[linux.git] / fs / mbcache.c

/*
 * linux/fs/mbcache.c
 * (C) 2001-2002 Andreas Gruenbacher, <[email protected]>
 */

/*
 * 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 <[email protected]>");
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 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-- && !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 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;

	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
 */
void
mb_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.
 */
void
mb_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
 */
int
mb_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.
 */
void
mb_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().
 */
void
mb_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;

cleanup:
	spin_unlock(&mb_cache_spinlock);
	return ce;
}

#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)
{
	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;
}


/*
 * 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").
 *
 * @cache: the cache to search
 * @bdev: the device the cache entry should belong to
 * @key: the key in the index
 */
struct mb_cache_entry *
mb_cache_entry_find_first(struct mb_cache *cache, struct block_device *bdev,
			  unsigned int key)
{
	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;
}


/*
 * 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 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;
}

#endif  /* !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) */

static int __init init_mbcache(void)
{
	register_shrinker(&mb_cache_shrinker);
	return 0;
}

static void __exit exit_mbcache(void)
{
	unregister_shrinker(&mb_cache_shrinker);
}

module_init(init_mbcache)
module_exit(exit_mbcache)
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/fs/mbcache.c
	3	* (C) 2001-2002 Andreas Gruenbacher, <[email protected]>
	4	*/
	5
	6	/*
	7	* Filesystem Meta Information Block Cache (mbcache)
	8	*
	9	* The mbcache caches blocks of block devices that need to be located
	10	* by their device/block number, as well as by other criteria (such
	11	* as the block's contents).
	12	*
	13	* There can only be one cache entry in a cache per device and block number.
	14	* Additional indexes need not be unique in this sense. The number of
	15	* additional indexes (=other criteria) can be hardwired at compile time
	16	* or specified at cache create time.
	17	*
	18	* Each cache entry is of fixed size. An entry may be `valid' or `invalid'
	19	* in the cache. A valid entry is in the main hash tables of the cache,
	20	* and may also be in the lru list. An invalid entry is not in any hashes
	21	* or lists.
	22	*
	23	* A valid cache entry is only in the lru list if no handles refer to it.
	24	* Invalid cache entries will be freed when the last handle to the cache
	25	* entry is released. Entries that cannot be freed immediately are put
	26	* back on the lru list.
	27	*/
	28
	29	#include <linux/kernel.h>
	30	#include <linux/module.h>
	31
	32	#include <linux/hash.h>
	33	#include <linux/fs.h>
	34	#include <linux/mm.h>
	35	#include <linux/slab.h>
	36	#include <linux/sched.h>
	37	#include <linux/init.h>
	38	#include <linux/mbcache.h>
	39
	40
	41	#ifdef MB_CACHE_DEBUG
	42	# define mb_debug(f...) do { \
	43	printk(KERN_DEBUG f); \
	44	printk("\n"); \
	45	} while (0)
	46	#define mb_assert(c) do { if (!(c)) \
	47	printk(KERN_ERR "assertion " #c " failed\n"); \
	48	} while(0)
	49	#else
	50	# define mb_debug(f...) do { } while(0)
	51	# define mb_assert(c) do { } while(0)
	52	#endif
	53	#define mb_error(f...) do { \
	54	printk(KERN_ERR f); \
	55	printk("\n"); \
	56	} while(0)
	57
	58	#define MB_CACHE_WRITER ((unsigned short)~0U >> 1)
	59
75c96f85	60	static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue);
1da177e4 LT	61
	62	MODULE_AUTHOR("Andreas Gruenbacher <[email protected]>");
	63	MODULE_DESCRIPTION("Meta block cache (for extended attributes)");
	64	MODULE_LICENSE("GPL");
	65
	66	EXPORT_SYMBOL(mb_cache_create);
	67	EXPORT_SYMBOL(mb_cache_shrink);
	68	EXPORT_SYMBOL(mb_cache_destroy);
	69	EXPORT_SYMBOL(mb_cache_entry_alloc);
	70	EXPORT_SYMBOL(mb_cache_entry_insert);
	71	EXPORT_SYMBOL(mb_cache_entry_release);
	72	EXPORT_SYMBOL(mb_cache_entry_free);
	73	EXPORT_SYMBOL(mb_cache_entry_get);
	74	#if !defined(MB_CACHE_INDEXES_COUNT) \|\| (MB_CACHE_INDEXES_COUNT > 0)
	75	EXPORT_SYMBOL(mb_cache_entry_find_first);
	76	EXPORT_SYMBOL(mb_cache_entry_find_next);
	77	#endif
	78
1da177e4 LT	79	/*
	80	* Global data: list of all mbcache's, lru list, and a spinlock for
	81	* accessing cache data structures on SMP machines. The lru list is
	82	* global across all mbcaches.
