fs/fscache/object.c

   1 /* FS-Cache object state machine handler
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  *
  11  * See Documentation/filesystems/caching/object.txt for a description of the
  12  * object state machine and the in-kernel representations.
  13  */
  14
  15 #define FSCACHE_DEBUG_LEVEL COOKIE
  16 #include <linux/module.h>
  17 #include <linux/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                 object->cache->ops->update_object(object);
 148                 goto active_transit;
 149
 150                 /* handle an object dying during lookup or creation */
 151         case FSCACHE_OBJECT_LC_DYING:
 152                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 153                 object->cache->ops->lookup_complete(object);
 154
 155                 spin_lock(&object->lock);
 156                 object->state = FSCACHE_OBJECT_DYING;
 157                 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 158                                        &object->cookie->flags))
 159                         wake_up_bit(&object->cookie->flags,
 160                                     FSCACHE_COOKIE_CREATING);
 161                 spin_unlock(&object->lock);
 162
 163                 fscache_done_parent_op(object);
 164
 165                 /* wait for completion of all active operations on this object
 166                  * and the death of all child objects of this object */
 167         case FSCACHE_OBJECT_DYING:
 168         dying:
 169                 clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
 170                 spin_lock(&object->lock);
 171                 _debug("dying OBJ%x {%d,%d}",
 172                        object->debug_id, object->n_ops, object->n_children);
 173                 if (object->n_ops == 0 && object->n_children == 0) {
 174                         object->event_mask &=
 175                                 ~(1 << FSCACHE_OBJECT_EV_CLEARED);
 176                         object->event_mask |=
 177                                 (1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 178                                 (1 << FSCACHE_OBJECT_EV_RETIRE) |
 179                                 (1 << FSCACHE_OBJECT_EV_RELEASE) |
 180                                 (1 << FSCACHE_OBJECT_EV_ERROR);
 181                 } else {
 182                         object->event_mask &=
 183                                 ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 184                                   (1 << FSCACHE_OBJECT_EV_RETIRE) |
 185                                   (1 << FSCACHE_OBJECT_EV_RELEASE) |
 186                                   (1 << FSCACHE_OBJECT_EV_ERROR));
 187                         object->event_mask |=
 188                                 1 << FSCACHE_OBJECT_EV_CLEARED;
 189                 }
 190                 spin_unlock(&object->lock);
 191                 fscache_enqueue_dependents(object);
 192                 goto terminal_transit;
 193
 194                 /* handle an abort during initialisation */
 195         case FSCACHE_OBJECT_ABORT_INIT:
 196                 _debug("handle abort init %lx", object->events);
 197                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 198
 199                 spin_lock(&object->lock);
 200                 fscache_dequeue_object(object);
 201
 202                 object->state = FSCACHE_OBJECT_DYING;
 203                 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 204                                        &object->cookie->flags))
 205                         wake_up_bit(&object->cookie->flags,
 206                                     FSCACHE_COOKIE_CREATING);
 207                 spin_unlock(&object->lock);
 208                 goto dying;
 209
 210                 /* handle the netfs releasing an object and possibly marking it
 211                  * obsolete too */
 212         case FSCACHE_OBJECT_RELEASING:
 213         case FSCACHE_OBJECT_RECYCLING:
 214                 object->event_mask &=
 215                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 216                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 217                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 218                           (1 << FSCACHE_OBJECT_EV_ERROR));
 219                 fscache_release_object(object);
 220                 spin_lock(&object->lock);
 221                 object->state = FSCACHE_OBJECT_DEAD;
 222                 spin_unlock(&object->lock);
 223                 fscache_stat(&fscache_n_object_dead);
 224                 goto terminal_transit;
 225
 226                 /* handle the parent cache of this object being withdrawn from
 227                  * active service */
 228         case FSCACHE_OBJECT_WITHDRAWING:
