fs/fscache/cookie.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* netfs cookie management
   3  *
   4  * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  *
   7  * See Documentation/filesystems/caching/netfs-api.rst for more information on
   8  * the netfs API.
   9  */
  10
  11 #define FSCACHE_DEBUG_LEVEL COOKIE
  12 #include <linux/module.h>
  13 #include <linux/slab.h>
  14 #include "internal.h"
  15
  16 struct kmem_cache *fscache_cookie_jar;
  17
  18 static void fscache_cookie_lru_timed_out(struct timer_list *timer);
  19 static void fscache_cookie_lru_worker(struct work_struct *work);
  20 static void fscache_cookie_worker(struct work_struct *work);
  21 static void fscache_unhash_cookie(struct fscache_cookie *cookie);
  22 static void fscache_perform_invalidation(struct fscache_cookie *cookie);
  23
  24 #define fscache_cookie_hash_shift 15
  25 static struct hlist_bl_head fscache_cookie_hash[1 << fscache_cookie_hash_shift];
  26 static LIST_HEAD(fscache_cookies);
  27 static DEFINE_RWLOCK(fscache_cookies_lock);
  28 static LIST_HEAD(fscache_cookie_lru);
  29 static DEFINE_SPINLOCK(fscache_cookie_lru_lock);
  30 DEFINE_TIMER(fscache_cookie_lru_timer, fscache_cookie_lru_timed_out);
  31 static DECLARE_WORK(fscache_cookie_lru_work, fscache_cookie_lru_worker);
  32 static const char fscache_cookie_states[FSCACHE_COOKIE_STATE__NR] = "-LCAIFUWRD";
  33 unsigned int fscache_lru_cookie_timeout = 10 * HZ;
  34
  35 void fscache_print_cookie(struct fscache_cookie *cookie, char prefix)
  36 {
  37         const u8 *k;
  38
  39         pr_err("%c-cookie c=%08x [fl=%lx na=%u nA=%u s=%c]\n",
  40                prefix,
  41                cookie->debug_id,
  42                cookie->flags,
  43                atomic_read(&cookie->n_active),
  44                atomic_read(&cookie->n_accesses),
  45                fscache_cookie_states[cookie->state]);
  46         pr_err("%c-cookie V=%08x [%s]\n",
  47                prefix,
  48                cookie->volume->debug_id,
  49                cookie->volume->key);
  50
  51         k = (cookie->key_len <= sizeof(cookie->inline_key)) ?
  52                 cookie->inline_key : cookie->key;
  53         pr_err("%c-key=[%u] '%*phN'\n", prefix, cookie->key_len, cookie->key_len, k);
  54 }
  55
  56 static void fscache_free_cookie(struct fscache_cookie *cookie)
  57 {
  58         if (WARN_ON_ONCE(!list_empty(&cookie->commit_link))) {
  59                 spin_lock(&fscache_cookie_lru_lock);
  60                 list_del_init(&cookie->commit_link);
  61                 spin_unlock(&fscache_cookie_lru_lock);
  62                 fscache_stat_d(&fscache_n_cookies_lru);
  63                 fscache_stat(&fscache_n_cookies_lru_removed);
  64         }
  65
  66         if (WARN_ON_ONCE(test_bit(FSCACHE_COOKIE_IS_HASHED, &cookie->flags))) {
  67                 fscache_print_cookie(cookie, 'F');
  68                 return;
  69         }
  70
  71         write_lock(&fscache_cookies_lock);
  72         list_del(&cookie->proc_link);
  73         write_unlock(&fscache_cookies_lock);
  74         if (cookie->aux_len > sizeof(cookie->inline_aux))
  75                 kfree(cookie->aux);
  76         if (cookie->key_len > sizeof(cookie->inline_key))
  77                 kfree(cookie->key);
  78         fscache_stat_d(&fscache_n_cookies);
  79         kmem_cache_free(fscache_cookie_jar, cookie);
  80 }
  81
  82 static void __fscache_queue_cookie(struct fscache_cookie *cookie)
  83 {
  84         if (!queue_work(fscache_wq, &cookie->work))
  85                 fscache_put_cookie(cookie, fscache_cookie_put_over_queued);
  86 }
  87
  88 static void fscache_queue_cookie(struct fscache_cookie *cookie,
  89                                  enum fscache_cookie_trace where)
  90 {
  91         fscache_get_cookie(cookie, where);
  92         __fscache_queue_cookie(cookie);
  93 }
  94
  95 /*
  96  * Initialise the access gate on a cookie by setting a flag to prevent the
  97  * state machine from being queued when the access counter transitions to 0.
  98  * We're only interested in this when we withdraw caching services from the
  99  * cookie.
 100  */
 101 static void fscache_init_access_gate(struct fscache_cookie *cookie)
 102 {
 103         int n_accesses;
 104
 105         n_accesses = atomic_read(&cookie->n_accesses);
 106         trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
 107                              n_accesses, fscache_access_cache_pin);
 108         set_bit(FSCACHE_COOKIE_NO_ACCESS_WAKE, &cookie->flags);
 109 }
 110
 111 /**
 112  * fscache_end_cookie_access - Unpin a cache at the end of an access.
 113  * @cookie: A data file cookie
 114  * @why: An indication of the circumstances of the access for tracing
 115  *
 116  * Unpin a cache cookie after we've accessed it and bring a deferred
 117  * relinquishment or withdrawal state into effect.
 118  *
 119  * The @why indicator is provided for tracing purposes.