	83	*/
	84
	85	static LIST_HEAD(mb_cache_list);
	86	static LIST_HEAD(mb_cache_lru_list);
	87	static DEFINE_SPINLOCK(mb_cache_spinlock);
1da177e4	88
1da177e4 LT	89	static inline int
	90	__mb_cache_entry_is_hashed(struct mb_cache_entry *ce)
	91	{
	92	return !list_empty(&ce->e_block_list);
	93	}
	94
	95
858119e1	96	static void
1da177e4 LT	97	__mb_cache_entry_unhash(struct mb_cache_entry *ce)
1da177e4 LT	98	{
1da177e4 LT	99	if (__mb_cache_entry_is_hashed(ce)) {
1da177e4 LT	100	list_del_init(&ce->e_block_list);
2aec7c52	101	list_del(&ce->e_index.o_list);
1da177e4 LT	102	}
	103	}
	104
	105
858119e1	106	static void
27496a8c	107	__mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask)
1da177e4 LT	108	{
	109	struct mb_cache *cache = ce->e_cache;
	110
	111	mb_assert(!(ce->e_used \|\| ce->e_queued));
2aec7c52 AG	112	kmem_cache_free(cache->c_entry_cache, ce);
2aec7c52 AG	113	atomic_dec(&cache->c_entry_count);
1da177e4 LT	114	}
	115
	116
858119e1	117	static void
1da177e4	118	__mb_cache_entry_release_unlock(struct mb_cache_entry *ce)
58f555e5	119	__releases(mb_cache_spinlock)
1da177e4 LT	120	{
	121	/* Wake up all processes queuing for this cache entry. */
	122	if (ce->e_queued)
	123	wake_up_all(&mb_cache_queue);
	124	if (ce->e_used >= MB_CACHE_WRITER)
	125	ce->e_used -= MB_CACHE_WRITER;
	126	ce->e_used--;
	127	if (!(ce->e_used \|\| ce->e_queued)) {
	128	if (!__mb_cache_entry_is_hashed(ce))
	129	goto forget;
	130	mb_assert(list_empty(&ce->e_lru_list));
	131	list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
	132	}
	133	spin_unlock(&mb_cache_spinlock);
	134	return;
	135	forget:
	136	spin_unlock(&mb_cache_spinlock);
	137	__mb_cache_entry_forget(ce, GFP_KERNEL);
	138	}
	139
	140
	141	/*
1ab6c499	142	* mb_cache_shrink_scan() memory pressure callback
1da177e4 LT	143	*
	144	* This function is called by the kernel memory management when memory
	145	* gets low.
	146	*
7f8275d0	147	* @shrink: (ignored)
1495f230	148	* @sc: shrink_control passed from reclaim
1da177e4	149	*
1ab6c499	150	* Returns the number of objects freed.
