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