-/*
- * linux/fs/mbcache.c
- * (C) 2001-2002 Andreas Gruenbacher, <a.gruenbacher@computer.org>
- */
-
-/*
- * Filesystem Meta Information Block Cache (mbcache)
- *
- * The mbcache caches blocks of block devices that need to be located
- * by their device/block number, as well as by other criteria (such
- * as the block's contents).
- *
- * There can only be one cache entry in a cache per device and block number.
- * Additional indexes need not be unique in this sense. The number of
- * additional indexes (=other criteria) can be hardwired at compile time
- * or specified at cache create time.
- *
- * Each cache entry is of fixed size. An entry may be `valid' or `invalid'
- * in the cache. A valid entry is in the main hash tables of the cache,
- * and may also be in the lru list. An invalid entry is not in any hashes
- * or lists.
- *
- * A valid cache entry is only in the lru list if no handles refer to it.
- * Invalid cache entries will be freed when the last handle to the cache
- * entry is released. Entries that cannot be freed immediately are put
- * back on the lru list.
- */
-
-/*
- * Lock descriptions and usage:
- *
- * Each hash chain of both the block and index hash tables now contains
- * a built-in lock used to serialize accesses to the hash chain.
- *
- * Accesses to global data structures mb_cache_list and mb_cache_lru_list
- * are serialized via the global spinlock mb_cache_spinlock.
- *
- * Each mb_cache_entry contains a spinlock, e_entry_lock, to serialize
- * accesses to its local data, such as e_used and e_queued.
- *
- * Lock ordering:
- *
- * Each block hash chain's lock has the highest lock order, followed by an
- * index hash chain's lock, mb_cache_bg_lock (used to implement mb_cache_entry's
- * lock), and mb_cach_spinlock, with the lowest order. While holding
- * either a block or index hash chain lock, a thread can acquire an
- * mc_cache_bg_lock, which in turn can also acquire mb_cache_spinlock.
- *
- * Synchronization:
- *
- * Since both mb_cache_entry_get and mb_cache_entry_find scan the block and
- * index hash chian, it needs to lock the corresponding hash chain. For each
- * mb_cache_entry within the chain, it needs to lock the mb_cache_entry to
- * prevent either any simultaneous release or free on the entry and also
- * to serialize accesses to either the e_used or e_queued member of the entry.
- *
- * To avoid having a dangling reference to an already freed
- * mb_cache_entry, an mb_cache_entry is only freed when it is not on a
- * block hash chain and also no longer being referenced, both e_used,
- * and e_queued are 0's. When an mb_cache_entry is explicitly freed it is
- * first removed from a block hash chain.
- */
-
-#include <linux/kernel.h>
-#include <linux/module.h>
-
-#include <linux/hash.h>
-#include <linux/fs.h>
-#include <linux/mm.h>
+#include <linux/spinlock.h>
#include <linux/slab.h>
-#include <linux/sched.h>
+#include <linux/list.h>
#include <linux/list_bl.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/workqueue.h>
#include <linux/mbcache.h>
-#include <linux/init.h>
-#include <linux/blockgroup_lock.h>
-#include <linux/log2.h>
-
-#ifdef MB_CACHE_DEBUG
-# define mb_debug(f...) do { \
- printk(KERN_DEBUG f); \
- printk("\n"); \
- } while (0)
-#define mb_assert(c) do { if (!(c)) \
- printk(KERN_ERR "assertion " #c " failed\n"); \
- } while(0)
-#else
-# define mb_debug(f...) do { } while(0)
-# define mb_assert(c) do { } while(0)
-#endif
-#define mb_error(f...) do { \
- printk(KERN_ERR f); \
- printk("\n"); \
- } while(0)
-
-#define MB_CACHE_WRITER ((unsigned short)~0U >> 1)
-
-#define MB_CACHE_ENTRY_LOCK_BITS ilog2(NR_BG_LOCKS)
-#define MB_CACHE_ENTRY_LOCK_INDEX(ce) \
- (hash_long((unsigned long)ce, MB_CACHE_ENTRY_LOCK_BITS))
-
-static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue);
-static struct blockgroup_lock *mb_cache_bg_lock;
-static struct kmem_cache *mb_cache_kmem_cache;
-
-MODULE_AUTHOR("Andreas Gruenbacher <a.gruenbacher@computer.org>");
-MODULE_DESCRIPTION("Meta block cache (for extended attributes)");
-MODULE_LICENSE("GPL");
-
-EXPORT_SYMBOL(mb_cache_create);
-EXPORT_SYMBOL(mb_cache_shrink);
-EXPORT_SYMBOL(mb_cache_destroy);
-EXPORT_SYMBOL(mb_cache_entry_alloc);
-EXPORT_SYMBOL(mb_cache_entry_insert);
-EXPORT_SYMBOL(mb_cache_entry_release);
-EXPORT_SYMBOL(mb_cache_entry_free);
-EXPORT_SYMBOL(mb_cache_entry_get);
-#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
-EXPORT_SYMBOL(mb_cache_entry_find_first);
-EXPORT_SYMBOL(mb_cache_entry_find_next);
-#endif
/*
- * Global data: list of all mbcache's, lru list, and a spinlock for
- * accessing cache data structures on SMP machines. The lru list is
- * global across all mbcaches.
+ * Mbcache is a simple key-value store. Keys need not be unique, however
+ * key-value pairs are expected to be unique (we use this fact in
+ * mb_cache_entry_delete_block()).
+ *
+ * Ext2 and ext4 use this cache for deduplication of extended attribute blocks.
+ * They use hash of a block contents as a key and block number as a value.