 120  */
 121 void fscache_end_cookie_access(struct fscache_cookie *cookie,
 122                                enum fscache_access_trace why)
 123 {
 124         int n_accesses;
 125
 126         smp_mb__before_atomic();
 127         n_accesses = atomic_dec_return(&cookie->n_accesses);
 128         trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
 129                              n_accesses, why);
 130         if (n_accesses == 0 &&
 131             !test_bit(FSCACHE_COOKIE_NO_ACCESS_WAKE, &cookie->flags))
 132                 fscache_queue_cookie(cookie, fscache_cookie_get_end_access);
 133 }
 134 EXPORT_SYMBOL(fscache_end_cookie_access);
 135
 136 /*
 137  * Pin the cache behind a cookie so that we can access it.
 138  */
 139 static void __fscache_begin_cookie_access(struct fscache_cookie *cookie,
 140                                           enum fscache_access_trace why)
 141 {
 142         int n_accesses;
 143
 144         n_accesses = atomic_inc_return(&cookie->n_accesses);
 145         smp_mb__after_atomic(); /* (Future) read state after is-caching.
 146                                  * Reread n_accesses after is-caching
 147                                  */
 148         trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
 149                              n_accesses, why);
 150 }
 151
 152 /**
 153  * fscache_begin_cookie_access - Pin a cache so data can be accessed
 154  * @cookie: A data file cookie
 155  * @why: An indication of the circumstances of the access for tracing
 156  *
 157  * Attempt to pin the cache to prevent it from going away whilst we're
 158  * accessing data and returns true if successful.  This works as follows:
 159  *
 160  *  (1) If the cookie is not being cached (ie. FSCACHE_COOKIE_IS_CACHING is not
 161  *      set), we return false to indicate access was not permitted.
 162  *
 163  *  (2) If the cookie is being cached, we increment its n_accesses count and
 164  *      then recheck the IS_CACHING flag, ending the access if it got cleared.
 165  *
 166  *  (3) When we end the access, we decrement the cookie's n_accesses and wake
 167  *      up the any waiters if it reaches 0.
 168  *
 169  *  (4) Whilst the cookie is actively being cached, its n_accesses is kept
 170  *      artificially incremented to prevent wakeups from happening.
 171  *
 172  *  (5) When the cache is taken offline or if the cookie is culled, the flag is
 173  *      cleared to prevent new accesses, the cookie's n_accesses is decremented
 174  *      and we wait for it to become 0.
 175  *
 176  * The @why indicator are merely provided for tracing purposes.
 177  */
 178 bool fscache_begin_cookie_access(struct fscache_cookie *cookie,
 179                                  enum fscache_access_trace why)
 180 {
 181         if (!test_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags))
 182                 return false;
 183         __fscache_begin_cookie_access(cookie, why);
 184         if (!test_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags) ||
 185             !fscache_cache_is_live(cookie->volume->cache)) {
 186                 fscache_end_cookie_access(cookie, fscache_access_unlive);
 187                 return false;
 188         }
 189         return true;
 190 }
 191
 192 static inline void wake_up_cookie_state(struct fscache_cookie *cookie)
 193 {
 194         /* Use a barrier to ensure that waiters see the state variable
 195          * change, as spin_unlock doesn't guarantee a barrier.
 196          *
 197          * See comments over wake_up_bit() and waitqueue_active().
 198          */
 199         smp_mb();
 200         wake_up_var(&cookie->state);
 201 }
 202
 203 /*
 204  * Change the state a cookie is at and wake up anyone waiting for that.  Impose
 205  * an ordering between the stuff stored in the cookie and the state member.
 206  * Paired with fscache_cookie_state().
 207  */
 208 static void __fscache_set_cookie_state(struct fscache_cookie *cookie,
 209                                        enum fscache_cookie_state state)
 210 {
 211         smp_store_release(&cookie->state, state);
 212 }
 213
 214 static void fscache_set_cookie_state(struct fscache_cookie *cookie,
 215                                      enum fscache_cookie_state state)
 216 {
 217         spin_lock(&cookie->lock);
 218         __fscache_set_cookie_state(cookie, state);
 219         spin_unlock(&cookie->lock);
 220         wake_up_cookie_state(cookie);
 221 }
 222
 223 /**
 224  * fscache_cookie_lookup_negative - Note negative lookup
 225  * @cookie: The cookie that was being looked up
 226  *
 227  * Note that some part of the metadata path in the cache doesn't exist and so
 228  * we can release any waiting readers in the certain knowledge that there's
 229  * nothing for them to actually read.
 230  *
 231  * This function uses no locking and must only be called from the state machine.
 232  */
 233 void fscache_cookie_lookup_negative(struct fscache_cookie *cookie)
 234 {
 235         set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
 236         fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_CREATING);
 237 }
 238 EXPORT_SYMBOL(fscache_cookie_lookup_negative);
 239
 240 /**
 241  * fscache_resume_after_invalidation - Allow I/O to resume after invalidation
 242  * @cookie: The cookie that was invalidated
 243  *
 244  * Tell fscache that invalidation is sufficiently complete that I/O can be
 245  * allowed again.
 246  */
 247 void fscache_resume_after_invalidation(struct fscache_cookie *cookie)
 248 {
 249         fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_ACTIVE);
 250 }
 251 EXPORT_SYMBOL(fscache_resume_after_invalidation);
 252
 253 /**
 254  * fscache_caching_failed - Report that a failure stopped caching on a cookie
 255  * @cookie: The cookie that was affected
 256  *
 257  * Tell fscache that caching on a cookie needs to be stopped due to some sort
 258  * of failure.
 259  *
 260  * This function uses no locking and must only be called from the state machine.
 261  */
 262 void fscache_caching_failed(struct fscache_cookie *cookie)
 263 {
 264         clear_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags);
 265         fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_FAILED);
 266 }
 267 EXPORT_SYMBOL(fscache_caching_failed);
 268
 269 /*
 270  * Set the index key in a cookie.  The cookie struct has space for a 16-byte
 271  * key plus length and hash, but if that's not big enough, it's instead a
 272  * pointer to a buffer containing 3 bytes of hash, 1 byte of length and then
 273  * the key data.
