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         int event;
 107
 108         ASSERT(object != NULL);
 109
 110         _enter("{OBJ%x,%s,%lx}",
 111                object->debug_id, fscache_object_states[object->state],
 112                object->events);
 113
 114         switch (object->state) {
 115                 /* wait for the parent object to become ready */
 116         case FSCACHE_OBJECT_INIT:
 117                 object->event_mask =
 118                         FSCACHE_OBJECT_EVENTS_MASK &
 119                         ~(1 << FSCACHE_OBJECT_EV_CLEARED);
 120                 fscache_initialise_object(object);
 121                 goto done;
 122
 123                 /* look up the object metadata on disk */
 124         case FSCACHE_OBJECT_LOOKING_UP:
 125                 fscache_lookup_object(object);
 126                 goto lookup_transit;
 127
 128                 /* create the object metadata on disk */
 129         case FSCACHE_OBJECT_CREATING:
 130                 fscache_lookup_object(object);
 131                 goto lookup_transit;
 132
 133                 /* handle an object becoming available; start pending
 134                  * operations and queue dependent operations for processing */
 135         case FSCACHE_OBJECT_AVAILABLE:
 136                 fscache_object_available(object);
 137                 goto active_transit;
 138
 139                 /* normal running state */
 140         case FSCACHE_OBJECT_ACTIVE:
 141                 goto active_transit;
 142
 143                 /* Invalidate an object on disk */
 144         case FSCACHE_OBJECT_INVALIDATING:
 145                 clear_bit(FSCACHE_OBJECT_EV_INVALIDATE, &object->events);
 146                 fscache_stat(&fscache_n_invalidates_run);
 147                 fscache_stat(&fscache_n_cop_invalidate_object);
 148                 fscache_invalidate_object(object);
 149                 fscache_stat_d(&fscache_n_cop_invalidate_object);
 150                 fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE);
 151                 goto active_transit;
 152
 153                 /* update the object metadata on disk */
 154         case FSCACHE_OBJECT_UPDATING:
 155                 clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
 156                 fscache_stat(&fscache_n_updates_run);
 157                 fscache_stat(&fscache_n_cop_update_object);
 158                 object->cache->ops->update_object(object);
 159                 fscache_stat_d(&fscache_n_cop_update_object);
 160                 goto active_transit;
 161
 162                 /* handle an object dying during lookup or creation */
 163         case FSCACHE_OBJECT_LC_DYING:
 164                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 165                 fscache_stat(&fscache_n_cop_lookup_complete);
 166                 object->cache->ops->lookup_complete(object);
 167                 fscache_stat_d(&fscache_n_cop_lookup_complete);
 168
 169                 spin_lock(&object->lock);
 170                 object->state = FSCACHE_OBJECT_DYING;
 171                 cookie = object->cookie;
 172                 if (cookie) {
 173                         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP,
 174                                                &cookie->flags))
 175                                 wake_up_bit(&cookie->flags,
 176                                             FSCACHE_COOKIE_LOOKING_UP);
 177                         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 178                                                &cookie->flags))
 179                                 wake_up_bit(&cookie->flags,
 180                                             FSCACHE_COOKIE_CREATING);
 181                 }
 182                 spin_unlock(&object->lock);
 183
 184                 fscache_done_parent_op(object);
 185
 186                 /* wait for completion of all active operations on this object
 187                  * and the death of all child objects of this object */
 188         case FSCACHE_OBJECT_DYING:
 189         dying:
 190                 clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
 191                 spin_lock(&object->lock);
 192                 _debug("dying OBJ%x {%d,%d}",
 193                        object->debug_id, object->n_ops, object->n_children);
 194                 if (object->n_ops == 0 && object->n_children == 0) {
 195                         object->event_mask &=
 196                                 ~(1 << FSCACHE_OBJECT_EV_CLEARED);
 197                         object->event_mask |=
 198                                 (1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 199                                 (1 << FSCACHE_OBJECT_EV_RETIRE) |
 200                                 (1 << FSCACHE_OBJECT_EV_RELEASE) |
 201                                 (1 << FSCACHE_OBJECT_EV_ERROR);
 202                 } else {
 203                         object->event_mask &=
 204                                 ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 205                                   (1 << FSCACHE_OBJECT_EV_RETIRE) |
 206                                   (1 << FSCACHE_OBJECT_EV_RELEASE) |