+ * That's why keys need not be unique (different xattr blocks may end up having
+ * the same hash). However block number always uniquely identifies a cache
+ * entry.
+ *
+ * We provide functions for creation and removal of entries, search by key,
+ * and a special "delete entry with given key-value pair" operation. Fixed
+ * size hash table is used for fast key lookups.
*/
-static LIST_HEAD(mb_cache_list);
-static LIST_HEAD(mb_cache_lru_list);
-static DEFINE_SPINLOCK(mb_cache_spinlock);
-
-static inline void
-__spin_lock_mb_cache_entry(struct mb_cache_entry *ce)
-{
- spin_lock(bgl_lock_ptr(mb_cache_bg_lock,
- MB_CACHE_ENTRY_LOCK_INDEX(ce)));
-}
-
-static inline void
-__spin_unlock_mb_cache_entry(struct mb_cache_entry *ce)
-{
- spin_unlock(bgl_lock_ptr(mb_cache_bg_lock,
- MB_CACHE_ENTRY_LOCK_INDEX(ce)));
-}
-
-static inline int
-__mb_cache_entry_is_block_hashed(struct mb_cache_entry *ce)
-{
- return !hlist_bl_unhashed(&ce->e_block_list);
-}
+struct mb_cache {
+ /* Hash table of entries */
+ struct hlist_bl_head *c_hash;
+ /* log2 of hash table size */
+ int c_bucket_bits;
+ /* Maximum entries in cache to avoid degrading hash too much */
+ int c_max_entries;
+ /* Protects c_list, c_entry_count */
+ spinlock_t c_list_lock;
+ struct list_head c_list;
+ /* Number of entries in cache */
+ unsigned long c_entry_count;
+ struct shrinker c_shrink;
+ /* Work for shrinking when the cache has too many entries */
+ struct work_struct c_shrink_work;
+};
+static struct kmem_cache *mb_entry_cache;
-static inline void
-__mb_cache_entry_unhash_block(struct mb_cache_entry *ce)
-{
- if (__mb_cache_entry_is_block_hashed(ce))
- hlist_bl_del_init(&ce->e_block_list);
-}
+static unsigned long mb_cache_shrink(struct mb_cache *cache,
+ unsigned int nr_to_scan);
-static inline int
-__mb_cache_entry_is_index_hashed(struct mb_cache_entry *ce)
+static inline struct hlist_bl_head *mb_cache_entry_head(struct mb_cache *cache,
+ u32 key)
{
- return !hlist_bl_unhashed(&ce->e_index.o_list);
+ return &cache->c_hash[hash_32(key, cache->c_bucket_bits)];
}
-static inline void
-__mb_cache_entry_unhash_index(struct mb_cache_entry *ce)
-{
- if (__mb_cache_entry_is_index_hashed(ce))
- hlist_bl_del_init(&ce->e_index.o_list);
-}
+/*
+ * Number of entries to reclaim synchronously when there are too many entries
+ * in cache
+ */
+#define SYNC_SHRINK_BATCH 64
/*
- * __mb_cache_entry_unhash_unlock()
- *
- * This function is called to unhash both the block and index hash
- * chain.
- * It assumes both the block and index hash chain is locked upon entry.
- * It also unlock both hash chains both exit
+ * mb_cache_entry_create - create entry in cache
+ * @cache - cache where the entry should be created
+ * @mask - gfp mask with which the entry should be allocated
+ * @key - key of the entry
+ * @block - block that contains data
+ * @reusable - is the block reusable by other inodes?
+ *
+ * Creates entry in @cache with key @key and records that data is stored in
+ * block @block. The function returns -EBUSY if entry with the same key
+ * and for the same block already exists in cache. Otherwise 0 is returned.
*/
-static inline void
-__mb_cache_entry_unhash_unlock(struct mb_cache_entry *ce)
+int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key,
+ sector_t block, bool reusable)
{
- __mb_cache_entry_unhash_index(ce);
- hlist_bl_unlock(ce->e_index_hash_p);
- __mb_cache_entry_unhash_block(ce);
- hlist_bl_unlock(ce->e_block_hash_p);
+ struct mb_cache_entry *entry, *dup;
+ struct hlist_bl_node *dup_node;
+ struct hlist_bl_head *head;
+
+ /* Schedule background reclaim if there are too many entries */
+ if (cache->c_entry_count >= cache->c_max_entries)
+ schedule_work(&cache->c_shrink_work);
+ /* Do some sync reclaim if background reclaim cannot keep up */
+ if (cache->c_entry_count >= 2*cache->c_max_entries)
+ mb_cache_shrink(cache, SYNC_SHRINK_BATCH);
+
+ entry = kmem_cache_alloc(mb_entry_cache, mask);
+ if (!entry)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&entry->e_list);
+ /* One ref for hash, one ref returned */
+ atomic_set(&entry->e_refcnt, 1);
+ entry->e_key = key;
+ entry->e_block = block;
+ entry->e_reusable = reusable;
+ head = mb_cache_entry_head(cache, key);
+ hlist_bl_lock(head);
+ hlist_bl_for_each_entry(dup, dup_node, head, e_hash_list) {
+ if (dup->e_key == key && dup->e_block == block) {
+ hlist_bl_unlock(head);
+ kmem_cache_free(mb_entry_cache, entry);
+ return -EBUSY;
+ }
+ }
+ hlist_bl_add_head(&entry->e_hash_list, head);
+ hlist_bl_unlock(head);
+
+ spin_lock(&cache->c_list_lock);
+ list_add_tail(&entry->e_list, &cache->c_list);
+ /* Grab ref for LRU list */
+ atomic_inc(&entry->e_refcnt);
+ cache->c_entry_count++;
+ spin_unlock(&cache->c_list_lock);
+
+ return 0;
}
+EXPORT_SYMBOL(mb_cache_entry_create);
-static void
-__mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask)
+void __mb_cache_entry_free(struct mb_cache_entry *entry)
{
- struct mb_cache *cache = ce->e_cache;
-
- mb_assert(!(ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt)));
- kmem_cache_free(cache->c_entry_cache, ce);
- atomic_dec(&cache->c_entry_count);
+ kmem_cache_free(mb_entry_cache, entry);
}
+EXPORT_SYMBOL(__mb_cache_entry_free);
-static void
-__mb_cache_entry_release(struct mb_cache_entry *ce)
+static struct mb_cache_entry *__entry_find(struct mb_cache *cache,
+ struct mb_cache_entry *entry,
+ u32 key)
{
- /* First lock the entry to serialize access to its local data. */
- __spin_lock_mb_cache_entry(ce);
- /* Wake up all processes queuing for this cache entry. */
- if (ce->e_queued)
- wake_up_all(&mb_cache_queue);
- if (ce->e_used >= MB_CACHE_WRITER)
- ce->e_used -= MB_CACHE_WRITER;
- /*
- * Make sure that all cache entries on lru_list have
- * both e_used and e_qued of 0s.
