diff options
Diffstat (limited to 'fs/mbcache.c')
| -rw-r--r-- | fs/mbcache.c | 871 |
1 files changed, 348 insertions, 523 deletions
diff --git a/fs/mbcache.c b/fs/mbcache.c index 8c32ef3ba88e..e60a840999aa 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -1,620 +1,445 @@ -/* - * 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. - */ - -#include <linux/kernel.h> -#include <linux/module.h> - -#include <linux/hash.h> -#include <linux/fs.h> -#include <linux/mm.h> +// SPDX-License-Identifier: GPL-2.0-only +#include <linux/spinlock.h> #include <linux/slab.h> +#include <linux/list.h> +#include <linux/list_bl.h> +#include <linux/module.h> #include <linux/sched.h> -#include <linux/init.h> +#include <linux/workqueue.h> #include <linux/mbcache.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) - -static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue); - -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. - */ - -static LIST_HEAD(mb_cache_list); -static LIST_HEAD(mb_cache_lru_list); -static DEFINE_SPINLOCK(mb_cache_spinlock); - /* - * What the mbcache registers as to get shrunk dynamically. + * 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_or_get()). + * + * Ext2 and ext4 use this cache for deduplication of extended attribute blocks. + * Ext4 also uses it for deduplication of xattr values stored in inodes. + * They use hash of data as a key and provide a value that may represent a + * block or inode number. That's why keys need not be unique (hash of different + * data may be the same). However user provided value 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 int mb_cache_shrink_fn(struct shrinker *shrink, - struct shrink_control *sc); - -static struct shrinker mb_cache_shrinker = { - .shrink = mb_cache_shrink_fn, - .seeks = DEFAULT_SEEKS, +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 */ + unsigned long 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 inline int -__mb_cache_entry_is_hashed(struct mb_cache_entry *ce) -{ - return !list_empty(&ce->e_block_list); -} - - -static void -__mb_cache_entry_unhash(struct mb_cache_entry *ce) -{ - if (__mb_cache_entry_is_hashed(ce)) { - list_del_init(&ce->e_block_list); - list_del(&ce->e_index.o_list); - } -} - +static struct kmem_cache *mb_entry_cache; -static void -__mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask) -{ - struct mb_cache *cache = ce->e_cache; - - mb_assert(!(ce->e_used || ce->e_queued)); - kmem_cache_free(cache->c_entry_cache, ce); - atomic_dec(&cache->c_entry_count); -} +static unsigned long mb_cache_shrink(struct mb_cache *cache, + unsigned long nr_to_scan); - -static void -__mb_cache_entry_release_unlock(struct mb_cache_entry *ce) - __releases(mb_cache_spinlock) +static inline struct hlist_bl_head *mb_cache_entry_head(struct mb_cache *cache, + u32 key) { - /* 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; - ce->e_used--; - if (!(ce->e_used || ce->e_queued)) { - if (!__mb_cache_entry_is_hashed(ce)) - goto forget; - mb_assert(list_empty(&ce->e_lru_list)); - list_add_tail(&ce->e_lru_list, &mb_cache_lru_list); - } - spin_unlock(&mb_cache_spinlock); - return; -forget: - spin_unlock(&mb_cache_spinlock); - __mb_cache_entry_forget(ce, GFP_KERNEL); + return &cache->c_hash[hash_32(key, cache->c_bucket_bits)]; } - /* - * mb_cache_shrink_fn() memory pressure callback - * - * This function is called by the kernel memory management when memory - * gets low. - * - * @shrink: (ignored) - * @sc: shrink_control passed from reclaim - * - * Returns the number of objects which are present in the cache. + * Number of entries to reclaim synchronously when there are too many entries + * in cache */ -static int -mb_cache_shrink_fn(struct shrinker *shrink, struct shrink_control *sc) -{ - LIST_HEAD(free_list); - struct mb_cache *cache; - struct mb_cache_entry *entry, *tmp; - int count = 0; - int nr_to_scan = sc->nr_to_scan; - gfp_t gfp_mask = sc->gfp_mask; - - mb_debug("trying to free %d entries", nr_to_scan); - spin_lock(&mb_cache_spinlock); - while (nr_to_scan-- && !