The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

FreeBSD/Linux Kernel Cross Reference
sys/fs/mbcache.c

Version: -  FREEBSD  -  FREEBSD-13-STABLE  -  FREEBSD-13-0  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  l41  -  OPENBSD  -  linux-2.6  -  MK84  -  PLAN9  -  xnu-8792 
SearchContext: -  none  -  3  -  10 

    1 /*
    2  * linux/fs/mbcache.c
    3  * (C) 2001-2002 Andreas Gruenbacher, <a.gruenbacher@computer.org>
    4  */
    5 
    6 /*
    7  * Filesystem Meta Information Block Cache (mbcache)
    8  *
    9  * The mbcache caches blocks of block devices that need to be located
   10  * by their device/block number, as well as by other criteria (such
   11  * as the block's contents).
   12  *
   13  * There can only be one cache entry in a cache per device and block number.
   14  * Additional indexes need not be unique in this sense. The number of
   15  * additional indexes (=other criteria) can be hardwired at compile time
   16  * or specified at cache create time.
   17  *
   18  * Each cache entry is of fixed size. An entry may be `valid' or `invalid'
   19  * in the cache. A valid entry is in the main hash tables of the cache,
   20  * and may also be in the lru list. An invalid entry is not in any hashes
   21  * or lists.
   22  *
   23  * A valid cache entry is only in the lru list if no handles refer to it.
   24  * Invalid cache entries will be freed when the last handle to the cache
   25  * entry is released. Entries that cannot be freed immediately are put
   26  * back on the lru list.
   27  */
   28 
   29 #include <linux/kernel.h>
   30 #include <linux/module.h>
   31 
   32 #include <linux/hash.h>
   33 #include <linux/fs.h>
   34 #include <linux/mm.h>
   35 #include <linux/slab.h>
   36 #include <linux/sched.h>
   37 #include <linux/init.h>
   38 #include <linux/mbcache.h>
   39 
   40 
   41 #ifdef MB_CACHE_DEBUG
   42 # define mb_debug(f...) do { \
   43                 printk(KERN_DEBUG f); \
   44                 printk("\n"); \
   45         } while (0)
   46 #define mb_assert(c) do { if (!(c)) \
   47                 printk(KERN_ERR "assertion " #c " failed\n"); \
   48         } while(0)
   49 #else
   50 # define mb_debug(f...) do { } while(0)
   51 # define mb_assert(c) do { } while(0)
   52 #endif
   53 #define mb_error(f...) do { \
   54                 printk(KERN_ERR f); \
   55                 printk("\n"); \
   56         } while(0)
   57 
   58 #define MB_CACHE_WRITER ((unsigned short)~0U >> 1)
   59 
   60 static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue);
   61                 
   62 MODULE_AUTHOR("Andreas Gruenbacher <a.gruenbacher@computer.org>");
   63 MODULE_DESCRIPTION("Meta block cache (for extended attributes)");
   64 MODULE_LICENSE("GPL");
   65 
   66 EXPORT_SYMBOL(mb_cache_create);
   67 EXPORT_SYMBOL(mb_cache_shrink);
   68 EXPORT_SYMBOL(mb_cache_destroy);
   69 EXPORT_SYMBOL(mb_cache_entry_alloc);
   70 EXPORT_SYMBOL(mb_cache_entry_insert);
   71 EXPORT_SYMBOL(mb_cache_entry_release);
   72 EXPORT_SYMBOL(mb_cache_entry_free);
   73 EXPORT_SYMBOL(mb_cache_entry_get);
   74 #if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
   75 EXPORT_SYMBOL(mb_cache_entry_find_first);
   76 EXPORT_SYMBOL(mb_cache_entry_find_next);
   77 #endif
   78 
   79 /*
   80  * Global data: list of all mbcache's, lru list, and a spinlock for
   81  * accessing cache data structures on SMP machines. The lru list is
   82  * global across all mbcaches.
   83  */
   84 
   85 static LIST_HEAD(mb_cache_list);
   86 static LIST_HEAD(mb_cache_lru_list);
   87 static DEFINE_SPINLOCK(mb_cache_spinlock);
   88 
   89 /*
   90  * What the mbcache registers as to get shrunk dynamically.
