[PATCH] ext2/3 updates for 2.5.44 (4/11): mbcache infrastructure for xattrs

# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/10/20	[e-mail]	1.813
# Port of the 0.8.50 xattr-mbcache patch to 2.5.  (Shrinker API, hch cleanups)
# (now uses struct block_device * to index devices, and uses hash.h for hash function)
# 
# This patch creates a meta block cache which is utilized by the ext3 and
# ext2 extended attribute patch (patches 2 and 3, respectively).  This
# cache allows directory blocks to be indexed by multiple keys.  In the
# case of the extended attribute patches, it is used to look up blocks by
# both the block number and by the hash of the extended attributes.  This
# is extremely important to allow the sharing of acl's when stored as
# extended attributes.  Otherwise every single file would require its own,
# separate, one block overhead to store then ACL, even though there might
# be a large number of files that have the same ACL.
# --------------------------------------------
#
# fs/Config.in            |   11 
# fs/Makefile             |    4 
# fs/mbcache.c            |  702 ++++++++++++++++++++++++++++++++++++++++++++++++
# include/linux/mbcache.h |   72 ++++
# 4 files changed, 788 insertions(+), 1 deletion(-)
#
diff -Nru a/fs/Config.in b/fs/Config.in
--- a/fs/Config.in	Sun Oct 20 04:40:53 2002
+++ b/fs/Config.in	Sun Oct 20 04:40:53 2002
@@ -182,6 +182,17 @@
    define_tristate CONFIG_ZISOFS_FS n
 fi
 
+# Meta block cache for Extended Attributes (ext2/ext3)
+if [ "$CONFIG_EXT2_FS_XATTR" = "y" -o "$CONFIG_EXT3_FS_XATTR" = "y" ]; then
+   if [ "$CONFIG_EXT2_FS" = "y" -o "$CONFIG_EXT3_FS" = "y" ]; then
+      define_tristate CONFIG_FS_MBCACHE y
+   else
+      if [ "$CONFIG_EXT2_FS" = "m" -o "$CONFIG_EXT3_FS" = "m" ]; then
+         define_tristate CONFIG_FS_MBCACHE m
+      fi
+   fi
+fi
+
 mainmenu_option next_comment
 comment 'Partition Types'
 source fs/partitions/Config.in
diff -Nru a/fs/Makefile b/fs/Makefile
--- a/fs/Makefile	Sun Oct 20 04:40:53 2002
+++ b/fs/Makefile	Sun Oct 20 04:40:53 2002
@@ -6,7 +6,7 @@
 # 
 
 export-objs :=	open.o dcache.o buffer.o bio.o inode.o dquot.o mpage.o aio.o \
-                fcntl.o read_write.o dcookies.o
+                fcntl.o read_write.o dcookies.o mbcache.o
 
 obj-y :=	open.o read_write.o devices.o file_table.o buffer.o \
 		bio.o super.o block_dev.o char_dev.o stat.o exec.o pipe.o \
@@ -29,6 +29,8 @@
 obj-y				+= binfmt_script.o
 
 obj-$(CONFIG_BINFMT_ELF)	+= binfmt_elf.o
+
+obj-$(CONFIG_FS_MBCACHE)	+= mbcache.o
 
 obj-$(CONFIG_QUOTA)		+= dquot.o
 obj-$(CONFIG_QFMT_V1)		+= quota_v1.o
diff -Nru a/fs/mbcache.c b/fs/mbcache.c
--- /dev/null	Wed Dec 31 16:00:00 1969
+++ b/fs/mbcache.c	Sun Oct 20 04:40:53 2002
@@ -0,0 +1,702 @@
+/*
+ * linux/fs/mbcache.c
+ * (C) 2001-2002 Andreas Gruenbacher, <[e-mail]>
+ */
+
+/*
+ * 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.
