fs/fscache/object.c

   1 /* FS-Cache object state machine handler
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  *
  11  * See Documentation/filesystems/caching/object.txt for a description of the
  12  * object state machine and the in-kernel representations.
  13  */
  14
  15 #define FSCACHE_DEBUG_LEVEL COOKIE
  16 #include <linux/module.h>
  17 #include <linux/slab.h>
  18 #include "internal.h"
  19
  20 const char *fscache_object_states[FSCACHE_OBJECT__NSTATES] = {
  21         [FSCACHE_OBJECT_INIT]           = "OBJECT_INIT",
  22         [FSCACHE_OBJECT_LOOKING_UP]     = "OBJECT_LOOKING_UP",
  23         [FSCACHE_OBJECT_CREATING]       = "OBJECT_CREATING",
  24         [FSCACHE_OBJECT_AVAILABLE]      = "OBJECT_AVAILABLE",
  25         [FSCACHE_OBJECT_ACTIVE]         = "OBJECT_ACTIVE",
  26         [FSCACHE_OBJECT_INVALIDATING]   = "OBJECT_INVALIDATING",
  27         [FSCACHE_OBJECT_UPDATING]       = "OBJECT_UPDATING",
  28         [FSCACHE_OBJECT_DYING]          = "OBJECT_DYING",
  29         [FSCACHE_OBJECT_LC_DYING]       = "OBJECT_LC_DYING",
  30         [FSCACHE_OBJECT_ABORT_INIT]     = "OBJECT_ABORT_INIT",
  31         [FSCACHE_OBJECT_RELEASING]      = "OBJECT_RELEASING",
  32         [FSCACHE_OBJECT_RECYCLING]      = "OBJECT_RECYCLING",
  33         [FSCACHE_OBJECT_WITHDRAWING]    = "OBJECT_WITHDRAWING",
  34         [FSCACHE_OBJECT_DEAD]           = "OBJECT_DEAD",
  35 };
  36 EXPORT_SYMBOL(fscache_object_states);
  37
  38 const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5] = {
  39         [FSCACHE_OBJECT_INIT]           = "INIT",
  40         [FSCACHE_OBJECT_LOOKING_UP]     = "LOOK",
  41         [FSCACHE_OBJECT_CREATING]       = "CRTN",
  42         [FSCACHE_OBJECT_AVAILABLE]      = "AVBL",
  43         [FSCACHE_OBJECT_ACTIVE]         = "ACTV",
  44         [FSCACHE_OBJECT_INVALIDATING]   = "INVL",
  45         [FSCACHE_OBJECT_UPDATING]       = "UPDT",
  46         [FSCACHE_OBJECT_DYING]          = "DYNG",
  47         [FSCACHE_OBJECT_LC_DYING]       = "LCDY",
  48         [FSCACHE_OBJECT_ABORT_INIT]     = "ABTI",
  49         [FSCACHE_OBJECT_RELEASING]      = "RELS",
  50         [FSCACHE_OBJECT_RECYCLING]      = "RCYC",
  51         [FSCACHE_OBJECT_WITHDRAWING]    = "WTHD",
  52         [FSCACHE_OBJECT_DEAD]           = "DEAD",
  53 };
  54
  55 static int  fscache_get_object(struct fscache_object *);
  56 static void fscache_put_object(struct fscache_object *);
  57 static void fscache_initialise_object(struct fscache_object *);
  58 static void fscache_lookup_object(struct fscache_object *);
  59 static void fscache_object_available(struct fscache_object *);
  60 static void fscache_invalidate_object(struct fscache_object *);
  61 static void fscache_release_object(struct fscache_object *);
  62 static void fscache_withdraw_object(struct fscache_object *);
  63 static void fscache_enqueue_dependents(struct fscache_object *);
  64 static void fscache_dequeue_object(struct fscache_object *);
  65
  66 /*
  67  * we need to notify the parent when an op completes that we had outstanding
  68  * upon it
  69  */
  70 static inline void fscache_done_parent_op(struct fscache_object *object)
  71 {
  72         struct fscache_object *parent = object->parent;
  73
  74         _enter("OBJ%x {OBJ%x,%x}",
  75                object->debug_id, parent->debug_id, parent->n_ops);
  76
  77         spin_lock_nested(&parent->lock, 1);
  78         parent->n_ops--;
  79         parent->n_obj_ops--;
  80         if (parent->n_ops == 0)
  81                 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
  82         spin_unlock(&parent->lock);
  83 }
  84
  85 /*
  86  * Notify netfs of invalidation completion.
