/* * 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/slab.h>#include <linux/sched.h>#include <linux/list_bl.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. */ 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);} 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 inline int__mb_cache_entry_is_index_hashed(struct mb_cache_entry *ce){ return !hlist_bl_unhashed(&ce->e_index.o_list);} 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);} /* * __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 */static inline void__mb_cache_entry_unhash_unlock(struct mb_cache_entry *ce){ __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);} 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 || atomic_read(&ce->e_refcnt))); kmem_cache_free(cache->c_entry_cache, ce); atomic_dec(&cache->c_entry_count);} static void__mb_cache_entry_release(struct mb_cache_entry *ce){ /* 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; } /* * 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); } __spin_unlock_mb_cache_entry(ce); return;forget: mb_assert(list_empty(&ce->e_lru_list)); __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-- > 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;} 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; 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; } 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;} /* * 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; 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; } __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(&mb_cache_spinlock); list_for_each_entry_safe(ce, tmp, &free_list, e_lru_list) { __mb_cache_entry_forget(ce, 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 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);} /* * 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. */Lines 1–500 of 858. Load more
/* * 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/slab.h> #include <linux/sched.h> #include <linux/list_bl.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. */ 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); } 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 inline int __mb_cache_entry_is_index_hashed(struct mb_cache_entry *ce) { return !hlist_bl_unhashed(&ce->e_index.o_list); } 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); } /* * __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 */ static inline void __mb_cache_entry_unhash_unlock(struct mb_cache_entry *ce) { __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); } 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 || atomic_read(&ce->e_refcnt))); kmem_cache_free(cache->c_entry_cache, ce); atomic_dec(&cache->c_entry_count); } static void __mb_cache_entry_release(struct mb_cache_entry *ce) { /* 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; } /* * 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); } __spin_unlock_mb_cache_entry(ce); return; forget: mb_assert(list_empty(&ce->e_lru_list)); __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 long mb_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-- > 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; } static unsigned long mb_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; 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; } 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; } /* * 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 */ void mb_cache_shrink(struct block_device *bdev) { 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; } __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(&mb_cache_spinlock); list_for_each_entry_safe(ce, tmp, &free_list, e_lru_list) { __mb_cache_entry_forget(ce, 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. */ void mb_cache_destroy(struct mb_cache *cache) { 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); } /* * 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. */