   91  */
   92 
   93 static int mb_cache_shrink_fn(struct shrinker *shrink,
   94                               struct shrink_control *sc);
   95 
   96 static struct shrinker mb_cache_shrinker = {
   97         .shrink = mb_cache_shrink_fn,
   98         .seeks = DEFAULT_SEEKS,
   99 };
  100 
  101 static inline int
  102 __mb_cache_entry_is_hashed(struct mb_cache_entry *ce)
  103 {
  104         return !list_empty(&ce->e_block_list);
  105 }
  106 
  107 
  108 static void
  109 __mb_cache_entry_unhash(struct mb_cache_entry *ce)
  110 {
  111         if (__mb_cache_entry_is_hashed(ce)) {
  112                 list_del_init(&ce->e_block_list);
  113                 list_del(&ce->e_index.o_list);
  114         }
  115 }
  116 
  117 
  118 static void
  119 __mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask)
  120 {
  121         struct mb_cache *cache = ce->e_cache;
  122 
  123         mb_assert(!(ce->e_used || ce->e_queued));
  124         kmem_cache_free(cache->c_entry_cache, ce);
  125         atomic_dec(&cache->c_entry_count);
  126 }
  127 
  128 
  129 static void
  130 __mb_cache_entry_release_unlock(struct mb_cache_entry *ce)
  131         __releases(mb_cache_spinlock)
  132 {
  133         /* Wake up all processes queuing for this cache entry. */
  134         if (ce->e_queued)
  135                 wake_up_all(&mb_cache_queue);
  136         if (ce->e_used >= MB_CACHE_WRITER)
  137                 ce->e_used -= MB_CACHE_WRITER;
  138         ce->e_used--;
  139         if (!(ce->e_used || ce->e_queued)) {
  140                 if (!__mb_cache_entry_is_hashed(ce))
  141                         goto forget;
  142                 mb_assert(list_empty(&ce->e_lru_list));
  143                 list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
  144         }
  145         spin_unlock(&mb_cache_spinlock);
  146         return;
  147 forget:
  148         spin_unlock(&mb_cache_spinlock);
  149         __mb_cache_entry_forget(ce, GFP_KERNEL);
  150 }
  151 
  152 
  153 /*
  154  * mb_cache_shrink_fn()  memory pressure callback
  155  *
  156  * This function is called by the kernel memory management when memory
  157  * gets low.
  158  *
  159  * @shrink: (ignored)
  160  * @sc: shrink_control passed from reclaim
  161  *
  162  * Returns the number of objects which are present in the cache.
  163  */
  164 static int
  165 mb_cache_shrink_fn(struct shrinker *shrink, struct shrink_control *sc)
  166 {
  167         LIST_HEAD(free_list);
  168         struct mb_cache *cache;
  169         struct mb_cache_entry *entry, *tmp;
  170         int count = 0;
  171         int nr_to_scan = sc->nr_to_scan;
  172         gfp_t gfp_mask = sc->gfp_mask;
  173 
  174         mb_debug("trying to free %d entries", nr_to_scan);
  175         spin_lock(&mb_cache_spinlock);
  176         while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) {
  177                 struct mb_cache_entry *ce =
  178                         list_entry(mb_cache_lru_list.next,
  179                                    struct mb_cache_entry, e_lru_list);
  180                 list_move_tail(&ce->e_lru_list, &free_list);
  181                 __mb_cache_entry_unhash(ce);
  182         }
  183         list_for_each_entry(cache, &mb_cache_list, c_cache_list) {
  184                 mb_debug("cache %s (%d)", cache->c_name,
  185                           atomic_read(&cache->c_entry_count));
  186                 count += atomic_read(&cache->c_entry_count);
  187         }
  188         spin_unlock(&mb_cache_spinlock);
  189         list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) {
  190                 __mb_cache_entry_forget(entry, gfp_mask);
  191         }
  192         return (count / 100) * sysctl_vfs_cache_pressure;
  193 }
  194 
  195 
  196 /*
  197  * mb_cache_create()  create a new cache
  198  *
  199  * All entries in one cache are equal size. Cache entries may be from
  200  * multiple devices. If this is the first mbcache created, registers
  201  * the cache with kernel memory management. Returns NULL if no more
  202  * memory was available.