 229                 object->event_mask &=
 230                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 231                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 232                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 233                           (1 << FSCACHE_OBJECT_EV_ERROR));
 234                 fscache_withdraw_object(object);
 235                 spin_lock(&object->lock);
 236                 object->state = FSCACHE_OBJECT_DEAD;
 237                 spin_unlock(&object->lock);
 238                 fscache_stat(&fscache_n_object_dead);
 239                 goto terminal_transit;
 240
 241                 /* complain about the object being woken up once it is
 242                  * deceased */
 243         case FSCACHE_OBJECT_DEAD:
 244                 printk(KERN_ERR "FS-Cache:"
 245                        " Unexpected event in dead state %lx\n",
 246                        object->events & object->event_mask);
 247                 BUG();
 248
 249         default:
 250                 printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
 251                        object->state);
 252                 BUG();
 253         }
 254
 255         /* determine the transition from a lookup state */
 256 lookup_transit:
 257         switch (fls(object->events & object->event_mask) - 1) {
 258         case FSCACHE_OBJECT_EV_WITHDRAW:
 259         case FSCACHE_OBJECT_EV_RETIRE:
 260         case FSCACHE_OBJECT_EV_RELEASE:
 261         case FSCACHE_OBJECT_EV_ERROR:
 262                 new_state = FSCACHE_OBJECT_LC_DYING;
 263                 goto change_state;
 264         case FSCACHE_OBJECT_EV_REQUEUE:
 265                 goto done;
 266         case -1:
 267                 goto done; /* sleep until event */
 268         default:
 269                 goto unsupported_event;
 270         }
 271
 272         /* determine the transition from an active state */
 273 active_transit:
 274         switch (fls(object->events & object->event_mask) - 1) {
 275         case FSCACHE_OBJECT_EV_WITHDRAW:
 276         case FSCACHE_OBJECT_EV_RETIRE:
 277         case FSCACHE_OBJECT_EV_RELEASE:
 278         case FSCACHE_OBJECT_EV_ERROR:
 279                 new_state = FSCACHE_OBJECT_DYING;
 280                 goto change_state;
 281         case FSCACHE_OBJECT_EV_UPDATE:
 282                 new_state = FSCACHE_OBJECT_UPDATING;
 283                 goto change_state;
 284         case -1:
 285                 new_state = FSCACHE_OBJECT_ACTIVE;
 286                 goto change_state; /* sleep until event */
 287         default:
 288                 goto unsupported_event;
 289         }
 290
 291         /* determine the transition from a terminal state */
 292 terminal_transit:
 293         switch (fls(object->events & object->event_mask) - 1) {
 294         case FSCACHE_OBJECT_EV_WITHDRAW:
 295                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 296                 goto change_state;
 297         case FSCACHE_OBJECT_EV_RETIRE:
 298                 new_state = FSCACHE_OBJECT_RECYCLING;
 299                 goto change_state;
 300         case FSCACHE_OBJECT_EV_RELEASE:
 301                 new_state = FSCACHE_OBJECT_RELEASING;
 302                 goto change_state;
 303         case FSCACHE_OBJECT_EV_ERROR:
 304                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 305                 goto change_state;
 306         case FSCACHE_OBJECT_EV_CLEARED:
 307                 new_state = FSCACHE_OBJECT_DYING;
 308                 goto change_state;
 309         case -1:
 310                 goto done; /* sleep until event */
 311         default:
 312                 goto unsupported_event;
 313         }
 314
 315 change_state:
 316         spin_lock(&object->lock);
 317         object->state = new_state;
 318         spin_unlock(&object->lock);
 319
 320 done:
 321         _leave(" [->%s]", fscache_object_states[object->state]);
 322         return;
 323
 324 unsupported_event:
 325         printk(KERN_ERR "FS-Cache:"
 326                " Unsupported event %lx [mask %lx] in state %s\n",
 327                object->events, object->event_mask,
 328                fscache_object_states[object->state]);
 329         BUG();
 330 }
 331
 332 /*
 333  * execute an object
 334  */
 335 static void fscache_object_slow_work_execute(struct slow_work *work)
 336 {
 337         struct fscache_object *object =
 338                 container_of(work, struct fscache_object, work);
 339         unsigned long start;
 340
 341         _enter("{OBJ%x}", object->debug_id);
 342
 343         clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 344
 345         start = jiffies;
 346         fscache_object_state_machine(object);
 347         fscache_hist(fscache_objs_histogram, start);
