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 "internal.h"
  18
  19 const char *fscache_object_states[FSCACHE_OBJECT__NSTATES] = {
  20         [FSCACHE_OBJECT_INIT]           = "OBJECT_INIT",
  21         [FSCACHE_OBJECT_LOOKING_UP]     = "OBJECT_LOOKING_UP",
  22         [FSCACHE_OBJECT_CREATING]       = "OBJECT_CREATING",
  23         [FSCACHE_OBJECT_AVAILABLE]      = "OBJECT_AVAILABLE",
  24         [FSCACHE_OBJECT_ACTIVE]         = "OBJECT_ACTIVE",
  25         [FSCACHE_OBJECT_UPDATING]       = "OBJECT_UPDATING",
  26         [FSCACHE_OBJECT_DYING]          = "OBJECT_DYING",
  27         [FSCACHE_OBJECT_LC_DYING]       = "OBJECT_LC_DYING",
  28         [FSCACHE_OBJECT_ABORT_INIT]     = "OBJECT_ABORT_INIT",
  29         [FSCACHE_OBJECT_RELEASING]      = "OBJECT_RELEASING",
  30         [FSCACHE_OBJECT_RECYCLING]      = "OBJECT_RECYCLING",
  31         [FSCACHE_OBJECT_WITHDRAWING]    = "OBJECT_WITHDRAWING",
  32         [FSCACHE_OBJECT_DEAD]           = "OBJECT_DEAD",
  33 };
  34 EXPORT_SYMBOL(fscache_object_states);
  35
  36 const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5] = {
  37         [FSCACHE_OBJECT_INIT]           = "INIT",
  38         [FSCACHE_OBJECT_LOOKING_UP]     = "LOOK",
  39         [FSCACHE_OBJECT_CREATING]       = "CRTN",
  40         [FSCACHE_OBJECT_AVAILABLE]      = "AVBL",
  41         [FSCACHE_OBJECT_ACTIVE]         = "ACTV",
  42         [FSCACHE_OBJECT_UPDATING]       = "UPDT",
  43         [FSCACHE_OBJECT_DYING]          = "DYNG",
  44         [FSCACHE_OBJECT_LC_DYING]       = "LCDY",
  45         [FSCACHE_OBJECT_ABORT_INIT]     = "ABTI",
  46         [FSCACHE_OBJECT_RELEASING]      = "RELS",
  47         [FSCACHE_OBJECT_RECYCLING]      = "RCYC",
  48         [FSCACHE_OBJECT_WITHDRAWING]    = "WTHD",
  49         [FSCACHE_OBJECT_DEAD]           = "DEAD",
  50 };
  51
  52 static int  fscache_get_object(struct fscache_object *);
  53 static void fscache_put_object(struct fscache_object *);
  54 static void fscache_initialise_object(struct fscache_object *);
  55 static void fscache_lookup_object(struct fscache_object *);
  56 static void fscache_object_available(struct fscache_object *);
  57 static void fscache_release_object(struct fscache_object *);
  58 static void fscache_withdraw_object(struct fscache_object *);
  59 static void fscache_enqueue_dependents(struct fscache_object *);
  60 static void fscache_dequeue_object(struct fscache_object *);
  61
  62 /*
  63  * we need to notify the parent when an op completes that we had outstanding
  64  * upon it
  65  */
  66 static inline void fscache_done_parent_op(struct fscache_object *object)
  67 {
  68         struct fscache_object *parent = object->parent;
  69
  70         _enter("OBJ%x {OBJ%x,%x}",
  71                object->debug_id, parent->debug_id, parent->n_ops);
  72
  73         spin_lock_nested(&parent->lock, 1);
  74         parent->n_ops--;
  75         parent->n_obj_ops--;
  76         if (parent->n_ops == 0)
  77                 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
  78         spin_unlock(&parent->lock);
  79 }
  80
  81 /*
  82  * process events that have been sent to an object's state machine
  83  * - initiates parent lookup
  84  * - does object lookup
  85  * - does object creation
  86  * - does object recycling and retirement
  87  * - does object withdrawal
  88  */
  89 static void fscache_object_state_machine(struct fscache_object *object)
  90 {
  91         enum fscache_object_state new_state;
  92         struct fscache_cookie *cookie;
  93
  94         ASSERT(object != NULL);
  95
  96         _enter("{OBJ%x,%s,%lx}",
  97                object->debug_id, fscache_object_states[object->state],
  98                object->events);
  99
 100         switch (object->state) {
 101                 /* wait for the parent object to become ready */
 102         case FSCACHE_OBJECT_INIT:
 103                 object->event_mask =
 104                         ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
 105                 fscache_initialise_object(object);
 106                 goto done;
 107
 108                 /* look up the object metadata on disk */
 109         case FSCACHE_OBJECT_LOOKING_UP:
 110                 fscache_lookup_object(object);
 111                 goto lookup_transit;
 112
 113                 /* create the object metadata on disk */
 114         case FSCACHE_OBJECT_CREATING:
 115                 fscache_lookup_object(object);
 116                 goto lookup_transit;
 117
 118                 /* handle an object becoming available; start pending
 119                  * operations and queue dependent operations for processing */