  87  */
  88 static inline void fscache_invalidation_complete(struct fscache_cookie *cookie)
  89 {
  90         if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
  91                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
  92 }
  93
  94 /*
  95  * process events that have been sent to an object's state machine
  96  * - initiates parent lookup
  97  * - does object lookup
  98  * - does object creation
  99  * - does object recycling and retirement
 100  * - does object withdrawal
 101  */
 102 static void fscache_object_state_machine(struct fscache_object *object)
 103 {
 104         enum fscache_object_state new_state;
 105         struct fscache_cookie *cookie;
 106
 107         ASSERT(object != NULL);
 108
 109         _enter("{OBJ%x,%s,%lx}",
 110                object->debug_id, fscache_object_states[object->state],
 111                object->events);
 112
 113         switch (object->state) {
 114                 /* wait for the parent object to become ready */
 115         case FSCACHE_OBJECT_INIT:
 116                 object->event_mask =
 117                         FSCACHE_OBJECT_EVENTS_MASK &
 118                         ~(1 << FSCACHE_OBJECT_EV_CLEARED);
 119                 fscache_initialise_object(object);
 120                 goto done;
 121
 122                 /* look up the object metadata on disk */
 123         case FSCACHE_OBJECT_LOOKING_UP:
 124                 fscache_lookup_object(object);
 125                 goto lookup_transit;
 126
 127                 /* create the object metadata on disk */
 128         case FSCACHE_OBJECT_CREATING:
 129                 fscache_lookup_object(object);
 130                 goto lookup_transit;
 131
 132                 /* handle an object becoming available; start pending
 133                  * operations and queue dependent operations for processing */
 134         case FSCACHE_OBJECT_AVAILABLE:
 135                 fscache_object_available(object);
 136                 goto active_transit;
 137
 138                 /* normal running state */
 139         case FSCACHE_OBJECT_ACTIVE:
 140                 goto active_transit;
 141
 142                 /* Invalidate an object on disk */
 143         case FSCACHE_OBJECT_INVALIDATING:
 144                 clear_bit(FSCACHE_OBJECT_EV_INVALIDATE, &object->events);
 145                 fscache_stat(&fscache_n_invalidates_run);
 146                 fscache_stat(&fscache_n_cop_invalidate_object);
 147                 fscache_invalidate_object(object);
 148                 fscache_stat_d(&fscache_n_cop_invalidate_object);
 149                 fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE);
 150                 goto active_transit;
 151
 152                 /* update the object metadata on disk */
 153         case FSCACHE_OBJECT_UPDATING:
 154                 clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
 155                 fscache_stat(&fscache_n_updates_run);
 156                 fscache_stat(&fscache_n_cop_update_object);
 157                 object->cache->ops->update_object(object);
 158                 fscache_stat_d(&fscache_n_cop_update_object);
 159                 goto active_transit;
 160
 161                 /* handle an object dying during lookup or creation */
 162         case FSCACHE_OBJECT_LC_DYING:
 163                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 164                 fscache_stat(&fscache_n_cop_lookup_complete);
 165                 object->cache->ops->lookup_complete(object);
 166                 fscache_stat_d(&fscache_n_cop_lookup_complete);
 167
 168                 spin_lock(&object->lock);
 169                 object->state = FSCACHE_OBJECT_DYING;
 170                 cookie = object->cookie;
 171                 if (cookie) {
 172                         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP,
 173                                                &cookie->flags))
 174                                 wake_up_bit(&cookie->flags,
 175                                             FSCACHE_COOKIE_LOOKING_UP);
 176                         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 177                                                &cookie->flags))
 178                                 wake_up_bit(&cookie->flags,
 179                                             FSCACHE_COOKIE_CREATING);
 180                 }
 181                 spin_unlock(&object->lock);
 182
 183                 fscache_done_parent_op(object);
 184
 185                 /* wait for completion of all active operations on this object
 186                  * and the death of all child objects of this object */
 187         case FSCACHE_OBJECT_DYING:
 188         dying:
 189                 clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
 190                 spin_lock(&object->lock);
 191                 _debug("dying OBJ%x {%d,%d}",
 192                        object->debug_id, object->n_ops, object->n_children);
 193                 if (object->n_ops == 0 && object->n_children == 0) {
 194                         object->event_mask &=
 195                                 ~(1 << FSCACHE_OBJECT_EV_CLEARED);
 196                         object->event_mask |=
 197                                 (1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 198                                 (1 << FSCACHE_OBJECT_EV_RETIRE) |