  203  *
  204  * @name: name of the cache (informal)
  205  * @bucket_bits: log2(number of hash buckets)
  206  */
  207 struct mb_cache *
  208 mb_cache_create(const char *name, int bucket_bits)
  209 {
  210         int n, bucket_count = 1 << bucket_bits;
  211         struct mb_cache *cache = NULL;
  212 
  213         cache = kmalloc(sizeof(struct mb_cache), GFP_KERNEL);
  214         if (!cache)
  215                 return NULL;
  216         cache->c_name = name;
  217         atomic_set(&cache->c_entry_count, 0);
  218         cache->c_bucket_bits = bucket_bits;
  219         cache->c_block_hash = kmalloc(bucket_count * sizeof(struct list_head),
  220                                       GFP_KERNEL);
  221         if (!cache->c_block_hash)
  222                 goto fail;
  223         for (n=0; n<bucket_count; n++)
  224                 INIT_LIST_HEAD(&cache->c_block_hash[n]);
  225         cache->c_index_hash = kmalloc(bucket_count * sizeof(struct list_head),
  226                                       GFP_KERNEL);
  227         if (!cache->c_index_hash)
  228                 goto fail;
  229         for (n=0; n<bucket_count; n++)
  230                 INIT_LIST_HEAD(&cache->c_index_hash[n]);
  231         cache->c_entry_cache = kmem_cache_create(name,
  232                 sizeof(struct mb_cache_entry), 0,
  233                 SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL);
  234         if (!cache->c_entry_cache)
  235                 goto fail2;
  236 
  237         /*
  238          * Set an upper limit on the number of cache entries so that the hash
  239          * chains won't grow too long.
  240          */
  241         cache->c_max_entries = bucket_count << 4;
  242 
  243         spin_lock(&mb_cache_spinlock);
  244         list_add(&cache->c_cache_list, &mb_cache_list);
  245         spin_unlock(&mb_cache_spinlock);
  246         return cache;
  247 
  248 fail2:
  249         kfree(cache->c_index_hash);
  250 
  251 fail:
  252         kfree(cache->c_block_hash);
  253         kfree(cache);
  254         return NULL;
  255 }
  256 
  257 
  258 /*
  259  * mb_cache_shrink()
  260  *
  261  * Removes all cache entries of a device from the cache. All cache entries
  262  * currently in use cannot be freed, and thus remain in the cache. All others
  263  * are freed.
  264  *
  265  * @bdev: which device's cache entries to shrink
  266  */
  267 void
  268 mb_cache_shrink(struct block_device *bdev)
  269 {
  270         LIST_HEAD(free_list);
  271         struct list_head *l, *ltmp;
  272 
  273         spin_lock(&mb_cache_spinlock);
  274         list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
  275                 struct mb_cache_entry *ce =
  276                         list_entry(l, struct mb_cache_entry, e_lru_list);
  277                 if (ce->e_bdev == bdev) {
  278                         list_move_tail(&ce->e_lru_list, &free_list);
  279                         __mb_cache_entry_unhash(ce);
  280                 }
  281         }
  282         spin_unlock(&mb_cache_spinlock);
  283         list_for_each_safe(l, ltmp, &free_list) {
  284                 __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
  285                                                    e_lru_list), GFP_KERNEL);
  286         }
  287 }
  288 
  289 
  290 /*
  291  * mb_cache_destroy()
  292  *
  293  * Shrinks the cache to its minimum possible size (hopefully 0 entries),
  294  * and then destroys it. If this was the last mbcache, un-registers the
  295  * mbcache from kernel memory management.
