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   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 "internal.h"
  18
  19 const char *fscache_object_states[] = {
  20         [FSCACHE_OBJECT_INIT]           = "OBJECT_INIT",
  21         [FSCACHE_OBJECT_LOOKING_UP]     = "OBJECT_LOOKING_UP",
  22         [FSCACHE_OBJECT_CREATING]       = "OBJECT_CREATING",
  23         [FSCACHE_OBJECT_AVAILABLE]      = "OBJECT_AVAILABLE",
  24         [FSCACHE_OBJECT_ACTIVE]         = "OBJECT_ACTIVE",
  25         [FSCACHE_OBJECT_UPDATING]       = "OBJECT_UPDATING",
  26         [FSCACHE_OBJECT_DYING]          = "OBJECT_DYING",
  27         [FSCACHE_OBJECT_LC_DYING]       = "OBJECT_LC_DYING",
  28         [FSCACHE_OBJECT_ABORT_INIT]     = "OBJECT_ABORT_INIT",
  29         [FSCACHE_OBJECT_RELEASING]      = "OBJECT_RELEASING",
  30         [FSCACHE_OBJECT_RECYCLING]      = "OBJECT_RECYCLING",
  31         [FSCACHE_OBJECT_WITHDRAWING]    = "OBJECT_WITHDRAWING",
  32         [FSCACHE_OBJECT_DEAD]           = "OBJECT_DEAD",
  33 };
  34 EXPORT_SYMBOL(fscache_object_states);
  35
  36 static void fscache_object_slow_work_put_ref(struct slow_work *);
  37 static int  fscache_object_slow_work_get_ref(struct slow_work *);
  38 static void fscache_object_slow_work_execute(struct slow_work *);
  39 static void fscache_initialise_object(struct fscache_object *);
  40 static void fscache_lookup_object(struct fscache_object *);
  41 static void fscache_object_available(struct fscache_object *);
  42 static void fscache_release_object(struct fscache_object *);
  43 static void fscache_withdraw_object(struct fscache_object *);
  44 static void fscache_enqueue_dependents(struct fscache_object *);
  45 static void fscache_dequeue_object(struct fscache_object *);
  46
  47 const struct slow_work_ops fscache_object_slow_work_ops = {
  48         .get_ref        = fscache_object_slow_work_get_ref,
  49         .put_ref        = fscache_object_slow_work_put_ref,
  50         .execute        = fscache_object_slow_work_execute,
  51 };
  52 EXPORT_SYMBOL(fscache_object_slow_work_ops);
  53
  54 /*
  55  * we need to notify the parent when an op completes that we had outstanding
  56  * upon it
  57  */
  58 static inline void fscache_done_parent_op(struct fscache_object *object)
  59 {
  60         struct fscache_object *parent = object->parent;
  61
  62         _enter("OBJ%x {OBJ%x,%x}",
  63                object->debug_id, parent->debug_id, parent->n_ops);
  64
  65         spin_lock_nested(&parent->lock, 1);
  66         parent->n_ops--;
  67         parent->n_obj_ops--;
  68         if (parent->n_ops == 0)
  69                 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
  70         spin_unlock(&parent->lock);
  71 }
  72
  73 /*
  74  * process events that have been sent to an object's state machine
  75  * - initiates parent lookup
  76  * - does object lookup
  77  * - does object creation
  78  * - does object recycling and retirement
  79  * - does object withdrawal
  80  */
  81 static void fscache_object_state_machine(struct fscache_object *object)
  82 {
  83         enum fscache_object_state new_state;
  84
  85         ASSERT(object != NULL);
  86
  87         _enter("{OBJ%x,%s,%lx}",
  88                object->debug_id, fscache_object_states[object->state],
  89                object->events);
  90
  91         switch (object->state) {
  92                 /* wait for the parent object to become ready */
  93         case FSCACHE_OBJECT_INIT:
  94                 object->event_mask =
  95                         ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
  96                 fscache_initialise_object(object);
  97                 goto done;
  98
  99                 /* look up the object metadata on disk */
 100         case FSCACHE_OBJECT_LOOKING_UP:
 101                 fscache_lookup_object(object);
 102                 goto lookup_transit;
 103
 104                 /* create the object metadata on disk */
 105         case FSCACHE_OBJECT_CREATING:
 106                 fscache_lookup_object(object);
 107                 goto lookup_transit;
 108
 109                 /* handle an object becoming available; start pending
 110                  * operations and queue dependent operations for processing */
 111         case FSCACHE_OBJECT_AVAILABLE:
 112                 fscache_object_available(object);
 113                 goto active_transit;
 114
 115                 /* normal running state */
 116         case FSCACHE_OBJECT_ACTIVE:
 117                 goto active_transit;
 118
 119                 /* update the object metadata on disk */
 120         case FSCACHE_OBJECT_UPDATING:
 121                 clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
 122                 fscache_stat(&fscache_n_updates_run);
 123                 object->cache->ops->update_object(object);
 124                 goto active_transit;
 125