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_move_tail(&ce->e_lru_list, &free_list); - __mb_cache_entry_unhash(ce); - } - 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); - list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) { - __mb_cache_entry_forget(entry, gfp_mask); - } - return (count / 100) * sysctl_vfs_cache_pressure; -} - +#define SYNC_SHRINK_BATCH 64 /* - * 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. + * 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 + * @value - value of the entry + * @reusable - is the entry reusable by others? * - * @name: name of the cache (informal) - * @bucket_bits: log2(number of hash buckets) + * Creates entry in @cache with key @key and value @value. The function returns + * -EBUSY if entry with the same key and value already exists in cache. + * Otherwise 0 is returned. */ -struct mb_cache * -mb_cache_create(const char *name, int bucket_bits) +int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key, + u64 value, bool reusable) { - int n, bucket_count = 1 << bucket_bits; - struct mb_cache *cache = NULL; - - 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 list_head), - GFP_KERNEL); - if (!cache->c_block_hash) - goto fail; - for (n=0; n<bucket_count; n++) - INIT_LIST_HEAD(&cache->c_block_hash[n]); - cache->c_index_hash = kmalloc(bucket_count * sizeof(struct list_head), - GFP_KERNEL); - if (!cache->c_index_hash) - goto fail; - for (n=0; n<bucket_count; n++) - INIT_LIST_HEAD(&cache->c_index_hash[n]); - cache->c_entry_cache = kmem_cache_create(name, - sizeof(struct mb_cache_entry), 0, - SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL); - if (!cache->c_entry_cache) - goto fail2; - + 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); /* - * Set an upper limit on the number of cache entries so that the hash - * chains won't grow too long. + * We create entry with two references. One reference is kept by the + * hash table, the other reference is used to protect us from + * mb_cache_entry_delete_or_get() until the entry is fully setup. This + * avoids nesting of cache->c_list_lock into hash table bit locks which + * is problematic for RT. */ - cache->c_max_entries = bucket_count << 4; + atomic_set(&entry->e_refcnt, 2); + entry->e_key = key; + entry->e_value = value; + entry->e_flags = 0; + if (reusable) + set_bit(MBE_REUSABLE_B, &entry->e_flags); + 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_value == value) { + 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); + cache->c_entry_count++; + spin_unlock(&cache->c_list_lock); + mb_cache_entry_put(cache, entry); - spin_lock(&mb_cache_spinlock); - list_add(&cache->c_cache_list, &mb_cache_list); - spin_unlock(&mb_cache_spinlock); - return cache; + return 0; +} +EXPORT_SYMBOL(mb_cache_entry_create); -fail2: - kfree(cache->c_index_hash); +void __mb_cache_entry_free(struct mb_cache *cache, struct mb_cache_entry *entry) +{ + struct hlist_bl_head *head; -fail: - kfree(cache->c_block_hash); - kfree(cache); - return NULL; + head = mb_cache_entry_head(cache, entry->e_key); + hlist_bl_lock(head); + hlist_bl_del(&entry->e_hash_list); + hlist_bl_unlock(head); + kmem_cache_free(mb_entry_cache, entry); } - +EXPORT_SYMBOL(__mb_cache_entry_free); /* - * mb_cache_shrink() + * mb_cache_entry_wait_unused - wait to be the last user of the entry * - * 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. + * @entry - entry to work on * - * @bdev: which device's cache entries to shrink + * Wait to be the last user of the entry. */ -void -mb_cache_shrink(struct block_device *bdev) +void mb_cache_entry_wait_unused(struct mb_cache_entry *entry) { - LIST_HEAD(free_list); - struct list_head *l, *ltmp; - - spin_lock(&mb_cache_spinlock); - list_for_each_safe(l, ltmp, &mb_cache_lru_list) { - struct mb_cache_entry *ce = - list_entry(l, struct mb_cache_entry, e_lru_list); - if (ce->e_bdev == bdev) { - list_move_tail(&ce->e_lru_list, &free_list); - __mb_cache_entry_unhash(ce); - } - } - spin_unlock(&mb_cache_spinlock); - list_for_each_safe(l, ltmp, &free_list) { - __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry, - e_lru_list), GFP_KERNEL); - } + wait_var_event(&entry->e_refcnt, atomic_read(&entry->e_refcnt) <= 2); } +EXPORT_SYMBOL(mb_cache_entry_wait_unused); +static struct mb_cache_entry *__entry_find(struct mb_cache *cache, + struct mb_cache_entry *entry, + u32 key) +{ + 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 && + test_bit(MBE_REUSABLE_B, &entry->e_flags) && + atomic_inc_not_zero(&entry->e_refcnt)) + goto out; + node = node->next; + } + entry = NULL; +out: + hlist_bl_unlock(head); + if (old_entry) + mb_cache_entry_put(cache, old_entry); + + return entry; +} /* - * mb_cache_destroy() + * mb_cache_entry_find_first - find the first reusable entry with the given key + * @cache: cache where we should search + * @key: key to look for * - * 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. + * Search in @cache for a reusable entry with key @key. Grabs reference to the + * first reusable entry found and returns the entry. */ -void -mb_cache_destroy(struct mb_cache *cache) +struct mb_cache_entry *mb_cache_entry_find_first(struct mb_cache *cache, + u32 key) { - LIST_HEAD(free_list); - struct list_head *l, *ltmp; - - spin_lock(&mb_cache_spinlock); - list_for_each_safe(l, ltmp, &mb_cache_lru_list) { - struct mb_cache_entry *ce = - list_entry(l, struct mb_cache_entry, e_lru_list); - if (ce->e_cache == cache) { - list_move_tail(&ce->e_lru_list, &free_list); - __mb_cache_entry_unhash(ce); - } - } - list_del(&cache->c_cache_list); - spin_unlock(&mb_cache_spinlock); - - list_for_each_safe(l, ltmp, &free_list) { - __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry, - e_lru_list), 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)); - } - - kmem_cache_destroy(cache->c_entry_cache); - - kfree(cache->c_index_hash); - kfree(cache->c_block_hash); - kfree(cache); + return __entry_find(cache, NULL, key); } +EXPORT_SYMBOL(mb_cache_entry_find_first); /* - * mb_cache_entry_alloc() + * mb_cache_entry_find_next - find next reusable entry with the same key + * @cache: cache where we should search + * @entry: entry to start search from * - * 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. + * Finds next reusable 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 reusable 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_alloc(struct mb_cache *cache, gfp_t gfp_flags) +struct mb_cache_entry *mb_cache_entry_find_next(struct mb_cache *cache, + struct mb_cache_entry *entry) { - struct mb_cache_entry *ce = NULL; - - if (atomic_read(&cache->c_entry_count) >= cache->c_max_entries) { - spin_lock(&mb_cache_spinlock); - if (!list_empty(&mb_cache_lru_list)) { - ce = list_entry(mb_cache_lru_list.next, - struct mb_cache_entry, e_lru_list); - list_del_init(&ce->e_lru_list); - __mb_cache_entry_unhash(ce); - } - spin_unlock(&mb_cache_spinlock); - } - if (!ce) { - 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_LIST_HEAD(&ce->e_block_list); - ce->e_cache = cache; - ce->e_queued = 0; - } - ce->e_used = 1 + MB_CACHE_WRITER; - return ce; + return __entry_find(cache, entry, entry->e_key); } - +EXPORT_SYMBOL(mb_cache_entry_find_next); /* - * 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 + * mb_cache_entry_get - get a cache entry by value (and key) + * @cache - cache we work with + * @key - key + * @value - value */ -int -mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev, - sector_t block, unsigned int key) +struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *cache, u32 key, + u64 value) { - struct mb_cache *cache = ce->e_cache; - unsigned int bucket; - struct list_head *l; - int error = -EBUSY; - - bucket = hash_long((unsigned long)bdev + (block & 0xffffffff), - cache->c_bucket_bits); - spin_lock(&mb_cache_spinlock); - list_for_each_prev(l, &cache->c_block_hash[bucket]) { - struct mb_cache_entry *ce = - list_entry(l, struct mb_cache_entry, e_block_list); - if (ce->e_bdev == bdev && ce->e_block == block) + 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_value == value && + atomic_inc_not_zero(&entry->e_refcnt)) goto out; } - __mb_cache_entry_unhash(ce); - ce->e_bdev = bdev; - ce->e_block = block; - list_add(&ce->e_block_list, &cache->c_block_hash[bucket]); - ce->e_index.o_key = key; - bucket = hash_long(key, cache->c_bucket_bits); - list_add(&ce->e_index.o_list, &cache->c_index_hash[bucket]); - error = 0; + entry = NULL; out: - spin_unlock(&mb_cache_spinlock); - return error; + hlist_bl_unlock(head); + return entry; } +EXPORT_SYMBOL(mb_cache_entry_get); - -/* - * mb_cache_entry_release() +/* mb_cache_entry_delete_or_get - remove