  296  */
  297 void
  298 mb_cache_destroy(struct mb_cache *cache)
  299 {
  300         LIST_HEAD(free_list);
  301         struct list_head *l, *ltmp;
  302 
  303         spin_lock(&mb_cache_spinlock);
  304         list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
  305                 struct mb_cache_entry *ce =
  306                         list_entry(l, struct mb_cache_entry, e_lru_list);
  307                 if (ce->e_cache == cache) {
  308                         list_move_tail(&ce->e_lru_list, &free_list);
  309                         __mb_cache_entry_unhash(ce);
  310                 }
  311         }
  312         list_del(&cache->c_cache_list);
  313         spin_unlock(&mb_cache_spinlock);
  314 
  315         list_for_each_safe(l, ltmp, &free_list) {
  316                 __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
  317                                                    e_lru_list), GFP_KERNEL);
  318         }
  319 
  320         if (atomic_read(&cache->c_entry_count) > 0) {
  321                 mb_error("cache %s: %d orphaned entries",
  322                           cache->c_name,
  323                           atomic_read(&cache->c_entry_count));
  324         }
  325 
  326         kmem_cache_destroy(cache->c_entry_cache);
  327 
  328         kfree(cache->c_index_hash);
  329         kfree(cache->c_block_hash);
  330         kfree(cache);
  331 }
  332 
  333 /*
  334  * mb_cache_entry_alloc()
  335  *
  336  * Allocates a new cache entry. The new entry will not be valid initially,
  337  * and thus cannot be looked up yet. It should be filled with data, and
  338  * then inserted into the cache using mb_cache_entry_insert(). Returns NULL
  339  * if no more memory was available.
  340  */
  341 struct mb_cache_entry *
  342 mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
  343 {
  344         struct mb_cache_entry *ce = NULL;
  345 
  346         if (atomic_read(&cache->c_entry_count) >= cache->c_max_entries) {
  347                 spin_lock(&mb_cache_spinlock);
  348                 if (!list_empty(&mb_cache_lru_list)) {
  349                         ce = list_entry(mb_cache_lru_list.next,
  350                                         struct mb_cache_entry, e_lru_list);
  351                         list_del_init(&ce->e_lru_list);
  352                         __mb_cache_entry_unhash(ce);
  353                 }
  354                 spin_unlock(&mb_cache_spinlock);
  355         }
  356         if (!ce) {
  357                 ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);
  358                 if (!ce)
  359                         return NULL;
  360                 atomic_inc(&cache->c_entry_count);
  361                 INIT_LIST_HEAD(&ce->e_lru_list);
  362                 INIT_LIST_HEAD(&ce->e_block_list);
  363                 ce->e_cache = cache;
  364                 ce->e_queued = 0;
  365         }
  366         ce->e_used = 1 + MB_CACHE_WRITER;
  367         return ce;
  368 }
  369 
  370 
  371 /*
  372  * mb_cache_entry_insert()
  373  *
  374  * Inserts an entry that was allocated using mb_cache_entry_alloc() into
  375  * the cache. After this, the cache entry can be looked up, but is not yet
  376  * in the lru list as the caller still holds a handle to it. Returns 0 on
  377  * success, or -EBUSY if a cache entry for that device + inode exists
  378  * already (this may happen after a failed lookup, but when another process
  379  * has inserted the same cache entry in the meantime).
  380  *
  381  * @bdev: device the cache entry belongs to
  382  * @block: block number
  383  * @key: lookup key
  384  */
  385 int
  386 mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,
  387                       sector_t block, unsigned int key)
  388 {
  389         struct mb_cache *cache = ce->e_cache;
  390         unsigned int bucket;
  391         struct list_head *l;
  392         int error = -EBUSY;
  393 
  394         bucket = hash_long((unsigned long)bdev + (block & 0xffffffff), 
  395                            cache->c_bucket_bits);
  396         spin_lock(&mb_cache_spinlock);
  397         list_for_each_prev(l, &cache->c_block_hash[bucket]) {
  398                 struct mb_cache_entry *ce =
  399                         list_entry(l, struct mb_cache_entry, e_block_list);
  400                 if (ce->e_bdev == bdev && ce->e_block == block)
  401                         goto out;
  402         }
  403         __mb_cache_entry_unhash(ce);
  404         ce->e_bdev = bdev;
  405         ce->e_block = block;
  406         list_add(&ce->e_block_list, &cache->c_block_hash[bucket]);
  407         ce->e_index.o_key = key;
  408         bucket = hash_long(key, cache->c_bucket_bits);
  409         list_add(&ce->e_index.o_list, &cache->c_index_hash[bucket]);
  410         error = 0;
  411 out:
  412         spin_unlock(&mb_cache_spinlock);
  413         return error;
  414 }
  415 
  416 
  417 /*
  418  * mb_cache_entry_release()
  419  *
  420  * Release a handle to a cache entry. When the last handle to a cache entry
  421  * is released it is either freed (if it is invalid) or otherwise inserted
  422  * in to the lru list.