 199                                 (1 << FSCACHE_OBJECT_EV_RELEASE) |
 200                                 (1 << FSCACHE_OBJECT_EV_ERROR);
 201                 } else {
 202                         object->event_mask &=
 203                                 ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 204                                   (1 << FSCACHE_OBJECT_EV_RETIRE) |
 205                                   (1 << FSCACHE_OBJECT_EV_RELEASE) |
 206                                   (1 << FSCACHE_OBJECT_EV_ERROR));
 207                         object->event_mask |=
 208                                 1 << FSCACHE_OBJECT_EV_CLEARED;
 209                 }
 210                 spin_unlock(&object->lock);
 211                 fscache_enqueue_dependents(object);
 212                 fscache_start_operations(object);
 213                 goto terminal_transit;
 214
 215                 /* handle an abort during initialisation */
 216         case FSCACHE_OBJECT_ABORT_INIT:
 217                 _debug("handle abort init %lx", object->events);
 218                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 219
 220                 spin_lock(&object->lock);
 221                 fscache_dequeue_object(object);
 222
 223                 object->state = FSCACHE_OBJECT_DYING;
 224                 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 225                                        &object->cookie->flags))
 226                         wake_up_bit(&object->cookie->flags,
 227                                     FSCACHE_COOKIE_CREATING);
 228                 spin_unlock(&object->lock);
 229                 goto dying;
 230
 231                 /* handle the netfs releasing an object and possibly marking it
 232                  * obsolete too */
 233         case FSCACHE_OBJECT_RELEASING:
 234         case FSCACHE_OBJECT_RECYCLING:
 235                 object->event_mask &=
 236                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 237                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 238                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 239                           (1 << FSCACHE_OBJECT_EV_ERROR));
 240                 fscache_release_object(object);
 241                 spin_lock(&object->lock);
 242                 object->state = FSCACHE_OBJECT_DEAD;
 243                 spin_unlock(&object->lock);
 244                 fscache_stat(&fscache_n_object_dead);
 245                 goto terminal_transit;
 246
 247                 /* handle the parent cache of this object being withdrawn from
 248                  * active service */
 249         case FSCACHE_OBJECT_WITHDRAWING:
 250                 object->event_mask &=
 251                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 252                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 253                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 254                           (1 << FSCACHE_OBJECT_EV_ERROR));
 255                 fscache_withdraw_object(object);
 256                 spin_lock(&object->lock);
 257                 object->state = FSCACHE_OBJECT_DEAD;
 258                 spin_unlock(&object->lock);
 259                 fscache_stat(&fscache_n_object_dead);
 260                 goto terminal_transit;
 261
 262                 /* complain about the object being woken up once it is
 263                  * deceased */
 264         case FSCACHE_OBJECT_DEAD:
 265                 printk(KERN_ERR "FS-Cache:"
 266                        " Unexpected event in dead state %lx\n",
 267                        object->events & object->event_mask);
 268                 BUG();
 269
 270         default:
 271                 printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
 272                        object->state);
 273                 BUG();
 274         }
 275
 276         /* determine the transition from a lookup state */
 277 lookup_transit:
 278         switch (fls(object->events & object->event_mask) - 1) {
 279         case FSCACHE_OBJECT_EV_WITHDRAW:
 280         case FSCACHE_OBJECT_EV_RETIRE:
 281         case FSCACHE_OBJECT_EV_RELEASE:
 282         case FSCACHE_OBJECT_EV_ERROR:
 283                 new_state = FSCACHE_OBJECT_LC_DYING;
 284                 goto change_state;
 285         case FSCACHE_OBJECT_EV_REQUEUE:
 286                 goto done;
 287         case -1:
 288                 goto done; /* sleep until event */
 289         default:
 290                 goto unsupported_event;
 291         }
 292
 293         /* determine the transition from an active state */
 294 active_transit:
 295         switch (fls(object->events & object->event_mask) - 1) {
 296         case FSCACHE_OBJECT_EV_WITHDRAW:
 297         case FSCACHE_OBJECT_EV_RETIRE:
 298         case FSCACHE_OBJECT_EV_RELEASE:
 299         case FSCACHE_OBJECT_EV_ERROR:
 300                 new_state = FSCACHE_OBJECT_DYING;
 301                 goto change_state;
 302         case FSCACHE_OBJECT_EV_INVALIDATE:
 303                 new_state = FSCACHE_OBJECT_INVALIDATING;
 304                 goto change_state;
 305         case FSCACHE_OBJECT_EV_UPDATE:
 306                 new_state = FSCACHE_OBJECT_UPDATING;