a cache entry if it has no users + * @cache - cache we work with + * @key - key + * @value - value * - * 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. + * Remove entry from cache @cache with key @key and value @value. The removal + * happens only if the entry is unused. The function returns NULL in case the + * entry was successfully removed or there's no entry in cache. Otherwise the + * function grabs reference of the entry that we failed to delete because it + * still has users and return it. */ -void -mb_cache_entry_release(struct mb_cache_entry *ce) +struct mb_cache_entry *mb_cache_entry_delete_or_get(struct mb_cache *cache, + u32 key, u64 value) { - spin_lock(&mb_cache_spinlock); - __mb_cache_entry_release_unlock(ce); -} + struct mb_cache_entry *entry; + entry = mb_cache_entry_get(cache, key, value); + if (!entry) + return NULL; -/* - * mb_cache_entry_free() + /* + * Drop the ref we got from mb_cache_entry_get() and the initial hash + * ref if we are the last user + */ + if (atomic_cmpxchg(&entry->e_refcnt, 2, 0) != 2) + return entry; + + spin_lock(&cache->c_list_lock); + if (!list_empty(&entry->e_list)) + list_del_init(&entry->e_list); + cache->c_entry_count--; + spin_unlock(&cache->c_list_lock); + __mb_cache_entry_free(cache, entry); + return NULL; +} +EXPORT_SYMBOL(mb_cache_entry_delete_or_get); + +/* mb_cache_entry_touch - cache entry got used + * @cache - cache the entry belongs to + * @entry - entry that got used * - * This is equivalent to the sequence mb_cache_entry_takeout() -- - * mb_cache_entry_release(). + * Marks entry as used to give hit higher chances of surviving in cache. */ -void -mb_cache_entry_free(struct mb_cache_entry *ce) +void mb_cache_entry_touch(struct mb_cache *cache, + struct mb_cache_entry *entry) { - spin_lock(&mb_cache_spinlock); - mb_assert(list_empty(&ce->e_lru_list)); - __mb_cache_entry_unhash(ce); - __mb_cache_entry_release_unlock(ce); + set_bit(MBE_REFERENCED_B, &entry->e_flags); } +EXPORT_SYMBOL(mb_cache_entry_touch); +static unsigned long mb_cache_count(struct shrinker *shrink, + struct shrink_control *sc) +{ + struct mb_cache *cache = shrink->private_data; -/* - * mb_cache_entry_get() - * - * 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"). - */ -struct mb_cache_entry * -mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev, - sector_t block) + return cache->c_entry_count; +} + +/* Shrink number of entries in cache */ +static unsigned long mb_cache_shrink(struct mb_cache *cache, + unsigned long nr_to_scan) { - unsigned int bucket; - struct list_head *l; - struct mb_cache_entry *ce; - - bucket = hash_long((unsigned long)bdev + (block & 0xffffffff), - cache->c_bucket_bits); - spin_lock(&mb_cache_spinlock); - list_for_each(l, &cache->c_block_hash[bucket]) { - ce = list_entry(l, struct mb_cache_entry, e_block_list); - if (ce->e_bdev == bdev && ce->e_block == block) { - DEFINE_WAIT(wait); - - if (!list_empty(&ce->e_lru_list)) - list_del_init(&ce->e_lru_list); - - while (ce->e_used > 0) { - ce->e_queued++; - prepare_to_wait(&mb_cache_queue, &wait, - TASK_UNINTERRUPTIBLE); - spin_unlock(&mb_cache_spinlock); - schedule(); - spin_lock(&mb_cache_spinlock); - ce->e_queued--; - } - finish_wait(&mb_cache_queue, &wait); - ce->e_used += 1 + MB_CACHE_WRITER; - - if (!__mb_cache_entry_is_hashed(ce)) { - __mb_cache_entry_release_unlock(ce); - return NULL; - } - goto cleanup; + struct mb_cache_entry *entry; + unsigned long 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); + /* Drop initial hash reference if there is no user */ + if (test_bit(MBE_REFERENCED_B, &entry->e_flags) || + atomic_cmpxchg(&entry->e_refcnt, 1, 0) != 1) { + clear_bit(MBE_REFERENCED_B, &entry->e_flags); + list_move_tail(&entry->e_list, &cache->c_list); + continue; } + list_del_init(&entry->e_list); + cache->c_entry_count--; + spin_unlock(&cache->c_list_lock); + __mb_cache_entry_free(cache, entry); + shrunk++; + cond_resched(); + spin_lock(&cache->c_list_lock); } - ce = NULL; + spin_unlock(&cache->c_list_lock); -cleanup: - spin_unlock(&mb_cache_spinlock); - return ce; + return shrunk; } -#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) - -static struct mb_cache_entry * -__mb_cache_entry_find(struct list_head *l, struct