lookup will be retried.
1069  */
1070 void fscache_object_retrying_stale(struct fscache_object *object)
1071 {
1072         fscache_stat(&fscache_n_cache_no_space_reject);
1073 }
1074 EXPORT_SYMBOL(fscache_object_retrying_stale);
1075
1076 /**
1077  * fscache_object_mark_killed - Note that an object was killed
1078  * @object: The object that was culled
1079  * @why: The reason the object was killed.
1080  *
1081  * Note that an object was killed.  Returns true if the object was
1082  * already marked killed, false if it wasn't.
1083  */
1084 void fscache_object_mark_killed(struct fscache_object *object,
1085                                 enum fscache_why_object_killed why)
1086 {
1087         if (test_and_set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags)) {
1088                 pr_err("Error: Object already killed by cache [%s]\n",
1089                        object->cache->identifier);
1090                 return;
1091         }
1092
1093         switch (why) {
1094         case FSCACHE_OBJECT_NO_SPACE:
1095                 fscache_stat(&fscache_n_cache_no_space_reject);
1096                 break;
1097         case FSCACHE_OBJECT_IS_STALE:
1098                 fscache_stat(&fscache_n_cache_stale_objects);
1099                 break;
1100         case FSCACHE_OBJECT_WAS_RETIRED:
1101                 fscache_stat(&fscache_n_cache_retired_objects);
1102                 break;
1103         case FSCACHE_OBJECT_WAS_CULLED:
1104                 fscache_stat(&fscache_n_cache_culled_objects);
1105                 break;
1106         }
1107 }
1108 EXPORT_SYMBOL(fscache_object_mark_killed);
1109
1110 /*
1111  * The object is dead.  We can get here if an object gets queued by an event
1112  * that would lead to its death (such as EV_KILL) when the dispatcher is
1113  * already running (and so can be requeued) but hasn't yet cleared the event
1114  * mask.
1115  */
1116 static const struct fscache_state *fscache_object_dead(struct fscache_object *object,
1117                                                        int event)
1118 {
1119         if (!test_and_set_bit(FSCACHE_OBJECT_RUN_AFTER_DEAD,
1120                               &object->flags))
1121                 return NO_TRANSIT;
1122
1123         WARN(true, "FS-Cache object redispatched after death");
1124         return NO_TRANSIT;
1125 }