 126                 /* handle an object dying during lookup or creation */
 127         case FSCACHE_OBJECT_LC_DYING:
 128                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 129                 object->cache->ops->lookup_complete(object);
 130
 131                 spin_lock(&object->lock);
 132                 object->state = FSCACHE_OBJECT_DYING;
 133                 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 134                                        &object->cookie->flags))
 135                         wake_up_bit(&object->cookie->flags,
 136                                     FSCACHE_COOKIE_CREATING);
 137                 spin_unlock(&object->lock);
 138
 139                 fscache_done_parent_op(object);
 140
 141                 /* wait for completion of all active operations on this object
 142                  * and the death of all child objects of this object */
 143         case FSCACHE_OBJECT_DYING:
 144         dying:
 145                 clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
 146                 spin_lock(&object->lock);
 147                 _debug("dying OBJ%x {%d,%d}",
 148                        object->debug_id, object->n_ops, object->n_children);
 149                 if (object->n_ops == 0 && object->n_children == 0) {
 150                         object->event_mask &=
 151                                 ~(1 << FSCACHE_OBJECT_EV_CLEARED);
 152                         object->event_mask |=
 153                                 (1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 154                                 (1 << FSCACHE_OBJECT_EV_RETIRE) |
 155                                 (1 << FSCACHE_OBJECT_EV_RELEASE) |
 156                                 (1 << FSCACHE_OBJECT_EV_ERROR);
 157                 } else {
 158                         object->event_mask &=
 159                                 ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 160                                   (1 << FSCACHE_OBJECT_EV_RETIRE) |
 161                                   (1 << FSCACHE_OBJECT_EV_RELEASE) |
 162                                   (1 << FSCACHE_OBJECT_EV_ERROR));
 163                         object->event_mask |=
 164                                 1 << FSCACHE_OBJECT_EV_CLEARED;
 165                 }
 166                 spin_unlock(&object->lock);
 167                 fscache_enqueue_dependents(object);
 168                 goto terminal_transit;
 169
 170                 /* handle an abort during initialisation */
 171         case FSCACHE_OBJECT_ABORT_INIT:
 172                 _debug("handle abort init %lx", object->events);
 173                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 174
 175                 spin_lock(&object->lock);
 176                 fscache_dequeue_object(object);
 177
 178                 object->state = FSCACHE_OBJECT_DYING;
 179                 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 180                                        &object->cookie->flags))
 181                         wake_up_bit(&object->cookie->flags,
 182                                     FSCACHE_COOKIE_CREATING);
 183                 spin_unlock(&object->lock);
 184                 goto dying;
 185
 186                 /* handle the netfs releasing an object and possibly marking it
 187                  * obsolete too */
 188         case FSCACHE_OBJECT_RELEASING:
 189         case FSCACHE_OBJECT_RECYCLING:
 190                 object->event_mask &=
 191                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 192                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 193                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 194                           (1 << FSCACHE_OBJECT_EV_ERROR));
 195                 fscache_release_object(object);
 196                 spin_lock(&object->lock);
 197                 object->state = FSCACHE_OBJECT_DEAD;
 198                 spin_unlock(&object->lock);
 199                 fscache_stat(&fscache_n_object_dead);
 200                 goto terminal_transit;
 201
 202                 /* handle the parent cache of this object being withdrawn from
 203                  * active service */
 204         case FSCACHE_OBJECT_WITHDRAWING:
 205                 object->event_mask &=
 206                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 207                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 208                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 209                           (1 << FSCACHE_OBJECT_EV_ERROR));
 210                 fscache_withdraw_object(object);
 211                 spin_lock(&object->lock);
 212                 object->state = FSCACHE_OBJECT_DEAD;
 213                 spin_unlock(&object->lock);
 214                 fscache_stat(&fscache_n_object_dead);
 215                 goto terminal_transit;
 216
 217                 /* complain about the object being woken up once it is