- */
- ce->e_used--;
- if (!(ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt))) {
- if (!__mb_cache_entry_is_block_hashed(ce)) {
- __spin_unlock_mb_cache_entry(ce);
- goto forget;
+ struct mb_cache_entry *old_entry = entry;
+ struct hlist_bl_node *node;
+ struct hlist_bl_head *head;
+
+ head = mb_cache_entry_head(cache, key);
+ hlist_bl_lock(head);
+ if (entry && !hlist_bl_unhashed(&entry->e_hash_list))
+ node = entry->e_hash_list.next;
+ else
+ node = hlist_bl_first(head);
+ while (node) {
+ entry = hlist_bl_entry(node, struct mb_cache_entry,
+ e_hash_list);
+ if (entry->e_key == key && entry->e_reusable) {
+ atomic_inc(&entry->e_refcnt);
+ goto out;
}
- /*
- * Need access to lru list, first drop entry lock,
- * then reacquire the lock in the proper order.
- */
- spin_lock(&mb_cache_spinlock);
- if (list_empty(&ce->e_lru_list))
- list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
- spin_unlock(&mb_cache_spinlock);
+ node = node->next;
}
- __spin_unlock_mb_cache_entry(ce);
- return;
-forget:
- mb_assert(list_empty(&ce->e_lru_list));
- __mb_cache_entry_forget(ce, GFP_KERNEL);
+ entry = NULL;
+out:
+ hlist_bl_unlock(head);
+ if (old_entry)
+ mb_cache_entry_put(cache, old_entry);
+
+ return entry;
}
/*
- * mb_cache_shrink_scan() memory pressure callback
- *
- * This function is called by the kernel memory management when memory
- * gets low.
+ * mb_cache_entry_find_first - find the first entry in cache with given key
+ * @cache: cache where we should search
+ * @key: key to look for
*
- * @shrink: (ignored)
- * @sc: shrink_control passed from reclaim
- *
- * Returns the number of objects freed.
+ * Search in @cache for entry with key @key. Grabs reference to the first
+ * entry found and returns the entry.
*/
-static unsigned long
-mb_cache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
+struct mb_cache_entry *mb_cache_entry_find_first(struct mb_cache *cache,
+ u32 key)
{
- LIST_HEAD(free_list);
- struct mb_cache_entry *entry, *tmp;
- int nr_to_scan = sc->nr_to_scan;
- gfp_t gfp_mask = sc->gfp_mask;
- unsigned long freed = 0;
-
- mb_debug("trying to free %d entries", nr_to_scan);
- spin_lock(&mb_cache_spinlock);
- while ((nr_to_scan-- > 0) && !list_empty(&mb_cache_lru_list)) {
- struct mb_cache_entry *ce =
- list_entry(mb_cache_lru_list.next,
- struct mb_cache_entry, e_lru_list);
- list_del_init(&ce->e_lru_list);
- if (ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt))
- continue;
- spin_unlock(&mb_cache_spinlock);
- /* Prevent any find or get operation on the entry */
- hlist_bl_lock(ce->e_block_hash_p);
- hlist_bl_lock(ce->e_index_hash_p);
- /* Ignore if it is touched by a find/get */
- if (ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt) ||
- !list_empty(&ce->e_lru_list)) {
- hlist_bl_unlock(ce->e_index_hash_p);
- hlist_bl_unlock(ce->e_block_hash_p);
- spin_lock(&mb_cache_spinlock);
- continue;
- }
- __mb_cache_entry_unhash_unlock(ce);
- list_add_tail(&ce->e_lru_list, &free_list);
- spin_lock(&mb_cache_spinlock);
- }
- spin_unlock(&mb_cache_spinlock);
-
- list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) {
- __mb_cache_entry_forget(entry, gfp_mask);
- freed++;
- }
- return freed;
+ return __entry_find(cache, NULL, key);
}
+EXPORT_SYMBOL(mb_cache_entry_find_first);
-static unsigned long
-mb_cache_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
+/*
+ * mb_cache_entry_find_next - find next entry in cache with the same
+ * @cache: cache where we should search
+ * @entry: entry to start search from
+ *
+ * Finds next entry in the hash chain which has the same key as @entry.
+ * If @entry is unhashed (which can happen when deletion of entry races
+ * with the search), finds the first entry in the hash chain. The function
+ * drops reference to @entry and returns with a reference to the found entry.