 207                                   (1 << FSCACHE_OBJECT_EV_ERROR));
 208                         object->event_mask |=
 209                                 1 << FSCACHE_OBJECT_EV_CLEARED;
 210                 }
 211                 spin_unlock(&object->lock);
 212                 fscache_enqueue_dependents(object);
 213                 fscache_start_operations(object);
 214                 goto terminal_transit;
 215
 216                 /* handle an abort during initialisation */
 217         case FSCACHE_OBJECT_ABORT_INIT:
 218                 _debug("handle abort init %lx", object->events);
 219                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 220
 221                 spin_lock(&object->lock);
 222                 fscache_dequeue_object(object);
 223
 224                 object->state = FSCACHE_OBJECT_DYING;
 225                 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 226                                        &object->cookie->flags))
 227                         wake_up_bit(&object->cookie->flags,
 228                                     FSCACHE_COOKIE_CREATING);
 229                 spin_unlock(&object->lock);
 230                 goto dying;
 231
 232                 /* handle the netfs releasing an object and possibly marking it
 233                  * obsolete too */
 234         case FSCACHE_OBJECT_RELEASING:
 235         case FSCACHE_OBJECT_RECYCLING:
 236                 object->event_mask &=
 237                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 238                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 239                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 240                           (1 << FSCACHE_OBJECT_EV_ERROR));
 241                 fscache_release_object(object);
 242                 spin_lock(&object->lock);
 243                 object->state = FSCACHE_OBJECT_DEAD;
 244                 spin_unlock(&object->lock);
 245                 fscache_stat(&fscache_n_object_dead);
 246                 goto terminal_transit;
 247
 248                 /* handle the parent cache of this object being withdrawn from
 249                  * active service */
 250         case FSCACHE_OBJECT_WITHDRAWING:
 251                 object->event_mask &=
 252                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 253                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 254                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 255                           (1 << FSCACHE_OBJECT_EV_ERROR));
 256                 fscache_withdraw_object(object);
 257                 spin_lock(&object->lock);
 258                 object->state = FSCACHE_OBJECT_DEAD;
 259                 spin_unlock(&object->lock);
 260                 fscache_stat(&fscache_n_object_dead);
 261                 goto terminal_transit;
 262
 263                 /* complain about the object being woken up once it is
 264                  * deceased */
 265         case FSCACHE_OBJECT_DEAD:
 266                 printk(KERN_ERR "FS-Cache:"
 267                        " Unexpected event in dead state %lx\n",
 268                        object->events & object->event_mask);
 269                 BUG();
 270
 271         default:
 272                 printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
 273                        object->state);
 274                 BUG();
 275         }
 276
 277         /* determine the transition from a lookup state */
 278 lookup_transit:
 279         event = fls(object->events & object->event_mask) - 1;
 280         switch (event) {
 281         case FSCACHE_OBJECT_EV_WITHDRAW:
 282         case FSCACHE_OBJECT_EV_RETIRE:
 283         case FSCACHE_OBJECT_EV_RELEASE:
 284         case FSCACHE_OBJECT_EV_ERROR:
 285                 new_state = FSCACHE_OBJECT_LC_DYING;
 286                 goto change_state;
 287         case FSCACHE_OBJECT_EV_INVALIDATE:
 288                 new_state = FSCACHE_OBJECT_INVALIDATING;
 289                 goto change_state;
 290         case FSCACHE_OBJECT_EV_REQUEUE:
 291                 goto done;
 292         case -1:
 293                 goto done; /* sleep until event */
 294         default:
 295                 goto unsupported_event;
 296         }
 297
 298         /* determine the transition from an active state */
 299 active_transit:
 300         event = fls(object->events & object->event_mask) - 1;
 301         switch (event) {
 302         case FSCACHE_OBJECT_EV_WITHDRAW:
 303         case FSCACHE_OBJECT_EV_RETIRE:
 304         case FSCACHE_OBJECT_EV_RELEASE:
 305         case FSCACHE_OBJECT_EV_ERROR:
 306                 new_state = FSCACHE_OBJECT_DYING;
 307                 goto change_state;
 308         case FSCACHE_OBJECT_EV_INVALIDATE:
 309                 new_state = FSCACHE_OBJECT_INVALIDATING;
 310                 goto change_state;
 311         case FSCACHE_OBJECT_EV_UPDATE:
 312                 new_state = FSCACHE_OBJECT_UPDATING;
 313                 goto change_state;
 314         case -1:
 315                 new_state = FSCACHE_OBJECT_ACTIVE;
 316                 goto change_state; /* sleep until event */
 317         default:
 318                 goto unsupported_event;
 319         }
 320
 321         /* determine the transition from a terminal state */
 322 terminal_transit:
 323         event = fls(object->events & object->event_mask) - 1;
 324         switch (event) {
 325         case FSCACHE_OBJECT_EV_WITHDRAW:
 326                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 327                 goto change_state;
 328         case FSCACHE_OBJECT_EV_RETIRE:
 329                 new_state = FSCACHE_OBJECT_RECYCLING;
 330                 goto change_state;
 331         case FSCACHE_OBJECT_EV_RELEASE:
 332                 new_state = FSCACHE_OBJECT_RELEASING;
 333                 goto change_state;
 334         case FSCACHE_OBJECT_EV_ERROR:
 335                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 336                 goto change_state;
 337         case FSCACHE_OBJECT_EV_CLEARED:
 338                 new_state = FSCACHE_OBJECT_DYING;
 339                 goto change_state;
 340         case -1:
 341                 goto done; /* sleep until event */
 342         default:
 343                 goto unsupported_event;
 344         }
 345
 346 change_state:
 347         spin_lock(&object->lock);
 348         object->state = new_state;
 349         spin_unlock(&object->lock);
 350
 351 done:
 352         _leave(" [->%s]", fscache_object_states[object->state]);
 353         return;
 354
 355 unsupported_event:
 356         printk(KERN_ERR "FS-Cache:"
 357                " Unsupported event %d [%lx/%lx] in state %s\n",
 358                event, object->events, object->event_mask,
 359                fscache_object_states[object->state]);
 360         BUG();
 361 }
 362
 363 /*
 364  * execute an object
 365  */
 366 void fscache_object_work_func(struct work_struct *work)
 367 {
 368         struct fscache_object *object =
 369                 container_of(work, struct fscache_object, work);
 370         unsigned long start;
 371
 372         _enter("{OBJ%x}", object->debug_id);
 373
 374         start = jiffies;
 375         fscache_object_state_machine(object);
 376         fscache_hist(fscache_objs_histogram, start);
 377         if (object->events & object->event_mask)
 378                 fscache_enqueue_object(object);
 379         clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 380         fscache_put_object(object);
 381 }
 382 EXPORT_SYMBOL(fscache_object_work_func);
 383
 384 /*
 385  * initialise an object
 386  * - check the specified object's parent to see if we can make use of it
 387  *   immediately to do a creation
 388  * - we may need to start the process of creating a parent and we need to wait
 389  *   for the parent's lookup and creation to complete if it's not there yet
 390  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 391  *   leaf-most cookies of the object and all its children
 392  */
 393 static void fscache_initialise_object(struct fscache_object *object)
 394 {
 395         struct fscache_object *parent;
 396
 397         _enter("");
 398         ASSERT(object->cookie != NULL);
 399         ASSERT(object->cookie->parent != NULL);
 400
 401         if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
 402                               (1 << FSCACHE_OBJECT_EV_RELEASE) |
 403                               (1 << FSCACHE_OBJECT_EV_RETIRE) |
 404                               (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
 405                 _debug("abort init %lx", object->events);
 406                 spin_lock(&object->lock);
 407                 object->state = FSCACHE_OBJECT_ABORT_INIT;
 408                 spin_unlock(&object->lock);
 409                 return;
 410         }
 411
 412         spin_lock(&object->cookie->lock);
 413         spin_lock_nested(&object->cookie->parent->lock, 1);
 414
 415         parent = object->parent;
 416         if (!parent) {
 417                 _debug("no parent");
 418                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 419         } else {
 420                 spin_lock(&object->lock);
 421                 spin_lock_nested(&parent->lock, 1);
 422                 _debug("parent %s", fscache_object_states[parent->state]);
 423
 424                 if (parent->state >= FSCACHE_OBJECT_DYING) {
 425                         _debug("bad parent");
 426                         set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 427                 } else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
 428                         _debug("wait");
 429
 430                         /* we may get woken up in this state by child objects
 431                          * binding on to us, so we need to make sure we don't
 432                          * add ourself to the list multiple times */
 433                         if (list_empty(&object->dep_link)) {
 434                                 fscache_stat(&fscache_n_cop_grab_object);
 435                                 object->cache->ops->grab_object(object);
 436                                 fscache_stat_d(&fscache_n_cop_grab_object);
 437                                 list_add(&object->dep_link,
 438                                          &parent->dependents);
 439