 274  */
 275 static int fscache_set_key(struct fscache_cookie *cookie,
 276                            const void *index_key, size_t index_key_len)
 277 {
 278         void *buf;
 279         size_t buf_size;
 280
 281         buf_size = round_up(index_key_len, sizeof(__le32));
 282
 283         if (index_key_len > sizeof(cookie->inline_key)) {
 284                 buf = kzalloc(buf_size, GFP_KERNEL);
 285                 if (!buf)
 286                         return -ENOMEM;
 287                 cookie->key = buf;
 288         } else {
 289                 buf = cookie->inline_key;
 290         }
 291
 292         memcpy(buf, index_key, index_key_len);
 293         cookie->key_hash = fscache_hash(cookie->volume->key_hash,
 294                                         buf, buf_size);
 295         return 0;
 296 }
 297
 298 static bool fscache_cookie_same(const struct fscache_cookie *a,
 299                                 const struct fscache_cookie *b)
 300 {
 301         const void *ka, *kb;
 302
 303         if (a->key_hash != b->key_hash ||
 304             a->volume   != b->volume ||
 305             a->key_len  != b->key_len)
 306                 return false;
 307
 308         if (a->key_len <= sizeof(a->inline_key)) {
 309                 ka = &a->inline_key;
 310                 kb = &b->inline_key;
 311         } else {
 312                 ka = a->key;
 313                 kb = b->key;
 314         }
 315         return memcmp(ka, kb, a->key_len) == 0;
 316 }
 317
 318 static atomic_t fscache_cookie_debug_id = ATOMIC_INIT(1);
 319
 320 /*
 321  * Allocate a cookie.
 322  */
 323 static struct fscache_cookie *fscache_alloc_cookie(
 324         struct fscache_volume *volume,
 325         u8 advice,
 326         const void *index_key, size_t index_key_len,
 327         const void *aux_data, size_t aux_data_len,
 328         loff_t object_size)
 329 {
 330         struct fscache_cookie *cookie;
 331
 332         /* allocate and initialise a cookie */
 333         cookie = kmem_cache_zalloc(fscache_cookie_jar, GFP_KERNEL);
 334         if (!cookie)
 335                 return NULL;
 336         fscache_stat(&fscache_n_cookies);
 337
 338         cookie->volume          = volume;
 339         cookie->advice          = advice;
 340         cookie->key_len         = index_key_len;
 341         cookie->aux_len         = aux_data_len;
 342         cookie->object_size     = object_size;
 343         if (object_size == 0)
 344                 __set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
 345
 346         if (fscache_set_key(cookie, index_key, index_key_len) < 0)
 347                 goto nomem;
 348
 349         if (cookie->aux_len <= sizeof(cookie->inline_aux)) {
 350                 memcpy(cookie->inline_aux, aux_data, cookie->aux_len);
 351         } else {
 352                 cookie->aux = kmemdup(aux_data, cookie->aux_len, GFP_KERNEL);
 353                 if (!cookie->aux)
 354                         goto nomem;
 355         }
 356
 357         refcount_set(&cookie->ref, 1);
 358         cookie->debug_id = atomic_inc_return(&fscache_cookie_debug_id);
 359         spin_lock_init(&cookie->lock);
 360         INIT_LIST_HEAD(&cookie->commit_link);
 361         INIT_WORK(&cookie->work, fscache_cookie_worker);
 362         __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
 363
 364         write_lock(&fscache_cookies_lock);
 365         list_add_tail(&cookie->proc_link, &fscache_cookies);
 366         write_unlock(&fscache_cookies_lock);
 367         fscache_see_cookie(cookie, fscache_cookie_new_acquire);
 368         return cookie;
 369
 370 nomem:
 371         fscache_free_cookie(cookie);
 372         return NULL;
 373 }
 374
 375 static void fscache_wait_on_collision(struct fscache_cookie *candidate,
 376                                       struct fscache_cookie *wait_for)
 377 {
 378         enum fscache_cookie_state *statep = &wait_for->state;
 379
 380         wait_var_event_timeout(statep, READ_ONCE(*statep) == FSCACHE_COOKIE_STATE_DROPPED,
 381                                20 * HZ);
 382         if (READ_ONCE(*statep) != FSCACHE_COOKIE_STATE_DROPPED) {
 383                 pr_notice("Potential collision c=%08x old: c=%08x",
 384                           candidate->debug_id, wait_for->debug_id);
 385                 wait_var_event(statep, READ_ONCE(*statep) == FSCACHE_COOKIE_STATE_DROPPED);
 386         }
 387 }
 388
 389 /*
 390  * Attempt to insert the new cookie into the hash.  If there's a collision, we
 391  * wait for the old cookie to complete if it's being relinquished and an error
 392  * otherwise.