 120         case FSCACHE_OBJECT_AVAILABLE:
 121                 fscache_object_available(object);
 122                 goto active_transit;
 123
 124                 /* normal running state */
 125         case FSCACHE_OBJECT_ACTIVE:
 126                 goto active_transit;
 127
 128                 /* update the object metadata on disk */
 129         case FSCACHE_OBJECT_UPDATING:
 130                 clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
 131                 fscache_stat(&fscache_n_updates_run);
 132                 fscache_stat(&fscache_n_cop_update_object);
 133                 object->cache->ops->update_object(object);
 134                 fscache_stat_d(&fscache_n_cop_update_object);
 135                 goto active_transit;
 136
 137                 /* handle an object dying during lookup or creation */
 138         case FSCACHE_OBJECT_LC_DYING:
 139                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 140                 fscache_stat(&fscache_n_cop_lookup_complete);
 141                 object->cache->ops->lookup_complete(object);
 142                 fscache_stat_d(&fscache_n_cop_lookup_complete);
 143
 144                 spin_lock(&object->lock);
 145                 object->state = FSCACHE_OBJECT_DYING;
 146                 cookie = object->cookie;
 147                 if (cookie) {
 148                         if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP,
 149                                                &cookie->flags))
 150                                 wake_up_bit(&cookie->flags,
 151                                             FSCACHE_COOKIE_LOOKING_UP);
 152                         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 153                                                &cookie->flags))
 154                                 wake_up_bit(&cookie->flags,
 155                                             FSCACHE_COOKIE_CREATING);
 156                 }
 157                 spin_unlock(&object->lock);
 158
 159                 fscache_done_parent_op(object);
 160
 161                 /* wait for completion of all active operations on this object
 162                  * and the death of all child objects of this object */
 163         case FSCACHE_OBJECT_DYING:
 164         dying:
 165                 clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
 166                 spin_lock(&object->lock);
 167                 _debug("dying OBJ%x {%d,%d}",
 168                        object->debug_id, object->n_ops, object->n_children);
 169                 if (object->n_ops == 0 && object->n_children == 0) {
 170                         object->event_mask &=
 171                                 ~(1 << FSCACHE_OBJECT_EV_CLEARED);
 172                         object->event_mask |=
 173                                 (1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 174                                 (1 << FSCACHE_OBJECT_EV_RETIRE) |
 175                                 (1 << FSCACHE_OBJECT_EV_RELEASE) |
 176                                 (1 << FSCACHE_OBJECT_EV_ERROR);
 177                 } else {
 178                         object->event_mask &=
 179                                 ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 180                                   (1 << FSCACHE_OBJECT_EV_RETIRE) |
 181                                   (1 << FSCACHE_OBJECT_EV_RELEASE) |
 182                                   (1 << FSCACHE_OBJECT_EV_ERROR));
 183                         object->event_mask |=
 184                                 1 << FSCACHE_OBJECT_EV_CLEARED;
 185                 }
 186                 spin_unlock(&object->lock);
 187                 fscache_enqueue_dependents(object);
 188                 fscache_start_operations(object);
 189                 goto terminal_transit;
 190
 191                 /* handle an abort during initialisation */
 192         case FSCACHE_OBJECT_ABORT_INIT:
 193                 _debug("handle abort init %lx", object->events);
 194                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 195
 196                 spin_lock(&object->lock);
 197                 fscache_dequeue_object(object);
 198
 199                 object->state = FSCACHE_OBJECT_DYING;
 200                 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 201                                        &object->cookie->flags))
 202                         wake_up_bit(&object->cookie->flags,
 203                                     FSCACHE_COOKIE_CREATING);
 204                 spin_unlock(&object->lock);
 205                 goto dying;
 206