1da177e4	151	*/
1ab6c499 DC	152	static unsigned long
1ab6c499 DC	153	mb_cache_shrink_scan(struct shrinker shrink, struct shrink_control sc)
1da177e4 LT	154	{
1da177e4 LT	155	LIST_HEAD(free_list);
e566d48c	156	struct mb_cache_entry entry, tmp;
1495f230 YH	157	int nr_to_scan = sc->nr_to_scan;
1495f230 YH	158	gfp_t gfp_mask = sc->gfp_mask;
1ab6c499	159	unsigned long freed = 0;
1da177e4	160
1da177e4	161	mb_debug("trying to free %d entries", nr_to_scan);
e566d48c	162	spin_lock(&mb_cache_spinlock);
1da177e4 LT	163	while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) {
	164	struct mb_cache_entry *ce =
	165	list_entry(mb_cache_lru_list.next,
	166	struct mb_cache_entry, e_lru_list);
	167	list_move_tail(&ce->e_lru_list, &free_list);
	168	__mb_cache_entry_unhash(ce);
1ab6c499 DC	169	freed++;
	170	}
	171	spin_unlock(&mb_cache_spinlock);
	172	list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) {
	173	__mb_cache_entry_forget(entry, gfp_mask);
1da177e4	174	}
1ab6c499 DC	175	return freed;
	176	}
	177
	178	static unsigned long
	179	mb_cache_shrink_count(struct shrinker shrink, struct shrink_control sc)
	180	{
	181	struct mb_cache *cache;
	182	unsigned long count = 0;
	183
	184	spin_lock(&mb_cache_spinlock);
e566d48c AG	185	list_for_each_entry(cache, &mb_cache_list, c_cache_list) {
	186	mb_debug("cache %s (%d)", cache->c_name,
	187	atomic_read(&cache->c_entry_count));
	188	count += atomic_read(&cache->c_entry_count);
	189	}
1da177e4	190	spin_unlock(&mb_cache_spinlock);
1ab6c499	191
55f841ce	192	return vfs_pressure_ratio(count);
1da177e4 LT	193	}
1da177e4 LT	194
1ab6c499 DC	195	static struct shrinker mb_cache_shrinker = {
	196	.count_objects = mb_cache_shrink_count,
	197	.scan_objects = mb_cache_shrink_scan,
	198	.seeks = DEFAULT_SEEKS,
	199	};
1da177e4 LT	200
	201	/*
	202	* mb_cache_create() create a new cache
	203	*
	204	* All entries in one cache are equal size. Cache entries may be from
	205	* multiple devices. If this is the first mbcache created, registers
	206	* the cache with kernel memory management. Returns NULL if no more
	207	* memory was available.
	208	*
	209	* @name: name of the cache (informal)
1da177e4 LT	210	* @bucket_bits: log2(number of hash buckets)
	211	*/
	212	struct mb_cache *
2aec7c52	213	mb_cache_create(const char *name, int bucket_bits)
1da177e4	214	{
2aec7c52	215	int n, bucket_count = 1 << bucket_bits;
1da177e4 LT	216	struct mb_cache *cache = NULL;
1da177e4 LT	217
2aec7c52	218	cache = kmalloc(sizeof(struct mb_cache), GFP_KERNEL);
1da177e4	219	if (!cache)
2aec7c52	220	return NULL;
1da177e4	221	cache->c_name = name;
1da177e4 LT	222	atomic_set(&cache->c_entry_count, 0);
1da177e4 LT	223	cache->c_bucket_bits = bucket_bits;
1da177e4 LT	224	cache->c_block_hash = kmalloc(bucket_count * sizeof(struct list_head),
	225	GFP_KERNEL);
	226	if (!cache->c_block_hash)
	227	goto fail;
	228	for (n=0; n<bucket_count; n++)
	229	INIT_LIST_HEAD(&cache->c_block_hash[n]);
2aec7c52 AG	230	cache->c_index_hash = kmalloc(bucket_count * sizeof(struct list_head),
	231	GFP_KERNEL);
	232	if (!cache->c_index_hash)
	233	goto fail;
	234	for (n=0; n<bucket_count; n++)
	235	INIT_LIST_HEAD(&cache->c_index_hash[n]);
	236	cache->c_entry_cache = kmem_cache_create(name,
	237	sizeof(struct mb_cache_entry), 0,
20c2df83	238	SLAB_RECLAIM_ACCOUNT\|SLAB_MEM_SPREAD, NULL);
1da177e4	239	if (!cache->c_entry_cache)
2aec7c52	240	goto fail2;
1da177e4	241
3a48ee8a AG	242	/*
	243	* Set an upper limit on the number of cache entries so that the hash
	244	* chains won't grow too long.
