lib/lru_cache.c

   1 /*
   2    lru_cache.c
   3
   4    This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
   5
   6    Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
   7    Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
   8    Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
   9
  10    drbd is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 2, or (at your option)
  13    any later version.
  14
  15    drbd is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with drbd; see the file COPYING.  If not, write to
  22    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  23
  24  */
  25
  26 #include <linux/module.h>
  27 #include <linux/bitops.h>
  28 #include <linux/slab.h>
  29 #include <linux/string.h> /* for memset */
  30 #include <linux/seq_file.h> /* for seq_printf */
  31 #include <linux/lru_cache.h>
  32
  33 MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
  34               "Lars Ellenberg <lars@linbit.com>");
  35 MODULE_DESCRIPTION("lru_cache - Track sets of hot objects");
  36 MODULE_LICENSE("GPL");
  37
  38 /* this is developers aid only.
  39  * it catches concurrent access (lack of locking on the users part) */
  40 #define PARANOIA_ENTRY() do {           \
  41         BUG_ON(!lc);                    \
  42         BUG_ON(!lc->nr_elements);       \
  43         BUG_ON(test_and_set_bit(__LC_PARANOIA, &lc->flags)); \
  44 } while (0)
  45
  46 #define RETURN(x...)     do { \
  47         clear_bit_unlock(__LC_PARANOIA, &lc->flags); \
  48         return x ; } while (0)
  49
  50 /* BUG() if e is not one of the elements tracked by lc */
  51 #define PARANOIA_LC_ELEMENT(lc, e) do { \
  52         struct lru_cache *lc_ = (lc);   \
  53         struct lc_element *e_ = (e);    \
  54         unsigned i = e_->lc_index;      \
  55         BUG_ON(i >= lc_->nr_elements);  \
  56         BUG_ON(lc_->lc_element[i] != e_); } while (0)
  57
  58
  59 /* We need to atomically
  60  *  - try to grab the lock (set LC_LOCKED)
  61  *  - only if there is no pending transaction
  62  *    (neither LC_DIRTY nor LC_STARVING is set)
  63  * Because of PARANOIA_ENTRY() above abusing lc->flags as well,
  64  * it is not sufficient to just say
  65  *      return 0 == cmpxchg(&lc->flags, 0, LC_LOCKED);
  66  */
  67 int lc_try_lock(struct lru_cache *lc)
  68 {
  69         unsigned long val;
  70         do {
  71                 val = cmpxchg(&lc->flags, 0, LC_LOCKED);
  72         } while (unlikely (val == LC_PARANOIA));
  73         /* Spin until no-one is inside a PARANOIA_ENTRY()/RETURN() section. */
  74         return 0 == val;
  75 #if 0
  76         /* Alternative approach, spin in case someone enters or leaves a
  77          * PARANOIA_ENTRY()/RETURN() section. */
  78         unsigned long old, new, val;
  79         do {
  80                 old = lc->flags & LC_PARANOIA;
  81                 new = old | LC_LOCKED;
  82                 val = cmpxchg(&lc->flags, old, new);
  83         } while (unlikely (val == (old ^ LC_PARANOIA)));
  84         return old == val;
  85 #endif
  86 }
  87
  88 /**
  89  * lc_create - prepares to track objects in an active set
  90  * @name: descriptive name only used in lc_seq_printf_stats and lc_seq_dump_details
  91  * @max_pending_changes: maximum changes to accumulate until a transaction is required
  92  * @e_count: number of elements allowed to be active simultaneously
  93  * @e_size: size of the tracked objects
  94  * @e_off: offset to the &struct lc_element member in a tracked object
  95  *
  96  * Returns a pointer to a newly initialized struct lru_cache on success,
  97  * or NULL on (allocation) failure.