 348         if (object->events & object->event_mask)
 349                 fscache_enqueue_object(object);
 350 }
 351
 352 /*
 353  * describe an object for slow-work debugging
 354  */
 355 #ifdef CONFIG_SLOW_WORK_PROC
 356 static void fscache_object_slow_work_desc(struct slow_work *work,
 357                                           struct seq_file *m)
 358 {
 359         struct fscache_object *object =
 360                 container_of(work, struct fscache_object, work);
 361
 362         seq_printf(m, "FSC: OBJ%x: %s",
 363                    object->debug_id,
 364                    fscache_object_states_short[object->state]);
 365 }
 366 #endif
 367
 368 /*
 369  * initialise an object
 370  * - check the specified object's parent to see if we can make use of it
 371  *   immediately to do a creation
 372  * - we may need to start the process of creating a parent and we need to wait
 373  *   for the parent's lookup and creation to complete if it's not there yet
 374  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 375  *   leaf-most cookies of the object and all its children
 376  */
 377 static void fscache_initialise_object(struct fscache_object *object)
 378 {
 379         struct fscache_object *parent;
 380
 381         _enter("");
 382         ASSERT(object->cookie != NULL);
 383         ASSERT(object->cookie->parent != NULL);
 384         ASSERT(list_empty(&object->work.link));
 385
 386         if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
 387                               (1 << FSCACHE_OBJECT_EV_RELEASE) |
 388                               (1 << FSCACHE_OBJECT_EV_RETIRE) |
 389                               (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
 390                 _debug("abort init %lx", object->events);
 391                 spin_lock(&object->lock);
 392                 object->state = FSCACHE_OBJECT_ABORT_INIT;
 393                 spin_unlock(&object->lock);
 394                 return;
 395         }
 396
 397         spin_lock(&object->cookie->lock);
 398         spin_lock_nested(&object->cookie->parent->lock, 1);
 399
 400         parent = object->parent;
 401         if (!parent) {
 402                 _debug("no parent");
 403                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 404         } else {
 405                 spin_lock(&object->lock);
 406                 spin_lock_nested(&parent->lock, 1);
 407                 _debug("parent %s", fscache_object_states[parent->state]);
 408
 409                 if (parent->state >= FSCACHE_OBJECT_DYING) {
 410                         _debug("bad parent");
 411                         set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 412                 } else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
 413                         _debug("wait");
 414
 415                         /* we may get woken up in this state by child objects
 416                          * binding on to us, so we need to make sure we don't
 417                          * add ourself to the list multiple times */
 418                         if (list_empty(&object->dep_link)) {
 419                                 object->cache->ops->grab_object(object);
 420                                 list_add(&object->dep_link,
 421                                          &parent->dependents);
 422
 423                                 /* fscache_acquire_non_index_cookie() uses this
 424                                  * to wake the chain up */
 425                                 if (parent->state == FSCACHE_OBJECT_INIT)
 426                                         fscache_enqueue_object(parent);
 427                         }
 428                 } else {
 429                         _debug("go");
 430                         parent->n_ops++;
 431                         parent->n_obj_ops++;
 432                         object->lookup_jif = jiffies;
 433                         object->state = FSCACHE_OBJECT_LOOKING_UP;
 434                         set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 435                 }
 436
 437                 spin_unlock(&parent->lock);
 438                 spin_unlock(&object->lock);
 439         }
 440
 441         spin_unlock(&object->cookie->parent->lock);
 442         spin_unlock(&object->cookie->lock);
 443         _leave("");
 444 }
 445
 446 /*
 447  * look an object up in the cache from which it was allocated
 448  * - we hold an "access lock" on the parent object, so the parent object cannot
 449  *   be withdrawn by either party till we've finished
 450  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 451  *   leaf-most cookies of the object and all its children
 452  */
 453 static void fscache_lookup_object(struct fscache_object *object)
 454 {
 455         struct fscache_cookie *cookie = object->cookie;