  423  */
  424 void
  425 mb_cache_entry_release(struct mb_cache_entry *ce)
  426 {
  427         spin_lock(&mb_cache_spinlock);
  428         __mb_cache_entry_release_unlock(ce);
  429 }
  430 
  431 
  432 /*
  433  * mb_cache_entry_free()
  434  *
  435  * This is equivalent to the sequence mb_cache_entry_takeout() --
  436  * mb_cache_entry_release().
  437  */
  438 void
  439 mb_cache_entry_free(struct mb_cache_entry *ce)
  440 {
  441         spin_lock(&mb_cache_spinlock);
  442         mb_assert(list_empty(&ce->e_lru_list));
  443         __mb_cache_entry_unhash(ce);
  444         __mb_cache_entry_release_unlock(ce);
  445 }
  446 
  447 
  448 /*
  449  * mb_cache_entry_get()
  450  *
  451  * Get a cache entry  by device / block number. (There can only be one entry
  452  * in the cache per device and block.) Returns NULL if no such cache entry
  453  * exists. The returned cache entry is locked for exclusive access ("single
  454  * writer").
  455  */
  456 struct mb_cache_entry *
  457 mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
  458                    sector_t block)
  459 {
  460         unsigned int bucket;
  461         struct list_head *l;
  462         struct mb_cache_entry *ce;
  463 
  464         bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
  465                            cache->c_bucket_bits);
  466         spin_lock(&mb_cache_spinlock);
  467         list_for_each(l, &cache->c_block_hash[bucket]) {
  468                 ce = list_entry(l, struct mb_cache_entry, e_block_list);
  469                 if (ce->e_bdev == bdev && ce->e_block == block) {
  470                         DEFINE_WAIT(wait);
  471 
  472                         if (!list_empty(&ce->e_lru_list))
  473                                 list_del_init(&ce->e_lru_list);
  474 
  475                         while (ce->e_used > 0) {
  476                                 ce->e_queued++;
  477                                 prepare_to_wait(&mb_cache_queue, &wait,
  478                                                 TASK_UNINTERRUPTIBLE);
  479                                 spin_unlock(&mb_cache_spinlock);
  480                                 schedule();
  481                                 spin_lock(&mb_cache_spinlock);
  482                                 ce->e_queued--;
  483                         }
  484                         finish_wait(&mb_cache_queue, &wait);
  485                         ce->e_used += 1 + MB_CACHE_WRITER;
  486 
  487                         if (!__mb_cache_entry_is_hashed(ce)) {
  488                                 __mb_cache_entry_release_unlock(ce);
  489                                 return NULL;
  490                         }
  491                         goto cleanup;
  492                 }
  493         }
  494         ce = NULL;
  495 
  496 cleanup:
  497         spin_unlock(&mb_cache_spinlock);
  498         return ce;
  499 }
  500 
  501 #if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
  502 
  503 static struct mb_cache_entry *
  504 __mb_cache_entry_find(struct list_head *l, struct list_head *head,
  505                       struct block_device *bdev, unsigned int key)
  506 {
  507         while (l != head) {
  508                 struct mb_cache_entry *ce =
  509                         list_entry(l, struct mb_cache_entry, e_index.o_list);
  510                 if (ce->e_bdev == bdev && ce->e_index.o_key == key) {
  511                         DEFINE_WAIT(wait);
  512 
  513                         if (!list_empty(&ce->e_lru_list))
  514                                 list_del_init(&ce->e_lru_list);
  515 
  516                         /* Incrementing before holding the lock gives readers
  517                            priority over writers. */
  518                         ce->e_used++;
  519                         while (ce->e_used >= MB_CACHE_WRITER) {
