fs/mbcache.c: change block and index hash chain to hlist_bl_node

This patch changes each mb_cache's both block and index hash chains to
use a hlist_bl_node, which contains a built-in lock.  This is the
first step in decoupling of locks serializing accesses to mb_cache
global data and each mb_cache_entry local data.
Signed-off-by: NT. Makphaibulchoke <tmac@hp.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/mbcache.c

@@ -34,9 +34,9 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
-#include <linux/init.h>
+#include <linux/list_bl.h>
 #include <linux/mbcache.h>
-
+#include <linux/init.h>
 
 #ifdef MB_CACHE_DEBUG
 # define mb_debug(f...) do { \
@@ -87,21 +87,38 @@ 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)
+__mb_cache_entry_is_block_hashed(struct mb_cache_entry *ce)
 {
-	return !list_empty(&ce->e_block_list);
+	return !hlist_bl_unhashed(&ce->e_block_list);
 }
 
 
-static void
-__mb_cache_entry_unhash(struct mb_cache_entry *ce)
+static inline void
+__mb_cache_entry_unhash_block(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);
-	}
+	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);
+}
+
+static inline void
+__mb_cache_entry_unhash(struct mb_cache_entry *ce)
+{
+	__mb_cache_entry_unhash_index(ce);
+	__mb_cache_entry_unhash_block(ce);
+}
 
 static void
 __mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask)
@@ -125,7 +142,7 @@ __mb_cache_entry_release_unlock(struct mb_cache_entry *ce)
 		ce->e_used -= MB_CACHE_WRITER;
 	ce->e_used--;
 	if (!(ce->e_used || ce->e_queued)) {
-		if (!__mb_cache_entry_is_hashed(ce))
+		if (!__mb_cache_entry_is_block_hashed(ce))
 			goto forget;
 		mb_assert(list_empty(&ce->e_lru_list));
 		list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
@@ -221,18 +238,18 @@ mb_cache_create(const char *name, int bucket_bits)
 	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);
+	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_LIST_HEAD(&cache->c_block_hash[n]);
-	cache->c_index_hash = kmalloc(bucket_count * sizeof(struct list_head),
-				      GFP_KERNEL);
+		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_LIST_HEAD(&cache->c_index_hash[n]);
+		INIT_HLIST_BL_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);
@@ -364,10 +381,13 @@ mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
 			return NULL;
 		atomic_inc(&cache->c_entry_count);
 		INIT_LIST_HEAD(&ce->e_lru_list);
-		INIT_LIST_HEAD(&ce->e_block_list);
+		INIT_HLIST_BL_NODE(&ce->e_block_list);
+		INIT_HLIST_BL_NODE(&ce->e_index.o_list);
 		ce->e_cache = cache;
 		ce->e_queued = 0;
 	}
+	ce->e_block_hash_p = &cache->c_block_hash[0];
+	ce->e_index_hash_p = &cache->c_index_hash[0];
 	ce->e_used = 1 + MB_CACHE_WRITER;
 	return ce;
 }
@@ -393,25 +413,32 @@ mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,
 {
 	struct mb_cache *cache = ce->e_cache;
 	unsigned int bucket;
-	struct list_head *l;
+	struct hlist_bl_node *l;
 	int error = -EBUSY;
+	struct hlist_bl_head *block_hash_p;
+	struct hlist_bl_head *index_hash_p;
+	struct mb_cache_entry *lce;
 
+	mb_assert(ce);
 	bucket = hash_long((unsigned long)bdev + (block & 0xffffffff), 
 			   cache->c_bucket_bits);
+	block_hash_p = &cache->c_block_hash[bucket];
 	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)
+	hlist_bl_for_each_entry(lce, l, block_hash_p, e_block_list) {
+		if (lce->e_bdev == bdev && lce->e_block == block)
 			goto out;
 	}
+	mb_assert(!__mb_cache_entry_is_block_hashed(ce));
 	__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_block_hash_p = block_hash_p;
 	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]);
+	index_hash_p = &cache->c_index_hash[bucket];
+	ce->e_index_hash_p = index_hash_p;
+	hlist_bl_add_head(&ce->e_index.o_list, index_hash_p);
+	hlist_bl_add_head(&ce->e_block_list, block_hash_p);
 	error = 0;
 out:
 	spin_unlock(&mb_cache_spinlock);
@@ -463,14 +490,16 @@ mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
 		   sector_t block)
 {
 	unsigned int bucket;
-	struct list_head *l;
+	struct hlist_bl_node *l;
 	struct mb_cache_entry *ce;
+	struct hlist_bl_head *block_hash_p;
 
 	bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
 			   cache->c_bucket_bits);
+	block_hash_p = &cache->c_block_hash[bucket];
 	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);
+	hlist_bl_for_each_entry(ce, l, block_hash_p, e_block_list) {
+		mb_assert(ce->e_block_hash_p == block_hash_p);
 		if (ce->e_bdev == bdev && ce->e_block == block) {
 			DEFINE_WAIT(wait);
 
