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: T. Makphaibulchoke <tmac@hp.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 78 insertions, 39 deletions

diff --git a/fs/mbcache.c b/fs/mbcache.c
index e519e45bf673..55db0daaca74 100644
--- a/fs/mbcache.c
+++ b/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 @@ cleanup:
 #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;
 }