 218                  * deceased */
 219         case FSCACHE_OBJECT_DEAD:
 220                 printk(KERN_ERR "FS-Cache:"
 221                        " Unexpected event in dead state %lx\n",
 222                        object->events & object->event_mask);
 223                 BUG();
 224
 225         default:
 226                 printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
 227                        object->state);
 228                 BUG();
 229         }
 230
 231         /* determine the transition from a lookup state */
 232 lookup_transit:
 233         switch (fls(object->events & object->event_mask) - 1) {
 234         case FSCACHE_OBJECT_EV_WITHDRAW:
 235         case FSCACHE_OBJECT_EV_RETIRE:
 236         case FSCACHE_OBJECT_EV_RELEASE:
 237         case FSCACHE_OBJECT_EV_ERROR:
 238                 new_state = FSCACHE_OBJECT_LC_DYING;
 239                 goto change_state;
 240         case FSCACHE_OBJECT_EV_REQUEUE:
 241                 goto done;
 242         case -1:
 243                 goto done; /* sleep until event */
 244         default:
 245                 goto unsupported_event;
 246         }
 247
 248         /* determine the transition from an active state */
 249 active_transit:
 250         switch (fls(object->events & object->event_mask) - 1) {
 251         case FSCACHE_OBJECT_EV_WITHDRAW:
 252         case FSCACHE_OBJECT_EV_RETIRE:
 253         case FSCACHE_OBJECT_EV_RELEASE:
 254         case FSCACHE_OBJECT_EV_ERROR:
 255                 new_state = FSCACHE_OBJECT_DYING;
 256                 goto change_state;
 257         case FSCACHE_OBJECT_EV_UPDATE:
 258                 new_state = FSCACHE_OBJECT_UPDATING;
 259                 goto change_state;
 260         case -1:
 261                 new_state = FSCACHE_OBJECT_ACTIVE;
 262                 goto change_state; /* sleep until event */
 263         default:
 264                 goto unsupported_event;
 265         }
 266
 267         /* determine the transition from a terminal state */
 268 terminal_transit:
 269         switch (fls(object->events & object->event_mask) - 1) {
 270         case FSCACHE_OBJECT_EV_WITHDRAW:
 271                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 272                 goto change_state;
 273         case FSCACHE_OBJECT_EV_RETIRE:
 274                 new_state = FSCACHE_OBJECT_RECYCLING;
 275                 goto change_state;
 276         case FSCACHE_OBJECT_EV_RELEASE:
 277                 new_state = FSCACHE_OBJECT_RELEASING;
 278                 goto change_state;
 279         case FSCACHE_OBJECT_EV_ERROR:
 280                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 281                 goto change_state;
 282         case FSCACHE_OBJECT_EV_CLEARED:
 283                 new_state = FSCACHE_OBJECT_DYING;
 284                 goto change_state;
 285         case -1:
 286                 goto done; /* sleep until event */
 287         default:
 288                 goto unsupported_event;
 289         }
 290
 291 change_state:
 292         spin_lock(&object->lock);
 293         object->state = new_state;
 294         spin_unlock(&object->lock);
 295
 296 done:
 297         _leave(" [->%s]", fscache_object_states[object->state]);
 298         return;
 299
 300 unsupported_event:
 301         printk(KERN_ERR "FS-Cache:"
 302                " Unsupported event %lx [mask %lx] in state %s\n",
 303                object->events, object->event_mask,
 304                fscache_object_states[object->state]);
 305         BUG();
 306 }
 307
 308 /*
 309  * execute an object
 310  */
 311 static void fscache_object_slow_work_execute(struct slow_work *work)
 312 {
 313         struct fscache_object *object =
 314                 container_of(work, struct fscache_object, work);
 315         unsigned long start;
 316
 317         _enter("{OBJ%x}", object->debug_id);
 318
 319         clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 320
 321         start = jiffies;
 322         fscache_object_state_machine(object);
 323         fscache_hist(fscache_objs_histogram, start);
 324         if (object->events & object->event_mask)
 325                 fscache_enqueue_object(object);
 326 }
 327
 328 /*
 329  * initialise an object
 330  * - check the specified object's parent to see if we can make use of it
 331  *   immediately to do a creation
 332  * - we may need to start the process of creating a parent and we need to wait
 333  *   for the parent's lookup and creation to complete if it's not there yet
 334  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 335  *   leaf-most cookies of the object and all its children
 336  */
 337 static void fscache_initialise_object(struct fscache_object *object)
 338 {
 339         struct fscache_object *parent;
 340
 341         _enter("");
 342         ASSERT(object->cookie != NULL);
 343         ASSERT(object->cookie->parent != NULL);