@@ -489,7 +518,7 @@ mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
 			finish_wait(&mb_cache_queue, &wait);
 			ce->e_used += 1 + MB_CACHE_WRITER;
 
-			if (!__mb_cache_entry_is_hashed(ce)) {
+			if (!__mb_cache_entry_is_block_hashed(ce)) {
 				__mb_cache_entry_release_unlock(ce);
 				return NULL;
 			}
@@ -506,12 +535,14 @@ mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
 #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,
+__mb_cache_entry_find(struct hlist_bl_node *l, struct hlist_bl_head *head,
 		      struct block_device *bdev, unsigned int key)
 {
-	while (l != head) {
+	while (l != NULL) {
 		struct mb_cache_entry *ce =
-			list_entry(l, struct mb_cache_entry, e_index.o_list);
+			hlist_bl_entry(l, struct mb_cache_entry,
+				e_index.o_list);
+		mb_assert(ce->e_index_hash_p == head);
 		if (ce->e_bdev == bdev && ce->e_index.o_key == key) {
 			DEFINE_WAIT(wait);
 
@@ -532,7 +563,7 @@ __mb_cache_entry_find(struct list_head *l, struct list_head *head,
 			}
 			finish_wait(&mb_cache_queue, &wait);
 
-			if (!__mb_cache_entry_is_hashed(ce)) {
+			if (!__mb_cache_entry_is_block_hashed(ce)) {
 				__mb_cache_entry_release_unlock(ce);
 				spin_lock(&mb_cache_spinlock);
 				return ERR_PTR(-EAGAIN);
@@ -562,12 +593,16 @@ 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;
+	struct hlist_bl_node *l;
+	struct mb_cache_entry *ce = NULL;
+	struct hlist_bl_head *index_hash_p;
 
+	index_hash_p = &cache->c_index_hash[bucket];
 	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);
+	if (!hlist_bl_empty(index_hash_p)) {
+		l = hlist_bl_first(index_hash_p);
+		ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
+	}
 	spin_unlock(&mb_cache_spinlock);
 	return ce;
 }
@@ -597,12 +632,16 @@ mb_cache_entry_find_next(struct mb_cache_entry *prev,
 {
 	struct mb_cache *cache = prev->e_cache;
 	unsigned int bucket = hash_long(key, cache->c_bucket_bits);
-	struct list_head *l;
+	struct hlist_bl_node *l;
 	struct mb_cache_entry *ce;
+	struct hlist_bl_head *index_hash_p;
 
+	index_hash_p = &cache->c_index_hash[bucket];
+	mb_assert(prev->e_index_hash_p == index_hash_p);
 	spin_lock(&mb_cache_spinlock);
+	mb_assert(!hlist_bl_empty(index_hash_p));
 	l = prev->e_index.o_list.next;
-	ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key);
+	ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
 	__mb_cache_entry_release_unlock(prev);
 	return ce;
 }

include/linux/mbcache.h

@@ -3,19 +3,21 @@
 
   (C) 2001 by Andreas Gruenbacher, <a.gruenbacher@computer.org>
 */
-
 struct mb_cache_entry {
 	struct list_head		e_lru_list;
 	struct mb_cache			*e_cache;
 	unsigned short			e_used;
 	unsigned short			e_queued;
+	atomic_t			e_refcnt;
 	struct block_device		*e_bdev;
 	sector_t			e_block;
-	struct list_head		e_block_list;
+	struct hlist_bl_node		e_block_list;
 	struct {
-		struct list_head	o_list;
+		struct hlist_bl_node	o_list;
 		unsigned int		o_key;
 	} e_index;
+	struct hlist_bl_head		*e_block_hash_p;
+	struct hlist_bl_head		*e_index_hash_p;
 };
 
 struct mb_cache {
@@ -25,8 +27,8 @@ struct mb_cache {
 	int				c_max_entries;
 	int				c_bucket_bits;
 	struct kmem_cache		*c_entry_cache;
-	struct list_head		*c_block_hash;
-	struct list_head		*c_index_hash;
+	struct hlist_bl_head		*c_block_hash;
+	struct hlist_bl_head		*c_index_hash;
 };
 
 /* Functions on caches */