 440                                 /* fscache_acquire_non_index_cookie() uses this
 441                                  * to wake the chain up */
 442                                 if (parent->state == FSCACHE_OBJECT_INIT)
 443                                         fscache_enqueue_object(parent);
 444                         }
 445                 } else {
 446                         _debug("go");
 447                         parent->n_ops++;
 448                         parent->n_obj_ops++;
 449                         object->lookup_jif = jiffies;
 450                         object->state = FSCACHE_OBJECT_LOOKING_UP;
 451                         set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 452                 }
 453
 454                 spin_unlock(&parent->lock);
 455                 spin_unlock(&object->lock);
 456         }
 457
 458         spin_unlock(&object->cookie->parent->lock);
 459         spin_unlock(&object->cookie->lock);
 460         _leave("");
 461 }
 462
 463 /*
 464  * look an object up in the cache from which it was allocated
 465  * - we hold an "access lock" on the parent object, so the parent object cannot
 466  *   be withdrawn by either party till we've finished
 467  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 468  *   leaf-most cookies of the object and all its children
 469  */
 470 static void fscache_lookup_object(struct fscache_object *object)
 471 {
 472         struct fscache_cookie *cookie = object->cookie;
 473         struct fscache_object *parent;
 474         int ret;
 475
 476         _enter("");
 477
 478         parent = object->parent;
 479         ASSERT(parent != NULL);
 480         ASSERTCMP(parent->n_ops, >, 0);
 481         ASSERTCMP(parent->n_obj_ops, >, 0);
 482
 483         /* make sure the parent is still available */
 484         ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
 485
 486         if (parent->state >= FSCACHE_OBJECT_DYING ||
 487             test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 488                 _debug("unavailable");
 489                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 490                 _leave("");
 491                 return;
 492         }
 493
 494         _debug("LOOKUP \"%s/%s\" in \"%s\"",
 495                parent->cookie->def->name, cookie->def->name,
 496                object->cache->tag->name);
 497
 498         fscache_stat(&fscache_n_object_lookups);
 499         fscache_stat(&fscache_n_cop_lookup_object);
 500         ret = object->cache->ops->lookup_object(object);
 501         fscache_stat_d(&fscache_n_cop_lookup_object);
 502
 503         if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
 504                 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 505
 506         if (ret == -ETIMEDOUT) {
 507                 /* probably stuck behind another object, so move this one to
 508                  * the back of the queue */
 509                 fscache_stat(&fscache_n_object_lookups_timed_out);
 510                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 511         }
 512
 513         _leave("");
 514 }
 515
 516 /**
 517  * fscache_object_lookup_negative - Note negative cookie lookup
 518  * @object: Object pointing to cookie to mark
 519  *
 520  * Note negative lookup, permitting those waiting to read data from an already
 521  * existing backing object to continue as there's no data for them to read.
 522  */
 523 void fscache_object_lookup_negative(struct fscache_object *object)
 524 {
 525         struct fscache_cookie *cookie = object->cookie;
 526
 527         _enter("{OBJ%x,%s}",
 528                object->debug_id, fscache_object_states[object->state]);
 529
 530         spin_lock(&object->lock);
 531         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 532                 fscache_stat(&fscache_n_object_lookups_negative);
 533
 534                 /* transit here to allow write requests to begin stacking up
 535                  * and read requests to begin returning ENODATA */
 536                 object->state = FSCACHE_OBJECT_CREATING;
 537                 spin_unlock(&object->lock);
 538
 539                 set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
 540                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 541
 542                 _debug("wake up lookup %p", &cookie->flags);
 543                 smp_mb__before_clear_bit();
 544                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 545                 smp_mb__after_clear_bit();
 546                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 547                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 548         } else {
 549                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 550                 spin_unlock(&object->lock);
 551         }
 552
 553         _leave("");
 554 }
 555 EXPORT_SYMBOL(fscache_object_lookup_negative);
 556
 557 /**
 558  * fscache_obtained_object - Note successful object lookup or creation
 559  * @object: Object pointing to cookie to mark
 560  *
 561  * Note successful lookup and/or creation, permitting those waiting to write
 562  * data to a backing object to continue.