+ */
+
+#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)
+		
+MODULE_AUTHOR("Andreas Gruenbacher <[e-mail]>");
+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_takeout);
+EXPORT_SYMBOL(mb_cache_entry_free);
+EXPORT_SYMBOL(mb_cache_entry_dup);
+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 spinlock_t mb_cache_spinlock = SPIN_LOCK_UNLOCKED;
+static struct shrinker *mb_shrinker;
+
+static inline int
+mb_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, unsigned int gfp_mask);
+
+static inline void
+__mb_cache_entry_takeout_lru(struct mb_cache_entry *ce)
+{
+	if (!list_empty(&ce->e_lru_list))
+		list_del_init(&ce->e_lru_list);
+}
+
+
+static inline void
+__mb_cache_entry_into_lru(struct mb_cache_entry *ce)
+{
+	list_add(&ce->e_lru_list, &mb_cache_lru_list);
+}
+
+
+static inline int
+__mb_cache_entry_in_lru(struct mb_cache_entry *ce)
+{
+	return (!list_empty(&ce->e_lru_list));
+}
+
+
+/*
+ * Insert the cache entry into all hashes.
+ */
+static inline void
+__mb_cache_entry_link(struct mb_cache_entry *ce)
+{
+	struct mb_cache *cache = ce->e_cache;
+	unsigned int bucket;
+	int n;
+	
+	bucket = hash_long((unsigned long)ce->e_bdev +
+			   (ce->e_block & 0xffffff), cache->c_bucket_bits);
+	list_add(&ce->e_block_list, &cache->c_block_hash[bucket]);
+	for (n=0; n<mb_cache_indexes(cache); n++) {
+		bucket = hash_long(ce->e_indexes[n].o_key,
+				   cache->c_bucket_bits);
+		list_add(&ce->e_indexes[n].o_list,
+		         &cache->c_indexes_hash[n][bucket]);
+	}
+}
+
+
+/*
+ * Remove the cache entry from all hashes.
+ */
+static inline void
+__mb_cache_entry_unlink(struct mb_cache_entry *ce)
+{
+	int n;
+
+	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 inline int
+__mb_cache_entry_is_linked(struct mb_cache_entry *ce)
+{
+	return (!list_empty(&ce->e_block_list));
+}
+
+
+static inline struct mb_cache_entry *
+__mb_cache_entry_read(struct mb_cache_entry *ce)
+{
+	__mb_cache_entry_takeout_lru(ce);
+	atomic_inc(&ce->e_used);
+	return ce;
+}
+
+
+static inline void
+__mb_cache_entry_forget(struct mb_cache_entry *ce)
+{
+	struct mb_cache *cache = ce->e_cache;
+
+	mb_assert(atomic_read(&ce->e_used) == 0);
+	atomic_dec(&cache->c_entry_count);
+	if (cache->c_op.free)
+		cache->c_op.free(ce);
+	kmem_cache_free(cache->c_entry_cache, ce);
+}
+
+
+static inline void
+__mb_cache_entry_release_unlock(struct mb_cache_entry *ce)
+{
+	if (atomic_dec_and_test(&ce->e_used)) {
+		if (!__mb_cache_entry_is_linked(ce))
+			goto forget;
+		__mb_cache_entry_into_lru(ce);
+	}
+	spin_unlock(&mb_cache_spinlock);
+	return;
+forget:
+	spin_unlock(&mb_cache_spinlock);
+	__mb_cache_entry_forget(ce);
+}
+
+
+/*
+ * 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 int
+mb_cache_shrink_fn(int nr_to_scan, unsigned int gfp_mask)
+{
+	LIST_HEAD(free_list);
+	struct list_head *l;
+	int count = 0;
+
+	spin_lock(&mb_cache_spinlock);
+	list_for_each_prev(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.prev,
+				   struct mb_cache_entry, e_lru_list);
+		list_move(&ce->e_lru_list, &free_list);
+		if (__mb_cache_entry_is_linked(ce))
+			__mb_cache_entry_unlink(ce);
+		nr_to_scan--;
+	}
+	spin_unlock(&mb_cache_spinlock);
+	l = free_list.prev;
+	while (l != &free_list) {
+		struct mb_cache_entry *ce = list_entry(l,
+			struct mb_cache_entry, e_lru_list);
+		l = l->prev;
+		__mb_cache_entry_forget(ce);
+		count--;
+	}
+out:
+	mb_debug("%d remaining entries ", count);
+	return count;
+}
+
+
+/*
+ * 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_index))
+		return NULL;
+
+	cache = kmalloc(sizeof(struct mb_cache) +
+	                indexes_count * sizeof(struct list_head), GFP_KERNEL);
+	if (!cache)
+		goto fail;
+	cache->c_name = name;
+	if (cache_op)
+		cache->c_op.free = cache_op->free;
+	else
+		cache->c_op.free = NULL;
+	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,
+		0 /*SLAB_POISON | SLAB_RED_ZONE*/, NULL, NULL);
+	if (!cache->c_entry_cache)
+		goto fail;
+
+	spin_lock(&mb_cache_spinlock);
+	if (list_empty(&mb_cache_list)) {
+		if (mb_shrinker) {
+			printk(KERN_ERR "%s: already have a shrinker!\n",
+					__FUNCTION__);
+			remove_shrinker(mb_shrinker);
+		}
+		mb_shrinker = set_shrinker(DEFAULT_SEEKS, mb_cache_shrink_fn);
+	}
+	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]);
+		if (cache->c_block_hash)
+			kfree(cache->c_block_hash);
+		kfree(cache);
+	}
+	return NULL;
+}
+
+
+/*
+ * mb_cache_shrink()
+ *
+ * Removes all cache entires 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.