 307                 goto change_state;
 308         case -1:
 309                 new_state = FSCACHE_OBJECT_ACTIVE;
 310                 goto change_state; /* sleep until event */
 311         default:
 312                 goto unsupported_event;
 313         }
 314
 315         /* determine the transition from a terminal state */
 316 terminal_transit:
 317         switch (fls(object->events & object->event_mask) - 1) {
 318         case FSCACHE_OBJECT_EV_WITHDRAW:
 319                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 320                 goto change_state;
 321         case FSCACHE_OBJECT_EV_RETIRE:
 322                 new_state = FSCACHE_OBJECT_RECYCLING;
 323                 goto change_state;
 324         case FSCACHE_OBJECT_EV_RELEASE:
 325                 new_state = FSCACHE_OBJECT_RELEASING;
 326                 goto change_state;
 327         case FSCACHE_OBJECT_EV_ERROR:
 328                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 329                 goto change_state;
 330         case FSCACHE_OBJECT_EV_CLEARED:
 331                 new_state = FSCACHE_OBJECT_DYING;
 332                 goto change_state;
 333         case -1:
 334                 goto done; /* sleep until event */
 335         default:
 336                 goto unsupported_event;
 337         }
 338
 339 change_state:
 340         spin_lock(&object->lock);
 341         object->state = new_state;
 342         spin_unlock(&object->lock);
 343
 344 done:
 345         _leave(" [->%s]", fscache_object_states[object->state]);
 346         return;
 347
 348 unsupported_event:
 349         printk(KERN_ERR "FS-Cache:"
 350                " Unsupported event %lx [mask %lx] in state %s\n",
 351                object->events, object->event_mask,
 352                fscache_object_states[object->state]);
 353         BUG();
 354 }
 355
 356 /*
 357  * execute an object
 358  */
 359 void fscache_object_work_func(struct work_struct *work)
 360 {
 361         struct fscache_object *object =
 362                 container_of(work, struct fscache_object, work);
 363         unsigned long start;
 364
 365         _enter("{OBJ%x}", object->debug_id);
 366
 367         start = jiffies;
 368         fscache_object_state_machine(object);
 369         fscache_hist(fscache_objs_histogram, start);
 370         if (object->events & object->event_mask)
 371                 fscache_enqueue_object(object);
 372         clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 373         fscache_put_object(object);
 374 }
 375 EXPORT_SYMBOL(fscache_object_work_func);
 376
 377 /*
 378  * initialise an object
 379  * - check the specified object's parent to see if we can make use of it
 380  *   immediately to do a creation
 381  * - we may need to start the process of creating a parent and we need to wait
 382  *   for the parent's lookup and creation to complete if it's not there yet
 383  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 384  *   leaf-most cookies of the object and all its children
 385  */
 386 static void fscache_initialise_object(struct fscache_object *object)
 387 {
 388         struct fscache_object *parent;
 389
 390         _enter("");
 391         ASSERT(object->cookie != NULL);
 392         ASSERT(object->cookie->parent != NULL);
 393
 394         if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
 395                               (1 << FSCACHE_OBJECT_EV_RELEASE) |
 396                               (1 << FSCACHE_OBJECT_EV_RETIRE) |
 397                               (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
 398                 _debug("abort init %lx", object->events);
 399                 spin_lock(&object->lock);
 400                 object->state = FSCACHE_OBJECT_ABORT_INIT;
 401                 spin_unlock(&object->lock);
 402                 return;
 403         }
 404
 405         spin_lock(&object->cookie->lock);
 406         spin_lock_nested(&object->cookie->parent->lock, 1);
 407
 408         parent = object->parent;
 409         if (!parent) {
 410                 _debug("no parent");
 411                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 412         } else {
 413                 spin_lock(&object->lock);
 414                 spin_lock_nested(&parent->lock, 1);
 415                 _debug("parent %s", fscache_object_states[parent->state]);
 416
 417                 if (parent->state >= FSCACHE_OBJECT_DYING) {
 418                         _debug("bad parent");
 419                         set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 420                 } else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
 421                         _debug("wait");
 422
 423                         /* we may get woken up in this state by child objects
 424                          * binding on to us, so we need to make sure we don't
 425                          * add ourself to the list multiple times */
 426                         if (list_empty(&object->dep_link)) {
 427                                 fscache_stat(&fscache_n_cop_grab_object);
 428                                 object->cache->ops->grab_object(object);
 429                                 fscache_stat_d(&fscache_n_cop_grab_object);
 430                                 list_add(&object->dep_link,