+ */
+struct mb_cache_entry *mb_cache_entry_find_next(struct mb_cache *cache,
+ struct mb_cache_entry *entry)
{
- struct mb_cache *cache;
- unsigned long count = 0;
-
- spin_lock(&mb_cache_spinlock);
- list_for_each_entry(cache, &mb_cache_list, c_cache_list) {
- mb_debug("cache %s (%d)", cache->c_name,
- atomic_read(&cache->c_entry_count));
- count += atomic_read(&cache->c_entry_count);
- }
- spin_unlock(&mb_cache_spinlock);
-
- return vfs_pressure_ratio(count);
+ return __entry_find(cache, entry, entry->e_key);
}
-
-static struct shrinker mb_cache_shrinker = {
- .count_objects = mb_cache_shrink_count,
- .scan_objects = mb_cache_shrink_scan,
- .seeks = DEFAULT_SEEKS,
-};
+EXPORT_SYMBOL(mb_cache_entry_find_next);
/*
- * mb_cache_create() create a new cache
- *
- * All entries in one cache are equal size. Cache entries may be from
- * multiple devices. If this is the first mbcache created, registers
- * the cache with kernel memory management. Returns NULL if no more
- * memory was available.
- *
- * @name: name of the cache (informal)
- * @bucket_bits: log2(number of hash buckets)
+ * mb_cache_entry_get - get a cache entry by block number (and key)
+ * @cache - cache we work with
+ * @key - key of block number @block
+ * @block - block number
*/
-struct mb_cache *
-mb_cache_create(const char *name, int bucket_bits)
+struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *cache, u32 key,
+ sector_t block)
{
- int n, bucket_count = 1 << bucket_bits;
- struct mb_cache *cache = NULL;
-
- if (!mb_cache_bg_lock) {
- mb_cache_bg_lock = kmalloc(sizeof(struct blockgroup_lock),
- GFP_KERNEL);
- if (!mb_cache_bg_lock)
- return NULL;
- bgl_lock_init(mb_cache_bg_lock);
- }
-
- cache = kmalloc(sizeof(struct mb_cache), GFP_KERNEL);
- if (!cache)
- return NULL;
- cache->c_name = name;
- atomic_set(&cache->c_entry_count, 0);
- cache->c_bucket_bits = bucket_bits;
- cache->c_block_hash = kmalloc(bucket_count *
- sizeof(struct hlist_bl_head), GFP_KERNEL);
- if (!cache->c_block_hash)
- goto fail;
- for (n=0; n<bucket_count; n++)
- INIT_HLIST_BL_HEAD(&cache->c_block_hash[n]);
- cache->c_index_hash = kmalloc(bucket_count *
- sizeof(struct hlist_bl_head), GFP_KERNEL);
- if (!cache->c_index_hash)
- goto fail;
- for (n=0; n<bucket_count; n++)
- INIT_HLIST_BL_HEAD(&cache->c_index_hash[n]);
- if (!mb_cache_kmem_cache) {
- mb_cache_kmem_cache = kmem_cache_create(name,
- sizeof(struct mb_cache_entry), 0,
- SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL);
- if (!mb_cache_kmem_cache)
- goto fail2;
+ struct hlist_bl_node *node;
+ struct hlist_bl_head *head;
+ struct mb_cache_entry *entry;
+
+ head = mb_cache_entry_head(cache, key);
+ hlist_bl_lock(head);
+ hlist_bl_for_each_entry(entry, node, head, e_hash_list) {
+ if (entry->e_key == key && entry->e_block == block) {
+ atomic_inc(&entry->e_refcnt);
+ goto out;
+ }
}
- cache->c_entry_cache = mb_cache_kmem_cache;
-
- /*
- * Set an upper limit on the number of cache entries so that the hash
- * chains won't grow too long.
- */
- cache->c_max_entries = bucket_count << 4;
-
- spin_lock(&mb_cache_spinlock);
- list_add(&cache->c_cache_list, &mb_cache_list);
- spin_unlock(&mb_cache_spinlock);
- return cache;
-
-fail2:
- kfree(cache->c_index_hash);
-
-fail:
- kfree(cache->c_block_hash);
- kfree(cache);
- return NULL;
+ entry = NULL;
+out:
+ hlist_bl_unlock(head);
+ return entry;
}
+EXPORT_SYMBOL(mb_cache_entry_get);
-
-/*
- * mb_cache_shrink()
- *
- * Removes all cache entries of a device from the cache. All cache entries
- * currently in use cannot be freed, and thus remain in the cache. All others
- * are freed.
+/* mb_cache_entry_delete_block - remove information about block from cache
+ * @cache - cache we work with
+ * @key - key of block @block
+ * @block - block number
*
- * @bdev: which device's cache entries to shrink
+ * Remove entry from cache @cache with key @key with data stored in @block.
*/
-void
-mb_cache_shrink(struct block_device *bdev)
+void mb_cache_entry_delete_block(struct mb_cache *cache, u32 key,
+ sector_t block)
{
- LIST_HEAD(free_list);
- struct list_head *l;
- struct mb_cache_entry *ce, *tmp;
-
- l = &mb_cache_lru_list;
- spin_lock(&mb_cache_spinlock);
- while (!list_is_last(l, &mb_cache_lru_list)) {
- l = l->next;
- ce = list_entry(l, struct mb_cache_entry, e_lru_list);
- if (ce->e_bdev == bdev) {
- list_del_init(&ce->e_lru_list);
- if (ce->e_used || ce->e_queued ||
- atomic_read(&ce->e_refcnt))
- continue;
- spin_unlock(&mb_cache_spinlock);
- /*
- * Prevent any find or get operation on the entry.