 344         ASSERT(list_empty(&object->work.link));
 345
 346         if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
 347                               (1 << FSCACHE_OBJECT_EV_RELEASE) |
 348                               (1 << FSCACHE_OBJECT_EV_RETIRE) |
 349                               (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
 350                 _debug("abort init %lx", object->events);
 351                 spin_lock(&object->lock);
 352                 object->state = FSCACHE_OBJECT_ABORT_INIT;
 353                 spin_unlock(&object->lock);
 354                 return;
 355         }
 356
 357         spin_lock(&object->cookie->lock);
 358         spin_lock_nested(&object->cookie->parent->lock, 1);
 359
 360         parent = object->parent;
 361         if (!parent) {
 362                 _debug("no parent");
 363                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 364         } else {
 365                 spin_lock(&object->lock);
 366                 spin_lock_nested(&parent->lock, 1);
 367                 _debug("parent %s", fscache_object_states[parent->state]);
 368
 369                 if (parent->state >= FSCACHE_OBJECT_DYING) {
 370                         _debug("bad parent");
 371                         set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 372                 } else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
 373                         _debug("wait");
 374
 375                         /* we may get woken up in this state by child objects
 376                          * binding on to us, so we need to make sure we don't
 377                          * add ourself to the list multiple times */
 378                         if (list_empty(&object->dep_link)) {
 379                                 object->cache->ops->grab_object(object);
 380                                 list_add(&object->dep_link,
 381                                          &parent->dependents);
 382
 383                                 /* fscache_acquire_non_index_cookie() uses this
 384                                  * to wake the chain up */
 385                                 if (parent->state == FSCACHE_OBJECT_INIT)
 386                                         fscache_enqueue_object(parent);
 387                         }
 388                 } else {
 389                         _debug("go");
 390                         parent->n_ops++;
 391                         parent->n_obj_ops++;
 392                         object->lookup_jif = jiffies;
 393                         object->state = FSCACHE_OBJECT_LOOKING_UP;
 394                         set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 395                 }
 396
 397                 spin_unlock(&parent->lock);
 398                 spin_unlock(&object->lock);
 399         }
 400
 401         spin_unlock(&object->cookie->parent->lock);
 402         spin_unlock(&object->cookie->lock);
 403         _leave("");
 404 }
 405
 406 /*
 407  * look an object up in the cache from which it was allocated
 408  * - we hold an "access lock" on the parent object, so the parent object cannot
 409  *   be withdrawn by either party till we've finished
 410  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 411  *   leaf-most cookies of the object and all its children
 412  */
 413 static void fscache_lookup_object(struct fscache_object *object)
 414 {
 415         struct fscache_cookie *cookie = object->cookie;
 416         struct fscache_object *parent;
 417
 418         _enter("");
 419
 420         parent = object->parent;
 421         ASSERT(parent != NULL);
 422         ASSERTCMP(parent->n_ops, >, 0);
 423         ASSERTCMP(parent->n_obj_ops, >, 0);
 424
 425         /* make sure the parent is still available */
 426         ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
 427
 428         if (parent->state >= FSCACHE_OBJECT_DYING ||
 429             test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 430                 _debug("unavailable");
 431                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 432                 _leave("");
 433                 return;
 434         }
 435
 436         _debug("LOOKUP \"%s/%s\" in \"%s\"",
 437                parent->cookie->def->name, cookie->def->name,
 438                object->cache->tag->name);
 439
 440         fscache_stat(&fscache_n_object_lookups);
 441         object->cache->ops->lookup_object(object);
 442
 443         if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
 444                 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 445
 446         _leave("");
 447 }
 448
 449 /**
 450  * fscache_object_lookup_negative - Note negative cookie lookup
 451  * @object: Object pointing to cookie to mark
 452  *
 453  * Note negative lookup, permitting those waiting to read data from an already
 454  * existing backing object to continue as there's no data for them to read.