 431                                          &parent->dependents);
 432
 433                                 /* fscache_acquire_non_index_cookie() uses this
 434                                  * to wake the chain up */
 435                                 if (parent->state == FSCACHE_OBJECT_INIT)
 436                                         fscache_enqueue_object(parent);
 437                         }
 438                 } else {
 439                         _debug("go");
 440                         parent->n_ops++;
 441                         parent->n_obj_ops++;
 442                         object->lookup_jif = jiffies;
 443                         object->state = FSCACHE_OBJECT_LOOKING_UP;
 444                         set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 445                 }
 446
 447                 spin_unlock(&parent->lock);
 448                 spin_unlock(&object->lock);
 449         }
 450
 451         spin_unlock(&object->cookie->parent->lock);
 452         spin_unlock(&object->cookie->lock);
 453         _leave("");
 454 }
 455
 456 /*
 457  * look an object up in the cache from which it was allocated
 458  * - we hold an "access lock" on the parent object, so the parent object cannot
 459  *   be withdrawn by either party till we've finished
 460  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 461  *   leaf-most cookies of the object and all its children
 462  */
 463 static void fscache_lookup_object(struct fscache_object *object)
 464 {
 465         struct fscache_cookie *cookie = object->cookie;
 466         struct fscache_object *parent;
 467         int ret;
 468
 469         _enter("");
 470
 471         parent = object->parent;
 472         ASSERT(parent != NULL);
 473         ASSERTCMP(parent->n_ops, >, 0);
 474         ASSERTCMP(parent->n_obj_ops, >, 0);
 475
 476         /* make sure the parent is still available */
 477         ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
 478
 479         if (parent->state >= FSCACHE_OBJECT_DYING ||
 480             test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 481                 _debug("unavailable");
 482                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 483                 _leave("");
 484                 return;
 485         }
 486
 487         _debug("LOOKUP \"%s/%s\" in \"%s\"",
 488                parent->cookie->def->name, cookie->def->name,
 489                object->cache->tag->name);
 490
 491         fscache_stat(&fscache_n_object_lookups);
 492         fscache_stat(&fscache_n_cop_lookup_object);
 493         ret = object->cache->ops->lookup_object(object);
 494         fscache_stat_d(&fscache_n_cop_lookup_object);
 495
 496         if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
 497                 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 498
 499         if (ret == -ETIMEDOUT) {
 500                 /* probably stuck behind another object, so move this one to
 501                  * the back of the queue */
 502                 fscache_stat(&fscache_n_object_lookups_timed_out);
 503                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 504         }
 505
 506         _leave("");
 507 }
 508
 509 /**
 510  * fscache_object_lookup_negative - Note negative cookie lookup
 511  * @object: Object pointing to cookie to mark
 512  *
 513  * Note negative lookup, permitting those waiting to read data from an already
 514  * existing backing object to continue as there's no data for them to read.
 515  */
 516 void fscache_object_lookup_negative(struct fscache_object *object)
 517 {
 518         struct fscache_cookie *cookie = object->cookie;
 519
 520         _enter("{OBJ%x,%s}",
 521                object->debug_id, fscache_object_states[object->state]);
 522
 523         spin_lock(&object->lock);
 524         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 525                 fscache_stat(&fscache_n_object_lookups_negative);
 526
 527                 /* transit here to allow write requests to begin stacking up
 528                  * and read requests to begin returning ENODATA */
 529                 object->state = FSCACHE_OBJECT_CREATING;
 530                 spin_unlock(&object->lock);
 531
 532                 set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
 533                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 534
 535                 _debug("wake up lookup %p", &cookie->flags);
 536                 smp_mb__before_clear_bit();
 537                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 538                 smp_mb__after_clear_bit();
 539                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 540                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 541         } else {
 542                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 543                 spin_unlock(&object->lock);
 544         }
 545
 546         _leave("");
 547 }
 548 EXPORT_SYMBOL(fscache_object_lookup_negative);
 549
 550 /**
 551  * fscache_obtained_object - Note successful object lookup or creation
 552  * @object: Object pointing to cookie to mark
 553  *
 554  * Note successful lookup and/or creation, permitting those waiting to write
 555  * data to a backing object to continue.