 207                 /* handle the netfs releasing an object and possibly marking it
 208                  * obsolete too */
 209         case FSCACHE_OBJECT_RELEASING:
 210         case FSCACHE_OBJECT_RECYCLING:
 211                 object->event_mask &=
 212                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 213                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 214                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 215                           (1 << FSCACHE_OBJECT_EV_ERROR));
 216                 fscache_release_object(object);
 217                 spin_lock(&object->lock);
 218                 object->state = FSCACHE_OBJECT_DEAD;
 219                 spin_unlock(&object->lock);
 220                 fscache_stat(&fscache_n_object_dead);
 221                 goto terminal_transit;
 222
 223                 /* handle the parent cache of this object being withdrawn from
 224                  * active service */
 225         case FSCACHE_OBJECT_WITHDRAWING:
 226                 object->event_mask &=
 227                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 228                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 229                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 230                           (1 << FSCACHE_OBJECT_EV_ERROR));
 231                 fscache_withdraw_object(object);
 232                 spin_lock(&object->lock);
 233                 object->state = FSCACHE_OBJECT_DEAD;
 234                 spin_unlock(&object->lock);
 235                 fscache_stat(&fscache_n_object_dead);
 236                 goto terminal_transit;
 237
 238                 /* complain about the object being woken up once it is
 239                  * deceased */
 240         case FSCACHE_OBJECT_DEAD:
 241                 printk(KERN_ERR "FS-Cache:"
 242                        " Unexpected event in dead state %lx\n",
 243                        object->events & object->event_mask);
 244                 BUG();
 245
 246         default:
 247                 printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
 248                        object->state);
 249                 BUG();
 250         }
 251
 252         /* determine the transition from a lookup state */
 253 lookup_transit:
 254         switch (fls(object->events & object->event_mask) - 1) {
 255         case FSCACHE_OBJECT_EV_WITHDRAW:
 256         case FSCACHE_OBJECT_EV_RETIRE:
 257         case FSCACHE_OBJECT_EV_RELEASE:
 258         case FSCACHE_OBJECT_EV_ERROR:
 259                 new_state = FSCACHE_OBJECT_LC_DYING;
 260                 goto change_state;
 261         case FSCACHE_OBJECT_EV_REQUEUE:
 262                 goto done;
 263         case -1:
 264                 goto done; /* sleep until event */
 265         default:
 266                 goto unsupported_event;
 267         }
 268
 269         /* determine the transition from an active state */
 270 active_transit:
 271         switch (fls(object->events & object->event_mask) - 1) {
 272         case FSCACHE_OBJECT_EV_WITHDRAW:
 273         case FSCACHE_OBJECT_EV_RETIRE:
 274         case FSCACHE_OBJECT_EV_RELEASE:
 275         case FSCACHE_OBJECT_EV_ERROR:
 276                 new_state = FSCACHE_OBJECT_DYING;
 277                 goto change_state;
 278         case FSCACHE_OBJECT_EV_UPDATE:
 279                 new_state = FSCACHE_OBJECT_UPDATING;
 280                 goto change_state;
 281         case -1:
 282                 new_state = FSCACHE_OBJECT_ACTIVE;
 283                 goto change_state; /* sleep until event */
 284         default:
 285                 goto unsupported_event;
 286         }
 287
 288         /* determine the transition from a terminal state */
 289 terminal_transit:
 290         switch (fls(object->events & object->event_mask) - 1) {
 291         case FSCACHE_OBJECT_EV_WITHDRAW:
 292                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 293                 goto change_state;
 294         case FSCACHE_OBJECT_EV_RETIRE:
 295                 new_state = FSCACHE_OBJECT_RECYCLING;
 296                 goto change_state;
 297         case FSCACHE_OBJECT_EV_RELEASE:
 298                 new_state = FSCACHE_OBJECT_RELEASING;
 299                 goto change_state;
 300         case FSCACHE_OBJECT_EV_ERROR:
 301                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 302                 goto change_state;
 303         case FSCACHE_OBJECT_EV_CLEARED:
 304                 new_state = FSCACHE_OBJECT_DYING;
 305                 goto change_state;
 306         case -1:
 307                 goto done; /* sleep until event */
 308         default:
 309                 goto unsupported_event;
 310         }
 311
 312 change_state:
 313         spin_lock(&object->lock);
 314         object->state = new_state;
 315         spin_unlock(&object->lock);
 316
 317 done:
 318         _leave(" [->%s]", fscache_object_states[object->state]);
 319         return;
 320
 321 unsupported_event:
 322         printk(KERN_ERR "FS-Cache:"
 323                " Unsupported event %lx [mask %lx] in state %s\n",
 324                object->events, object->event_mask,
 325                fscache_object_states[object->state]);
 326         BUG();
 327 }
 328
 329 /*
 330  * execute an object
 331  */
 332 void fscache_object_work_func(struct work_struct *work)
 333 {
 334         struct fscache_object *object =
 335                 container_of(work, struct fscache_object, work);
 336         unsigned long start;
 337
 338         _enter("{OBJ%x}", object->debug_id);
 339
 340         start = jiffies;
 341         fscache_object_state_machine(object);
 342         fscache_hist(fscache_objs_histogram, start);
 343         if (object->events & object->event_mask)
 344                 fscache_enqueue_object(object);
 345         clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 346         fscache_put_object(object);
 347 }
 348 EXPORT_SYMBOL(fscache_object_work_func);
 349
 350 /*
 351  * initialise an object
 352  * - check the specified object's parent to see if we can make use of it
 353  *   immediately to do a creation
 354  * - we may need to start the process of creating a parent and we need to wait
 355  *   for the parent's lookup and creation to complete if it's not there yet
 356  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 357  *   leaf-most cookies of the object and all its children
 358  */
 359 static void fscache_initialise_object(struct fscache_object *object)
 360 {
 361         struct fscache_object *parent;
 362
 363         _enter("");
 364         ASSERT(object->cookie != NULL);
 365         ASSERT(object->cookie->parent != NULL);
 366
 367         if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
 368                               (1 << FSCACHE_OBJECT_EV_RELEASE) |
 369                               (1 << FSCACHE_OBJECT_EV_RETIRE) |
 370                               (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
 371                 _debug("abort init %lx", object->events);
 372                 spin_lock(&object->lock);
 373                 object->state = FSCACHE_OBJECT_ABORT_INIT;
 374                 spin_unlock(&object->lock);
 375                 return;
 376         }
 377
 378         spin_lock(&object->cookie->lock);
 379         spin_lock_nested(&object->cookie->parent->lock, 1);
 380
 381         parent = object->parent;
 382         if (!parent) {
 383                 _debug("no parent");
 384                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 385         } else {
 386                 spin_lock(&object->lock);
 387                 spin_lock_nested(&parent->lock, 1);
 388                 _debug("parent %s", fscache_object_states[parent->state]);
 389
 390                 if (parent->state >= FSCACHE_OBJECT_DYING) {
 391                         _debug("bad parent");
 392                         set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 393                 } else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
 394                         _debug("wait");
 395
 396                         /* we may get woken up in this state by child objects
 397                          * binding on to us, so we need to make sure we don't
 398                          * add ourself to the list multiple times */
 399                         if (list_empty(&object->dep_link)) {
 400                                 fscache_stat(&fscache_n_cop_grab_object);
 401                                 object->cache->ops->grab_object(object);
 402                                 fscache_stat_d(&fscache_n_cop_grab_object);
 403                                 list_add(&object->dep_link,
 404                                          &parent->dependents);
 405
 406                                 /* fscache_acquire_non_index_cookie() uses this
 407                                  * to wake the chain up */
 408                                 if (parent->state == FSCACHE_OBJECT_INIT)
 409                                         fscache_enqueue_object(parent);
 410                         }
 411                 } else {
 412                         _debug("go");
 413                         parent->n_ops++;
 414                         parent->n_obj_ops++;
 415                         object->lookup_jif = jiffies;