 455  */
 456 void fscache_object_lookup_negative(struct fscache_object *object)
 457 {
 458         struct fscache_cookie *cookie = object->cookie;
 459
 460         _enter("{OBJ%x,%s}",
 461                object->debug_id, fscache_object_states[object->state]);
 462
 463         spin_lock(&object->lock);
 464         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 465                 fscache_stat(&fscache_n_object_lookups_negative);
 466
 467                 /* transit here to allow write requests to begin stacking up
 468                  * and read requests to begin returning ENODATA */
 469                 object->state = FSCACHE_OBJECT_CREATING;
 470                 spin_unlock(&object->lock);
 471
 472                 set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
 473                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 474
 475                 _debug("wake up lookup %p", &cookie->flags);
 476                 smp_mb__before_clear_bit();
 477                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 478                 smp_mb__after_clear_bit();
 479                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 480                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 481         } else {
 482                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 483                 spin_unlock(&object->lock);
 484         }
 485
 486         _leave("");
 487 }
 488 EXPORT_SYMBOL(fscache_object_lookup_negative);
 489
 490 /**
 491  * fscache_obtained_object - Note successful object lookup or creation
 492  * @object: Object pointing to cookie to mark
 493  *
 494  * Note successful lookup and/or creation, permitting those waiting to write
 495  * data to a backing object to continue.
 496  *
 497  * Note that after calling this, an object's cookie may be relinquished by the
 498  * netfs, and so must be accessed with object lock held.
 499  */
 500 void fscache_obtained_object(struct fscache_object *object)
 501 {
 502         struct fscache_cookie *cookie = object->cookie;
 503
 504         _enter("{OBJ%x,%s}",
 505                object->debug_id, fscache_object_states[object->state]);
 506
 507         /* if we were still looking up, then we must have a positive lookup
 508          * result, in which case there may be data available */
 509         spin_lock(&object->lock);
 510         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 511                 fscache_stat(&fscache_n_object_lookups_positive);
 512
 513                 clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 514
 515                 object->state = FSCACHE_OBJECT_AVAILABLE;
 516                 spin_unlock(&object->lock);
 517
 518                 smp_mb__before_clear_bit();
 519                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 520                 smp_mb__after_clear_bit();
 521                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 522                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 523         } else {
 524                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 525                 fscache_stat(&fscache_n_object_created);
 526
 527                 object->state = FSCACHE_OBJECT_AVAILABLE;
 528                 spin_unlock(&object->lock);
 529                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 530                 smp_wmb();
 531         }
 532
 533         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
 534                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 535
 536         _leave("");
 537 }
 538 EXPORT_SYMBOL(fscache_obtained_object);
 539
 540 /*
 541  * handle an object that has just become available
 542  */
 543 static void fscache_object_available(struct fscache_object *object)
 544 {
 545         _enter("{OBJ%x}", object->debug_id);
 546
 547         spin_lock(&object->lock);
 548
 549         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
 550                 wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
 551
 552         fscache_done_parent_op(object);
 553         if (object->n_in_progress == 0) {
 554                 if (object->n_ops > 0) {
 555                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 556                         ASSERTIF(object->n_ops > object->n_obj_ops,