 556  *
 557  * Note that after calling this, an object's cookie may be relinquished by the
 558  * netfs, and so must be accessed with object lock held.
 559  */
 560 void fscache_obtained_object(struct fscache_object *object)
 561 {
 562         struct fscache_cookie *cookie = object->cookie;
 563
 564         _enter("{OBJ%x,%s}",
 565                object->debug_id, fscache_object_states[object->state]);
 566
 567         /* if we were still looking up, then we must have a positive lookup
 568          * result, in which case there may be data available */
 569         spin_lock(&object->lock);
 570         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 571                 fscache_stat(&fscache_n_object_lookups_positive);
 572
 573                 clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 574
 575                 object->state = FSCACHE_OBJECT_AVAILABLE;
 576                 spin_unlock(&object->lock);
 577
 578                 smp_mb__before_clear_bit();
 579                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 580                 smp_mb__after_clear_bit();
 581                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 582                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 583         } else {
 584                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 585                 fscache_stat(&fscache_n_object_created);
 586
 587                 object->state = FSCACHE_OBJECT_AVAILABLE;
 588                 spin_unlock(&object->lock);
 589                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 590                 smp_wmb();
 591         }
 592
 593         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
 594                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 595
 596         _leave("");
 597 }
 598 EXPORT_SYMBOL(fscache_obtained_object);
 599
 600 /*
 601  * handle an object that has just become available
 602  */
 603 static void fscache_object_available(struct fscache_object *object)
 604 {
 605         _enter("{OBJ%x}", object->debug_id);
 606
 607         spin_lock(&object->lock);
 608
 609         if (object->cookie &&
 610             test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
 611                 wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
 612
 613         fscache_done_parent_op(object);
 614         if (object->n_in_progress == 0) {
 615                 if (object->n_ops > 0) {
 616                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 617                         fscache_start_operations(object);
 618                 } else {
 619                         ASSERT(list_empty(&object->pending_ops));
 620                 }
 621         }
 622         spin_unlock(&object->lock);
 623
 624         fscache_stat(&fscache_n_cop_lookup_complete);
 625         object->cache->ops->lookup_complete(object);
 626         fscache_stat_d(&fscache_n_cop_lookup_complete);
 627         fscache_enqueue_dependents(object);
 628
 629         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 630         fscache_stat(&fscache_n_object_avail);
 631
 632         _leave("");
 633 }
 634
 635 /*
 636  * drop an object's attachments
 637  */
 638 static void fscache_drop_object(struct fscache_object *object)
 639 {
 640         struct fscache_object *parent = object->parent;
 641         struct fscache_cache *cache = object->cache;
 642
 643         _enter("{OBJ%x,%d}", object->debug_id, object->n_children);
 644
 645         ASSERTCMP(object->cookie, ==, NULL);
 646         ASSERT(hlist_unhashed(&object->cookie_link));
 647
 648         spin_lock(&cache->object_list_lock);
 649         list_del_init(&object->cache_link);
 650         spin_unlock(&cache->object_list_lock);
 651
 652         fscache_stat(&fscache_n_cop_drop_object);
 653         cache->ops->drop_object(object);
 654         fscache_stat_d(&fscache_n_cop_drop_object);
 655
 656         if (parent) {
 657                 _debug("release parent OBJ%x {%d}",
 658                        parent->debug_id, parent->n_children);
 659
 660                 spin_lock(&parent->lock);
 661                 parent->n_children--;
 662                 if (parent->n_children == 0)
 663                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 664                 spin_unlock(&parent->lock);
 665                 object->parent = NULL;
 666         }
 667
 668         /* this just shifts the object release to the work processor */
 669         fscache_put_object(object);
 670
 671         _leave("");
 672 }
 673
 674 /*