+ *
+ * @cache: which cache to shrink
+ * @bdev: which device's cache entries to shrink
+ */
+void
+mb_cache_shrink(struct mb_cache *cache, struct block_device *bdev)
+{
+	LIST_HEAD(free_list);
+	struct list_head *l;
+
+	spin_lock(&mb_cache_spinlock);
+	l = mb_cache_lru_list.prev;
+	while (l != &mb_cache_lru_list) {
+		struct mb_cache_entry *ce =
+			list_entry(l, struct mb_cache_entry, e_lru_list);
+		l = l->prev;
+		if (ce->e_bdev == bdev) {
+			list_move(&ce->e_lru_list, &free_list);
+			if (__mb_cache_entry_is_linked(ce))
+				__mb_cache_entry_unlink(ce);
+		}
+	}
+	spin_unlock(&mb_cache_spinlock);
+	l = free_list.prev;
+	while (l != &free_list) {
+		struct mb_cache_entry *ce =
+			list_entry(l, struct mb_cache_entry, e_lru_list);
+		l = l->prev;
+		__mb_cache_entry_forget(ce);
+	}
+}
+
+
+/*
+ * 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;
+	int n;
+
+	spin_lock(&mb_cache_spinlock);
+	l = mb_cache_lru_list.prev;
+	while (l != &mb_cache_lru_list) {
+		struct mb_cache_entry *ce =
+			list_entry(l, struct mb_cache_entry, e_lru_list);
+		l = l->prev;
+		if (ce->e_cache == cache) {
+			list_move(&ce->e_lru_list, &free_list);
+			if (__mb_cache_entry_is_linked(ce))
+				__mb_cache_entry_unlink(ce);
+		}
+	}
+	list_del(&cache->c_cache_list);
+	if (list_empty(&mb_cache_list) && mb_shrinker) {
+		remove_shrinker(mb_shrinker);
+		mb_shrinker = 0;
+	}
+	spin_unlock(&mb_cache_spinlock);
+
+	l = free_list.prev;
+	while (l != &free_list) {
+		struct mb_cache_entry *ce =
+			list_entry(l, struct mb_cache_entry, e_lru_list);
+		l = l->prev;
+		__mb_cache_entry_forget(ce);
+	}
+
+	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;
+		atomic_set(&ce->e_used, 1);
+	}
+	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).
+ */
+int
+mb_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_assert(!__mb_cache_entry_is_linked(ce));
+	ce->e_bdev = bdev;
+	ce->e_block = block;
+	for (n=0; n<mb_cache_indexes(cache); n++)
+		ce->e_indexes[n].o_key = keys[n];
+	__mb_cache_entry_link(ce);
+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_takeout()
+ *
+ * Take a cache entry out of the cache, making it invalid. The entry can later
+ * be re-inserted using mb_cache_entry_insert(), or released using
+ * mb_cache_entry_release().
+ */
+void
+mb_cache_entry_takeout(struct mb_cache_entry *ce)
+{
+	spin_lock(&mb_cache_spinlock);
+	mb_assert(!__mb_cache_entry_in_lru(ce));
+	if (__mb_cache_entry_is_linked(ce))
+		__mb_cache_entry_unlink(ce);
+	spin_unlock(&mb_cache_spinlock);
+}
+
+
+/*
+ * 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(!__mb_cache_entry_in_lru(ce));
+	if (__mb_cache_entry_is_linked(ce))
+		__mb_cache_entry_unlink(ce);
+	__mb_cache_entry_release_unlock(ce);
+}
+
+
+/*
+ * mb_cache_entry_dup()
+ *
+ * Duplicate a handle to a cache entry (does not duplicate the cache entry
+ * itself). After the call, both the old and the new handle must be released.