 393  */
 394 static bool fscache_hash_cookie(struct fscache_cookie *candidate)
 395 {
 396         struct fscache_cookie *cursor, *wait_for = NULL;
 397         struct hlist_bl_head *h;
 398         struct hlist_bl_node *p;
 399         unsigned int bucket;
 400
 401         bucket = candidate->key_hash & (ARRAY_SIZE(fscache_cookie_hash) - 1);
 402         h = &fscache_cookie_hash[bucket];
 403
 404         hlist_bl_lock(h);
 405         hlist_bl_for_each_entry(cursor, p, h, hash_link) {
 406                 if (fscache_cookie_same(candidate, cursor)) {
 407                         if (!test_bit(FSCACHE_COOKIE_RELINQUISHED, &cursor->flags))
 408                                 goto collision;
 409                         wait_for = fscache_get_cookie(cursor,
 410                                                       fscache_cookie_get_hash_collision);
 411                         break;
 412                 }
 413         }
 414
 415         fscache_get_volume(candidate->volume, fscache_volume_get_cookie);
 416         atomic_inc(&candidate->volume->n_cookies);
 417         hlist_bl_add_head(&candidate->hash_link, h);
 418         set_bit(FSCACHE_COOKIE_IS_HASHED, &candidate->flags);
 419         hlist_bl_unlock(h);
 420
 421         if (wait_for) {
 422                 fscache_wait_on_collision(candidate, wait_for);
 423                 fscache_put_cookie(wait_for, fscache_cookie_put_hash_collision);
 424         }
 425         return true;
 426
 427 collision:
 428         trace_fscache_cookie(cursor->debug_id, refcount_read(&cursor->ref),
 429                              fscache_cookie_collision);
 430         pr_err("Duplicate cookie detected\n");
 431         fscache_print_cookie(cursor, 'O');
 432         fscache_print_cookie(candidate, 'N');
 433         hlist_bl_unlock(h);
 434         return false;
 435 }
 436
 437 /*
 438  * Request a cookie to represent a data storage object within a volume.
 439  *
 440  * We never let on to the netfs about errors.  We may set a negative cookie
 441  * pointer, but that's okay
 442  */
 443 struct fscache_cookie *__fscache_acquire_cookie(
 444         struct fscache_volume *volume,
 445         u8 advice,
 446         const void *index_key, size_t index_key_len,
 447         const void *aux_data, size_t aux_data_len,
 448         loff_t object_size)
 449 {
 450         struct fscache_cookie *cookie;
 451
 452         _enter("V=%x", volume->debug_id);
 453
 454         if (!index_key || !index_key_len || index_key_len > 255 || aux_data_len > 255)
 455                 return NULL;
 456         if (!aux_data || !aux_data_len) {
 457                 aux_data = NULL;
 458                 aux_data_len = 0;
 459         }
 460
 461         fscache_stat(&fscache_n_acquires);
 462
 463         cookie = fscache_alloc_cookie(volume, advice,
 464                                       index_key, index_key_len,
 465                                       aux_data, aux_data_len,
 466                                       object_size);
 467         if (!cookie) {
 468                 fscache_stat(&fscache_n_acquires_oom);
 469                 return NULL;
 470         }
 471
 472         if (!fscache_hash_cookie(cookie)) {
 473                 fscache_see_cookie(cookie, fscache_cookie_discard);
 474                 fscache_free_cookie(cookie);
 475                 return NULL;
 476         }
 477
 478         trace_fscache_acquire(cookie);
 479         fscache_stat(&fscache_n_acquires_ok);
 480         _leave(" = c=%08x", cookie->debug_id);
 481         return cookie;
 482 }
 483 EXPORT_SYMBOL(__fscache_acquire_cookie);
 484
 485 /*
 486  * Prepare a cache object to be written to.
 487  */
 488 static void fscache_prepare_to_write(struct fscache_cookie *cookie)
 489 {
 490         cookie->volume->cache->ops->prepare_to_write(cookie);
 491 }
 492
 493 /*
 494  * Look up a cookie in the cache.
 495  */
 496 static void fscache_perform_lookup(struct fscache_cookie *cookie)
 497 {
 498         enum fscache_access_trace trace = fscache_access_lookup_cookie_end_failed;
 499         bool need_withdraw = false;
 500
 501         _enter("");
 502
 503         if (!cookie->volume->cache_priv) {
 504                 fscache_create_volume(cookie->volume, true);
 505                 if (!cookie->volume->cache_priv) {
 506                         fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
 507                         goto out;
 508                 }
 509         }
 510
 511         if (!cookie->volume->cache->ops->lookup_cookie(cookie)) {
 512                 if (cookie->state != FSCACHE_COOKIE_STATE_FAILED)
 513                         fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
 514                 need_withdraw = true;
 515                 _leave(" [fail]");
 516                 goto out;
 517         }
 518
 519         fscache_see_cookie(cookie, fscache_cookie_see_active);
 520         fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_ACTIVE);
 521         trace = fscache_access_lookup_cookie_end;
 522
 523 out:
 524         fscache_end_cookie_access(cookie, trace);
 525         if (need_withdraw)
 526                 fscache_withdraw_cookie(cookie);
 527         fscache_end_volume_access(cookie->volume, cookie, trace);
 528 }
 529
 530 /*
 531  * Begin the process of looking up a cookie.  We offload the actual process to
 532  * a worker thread.
 533  */
 534 static bool fscache_begin_lookup(struct fscache_cookie *cookie, bool will_modify)
 535 {
 536         if (will_modify) {
 537                 set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags);
 538                 set_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags);
 539         }
 540         if (!fscache_begin_volume_access(cookie->volume, cookie,
 541                                          fscache_access_lookup_cookie))
 542                 return false;
 543
 544         __fscache_begin_cookie_access(cookie, fscache_access_lookup_cookie);
 545         __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_LOOKING_UP);
 546         set_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags);
 547         set_bit(FSCACHE_COOKIE_HAS_BEEN_CACHED, &cookie->flags);
 548         return true;
 549 }
 550
 551 /*
 552  * Start using the cookie for I/O.  This prevents the backing object from being
 553  * reaped by VM pressure.
 554  */
 555 void __fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify)
 556 {
 557         enum fscache_cookie_state state;
 558         bool queue = false;
 559         int n_active;
 560
 561         _enter("c=%08x", cookie->debug_id);
 562
 563         if (WARN(test_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags),
 564                  "Trying to use relinquished cookie\n"))
 565                 return;
 566
 567         spin_lock(&cookie->lock);
 568
 569         n_active = atomic_inc_return(&cookie->n_active);
 570         trace_fscache_active(cookie->debug_id, refcount_read(&cookie->ref),
 571                              n_active, atomic_read(&cookie->n_accesses),
 572                              will_modify ?