 456         struct fscache_object *parent;
 457
 458         _enter("");
 459
 460         parent = object->parent;
 461         ASSERT(parent != NULL);
 462         ASSERTCMP(parent->n_ops, >, 0);
 463         ASSERTCMP(parent->n_obj_ops, >, 0);
 464
 465         /* make sure the parent is still available */
 466         ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
 467
 468         if (parent->state >= FSCACHE_OBJECT_DYING ||
 469             test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 470                 _debug("unavailable");
 471                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 472                 _leave("");
 473                 return;
 474         }
 475
 476         _debug("LOOKUP \"%s/%s\" in \"%s\"",
 477                parent->cookie->def->name, cookie->def->name,
 478                object->cache->tag->name);
 479
 480         fscache_stat(&fscache_n_object_lookups);
 481         object->cache->ops->lookup_object(object);
 482
 483         if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
 484                 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 485
 486         _leave("");
 487 }
 488
 489 /**
 490  * fscache_object_lookup_negative - Note negative cookie lookup
 491  * @object: Object pointing to cookie to mark
 492  *
 493  * Note negative lookup, permitting those waiting to read data from an already
 494  * existing backing object to continue as there's no data for them to read.
 495  */
 496 void fscache_object_lookup_negative(struct fscache_object *object)
 497 {
 498         struct fscache_cookie *cookie = object->cookie;
 499
 500         _enter("{OBJ%x,%s}",
 501                object->debug_id, fscache_object_states[object->state]);
 502
 503         spin_lock(&object->lock);
 504         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 505                 fscache_stat(&fscache_n_object_lookups_negative);
 506
 507                 /* transit here to allow write requests to begin stacking up
 508                  * and read requests to begin returning ENODATA */
 509                 object->state = FSCACHE_OBJECT_CREATING;
 510                 spin_unlock(&object->lock);
 511
 512                 set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
 513                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 514
 515                 _debug("wake up lookup %p", &cookie->flags);
 516                 smp_mb__before_clear_bit();
 517                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 518                 smp_mb__after_clear_bit();
 519                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 520                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 521         } else {
 522                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 523                 spin_unlock(&object->lock);
 524         }
 525
 526         _leave("");
 527 }
 528 EXPORT_SYMBOL(fscache_object_lookup_negative);
 529
 530 /**
 531  * fscache_obtained_object - Note successful object lookup or creation
 532  * @object: Object pointing to cookie to mark
 533  *
 534  * Note successful lookup and/or creation, permitting those waiting to write
 535  * data to a backing object to continue.
 536  *
 537  * Note that after calling this, an object's cookie may be relinquished by the
 538  * netfs, and so must be accessed with object lock held.
 539  */
 540 void fscache_obtained_object(struct fscache_object *object)
 541 {
 542         struct fscache_cookie *cookie = object->cookie;
 543
 544         _enter("{OBJ%x,%s}",
 545                object->debug_id, fscache_object_states[object->state]);
 546
 547         /* if we were still looking up, then we must have a positive lookup
 548          * result, in which case there may be data available */
 549         spin_lock(&object->lock);
 550         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 551                 fscache_stat(&fscache_n_object_lookups_positive);
 552
 553                 clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 554
 555                 object->state = FSCACHE_OBJECT_AVAILABLE;
 556                 spin_unlock(&object->lock);
 557
 558                 smp_mb__before_clear_bit();
 559                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 560                 smp_mb__after_clear_bit();
 561                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 562                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 563         } else {
 564                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 565                 fscache_stat(&fscache_n_object_created);
 566
 567                 object->state = FSCACHE_OBJECT_AVAILABLE;
 568                 spin_unlock(&object->lock);
