/* * 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>#include <linux/slab.h>#include <linux/sched.h>#include <linux/init.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); 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 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 void__mb_cache_entry_release_unlock(struct mb_cache_entry *ce)	__releases(mb_cache_spinlock){	/* 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);}  /* * mb_cache_shrink_scan()  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 freed. */static unsigned longmb_cache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc){	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-- && !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);		freed++;	}	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 freed;} static unsigned longmb_cache_shrink_count(struct shrinker *shrink, struct shrink_control *sc){	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);} static struct shrinker mb_cache_shrinker = {	.count_objects = mb_cache_shrink_count,	.scan_objects = mb_cache_shrink_scan,	.seeks = DEFAULT_SEEKS,}; /* * 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) */struct mb_cache *mb_cache_create(const char *name, int bucket_bits){	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; 	/*	 * 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;}  /* * 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. * * @bdev: which device's cache entries to shrink */voidmb_cache_shrink(struct block_device *bdev){	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);	}}  /* * mb_cache_destroy() * * 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. */voidmb_cache_destroy(struct mb_cache *cache){	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);} /* * 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){	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;}  /* * 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 */intmb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,		      sector_t block, unsigned int key){	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)			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;out:	spin_unlock(&mb_cache_spinlock);	return error;}  /* * 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. */voidmb_cache_entry_release(struct mb_cache_entry *ce){	spin_lock(&mb_cache_spinlock);	__mb_cache_entry_release_unlock(ce);}  /* * mb_cache_entry_free() * * This is equivalent to the sequence mb_cache_entry_takeout() -- * mb_cache_entry_release(). */voidmb_cache_entry_free(struct mb_cache_entry *ce){	spin_lock(&mb_cache_spinlock);	mb_assert(list_empty(&ce->e_lru_list));	__mb_cache_entry_unhash(ce);	__mb_cache_entry_release_unlock(ce);}  /* * 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){	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;		}	}	ce = NULL; 

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