 416                         object->state = FSCACHE_OBJECT_LOOKING_UP;
 417                         set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 418                 }
 419
 420                 spin_unlock(&parent->lock);
 421                 spin_unlock(&object->lock);
 422         }
 423
 424         spin_unlock(&object->cookie->parent->lock);
 425         spin_unlock(&object->cookie->lock);
 426         _leave("");
 427 }
 428
 429 /*
 430  * look an object up in the cache from which it was allocated
 431  * - we hold an "access lock" on the parent object, so the parent object cannot
 432  *   be withdrawn by either party till we've finished
 433  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 434  *   leaf-most cookies of the object and all its children
 435  */
 436 static void fscache_lookup_object(struct fscache_object *object)
 437 {
 438         struct fscache_cookie *cookie = object->cookie;
 439         struct fscache_object *parent;
 440         int ret;
 441
 442         _enter("");
 443
 444         parent = object->parent;
 445         ASSERT(parent != NULL);
 446         ASSERTCMP(parent->n_ops, >, 0);
 447         ASSERTCMP(parent->n_obj_ops, >, 0);
 448
 449         /* make sure the parent is still available */
 450         ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
 451
 452         if (parent->state >= FSCACHE_OBJECT_DYING ||
 453             test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 454                 _debug("unavailable");
 455                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 456                 _leave("");
 457                 return;
 458         }
 459
 460         _debug("LOOKUP \"%s/%s\" in \"%s\"",
 461                parent->cookie->def->name, cookie->def->name,
 462                object->cache->tag->name);
 463
 464         fscache_stat(&fscache_n_object_lookups);
 465         fscache_stat(&fscache_n_cop_lookup_object);
 466         ret = object->cache->ops->lookup_object(object);
 467         fscache_stat_d(&fscache_n_cop_lookup_object);
 468
 469         if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
 470                 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 471
 472         if (ret == -ETIMEDOUT) {
 473                 /* probably stuck behind another object, so move this one to
 474                  * the back of the queue */
 475                 fscache_stat(&fscache_n_object_lookups_timed_out);
 476                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 477         }
 478
 479         _leave("");
 480 }
 481
 482 /**
 483  * fscache_object_lookup_negative - Note negative cookie lookup
 484  * @object: Object pointing to cookie to mark
 485  *
 486  * Note negative lookup, permitting those waiting to read data from an already
 487  * existing backing object to continue as there's no data for them to read.
 488  */
 489 void fscache_object_lookup_negative(struct fscache_object *object)
 490 {
 491         struct fscache_cookie *cookie = object->cookie;
 492
 493         _enter("{OBJ%x,%s}",
 494                object->debug_id, fscache_object_states[object->state]);
 495
 496         spin_lock(&object->lock);
 497         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 498                 fscache_stat(&fscache_n_object_lookups_negative);
 499
 500                 /* transit here to allow write requests to begin stacking up
 501                  * and read requests to begin returning ENODATA */
 502                 object->state = FSCACHE_OBJECT_CREATING;
 503                 spin_unlock(&object->lock);
 504
 505                 set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
 506                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 507
 508                 _debug("wake up lookup %p", &cookie->flags);
 509                 smp_mb__before_clear_bit();
 510                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 511                 smp_mb__after_clear_bit();
 512                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 513                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 514         } else {
 515                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 516                 spin_unlock(&object->lock);
 517         }
 518
 519         _leave("");
 520 }
 521 EXPORT_SYMBOL(fscache_object_lookup_negative);
 522
 523 /**
 524  * fscache_obtained_object - Note successful object lookup or creation
 525  * @object: Object pointing to cookie to mark
 526  *
 527  * Note successful lookup and/or creation, permitting those waiting to write
 528  * data to a backing object to continue.