	245	*/
	246	cache->c_max_entries = bucket_count << 4;
	247
1da177e4 LT	248	spin_lock(&mb_cache_spinlock);
	249	list_add(&cache->c_cache_list, &mb_cache_list);
	250	spin_unlock(&mb_cache_spinlock);
	251	return cache;
	252
2aec7c52 AG	253	fail2:
	254	kfree(cache->c_index_hash);
	255
1da177e4	256	fail:
2aec7c52 AG	257	kfree(cache->c_block_hash);
2aec7c52 AG	258	kfree(cache);
1da177e4 LT	259	return NULL;
	260	}
	261
	262
	263	/*
	264	* mb_cache_shrink()
	265	*
7f927fcc	266	* Removes all cache entries of a device from the cache. All cache entries
1da177e4 LT	267	* currently in use cannot be freed, and thus remain in the cache. All others
	268	* are freed.
	269	*
1da177e4 LT	270	* @bdev: which device's cache entries to shrink
	271	*/
	272	void
8c52ab42	273	mb_cache_shrink(struct block_device *bdev)
1da177e4 LT	274	{
	275	LIST_HEAD(free_list);
	276	struct list_head l, ltmp;
	277
	278	spin_lock(&mb_cache_spinlock);
	279	list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
	280	struct mb_cache_entry *ce =
	281	list_entry(l, struct mb_cache_entry, e_lru_list);
	282	if (ce->e_bdev == bdev) {
	283	list_move_tail(&ce->e_lru_list, &free_list);
	284	__mb_cache_entry_unhash(ce);
	285	}
	286	}
	287	spin_unlock(&mb_cache_spinlock);
	288	list_for_each_safe(l, ltmp, &free_list) {
	289	__mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
	290	e_lru_list), GFP_KERNEL);
	291	}
	292	}
	293
	294
	295	/*
	296	* mb_cache_destroy()
	297	*
	298	* Shrinks the cache to its minimum possible size (hopefully 0 entries),
	299	* and then destroys it. If this was the last mbcache, un-registers the
	300	* mbcache from kernel memory management.
	301	*/
	302	void
	303	mb_cache_destroy(struct mb_cache *cache)
	304	{
	305	LIST_HEAD(free_list);
	306	struct list_head l, ltmp;
1da177e4 LT	307
	308	spin_lock(&mb_cache_spinlock);
	309	list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
	310	struct mb_cache_entry *ce =
	311	list_entry(l, struct mb_cache_entry, e_lru_list);
	312	if (ce->e_cache == cache) {
	313	list_move_tail(&ce->e_lru_list, &free_list);
	314	__mb_cache_entry_unhash(ce);
	315	}
	316	}
	317	list_del(&cache->c_cache_list);
	318	spin_unlock(&mb_cache_spinlock);
	319
	320	list_for_each_safe(l, ltmp, &free_list) {
	321	__mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
	322	e_lru_list), GFP_KERNEL);
	323	}
	324
	325	if (atomic_read(&cache->c_entry_count) > 0) {
	326	mb_error("cache %s: %d orphaned entries",
	327	cache->c_name,
	328	atomic_read(&cache->c_entry_count));
	329	}
	330
	331	kmem_cache_destroy(cache->c_entry_cache);
	332
2aec7c52	333	kfree(cache->c_index_hash);
1da177e4 LT	334	kfree(cache->c_block_hash);
	335	kfree(cache);
	336	}
	337
1da177e4 LT	338	/*
	339	* mb_cache_entry_alloc()
	340	*
	341	* Allocates a new cache entry. The new entry will not be valid initially,
	342	* and thus cannot be looked up yet. It should be filled with data, and
	343	* then inserted into the cache using mb_cache_entry_insert(). Returns NULL
	344	* if no more memory was available.