 573                              fscache_active_use_modify : fscache_active_use);
 574
 575 again:
 576         state = fscache_cookie_state(cookie);
 577         switch (state) {
 578         case FSCACHE_COOKIE_STATE_QUIESCENT:
 579                 queue = fscache_begin_lookup(cookie, will_modify);
 580                 break;
 581
 582         case FSCACHE_COOKIE_STATE_LOOKING_UP:
 583         case FSCACHE_COOKIE_STATE_CREATING:
 584                 if (will_modify)
 585                         set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags);
 586                 break;
 587         case FSCACHE_COOKIE_STATE_ACTIVE:
 588         case FSCACHE_COOKIE_STATE_INVALIDATING:
 589                 if (will_modify &&
 590                     !test_and_set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags)) {
 591                         set_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags);
 592                         queue = true;
 593                 }
 594                 break;
 595
 596         case FSCACHE_COOKIE_STATE_FAILED:
 597         case FSCACHE_COOKIE_STATE_WITHDRAWING:
 598                 break;
 599
 600         case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
 601                 spin_unlock(&cookie->lock);
 602                 wait_var_event(&cookie->state,
 603                                fscache_cookie_state(cookie) !=
 604                                FSCACHE_COOKIE_STATE_LRU_DISCARDING);
 605                 spin_lock(&cookie->lock);
 606                 goto again;
 607
 608         case FSCACHE_COOKIE_STATE_DROPPED:
 609         case FSCACHE_COOKIE_STATE_RELINQUISHING:
 610                 WARN(1, "Can't use cookie in state %u\n", state);
 611                 break;
 612         }
 613
 614         spin_unlock(&cookie->lock);
 615         if (queue)
 616                 fscache_queue_cookie(cookie, fscache_cookie_get_use_work);
 617         _leave("");
 618 }
 619 EXPORT_SYMBOL(__fscache_use_cookie);
 620
 621 static void fscache_unuse_cookie_locked(struct fscache_cookie *cookie)
 622 {
 623         clear_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags);
 624         if (!test_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags))
 625                 return;
 626
 627         cookie->unused_at = jiffies;
 628         spin_lock(&fscache_cookie_lru_lock);
 629         if (list_empty(&cookie->commit_link)) {
 630                 fscache_get_cookie(cookie, fscache_cookie_get_lru);
 631                 fscache_stat(&fscache_n_cookies_lru);
 632         }
 633         list_move_tail(&cookie->commit_link, &fscache_cookie_lru);
 634
 635         spin_unlock(&fscache_cookie_lru_lock);
 636         timer_reduce(&fscache_cookie_lru_timer,
 637                      jiffies + fscache_lru_cookie_timeout);
 638 }
 639
 640 /*
 641  * Stop using the cookie for I/O.
 642  */
 643 void __fscache_unuse_cookie(struct fscache_cookie *cookie,
 644                             const void *aux_data, const loff_t *object_size)
 645 {
 646         unsigned int debug_id = cookie->debug_id;
 647         unsigned int r = refcount_read(&cookie->ref);
 648         unsigned int a = atomic_read(&cookie->n_accesses);
 649         unsigned int c;
 650
 651         if (aux_data || object_size)
 652                 __fscache_update_cookie(cookie, aux_data, object_size);
 653
 654         /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
 655         c = atomic_fetch_add_unless(&cookie->n_active, -1, 1);
 656         if (c != 1) {
 657                 trace_fscache_active(debug_id, r, c - 1, a, fscache_active_unuse);
 658                 return;
 659         }
 660
 661         spin_lock(&cookie->lock);
 662         r = refcount_read(&cookie->ref);
 663         a = atomic_read(&cookie->n_accesses);
 664         c = atomic_dec_return(&cookie->n_active);
 665         trace_fscache_active(debug_id, r, c, a, fscache_active_unuse);
 666         if (c == 0)
 667                 fscache_unuse_cookie_locked(cookie);
 668         spin_unlock(&cookie->lock);
 669 }
 670 EXPORT_SYMBOL(__fscache_unuse_cookie);
 671
 672 /*
 673  * Perform work upon the cookie, such as committing its cache state,
 674  * relinquishing it or withdrawing the backing cache.  We're protected from the
 675  * cache going away under us as object withdrawal must come through this
 676  * non-reentrant work item.
 677  */
 678 static void fscache_cookie_state_machine(struct fscache_cookie *cookie)
 679 {
 680         enum fscache_cookie_state state;
 681         bool wake = false;
 682
 683         _enter("c=%x", cookie->debug_id);
 684
 685 again:
 686         spin_lock(&cookie->lock);
 687 again_locked:
 688         state = cookie->state;
 689         switch (state) {
 690         case FSCACHE_COOKIE_STATE_QUIESCENT:
 691                 /* The QUIESCENT state is jumped to the LOOKING_UP state by
 692                  * fscache_use_cookie().
