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