  98  */
  99 struct lru_cache *lc_create(const char *name, struct kmem_cache *cache,
 100                 unsigned max_pending_changes,
 101                 unsigned e_count, size_t e_size, size_t e_off)
 102 {
 103         struct hlist_head *slot = NULL;
 104         struct lc_element **element = NULL;
 105         struct lru_cache *lc;
 106         struct lc_element *e;
 107         unsigned cache_obj_size = kmem_cache_size(cache);
 108         unsigned i;
 109
 110         WARN_ON(cache_obj_size < e_size);
 111         if (cache_obj_size < e_size)
 112                 return NULL;
 113
 114         /* e_count too big; would probably fail the allocation below anyways.
 115          * for typical use cases, e_count should be few thousand at most. */
 116         if (e_count > LC_MAX_ACTIVE)
 117                 return NULL;
 118
 119         slot = kcalloc(e_count, sizeof(struct hlist_head), GFP_KERNEL);
 120         if (!slot)
 121                 goto out_fail;
 122         element = kzalloc(e_count * sizeof(struct lc_element *), GFP_KERNEL);
 123         if (!element)
 124                 goto out_fail;
 125
 126         lc = kzalloc(sizeof(*lc), GFP_KERNEL);
 127         if (!lc)
 128                 goto out_fail;
 129
 130         INIT_LIST_HEAD(&lc->in_use);
 131         INIT_LIST_HEAD(&lc->lru);
 132         INIT_LIST_HEAD(&lc->free);
 133         INIT_LIST_HEAD(&lc->to_be_changed);
 134
 135         lc->name = name;
 136         lc->element_size = e_size;
 137         lc->element_off = e_off;
 138         lc->nr_elements = e_count;
 139         lc->max_pending_changes = max_pending_changes;
 140         lc->lc_cache = cache;
 141         lc->lc_element = element;
 142         lc->lc_slot = slot;
 143
 144         /* preallocate all objects */
 145         for (i = 0; i < e_count; i++) {
 146                 void *p = kmem_cache_alloc(cache, GFP_KERNEL);
 147                 if (!p)
 148                         break;
 149                 memset(p, 0, lc->element_size);
 150                 e = p + e_off;
 151                 e->lc_index = i;
 152                 e->lc_number = LC_FREE;
 153                 e->lc_new_number = LC_FREE;
 154                 list_add(&e->list, &lc->free);
 155                 element[i] = e;
 156         }
 157         if (i == e_count)
 158                 return lc;
 159
 160         /* else: could not allocate all elements, give up */
 161         for (i--; i; i--) {
 162                 void *p = element[i];
 163                 kmem_cache_free(cache, p - e_off);
 164         }
 165         kfree(lc);
 166 out_fail:
 167         kfree(element);
 168         kfree(slot);
 169         return NULL;
 170 }
 171
 172 static void lc_free_by_index(struct lru_cache *lc, unsigned i)
 173 {
 174         void *p = lc->lc_element[i];
 175         WARN_ON(!p);
 176         if (p) {
 177                 p -= lc->element_off;
 178                 kmem_cache_free(lc->lc_cache, p);
 179         }
 180 }
 181
 182 /**
 183  * lc_destroy - frees memory allocated by lc_create()
 184  * @lc: the lru cache to destroy
 185  */
 186 void lc_destroy(struct lru_cache *lc)
 187 {
 188         unsigned i;
 189         if (!lc)
 190                 return;
 191         for (i = 0; i < lc->nr_elements; i++)
 192                 lc_free_by_index(lc, i);
 193         kfree(lc->lc_element);
 194         kfree(lc->lc_slot);
 195         kfree(lc);
 196 }
 197
 198 /**
 199  * lc_reset - does a full reset for @lc and the hash table slots.