 563  *
 564  * Note that after calling this, an object's cookie may be relinquished by the
 565  * netfs, and so must be accessed with object lock held.
 566  */
 567 void fscache_obtained_object(struct fscache_object *object)
 568 {
 569         struct fscache_cookie *cookie = object->cookie;
 570
 571         _enter("{OBJ%x,%s}",
 572                object->debug_id, fscache_object_states[object->state]);
 573
 574         /* if we were still looking up, then we must have a positive lookup
 575          * result, in which case there may be data available */
 576         spin_lock(&object->lock);
 577         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 578                 fscache_stat(&fscache_n_object_lookups_positive);
 579
 580                 clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 581
 582                 object->state = FSCACHE_OBJECT_AVAILABLE;
 583                 spin_unlock(&object->lock);
 584
 585                 smp_mb__before_clear_bit();
 586                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 587                 smp_mb__after_clear_bit();
 588                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 589                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 590         } else {
 591                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 592                 fscache_stat(&fscache_n_object_created);
 593
 594                 object->state = FSCACHE_OBJECT_AVAILABLE;
 595                 spin_unlock(&object->lock);
 596                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 597                 smp_wmb();
 598         }
 599
 600         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
 601                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 602
 603         _leave("");
 604 }
 605 EXPORT_SYMBOL(fscache_obtained_object);
 606
 607 /*
 608  * handle an object that has just become available
 609  */
 610 static void fscache_object_available(struct fscache_object *object)
 611 {
 612         _enter("{OBJ%x}", object->debug_id);
 613
 614         spin_lock(&object->lock);
 615
 616         if (object->cookie &&
 617             test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
 618                 wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
 619
 620         fscache_done_parent_op(object);
 621         if (object->n_in_progress == 0) {
 622                 if (object->n_ops > 0) {
 623                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 624                         fscache_start_operations(object);
 625                 } else {
 626                         ASSERT(list_empty(&object->pending_ops));
 627                 }
 628         }
 629         spin_unlock(&object->lock);
 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         fscache_enqueue_dependents(object);
 635
 636         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 637         fscache_stat(&fscache_n_object_avail);
 638
 639         _leave("");
 640 }
 641
 642 /*
 643  * drop an object's attachments
 644  */
 645 static void fscache_drop_object(struct fscache_object *object)
 646 {
 647         struct fscache_object *parent = object->parent;
 648         struct fscache_cache *cache = object->cache;
 649
 650         _enter("{OBJ%x,%d}", object->debug_id, object->n_children);
 651
 652         ASSERTCMP(object->cookie, ==, NULL);
 653         ASSERT(hlist_unhashed(&object->cookie_link));
 654
 655         spin_lock(&cache->object_list_lock);
 656         list_del_init(&object->cache_link);
 657         spin_unlock(&cache->object_list_lock);
 658
 659         fscache_stat(&fscache_n_cop_drop_object);
 660         cache->ops->drop_object(object);
 661         fscache_stat_d(&fscache_n_cop_drop_object);
 662
 663         if (parent) {
 664                 _debug("release parent OBJ%x {%d}",
 665                        parent->debug_id, parent->n_children);
 666
 667                 spin_lock(&parent->lock);
 668                 parent->n_children--;
 669                 if (parent->n_children == 0)
 670                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 671                 spin_unlock(&parent->lock);
 672                 object->parent = NULL;
 673         }
 674
 675         /* this just shifts the object release to the work processor */
 676         fscache_put_object(object);
 677
 678         _leave("");
 679 }
 680
 681 /*
 682  * release or recycle an object that the netfs has discarded
 683  */
