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