 693                  */
 694
 695                 if (atomic_read(&cookie->n_accesses) == 0 &&
 696                     test_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags)) {
 697                         __fscache_set_cookie_state(cookie,
 698                                                    FSCACHE_COOKIE_STATE_RELINQUISHING);
 699                         wake = true;
 700                         goto again_locked;
 701                 }
 702                 break;
 703
 704         case FSCACHE_COOKIE_STATE_LOOKING_UP:
 705                 spin_unlock(&cookie->lock);
 706                 fscache_init_access_gate(cookie);
 707                 fscache_perform_lookup(cookie);
 708                 goto again;
 709
 710         case FSCACHE_COOKIE_STATE_INVALIDATING:
 711                 spin_unlock(&cookie->lock);
 712                 fscache_perform_invalidation(cookie);
 713                 goto again;
 714
 715         case FSCACHE_COOKIE_STATE_ACTIVE:
 716                 if (test_and_clear_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags)) {
 717                         spin_unlock(&cookie->lock);
 718                         fscache_prepare_to_write(cookie);
 719                         spin_lock(&cookie->lock);
 720                 }
 721                 if (test_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags)) {
 722                         __fscache_set_cookie_state(cookie,
 723                                                    FSCACHE_COOKIE_STATE_LRU_DISCARDING);
 724                         wake = true;
 725                         goto again_locked;
 726                 }
 727                 fallthrough;
 728
 729         case FSCACHE_COOKIE_STATE_FAILED:
 730                 if (atomic_read(&cookie->n_accesses) != 0)
 731                         break;
 732                 if (test_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags)) {
 733                         __fscache_set_cookie_state(cookie,
 734                                                    FSCACHE_COOKIE_STATE_RELINQUISHING);
 735                         wake = true;
 736                         goto again_locked;
 737                 }
 738                 if (test_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags)) {
 739                         __fscache_set_cookie_state(cookie,
 740                                                    FSCACHE_COOKIE_STATE_WITHDRAWING);
 741                         wake = true;
 742                         goto again_locked;
 743                 }
 744                 break;
 745
 746         case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
 747         case FSCACHE_COOKIE_STATE_RELINQUISHING:
 748         case FSCACHE_COOKIE_STATE_WITHDRAWING:
 749                 if (cookie->cache_priv) {
 750                         spin_unlock(&cookie->lock);
 751                         cookie->volume->cache->ops->withdraw_cookie(cookie);
 752                         spin_lock(&cookie->lock);
 753                 }
 754
 755                 switch (state) {
 756                 case FSCACHE_COOKIE_STATE_RELINQUISHING:
 757                         fscache_see_cookie(cookie, fscache_cookie_see_relinquish);
 758                         fscache_unhash_cookie(cookie);
 759                         __fscache_set_cookie_state(cookie,
 760                                                    FSCACHE_COOKIE_STATE_DROPPED);
 761                         wake = true;
 762                         goto out;
 763                 case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
 764                         fscache_see_cookie(cookie, fscache_cookie_see_lru_discard);
 765                         break;
 766                 case FSCACHE_COOKIE_STATE_WITHDRAWING:
 767                         fscache_see_cookie(cookie, fscache_cookie_see_withdraw);
 768                         break;
 769                 default:
 770                         BUG();
 771                 }
 772
 773                 clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);
 774                 clear_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags);
 775                 clear_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags);
 776                 clear_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags);
 777                 set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
 778                 __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
 779                 wake = true;
 780                 goto again_locked;
 781
 782         case FSCACHE_COOKIE_STATE_DROPPED:
 783                 break;
 784
 785         default:
 786                 WARN_ONCE(1, "Cookie %x in unexpected state %u\n",
 787                           cookie->debug_id, state);
 788                 break;
 789         }
 790
 791 out:
 792         spin_unlock(&cookie->lock);
 793         if (wake)
 794                 wake_up_cookie_state(cookie);
 795         _leave("");
 796 }
 797
 798 static void fscache_cookie_worker(struct work_struct *work)
 799 {
 800         struct fscache_cookie *cookie = container_of(work, struct fscache_cookie, work);
 801
 802         fscache_see_cookie(cookie, fscache_cookie_see_work);
 803         fscache_cookie_state_machine(cookie);
 804         fscache_put_cookie(cookie, fscache_cookie_put_work);
 805 }
 806
 807 /*
 808  * Wait for the object to become inactive.  The cookie's work item will be
 809  * scheduled when someone transitions n_accesses to 0 - but if someone's
 810  * already done that, schedule it anyway.
 811  */
 812 static void __fscache_withdraw_cookie(struct fscache_cookie *cookie)
 813 {
 814         int n_accesses;
 815         bool unpinned;
 816
 817         unpinned = test_and_clear_bit(FSCACHE_COOKIE_NO_ACCESS_WAKE, &cookie->flags);
 818
 819         /* Need to read the access count after unpinning */
 820         n_accesses = atomic_read(&cookie->n_accesses);
 821         if (unpinned)
 822                 trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
 823                                      n_accesses, fscache_access_cache_unpin);
 824         if (n_accesses == 0)
 825                 fscache_queue_cookie(cookie, fscache_cookie_get_end_access);
 826 }
 827
 828 static void fscache_cookie_lru_do_one(struct fscache_cookie *cookie)
 829 {
 830         fscache_see_cookie(cookie, fscache_cookie_see_lru_do_one);
 831
 832         spin_lock(&cookie->lock);