 675  * release or recycle an object that the netfs has discarded
 676  */
 677 static void fscache_release_object(struct fscache_object *object)
 678 {
 679         _enter("");
 680
 681         fscache_drop_object(object);
 682 }
 683
 684 /*
 685  * withdraw an object from active service
 686  */
 687 static void fscache_withdraw_object(struct fscache_object *object)
 688 {
 689         struct fscache_cookie *cookie;
 690         bool detached;
 691
 692         _enter("");
 693
 694         spin_lock(&object->lock);
 695         cookie = object->cookie;
 696         if (cookie) {
 697                 /* need to get the cookie lock before the object lock, starting
 698                  * from the object pointer */
 699                 atomic_inc(&cookie->usage);
 700                 spin_unlock(&object->lock);
 701
 702                 detached = false;
 703                 spin_lock(&cookie->lock);
 704                 spin_lock(&object->lock);
 705
 706                 if (object->cookie == cookie) {
 707                         hlist_del_init(&object->cookie_link);
 708                         object->cookie = NULL;
 709                         fscache_invalidation_complete(cookie);
 710                         detached = true;
 711                 }
 712                 spin_unlock(&cookie->lock);
 713                 fscache_cookie_put(cookie);
 714                 if (detached)
 715                         fscache_cookie_put(cookie);
 716         }
 717
 718         spin_unlock(&object->lock);
 719
 720         fscache_drop_object(object);
 721 }
 722
 723 /*
 724  * withdraw an object from active service at the behest of the cache
 725  * - need break the links to a cached object cookie
 726  * - called under two situations:
 727  *   (1) recycler decides to reclaim an in-use object
 728  *   (2) a cache is unmounted
 729  * - have to take care as the cookie can be being relinquished by the netfs
 730  *   simultaneously
 731  * - the object is pinned by the caller holding a refcount on it
 732  */
 733 void fscache_withdrawing_object(struct fscache_cache *cache,
 734                                 struct fscache_object *object)
 735 {
 736         bool enqueue = false;
 737
 738         _enter(",OBJ%x", object->debug_id);
 739
 740         spin_lock(&object->lock);
 741         if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
 742                 object->state = FSCACHE_OBJECT_WITHDRAWING;
 743                 enqueue = true;
 744         }
 745         spin_unlock(&object->lock);
 746
 747         if (enqueue)
 748                 fscache_enqueue_object(object);
 749
 750         _leave("");
 751 }
 752
 753 /*
 754  * get a ref on an object
 755  */
 756 static int fscache_get_object(struct fscache_object *object)
 757 {
 758         int ret;
 759
 760         fscache_stat(&fscache_n_cop_grab_object);
 761         ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 762         fscache_stat_d(&fscache_n_cop_grab_object);
 763         return ret;
 764 }
 765
 766 /*
 767  * discard a ref on a work item
 768  */
 769 static void fscache_put_object(struct fscache_object *object)
 770 {
 771         fscache_stat(&fscache_n_cop_put_object);
 772         object->cache->ops->put_object(object);
 773         fscache_stat_d(&fscache_n_cop_put_object);
 774 }
 775
 776 /*
 777  * enqueue an object for metadata-type processing
 778  */
 779 void fscache_enqueue_object(struct fscache_object *object)
 780 {
 781         _enter("{OBJ%x}", object->debug_id);
 782
 783         if (fscache_get_object(object) >= 0) {
 784                 wait_queue_head_t *cong_wq =
 785                         &get_cpu_var(fscache_object_cong_wait);
 786
 787                 if (queue_work(fscache_object_wq, &object->work)) {
 788                         if (fscache_object_congested())
 789                                 wake_up(cong_wq);
 790                 } else
 791                         fscache_put_object(object);
 792
 793                 put_cpu_var(fscache_object_cong_wait);
 794         }
 795 }
 796
 797 /**
 798  * fscache_object_sleep_till_congested - Sleep until object wq is congested
 799  * @timoutp: Scheduler sleep timeout
 800  *
 801  * Allow an object handler to sleep until the object workqueue is congested.
 802  *
 803  * The caller must set up a wake up event before calling this and must have set
 804  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 805  * condition before calling this function as no test is made here.
 806  *
 807  * %true is returned if the object wq is congested, %false otherwise.