	345	*/
	346	struct mb_cache_entry *
335e92e8	347	mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
1da177e4	348	{
3a48ee8a AG	349	struct mb_cache_entry *ce = NULL;
	350
	351	if (atomic_read(&cache->c_entry_count) >= cache->c_max_entries) {
	352	spin_lock(&mb_cache_spinlock);
	353	if (!list_empty(&mb_cache_lru_list)) {
	354	ce = list_entry(mb_cache_lru_list.next,
	355	struct mb_cache_entry, e_lru_list);
	356	list_del_init(&ce->e_lru_list);
	357	__mb_cache_entry_unhash(ce);
	358	}
	359	spin_unlock(&mb_cache_spinlock);
	360	}
	361	if (!ce) {
	362	ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);
	363	if (!ce)
	364	return NULL;
f9e83489	365	atomic_inc(&cache->c_entry_count);
1da177e4 LT	366	INIT_LIST_HEAD(&ce->e_lru_list);
	367	INIT_LIST_HEAD(&ce->e_block_list);
	368	ce->e_cache = cache;
1da177e4 LT	369	ce->e_queued = 0;
1da177e4 LT	370	}
3a48ee8a	371	ce->e_used = 1 + MB_CACHE_WRITER;
1da177e4 LT	372	return ce;
	373	}
	374
	375
	376	/*
	377	* mb_cache_entry_insert()
	378	*
	379	* Inserts an entry that was allocated using mb_cache_entry_alloc() into
	380	* the cache. After this, the cache entry can be looked up, but is not yet
	381	* in the lru list as the caller still holds a handle to it. Returns 0 on
	382	* success, or -EBUSY if a cache entry for that device + inode exists
	383	* already (this may happen after a failed lookup, but when another process
	384	* has inserted the same cache entry in the meantime).
	385	*
	386	* @bdev: device the cache entry belongs to
	387	* @block: block number
2aec7c52	388	* @key: lookup key
1da177e4 LT	389	*/
	390	int
	391	mb_cache_entry_insert(struct mb_cache_entry ce, struct block_device bdev,
2aec7c52	392	sector_t block, unsigned int key)
1da177e4 LT	393	{
	394	struct mb_cache *cache = ce->e_cache;
	395	unsigned int bucket;
	396	struct list_head *l;
2aec7c52	397	int error = -EBUSY;
1da177e4 LT	398
	399	bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
	400	cache->c_bucket_bits);
	401	spin_lock(&mb_cache_spinlock);
	402	list_for_each_prev(l, &cache->c_block_hash[bucket]) {
	403	struct mb_cache_entry *ce =
	404	list_entry(l, struct mb_cache_entry, e_block_list);
	405	if (ce->e_bdev == bdev && ce->e_block == block)
	406	goto out;
	407	}
	408	__mb_cache_entry_unhash(ce);
	409	ce->e_bdev = bdev;
	410	ce->e_block = block;
	411	list_add(&ce->e_block_list, &cache->c_block_hash[bucket]);
2aec7c52 AG	412	ce->e_index.o_key = key;
	413	bucket = hash_long(key, cache->c_bucket_bits);
	414	list_add(&ce->e_index.o_list, &cache->c_index_hash[bucket]);
1da177e4 LT	415	error = 0;
	416	out:
	417	spin_unlock(&mb_cache_spinlock);
	418	return error;
	419	}
	420
	421
	422	/*
	423	* mb_cache_entry_release()
	424	*
	425	* Release a handle to a cache entry. When the last handle to a cache entry
	426	* is released it is either freed (if it is invalid) or otherwise inserted
	427	* in to the lru list.