 569                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 570                 smp_wmb();
 571         }
 572
 573         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
 574                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 575
 576         _leave("");
 577 }
 578 EXPORT_SYMBOL(fscache_obtained_object);
 579
 580 /*
 581  * handle an object that has just become available
 582  */
 583 static void fscache_object_available(struct fscache_object *object)
 584 {
 585         _enter("{OBJ%x}", object->debug_id);
 586
 587         spin_lock(&object->lock);
 588
 589         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
 590                 wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
 591
 592         fscache_done_parent_op(object);
 593         if (object->n_in_progress == 0) {
 594                 if (object->n_ops > 0) {
 595                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 596                         ASSERTIF(object->n_ops > object->n_obj_ops,
 597                                  !list_empty(&object->pending_ops));
 598                         fscache_start_operations(object);
 599                 } else {
 600                         ASSERT(list_empty(&object->pending_ops));
 601                 }
 602         }
 603         spin_unlock(&object->lock);
 604
 605         object->cache->ops->lookup_complete(object);
 606         fscache_enqueue_dependents(object);
 607
 608         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 609         fscache_stat(&fscache_n_object_avail);
 610
 611         _leave("");
 612 }
 613
 614 /*
 615  * drop an object's attachments
 616  */
 617 static void fscache_drop_object(struct fscache_object *object)
 618 {
 619         struct fscache_object *parent = object->parent;
 620         struct fscache_cache *cache = object->cache;
 621
 622         _enter("{OBJ%x,%d}", object->debug_id, object->n_children);
 623
 624         spin_lock(&cache->object_list_lock);
 625         list_del_init(&object->cache_link);
 626         spin_unlock(&cache->object_list_lock);
 627
 628         cache->ops->drop_object(object);
 629
 630         if (parent) {
 631                 _debug("release parent OBJ%x {%d}",
 632                        parent->debug_id, parent->n_children);
 633
 634                 spin_lock(&parent->lock);
 635                 parent->n_children--;
 636                 if (parent->n_children == 0)
 637                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 638                 spin_unlock(&parent->lock);
 639                 object->parent = NULL;
 640         }
 641
 642         /* this just shifts the object release to the slow work processor */
 643         object->cache->ops->put_object(object);
 644
 645         _leave("");
 646 }
 647
 648 /*
 649  * release or recycle an object that the netfs has discarded
 650  */
 651 static void fscache_release_object(struct fscache_object *object)
 652 {
 653         _enter("");
 654
 655         fscache_drop_object(object);
 656 }
 657
 658 /*
 659  * withdraw an object from active service
 660  */
 661 static void fscache_withdraw_object(struct fscache_object *object)
 662 {
 663         struct fscache_cookie *cookie;
 664         bool detached;
 665
 666         _enter("");
 667
 668         spin_lock(&object->lock);
 669         cookie = object->cookie;
 670         if (cookie) {
 671                 /* need to get the cookie lock before the object lock, starting
 672                  * from the object pointer */
 673                 atomic_inc(&cookie->usage);
 674                 spin_unlock(&object->lock);
 675
 676                 detached = false;
 677                 spin_lock(&cookie->lock);
 678                 spin_lock(&object->lock);
 679
 680                 if (object->cookie == cookie) {
 681                         hlist_del_init(&object->cookie_link);
 682                         object->cookie = NULL;
 683                         detached = true;
 684                 }
 685                 spin_unlock(&cookie->lock);
 686                 fscache_cookie_put(cookie);
 687                 if (detached)
 688                         fscache_cookie_put(cookie);
 689         }
 690
 691         spin_unlock(&object->lock);
 692
 693         fscache_drop_object(object);
 694 }
 695
 696 /*
 697  * withdraw an object from active service at the behest of the cache
 698  * - need break the links to a cached object cookie
 699  * - called under two situations:
 700  *   (1) recycler decides to reclaim an in-use object
 701  *   (2) a cache is unmounted
 702  * - have to take care as the cookie can be being relinquished by the netfs
 703  *   simultaneously
 704  * - the object is pinned by the caller holding a refcount on it
 705  */
 706 void fscache_withdrawing_object(struct fscache_cache *cache,