 529  *
 530  * Note that after calling this, an object's cookie may be relinquished by the
 531  * netfs, and so must be accessed with object lock held.
 532  */
 533 void fscache_obtained_object(struct fscache_object *object)
 534 {
 535         struct fscache_cookie *cookie = object->cookie;
 536
 537         _enter("{OBJ%x,%s}",
 538                object->debug_id, fscache_object_states[object->state]);
 539
 540         /* if we were still looking up, then we must have a positive lookup
 541          * result, in which case there may be data available */
 542         spin_lock(&object->lock);
 543         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 544                 fscache_stat(&fscache_n_object_lookups_positive);
 545
 546                 clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 547
 548                 object->state = FSCACHE_OBJECT_AVAILABLE;
 549                 spin_unlock(&object->lock);
 550
 551                 smp_mb__before_clear_bit();
 552                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 553                 smp_mb__after_clear_bit();
 554                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 555                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 556         } else {
 557                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 558                 fscache_stat(&fscache_n_object_created);
 559
 560                 object->state = FSCACHE_OBJECT_AVAILABLE;
 561                 spin_unlock(&object->lock);
 562                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 563                 smp_wmb();
 564         }
 565
 566         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
 567                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 568
 569         _leave("");
 570 }
 571 EXPORT_SYMBOL(fscache_obtained_object);
 572
 573 /*
 574  * handle an object that has just become available
 575  */
 576 static void fscache_object_available(struct fscache_object *object)
 577 {
 578         _enter("{OBJ%x}", object->debug_id);
 579
 580         spin_lock(&object->lock);
 581
 582         if (object->cookie &&
 583             test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
 584                 wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
 585
 586         fscache_done_parent_op(object);
 587         if (object->n_in_progress == 0) {
 588                 if (object->n_ops > 0) {
 589                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 590                         ASSERTIF(object->n_ops > object->n_obj_ops,
 591                                  !list_empty(&object->pending_ops));
 592                         fscache_start_operations(object);
 593                 } else {
 594                         ASSERT(list_empty(&object->pending_ops));
 595                 }
 596         }
 597         spin_unlock(&object->lock);
 598
 599         fscache_stat(&fscache_n_cop_lookup_complete);
 600         object->cache->ops->lookup_complete(object);
 601         fscache_stat_d(&fscache_n_cop_lookup_complete);
 602         fscache_enqueue_dependents(object);
 603
 604         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 605         fscache_stat(&fscache_n_object_avail);
 606
 607         _leave("");
 608 }
 609
 610 /*
 611  * drop an object's attachments
 612  */
 613 static void fscache_drop_object(struct fscache_object *object)
 614 {
 615         struct fscache_object *parent = object->parent;
 616         struct fscache_cache *cache = object->cache;
 617
 618         _enter("{OBJ%x,%d}", object->debug_id, object->n_children);
 619
 620         ASSERTCMP(object->cookie, ==, NULL);
 621         ASSERT(hlist_unhashed(&object->cookie_link));
 622
 623         spin_lock(&cache->object_list_lock);
 624         list_del_init(&object->cache_link);
 625         spin_unlock(&cache->object_list_lock);
 626
 627         fscache_stat(&fscache_n_cop_drop_object);
 628         cache->ops->drop_object(object);
 629         fscache_stat_d(&fscache_n_cop_drop_object);
 630
 631         if (parent) {
 632                 _debug("release parent OBJ%x {%d}",
 633                        parent->debug_id, parent->n_children);
 634
 635                 spin_lock(&parent->lock);
 636                 parent->n_children--;
 637                 if (parent->n_children == 0)
 638                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 639                 spin_unlock(&parent->lock);