 684 static void fscache_release_object(struct fscache_object *object)
 685 {
 686         _enter("");
 687
 688         fscache_drop_object(object);
 689 }
 690
 691 /*
 692  * withdraw an object from active service
 693  */
 694 static void fscache_withdraw_object(struct fscache_object *object)
 695 {
 696         struct fscache_cookie *cookie;
 697         bool detached;
 698
 699         _enter("");
 700
 701         spin_lock(&object->lock);
 702         cookie = object->cookie;
 703         if (cookie) {
 704                 /* need to get the cookie lock before the object lock, starting
 705                  * from the object pointer */
 706                 atomic_inc(&cookie->usage);
 707                 spin_unlock(&object->lock);
 708
 709                 detached = false;
 710                 spin_lock(&cookie->lock);
 711                 spin_lock(&object->lock);
 712
 713                 if (object->cookie == cookie) {
 714                         hlist_del_init(&object->cookie_link);
 715                         object->cookie = NULL;
 716                         fscache_invalidation_complete(cookie);
 717                         detached = true;
 718                 }
 719                 spin_unlock(&cookie->lock);
 720                 fscache_cookie_put(cookie);
 721                 if (detached)
 722                         fscache_cookie_put(cookie);
 723         }
 724
 725         spin_unlock(&object->lock);
 726
 727         fscache_drop_object(object);
 728 }
 729
 730 /*
 731  * withdraw an object from active service at the behest of the cache
 732  * - need break the links to a cached object cookie
 733  * - called under two situations:
 734  *   (1) recycler decides to reclaim an in-use object
 735  *   (2) a cache is unmounted
 736  * - have to take care as the cookie can be being relinquished by the netfs
 737  *   simultaneously
 738  * - the object is pinned by the caller holding a refcount on it
 739  */
 740 void fscache_withdrawing_object(struct fscache_cache *cache,
 741                                 struct fscache_object *object)
 742 {
 743         bool enqueue = false;
 744
 745         _enter(",OBJ%x", object->debug_id);
 746
 747         spin_lock(&object->lock);
 748         if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
 749                 object->state = FSCACHE_OBJECT_WITHDRAWING;
 750                 enqueue = true;
 751         }
 752         spin_unlock(&object->lock);
 753
 754         if (enqueue)
 755                 fscache_enqueue_object(object);
 756
 757         _leave("");
 758 }
 759
 760 /*
 761  * get a ref on an object
 762  */
 763 static int fscache_get_object(struct fscache_object *object)
 764 {
 765         int ret;
 766
 767         fscache_stat(&fscache_n_cop_grab_object);
 768         ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 769         fscache_stat_d(&fscache_n_cop_grab_object);
 770         return ret;
 771 }
 772
 773 /*
 774  * discard a ref on a work item
 775  */
 776 static void fscache_put_object(struct fscache_object *object)
 777 {
 778         fscache_stat(&fscache_n_cop_put_object);
 779         object->cache->ops->put_object(object);
 780         fscache_stat_d(&fscache_n_cop_put_object);
 781 }
 782
 783 /*
 784  * enqueue an object for metadata-type processing
 785  */
 786 void fscache_enqueue_object(struct fscache_object *object)
 787 {
 788         _enter("{OBJ%x}", object->debug_id);
 789
 790         if (fscache_get_object(object) >= 0) {
 791                 wait_queue_head_t *cong_wq =
 792                         &get_cpu_var(fscache_object_cong_wait);
 793
 794                 if (queue_work(fscache_object_wq, &object->work)) {
 795                         if (fscache_object_congested())
 796                                 wake_up(cong_wq);
 797                 } else
 798                         fscache_put_object(object);
 799
 800                 put_cpu_var(fscache_object_cong_wait);
 801         }
 802 }
 803
 804 /**
 805  * fscache_object_sleep_till_congested - Sleep until object wq is congested
 806  * @timoutp: Scheduler sleep timeout
 807  *
 808  * Allow an object handler to sleep until the object workqueue is congested.
 809  *
 810  * The caller must set up a wake up event before calling this and must have set
 811  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 812  * condition before calling this function as no test is made here.
 813  *
 814  * %true is returned if the object wq is congested, %false otherwise.