	428	*/
	429	void
	430	mb_cache_entry_release(struct mb_cache_entry *ce)
	431	{
	432	spin_lock(&mb_cache_spinlock);
	433	__mb_cache_entry_release_unlock(ce);
	434	}
	435
	436
	437	/*
	438	* mb_cache_entry_free()
	439	*
	440	* This is equivalent to the sequence mb_cache_entry_takeout() --
	441	* mb_cache_entry_release().
	442	*/
	443	void
	444	mb_cache_entry_free(struct mb_cache_entry *ce)
	445	{
	446	spin_lock(&mb_cache_spinlock);
	447	mb_assert(list_empty(&ce->e_lru_list));
	448	__mb_cache_entry_unhash(ce);
	449	__mb_cache_entry_release_unlock(ce);
	450	}
	451
	452
	453	/*
	454	* mb_cache_entry_get()
	455	*
	456	* Get a cache entry by device / block number. (There can only be one entry
	457	* in the cache per device and block.) Returns NULL if no such cache entry
	458	* exists. The returned cache entry is locked for exclusive access ("single
	459	* writer").
	460	*/
	461	struct mb_cache_entry *
	462	mb_cache_entry_get(struct mb_cache cache, struct block_device bdev,
	463	sector_t block)
	464	{
	465	unsigned int bucket;
	466	struct list_head *l;
	467	struct mb_cache_entry *ce;
	468
	469	bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
	470	cache->c_bucket_bits);
	471	spin_lock(&mb_cache_spinlock);
	472	list_for_each(l, &cache->c_block_hash[bucket]) {
	473	ce = list_entry(l, struct mb_cache_entry, e_block_list);
	474	if (ce->e_bdev == bdev && ce->e_block == block) {
	475	DEFINE_WAIT(wait);
	476
	477	if (!list_empty(&ce->e_lru_list))
	478	list_del_init(&ce->e_lru_list);
479
480	while (ce->e_used > 0) {
481	ce->e_queued++;
482	prepare_to_wait(&mb_cache_queue, &wait,
483	TASK_UNINTERRUPTIBLE);
484	spin_unlock(&mb_cache_spinlock);
485	schedule();
486	spin_lock(&mb_cache_spinlock);
487	ce->e_queued--;
488	}
489	finish_wait(&mb_cache_queue, &wait);
490	ce->e_used += 1 + MB_CACHE_WRITER;
491
492	if (!__mb_cache_entry_is_hashed(ce)) {
493	__mb_cache_entry_release_unlock(ce);
494	return NULL;
495	}
496	goto cleanup;
497	}
498	}
499	ce = NULL;
500
501	cleanup:
502	spin_unlock(&mb_cache_spinlock);
503	return ce;
504	}
505
506	#if !defined(MB_CACHE_INDEXES_COUNT) \|\| (MB_CACHE_INDEXES_COUNT > 0)
507
508	static struct mb_cache_entry *
509	__mb_cache_entry_find(struct list_head l, struct list_head head,
2aec7c52	510	struct block_device *bdev, unsigned int key)
1da177e4 LT	511	{
	512	while (l != head) {
	513	struct mb_cache_entry *ce =
2aec7c52 AG	514	list_entry(l, struct mb_cache_entry, e_index.o_list);
2aec7c52 AG	515	if (ce->e_bdev == bdev && ce->e_index.o_key == key) {
1da177e4 LT	516	DEFINE_WAIT(wait);
	517
	518	if (!list_empty(&ce->e_lru_list))
	519	list_del_init(&ce->e_lru_list);
	520
	521	/* Incrementing before holding the lock gives readers
	522	priority over writers. */
	523	ce->e_used++;
	524	while (ce->e_used >= MB_CACHE_WRITER) {
	525	ce->e_queued++;
	526	prepare_to_wait(&mb_cache_queue, &wait,
	527	TASK_UNINTERRUPTIBLE);
	528	spin_unlock(&mb_cache_spinlock);
	529	schedule();
	530	spin_lock(&mb_cache_spinlock);
	531	ce->e_queued--;
	532	}
	533	finish_wait(&mb_cache_queue, &wait);
	534
	535	if (!__mb_cache_entry_is_hashed(ce)) {
	536	__mb_cache_entry_release_unlock(ce);
	537	spin_lock(&mb_cache_spinlock);
	538	return ERR_PTR(-EAGAIN);
	539	}
	540	return ce;
	541	}
	542	l = l->next;
	543	}
	544	return NULL;
	545	}
	546
	547
	548	/*
	549	* mb_cache_entry_find_first()
	550	*
	551	* Find the first cache entry on a given device with a certain key in
25985edc	552	* an additional index. Additional matches can be found with
1da177e4 LT	553	* mb_cache_entry_find_next(). Returns NULL if no match was found. The
	554	* returned cache entry is locked for shared access ("multiple readers").
