/* * 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 struct mb_cache {	struct list_head		c_cache_list;	const char			*c_name;	struct mb_cache_op		c_op;	atomic_t			c_entry_count;	int				c_bucket_bits;#ifndef MB_CACHE_INDEXES_COUNT	int				c_indexes_count;#endif	kmem_cache_t			*c_entry_cache;	struct list_head		*c_block_hash;	struct list_head		*c_indexes_hash[0];};  /* * 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 struct shrinker *mb_shrinker; static inline intmb_cache_indexes(struct mb_cache *cache){#ifdef MB_CACHE_INDEXES_COUNT	return MB_CACHE_INDEXES_COUNT;#else	return cache->c_indexes_count;#endif} /* * What the mbcache registers as to get shrunk dynamically. */ static int mb_cache_shrink_fn(int nr_to_scan, gfp_t gfp_mask);  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){	int n; 	if (__mb_cache_entry_is_hashed(ce)) {		list_del_init(&ce->e_block_list);		for (n=0; n<mb_cache_indexes(ce->e_cache); n++)			list_del(&ce->e_indexes[n].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));	if (cache->c_op.free && cache->c_op.free(ce, gfp_mask)) {		/* free failed -- put back on the lru list		   for freeing later. */		spin_lock(&mb_cache_spinlock);		list_add(&ce->e_lru_list, &mb_cache_lru_list);		spin_unlock(&mb_cache_spinlock);	} else {		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){	/* 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_fn()  memory pressure callback * * This function is called by the kernel memory management when memory * gets low. * * @nr_to_scan: Number of objects to scan * @gfp_mask: (ignored) * * Returns the number of objects which are present in the cache. */static intmb_cache_shrink_fn(int nr_to_scan, gfp_t gfp_mask){	LIST_HEAD(free_list);	struct list_head *l, *ltmp;	int count = 0; 	spin_lock(&mb_cache_spinlock);	list_for_each(l, &mb_cache_list) {		struct mb_cache *cache =			list_entry(l, struct mb_cache, c_cache_list);		mb_debug("cache %s (%d)", cache->c_name,			  atomic_read(&cache->c_entry_count));		count += atomic_read(&cache->c_entry_count);	}	mb_debug("trying to free %d entries", nr_to_scan);	if (nr_to_scan == 0) {		spin_unlock(&mb_cache_spinlock);		goto out;	}	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);	}	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_mask);	}out:	return (count / 100) * sysctl_vfs_cache_pressure;}  /* * 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) * @cache_op: contains the callback called when freeing a cache entry * @entry_size: The size of a cache entry, including *              struct mb_cache_entry * @indexes_count: number of additional indexes in the cache. Must equal *                 MB_CACHE_INDEXES_COUNT if the number of indexes is *                 hardwired. * @bucket_bits: log2(number of hash buckets) */struct mb_cache *mb_cache_create(const char *name, struct mb_cache_op *cache_op,		size_t entry_size, int indexes_count, int bucket_bits){	int m=0, n, bucket_count = 1 << bucket_bits;	struct mb_cache *cache = NULL; 	if(entry_size < sizeof(struct mb_cache_entry) +	   indexes_count * sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]))		return NULL; 	cache = kmalloc(sizeof(struct mb_cache) +	                indexes_count * sizeof(struct list_head), GFP_KERNEL);	if (!cache)		goto fail;	cache->c_name = name;	cache->c_op.free = NULL;	if (cache_op)		cache->c_op.free = cache_op->free;	atomic_set(&cache->c_entry_count, 0);	cache->c_bucket_bits = bucket_bits;#ifdef MB_CACHE_INDEXES_COUNT	mb_assert(indexes_count == MB_CACHE_INDEXES_COUNT);#else	cache->c_indexes_count = indexes_count;#endif	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]);	for (m=0; m<indexes_count; m++) {		cache->c_indexes_hash[m] = kmalloc(bucket_count *		                                 sizeof(struct list_head),		                                 GFP_KERNEL);		if (!cache->c_indexes_hash[m])			goto fail;		for (n=0; n<bucket_count; n++)			INIT_LIST_HEAD(&cache->c_indexes_hash[m][n]);	}	cache->c_entry_cache = kmem_cache_create(name, entry_size, 0,		SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL, NULL);	if (!cache->c_entry_cache)		goto fail; 	spin_lock(&mb_cache_spinlock);	list_add(&cache->c_cache_list, &mb_cache_list);	spin_unlock(&mb_cache_spinlock);	return cache; fail:	if (cache) {		while (--m >= 0)			kfree(cache->c_indexes_hash[m]);		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;	int n; 	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); 	for (n=0; n < mb_cache_indexes(cache); n++)		kfree(cache->c_indexes_hash[n]);	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){	struct mb_cache_entry *ce; 	atomic_inc(&cache->c_entry_count);	ce = kmem_cache_alloc(cache->c_entry_cache, GFP_KERNEL);	if (ce) {		INIT_LIST_HEAD(&ce->e_lru_list);		INIT_LIST_HEAD(&ce->e_block_list);		ce->e_cache = cache;		ce->e_used = 1 + MB_CACHE_WRITER;		ce->e_queued = 0;	}	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 * @keys: array of additional keys. There must be indexes_count entries *        in the array (as specified when creating the cache). */intmb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,		      sector_t block, unsigned int keys[]){	struct mb_cache *cache = ce->e_cache;	unsigned int bucket;	struct list_head *l;	int error = -EBUSY, n; 	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]);	for (n=0; n<mb_cache_indexes(cache); n++) {		ce->e_indexes[n].o_key = keys[n];		bucket = hash_long(keys[n], cache->c_bucket_bits);		list_add(&ce->e_indexes[n].o_list,			 &cache->c_indexes_hash[n][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

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