+ */
+struct mb_cache_entry *
+mb_cache_entry_dup(struct mb_cache_entry *ce)
+{
+	atomic_inc(&ce->e_used);
+	return 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.
+ */
+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) {
+			ce = __mb_cache_entry_read(ce);
+			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,
+		      int index, struct block_device *bdev, unsigned int key)
+{
+	while (l != head) {
+		struct mb_cache_entry *ce =
+			list_entry(l, struct mb_cache_entry,
+			           e_indexes[index].o_list);
+		if (ce->e_bdev == bdev &&
+		    ce->e_indexes[index].o_key == key) {
+			ce = __mb_cache_entry_read(ce);
+			if (ce)
+				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. Additonal matches can be found with
+ * mb_cache_entry_find_next(). Returns NULL if no match was found.
+ *
+ * @cache: the cache to search
+ * @index: the number of the additonal index to search (0<=index<indexes_count)
+ * @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, int index,
+			  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;
+
+	mb_assert(index < mb_cache_indexes(cache));
+	spin_lock(&mb_cache_spinlock);
+	l = cache->c_indexes_hash[index][bucket].next;
+	ce = __mb_cache_entry_find(l, &cache->c_indexes_hash[index][bucket],
+	                           index, 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
+ * @index: the number of the additonal index to search (0<=index<indexes_count)
+ * @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, int index,
+			 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;
+
+	mb_assert(index < mb_cache_indexes(cache));
+	spin_lock(&mb_cache_spinlock);
+	l = prev->e_indexes[index].o_list.next;
+	ce = __mb_cache_entry_find(l, &cache->c_indexes_hash[index][bucket],
+	                           index, bdev, key);
+	__mb_cache_entry_release_unlock(prev);
+	return ce;
+}
+
+#endif  /* !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) */
diff -Nru a/include/linux/mbcache.h b/include/linux/mbcache.h
--- /dev/null	Wed Dec 31 16:00:00 1969
+++ b/include/linux/mbcache.h	Sun Oct 20 04:40:53 2002
@@ -0,0 +1,72 @@
+/*
+  File: linux/mbcache.h
+
+  (C) 2001 by Andreas Gruenbacher, <[e-mail]>
+*/
+
+/* Hardwire the number of additional indexes */
+#define MB_CACHE_INDEXES_COUNT 1
+
+struct mb_cache_entry;
+
+struct mb_cache_op {
+	void (*free)(struct mb_cache_entry *);
+};
+
+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];
+};
+
+struct mb_cache_entry_index {
+	struct list_head		o_list;
+	unsigned int			o_key;
+};
+
+struct mb_cache_entry {
+	struct list_head		e_lru_list;
+	struct mb_cache			*e_cache;
+	atomic_t			e_used;
+	struct block_device		*e_bdev;
+	sector_t			e_block;
+	struct list_head		e_block_list;
+	struct mb_cache_entry_index	e_indexes[0];
+};
+
+/* Functions on caches */
+
+struct mb_cache * mb_cache_create(const char *, struct mb_cache_op *, size_t,
+				  int, int);
+void mb_cache_shrink(struct mb_cache *, struct block_device *);
+void mb_cache_destroy(struct mb_cache *);
+
+/* Functions on cache entries */
+
+struct mb_cache_entry *mb_cache_entry_alloc(struct mb_cache *);
+int mb_cache_entry_insert(struct mb_cache_entry *, struct block_device *,
+			  sector_t, unsigned int[]);
+void mb_cache_entry_rehash(struct mb_cache_entry *, unsigned int[]);
+void mb_cache_entry_release(struct mb_cache_entry *);
+void mb_cache_entry_takeout(struct mb_cache_entry *);
+void mb_cache_entry_free(struct mb_cache_entry *);
+struct mb_cache_entry *mb_cache_entry_dup(struct mb_cache_entry *);
+struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *,
+					  struct block_device *,
+					  sector_t);
+#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
+struct mb_cache_entry *mb_cache_entry_find_first(struct mb_cache *cache, int,
+						 struct block_device *, 
+						 unsigned int);
+struct mb_cache_entry *mb_cache_entry_find_next(struct mb_cache_entry *, int,
+						struct block_device *, 
+						unsigned int);
+#endif