	555	*
	556	* @cache: the cache to search
1da177e4 LT	557	* @bdev: the device the cache entry should belong to
	558	* @key: the key in the index
	559	*/
	560	struct mb_cache_entry *
2aec7c52 AG	561	mb_cache_entry_find_first(struct mb_cache cache, struct block_device bdev,
2aec7c52 AG	562	unsigned int key)
1da177e4 LT	563	{
	564	unsigned int bucket = hash_long(key, cache->c_bucket_bits);
	565	struct list_head *l;
	566	struct mb_cache_entry *ce;
	567
1da177e4	568	spin_lock(&mb_cache_spinlock);
2aec7c52 AG	569	l = cache->c_index_hash[bucket].next;
2aec7c52 AG	570	ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key);
1da177e4 LT	571	spin_unlock(&mb_cache_spinlock);
	572	return ce;
	573	}
	574
	575
	576	/*
	577	* mb_cache_entry_find_next()
	578	*
	579	* Find the next cache entry on a given device with a certain key in an
	580	* additional index. Returns NULL if no match could be found. The previous
	581	* entry is atomatically released, so that mb_cache_entry_find_next() can
	582	* be called like this:
	583	*
	584	* entry = mb_cache_entry_find_first();
	585	* while (entry) {
	586	* ...
	587	* entry = mb_cache_entry_find_next(entry, ...);
	588	* }
	589	*
	590	* @prev: The previous match
1da177e4 LT	591	* @bdev: the device the cache entry should belong to
	592	* @key: the key in the index
	593	*/
	594	struct mb_cache_entry *
2aec7c52	595	mb_cache_entry_find_next(struct mb_cache_entry *prev,
1da177e4 LT	596	struct block_device *bdev, unsigned int key)
	597	{
	598	struct mb_cache *cache = prev->e_cache;
	599	unsigned int bucket = hash_long(key, cache->c_bucket_bits);
	600	struct list_head *l;
	601	struct mb_cache_entry *ce;
	602
1da177e4	603	spin_lock(&mb_cache_spinlock);
2aec7c52 AG	604	l = prev->e_index.o_list.next;
2aec7c52 AG	605	ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key);
1da177e4 LT	606	__mb_cache_entry_release_unlock(prev);
	607	return ce;
	608	}
	609
	610	#endif /* !defined(MB_CACHE_INDEXES_COUNT) \|\| (MB_CACHE_INDEXES_COUNT > 0) */
	611
	612	static int __init init_mbcache(void)
	613	{
8e1f936b	614	register_shrinker(&mb_cache_shrinker);
1da177e4 LT	615	return 0;
	616	}
	617
	618	static void __exit exit_mbcache(void)
	619	{
8e1f936b	620	unregister_shrinker(&mb_cache_shrinker);
1da177e4 LT	621	}
	622
	623	module_init(init_mbcache)
	624	module_exit(exit_mbcache)
	625