 833         if (cookie->state != FSCACHE_COOKIE_STATE_ACTIVE ||
 834             time_before(jiffies, cookie->unused_at + fscache_lru_cookie_timeout) ||
 835             atomic_read(&cookie->n_active) > 0) {
 836                 spin_unlock(&cookie->lock);
 837                 fscache_stat(&fscache_n_cookies_lru_removed);
 838         } else {
 839                 set_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags);
 840                 spin_unlock(&cookie->lock);
 841                 fscache_stat(&fscache_n_cookies_lru_expired);
 842                 _debug("lru c=%x", cookie->debug_id);
 843                 __fscache_withdraw_cookie(cookie);
 844         }
 845
 846         fscache_put_cookie(cookie, fscache_cookie_put_lru);
 847 }
 848
 849 static void fscache_cookie_lru_worker(struct work_struct *work)
 850 {
 851         struct fscache_cookie *cookie;
 852         unsigned long unused_at;
 853
 854         spin_lock(&fscache_cookie_lru_lock);
 855
 856         while (!list_empty(&fscache_cookie_lru)) {
 857                 cookie = list_first_entry(&fscache_cookie_lru,
 858                                           struct fscache_cookie, commit_link);
 859                 unused_at = cookie->unused_at + fscache_lru_cookie_timeout;
 860                 if (time_before(jiffies, unused_at)) {
 861                         timer_reduce(&fscache_cookie_lru_timer, unused_at);
 862                         break;
 863                 }
 864
 865                 list_del_init(&cookie->commit_link);
 866                 fscache_stat_d(&fscache_n_cookies_lru);
 867                 spin_unlock(&fscache_cookie_lru_lock);
 868                 fscache_cookie_lru_do_one(cookie);
 869                 spin_lock(&fscache_cookie_lru_lock);
 870         }
 871
 872         spin_unlock(&fscache_cookie_lru_lock);
 873 }
 874
 875 static void fscache_cookie_lru_timed_out(struct timer_list *timer)
 876 {
 877         queue_work(fscache_wq, &fscache_cookie_lru_work);
 878 }
 879
 880 static void fscache_cookie_drop_from_lru(struct fscache_cookie *cookie)
 881 {
 882         bool need_put = false;
 883
 884         if (!list_empty(&cookie->commit_link)) {
 885                 spin_lock(&fscache_cookie_lru_lock);
 886                 if (!list_empty(&cookie->commit_link)) {
 887                         list_del_init(&cookie->commit_link);
 888                         fscache_stat_d(&fscache_n_cookies_lru);
 889                         fscache_stat(&fscache_n_cookies_lru_dropped);
 890                         need_put = true;
 891                 }
 892                 spin_unlock(&fscache_cookie_lru_lock);
 893                 if (need_put)
 894                         fscache_put_cookie(cookie, fscache_cookie_put_lru);
 895         }
 896 }
 897
 898 /*
 899  * Remove a cookie from the hash table.
 900  */
 901 static void fscache_unhash_cookie(struct fscache_cookie *cookie)
 902 {
 903         struct hlist_bl_head *h;
 904         unsigned int bucket;
 905
 906         bucket = cookie->key_hash & (ARRAY_SIZE(fscache_cookie_hash) - 1);
 907         h = &fscache_cookie_hash[bucket];
 908
 909         hlist_bl_lock(h);
 910         hlist_bl_del(&cookie->hash_link);
 911         clear_bit(FSCACHE_COOKIE_IS_HASHED, &cookie->flags);
 912         hlist_bl_unlock(h);
 913         fscache_stat(&fscache_n_relinquishes_dropped);
 914 }
 915
 916 static void fscache_drop_withdraw_cookie(struct fscache_cookie *cookie)
 917 {
 918         fscache_cookie_drop_from_lru(cookie);
 919         __fscache_withdraw_cookie(cookie);
 920 }
 921
 922 /**
 923  * fscache_withdraw_cookie - Mark a cookie for withdrawal
 924  * @cookie: The cookie to be withdrawn.
 925  *
 926  * Allow the cache backend to withdraw the backing for a cookie for its own
 927  * reasons, even if that cookie is in active use.
 928  */
 929 void fscache_withdraw_cookie(struct fscache_cookie *cookie)
 930 {
 931         set_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags);
 932         fscache_drop_withdraw_cookie(cookie);
 933 }
 934 EXPORT_SYMBOL(fscache_withdraw_cookie);
 935
 936 /*
 937  * Allow the netfs to release a cookie back to the cache.
 938  * - the object will be marked as recyclable on disk if retire is true
 939  */
 940 void __fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
 941 {
 942         fscache_stat(&fscache_n_relinquishes);
 943         if (retire)
 944                 fscache_stat(&fscache_n_relinquishes_retire);
 945
 946         _enter("c=%08x{%d},%d",
 947                cookie->debug_id, atomic_read(&cookie->n_active), retire);
 948
 949         if (WARN(test_and_set_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags),
 950                  "Cookie c=%x already relinquished\n", cookie->debug_id))
 951                 return;
 952
 953         if (retire)
 954                 set_bit(FSCACHE_COOKIE_RETIRED, &cookie->flags);
 955         trace_fscache_relinquish(cookie, retire);
 956
 957         ASSERTCMP(atomic_read(&cookie->n_active), ==, 0);
 958         ASSERTCMP(atomic_read(&cookie->volume->n_cookies), >, 0);
 959         atomic_dec(&cookie->volume->n_cookies);
 960
 961         if (test_bit(FSCACHE_COOKIE_HAS_BEEN_CACHED, &cookie->flags)) {
 962                 set_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags);
 963                 fscache_drop_withdraw_cookie(cookie);
 964         } else {
 965                 fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_DROPPED);
 966                 fscache_unhash_cookie(cookie);
 967         }
 968         fscache_put_cookie(cookie, fscache_cookie_put_relinquish);
 969 }
 970 EXPORT_SYMBOL(__fscache_relinquish_cookie);
 971
 972 /*
 973  * Drop a reference to a cookie.
 974  */
 975 void fscache_put_cookie(struct fscache_cookie *cookie,
 976                         enum fscache_cookie_trace where)
 977 {
 978         struct fscache_volume *volume = cookie->volume;
 979         unsigned int cookie_debug_id = cookie->debug_id;
 980         bool zero;
 981         int ref;
 982
 983         zero = __refcount_dec_and_test(&cookie->ref, &ref);
 984         trace_fscache_cookie(cookie_debug_id, ref - 1, where);
 985         if (zero) {
 986                 fscache_free_cookie(cookie);
 987                 fscache_put_volume(volume, fscache_volume_put_cookie);
 988         }
 989 }
 990 EXPORT_SYMBOL(fscache_put_cookie);
 991
 992 /*
 993  * Get a reference to a cookie.