 815  */
 816 bool fscache_object_sleep_till_congested(signed long *timeoutp)
 817 {
 818         wait_queue_head_t *cong_wq = &__get_cpu_var(fscache_object_cong_wait);
 819         DEFINE_WAIT(wait);
 820
 821         if (fscache_object_congested())
 822                 return true;
 823
 824         add_wait_queue_exclusive(cong_wq, &wait);
 825         if (!fscache_object_congested())
 826                 *timeoutp = schedule_timeout(*timeoutp);
 827         finish_wait(cong_wq, &wait);
 828
 829         return fscache_object_congested();
 830 }
 831 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 832
 833 /*
 834  * enqueue the dependents of an object for metadata-type processing
 835  * - the caller must hold the object's lock
 836  * - this may cause an already locked object to wind up being processed again
 837  */
 838 static void fscache_enqueue_dependents(struct fscache_object *object)
 839 {
 840         struct fscache_object *dep;
 841
 842         _enter("{OBJ%x}", object->debug_id);
 843
 844         if (list_empty(&object->dependents))
 845                 return;
 846
 847         spin_lock(&object->lock);
 848
 849         while (!list_empty(&object->dependents)) {
 850                 dep = list_entry(object->dependents.next,
 851                                  struct fscache_object, dep_link);
 852                 list_del_init(&dep->dep_link);
 853
 854
 855                 /* sort onto appropriate lists */
 856                 fscache_enqueue_object(dep);
 857                 fscache_put_object(dep);
 858
 859                 if (!list_empty(&object->dependents))
 860                         cond_resched_lock(&object->lock);
 861         }
 862
 863         spin_unlock(&object->lock);
 864 }
 865
 866 /*
 867  * remove an object from whatever queue it's waiting on
 868  * - the caller must hold object->lock
 869  */
 870 void fscache_dequeue_object(struct fscache_object *object)
 871 {
 872         _enter("{OBJ%x}", object->debug_id);
 873
 874         if (!list_empty(&object->dep_link)) {
 875                 spin_lock(&object->parent->lock);
 876                 list_del_init(&object->dep_link);
 877                 spin_unlock(&object->parent->lock);
 878         }
 879
 880         _leave("");
 881 }
 882
 883 /**
 884  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 885  * @object: The object to ask about
 886  * @data: The auxiliary data for the object
 887  * @datalen: The size of the auxiliary data
 888  *
 889  * This function consults the netfs about the coherency state of an object
 890  */
 891 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 892                                         const void *data, uint16_t datalen)
 893 {
 894         enum fscache_checkaux result;
 895
 896         if (!object->cookie->def->check_aux) {
 897                 fscache_stat(&fscache_n_checkaux_none);
 898                 return FSCACHE_CHECKAUX_OKAY;
 899         }
 900
 901         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 902                                                 data, datalen);
 903         switch (result) {
 904                 /* entry okay as is */
 905         case FSCACHE_CHECKAUX_OKAY:
 906                 fscache_stat(&fscache_n_checkaux_okay);
 907                 break;
 908
 909                 /* entry requires update */
 910         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 911                 fscache_stat(&fscache_n_checkaux_update);
 912                 break;
 913
 914                 /* entry requires deletion */
 915         case FSCACHE_CHECKAUX_OBSOLETE:
 916                 fscache_stat(&fscache_n_checkaux_obsolete);
 917                 break;
 918
 919         default:
 920                 BUG();
 921         }
 922
 923         return result;
 924 }
 925 EXPORT_SYMBOL(fscache_check_aux);
 926
 927 /*
 928  * Asynchronously invalidate an object.
 929  */
 930 static void fscache_invalidate_object(struct fscache_object *object)
 931 {
 932         struct fscache_operation *op;
 933         struct fscache_cookie *cookie = object->cookie;
 934
 935         _enter("{OBJ%x}", object->debug_id);
 936
 937         /* Reject any new read/write ops and abort any that are pending. */
 938         fscache_invalidate_writes(cookie);
 939         clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 940         fscache_cancel_all_ops(object);
 941
 942         /* Now we have to wait for in-progress reads and writes */
 943         op = kzalloc(sizeof(*op), GFP_KERNEL);
 944         if (!op) {
 945                 fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
 946                 _leave(" [ENOMEM]");
 947                 return;
 948         }
 949
 950         fscache_operation_init(op, object->cache->ops->invalidate_object, NULL);
 951         op->flags = FSCACHE_OP_ASYNC | (1 << FSCACHE_OP_EXCLUSIVE);
 952
 953         spin_lock(&cookie->lock);
 954         if (fscache_submit_exclusive_op(object, op) < 0)
 955                 goto submit_op_failed;
 956         spin_unlock(&cookie->lock);
 957         fscache_put_operation(op);
 958
 959         /* Once we've completed the invalidation, we know there will be no data
 960          * stored in the cache and thus we can reinstate the data-check-skip
 961          * optimisation.
 962          */
 963         set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 964
 965         /* We can allow read and write requests to come in once again.  They'll
 966          * queue up behind our exclusive invalidation operation.
 967          */
 968         fscache_invalidation_complete(cookie);
 969         _leave("");
 970         return;
 971
 972 submit_op_failed:
 973         spin_unlock(&cookie->lock);
 974         kfree(op);
 975         fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
 976         _leave(" [EIO]");
 977 }