 557                                  !list_empty(&object->pending_ops));
 558                         fscache_start_operations(object);
 559                 } else {
 560                         ASSERT(list_empty(&object->pending_ops));
 561                 }
 562         }
 563         spin_unlock(&object->lock);
 564
 565         object->cache->ops->lookup_complete(object);
 566         fscache_enqueue_dependents(object);
 567
 568         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 569         fscache_stat(&fscache_n_object_avail);
 570
 571         _leave("");
 572 }
 573
 574 /*
 575  * drop an object's attachments
 576  */
 577 static void fscache_drop_object(struct fscache_object *object)
 578 {
 579         struct fscache_object *parent = object->parent;
 580         struct fscache_cache *cache = object->cache;
 581
 582         _enter("{OBJ%x,%d}", object->debug_id, object->n_children);
 583
 584         spin_lock(&cache->object_list_lock);
 585         list_del_init(&object->cache_link);
 586         spin_unlock(&cache->object_list_lock);
 587
 588         cache->ops->drop_object(object);
 589
 590         if (parent) {
 591                 _debug("release parent OBJ%x {%d}",
 592                        parent->debug_id, parent->n_children);
 593
 594                 spin_lock(&parent->lock);
 595                 parent->n_children--;
 596                 if (parent->n_children == 0)
 597                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 598                 spin_unlock(&parent->lock);
 599                 object->parent = NULL;
 600         }
 601
 602         /* this just shifts the object release to the slow work processor */
 603         object->cache->ops->put_object(object);
 604
 605         _leave("");
 606 }
 607
 608 /*
 609  * release or recycle an object that the netfs has discarded
 610  */
 611 static void fscache_release_object(struct fscache_object *object)
 612 {
 613         _enter("");
 614
 615         fscache_drop_object(object);
 616 }
 617
 618 /*
 619  * withdraw an object from active service
 620  */
 621 static void fscache_withdraw_object(struct fscache_object *object)
 622 {
 623         struct fscache_cookie *cookie;
 624         bool detached;
 625
 626         _enter("");
 627
 628         spin_lock(&object->lock);
 629         cookie = object->cookie;
 630         if (cookie) {
 631                 /* need to get the cookie lock before the object lock, starting
 632                  * from the object pointer */
 633                 atomic_inc(&cookie->usage);
 634                 spin_unlock(&object->lock);
 635
 636                 detached = false;
 637                 spin_lock(&cookie->lock);
 638                 spin_lock(&object->lock);
 639
 640                 if (object->cookie == cookie) {
 641                         hlist_del_init(&object->cookie_link);
 642                         object->cookie = NULL;
 643                         detached = true;
 644                 }
 645                 spin_unlock(&cookie->lock);
 646                 fscache_cookie_put(cookie);
 647                 if (detached)
 648                         fscache_cookie_put(cookie);
 649         }
 650
 651         spin_unlock(&object->lock);
 652
 653         fscache_drop_object(object);
 654 }
 655
 656 /*
 657  * withdraw an object from active service at the behest of the cache
 658  * - need break the links to a cached object cookie
 659  * - called under two situations:
 660  *   (1) recycler decides to reclaim an in-use object
 661  *   (2) a cache is unmounted
 662  * - have to take care as the cookie can be being relinquished by the netfs
 663  *   simultaneously
 664  * - the object is pinned by the caller holding a refcount on it
 665  */
 666 void fscache_withdrawing_object(struct fscache_cache *cache,
 667                                 struct fscache_object *object)
 668 {
 669         bool enqueue = false;
 670
 671         _enter(",OBJ%x", object->debug_id);
 672
 673         spin_lock(&object->lock);
 674         if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
 675                 object->state = FSCACHE_OBJECT_WITHDRAWING;
 676                 enqueue = true;
 677         }
 678         spin_unlock(&object->lock);
 679
 680         if (enqueue)