 200  * @lc: the lru cache to operate on
 201  *
 202  * It is roughly the equivalent of re-allocating a fresh lru_cache object,
 203  * basically a short cut to lc_destroy(lc); lc = lc_create(...);
 204  */
 205 void lc_reset(struct lru_cache *lc)
 206 {
 207         unsigned i;
 208
 209         INIT_LIST_HEAD(&lc->in_use);
 210         INIT_LIST_HEAD(&lc->lru);
 211         INIT_LIST_HEAD(&lc->free);
 212         INIT_LIST_HEAD(&lc->to_be_changed);
 213         lc->used = 0;
 214         lc->hits = 0;
 215         lc->misses = 0;
 216         lc->starving = 0;
 217         lc->locked = 0;
 218         lc->changed = 0;
 219         lc->pending_changes = 0;
 220         lc->flags = 0;
 221         memset(lc->lc_slot, 0, sizeof(struct hlist_head) * lc->nr_elements);
 222
 223         for (i = 0; i < lc->nr_elements; i++) {
 224                 struct lc_element *e = lc->lc_element[i];
 225                 void *p = e;
 226                 p -= lc->element_off;
 227                 memset(p, 0, lc->element_size);
 228                 /* re-init it */
 229                 e->lc_index = i;
 230                 e->lc_number = LC_FREE;
 231                 e->lc_new_number = LC_FREE;
 232                 list_add(&e->list, &lc->free);
 233         }
 234 }
 235
 236 /**
 237  * lc_seq_printf_stats - print stats about @lc into @seq
 238  * @seq: the seq_file to print into
 239  * @lc: the lru cache to print statistics of
 240  */
 241 size_t lc_seq_printf_stats(struct seq_file *seq, struct lru_cache *lc)
 242 {
 243         /* NOTE:
 244          * total calls to lc_get are
 245          * (starving + hits + misses)
 246          * misses include "locked" count (update from an other thread in
 247          * progress) and "changed", when this in fact lead to an successful
 248          * update of the cache.
 249          */
 250         return seq_printf(seq, "\t%s: used:%u/%u "
 251                 "hits:%lu misses:%lu starving:%lu locked:%lu changed:%lu\n",
 252                 lc->name, lc->used, lc->nr_elements,
 253                 lc->hits, lc->misses, lc->starving, lc->locked, lc->changed);
 254 }
 255
 256 static struct hlist_head *lc_hash_slot(struct lru_cache *lc, unsigned int enr)
 257 {
 258         return  lc->lc_slot + (enr % lc->nr_elements);
 259 }
 260
 261
 262 static struct lc_element *__lc_find(struct lru_cache *lc, unsigned int enr,
 263                 bool include_changing)
 264 {
 265         struct lc_element *e;
 266
 267         BUG_ON(!lc);
 268         BUG_ON(!lc->nr_elements);
 269         hlist_for_each_entry(e, lc_hash_slot(lc, enr), colision) {
 270                 /* "about to be changed" elements, pending transaction commit,
 271                  * are hashed by their "new number". "Normal" elements have
 272                  * lc_number == lc_new_number. */
 273                 if (e->lc_new_number != enr)
 274                         continue;
 275                 if (e->lc_new_number == e->lc_number || include_changing)
 276                         return e;
 277                 break;
 278         }
 279         return NULL;
 280 }
 281
 282 /**
 283  * lc_find - find element by label, if present in the hash table
 284  * @lc: The lru_cache object
 285  * @enr: element number
 286  *
 287  * Returns the pointer to an element, if the element with the requested
 288  * "label" or element number is present in the hash table,
 289  * or NULL if not found. Does not change the refcnt.
 290  * Ignores elements that are "about to be used", i.e. not yet in the active
 291  * set, but still pending transaction commit.
 292  */
 293 struct lc_element *lc_find(struct lru_cache *lc, unsigned int enr)
 294 {
 295         return __lc_find(lc, enr, 0);
 296 }
 297
 298 /**
 299  * lc_is_used - find element by label
 300  * @lc: The lru_cache object
 301  * @enr: element number
 302  *
 303  * Returns true, if the element with the requested "label" or element number is
 304  * present in the hash table, and is used (refcnt > 0).