 640                 object->parent = NULL;
 641         }
 642
 643         /* this just shifts the object release to the work processor */
 644         fscache_put_object(object);
 645
 646         _leave("");
 647 }
 648
 649 /*
 650  * release or recycle an object that the netfs has discarded
 651  */
 652 static void fscache_release_object(struct fscache_object *object)
 653 {
 654         _enter("");
 655
 656         fscache_drop_object(object);
 657 }
 658
 659 /*
 660  * withdraw an object from active service
 661  */
 662 static void fscache_withdraw_object(struct fscache_object *object)
 663 {
 664         struct fscache_cookie *cookie;
 665         bool detached;
 666
 667         _enter("");
 668
 669         spin_lock(&object->lock);
 670         cookie = object->cookie;
 671         if (cookie) {
 672                 /* need to get the cookie lock before the object lock, starting
 673                  * from the object pointer */
 674                 atomic_inc(&cookie->usage);
 675                 spin_unlock(&object->lock);
 676
 677                 detached = false;
 678                 spin_lock(&cookie->lock);
 679                 spin_lock(&object->lock);
 680
 681                 if (object->cookie == cookie) {
 682                         hlist_del_init(&object->cookie_link);
 683                         object->cookie = NULL;
 684                         detached = true;
 685                 }
 686                 spin_unlock(&cookie->lock);
 687                 fscache_cookie_put(cookie);
 688                 if (detached)
 689                         fscache_cookie_put(cookie);
 690         }
 691
 692         spin_unlock(&object->lock);
 693
 694         fscache_drop_object(object);
 695 }
 696
 697 /*
 698  * withdraw an object from active service at the behest of the cache
 699  * - need break the links to a cached object cookie
 700  * - called under two situations:
 701  *   (1) recycler decides to reclaim an in-use object
 702  *   (2) a cache is unmounted
 703  * - have to take care as the cookie can be being relinquished by the netfs
 704  *   simultaneously
 705  * - the object is pinned by the caller holding a refcount on it
 706  */
 707 void fscache_withdrawing_object(struct fscache_cache *cache,
 708                                 struct fscache_object *object)
 709 {
 710         bool enqueue = false;
 711
 712         _enter(",OBJ%x", object->debug_id);
 713
 714         spin_lock(&object->lock);
 715         if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
 716                 object->state = FSCACHE_OBJECT_WITHDRAWING;
 717                 enqueue = true;
 718         }
 719         spin_unlock(&object->lock);
 720
 721         if (enqueue)
 722                 fscache_enqueue_object(object);
 723
 724         _leave("");
 725 }
 726
 727 /*
 728  * get a ref on an object
 729  */
 730 static int fscache_get_object(struct fscache_object *object)
 731 {
 732         int ret;
 733
 734         fscache_stat(&fscache_n_cop_grab_object);
 735         ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 736         fscache_stat_d(&fscache_n_cop_grab_object);
 737         return ret;
 738 }
 739
 740 /*
 741  * discard a ref on a work item
 742  */
 743 static void fscache_put_object(struct fscache_object *object)
 744 {
 745         fscache_stat(&fscache_n_cop_put_object);
 746         object->cache->ops->put_object(object);
 747         fscache_stat_d(&fscache_n_cop_put_object);
 748 }
 749
 750 /*
 751  * enqueue an object for metadata-type processing
 752  */
 753 void fscache_enqueue_object(struct fscache_object *object)
 754 {
 755         _enter("{OBJ%x}", object->debug_id);
 756
 757         if (fscache_get_object(object) >= 0) {
 758                 wait_queue_head_t *cong_wq =
 759                         &get_cpu_var(fscache_object_cong_wait);
 760
 761                 if (queue_work(fscache_object_wq, &object->work)) {
 762                         if (fscache_object_congested())
 763                                 wake_up(cong_wq);
 764                 } else
 765                         fscache_put_object(object);
 766
 767                 put_cpu_var(fscache_object_cong_wait);
 768         }
 769 }
 770
 771 /**
 772  * fscache_object_sleep_till_congested - Sleep until object wq is congested
 773  * @timoutp: Scheduler sleep timeout
 774  *
 775  * Allow an object handler to sleep until the object workqueue is congested.