 994  */
 995 struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie,
 996                                           enum fscache_cookie_trace where)
 997 {
 998         int ref;
 999
1000         __refcount_inc(&cookie->ref, &ref);
1001         trace_fscache_cookie(cookie->debug_id, ref + 1, where);
1002         return cookie;
1003 }
1004 EXPORT_SYMBOL(fscache_get_cookie);
1005
1006 /*
1007  * Ask the cache to effect invalidation of a cookie.
1008  */
1009 static void fscache_perform_invalidation(struct fscache_cookie *cookie)
1010 {
1011         if (!cookie->volume->cache->ops->invalidate_cookie(cookie))
1012                 fscache_caching_failed(cookie);
1013         fscache_end_cookie_access(cookie, fscache_access_invalidate_cookie_end);
1014 }
1015
1016 /*
1017  * Invalidate an object.
1018  */
1019 void __fscache_invalidate(struct fscache_cookie *cookie,
1020                           const void *aux_data, loff_t new_size,
1021                           unsigned int flags)
1022 {
1023         bool is_caching;
1024
1025         _enter("c=%x", cookie->debug_id);
1026
1027         fscache_stat(&fscache_n_invalidates);
1028
1029         if (WARN(test_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags),
1030                  "Trying to invalidate relinquished cookie\n"))
1031                 return;
1032
1033         if ((flags & FSCACHE_INVAL_DIO_WRITE) &&
1034             test_and_set_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags))
1035                 return;
1036
1037         spin_lock(&cookie->lock);
1038         set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
1039         fscache_update_aux(cookie, aux_data, &new_size);
1040         cookie->inval_counter++;
1041         trace_fscache_invalidate(cookie, new_size);
1042
1043         switch (cookie->state) {
1044         case FSCACHE_COOKIE_STATE_INVALIDATING: /* is_still_valid will catch it */
1045         default:
1046                 spin_unlock(&cookie->lock);
1047                 _leave(" [no %u]", cookie->state);
1048                 return;
1049
1050         case FSCACHE_COOKIE_STATE_LOOKING_UP:
1051         case FSCACHE_COOKIE_STATE_CREATING:
1052                 spin_unlock(&cookie->lock);
1053                 _leave(" [look %x]", cookie->inval_counter);
1054                 return;
1055
1056         case FSCACHE_COOKIE_STATE_ACTIVE:
1057                 is_caching = fscache_begin_cookie_access(
1058                         cookie, fscache_access_invalidate_cookie);
1059                 if (is_caching)
1060                         __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_INVALIDATING);
1061                 spin_unlock(&cookie->lock);
1062                 wake_up_cookie_state(cookie);
1063
1064                 if (is_caching)
1065                         fscache_queue_cookie(cookie, fscache_cookie_get_inval_work);
1066                 _leave(" [inv]");
1067                 return;
1068         }
1069 }
1070 EXPORT_SYMBOL(__fscache_invalidate);
1071
1072 /*
1073  * Generate a list of extant cookies in /proc/fs/fscache/cookies
1074  */
1075 static int fscache_cookies_seq_show(struct seq_file *m, void *v)
1076 {
1077         struct fscache_cookie *cookie;
1078         unsigned int keylen = 0, auxlen = 0;
1079         u8 *p;
1080
1081         if (v == &fscache_cookies) {
1082                 seq_puts(m,
1083                          "COOKIE   VOLUME   REF ACT ACC S FL DEF             \n"
1084                          "======== ======== === === === = == ================\n"
1085                          );
1086                 return 0;
1087         }
1088
1089         cookie = list_entry(v, struct fscache_cookie, proc_link);
1090
1091         seq_printf(m,
1092                    "%08x %08x %3d %3d %3d %c %02lx",
1093                    cookie->debug_id,
1094                    cookie->volume->debug_id,
1095                    refcount_read(&cookie->ref),
1096                    atomic_read(&cookie->n_active),
1097                    atomic_read(&cookie->n_accesses),
1098                    fscache_cookie_states[cookie->state],
1099                    cookie->flags);
1100
1101         keylen = cookie->key_len;
1102         auxlen = cookie->aux_len;
1103
1104         if (keylen > 0 || auxlen > 0) {
1105                 seq_puts(m, " ");
1106                 p = keylen <= sizeof(cookie->inline_key) ?
1107                         cookie->inline_key : cookie->key;
1108                 for (; keylen > 0; keylen--)
1109                         seq_printf(m, "%02x", *p++);
1110                 if (auxlen > 0) {
1111                         seq_puts(m, ", ");
1112                         p = auxlen <= sizeof(cookie->inline_aux) ?
1113                                 cookie->inline_aux : cookie->aux;
1114                         for (; auxlen > 0; auxlen--)
1115                                 seq_printf(m, "%02x", *p++);
1116                 }
1117         }
1118
1119         seq_puts(m, "\n");
1120         return 0;
1121 }
1122
1123 static void *fscache_cookies_seq_start(struct seq_file *m, loff_t *_pos)
1124         __acquires(fscache_cookies_lock)
1125 {
1126         read_lock(&fscache_cookies_lock);
1127         return seq_list_start_head(&fscache_cookies, *_pos);
1128 }
1129
1130 static void *fscache_cookies_seq_next(struct seq_file *m, void *v, loff_t *_pos)
1131 {
1132         return seq_list_next(v, &fscache_cookies, _pos);
1133 }
1134
1135 static void fscache_cookies_seq_stop(struct seq_file *m, void *v)
1136         __releases(rcu)
1137 {
1138         read_unlock(&fscache_cookies_lock);
1139 }
1140
1141
1142 const struct seq_operations fscache_cookies_seq_ops = {
1143         .start  = fscache_cookies_seq_start,
1144         .next   = fscache_cookies_seq_next,
1145         .stop   = fscache_cookies_seq_stop,
1146         .show   = fscache_cookies_seq_show,
1147 };