 305  * Also finds elements that are not _currently_ used but only "about to be
 306  * used", i.e. on the "to_be_changed" list, pending transaction commit.
 307  */
 308 bool lc_is_used(struct lru_cache *lc, unsigned int enr)
 309 {
 310         struct lc_element *e = __lc_find(lc, enr, 1);
 311         return e && e->refcnt;
 312 }
 313
 314 /**
 315  * lc_del - removes an element from the cache
 316  * @lc: The lru_cache object
 317  * @e: The element to remove
 318  *
 319  * @e must be unused (refcnt == 0). Moves @e from "lru" to "free" list,
 320  * sets @e->enr to %LC_FREE.
 321  */
 322 void lc_del(struct lru_cache *lc, struct lc_element *e)
 323 {
 324         PARANOIA_ENTRY();
 325         PARANOIA_LC_ELEMENT(lc, e);
 326         BUG_ON(e->refcnt);
 327
 328         e->lc_number = e->lc_new_number = LC_FREE;
 329         hlist_del_init(&e->colision);
 330         list_move(&e->list, &lc->free);
 331         RETURN();
 332 }
 333
 334 static struct lc_element *lc_prepare_for_change(struct lru_cache *lc, unsigned new_number)
 335 {
 336         struct list_head *n;
 337         struct lc_element *e;
 338
 339         if (!list_empty(&lc->free))
 340                 n = lc->free.next;
 341         else if (!list_empty(&lc->lru))
 342                 n = lc->lru.prev;
 343         else
 344                 return NULL;
 345
 346         e = list_entry(n, struct lc_element, list);
 347         PARANOIA_LC_ELEMENT(lc, e);
 348
 349         e->lc_new_number = new_number;
 350         if (!hlist_unhashed(&e->colision))
 351                 __hlist_del(&e->colision);
 352         hlist_add_head(&e->colision, lc_hash_slot(lc, new_number));
 353         list_move(&e->list, &lc->to_be_changed);
 354
 355         return e;
 356 }
 357
 358 static int lc_unused_element_available(struct lru_cache *lc)
 359 {
 360         if (!list_empty(&lc->free))
 361                 return 1; /* something on the free list */
 362         if (!list_empty(&lc->lru))
 363                 return 1;  /* something to evict */
 364
 365         return 0;
 366 }
 367
 368 /* used as internal flags to __lc_get */
 369 enum {
 370         LC_GET_MAY_CHANGE = 1,
 371         LC_GET_MAY_USE_UNCOMMITTED = 2,
 372 };
 373
 374 static struct lc_element *__lc_get(struct lru_cache *lc, unsigned int enr, unsigned int flags)
 375 {
 376         struct lc_element *e;
 377
 378         PARANOIA_ENTRY();
 379         if (lc->flags & LC_STARVING) {
 380                 ++lc->starving;
 381                 RETURN(NULL);
 382         }
 383
 384         e = __lc_find(lc, enr, 1);
 385         /* if lc_new_number != lc_number,
 386          * this enr is currently being pulled in already,
 387          * and will be available once the pending transaction
 388          * has been committed. */
 389         if (e) {
 390                 if (e->lc_new_number != e->lc_number) {
 391                         /* It has been found above, but on the "to_be_changed"
 392                          * list, not yet committed.  Don't pull it in twice,
 393                          * wait for the transaction, then try again...
 394                          */
 395                         if (!(flags & LC_GET_MAY_USE_UNCOMMITTED))
 396                                 RETURN(NULL);
 397                         /* ... unless the caller is aware of the implications,
 398                          * probably preparing a cumulative transaction. */
 399                         ++e->refcnt;
 400                         ++lc->hits;
 401                         RETURN(e);
 402                 }
 403                 /* else: lc_new_number == lc_number; a real hit. */
 404                 ++lc->hits;
 405                 if (e->refcnt++ == 0)
 406                         lc->used++;
 407                 list_move(&e->list, &lc->in_use); /* Not evictable... */
 408                 RETURN(e);
 409         }
 410         /* e == NULL */
 411
 412         ++lc->misses;
 413         if (!(flags & LC_GET_MAY_CHANGE))
 414                 RETURN(NULL);
 415
 416         /* To avoid races with lc_try_lock(), first, mark us dirty
 417          * (using test_and_set_bit, as it implies memory barriers), ... */
 418         test_and_set_bit(__LC_DIRTY, &lc->flags);
 419
 420         /* ... only then check if it is locked anyways. If lc_unlock clears
 421          * the dirty bit again, that's not a problem, we will come here again.