 776  *
 777  * The caller must set up a wake up event before calling this and must have set
 778  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
 779  * condition before calling this function as no test is made here.
 780  *
 781  * %true is returned if the object wq is congested, %false otherwise.
 782  */
 783 bool fscache_object_sleep_till_congested(signed long *timeoutp)
 784 {
 785         wait_queue_head_t *cong_wq = &__get_cpu_var(fscache_object_cong_wait);
 786         DEFINE_WAIT(wait);
 787
 788         if (fscache_object_congested())
 789                 return true;
 790
 791         add_wait_queue_exclusive(cong_wq, &wait);
 792         if (!fscache_object_congested())
 793                 *timeoutp = schedule_timeout(*timeoutp);
 794         finish_wait(cong_wq, &wait);
 795
 796         return fscache_object_congested();
 797 }
 798 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 799
 800 /*
 801  * enqueue the dependents of an object for metadata-type processing
 802  * - the caller must hold the object's lock
 803  * - this may cause an already locked object to wind up being processed again
 804  */
 805 static void fscache_enqueue_dependents(struct fscache_object *object)
 806 {
 807         struct fscache_object *dep;
 808
 809         _enter("{OBJ%x}", object->debug_id);
 810
 811         if (list_empty(&object->dependents))
 812                 return;
 813
 814         spin_lock(&object->lock);
 815
 816         while (!list_empty(&object->dependents)) {
 817                 dep = list_entry(object->dependents.next,
 818                                  struct fscache_object, dep_link);
 819                 list_del_init(&dep->dep_link);
 820
 821
 822                 /* sort onto appropriate lists */
 823                 fscache_enqueue_object(dep);
 824                 fscache_put_object(dep);
 825
 826                 if (!list_empty(&object->dependents))
 827                         cond_resched_lock(&object->lock);
 828         }
 829
 830         spin_unlock(&object->lock);
 831 }
 832
 833 /*
 834  * remove an object from whatever queue it's waiting on
 835  * - the caller must hold object->lock
 836  */
 837 void fscache_dequeue_object(struct fscache_object *object)
 838 {
 839         _enter("{OBJ%x}", object->debug_id);
 840
 841         if (!list_empty(&object->dep_link)) {
 842                 spin_lock(&object->parent->lock);
 843                 list_del_init(&object->dep_link);
 844                 spin_unlock(&object->parent->lock);
 845         }
 846
 847         _leave("");
 848 }
 849
 850 /**
 851  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 852  * @object: The object to ask about
 853  * @data: The auxiliary data for the object
 854  * @datalen: The size of the auxiliary data
 855  *
 856  * This function consults the netfs about the coherency state of an object
 857  */
 858 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 859                                         const void *data, uint16_t datalen)
 860 {
 861         enum fscache_checkaux result;
 862
 863         if (!object->cookie->def->check_aux) {
 864                 fscache_stat(&fscache_n_checkaux_none);
 865                 return FSCACHE_CHECKAUX_OKAY;
 866         }
 867
 868         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 869                                                 data, datalen);
 870         switch (result) {
 871                 /* entry okay as is */
 872         case FSCACHE_CHECKAUX_OKAY:
 873                 fscache_stat(&fscache_n_checkaux_okay);
 874                 break;
 875
 876                 /* entry requires update */
 877         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 878                 fscache_stat(&fscache_n_checkaux_update);
 879                 break;
 880
 881                 /* entry requires deletion */
 882         case FSCACHE_CHECKAUX_OBSOLETE:
 883                 fscache_stat(&fscache_n_checkaux_obsolete);
 884                 break;
 885
 886         default:
 887                 BUG();
 888         }
 889
 890         return result;
 891 }
 892 EXPORT_SYMBOL(fscache_check_aux);