 808  */
 809 bool fscache_object_sleep_till_congested(signed long *timeoutp)
 810 {
 811         wait_queue_head_t *cong_wq = &__get_cpu_var(fscache_object_cong_wait);
 812         DEFINE_WAIT(wait);
 813
 814         if (fscache_object_congested())
 815                 return true;
 816
 817         add_wait_queue_exclusive(cong_wq, &wait);
 818         if (!fscache_object_congested())
 819                 *timeoutp = schedule_timeout(*timeoutp);
 820         finish_wait(cong_wq, &wait);
 821
 822         return fscache_object_congested();
 823 }
 824 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 825
 826 /*
 827  * enqueue the dependents of an object for metadata-type processing
 828  * - the caller must hold the object's lock
 829  * - this may cause an already locked object to wind up being processed again
 830  */
 831 static void fscache_enqueue_dependents(struct fscache_object *object)
 832 {
 833         struct fscache_object *dep;
 834
 835         _enter("{OBJ%x}", object->debug_id);
 836
 837         if (list_empty(&object->dependents))
 838                 return;
 839
 840         spin_lock(&object->lock);
 841
 842         while (!list_empty(&object->dependents)) {
 843                 dep = list_entry(object->dependents.next,
 844                                  struct fscache_object, dep_link);
 845                 list_del_init(&dep->dep_link);
 846
 847
 848                 /* sort onto appropriate lists */
 849                 fscache_enqueue_object(dep);
 850                 fscache_put_object(dep);
 851
 852                 if (!list_empty(&object->dependents))
 853                         cond_resched_lock(&object->lock);
 854         }
 855
 856         spin_unlock(&object->lock);
 857 }
 858
 859 /*
 860  * remove an object from whatever queue it's waiting on
 861  * - the caller must hold object->lock
 862  */
 863 void fscache_dequeue_object(struct fscache_object *object)
 864 {
 865         _enter("{OBJ%x}", object->debug_id);
 866
 867         if (!list_empty(&object->dep_link)) {
 868                 spin_lock(&object->parent->lock);
 869                 list_del_init(&object->dep_link);
 870                 spin_unlock(&object->parent->lock);
 871         }
 872
 873         _leave("");
 874 }
 875
 876 /**
 877  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 878  * @object: The object to ask about
 879  * @data: The auxiliary data for the object
 880  * @datalen: The size of the auxiliary data
 881  *
 882  * This function consults the netfs about the coherency state of an object
 883  */
 884 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 885                                         const void *data, uint16_t datalen)
 886 {
 887         enum fscache_checkaux result;
 888
 889         if (!object->cookie->def->check_aux) {
 890                 fscache_stat(&fscache_n_checkaux_none);
 891                 return FSCACHE_CHECKAUX_OKAY;
 892         }
 893
 894         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 895                                                 data, datalen);
 896         switch (result) {
 897                 /* entry okay as is */
 898         case FSCACHE_CHECKAUX_OKAY:
 899                 fscache_stat(&fscache_n_checkaux_okay);
 900                 break;
 901
 902                 /* entry requires update */
 903         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 904                 fscache_stat(&fscache_n_checkaux_update);
 905                 break;
 906
 907                 /* entry requires deletion */
 908         case FSCACHE_CHECKAUX_OBSOLETE:
 909                 fscache_stat(&fscache_n_checkaux_obsolete);
 910                 break;
 911
 912         default:
 913                 BUG();
 914         }
 915
 916         return result;
 917 }
 918 EXPORT_SYMBOL(fscache_check_aux);
 919
 920 /*
 921  * Asynchronously invalidate an object.
 922  */
 923 static void fscache_invalidate_object(struct fscache_object *object)
 924 {
 925         struct fscache_operation *op;
 926         struct fscache_cookie *cookie = object->cookie;
 927
 928         _enter("{OBJ%x}", object->debug_id);
 929
 930         /* Reject any new read/write ops and abort any that are pending. */
 931         fscache_invalidate_writes(cookie);
 932         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 933         fscache_cancel_all_ops(object);
 934
 935         /* Now we have to wait for in-progress reads and writes */
 936         op = kzalloc(sizeof(*op), GFP_KERNEL);
 937         if (!op) {
 938                 fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
 939                 _leave(" [ENOMEM]");
 940                 return;
 941         }
 942
 943         fscache_operation_init(op, object->cache->ops->invalidate_object, NULL);
 944         op->flags = FSCACHE_OP_ASYNC | (1 << FSCACHE_OP_EXCLUSIVE);
 945
 946         spin_lock(&cookie->lock);
 947         if (fscache_submit_exclusive_op(object, op) < 0)
 948                 BUG();
 949         spin_unlock(&cookie->lock);
 950         fscache_put_operation(op);
 951
 952         /* Once we've completed the invalidation, we know there will be no data
 953          * stored in the cache and thus we can reinstate the data-check-skip
 954          * optimisation.
 955          */
 956         set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 957
 958         /* We can allow read and write requests to come in once again.  They'll
 959          * queue up behind our exclusive invalidation operation.
 960          */
 961         fscache_invalidation_complete(cookie);
 962         _leave("");
 963 }