- */
- hlist_bl_lock(ce->e_block_hash_p);
- hlist_bl_lock(ce->e_index_hash_p);
- /* Ignore if it is touched by a find/get */
- if (ce->e_used || ce->e_queued ||
- atomic_read(&ce->e_refcnt) ||
- !list_empty(&ce->e_lru_list)) {
- hlist_bl_unlock(ce->e_index_hash_p);
- hlist_bl_unlock(ce->e_block_hash_p);
- l = &mb_cache_lru_list;
- spin_lock(&mb_cache_spinlock);
- continue;
+ struct hlist_bl_node *node;
+ struct hlist_bl_head *head;
+ struct mb_cache_entry *entry;
+
+ head = mb_cache_entry_head(cache, key);
+ hlist_bl_lock(head);
+ hlist_bl_for_each_entry(entry, node, head, e_hash_list) {
+ if (entry->e_key == key && entry->e_block == block) {
+ /* We keep hash list reference to keep entry alive */
+ hlist_bl_del_init(&entry->e_hash_list);
+ hlist_bl_unlock(head);
+ spin_lock(&cache->c_list_lock);
+ if (!list_empty(&entry->e_list)) {
+ list_del_init(&entry->e_list);
+ cache->c_entry_count--;
+ atomic_dec(&entry->e_refcnt);
}
- __mb_cache_entry_unhash_unlock(ce);
- mb_assert(!(ce->e_used || ce->e_queued ||
- atomic_read(&ce->e_refcnt)));
- list_add_tail(&ce->e_lru_list, &free_list);
- l = &mb_cache_lru_list;
- spin_lock(&mb_cache_spinlock);
+ spin_unlock(&cache->c_list_lock);
+ mb_cache_entry_put(cache, entry);
+ return;
}
}
- spin_unlock(&mb_cache_spinlock);
-
- list_for_each_entry_safe(ce, tmp, &free_list, e_lru_list) {
- __mb_cache_entry_forget(ce, GFP_KERNEL);
- }
+ hlist_bl_unlock(head);
}
+EXPORT_SYMBOL(mb_cache_entry_delete_block);
-
-/*
- * mb_cache_destroy()
+/* mb_cache_entry_touch - cache entry got used
+ * @cache - cache the entry belongs to
+ * @entry - entry that got used
*
- * Shrinks the cache to its minimum possible size (hopefully 0 entries),
- * and then destroys it. If this was the last mbcache, un-registers the
- * mbcache from kernel memory management.
+ * Marks entry as used to give hit higher chances of surviving in cache.
*/
-void
-mb_cache_destroy(struct mb_cache *cache)
+void mb_cache_entry_touch(struct mb_cache *cache,
+ struct mb_cache_entry *entry)
{
- LIST_HEAD(free_list);
- struct mb_cache_entry *ce, *tmp;
-
- spin_lock(&mb_cache_spinlock);
- list_for_each_entry_safe(ce, tmp, &mb_cache_lru_list, e_lru_list) {
- if (ce->e_cache == cache)
- list_move_tail(&ce->e_lru_list, &free_list);
- }
- list_del(&cache->c_cache_list);
- spin_unlock(&mb_cache_spinlock);
-
- list_for_each_entry_safe(ce, tmp, &free_list, e_lru_list) {
- list_del_init(&ce->e_lru_list);
- /*
- * Prevent any find or get operation on the entry.
- */
- hlist_bl_lock(ce->e_block_hash_p);
- hlist_bl_lock(ce->e_index_hash_p);
- mb_assert(!(ce->e_used || ce->e_queued ||
- atomic_read(&ce->e_refcnt)));
- __mb_cache_entry_unhash_unlock(ce);
- __mb_cache_entry_forget(ce, GFP_KERNEL);
- }
-
- if (atomic_read(&cache->c_entry_count) > 0) {
- mb_error("cache %s: %d orphaned entries",
- cache->c_name,
- atomic_read(&cache->c_entry_count));
- }
-
- if (list_empty(&mb_cache_list)) {
- kmem_cache_destroy(mb_cache_kmem_cache);
- mb_cache_kmem_cache = NULL;
- }
- kfree(cache->c_index_hash);
- kfree(cache->c_block_hash);
- kfree(cache);
+ entry->e_referenced = 1;
}
+EXPORT_SYMBOL(mb_cache_entry_touch);
-/*
- * mb_cache_entry_alloc()
- *
- * Allocates a new cache entry. The new entry will not be valid initially,
- * and thus cannot be looked up yet. It should be filled with data, and
- * then inserted into the cache using mb_cache_entry_insert(). Returns NULL
- * if no more memory was available.
- */
-struct mb_cache_entry *
-mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
+static unsigned long mb_cache_count(struct shrinker *shrink,
+ struct shrink_control *sc)
{
- struct mb_cache_entry *ce;
-
- if (atomic_read(&cache->c_entry_count) >= cache->c_max_entries) {
- struct list_head *l;
-
- l = &mb_cache_lru_list;
- spin_lock(&mb_cache_spinlock);
- while (!list_is_last(l, &mb_cache_lru_list)) {
- l = l->next;
- ce = list_entry(l, struct mb_cache_entry, e_lru_list);
- if (ce->e_cache == cache) {
- list_del_init(&ce->e_lru_list);
- if (ce->e_used || ce->e_queued ||
- atomic_read(&ce->e_refcnt))
- continue;
- spin_unlock(&mb_cache_spinlock);
- /*
- * Prevent any find or get operation on the
- * entry.