 707                                 struct fscache_object *object)
 708 {
 709         bool enqueue = false;
 710
 711         _enter(",OBJ%x", object->debug_id);
 712
 713         spin_lock(&object->lock);
 714         if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
 715                 object->state = FSCACHE_OBJECT_WITHDRAWING;
 716                 enqueue = true;
 717         }
 718         spin_unlock(&object->lock);
 719
 720         if (enqueue)
 721                 fscache_enqueue_object(object);
 722
 723         _leave("");
 724 }
 725
 726 /*
 727  * allow the slow work item processor to get a ref on an object
 728  */
 729 static int fscache_object_slow_work_get_ref(struct slow_work *work)
 730 {
 731         struct fscache_object *object =
 732                 container_of(work, struct fscache_object, work);
 733
 734         return object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 735 }
 736
 737 /*
 738  * allow the slow work item processor to discard a ref on a work item
 739  */
 740 static void fscache_object_slow_work_put_ref(struct slow_work *work)
 741 {
 742         struct fscache_object *object =
 743                 container_of(work, struct fscache_object, work);
 744
 745         return object->cache->ops->put_object(object);
 746 }
 747
 748 /*
 749  * enqueue an object for metadata-type processing
 750  */
 751 void fscache_enqueue_object(struct fscache_object *object)
 752 {
 753         _enter("{OBJ%x}", object->debug_id);
 754
 755         slow_work_enqueue(&object->work);
 756 }
 757
 758 /*
 759  * enqueue the dependents of an object for metadata-type processing
 760  * - the caller must hold the object's lock
 761  * - this may cause an already locked object to wind up being processed again
 762  */
 763 static void fscache_enqueue_dependents(struct fscache_object *object)
 764 {
 765         struct fscache_object *dep;
 766
 767         _enter("{OBJ%x}", object->debug_id);
 768
 769         if (list_empty(&object->dependents))
 770                 return;
 771
 772         spin_lock(&object->lock);
 773
 774         while (!list_empty(&object->dependents)) {
 775                 dep = list_entry(object->dependents.next,
 776                                  struct fscache_object, dep_link);
 777                 list_del_init(&dep->dep_link);
 778
 779
 780                 /* sort onto appropriate lists */
 781                 fscache_enqueue_object(dep);
 782                 dep->cache->ops->put_object(dep);
 783
 784                 if (!list_empty(&object->dependents))
 785                         cond_resched_lock(&object->lock);
 786         }
 787
 788         spin_unlock(&object->lock);
 789 }
 790
 791 /*
 792  * remove an object from whatever queue it's waiting on
 793  * - the caller must hold object->lock
 794  */
 795 void fscache_dequeue_object(struct fscache_object *object)
 796 {
 797         _enter("{OBJ%x}", object->debug_id);
 798
 799         if (!list_empty(&object->dep_link)) {
 800                 spin_lock(&object->parent->lock);
 801                 list_del_init(&object->dep_link);
 802                 spin_unlock(&object->parent->lock);
 803         }
 804
 805         _leave("");
 806 }
 807
 808 /**
 809  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 810  * @object: The object to ask about
 811  * @data: The auxiliary data for the object
 812  * @datalen: The size of the auxiliary data
 813  *
 814  * This function consults the netfs about the coherency state of an object
 815  */
 816 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 817                                         const void *data, uint16_t datalen)
 818 {
 819         enum fscache_checkaux result;
 820
 821         if (!object->cookie->def->check_aux) {
 822                 fscache_stat(&fscache_n_checkaux_none);
 823                 return FSCACHE_CHECKAUX_OKAY;
 824         }
 825
 826         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 827                                                 data, datalen);
 828         switch (result) {
 829                 /* entry okay as is */
 830         case FSCACHE_CHECKAUX_OKAY:
 831                 fscache_stat(&fscache_n_checkaux_okay);
 832                 break;
 833
 834                 /* entry requires update */
 835         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 836                 fscache_stat(&fscache_n_checkaux_update);
 837                 break;
 838
 839                 /* entry requires deletion */
 840         case FSCACHE_CHECKAUX_OBSOLETE:
 841                 fscache_stat(&fscache_n_checkaux_obsolete);
 842                 break;
 843
 844         default:
 845                 BUG();
 846         }
 847
 848         return result;
 849 }
 850 EXPORT_SYMBOL(fscache_check_aux);