list_head *head, - struct block_device *bdev, unsigned int key) +static unsigned long mb_cache_scan(struct shrinker *shrink, + struct shrink_control *sc) { - while (l != head) { - struct mb_cache_entry *ce = - list_entry(l, struct mb_cache_entry, e_index.o_list); - if (ce->e_bdev == bdev && ce->e_index.o_key == key) { - DEFINE_WAIT(wait); - - if (!list_empty(&ce->e_lru_list)) - list_del_init(&ce->e_lru_list); - - /* Incrementing before holding the lock gives readers - priority over writers. */ - ce->e_used++; - while (ce->e_used >= MB_CACHE_WRITER) { - ce->e_queued++; - prepare_to_wait(&mb_cache_queue, &wait, - TASK_UNINTERRUPTIBLE); - spin_unlock(&mb_cache_spinlock); - schedule(); - spin_lock(&mb_cache_spinlock); - ce->e_queued--; - } - finish_wait(&mb_cache_queue, &wait); - - if (!__mb_cache_entry_is_hashed(ce)) { - __mb_cache_entry_release_unlock(ce); - spin_lock(&mb_cache_spinlock); - return ERR_PTR(-EAGAIN); - } - return ce; - } - l = l->next; - } - return NULL; + struct mb_cache *cache = shrink->private_data; + return mb_cache_shrink(cache, sc->nr_to_scan); } +/* We shrink 1/X of the cache when we have too many entries in it */ +#define SHRINK_DIVISOR 16 + +static void mb_cache_shrink_worker(struct work_struct *work) +{ + 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_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_create - create cache + * @bucket_bits: log2 of the hash table size * - * @cache: the cache to search - * @bdev: the device the cache entry should belong to - * @key: the key in the index + * Create cache for keys with 2^bucket_bits hash entries. */ -struct mb_cache_entry * -mb_cache_entry_find_first(struct mb_cache *cache, struct block_device *bdev, - unsigned int key) +struct mb_cache *mb_cache_create(int bucket_bits) { - unsigned int bucket = hash_long(key, cache->c_bucket_bits); - struct list_head *l; - struct mb_cache_entry *ce; - - spin_lock(&mb_cache_spinlock); - l = cache->c_index_hash[bucket].next; - ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key); - spin_unlock(&mb_cache_spinlock); - return ce; -} + struct mb_cache *cache; + unsigned long bucket_count = 1UL << bucket_bits; + unsigned long i; + + 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_array(bucket_count, + sizeof(struct hlist_bl_head), + GFP_KERNEL); + if (!cache->c_hash) { + kfree(cache); + goto err_out; + } + for (i = 0; i < bucket_count; i++) + INIT_HLIST_BL_HEAD(&cache->c_hash[i]); + + cache->c_shrink = shrinker_alloc(0, "mbcache-shrinker"); + if (!cache->c_shrink) { + kfree(cache->c_hash); + kfree(cache); + goto err_out; + } + + cache->c_shrink->count_objects = mb_cache_count; + cache->c_shrink->scan_objects = mb_cache_scan; + cache->c_shrink->private_data = cache; + + shrinker_register(cache->c_shrink); + INIT_WORK(&cache->c_shrink_work, mb_cache_shrink_worker); + + return cache; + +err_out: + return NULL; +} +EXPORT_SYMBOL(mb_cache_create); /* - * 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: + * mb_cache_destroy - destroy cache + * @cache: the cache to destroy * - * 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 + * 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_next(struct mb_cache_entry *prev, - struct block_device *bdev, unsigned int key) +void mb_cache_destroy(struct mb_cache *cache) { - struct mb_cache *cache = prev->e_cache; - unsigned int bucket = hash_long(key, cache->c_bucket_bits); - struct list_head *l; - struct mb_cache_entry *ce; - - spin_lock(&mb_cache_spinlock); - l = prev->e_index.o_list.next; - ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key); - __mb_cache_entry_release_unlock(prev); - return ce; -} + struct mb_cache_entry *entry, *next; -#endif /* !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) */ + shrinker_free(cache->c_shrink); -static int __init init_mbcache(void) + /* + * 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) { + 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); +} +EXPORT_SYMBOL(mb_cache_destroy); + +static int __init mbcache_init(void) { - register_shrinker(&mb_cache_shrinker); + mb_entry_cache = KMEM_CACHE(mb_cache_entry, SLAB_RECLAIM_ACCOUNT); + if (!mb_entry_cache) + return -ENOMEM; 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"); |