- */
- hlist_bl_lock(ce->e_block_hash_p);
- hlist_bl_lock(ce->e_index_hash_p);
- /* Ignore if it is touched by a find/get */
- if (ce->e_used || ce->e_queued ||
- atomic_read(&ce->e_refcnt) ||
- !list_empty(&ce->e_lru_list)) {
- hlist_bl_unlock(ce->e_index_hash_p);
- hlist_bl_unlock(ce->e_block_hash_p);
- l = &mb_cache_lru_list;
- spin_lock(&mb_cache_spinlock);
- continue;
- }
- mb_assert(list_empty(&ce->e_lru_list));
- mb_assert(!(ce->e_used || ce->e_queued ||
- atomic_read(&ce->e_refcnt)));
- __mb_cache_entry_unhash_unlock(ce);
- goto found;
- }
- }
- spin_unlock(&mb_cache_spinlock);
- }
+ struct mb_cache *cache = container_of(shrink, struct mb_cache,
+ c_shrink);
- ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);
- if (!ce)
- return NULL;
- atomic_inc(&cache->c_entry_count);
- INIT_LIST_HEAD(&ce->e_lru_list);
- INIT_HLIST_BL_NODE(&ce->e_block_list);
- INIT_HLIST_BL_NODE(&ce->e_index.o_list);
- ce->e_cache = cache;
- ce->e_queued = 0;
- atomic_set(&ce->e_refcnt, 0);
-found:
- ce->e_block_hash_p = &cache->c_block_hash[0];
- ce->e_index_hash_p = &cache->c_index_hash[0];
- ce->e_used = 1 + MB_CACHE_WRITER;
- return ce;
+ return cache->c_entry_count;
}
-
-/*
- * mb_cache_entry_insert()
- *
- * Inserts an entry that was allocated using mb_cache_entry_alloc() into
- * the cache. After this, the cache entry can be looked up, but is not yet
- * in the lru list as the caller still holds a handle to it. Returns 0 on
- * success, or -EBUSY if a cache entry for that device + inode exists
- * already (this may happen after a failed lookup, but when another process
- * has inserted the same cache entry in the meantime).
- *
- * @bdev: device the cache entry belongs to
- * @block: block number
- * @key: lookup key
- */
-int
-mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,
- sector_t block, unsigned int key)
+/* Shrink number of entries in cache */
+static unsigned long mb_cache_shrink(struct mb_cache *cache,
+ unsigned int nr_to_scan)
{
- struct mb_cache *cache = ce->e_cache;
- unsigned int bucket;
- struct hlist_bl_node *l;
- struct hlist_bl_head *block_hash_p;
- struct hlist_bl_head *index_hash_p;
- struct mb_cache_entry *lce;
-
- mb_assert(ce);
- bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
- cache->c_bucket_bits);
- block_hash_p = &cache->c_block_hash[bucket];
- hlist_bl_lock(block_hash_p);
- hlist_bl_for_each_entry(lce, l, block_hash_p, e_block_list) {
- if (lce->e_bdev == bdev && lce->e_block == block) {
- hlist_bl_unlock(block_hash_p);
- return -EBUSY;
+ struct mb_cache_entry *entry;
+ struct hlist_bl_head *head;
+ unsigned int shrunk = 0;
+
+ spin_lock(&cache->c_list_lock);
+ while (nr_to_scan-- && !list_empty(&cache->c_list)) {
+ entry = list_first_entry(&cache->c_list,
+ struct mb_cache_entry, e_list);
+ if (entry->e_referenced) {
+ entry->e_referenced = 0;
+ list_move_tail(&cache->c_list, &entry->e_list);
+ continue;
}
+ list_del_init(&entry->e_list);
+ cache->c_entry_count--;
+ /*
+ * We keep LRU list reference so that entry doesn't go away
+ * from under us.
+ */
+ spin_unlock(&cache->c_list_lock);
+ head = mb_cache_entry_head(cache, entry->e_key);
+ hlist_bl_lock(head);
+ if (!hlist_bl_unhashed(&entry->e_hash_list)) {
+ hlist_bl_del_init(&entry->e_hash_list);
+ atomic_dec(&entry->e_refcnt);
+ }
+ hlist_bl_unlock(head);
+ if (mb_cache_entry_put(cache, entry))
+ shrunk++;
+ cond_resched();
+ spin_lock(&cache->c_list_lock);
}
- mb_assert(!__mb_cache_entry_is_block_hashed(ce));
- __mb_cache_entry_unhash_block(ce);
- __mb_cache_entry_unhash_index(ce);
- ce->e_bdev = bdev;
- ce->e_block = block;
- ce->e_block_hash_p = block_hash_p;
- ce->e_index.o_key = key;
- hlist_bl_add_head(&ce->e_block_list, block_hash_p);
- hlist_bl_unlock(block_hash_p);
- bucket = hash_long(key, cache->c_bucket_bits);
- index_hash_p = &cache->c_index_hash[bucket];
- hlist_bl_lock(index_hash_p);
- ce->e_index_hash_p = index_hash_p;
- hlist_bl_add_head(&ce->e_index.o_list, index_hash_p);
- hlist_bl_unlock(index_hash_p);
- return 0;
-}
+ spin_unlock(&cache->c_list_lock);
+ return shrunk;
+}
-/*
- * mb_cache_entry_release()
- *
- * Release a handle to a cache entry. When the last handle to a cache entry
- * is released it is either freed (if it is invalid) or otherwise inserted
- * in to the lru list.