 681                 fscache_enqueue_object(object);
 682
 683         _leave("");
 684 }
 685
 686 /*
 687  * allow the slow work item processor to get a ref on an object
 688  */
 689 static int fscache_object_slow_work_get_ref(struct slow_work *work)
 690 {
 691         struct fscache_object *object =
 692                 container_of(work, struct fscache_object, work);
 693
 694         return object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 695 }
 696
 697 /*
 698  * allow the slow work item processor to discard a ref on a work item
 699  */
 700 static void fscache_object_slow_work_put_ref(struct slow_work *work)
 701 {
 702         struct fscache_object *object =
 703                 container_of(work, struct fscache_object, work);
 704
 705         return object->cache->ops->put_object(object);
 706 }
 707
 708 /*
 709  * enqueue an object for metadata-type processing
 710  */
 711 void fscache_enqueue_object(struct fscache_object *object)
 712 {
 713         _enter("{OBJ%x}", object->debug_id);
 714
 715         slow_work_enqueue(&object->work);
 716 }
 717
 718 /*
 719  * enqueue the dependents of an object for metadata-type processing
 720  * - the caller must hold the object's lock
 721  * - this may cause an already locked object to wind up being processed again
 722  */
 723 static void fscache_enqueue_dependents(struct fscache_object *object)
 724 {
 725         struct fscache_object *dep;
 726
 727         _enter("{OBJ%x}", object->debug_id);
 728
 729         if (list_empty(&object->dependents))
 730                 return;
 731
 732         spin_lock(&object->lock);
 733
 734         while (!list_empty(&object->dependents)) {
 735                 dep = list_entry(object->dependents.next,
 736                                  struct fscache_object, dep_link);
 737                 list_del_init(&dep->dep_link);
 738
 739
 740                 /* sort onto appropriate lists */
 741                 fscache_enqueue_object(dep);
 742                 dep->cache->ops->put_object(dep);
 743
 744                 if (!list_empty(&object->dependents))
 745                         cond_resched_lock(&object->lock);
 746         }
 747
 748         spin_unlock(&object->lock);
 749 }
 750
 751 /*
 752  * remove an object from whatever queue it's waiting on
 753  * - the caller must hold object->lock
 754  */
 755 void fscache_dequeue_object(struct fscache_object *object)
 756 {
 757         _enter("{OBJ%x}", object->debug_id);
 758
 759         if (!list_empty(&object->dep_link)) {
 760                 spin_lock(&object->parent->lock);
 761                 list_del_init(&object->dep_link);
 762                 spin_unlock(&object->parent->lock);
 763         }
 764
 765         _leave("");
 766 }
 767
 768 /**
 769  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 770  * @object: The object to ask about
 771  * @data: The auxiliary data for the object
 772  * @datalen: The size of the auxiliary data
 773  *
 774  * This function consults the netfs about the coherency state of an object
 775  */
 776 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 777                                         const void *data, uint16_t datalen)
 778 {
 779         enum fscache_checkaux result;
 780
 781         if (!object->cookie->def->check_aux) {
 782                 fscache_stat(&fscache_n_checkaux_none);
 783                 return FSCACHE_CHECKAUX_OKAY;
 784         }
 785
 786         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 787                                                 data, datalen);
 788         switch (result) {
 789                 /* entry okay as is */
 790         case FSCACHE_CHECKAUX_OKAY:
 791                 fscache_stat(&fscache_n_checkaux_okay);
 792                 break;
 793
 794                 /* entry requires update */
 795         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 796                 fscache_stat(&fscache_n_checkaux_update);
 797                 break;
 798
 799                 /* entry requires deletion */
 800         case FSCACHE_CHECKAUX_OBSOLETE:
 801                 fscache_stat(&fscache_n_checkaux_obsolete);
 802                 break;
 803
 804         default:
 805                 BUG();
 806         }
 807
 808         return result;
 809 }
 810 EXPORT_SYMBOL(fscache_check_aux);