 422          */
 423         if (test_bit(__LC_LOCKED, &lc->flags)) {
 424                 ++lc->locked;
 425                 RETURN(NULL);
 426         }
 427
 428         /* In case there is nothing available and we can not kick out
 429          * the LRU element, we have to wait ...
 430          */
 431         if (!lc_unused_element_available(lc)) {
 432                 __set_bit(__LC_STARVING, &lc->flags);
 433                 RETURN(NULL);
 434         }
 435
 436         /* It was not present in the active set.  We are going to recycle an
 437          * unused (or even "free") element, but we won't accumulate more than
 438          * max_pending_changes changes.  */
 439         if (lc->pending_changes >= lc->max_pending_changes)
 440                 RETURN(NULL);
 441
 442         e = lc_prepare_for_change(lc, enr);
 443         BUG_ON(!e);
 444
 445         clear_bit(__LC_STARVING, &lc->flags);
 446         BUG_ON(++e->refcnt != 1);
 447         lc->used++;
 448         lc->pending_changes++;
 449
 450         RETURN(e);
 451 }
 452
 453 /**
 454  * lc_get - get element by label, maybe change the active set
 455  * @lc: the lru cache to operate on
 456  * @enr: the label to look up
 457  *
 458  * Finds an element in the cache, increases its usage count,
 459  * "touches" and returns it.
 460  *
 461  * In case the requested number is not present, it needs to be added to the
 462  * cache. Therefore it is possible that an other element becomes evicted from
 463  * the cache. In either case, the user is notified so he is able to e.g. keep
 464  * a persistent log of the cache changes, and therefore the objects in use.
 465  *
 466  * Return values:
 467  *  NULL
 468  *     The cache was marked %LC_STARVING,
 469  *     or the requested label was not in the active set
 470  *     and a changing transaction is still pending (@lc was marked %LC_DIRTY).
 471  *     Or no unused or free element could be recycled (@lc will be marked as
 472  *     %LC_STARVING, blocking further lc_get() operations).
 473  *
 474  *  pointer to the element with the REQUESTED element number.
 475  *     In this case, it can be used right away
 476  *
 477  *  pointer to an UNUSED element with some different element number,
 478  *          where that different number may also be %LC_FREE.
 479  *
 480  *          In this case, the cache is marked %LC_DIRTY,
 481  *          so lc_try_lock() will no longer succeed.
 482  *          The returned element pointer is moved to the "to_be_changed" list,
 483  *          and registered with the new element number on the hash collision chains,
 484  *          so it is possible to pick it up from lc_is_used().
 485  *          Up to "max_pending_changes" (see lc_create()) can be accumulated.
 486  *          The user now should do whatever housekeeping is necessary,
 487  *          typically serialize on lc_try_lock_for_transaction(), then call
 488  *          lc_committed(lc) and lc_unlock(), to finish the change.
 489  *
 490  * NOTE: The user needs to check the lc_number on EACH use, so he recognizes
 491  *       any cache set change.
 492  */
 493 struct lc_element *lc_get(struct lru_cache *lc, unsigned int enr)
 494 {
 495         return __lc_get(lc, enr, LC_GET_MAY_CHANGE);
 496 }
 497
 498 /**
 499  * lc_get_cumulative - like lc_get; also finds to-be-changed elements
 500  * @lc: the lru cache to operate on
 501  * @enr: the label to look up
 502  *
 503  * Unlike lc_get this also returns the element for @enr, if it is belonging to
 504  * a pending transaction, so the return values are like for lc_get(),
 505  * plus:
 506  *
 507  * pointer to an element already on the "to_be_changed" list.