  520                                 ce->e_queued++;
  521                                 prepare_to_wait(&mb_cache_queue, &wait,
  522                                                 TASK_UNINTERRUPTIBLE);
  523                                 spin_unlock(&mb_cache_spinlock);
  524                                 schedule();
  525                                 spin_lock(&mb_cache_spinlock);
  526                                 ce->e_queued--;
  527                         }
  528                         finish_wait(&mb_cache_queue, &wait);
  529 
  530                         if (!__mb_cache_entry_is_hashed(ce)) {
  531                                 __mb_cache_entry_release_unlock(ce);
  532                                 spin_lock(&mb_cache_spinlock);
  533                                 return ERR_PTR(-EAGAIN);
  534                         }
  535                         return ce;
  536                 }
  537                 l = l->next;
  538         }
  539         return NULL;
  540 }
  541 
  542 
  543 /*
  544  * mb_cache_entry_find_first()
  545  *
  546  * Find the first cache entry on a given device with a certain key in
  547  * an additional index. Additional matches can be found with
  548  * mb_cache_entry_find_next(). Returns NULL if no match was found. The
  549  * returned cache entry is locked for shared access ("multiple readers").
  550  *
  551  * @cache: the cache to search
  552  * @bdev: the device the cache entry should belong to
  553  * @key: the key in the index
  554  */
  555 struct mb_cache_entry *
  556 mb_cache_entry_find_first(struct mb_cache *cache, struct block_device *bdev,
  557                           unsigned int key)
  558 {
  559         unsigned int bucket = hash_long(key, cache->c_bucket_bits);
  560         struct list_head *l;
  561         struct mb_cache_entry *ce;
  562 
  563         spin_lock(&mb_cache_spinlock);
  564         l = cache->c_index_hash[bucket].next;
  565         ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key);
  566         spin_unlock(&mb_cache_spinlock);
  567         return ce;
  568 }
  569 
  570 
  571 /*
  572  * mb_cache_entry_find_next()
  573  *
  574  * Find the next cache entry on a given device with a certain key in an
  575  * additional index. Returns NULL if no match could be found. The previous
  576  * entry is atomatically released, so that mb_cache_entry_find_next() can
  577  * be called like this:
  578  *
  579  * entry = mb_cache_entry_find_first();
  580  * while (entry) {
  581  *      ...
  582  *      entry = mb_cache_entry_find_next(entry, ...);
  583  * }
  584  *
  585  * @prev: The previous match
  586  * @bdev: the device the cache entry should belong to
  587  * @key: the key in the index
  588  */
  589 struct mb_cache_entry *
  590 mb_cache_entry_find_next(struct mb_cache_entry *prev,
  591                          struct block_device *bdev, unsigned int key)
  592 {
  593         struct mb_cache *cache = prev->e_cache;
  594         unsigned int bucket = hash_long(key, cache->c_bucket_bits);
  595         struct list_head *l;
  596         struct mb_cache_entry *ce;
  597 
  598         spin_lock(&mb_cache_spinlock);
  599         l = prev->e_index.o_list.next;
  600         ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key);
  601         __mb_cache_entry_release_unlock(prev);
  602         return ce;
  603 }
  604 
  605 #endif  /* !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) */
  606 
  607 static int __init init_mbcache(void)
  608 {
  609         register_shrinker(&mb_cache_shrinker);
  610         return 0;
  611 }
  612 
  613 static void __exit exit_mbcache(void)
  614 {
  615         unregister_shrinker(&mb_cache_shrinker);
  616 }
  617 
  618 module_init(init_mbcache)
  619 module_exit(exit_mbcache)
  620 

Cache object: 692f1af2948565cdc03cb525a268a9ac


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.