- */
-void
-mb_cache_entry_release(struct mb_cache_entry *ce)
+static unsigned long mb_cache_scan(struct shrinker *shrink,
+ struct shrink_control *sc)
{
- __mb_cache_entry_release(ce);
+ int nr_to_scan = sc->nr_to_scan;
+ struct mb_cache *cache = container_of(shrink, struct mb_cache,
+ c_shrink);
+ return mb_cache_shrink(cache, nr_to_scan);
}
+/* We shrink 1/X of the cache when we have too many entries in it */
+#define SHRINK_DIVISOR 16
-/*
- * mb_cache_entry_free()
- *
- */
-void
-mb_cache_entry_free(struct mb_cache_entry *ce)
+static void mb_cache_shrink_worker(struct work_struct *work)
{
- mb_assert(ce);
- mb_assert(list_empty(&ce->e_lru_list));
- hlist_bl_lock(ce->e_index_hash_p);
- __mb_cache_entry_unhash_index(ce);
- hlist_bl_unlock(ce->e_index_hash_p);
- hlist_bl_lock(ce->e_block_hash_p);
- __mb_cache_entry_unhash_block(ce);
- hlist_bl_unlock(ce->e_block_hash_p);
- __mb_cache_entry_release(ce);
+ struct mb_cache *cache = container_of(work, struct mb_cache,
+ c_shrink_work);
+ mb_cache_shrink(cache, cache->c_max_entries / SHRINK_DIVISOR);
}
-
/*
- * mb_cache_entry_get()
+ * mb_cache_create - create cache
+ * @bucket_bits: log2 of the hash table size
*
- * Get a cache entry by device / block number. (There can only be one entry
- * in the cache per device and block.) Returns NULL if no such cache entry
- * exists. The returned cache entry is locked for exclusive access ("single
- * writer").
+ * Create cache for keys with 2^bucket_bits hash entries.
*/
-struct mb_cache_entry *
-mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
- sector_t block)
+struct mb_cache *mb_cache_create(int bucket_bits)
{
- unsigned int bucket;
- struct hlist_bl_node *l;
- struct mb_cache_entry *ce;
- struct hlist_bl_head *block_hash_p;
-
- bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
- cache->c_bucket_bits);
- block_hash_p = &cache->c_block_hash[bucket];
- /* First serialize access to the block corresponding hash chain. */
- hlist_bl_lock(block_hash_p);
- hlist_bl_for_each_entry(ce, l, block_hash_p, e_block_list) {
- mb_assert(ce->e_block_hash_p == block_hash_p);
- if (ce->e_bdev == bdev && ce->e_block == block) {
- /*
- * Prevent a free from removing the entry.
- */
- atomic_inc(&ce->e_refcnt);
- hlist_bl_unlock(block_hash_p);
- __spin_lock_mb_cache_entry(ce);
- atomic_dec(&ce->e_refcnt);
- if (ce->e_used > 0) {
- DEFINE_WAIT(wait);
- while (ce->e_used > 0) {
- ce->e_queued++;
- prepare_to_wait(&mb_cache_queue, &wait,
- TASK_UNINTERRUPTIBLE);
- __spin_unlock_mb_cache_entry(ce);
- schedule();
- __spin_lock_mb_cache_entry(ce);
- ce->e_queued--;
- }
- finish_wait(&mb_cache_queue, &wait);
- }
- ce->e_used += 1 + MB_CACHE_WRITER;
- __spin_unlock_mb_cache_entry(ce);
+ struct mb_cache *cache;
+ int bucket_count = 1 << bucket_bits;
+ int i;
- if (!list_empty(&ce->e_lru_list)) {
- spin_lock(&mb_cache_spinlock);
- list_del_init(&ce->e_lru_list);
- spin_unlock(&mb_cache_spinlock);
- }
- if (!__mb_cache_entry_is_block_hashed(ce)) {
- __mb_cache_entry_release(ce);
- return NULL;
- }
- return ce;
- }
+ if (!try_module_get(THIS_MODULE))
+ return NULL;
+
+ cache = kzalloc(sizeof(struct mb_cache), GFP_KERNEL);
+ if (!cache)
+ goto err_out;
+ cache->c_bucket_bits = bucket_bits;
+ cache->c_max_entries = bucket_count << 4;
+ INIT_LIST_HEAD(&cache->c_list);
+ spin_lock_init(&cache->c_list_lock);
+ cache->c_hash = kmalloc(bucket_count * sizeof(struct hlist_bl_head),
+ GFP_KERNEL);
+ if (!cache->c_hash) {
+ kfree(cache);
+ goto err_out;
}
- hlist_bl_unlock(block_hash_p);
- return NULL;
-}
+ for (i = 0; i < bucket_count; i++)
+ INIT_HLIST_BL_HEAD(&cache->c_hash[i]);
-#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
+ cache->c_shrink.count_objects = mb_cache_count;
+ cache->c_shrink.scan_objects = mb_cache_scan;
+ cache->c_shrink.seeks = DEFAULT_SEEKS;
+ register_shrinker(&cache->c_shrink);
-static struct mb_cache_entry *
-__mb_cache_entry_find(struct hlist_bl_node *l, struct hlist_bl_head *head,
- struct block_device *bdev, unsigned int key)
-{
+ INIT_WORK(&cache->c_shrink_work, mb_cache_shrink_worker);
- /* The index hash chain is alredy acquire by caller. */
- while (l != NULL) {
- struct mb_cache_entry *ce =
- hlist_bl_entry(l, struct mb_cache_entry,
- e_index.o_list);
- mb_assert(ce->e_index_hash_p == head);
- if (ce->e_bdev == bdev && ce->e_index.o_key == key) {
- /*
- * Prevent a free from removing the entry.