 508  *      In this case, the cache was already marked %LC_DIRTY.
 509  *
 510  * Caller needs to make sure that the pending transaction is completed,
 511  * before proceeding to actually use this element.
 512  */
 513 struct lc_element *lc_get_cumulative(struct lru_cache *lc, unsigned int enr)
 514 {
 515         return __lc_get(lc, enr, LC_GET_MAY_CHANGE|LC_GET_MAY_USE_UNCOMMITTED);
 516 }
 517
 518 /**
 519  * lc_try_get - get element by label, if present; do not change the active set
 520  * @lc: the lru cache to operate on
 521  * @enr: the label to look up
 522  *
 523  * Finds an element in the cache, increases its usage count,
 524  * "touches" and returns it.
 525  *
 526  * Return values:
 527  *  NULL
 528  *     The cache was marked %LC_STARVING,
 529  *     or the requested label was not in the active set
 530  *
 531  *  pointer to the element with the REQUESTED element number.
 532  *     In this case, it can be used right away
 533  */
 534 struct lc_element *lc_try_get(struct lru_cache *lc, unsigned int enr)
 535 {
 536         return __lc_get(lc, enr, 0);
 537 }
 538
 539 /**
 540  * lc_committed - tell @lc that pending changes have been recorded
 541  * @lc: the lru cache to operate on
 542  *
 543  * User is expected to serialize on explicit lc_try_lock_for_transaction()
 544  * before the transaction is started, and later needs to lc_unlock() explicitly
 545  * as well.
 546  */
 547 void lc_committed(struct lru_cache *lc)
 548 {
 549         struct lc_element *e, *tmp;
 550
 551         PARANOIA_ENTRY();
 552         list_for_each_entry_safe(e, tmp, &lc->to_be_changed, list) {
 553                 /* count number of changes, not number of transactions */
 554                 ++lc->changed;
 555                 e->lc_number = e->lc_new_number;
 556                 list_move(&e->list, &lc->in_use);
 557         }
 558         lc->pending_changes = 0;
 559         RETURN();
 560 }
 561
 562
 563 /**
 564  * lc_put - give up refcnt of @e
 565  * @lc: the lru cache to operate on
 566  * @e: the element to put
 567  *
 568  * If refcnt reaches zero, the element is moved to the lru list,
 569  * and a %LC_STARVING (if set) is cleared.
 570  * Returns the new (post-decrement) refcnt.
 571  */
 572 unsigned int lc_put(struct lru_cache *lc, struct lc_element *e)
 573 {
 574         PARANOIA_ENTRY();
 575         PARANOIA_LC_ELEMENT(lc, e);
 576         BUG_ON(e->refcnt == 0);
 577         BUG_ON(e->lc_number != e->lc_new_number);
 578         if (--e->refcnt == 0) {
 579                 /* move it to the front of LRU. */
 580                 list_move(&e->list, &lc->lru);
 581                 lc->used--;
 582                 clear_bit_unlock(__LC_STARVING, &lc->flags);
 583         }
 584         RETURN(e->refcnt);
 585 }
 586
 587 /**
 588  * lc_element_by_index
 589  * @lc: the lru cache to operate on
 590  * @i: the index of the element to return
 591  */
 592 struct lc_element *lc_element_by_index(struct lru_cache *lc, unsigned i)
 593 {
 594         BUG_ON(i >= lc->nr_elements);
 595         BUG_ON(lc->lc_element[i] == NULL);
 596         BUG_ON(lc->lc_element[i]->lc_index != i);
 597         return lc->lc_element[i];
 598 }
 599
 600 /**
 601  * lc_index_of
 602  * @lc: the lru cache to operate on
 603  * @e: the element to query for its index position in lc->element
 604  */
 605 unsigned int lc_index_of(struct lru_cache *lc, struct lc_element *e)
 606 {
 607         PARANOIA_LC_ELEMENT(lc, e);
 608         return e->lc_index;
 609 }
 610
 611 /**
 612  * lc_set - associate index with label
 613  * @lc: the lru cache to operate on
 614  * @enr: the label to set
 615  * @index: the element index to associate label with.