- */
- atomic_inc(&ce->e_refcnt);
- hlist_bl_unlock(head);
- __spin_lock_mb_cache_entry(ce);
- atomic_dec(&ce->e_refcnt);
- ce->e_used++;
- /* Incrementing before holding the lock gives readers
- priority over writers. */
- if (ce->e_used >= MB_CACHE_WRITER) {
- DEFINE_WAIT(wait);
-
- while (ce->e_used >= MB_CACHE_WRITER) {
- ce->e_queued++;
- prepare_to_wait(&mb_cache_queue, &wait,
- TASK_UNINTERRUPTIBLE);
- __spin_unlock_mb_cache_entry(ce);
- schedule();
- __spin_lock_mb_cache_entry(ce);
- ce->e_queued--;
- }
- finish_wait(&mb_cache_queue, &wait);
- }
- __spin_unlock_mb_cache_entry(ce);
- if (!list_empty(&ce->e_lru_list)) {
- spin_lock(&mb_cache_spinlock);
- list_del_init(&ce->e_lru_list);
- spin_unlock(&mb_cache_spinlock);
- }
- if (!__mb_cache_entry_is_block_hashed(ce)) {
- __mb_cache_entry_release(ce);
- return ERR_PTR(-EAGAIN);
- }
- return ce;
- }
- l = l->next;
- }
- hlist_bl_unlock(head);
+ return cache;
+
+err_out:
+ module_put(THIS_MODULE);
return NULL;
}
-
+EXPORT_SYMBOL(mb_cache_create);
/*
- * mb_cache_entry_find_first()
- *
- * Find the first cache entry on a given device with a certain key in
- * an additional index. Additional matches can be found with
- * mb_cache_entry_find_next(). Returns NULL if no match was found. The
- * returned cache entry is locked for shared access ("multiple readers").
+ * mb_cache_destroy - destroy cache
+ * @cache: the cache to destroy
*
- * @cache: the cache to search
- * @bdev: the device the cache entry should belong to
- * @key: the key in the index
+ * Free all entries in cache and cache itself. Caller must make sure nobody
+ * (except shrinker) can reach @cache when calling this.
*/
-struct mb_cache_entry *
-mb_cache_entry_find_first(struct mb_cache *cache, struct block_device *bdev,
- unsigned int key)
+void mb_cache_destroy(struct mb_cache *cache)
{
- unsigned int bucket = hash_long(key, cache->c_bucket_bits);
- struct hlist_bl_node *l;
- struct mb_cache_entry *ce = NULL;
- struct hlist_bl_head *index_hash_p;
-
- index_hash_p = &cache->c_index_hash[bucket];
- hlist_bl_lock(index_hash_p);
- if (!hlist_bl_empty(index_hash_p)) {
- l = hlist_bl_first(index_hash_p);
- ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
- } else
- hlist_bl_unlock(index_hash_p);
- return ce;
-}
+ struct mb_cache_entry *entry, *next;
+ unregister_shrinker(&cache->c_shrink);
-/*
- * mb_cache_entry_find_next()
- *
- * Find the next cache entry on a given device with a certain key in an
- * additional index. Returns NULL if no match could be found. The previous
- * entry is atomatically released, so that mb_cache_entry_find_next() can
- * be called like this:
- *
- * entry = mb_cache_entry_find_first();
- * while (entry) {
- * ...
- * entry = mb_cache_entry_find_next(entry, ...);
- * }
- *
- * @prev: The previous match
- * @bdev: the device the cache entry should belong to
- * @key: the key in the index
- */
-struct mb_cache_entry *
-mb_cache_entry_find_next(struct mb_cache_entry *prev,
- struct block_device *bdev, unsigned int key)
-{
- struct mb_cache *cache = prev->e_cache;
- unsigned int bucket = hash_long(key, cache->c_bucket_bits);
- struct hlist_bl_node *l;
- struct mb_cache_entry *ce;
- struct hlist_bl_head *index_hash_p;
-
- index_hash_p = &cache->c_index_hash[bucket];
- mb_assert(prev->e_index_hash_p == index_hash_p);
- hlist_bl_lock(index_hash_p);
- mb_assert(!hlist_bl_empty(index_hash_p));
- l = prev->e_index.o_list.next;
- ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
- __mb_cache_entry_release(prev);
- return ce;
+ /*
+ * We don't bother with any locking. Cache must not be used at this
+ * point.
+ */
+ list_for_each_entry_safe(entry, next, &cache->c_list, e_list) {
+ if (!hlist_bl_unhashed(&entry->e_hash_list)) {
+ hlist_bl_del_init(&entry->e_hash_list);
+ atomic_dec(&entry->e_refcnt);
+ } else
+ WARN_ON(1);
+ list_del(&entry->e_list);
+ WARN_ON(atomic_read(&entry->e_refcnt) != 1);
+ mb_cache_entry_put(cache, entry);
+ }
+ kfree(cache->c_hash);
+ kfree(cache);
+ module_put(THIS_MODULE);
}
+EXPORT_SYMBOL(mb_cache_destroy);
-#endif /* !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) */
-
-static int __init init_mbcache(void)
+static int __init mbcache_init(void)
{
- register_shrinker(&mb_cache_shrinker);
+ mb_entry_cache = kmem_cache_create("mbcache",
+ sizeof(struct mb_cache_entry), 0,
+ SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL);
+ BUG_ON(!mb_entry_cache);
return 0;
}
-static void __exit exit_mbcache(void)
+static void __exit mbcache_exit(void)
{
- unregister_shrinker(&mb_cache_shrinker);
+ kmem_cache_destroy(mb_entry_cache);
}
-module_init(init_mbcache)
-module_exit(exit_mbcache)
+module_init(mbcache_init)
+module_exit(mbcache_exit)
+MODULE_AUTHOR("Jan Kara <jack@suse.cz>");
+MODULE_DESCRIPTION("Meta block cache (for extended attributes)");
+MODULE_LICENSE("GPL");
projects / cascardo / linux.git / blobdiff