 616  *
 617  * Used to initialize the active set to some previously recorded state.
 618  */
 619 void lc_set(struct lru_cache *lc, unsigned int enr, int index)
 620 {
 621         struct lc_element *e;
 622         struct list_head *lh;
 623
 624         if (index < 0 || index >= lc->nr_elements)
 625                 return;
 626
 627         e = lc_element_by_index(lc, index);
 628         BUG_ON(e->lc_number != e->lc_new_number);
 629         BUG_ON(e->refcnt != 0);
 630
 631         e->lc_number = e->lc_new_number = enr;
 632         hlist_del_init(&e->colision);
 633         if (enr == LC_FREE)
 634                 lh = &lc->free;
 635         else {
 636                 hlist_add_head(&e->colision, lc_hash_slot(lc, enr));
 637                 lh = &lc->lru;
 638         }
 639         list_move(&e->list, lh);
 640 }
 641
 642 /**
 643  * lc_dump - Dump a complete LRU cache to seq in textual form.
 644  * @lc: the lru cache to operate on
 645  * @seq: the &struct seq_file pointer to seq_printf into
 646  * @utext: user supplied additional "heading" or other info
 647  * @detail: function pointer the user may provide to dump further details
 648  * of the object the lc_element is embedded in. May be NULL.
 649  * Note: a leading space ' ' and trailing newline '\n' is implied.
 650  */
 651 void lc_seq_dump_details(struct seq_file *seq, struct lru_cache *lc, char *utext,
 652              void (*detail) (struct seq_file *, struct lc_element *))
 653 {
 654         unsigned int nr_elements = lc->nr_elements;
 655         struct lc_element *e;
 656         int i;
 657
 658         seq_printf(seq, "\tnn: lc_number (new nr) refcnt %s\n ", utext);
 659         for (i = 0; i < nr_elements; i++) {
 660                 e = lc_element_by_index(lc, i);
 661                 if (e->lc_number != e->lc_new_number)
 662                         seq_printf(seq, "\t%5d: %6d %8d %6d ",
 663                                 i, e->lc_number, e->lc_new_number, e->refcnt);
 664                 else
 665                         seq_printf(seq, "\t%5d: %6d %-8s %6d ",
 666                                 i, e->lc_number, "-\"-", e->refcnt);
 667                 if (detail)
 668                         detail(seq, e);
 669                 seq_putc(seq, '\n');
 670         }
 671 }
 672
 673 EXPORT_SYMBOL(lc_create);
 674 EXPORT_SYMBOL(lc_reset);
 675 EXPORT_SYMBOL(lc_destroy);
 676 EXPORT_SYMBOL(lc_set);
 677 EXPORT_SYMBOL(lc_del);
 678 EXPORT_SYMBOL(lc_try_get);
 679 EXPORT_SYMBOL(lc_find);
 680 EXPORT_SYMBOL(lc_get);
 681 EXPORT_SYMBOL(lc_put);
 682 EXPORT_SYMBOL(lc_committed);
 683 EXPORT_SYMBOL(lc_element_by_index);
 684 EXPORT_SYMBOL(lc_index_of);
 685 EXPORT_SYMBOL(lc_seq_printf_stats);
 686 EXPORT_SYMBOL(lc_seq_dump_details);
 687 EXPORT_SYMBOL(lc_try_lock);
 688 EXPORT_SYMBOL(lc_is_used);
 689 EXPORT_SYMBOL(lc_get_cumulative);